Texas Tech University
Center for Pulsed Power & Power Electronics

Authors: Michael Giesselmann; Jon Mayes

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10310878

Abstract: We are reporting on a capacitor charger with a rated peak voltage of 50kV. The charger is fed from a standard 208V, 3-phase AC utility outlet. The HV package, consisting of a high frequency transformer, HV rectifier and HV feedback voltage divider was provided by Stangenes Industries and is contained in a 19 inch, 5U rack mountable package. The primary of the transformer is driven by an H-bridge inverter. Inverter current control is achieved through a Digital Signal Controller (DSC) with a fast PWM controller and a programmable analog comparator. The DSC provides cycle-by-cycle peak current mode control as well as current loop stabilization through digital slope compensation. The charger is controlled by an Industrial controller with a touch screen interface. The touch screen interface involves multiple programmable and customizable screens. The controller monitors the output voltage of the load capacitor and closes the voltage loop. A back-up safety function limits the charge time should the voltage loop be broken or not work properly.

Conferences

Authors: C. A. Negri; S. Daneshvardehnavi; K. E. K. Schmitt; A. Esmaeel Nezhad; P. H. J. Nardelli; S. Bayne; M. G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9732999

Abstract: The power output of the solar panels follows a power-voltage (P-V) characteristic containing only one Global Maximum Point (GMP) in the normal conditions. However, under Partial Shading Conditions (PSC), the unbalanced irradiance in the panels creates Local Maximum Points (LMP) in the P-V curve. Standard control techniques for Maximum Power Point Tracking (MPPT) can not properly locate the GMP, stagnating in LMPs and generating losses in the energy harvesting. Specific techniques to locate the GMP are presented in the literature. However, the condition to restart the GMP is not widely discussed. The main challenges of global search algorithms are related to the restarting conditions. Avoiding unnecessary searching and providing an assertive GMP restarting condition is crucial for PV systems operation. In every GMP search, the solar inverters oscillate the power exchanged with the grid, causing frequency and voltage variations depending on the size of the PV plant. This paper proposes a novel technique that uses a centralized controller to identify the shaded inverters, creating flags that locally start the GMP searching. The solution minimizes the number of times the search is performed by providing an assertive GMP restarting condition, saving energy, and avoiding unnecessary output power oscillation. The proposed control technique was evaluated using the data of a real 150-kW solar farm containing five inverters with two MPPT trackers each.

Journal

Authors: DaneshvarDehnavi, S; Negri, C; Bayne, S; Giesselmann, M

PDF: https://www.sciencedirect.com/science/article/abs/pii/S001905782100207X?via%3Dihub

Abstract: With the advancement of technology, electric equipment and loads have become more sensitive to problems related to power quality, such as voltage sag, swell, imbalances, and harmonics. To detect faults and to protect sensitive loads from these voltage distortions, a Dynamic Voltage Restorer (DVR) series compensator is among the best available cost-effective solutions. One of the main goals of the DVR is to achieve a control structure that is robust, stable, and can handle properly the disturbances (e.g., grid voltage issues, load current, and fluctuations at the DC link voltage) and model uncertainties (e.g., inverters and filter parameters). In this work, a novel framework control strategy based on Uncertainty and Disturbance Estimator (UDE) is proposed to improve the response of the DVR to properly compensate the load voltage under a variety of power quality issues, particularly the ones associated with the grid voltage disturbances. Additionally, the stability of the proposed control system is analyzed and validated using the Lyapunov stability theory. The advantages of the new control system are robustness, simplified design, good harmonic rejection, low tracking error, fast response, and sinusoidal reference tracking without the need for voltage transformations or specific frequency tuning (e.g., abc-dq0 and Proportional-Resonant). This research uses the MATLAB/Simulink software to validate the effectiveness of the proposed scheme under a diverse set of conditions with no control limitations. Moreover, the designed controller is tested under real conditions using Hardware-In-theLoop (HIL) validation with OPAL-RT real-time simulator coupled with a TI Launchpad microcontroller. The results demonstrate a good performance of the proposed control strategy for a quick transient response and a great harmonic rejection when subject to grid voltage distortions. (c) 2021 ISA. Published by Elsevier Ltd. All rights reserved.

Journal

Authors: A. Balal; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9772041

Abstract: This paper makes use of electric vehicles (EVs) that are simultaneously connected to the Photovoltaic Cells (PV) and the power grid. In micro-grids, batteries of the electric vehicles (EVs) used as a source of power to feed the power grid in the peak demands of electricity. EVs can help regulation of the power grid by storing excess solar energy and returning it to the grid during high demand hours. This paper proposes a new architecture of micro-grids by using a rooftop solar system, Battery Electric Vehicles (BEVs), grid connected inverters, a boost converter, a bidirectional half-bridge converter, output filter, including L, LC, or LCL, and transformers. The main parts of this micro-grid are illustrated and modeled, as well as a simulation of their operation. In addition, simulation results explore the charging and discharging scenarios of the BEVs.

Conference Paper/Presentation

Authors: S. Daneshvardehnavi; C. A. Negri; K. E. K. Schmitt; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9458523

Abstract: This paper presents a control strategy for reactive power support using Plug-in Electric Vehicles (PEV) as a case study for the Global Laboratory for Energy Asset Management and Manufacturing (GLEAMM) microgrid. The control topology is divided into two levels with a dynamic limitation. This Electric Vehicle (EV) station Charger has a topology including a full-bridge AC-DC rectifier and a bidirectional half-bridge DC-DC converter. In the first level, a PQ and power control are used for the AC/DC inverter and DC/DC converters, receiving the set-points for active and reactive power from the upper level. The second level is a central controller that is used to manage the reactive power at the microgrid and to provide the necessary power setpoints for the PEV. A dynamic limitation strategy is proposed to maximize the reactive power support maintaining a reasonable amount of active power to charge the EV battery, considering the maximum limitation of the AC/DC inverter. To validate the effectiveness of the proposed control strategy, simulation results from a three-phase system are simulated in Matlab/Simulink environment.

Conference Paper/Presentation

Authors: DaneshvarDehnavi, S; Negri, CA; Giesselmann, MG; Bayne, SB; Wollenberg, B

PDF: https://reader.elsevier.com/reader/sd/pii/S0960148121008661?token=932D53120197025F7F7EC2580A2B31CCF46703E26A108CCF8761AE6090D17112871022DB7501299783854A59C3D19018&originRegion=us-east-1&originCreation=20221127205605

Abstract: Global warming has been a critical issue in recent years. Many leaders and politicians have talked about replacing fossil fuels with Renewable Energy Resources (RES). Some of them even went further and are talking about running a country with 100% RES soon. Is that economically viable? What would be the estimated cost of such a system? In this paper, a city in west Texas with a 100 MW peak load has been assumed to operate with the wind, solar, and Battery Energy Storage System (BESS) totally disconnected from the grid for a cost evaluation. Real generation and load time series data are used to achieve an optimum combination of the installed capacity of those resources by minimizing the total overnight cost, respecting a maximum of 24 h of faults in which the system cannot provide the load during the period. A Monte Carlo simulation is applied to the previous results to evaluate the influence of faulty devices and increase the robustness of the system. The results for both cases are analyzed and compared. Finally, the total cost of install capacity will be compared with other non-renewable resources. (c) 2021 Elsevier Ltd. All rights reserved.

Journal

Authors: A. Balal; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9639359

Abstract: Shortage of power generation results in unplanned load shedding. Active participation of the people on the demand side provides a solution by moving loads from peak time to off/peak hours during the day. This paper presents a Demand Side Management (DSM) that includes a rooftop photovoltaic system, a Battery Storage System (BSS), a hybrid control system, and a grid-tie inverter to reduce peak demands. The hybrid controller ensures that the maximum solar power generated is used or stored in the batteries for a given load, and any excess energy feeds the power grid. In this system, essential loads and generated power from rooftop PV systems are constantly monitored, and power generated by solar panels is preferred above grid electricity. According to the results, this system provides 100 % of each residence"™s required energy, plus an annual 6497 kWh to feed the AC grid and store in the BSS, resulting in monthly cost savings and the elimination of peak loads, particularly during the summer months, as well as a variety of environmental benefits.

Conference Paper/Presentation

Authors: V. Roy; S. S. Noureen; S. Atique; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9467414

Abstract: Some of the recent reports show that Power Grid is a target of attack and gradually the need for understanding the security of Grid network is getting a prime focus. The Department of Homeland Security has imposed focus on Cyber Threats on Power Grid in their "Cyber Security Strategy,2018" [1] . DHS has focused on innovations to manage risk attacks on Power System based national resources. Power Grid is a cyber physical system which consists of power flow and data transmission. The important part of a microgrid is the two-way power flow which makes the system complex on monitoring and control. In this paper, we have tried to study different types of attacks which change the data propagation of Synchrophasor, network communication interruption behavior and find the data propagation scenario due to attack. The focus of the paper is to develop a platform for Synchrophasor based data network attack study which is a part of Microgrid design. Different types of intrusion models were studied to observe change in Synchrophasor data pattern which will help for further prediction to improve Microgrid resiliency for different types of cyber-attack.

IEEE Conferences

Authors: Michael Giesselmann; Jon Mayes

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9733157

Abstract: We are reporting on the design of a compact capacitor charger with a rated output voltage of 50kV and a power rating of 10kJ/s. The input source is a 208V, 3-phase AC utility supply. The charger shall fit in to an 19inch, 5U enclosure. The core of the charger is a HV-power pack containing a high-frequency transformer with a nano-crystalline core, multiple output windings using litz-wire and integrated HV rectifiers. The primary of the transformer is driven by an H-bridge inverter with advanced IGBTs and matching High Power Drivers. The control is through a state-of-the-art Digital Signal Controller (DSC) with fast cycle-by-cycle Peak current mode control, leading edge blanking, and high resolution, fast, automated slope compensation for current loop stability. The DSC runs at 5 times the speed of the main processor core for ns level PWM resolution.

Conferences

Authors: S. Basu; V. Roy; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9342862

Abstract: The extensive integration of renewable sources of energy has caused the number of conventional power plants to go down. This in turn causes a reduction of the system resilience, i.e. the ability of a system to recover from a fault. Synchronous condensers, when included in the grid, contribute to the fault current and provide voltage support thereby enhancing dynamic voltage recovery. This article summarizes the capacity of a synchronous condenser, when connected to the power grid with wind or solar power plants to compensate for reactive power compensation and injection of active power at their point of common coupling. A case, based on a local distribution network, is developed on a 33kV transmission line that feeds into several inductive loads. Simulations are performed in PSIM to display the enhancement of system stability and reduction in power losses while supplying reactive power by activating synchronous condensers to the grid with given practical grid rules.

Conference Paper/Presentation

Authors: M. Giesselmann; S. Daneshvardehnavi

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9158658

Abstract: We are presenting an LT-Spice Model for 3-phase Induction Generators that are operating in off-grid mode using a 3-phase capacitor bank for self-excitation. To model the self-excitation, we include the effects of a non-linear magnetizing inductance with residual magnetic flux and saturation. Our model represents both the electrical as well as the mechanical characteristics of the machine.

IEEE Conferences

Authors: C. A. Negri; S. D. Dehnavi; M. G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9186303

Abstract: The high power and energy density of synchronous machines turn them into reliable sources of energy for pulsed power applications. In this article, two mathematical models using both actual and normalized (per-unit) parameters have been developed and simulated in LTspice, which is a powerful and a free tool to simulate electrical/electronic circuits. In this article, an efficient solver based on the flux and current equations is presented. The model has been validated against published results with both actual and per-unit parameters. It has been observed that for models with normalized parameters, the simulation time is significantly reduced. The validated model of the machine has been used to show the effects of nonlinear loads on the voltages and currents, in particular the reaction currents in the damper winding inside of the generator. In addition, the model has been used to study the effect of the RC time constant of the load on the peak power provided by a synchronous machine used to store energy for pulsed power applications.

IEEE Journals

Authors: V. Roy; S. Noureen; T. Atique; S. Bayne; M. Giesselmann; A. S. Subburaj; M. A. Harral

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9020467

Abstract: Introduction of Synchronized phasor measurement unit (PMU) in power system is a solution for monitoring system wide disturbances. PMUs provide precise information about a system's phasors such as magnitude and phase angle of sine waves of the system. PMU data is a valuable source when determining the post-mortem of a fault, or a system disturbance. It can be unveiled what time the system began to falter and exactly what instabilities the system experienced. Knowing the cause of such instabilities will allow enhancement of the current system protection system. This will help in minimizing risk, disruptions or total system collapse. PMUs are synchronized via global positioning system (GPS). For wide area monitoring (WAM), synchronization of the PMUs allows for interconnected systems to be monitored simultaneously, giving real time records. This paper explores the impact of PMU in modern power system, deployment strategies of PMU network around Texas Tech University, importance of PMU data collected from the network, correlation of events by data analysis and focus on how the time stamped information is valuable for grid stability. The ongoing smart architecture of grid will increase dependency and importance on PMU based network in future.

Conference Paper/Presentation

Authors: C. Negri; S. Daneshvardehnavi; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9009899

Abstract: We are reporting on the formulation and performance of dynamic models for Pulsed Alternators for LTspice. The models are modular and hierarchical and cover both the electrical and mechanical aspects of the electric machine including the mechanical torque, speed and inertia. The models also include the effects of the damper cage and the excitation winding to accurately represent the sub-transient and transient behavior. The models can also be used to represent synchronous generators in steady state operation. LTspice is a powerful, widely available software package that can be used to model Pulsed Power circuits. We are presenting the detailed models as well as results of the simulations.

IEEE Conferences

Authors: M. Giesselmann; V. Roy

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8662233

Abstract: This paper is showing simulations of power supplies for repetitive power modulators using LTspice. We are presenting power supplies with single-phase and three-phase AC input and the effects of the rectifier stages on AC input current waveforms in both cases. We are also presenting the resulting power factor including circuits for electronic power factor correction. LTspice models for electronic power factor correction using cycle-by-cycle switching as well as time-averaged models are presented. The time-averaged models replace the PWM (pulse width modulation) switch with a transformer model with variable duty cycle. They are valid for a range of DC-DC converters. We are extending the time-averaged model for operation in continuous (CCM) and discontinuous (DCM) conduction mode and presenting results that show the fidelity of these models by comparison to cycle-by-cycle results. We are providing the detailed mathematical derivation for the DCM model expansion in the appendix. Time-averaged models do not have to keep track of thousands of steep switching transitions and can run orders of magnitude faster than cycle-by-cycle switch-mode models. Results using the time-averaged model are presented for a power supply with primary (wave-shaping) and cascaded secondary feedback control that regulates the output voltage of the converter.

IEEE Journals

Authors: V. Roy; S. S. Noureen; S. Bayne; A. Bilbao; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8416176

Abstract: In this present study a hybrid renewable energy system is proposed to optimize the load demand for Center Pivot Irrigation System for remote cultivation areas in Lubbock, Texas. The energy resources included in the study are solar photovoltaic and wind energy. For the ease of study, a 120-acre cultivable land area is considered as model. Simulation and analysis of the load is developed using HOMER (Hybrid Optimization Model for Electric Renewable) software and the optimum use of renewable resources is determined. A RT-LAB based model is also developed to determine real time analysis of center Pivot load. As the impact of wind is remarkable and solar irradiance is significant in Lubbock area, the wind turbine and solar photovoltaic system is given priority for effective optimization. Using HOMER software and RT-LAB based analysis of different combinations and multiple components are considered for simulation study. An optimal solution is proposed in the work by considering the renewable energy resources as prime sources in Lubbock area for this optimization method.

IEEE Conferences

Authors: V. Roy; S. S. Noureen; S. B. Bayne; A. Bilbao; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8671342

Abstract: Recent advancement in Power System Analysis shows that implementation of PMU (Phasor Measurement Unit) in Smart Grid playing a significant role over SCADA. The main reasoning for that is more sampling data than traditional SCADA system. Every PMU data like voltage, current and Phase angle gives more samples in every second which is helpful for event detection. The enormous data send by each PMU in every second energies the big data issue. To find out and predict the transient situation and even small disturbances or anomalies from big data analysis within the specified short period of time is a challenge for near future. Because introduction of new smart electrical devices will boost up the big data issue. Processing of big data for post disturbance analysis is also an important task. This paper gives a scenario of PMU measurements received to PDC (Phasor Data Concentrator) from PMUs placed in distinct locations and detection of transient events for post disturbance analysis. In this analysis, the disturbances are evaluated with the R programming analysis and compare findings of chronological data from separate locations and also shows the relation between disturbances in a grid. For this analysis, the impacts of frequency and voltage data are also considered.

IEEE Conferences

Authors: Giesselmann, M; Bayne, S; Shamin, N; Kelley, M; Reale, D; Cingoz, F

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8936837

Abstract: We are reporting on models for a group of inverters that can feed real and reactive power into a utility grid in Grid-Tied mode and is able to smoothly transition to islanded mode. In grid tied mode, the inverters are operating in P/Q mode and inject controllable amounts of real and reactive power into the grid. In islanded mode the inverters are grid forming and share power using droop control. We are presenting MatLAB-Simulink models and results of the simulations including the transitions.

Conference Paper/Presentation

Authors: M. Giesselmann; V. Roy

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8936816

Abstract: LTspice is a powerful simulation language that is specifically optimized for modeling Switch Mode Power conversion. It is not limited to small numbers of nodes and freely available [1]. We are presenting several examples of simulations for popular electronic power factor correction circuits that improve the input power factor of AC Power Supplies by active wave-shaping of the AC input current and the associated avoidance of harmonics. The simulations are performed using a cycle-by cycle switching approach as well as using a time averaged PWM model. A fast inner current loop is controlling the shape of the input current such that it matches the sinusoidal shape of the AC input voltage. A time averaged PWM model is useful for fast simulations covering many cycles to design and study secondary feedback control that regulates the output voltage of the converter.

Conference Paper/Presentation

Authors: Zhang, Z; Giesselmann, M; Mankowski, J; Dickens, J; Neuber, A; Joshi, RP

PDF: https://scholars.ttu.edu/en/publications/evaluation-of-high-field-andor-local-heating-based-material-degra-14

Abstract: A molecular dynamics ( MD) model is used to study the potential for mass ejection from a metal nanoprotrusion, driven by high fields and temperature increases. Three- dimensional calculations of the electric fields surrounding the metal emitter are used to obtain the Maxwell stress on the metal. This surface loading is coupled into MD simulations. Our results show that mass ejection from the nanotip is possible and indicate that both larger aspect ratios and higher local temperatures will drive the instability. Hence it is predicted that in a nonuniform distribution of emitters, the longer and thinner sites will suffer the most damage, which is generally in keeping with the trends of a recent experimental report ( Parson et al 2014 IEEE Trans. Plasma Sci. 42 3982). A possible hypothesis for mass ejection in the absence of a distinct nanoprotrusion is also discussed.

Journal

Authors: A. S. Subburaj; S. B. Bayne; M. G. Giesselmann; M. A. Harral

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7175004

Abstract: This paper provides steady-state and transient analysis of the equivalent circuit of the 1 MWh battery tied to the grid for wind integration. It also discusses the installation of a 1 MWh battery system at Reese Technology Center (RTC) in Lubbock, Texas. The research involves deploying energy storage devices for application with wind turbine model to understand the transient behavior of the system under three phase fault conditions. A 1 MW/1 MWh battery storage system at the RTC is connected to the South Plains Electric Cooperative (SPEC) grid. The batteries are used for energy storage and for mitigation of transient conditions grid dynamics. In this paper, the equivalent circuit of the 1 MWh battery is modeled in PSCAD and analyzed for its charge and discharge characteristics under transient fault conditions when it is tied to the grid for wind integration.

IEEE Journals

Authors: A. V. Bilbao; M. G. Giesselmann; S. B. Bayne

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8012811

Abstract: Rapid capacitor chargers are typically used to charge a bank of capacitors with the purpose of discharging it into a pulsed power load [1,3]. Previous research shows that the charging voltage of the load can be accurately calculated in real-time using microcontroller software algorithms [1,5]. The objective of this paper is to report a hardware based approach to measure the charge transfer into the load capacitor and implicitly the capacitor charging voltage. The proposed circuit uses operational amplifiers in order to integrate the input charge. A microcontroller receives the integrated signal to compute the output voltage and stop the charging process when the target voltage has been reached. Failure to accurately detect the end of charge time could lead to an excessively large capacitor bank voltage. For this reason, the proposed method can be utilized as a primary means of end-of-charge detection in conjunction with a traditional voltage sensing scheme.

IEEE Conferences

Authors: A. V. Bilbao; J. A. Schrock; M. D. Kelley; E. Hirsch; W. B. Ray; S. B. Bayne; M. G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8012882

Abstract: Silicon carbide power semiconductor devices are capable of increasing the power density of power electronics systems [1, 2]. In recent years, devices rated to block voltages up to 20 kV have been demonstrated [3]. These research grade devices must be fully characterized to determine operating characteristics as well as failure mechanisms. The purpose of this paper is to demonstrate the continuous switching performance of ultra-high voltage metal oxide semiconductor field effect transistors (MOSFET) rated for 15 kV / 10 A. A high voltage boost converter was developed to evaluate the continuous switching performance where the high-voltage MOSFET is utilized as the main switching element. During operation, the on-state voltage, gate leakage current, and dc characteristics are monitored to determine device degradation. Measured device degradation is presented as a comparison of initial and final dc characterization.

IEEE Conferences

Authors: Hirsch, EA; Schrock, JA; Lacouture, S; Bilbao, A; Bayne, S; Giesselmann, M; O'Brien, H; Ogunniyi, A

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8012879

Abstract: Silicon Carbide (SiC) is a leading wide bandgap semiconductor for increasing the power density of high power applications. This paper overviews the long term reliability and safe operating area of 15 kV SiC PiN diodes during pulsed current conditions. An automated system is used to stress these devices with ultra-high current pulses and monitor degradation with in-system characterization. The system is capable of a 100 mu s full-width half maximum pulse width up to 15 kA, with a repetition rate of 0.5 Hz. Periodic in-system characterization measures device forward conduction and reverse breakdown. The devices in this paper are pulsed at current levels from 1.5 kA to 2.5 kA. Over 100,000 pulses at 1.5 kA have been performed with no degradation. The long term reliability and failure mode results for the 15 kV PiN diodes will be reviewed.

Conference Paper/Presentation

Authors: J. A. Schrock; E. A. Hirsch; S. Lacouture; M. D. Kelley; A. V. Bilbao; W. B. Ray; S. B. Bayne; M. Giesselmann; H. O'Brien; A. Ogunniyi

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7482767

Abstract: SiC SGTO thyristors are an advanced solution for increasing the power density of medium voltage power electronics. However, for these devices to replace Si thyristor technology in industrial applications their characteristics and failure modes must be understood. This letter presents the failure modes of two 15-kV SiC SGTO thyristors during repetitive overcurrent conditions. The devices were evaluated with 2-kA (3.85 kA/cm2) square pulses of 100 μs duration using a pulse forming network. Throughout testing, each devices' static characteristics were analyzed for signs of degradation; upon degradation, testing was ceased and the physical failure mode was determined through imaging with a scanning electron microscope (SEM) in conjunction with a focused ion beam. The electrical results demonstrate the failure modes of both SiC SGTO thyristors during pulsed overcurrents electrically manifested themselves as a conductive path through the gate-anode junction and an increased device on-state voltage. SEM imaging revealed one SiC thyristor formed an approximately 10-μm wide cylindrical void, and the second SiC thyristor formed an approximately 200-μm long crack. However, the experimental results demonstrate these 15-kV SiC SGTO thyristors' robust ability to repetitively switch at extreme high current density for tens of thousands of cycles.

IEEE Journals

Authors: S. Abedi; M. He; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7747960

Abstract: Real-time actuation of scheduled reserve capacity in power system operations with high penetration of wind power is prone to failure on account of unexpected shortcomings in network transfer capability. In this paper, a graph partitioning-based reserve zoning method is incorporated into the security-constrained unit commitment to improve the deliverability of operating reserves in a reserve zone and mitigate possible congestions caused by uncertain wind power. A graph representation of power system is proposed in which the edge weights are quantified by the likelihood of secure transmission utilization for each line. The probability distribution of line flows are characterized by the uncertainty of multiple correlated wind farm output forecasts as well as credible line outage contingencies reflected on the line flows using distribution factors. The minimum k-cut problem using the Gomory-Hu equivalent tree is addressed as a simple and efficient method to solve the NP-complete partitioning problem. The resultant zones can assure reduced risk of congested operating conditions and thus, provide a new approach to efficient management of intra-zonal congestions.

IEEE Conferences

Authors: S. Ramabhotla; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7462516

Abstract: A microgrid integrated with Distributed Energy Resources (DERs), Energy Storage, and Controllable Loads along with critical and non-critical loads is considered. The operation and maintenance cost (O&M) optimization is performed by the Economic Dispatch using the Reduced Gradient Method in the grid connected mode of microgrid. The minimized cost function of the system must be obtained for the optimization of the O&M cost of microgrid while meeting the load demand. The O&M cost includes the operation and maintenance cost of generated energy by each source and also the energy purchased from the utility. For obtaining the minimum cost of the system, the reduced gradient algorithm is implemented. To improve the reliability and to enhance the economic dispatch operation, a diesel generator and a battery energy storage are included in the microgrid. Different scenarios of the energy sources are compared along with the change in wind and battery profiles of microgrid to obtain the minimum O&M cost of the system. Various profiles of battery and wind energy are considered and minimal O&M cost of each profile is obtained and compared. As a result, the optimal cost of the system is obtained by considering the change in wind and battery profiles and hence provides the optimal solution while meeting the critical and non-critical loads demand.

Conference Paper/Presentation

Authors: S. Ramabhotla; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7462530

Abstract: In a microgrid, PTC Wind Solutions is used toimplement the optimization of reliability with the help of FaultTree Analysis (FTA). The reliability of each energy source alongwith the non-critical load is calculated. To interpret the faulttree results, the quantitative and qualitative analysis arecalculated. Then the importance measures like RiskAchievement Worth, Risk Reduction Worth, CriticalityImportance and Fussel -- Vesely Importance are used tocalculate the sensitivity and uncertainty of fault tree results. Thecomponents which are sensitive and at high risk are calculatedfrom the results. Using the logic gates in the PTC WindchillSolutions, the entire fault tree for a non-critical load outage isbuilt and studied. From the results, the unreliability andunavailability of the fault tree are used to calculate thereliability and availability of non-critical load outage. From theFault Tree Analysis, the unavailability and unreliability of noncriticalload outage are calculated which illustrates the values ofavailability and reliability. From the fault tree analysis, theunavailability and unreliability of non-critical load outage arecalculated as 0.01228, which illustrates that the availability andreliability as 98.77%. Minimal cut sets of circuit breaker acrossthe non-critical load, Point of Common Coupling at the maingrid, and a transformer are calculated from the QualitativeAnalysis. The top event probability evaluation of a non -- criticalload is performed using the Quantitative analysis whichindicates the system failure probability. The calculation ofImportance measures -- Risk Achievement Worth, RiskReduction Worth, Criticality Importance, Fussel -- VeselyImportance is performed. Thus, the reliability and availabilityof non-critical load is obtained using the PTC WindchillSolutions. The top event occurrence is caused by the basic andintermediate events of a fault trees. The components at high riskare calculated using the importance measures. Therefore, fromthe Qualitative and Quantitative analysis the components whichare at high risk and sensitive are obtained and maintained wellto optimize the reliability.

Conference Paper/Presentation

Authors: J. A. Schrock; E. A. Hirsch; A. Bilbao; S. Lacouture; W. Ray; S. Bayne; M. Giesselmann; A. Ogunniyi; H. O'Brien

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8012878

Abstract: Silicon carbide Super Gate Turn-Off (SGTO) thyristors are an advanced technology for increasing the power density of high voltage pulsed power or power electronic systems. However, the transient characteristics and failure modes of these devices have to be further understood. This paper presents the Atlas TCAD simulation of a 15 kV SiC SGTO thyristor during extreme pulsed overcurrent conditions. The simulated device is first validated against dc measurements of a physical device. The device is then simulated at various pulse current amplitudes using a 10 stage 100 μs PFN. In addition, a tradeoff study for the drift region and anode mesa width is performed.

IEEE Conferences

Authors: Bilbao, AV; Schrock, JA; Ray, WB; Kelley, MD; Holt, SL; Giesselmann, MG; Bayne, SB

PDF: https://aip.scitation.org/doi/10.1063/1.4927822

Abstract: Obtaining accurate collector to emitter voltage measurements when characterizing high voltage silicon carbide (SiC) devices requires the ability to measure voltages in the range of zero to 10 V while the device is in the on-state and the ability to withstand ultra-high voltages while the device is in the off-state. This paper presents a specialized voltage probe capable of accurately measuring the aforementioned range. A comparison is made between the proposed probe and other commonly used high voltage probe alternatives in relation to high voltage SiC device testing. Testing of the probe was performed to ensure linearity, high accuracy, and high bandwidth. (C) 2015 AIP Publishing LLC.

Journal

Authors: Lacouture, S; Schrock, JA; Ray, WB; Hirsch, EA; Bayne, S; Giesselmann, M; O'Brien, H; Ogunniyi, A; Scozzie, C

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7296932

Abstract: While Silicon Carbide (SiC) based power switching elements are starting to appear that are able to perform better than their Si counterparts in terms of voltage hold off, current density and operating temperature, the material is still relatively new in the semiconductor arena, and although new device designs are simulated extensively before being committed to fabrication, there is often a large discrepancy between actual device performance and simulated results. Manufacturers certainly carry out some electrical testing of these quasi experimental components, but there is a dearth of information pertaining to Safe Operating Area (SOA) and device longevity. Texas Tech University's Center for Pulsed Power and Power Electronics, in cooperation with Army Research Lab, has carried out extensive long term, high - energy testing of SiC Super Gate Turn Off Thyristors (SGTOs) produced by Cree Inc. To conduct this extremely high volume testing at high energy levels, an automated test bed was designed that pulses the devices for an arbitrary number of cycles and alternately switches the device to a low energy characterization system, with all waveforms and current - voltage characteristics recorded. Approximately 350,000 high energy cycles on various SGTOs have been recorded. From this large database of results, actual SOA at high cycle count (>> 10,000 pulses) has been extracted for the devices. With each cycle's waveforms recorded, and the devices' characteristics traced at chosen intervals, several distinct changes in these parameters have been found to inevitably herald the imminent failure of a device. The most common change is in the gate - anode junction, where curve traces show a leaking, almost resistive behavior immediately before the junction becomes forward biased. As the system is completely automated, and limits can be set to halt a test sequence upon being broached, several devices have been brought to the brink of failure - an event that is usually catastrophic, physically destroying the device - to be examined by the manufacturer.

Conference Paper/Presentation

Authors: M. G. Giesselmann; A. Bilbao

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7297019

Abstract: We are reporting on a comprehensive study on protective de-coupling networks for High Voltage (HV) pulsed power charging supplies. Typically HV power supplies charge large capacitor banks [1, page 3], [2, page 4], which are rapidly discharged into a pulsed power load. Even during a normal discharge, this can put severe stress on the power supply if it is not properly decoupled from the load. A fault at the load capacitor such as a flashover resulting in a ringing discharge with voltage reversal would put even more stress on the power supply, since the load capacitor could discharge through the rectifier diodes in forward direction. In such a case the output rectifier of the power supply could be instantaneously destroyed. Protective networks between the power supply and the load can prevent such damage but may limit the efficiency as well as the available power output and rep-rate of the HV power supply. We are reporting on a number of protective networks including combinations of resistors, inductors, and diodes that can be placed between the output of the power supply and the load. We are also considering the effects of parasitics and the surge I²t action integral [3, Page 20] of the output rectifiers of the power supply to arrive at guidelines for optimal system protection.

Conference Paper/Presentation

Authors: M. He; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7131804

Abstract: Microgrids, as individual controllable entities that can operate either islanded from or interconnected to main power grid, have emerged as a promising solution to improving energy efficiency and resilience to disturbance. When linked together in a self-organized manner, a cluster of microgrids can significantly enhance the reliability and power quality for critical load. With this insight, we study the self-organization and decentralized energy management of a microgrid cluster islanded from main grid after a disruptive event. In the self-organization stage, depending on the available generation resources, each microgrid decides on whether to connect to the cluster; and the microgrid energy management systems then “negotiate” on the optimal power exchange with each other in the cluster. Once the power exchange is determined, the generation and storage resources of each microgrid are managed to guarantee the energy reliability of critical loads and overall energy efficiency, through a scheduling procedure followed by a dispatch procedure. The effectiveness of the proposed method is revealed via case studies.

IEEE Conferences

Authors: M. He; S. Nimmagadda; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7285973

Abstract: In this paper, a novel scheme for subsynchronous oscillation detection and modal parameter estimation is proposed, by leveraging the rich information contained in high-rate phasor measurements as well as the effectiveness of synchrosqueezing transform for multimodal signal analysis. Specifically, an instantaneous time-frequency representation of a voltage/current signal is first obtained by applying synchrosqueezing transform to the real-time data collected by a phasor measurement unit. The non-zero synchrosqueezing transform coefficients quantify the undamped frequency components of the original voltage/current signal at each time instant. For an unknown number of undamped frequency components, unsupervised clustering is applied to the non-zero synchrosqueezing transform coefficients in the frequency domain, so as to determine how many modes comprise the signal, as well as which mode each non-zero synchrosqueezing transform coefficient belongs to. Then, for each detected mode, the corresponding non-zero synchrosqueezing transform coefficients are utilized to reconstruct a component of the original voltage/current signal. Finally, the magnitude, damping factor and phase angle of each mode are estimated by applying a least square estimation algorithm to the reconstructed component signal. The effectiveness of the proposed approach is revealed through several case studies using IEEE benchmark models. Further, practical issues involving missing data, measurement noise and transform basis functions are also systematically addressed in this study.

Conference Paper/Presentation

Authors: M. G. Giesselmann; T. T. Vollmer; W. J. Carey

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6828765

Abstract: This paper presents a 100-kV high frequency transformer/rectifier package, which is capable of a dual output polarity operation. An H-Bridge inverter drives the primary of the high voltage (HV) transformer at a frequency of 20 kHz. The inverter is driven by a Microchip dsPIC33F digital signal controller using peak current mode control with adaptive slope compensation. The HV-tank has two HV-coax output cables with a grounded shield on each cable. If the center conductor of the coax cable designated as negative output is grounded, positive voltage is obtained from the coax cable designated as positive output and vice versa. This paper provides design details and experimental results from tests of the entire system.

IEEE Journals

Authors: Bayne, S; Lacouture, S; Lawson, K; Giesselmann, M; Scozzie, CJ; O'Brien, H; Ogunniyi, AA

PDF: https://ieeexplore.ieee.org/document/6634860

Abstract: This paper describes the design and implementation of a small-scale pulsed power system specifically intended to evaluate the suitability of experimental silicon and silicon carbide high power Super Gate Turn Off thyristors for high action (500 A(2) s and above) pulsed power applications where energy is extracted from a storage element in a rapid and controlled manner. To this end, six of each type of device was placed in a controlled three phase rectifier circuit which was in turn connected to an aircraft ground power motor-generator set and subjected to testing protocols with varying power levels, while parameters such as offset firing angle were varied. (C) 2014 AIP Publishing LLC.

Journal

Authors: A. S. Subburaj; P. Kondur; S. B. Bayne; M. G. Giesselmann; M. A. Harral

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6824615

Abstract: This paper provides an overview of battery technologies and the grid-connected battery projects that integrate wind. It also discusses the deployment of a battery system at Reese Technology Center (RTC) in Texas. The research at RTC involves deploying energy storage devices (i.e. Batteries with grid-tie inverters) for application in wind farms to understand the interaction between wind energy, the grid and the grid loads. The research work focus on the modeling of a battery system and wind turbines when it is connected to the grid, with the aim to understand the optimized energy flow between the battery, the wind farm, and the utility grid, energy management for storage, battery performance, energy dispatch and reliability. With the view of modeling the test bed of the grid-connected battery project at Reese, this paper provides the preliminary simulation results using PSCAD on discharge characteristics of a single cell of a battery at various C rates.

Conference Paper/Presentation

Authors: A. S. Subburaj; S. B. Bayne; M. G. Giesselmann; M. A. Harral

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6839166

Abstract: This paper provides an analysis of the equivalent circuit of the 1 MW battery tied to the grid. It also discusses the installation of a 1 MWh battery system at Reese Technology Center (RTC) in Lubbock, Texas. The research involves deploying energy storage devices for application in wind farms to understand the interaction between wind energy, the grid and the grid loads. A 1 MW/1 MWh battery storage system at the RTC is connected to the South Plains Electric Cooperative (SPEC) grid. The batteries are used for energy storage and for mitigation of transient conditions grid dynamics. In this paper the 1 MW battery is modeled in PSCAD and analyzed for its discharge characteristics when it is tied to the grid.

Conference Paper/Presentation

Authors: M. G. Giesselmann; A. Bilbao

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7287357

Abstract: We are reporting on a software implemented HV-sensor for a Digitally Controlled Rapid Capacitor Charger. The new contribution of this paper is to replace a physical voltage sensor with an algorithm that executes in real time in the digital controller for the charger. This avoids the cost, bandwidth limitations and insulation challenges of a conventional HV-sensor. The capacitor charger is controlled by a digital signal controller using a peak current mode control algorithm with adaptive slope compensation as reported in [1]. The peak current mode algorithm uses the analog comparator to detect the peak current and the duty cycle of the inverter at the current peak. Through knowledge of the current waveshape, we can deduct the charge that was transferred during each cycle. This information can be used to predict the voltage of the load capacitor during the charging process. To evaluate the feasibility of this approach, we compare the results from the capacitor voltage prediction algorithm to data obtained with a laboratory grade HV probe.

Conference Paper/Presentation

Authors: S. Ramabhotla; S. Bayne; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7061838

Abstract: Microgrid combines with Distributed Energy Resources (DERs), energy storage, and controllable loads. It is connected to the maingrid through the point of common coupling (PCC). Economic dispatch using reduced gradient method is implemented for the optimization of energy in the microgrid using MATLAB. The optimization is obtained by minimizing the cost function of the system while meeting the load demand. The operation & maintenance cost, and investment costs are considered in the cost functions of the microsources. The minimum total cost of the system is obtained by comparing different scenarios of the microsources in the microgrid.

Conference Paper/Presentation

Authors: Pol, S; Taylor, A; Bilbao, A; Doostalab, A; Novoa, S; Westergaard, C; Hussain, F; Sheng, J; Ren, BB; Giesselmann, M; Glauser, M; Castillo, L

PDF: https://iopscience.iop.org/article/10.1088/1742-6596/524/1/012175

Abstract: As a first step to study the dynamics of a wind farm, we experimentally explored the flow field behind a single wind turbine of diameter 1.17 m at a hub height of 6.25 m. A 10 m tower upstream of the wind farm characterizes the atmospheric conditions and its influence on the wake evolution. A vertical rake of sonic anemometers is clustered around the hub height on a second tower, 6D downstream of the turbine. We present preliminary observations from a 1-hour block of data recorded in near-neutral atmospheric conditions. The ratio of the standard deviation of power to the inflow velocity is greater than three, revealing adverse effects of inflow turbulence on the power and load fluctuations. Furthermore, the wake defect and Reynolds stress and its gradient are pronounced at 6D. The flux of energy due to Reynolds stresses is similar to that reported in wind tunnel studies. The swirl and mixing produces a constant temperature wake which results in a density jump across the wake interface. Further field measurements will explore the dynamics of a model wind farm, including the effects of atmospheric variability.

Conference Paper/Presentation

Authors: M. Giesselmann; T. Vollmer; W. Carey

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6633266

Abstract: A 100kV high frequency transformer / rectifier package was designed and tested which is capable of dual polarity operation. The primary of the transformer is driven by an H-Bridge at a frequency of 20 kHz. The transformer has two HV-coax output cables with a grounded shield on each cable. One of the HV output cables is designated as the positive output terminal whereas the other output cable is designated as the negative output terminal. The shields of both output cables are always grounded. In addition, the core of the transformer is grounded. To obtain either positive or negative output voltage, either of the HV center conductors of the output coax cables is grounded. If the center conductor of the coax cable designated as negative output is grounded, positive voltage is obtained from the coax cable designated as positive output is obtained and vice versa.

IEEE Conferences

Authors: Lacouture, S; Lawson, K; Bayne, S; Giesselmann, M; Scozzie, CJ; O'Brien, H; Ogunniyi, AA

PDF: https://aip.scitation.org/doi/10.1063/1.4823525

Abstract: A high energy, modular, completely automated test bed with integrated data acquisition and characterization systems was successfully designed in order to perform both safe operating area as well as very high volume reliability testing on experimental silicon carbide Super Gate Turn Off (SGTO) thyristors. Although the system follows a modular design philosophy, with each functional block acting as a peripheral to a main control module and can be adapted to arbitrary power and pulse width levels, for the specific SGTO devices initially evaluated it was configured to have the device discharge variable current levels of up to 6 kA into a 0.5 Omega resistive load with a relatively square pulse fixed at 100 mu s full width at half maximum delivering energy levels up to 1.8 kJ to the load. (C) 2013 AIP Publishing LLC.

Journal

Authors: Shelby Lacouture; Kevin Lawson; Stephen Bayne; Michael Giesselmann; Heather O'Brien; Aderinto Ogunniyi; Charles J. Scozzie

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6627575

Abstract: An advanced evaluation system for experimental high power Super Gate Turn Off Thyristors (SGTOs) with built - in custom data acquisition and characterization electronics was designed and built in a cooperative agreement between engineers at Texas Tech University's Center for Pulsed Power and Power electronics (P3 E) laboratory and research scientists at Army Research Lab (ARL). The system consist of a Pulse Forming Network (PFN) energized by a rapid capacitor charger, a data acquisition system which records chosen waveforms for each test cycle and a curve tracing module which the test devices are mechanically switched into to record current and voltage characteristics at arbitrary intervals between high power cycles. Testing is completely automated, with all test parameters including charge level, repetition rate, volume, etc. set within a windows based GUI. The evaluation system has successfully recorded changing I - V characteristics before actual physical failure in several devices. Extremely high volume testing has also been carried out with one device having been cycled over 42,000 times at moderate (2.5 kA) conduction levels.

Conferences

Authors: K. Lawson; S. Lacouture; S. Bayne; M. Giesselmann; H. O'Brien; A. Ogunniyi; C. J. Scozzie

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6634860

Abstract: An advanced evaluation system for experimental high power silicon (Si) and silicon carbide (SiC) Super Gate Turn Off Thyristors (SGTOs) with custom data acquisition and characterization electronics was designed and built in a cooperative agreement between engineers at Texas Tech University's (TTU) Center for Pulsed Power and Power Electronics (P3E) laboratory and research scientists at the U.S. Army Research Lab (ARL). The system consists of a 4.4 kJ Pulse Forming Network (PFN) energized by a 10 kW rapid capacitor charger developed at TTU, a data acquisition system which records chosen waveforms for each test cycle and a curve tracing module which the test devices are mechanically switched into to record current and voltage characteristics at arbitrary intervals between high power cycles. Testing is completely automated, with all test parameters including charge level, repetition rate, volume, etc. set within a custom windows based GUI. The evaluation system has successfully recorded changing I-V characteristics before actual physical failure in several devices. Extremely high volume testing has also been carried out with one device having been cycled over 30,000 times at moderate (2.5 kA) conduction levels. This paper expands on work presented at the 2012 Power Modulator Conference and presents newly acquired data and modifications.

IEEE Conferences

Authors: K. Lawson; S. Lacouture; S. B. Bayne; M. Giesselmann; T. Vollmer; H. O'Brien; C. Scozzie; A. Ogunniyi

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6518751

Abstract: In a collaborative effort between Army Research Lab (ARL) and Texas Tech University's center for Pulsed Power and Power Electronics (P3E) lab, a high power, high energy test bed meant to characterize experimental Si and SiC Super Gate Turn Off (SGTO) devices was designed and built. The system was engineered to run the devices through an arbitrary number of test cycles while recording all pertinent data automatically. Test parameters are set through a windows GUI which communicates with a microprocessor - based control system that orchestrates timing and settings of each subsystem as well as acquiring voltage and current waveforms with high speed ADCs operating simultaneously in parallel. The test waveform itself is generated by a Pulse Forming Network (PFN) which accurately controls rise time, fall time and pulse width. The PFN is charged by a Rapid Capacitor Charger (RCC) system designed at the P3E lab that is capable of 10 kW and allows precise charge voltage levels to be set. Waveforms are acquired through isolated probes specifically designed to capture desired signals even in the presence of a large bias voltages.

IEEE Conferences

Authors: Lacouture, S; Lawson, K; Bayne, S; Giesselmann, M; O'Brien, H; Scozzie, CJ

PDF: https://www.scientific.net/MSF.717-720.1183

Abstract: The development of new semiconductor designs requires that extensive testing be completed in order to fully understand the device's characteristics and performance capabilities. This paper describes the evaluation of experimental Silicon Carbide high power Super Gate Turn Off Thyristors (SiC SGTOs) in a unique test bed that is capable of stressing the devices with very high energy/power levels while at the same time mimicking a realistic, real world application for such devices.

Conference Paper/Presentation

Authors: T. T. Vollmer; M. G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6518827

Abstract: The RCC (rapid capacitor charger) previously developed at the P3E Center [1] has been adapted to charge an 1800 J PFN (pulse forming network) for rep-rated operation. The entire automated system to test and evaluate SGTOs (Super Gate turn-off Thyristors) runs at a 1 Hertz repetition rate; thus requiring a power supply to charge the PFN within 500 ms and have a 3.6 kJ/s average power capability to allow for data acquisition and storage between shots. The hard-switching H-bridge topology with 10 kW burst mode handling capability is very well suited for this compact table top system design. The control of the RCC has been shifted to a PIC controller responsible for PFN charging. Charging parameters include: an adjustable charging time from 50 to 500 ms, high voltage monitoring with adjustable voltage level, and RCC Go/shut-off. All charging parameters are determined by the main CPU handling the automation process and are sent to the PIC controller before each PFN charging event. With the addition of forced air cooled heat-sink for the IGBT modules, enough heat can be removed to allow continuous automated operation.

Conference Paper/Presentation

Authors: R. W. Karhi; D. A. Wetz; J. J. Mankowski; M. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6197742

Abstract: The design and experimental results of a 40-stage distributed energy store (DES) plasma arc railgun are presented. The railgun drives a free running hypervelocity plasma arc, one that is not pushing a payload, to velocities in excess of 10 km/s. These high velocities are of interest as they are required to successfully launch payloads into low earth orbit (LEO). The ability to launch payloads into LEO using a hypervelocity electromagnetic launcher has many financial benefits over the more conventional chemical combustion launchers. In collaboration with an Air Force Office of Scientific Research funded Multidisciplinary University Research Initiative project, the Center for Pulsed Power and Power Electronics at Texas Tech University in Lubbock, Texas has been responsible for developing and investigating a functional scale model of a multistage DES railgun to determine its effectiveness to suppress restrike phenomenon and increase plasma armature railgun performance. The distributed energy scheme is theorized to suppress restrike arc formation because the back emf voltage is localized to active stage regions where high gas density and low temperature inhibits breakdown. B-dot sensors positioned along the length of the launcher provide data to measure the plasma arc velocity and detect restrike, arc splitting, or additional secondary arc formation phenomena.

IEEE Journals

Authors: R. W. Karhi; D. A. Wetz; M. Giesselmann; J. J. Mankowski; J. P. Diehl; P. M. Kelly

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5740614

Abstract: The development process pertaining to the design, fabrication, and testing of a 40-stage free-running arc synchronous distributed energy railgun is presented. Research efforts are still ongoing to suppress the restrike phenomenon that is responsible for causing a velocity ceiling around 6 km/s to exist on plasma armature breech-fed railguns. Numerous solutions have been theorized as viable methods of restrike prevention but lack experimental verification. In collaboration on an AFOSR Multidisciplinary University Research Initiative project, the team at Texas Tech University is responsible for characterizing a functional scale model of a synchronous distributed energy railgun to investigate the effectiveness of a distributed energy scheme to suppress the plasma restrike phenomenon and increase plasma armature railgun performance. The distributed energy scheme is theorized to suppress restrike arc formation because the back-EMF voltage is localized to active stage regions. Synchronous operation refers to the speed of an electromagnetic wave in the LC transmission line formed by the rails and capacitors being matched to the velocity of the armature. The railgun drives a hypervelocity (8 km/s) plasma armature, with no payload, to emulate the conditions of a high-altitude microsatellite launch while relieving the financial burden of a large stored energy facility. Experimental data collected from a seven-stage prototype distributed energy system are discussed which will mimic the design and operation of the first seven stages associated with the final 40-stage system, which is currently under construction. The data collected from this prototype as well as the final 40-stage system will be analyzed for secondary arc formation in an attempt to verify the distributed energy scheme's success in suppressing restrike formation.

IEEE Journals

Authors: R. Karhi; D. Wetz; J. Mankowski; M. Giesselmann; I. El-Dana

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6191671

Abstract: The design and experimental results of a 40-stage distributed energy store (DES) plasma arc railgun are presented. The railgun drives a free running hypervelocity plasma arc, one that is not pushing a payload, to velocities in excess of 10 km/s. These high velocities are of interest as they are required to successfully launch payloads into low earth orbit (LEO). The ability to launch payloads into LEO using a hypervelocity electromagnetic launcher has many financial benefits over the more conventional chemical combustion launchers. In collaboration on an Air Force Office of Scientific Research (AFOSR) funded Multidisciplinary University Research Initiative (MURI) project, the Center for Pulsed Power and Power Electronics (P3E) at Texas Tech University in Lubbock. Texas has been responsible for developing and investigating a functional scale model of a multi-stage DES railgun to determine its effectiveness to suppress restrike phenomenon and increase plasma armature railgun performance. The distributed energy scheme is theorized to suppress restrike arc formation because the back emf voltage is localized to active stage regions. B-dot sensors positioned along the length of the launcher provide data to measure the plasma arc velocity and detect restrike, arc splitting, or additional secondary arc formation phenomena.

IEEE Conferences

Authors: Giesselmann, M

PDF: https://www.sciencedirect.com/science/article/pii/B9780123820365000434

Book Chapter

Authors: Shelby Lacouture; Stephen B. Bayne; Michael G. Giesselmann; Kevin Lawson; H O'Brien; C. J. Scozzie

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6191511

Abstract: The development of new semiconductor devices requires that extensive testing be completed in order to fully understand the device characteristics and performance capabilities. This paper describes the evaluation of experimental Silicon high power Super Gate Turn Off Thyristors (Si SGTOs) in a unique testing environment. The SGTOs are capable of blocking in the forward direction up to 5kV and are also capable of handling several kA when pulsed. The device structure is asymmetric so the reverse blocking of these devices is only a couple hundred volts. Since these devices are SGTOs special consideration had to be given to the gate trigger circuit so that noise would be minimized on the gate therefore preventing false triggering of the devices.

Conferences

Authors: T. T. Vollmer; M. G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6191687

Abstract: We are reporting results on a compact high voltage capacitor charger with modular topology for rep-rated operation. This modular topology utilizes synchronized hard-switching H-Bridge inverters. Each current-mode controlled inverter is fed into the highly coupled primaries of a high frequency transformer with a nano-crystalline core. This charging system with two synchronized H-Bridges has reached voltages of over 20 kV with power outputs in excess of 10 kW. Rep-rated operation along with system efficiency has been explored with this modular topology system. Burst mode operation has achieved rep rates close to 20 Hz. Overall system efficiencies have been measured at nearly 80%.

IEEE Conferences

Authors: Shelby Lacouture; Stephen B. Bayne; Michael G. Giesselmann; Kevin Lawson; H O'Brien; C. J. Scozzie

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6191666

Abstract: This paper details the design of a test platform for experimental silicon and silicon carbide Super Gate Turn Off devices (SGTOs) capable of stressing the devices with very high energy/power levels while at the same time mimicking a realistic, real world application. To this end an aircraft ground power Motor - Generator set was acquired consisting of a high frequency synchronous generator, a D.C. powered brushless exciter machine, and a 100 HP induction motor. The Si SGTO devices were then placed in a three phase controlled rectifier circuit connected between the generator output and a low impedance high power purely resistive load.

Conferences

Authors: David Matia; Hermann Krompholz; Travis Vollmer; Andreas Neuber; Michael Giesselmann; Magne Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5958372

Abstract: A detailed characterization of a 50 J linear transformer driver (LTD) stage is presented. The specific goal of the design is to achieve energy densities superior to typical Marx generators, such as a 500 J compact Marx generator previously designed and built at Texas Tech's Pulsed Power lab. Experimental and analytical techniques for determining circuit elements and especially parasitic elements were used, yielding the magnetizing, primary and secondary leakage inductances associated with the transformer, core saturation effects, parasitic capacitances, the inductance of the pulse discharge circuit, and losses in both copper and the deltamax core. The investigations into these characteristics were carried out using both sinusoidal excitation from 1 kHz to 20 Mhz, and pulsed excitation with rise times down to 5 ns. Pulse amplitudes were varied to cover both the linear and saturation regimes of the core. Distributed parasitic capacitances and the inductance of the pulse discharge circuit were estimated analytically and compared with experimental results. This work was carried out to seek an ideal arrangement of the capacitors and switches on the LTD stage and gain a better basic understanding of fast rise time pulse transformers. Adjustments to the 50 J stage are proposed based on this characterization in order to optimize a future ten stage, 500 J assembly.

Conferences

Authors: M. G. Giesselmann; T. T. Vollmer; L. Altgilbers

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5958381

Abstract: We are reporting on a new compact high power capacitor charger with modular topology for rep. rated High Power Microwave generators and other Pulsed Power Applications. The charger is capable of using a number of synchronized H-Bridge inverters feeding into a common transformer. The common transformer uses litz wire windings and a nano-crystalline core to reduce losses and AC impedance. The H-Bridge inverter modules are individually controlled using peak current mode control which assures proper current sharing and protects the H-Bridge modules from overload while achieving the maximum current handling capacity. To assure stability of the current loops for peak current mode control, slope compensation is used. Major advancements over previous designs are the ability to use multiple H-Bridge inverters with proper synchronization, improved efficiency through advanced transformer design and improved current mode control.

IEEE Conferences

Authors: D. Matia; H. Krompholz; M. Giesselmann; A. Neuber; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5386263

Abstract: The design of a 15 kA linear transformer driver (LTD) is presented. The specific goal of this LTD was improved energy density over the 500 J compact Marx generator previously designed and built at Texas Tech's Pulsed Power lab. The design of an individual 50 joule, 30 kV stage is discussed. For successful operation of the LTD, multiple spark gaps have to be fired with low jitter. Possible approaches for the design of a compact, low jitter triggering circuit will be presented as well.

IEEE Conferences

Authors: Ryan Karhi; Michael Giesselmann; David Wetz; Jeff Diehl

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5386257

Abstract: The development process pertaining to the design, fabrication, and testing of a 40-stage free-running arc synchronous distributed energy railgun is presented. Investigation of this type of system will determine the effectiveness of a distributed energy scheme to suppress the plasma restrike phenomenon and increase plasma armature railgun performance. Determined by a computer simulation, the proposed system will have a 1.0 cm ? 1.0 cm square bore cross section and a stage length of 15.24 cm producing a total rail length of 6 meters for 40 stages. A free-arc is utilized to relieve the financial burden of a large stored energy facility. A velocity of 8 km/s is desired to emulate conditions during a high altitude microsatellite launch. To achieve this velocity, pulsed power in conjunction with a low pressure (~ 10 Torr) air environment is required. The pulsed power supplies 15 kJ of energy to provide an armature current (~ 50 kA) for 1 millisecond. A real-time feedback control system will accurately release the stage energy upon arc arrival. Experimental data collected from a 7-stage prototype distributed system is discussed which will mimic the design and operation of the first 7 stages associated with the 40-stage railgun. The copper rail length is 1.2 m long with a 1 cm ? 1 cm square bore cross section and a 15.24 cm stage length. Each distributed energy stage contains a 750 ?F capacitor bank, a thyristor with an anti-parallel diode, and a driver board for triggering. The armature is formed using a plasma injector that is powered by a 40 kV Marx generator. Diagnostics for this examination include rail B-dot probes as well as independent Rogowski coils for each stage. Data collected from the rail B-dot probes will be used to measure the armature position and velocity as a function of time. There is no target velocity for this prototype; repeatable energy module operation, accurate stage triggering, and arc propagation toward the muzzle are the main areas focus. Outcomes of these initial experimental results will aid the development of the 40-stage system.

Conferences

Authors: Michael G. Giesselmann; Travis T. Vollmer

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5386226

Abstract: We are reporting on a new design for a compact high power Capacitor charger with a power output that far exceeds the peak power of previously reported designs. For this purpose we are evaluating parallel modular designs with separate inverters, transformers, & rectifiers and compare them with designs with a larger module size. For larger power implementations with a single inverter, transformer, & rectifier, the main challenge is the design of the inverter using parallel connected IGBT transistors and their current sharing. We are demonstrating an implementation were we are combining 2 H-Bridge inverters in parallel to feed the primary of a 100 kVA compact step-up transformer. Each H-Bridge is using current mode control to enforce current sharing. The oscillators in the current mode control IC's for each H-Bridge are synchronized for this parallel mode of operation. This topology could be expanded to more H-Bridges. In order to reduce the high-frequency impedance and the windings losses of the step-up transformer, litz wire is used for both the primary winding and the secondary windings.

Conferences

Authors: M. Giesselmann; T. Vollmer; M. Lara; J. Mayes

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4743625

Abstract: We are reporting on a compact high power charger which is integrated into compact Marx generators for rep. rated high power microwave generators and other pulsed power applications. The charger uses rectified AC mains input voltages of 120 V single phase or 208 V three phase and produces output voltages of up to ten's of kV with HV output power levels of 10 kW. The rep. rate capability is up to 100 Hz. Major advancements over previous designs are current mode control of the main inverter and improved voltage feedback control.

IEEE Conferences

Authors: M. Giesselmann; T. Vollmer; R. Edwards; T. Roettger; M. Walavalkar

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4743626

Abstract: We are reporting on a compact high voltage (HV) power supply that can be used in the mobile or airborne generation of high power microwave generators. The charger uses rectified AC mains input voltages of 480 V three phase and produces output voltages of more than 55 kV with HV output power levels of 100's of kW continuously. Major advancements over a previous design are the design of the secondary winding of the HV nano-crystalline transformer, the control of the primary inverter and the thermal management and diagnostic of the HV-DC rectifier.

IEEE Conferences

Authors: J. Mankowski; J. Dickens; M. Giesselmann; B. McDaniel; B. McHale; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4033078

Abstract: Experimental results of a distributed energy source railgun are presented. Distributed energy source railguns were first proposed by Marshal in an asynchronous scheme and later by Parker synchronously. Both schemes employ a "traveling excitation wave" to push the projectile along the rail. The primary advantages of such a scheme over the common breech-fed is higher efficiency due to less energy remaining in the rail and lower rail resistive loses. Another advantage is the reduction in the probability of re-strike. However, these advantages are achieved at a cost of higher switching complexity. As a proof of principle experiment, we have constructed a bench-top solid armature railgun with distributed energy sources. Instead of a single, capacitive, breech-fed, energy source, the current is supplied by two storage capacitor banks, placed at different positions along the rail. The switching configuration, which requires a dedicated switch at each capacitor, is realized with sold state switches. The railgun is diagnosed in order to evaluate performance and to appropriately trigger the switches. In addition, experimental results are compared to simulation

IEEE Journals

Authors: Ryan C. Edwards; Michael G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4346175

Abstract: Summary form only given. Nano-crystalline ferro-magnetic core material has very favorable magnetic properties for high frequency power applications. This paper investigates the properties of a nanocrystalline transformer with multiple secondary windings through experimental evaluation over a range of frequencies. Design considerations are addressed with special attention focused on scaling with respect to frequency, leakage inductance, and effective AC resistance of the windings. The data derived from the experimental evaluation yields scaling factors to help determine a transformer design for optimal power density.

Conferences

Authors: Ryan C. Edwards; Michael G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4652473

Abstract: Nano-crystalline ferro-magnetic core material has very favorable magnetic properties for high frequency power applications. This paper investigates the properties of a nano-crystalline transformer with multiple secondary windings through experimental evaluation over a range of frequencies. Design considerations are addressed with special attention focused on scaling with respect to frequency, cores losses, and effective AC resistance of the windings. The data derived from the experimental evaluation helps determine a transformer optimal design for the best power density.

Conferences

Authors: M. G. Giesselmann; R. C. Edwards; M. Lara; J. Mayes

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4345949

Abstract: Summary form given only. We are reporting on a compact high power charger which is integrated into compact Marx Generators for rep. rated High Power Microwave generators and other Pulsed Power Applications. The charger uses rectified AC mains input voltages of 120V single Phase or 208V three phase and produces output voltages of up to 50 kV with HV output power levels of 10 kW. The rep. rate capability is up to 100 Hz. Major advancements over previous designs are current mode control of the main inverter, improved efficiency through advanced transformer design and improved feedback control.

IEEE Conferences

Authors: Giesselmann, M; McHale, B; Neuber, A

PDF: https://ieeexplore.ieee.org/document/4216273

Abstract: We designed and tested several rapid capacitor chargers for rep-rated operation of low-inductance, compact Marx generators with rep-rates ranging from 10 Hz to 100 Hz. All chargers are designed to be packaged in cylindrical volumes with inside diameters in the range of 5 in - 12 in. Our capacitor chargers are based on H-Bridge inverters using ultra fast 600V class IGBTs. The high voltage is obtained by driving step-up transformers with nano-crystalline cores at 30 kHz. These chargers are capable of average DC output power levels of more than 5 kW for short time operation, during which the thermal inertia of the IGBT assembly provides effective cooling (up to seconds). To achieve reliable rep-rated operation of the chargers, we developed HV feedback sensors to monitor the charging process and solid state Marx-style trigger generators to command trigger the discharge of the main Marx.

Conference Paper/Presentation

Authors: W. J. Carey; A. J. Wiebe; D. D. Schwindt; L. L. Altgilbers; M. Giesselmann; B. McHale; K. Heinemann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4084191

Abstract: The development of an autonomous RF radiation package for various applications is presented. This work is a coordinated effort to develop a tightly integrated unit, including the batteries, power supply, Marx generator, and plug and play antennas for various applications. ARC technology has designed the Marx generator and its associated high voltage antennas for this effort. Previous work by ARC has demonstrated 75 mm diameter, 700 mm length diameter Marx generators capable of delivering 200 kV pulses into 50 Omega coaxial cable with sub-nanosecond risetimes, enabling it to drive an antenna and generate high power microwaves. This technology has been re-designed into a reduced length geometry and augmented by inductive charging to permit pulse repetition rates. The antenna is incorporated directly onto the Marx output for efficient energy transfer and for compactness. This package has demonstrated peak electric field strengths up to 4700 V/m at 10 m. Texas Tech University has worked closely with ARC in developing a rapid charging power supply to meet stringent package constraints and still permit high pulse repetition rates. This system has already demonstrated the ability to charge a 50 nF capacitance up to 40 kV with a repetition frequency of 100 Hz, delivering an average power of 4 kW. This paper details the present status of the project, which will be completed in July, 2005. The cylindrical geometry of the final package has a diameter of 155 mm, a length of approximately 1500 mm without the antenna, and a mass of approximately 35 kg, depending upon the chosen antenna implementation. Results of preliminary tests are included.

IEEE Conferences

Authors: Giesselmann, M; McHale, B; Crawford, M

PDF: https://ieeexplore.ieee.org/document/1398070

Abstract: This paper describes work toward transient energy extraction from high-frequency alternators to drive electromagnetic launchers through intelligent triggering of thyristors, or silicon controlled rectifiers (SCR). The work was done using a three-phase, 75 kVA level motor-generator set with a dc machine acting as the load. This system serves as a scale model to develop control techniques for full-scale, multimegajoule applications. With the use of a microcontroller and advanced sensors, the system is able to maintain synchronization of the SCR converter with the generator voltage despite dynamically changing frequency and voltage distortion.

Journal

Authors: M. Giesselmann; B. Palmer; A. Neuber; J. Donlon

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4084329

Abstract: We are reporting on a High-Voltage Impulse Generator, which consists of a step-up transformer, which is driven by new HV-IGBTs (High-Voltage Isolated Gate Bipolar Transistors). The new HV-IGBTs are individually packaged silicon-dies intended for Pulsed-Power Applications. The silicon dies are normally packaged in large modules for locomotive motor drives and similar traction applications. In our work we used the Powerex QIS4506001 discrete IGBT and the QRS4506001 discrete diode, both with a nominal rating of 4500V/60A, derived from continuous- duty applications. Our experiments have shown that the devices are capable of handling currents in excess of 1 kA during pulsed operation.

Conferences

Authors: M. Giesselmann; B. McHale

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4084435

Abstract: We designed and build a rapid capacitor charger for 10 Hz, 500 J/shot operation of a low-inductance, compact Marx generator. The charger uses a hard-switched IGBT H-Bridge Inverter, which drives a 30 kHz, nano- crystalline step-up transformer. The transformer, in addition to the high-voltage rectifier and a trigger- transformer are contained in a section which is filled with transformer oil. The main circuit board also contains a solid-state Marx generator to trigger the main Marx generator. We also implemented a self-powered HV-feedback sensor to stop the charge process precisely at the target voltage. This new sensor greatly enhanced the rep-rated performance of the Marx by preventing pre-fires, since it enabled us to charge aggressively without overshooting the target voltage and have more time for spark-gap recovery.

Conferences

Authors: Giesselmann, M; McHale, B; Crawford, A

PDF: https://ieeexplore.ieee.org/document/1398070

Abstract: This paper describes work towards transient energy extraction from high frequency alternators to drive electromagnetic launchers through intelligent triggering of thyristors/Silicon Controlled Rectifiers (SCRs). The work was done using a 3-phase, 75 kVA level motor-generator set with a DC machine acting as the load. This system serves as a scale model to develop control techniques for full scale, multi-megajoule applications. With the use of a microcontroller and advanced sensors the system is able to maintain synchronization of the SCR converter with the generator voltage despite dynamically changing frequency and voltage distortion.

Conference Paper/Presentation

Authors: Giesselmann, M; Edwards, R; Bayne, S; Kaplan, S; Shaffer, E

PDF: https://ieeexplore.ieee.org/document/1433587

Abstract: The charged controlled model is presented as an effective method to simulate junction barrier schottky (JBS) silicon carbide diodes. Proven as a valuable approach for silicon devices, this model can also account for wide bandgap energy semiconductors. The model was implemented in Orcad's SPICE software package using analog behavioral modelling. The simulation combines the efficiency of a traditional static model with an improved charge controlled model representing transient characteristics of the semiconductor due to stored charge in the depletion layer. The result is an enhanced model that simulates in short period of time. Parameter extraction methods are used to help identify saturation currents, capacitance, resistance, voltages, and modelling coefficients. The simulation results in a close fit to the data taken during reverse recovery of a JBS SiC diode.

Conference Paper/Presentation

Authors: Giesselmann, M; McHale, B; Heeren, T

PDF: https://ieeexplore.ieee.org/document/1433595

Abstract: This paper presents new advances in High-Voltage power supplies, which are used for rapid capacitor charging. We are developing very compact power supplies with input voltages of around 250 V and output voltages of 30-50 kV. The output power levels of these chargers are above 10 kW. These chargers are using state-of-the-art Isolated Gate Bipolar Transistors (IGBTs) as well as advanced packaging methods and other innovative circuitry. In addition, the size and weight of the step-up transformer has been significantly reduced. Design details as well as experimental results are presented.

Conference Paper/Presentation

Authors: M. Giesselmann; T. Heeren; T. Helle

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1277806

Abstract: We are developing compact, high-power chargers for rapid charging of energy storage capacitors. The main application is presently rapid charging of the capacitors inside of compact Marx generators for reprated operation. Compact Marx generators produce output pulses with amplitudes above 300 kV with ns or subns rise-times. A typical application is the generation of high power microwaves. Initially all energy storage capacitors in a Marx generator are charged in parallel. During the so-called erection cycle, the capacitors are connected in series. The charging voltage in the parallel configuration is around 40-50 kV. The input voltage of our charger is in the range of several hundred volts. Rapid charging of the capacitors in the parallel configuration will enable a high pulse repetition-rate of the compact Marx generator. The high power charger uses state-of-the-art IGBTs (isolated gate bipolar transistors) in an H-bridge topology and a compact, high frequency transformer. The IGBTs and the associated controls are packaged for minimum weight and maximum power density. The packaging and device selection makes use of burst mode operation (thermal inertia) of the charger. The present charger is considerably smaller than the one presented in Giesselmann, M et al., (2001).

Conferences

Authors: Giesselmann, M; McHale, B; Crawford, M

PDF: https://ieeexplore.ieee.org/document/1277807

Abstract: This paper describes work towards controlling the output of fast AC-Alternators to drive transient loads through intelligent triggering of SCR (Thyristor) switches. The project entails the extension of methods and techniques that have been developed for high performance control of relatively small and slow turning industrial machines, to the more demanding regime of AC-machines used for kinetic energy storage and fast AC-servos for military applications. One of these techniques is a rotational transformation, where the (sinusoidal) AC output voltage of an alternator is converted to a DC level representing the instantaneous amplitude. This transformation, also called 'Vector Rotation' can be used for very fast observation of the momentary amplitudes of all electrical machine quantities, since no averaging is necessary. Through the use of vector rotations, advanced sensors and real time signal processing it is possible to demonstrate fast real-time monitoring of the energy extraction from a high frequency AC-Alternator with a full-bridge SCR converter. A low-voltage DC machine was selected as the load for the system, which closely resembles the transient impedance of an electric launcher.

Conference Paper/Presentation

Authors: Giesselmann, M; McHale, B; Crawford, M

PDF: https://ieeexplore.ieee.org/abstract/document/1179842

Abstract: This paper describes the use of methods and techniques that have been developed for high-performance control of relatively small and slow turning industrial machines and extend these techniques to the more demanding regime of ac machines used for kinetic energy storage and fast ac servos for military applications. In particular,this paper describes a technique for fast monitoring of the output voltage of ac generators. To accomplish fast monitoring, the (sinusoidal) ac output voltage is converted to a dc quantity that represents the instantaneous amplitude. This is achieved through the use of a rotational transformation. This transformation, also called vector rotation, can be used for very fast observation of the momentary amplitudes of all electrical machine quantities, such that averaging of the ac value (to determine 66 momentary average rms amplitude) is not necessary. The procedure is implemented by tightly integrating a digital motion control coprocessor into the memory map of a 16-bit microcontroller.

Journal

Authors: M.G. Hoffman; J.C. Dickens; M.G. Giesselmann

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1277679

Abstract: This paper presents a study of temperature variations in a Pulse Power Thyristor (PPT) during and after discharge. The PPT studied was the SPT411BHT. The SPT411BHT is a 5000 V, 4600 A, 125 mm thyristor made by Silicon Power Corporation. In order to determine the temperature of the PPT silicon, a 125 mm diode with identical thermal properties is placed in series with the PPT. There is a strict relationship between the forward voltage and the silicon temperature of the diode. Measurement of the forward voltage of the diode before and after discharge will accurately predict the temperature increase of the silicon. Peak discharge currents will be varied from 30 kA to 90 kA. The forward voltage measurement circuit must be able to resolve millivolts in the presence of common mode voltages in excess of 2 kV. Also, the circuit must isolate the measurement equipment from the circuit. This paper will discuss the temperature measurement concept as well as the design details of the circuit used to measure the diode forward voltage.

Conferences

Authors: Li, SH; Wunsch, DC; O'Hair, E; Giesselmann, MG

PDF: https://reader.elsevier.com/reader/sd/pii/S0743731501918076?token=71560B31268F9710BA7B935A7F74DD34C354362F6C8D93C17299BCA84C8441D51856130912BA0BFE40FBFFDF4E68E8AF&originRegion=us-east-1&originCreation=20221127212026

Abstract: The extended Kalman filter (EKF) algorithm has been shown to be advantageous for neural network trainings. However, unlike the backpropagation (BP), many matrix operations are needed for the EKF algorithm and therefore greatly increase the computational complexity. This paper presents a method to do the EKF training on a SIMD parallel machine. We use a multistream decoupled extended Kalman filter (DEKF) training algorithm which can provide efficient use of the parallel resource and more improved trained network weights. From the overall design consideration of the DEKF algorithm and the consideration of maximum usage of the parallel resource, the multistream DEKF training is realized on a MasPar SIMD parallel machine. The performance of the parallel DEKF training algorithm is studied. Comparisons are performed to investigate pattern and batch-form trainings for both EKF and BP training algorithms. (C) 2002 Elsevier Science (USA).

Journal

Authors: M. Giesselmann; T. Heeren; A. Neuber; J. Walter; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1003943

Abstract: Explosive flux compression generators generate hundreds of kiloamperes and voltages of a few kilovolts. A power conditioning stage is required since typically voltages in the hundreds of kilovolts range are needed. Inductive energy storage systems with an opening switch provide the necessary voltage gain. In our application, the opening switch has been implemented as an exploding wire fuse. The voltage gain, and hence the performance of the system, is greatly dependent on the opening switch. We utilized high-speed optical imaging (up to 10/sup 7/ pictures/s) to assess the performance of the exploding wire fuse.

Journals

Authors: M. Giesselmann; T. Heeren; A. Neuber; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1002018

Abstract: This paper describes an advanced PSpice/sup (R)/ model, which is used to complement the experimental work on explosive flux compression generators. This work is conducted at Texas Tech University in the framework of a MURI program. The results from the model are compared to actual results from generators that have been tested in the authors' laboratory. To achieve better fidelity of the model, the effect of transient current diffusion into the conductors of the generator is modeled by using a ladder network with many concentric layers of each current carrying conductor. For the optimum accuracy, the spacing of the concentric layers is closest at the surface of the conductor. The paper shows results, comparisons with experimental data and applications of the model for the design of power conditioning systems for MFC-generators.

Conferences

Authors: M. Giesselmann; E. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1002177

Abstract: This paper describes the downsizing potential of a power supply for charging a 7.2 /spl mu/F capacitor to a voltage of 30 kV, which represents 3.24 kJ of energy, in approximately 40 ms. This process should be repeatable 10-20 times in a short burst mode within a time frame of a few minutes. The primary supply is a DC source with approximately 650 V. A previous design achieved all these goals using 4 Semikron half-bridge IGBTs rated at 1200 V/1200 A each. From the operational experience with the previous charger we concluded, that the weight and volume of the inverter, which is the core of the system, can be reduced to half of the previous size. This can be achieved by using advancements in IGBT modules as well as state of the art capacitors and optimum packaging. Due to the increased capabilities of the new IGBT modules, the number of required modules can be reduced from 4 to 2. In addition, the 15 V/10 A auxiliary power supply, which was previously required, is no longer needed, since the new modules derive their auxiliary power from the main DC bus. The new IGBT modules will be connected to form an H-Bridge. A step-up transformer and a rectifier bank will be connected to the output of the H-Bridge. For compactness, the cooling fins on the old modules have been removed, which was permissible due to the fact that the supply is only operated in short term burst mode. There are no cooling fins to remove on the new module since we are using the water-cooled version. This also gives us the option to water cool if needed. With these modifications, the original charger, which took up a standard 19 inch equipment rack, could be reduced to the size of an oversized suitcase.

Conferences

Authors: Li, SH; Wunsch, DC; O'Hair, E; Giesselmann, MG

PDF: https://watermark.silverchair.com/327_1.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAA_swggP3BgkqhkiG9w0BBwagggPoMIID5AIBADCCA90GCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMLqEIsrNKWX499X0NAgEQgIIDrgPr5DDONXYdIvN847mijhju9Kb-7XveI73MWHkKe54fkxrS4OkDd9ts4v2RgdrTlsoOBfg_A9rs6hd_up8T-ufk2F1G-pa3csApQlfvjJyV-xDgcCzmm-Q-eiiSkk97OeV7fSs_7MpTXDPm39PLJZp_ALa3Jtln1sGo15JpmMRE7Matft9M_EbqzY0dc854tW9uqPtztDRkvPyxSaiF1hn-apfutVnlcMjTD1Go8m2fJAQQnIZyNMKEafzWu-wBvMZtuwm6ybM0TZTzWy7rDp9J8SIt9fGDs4HhEJY6jE1OCo5107YFD4R7laWW_MMcsdD-CLzfqXkuMvJbuz4cc2XA64mHW7FaP6nd50Qhc6rAQr4A1PJB2PkeXUJP_8Pb-a5PvnIs5aMcuL9rXi4aZ58yl3lGx5i6WacidU3DWgr8DaWawUqQQHg9KxTiwZm35YByDZEtQNluEpX-CKDgJ79YaKDgjtQTw7EqxibqXxHO6FYZa6-05OB6p_TlkZ_f0qQ322Su3s00JCJ1pRc8q-OpgP7wtJp9q0i43ZSoqnR2rohEuK9y-tmSJQgPrMXYujMKsBJr5iwK1L4v7Q8eGS5M39Jym_egxwGulU7envFJKVrZ2weYb9ka8IgEA0ApXMDhxJhVj49gJVoLeakpgj1hheWx4mImtGsLejr2NOJEDWbf-97JhJjTbOq19XrKtc0W-cu4OUa2SlHlQC1CSHKxRLd_B6cPMmVIvvPc9GGTpNV_5yr83xcOorMlgMLd6q19GGP9bw9HVynbUEd2gDOAih0ViOu2RE3HwSIZy6WvH92nMMMVb-bphAEmKxt48HnyqUwtYh4FNhL9sDCMXDrYchb-KGqpddWiFjMQ_9sn5k18vzzNNTT8qOPy5I5E-rqr7wAZbDqvdbcobV0zjzbr979hFDsq1kUxHjHIGCK7xPrPpXKn1q_icXbfo9TwjkP1i2nOVOXZU76BrGqSQDRq6hLZgAASIU9LjVOzbjkZOlQ3PnmUGaHm6TTbEFs2dBjfPOUdOSBtj1Z0RgUVsSgnYJ_ixwrfxJVQyoPCuhMLqkm_7efUPiQMY0zlP4NBQxOeSyb11bYikTfYynUp6dftfkxtJUMVAuo1jVc8B4PLEC_UXHMnoSLDN_V2-Ozk5cz2cIDKY3JLCCCfAzdgmPyITkrw5I-DHp8Pszd6HkRt_LalIlYekKNB2BeS3Z0LtgplCDsznDED2-n4t-SZtkaXaH6OrLvSpuZhKaICfA

Abstract: This paper examines and compares regression and artificial neural network models used for the estimation of wind turbine power curves. First, characteristics of wind turbine power generation are investigated. Then, models for turbine power curve estimation using both regression and neural network methods are presented and compared. The parameter estimates for the regression model and training of the neural network are completed with the windfarm data, and the performances of the two models are studied. The regression model is shown to be function dependent, and the neural network model obtains its power curve estimation through learning. The neural network model is found to possess better performance than the regression model for turbine power curve estimation tinder complicated influence factors.

Journal

Authors: A. Neuber; J. Dickens; J. B. Cornette; K. Jamison; E. R. Parkinson; M. Giesselmann; P. Worsey; J. Baird; M. Schmidt; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=940950

Abstract: A variety of basic magnetic flux compression (MFC) generator geometries have been tested during the last three decades. Though size and operating regimes differ widely, it is apparent that the helical flux compression generator is the most promising concept with respect to current amplification and compactness. Though the geometry of the helical generator (dynamically expanding armature in the center of a current carrying helix) seems to be basic, it turns out that the understanding of all involved processes is rather difficult. This fact is apparent from the present lack of a computer model that is solely based on physical principles and manages without heuristic factors. A simple generator was designed to address flux and current losses of the helical generator. The generator's maximum current amplitude is given as a function of the seed current and the resulting "seed-current" spread is compared to the output of state-of-the-art computer models. Temporally resolved current and current time derivative signals are compared as well. The detailed generator geometry is introduced in order to facilitate future computer code bench marking or development. The impact of this research on the present understanding of magnetic flux losses in helical MFC generators is briefly discussed.

IEEE Journals

Authors: M. Giesselmann; T. Heeren; A. Neuber; J. Walter; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1002004

Abstract: This paper presents high-speed optical diagnostics of an exploding wire fuse, which is used in the power conditioning system for an explosive flux compression generator. The images were taken using an IMACON(R) 790 high-speed framing camera utilizing a gated image intensifier tube. For the authors' measurements, the camera was operated in the high-speed multiple frame mode, yielding 8-10 sequential, 2 dimensional pictures with 100 ns between exposures.

Conferences

Authors: Giesselmann, M; Eccleshall, D

PDF: https://ieeexplore.ieee.org/document/911805

Abstract: A PSpice (R) model for a 4-phase, 4-pole air core compulsator was created. With minor modifications it could also model the performance of other pulse alternators. In addition, models for a railgun and switching elements have been created. The models were used to evaluate the system performance of the compulsator and an attached railgun in various configurations with diode rectifiers and SCR's. The process of self-excitation of the machine was also studied. The paper is focusing on the basic theory behind the models as well as techniques for numerical implementation, In addition generic results using normalized parameters are given.

Journal

Authors: Li, SH; Wunsch, DC; O'Hair, EA; Giesselmann, MG

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=937208

Abstract: This paper uses data collected at Central and South West Services Fort Davis wind farm to develop a neural network based prediction of power produced by each turbine. The power generated by electric wind turbines changes rapidly because of the continuous fluctuation of wind speed and direction. It is important for the power industry to have the capability to perform this prediction for diagnostic purposes-lower-than-expected wind power may be an early indicator of a need for maintenance. In this paper, characteristics of wind power generation are first evaluated in order to establish the relative importance for the neural network. A four input neural network is developed and its performance is shown to be superior to the single parameter traditional model approach.

Journal

Authors: Bayne, SB; Giesselmann, MG

PDF: https://ieeexplore.ieee.org/abstract/document/870874

Abstract: Renewable energy such as wind and solar is a clean source of energy that can be integrated with conventional ways of producing energy. Power utility companies are looking at ways to integrate renewable energy with conventional methods. The Central and South West (CSW) renewable project was designed to investigate the role of solar and wind energy in a utility system. When connecting a wind farm to a utility grid, several issues must be taken into consideration such as stability, load matching, cost, location and the wind profile in relation to the peak loads on the system. One other parameter that is seldom considered is the effect of power oscillations due to turbine blades passing through their full are of motion and periodically encountering different wind speeds at different vertical positions. In the following, this effect is called 'blade passing' for short. This paper evaluates the effect of blade passing on the output voltage and current for a grid connected wind farm. The effect of blade passing as a function of the number of wind turbines connected to the grid is also investigated. The exact causes of the blade passing effect are also discussed.

Conference Paper/Presentation

Authors: Giesselmann, M; Kristiansen, M; Grinstead, B; Wilson, M

PDF: https://www.scopus.com/record/display.uri?eid=2-s2.0-0034508877&origin=inward&txGid=9189bf197e8c232dbc11eddcc58886a1

Abstract: A pulse generator, constructed by a group of Russian scientists, which is using a solid state opening switch (SOS), was characterized and tested, The diode acts similar to a step recovery diode but has voltage and current ratings that exceed the levels in US manufactured step-recovery diodes by orders of magnitude. To the authors knowledge, there are no US manufactured diodes for the application described here, With the load chosen for this paper, the generator produces pulses of 100 kV amplitude and 10 ns bah width, using a 600V DC supply. The maximum pulse repetition rate is 100 Hx, limited by thermal considerations of the primary charging resistor, This limit could be easily overcome by using a switch-mode power supply to charge the primary capacitors, This pulser can be used to generate partial discharges in a chemical reactor in order to produce Ozone for a variety of industrial uses such as sterilization, oxidation, NOx or SOx removal from exhaust gases, etc. The greatest advantage is the long lifetime of this all solid-state device.

Conference Paper/Presentation

Authors: M. Giesselmann; T. Heeren; E. Kristiansen; J. G. Kim; J. C. Dickens; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=901200

Abstract: The pulsed power conditioning system (PPCS) is one of the key enabling technologies for using the energy output of a magnetic flux compression generator (MFCG). This paper shows the results of comprehensive experimental studies of an inductive energy storage system using an exploding wire fuse. The effects of metal oxide varistors (MOVs) for use as pulse-shaping devices are also presented. The experimental results are complemented by a comprehensive evaluation and interpretation of the results using the tools available in the professional version of MathCAD.

IEEE Journals

Authors: A. Neuber; J. Dickens; M. Giesselmann; B. Freeman; D. Dorsey; H. Krompholz; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6220176

Abstract: The design of a helical flux compression generator, driven by 200 g of high explosives, for basic studies is presented and experimental results are discussed. Generator current and dI/dt are measured with Rogowski coils placed on the load. Both crowbar closure and contact velocity have been successfully simulated with CTH, a three-dimensional finite element hydrodynamic code. The generator's magnetic field structure is briefly discussed and magnetic field probe measurements are presented.

IEEE Conferences

Authors: A. Neuber; J. Dickens; M. Giesselmann; B. Freeman; J. Rasty; H. Krompholz; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=855148

Abstract: Summary form only given, as follows. The design of a helical flux compression generator, driven by 150 g of high explosives, for basic studies is presented and experimental results are discussed in comparison to numerical simulations. Simulation of the electric current output with the commercial circuit simulator PSPICE shows that this generator conserves the magnetic flux ideally in the low current mode, <30 kA. At current amplitudes in excess of 100 kA heating and melting of the single wound helix wire, AWG 12, limit the current flow. The volume between armature and stator is spectroscopically probed with fiber optics and valuable insight into the state of the shocked and compressed gas is gained. The same fiber optic probes are used to measure the velocity of the armature-stator contact along the generator axis. This contact velocity is largely affected by armature end effects, mainly due to the pressure loss at the detonator end. Both gas temperature and contact velocity have been successfully simulated with LS-DYNA3D, a three dimensional finite element hydrodynamic code. The generator's magnetic field structure is briefly discussed and magnetic field probe measurements are presented.

IEEE Conferences

Authors: J. Kim; J. Zhang; M. Giesselmann; J. Dickens; J. Mankowski; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=823802

Abstract: In this paper, the simulation and evaluation of energy efficiency and voltage amplification in an inductive energy storage system with resistive, capacitive and diode loads is presented. A numerical simulation with Mathcad shows that by proper reduction of the storage energy inductance and of the exploding fuse interruption time, the energy efficiency and voltage amplification can be greatly improved.

IEEE Conferences

Authors: M. Giesselmann; J. Zhang; T. Heeren; E. Kristiansen; J. Dickens; D. Castro; D. Garcia; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=823810

Abstract: One of the key technologies in a high power microwave system is the pulsed power conditioning system (PPCS). For a system driven by an explosive flux compression generator, the PPCS may consist of an energy storage inductor, a fuse type opening switch and a sharpening spark gap. This paper presents the investigation of a PPCS with a pulse transformer. Before the construction of a prototype, the behavior of the PPCS was simulated using the PSpice circuit simulation code. A transformer with a primary inductance of 3.5 /spl mu/H, secondary inductance of 85 /spl mu/H and coupling coefficient of 0.75, was designed and used in the experiments. The transformer was designed with two coaxial windings. Simulation results as well as experimental waveforms are shown.

IEEE Conferences

Authors: M. Giesselmann; T. Heeren; E. Kristiansen; J. Dickens; D. Castro; D. Garcia; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=823799

Abstract: This paper describes a metal oxide varistor (MOV) pulse shaping device, which is to be used for generating a flat-top voltage pulse for high power microwave devices. The MOV pulse-shaping device is attached to a coaxial pulse compression system. The pulse compression system consists of an inductive energy storage section, an exploding wire fuse and an output spark gap. The paper contains a detailed discussion of the pulse compression system followed by a description of the MOV pulse-shaping device. The MOV elements that are used for this pulse shaping application are the SIOV-E32VR602 type, made by Siemens.

IEEE Conferences

Authors: J. Zhang; J. Dickens; M. Giesselmann; J. Kim; E. Kristiansen; J. Mankowski; D. Garcia; M. Kristiansen

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=823610

Abstract: To improve the pulse shape and to obtain /spl mu/s order pulse duration on a diode load in an inductive energy storage system, an oil-submerged compact pulse transformer with diameter of 20 cm and length of 70 cm has been designed and tested. From theoretical calculations, the parameters with primary inductance L/sub p/=3.4 /spl mu/H, secondary inductance L/sub s/=90 /spl mu/H, and coupling coefficient K=0.772 are obtained. To prevent breakdown, a conical secondary design is adopted. Under the condition of 500 kV operation voltage, the maximum electric field in the transformer is 205 kV/cm (in oil). The axial voltage distribution on the secondary is linear. Experiments have been done to test the insulation, the mechanical force and the coupling coefficient. The test results are consistent with the design parameters.

IEEE Conferences

Authors: Giesselmann, MG; Haider, MR

PDF: https://ieeexplore.ieee.org/document/741236

Abstract: Prototypes of three-phase synchronous rectifiers using power MOSFETs including the necessary control circuitry have been developed and tested. Experimental results show a significant reduction of conduction losses at room temperature and large additional improvements if the MOSFETs are cooled with liquid nitrogen. The synchronous rectifier is proposed to be used as part of a power system for a next generation ground based radar (GBR) system.

Conference Paper/Presentation

Authors: Giesselmann, MG

PDF: https://ieeexplore.ieee.org/document/659210

Abstract: This paper shows computer models for common switch-mode converters with averaged and conventional cycle by cycle switching operation. Models for the Buck, Boost, Buck-Boost, and Cuk converter are presented. Also shown are Buck and Boost converters with integrated magnetic components. All time averaged models are using an identical averaged model for the PWM switch. The models are implemented using PSpice(R) for Windows(R). The advantage of averaged models are much faster execution time as well as the ability to perform frequency domain (bode plots) analysis in addition to time domain analysis.

Conference Paper/Presentation

Authors: Giesselmann, M

PDF: https://www.scopus.com/record/display.uri?eid=2-s2.0-0030705759&origin=inward&txGid=7ba1673c2d729b3f35d9311f658fd8c3

Abstract: This paper presents the dynamic model of a 3-phase synchronous machine using the graphical user interface provided by the PSpice program environment. The machine model includes the effects of the damper winding and salient poles. The paper presents results of the dynamic behavior of a salient pole synchronous machine including voltage, current, torque, and power traces. The model is organized in a hierarchical structure and includes custom symbols for the machine several functional modules like reference frame transformation modules. The custom symbols have been created within the Schematics editor of the PSpice program group. Details of the implementation as well as the theoretical equations are presented. The model that is shown in this paper is working on the free evaluation version of the PSpice software, Release 6.2a.

Journal

Authors: J. Dickens; M. Kristiansen; M. Giesselmann; J. G. Kim

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=679365

Abstract: A Russian power modulator, which is based on a diode that has been touted as a high-power solid-state pulsed power opening switch (SOS) was characterized and tested. The diode has characteristics similar to those of a step-recovery diode, except that the reverse current density is 10-100 times larger than in US manufactured diodes. The modulator has a DC input voltage of 600 V and produces a pulse of 150 kV amplitude and 25 ns half width into a 350 /spl Omega/ load. The maximum pulse repetition rate is 100 Hz. The limit is given by thermal limitations and can be increased through the use of more effective cooling methods.

IEEE Conferences

Authors: Li, SH; Wunsch, DC; OHair, E; Giesselmann, MG

PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=611648

Abstract: The power generated by electric wind turbines changes rapidly because of the continuous fluctuation of wind speed and direction. It is important for the power industry to have the capability to estimate this changing power. In this paper, the characteristics of wind power generation are studied and a neural network is used to estimate it. We use real windfarm data to demonstrate a neural network solution for this problem, and show that the network can estimate power even in changing wind conditions.

Conference Paper/Presentation

Authors: Giesselmann, M; Crittenden, B

PDF: https://ieeexplore.ieee.org/document/564494

Abstract: The design and construction of a Neutral Point Clamped Inverter along with its modulation strategy and circuit simulation using PSPICE 6.2 for Windows is presented. This inverter is a subscale (100 kW) prototype for a inverter that is intended to be used in a 1MW level universal power converter system to produce 3 phase AC power at 60 Hz from variable input sources.

Conference Paper/Presentation

Authors: Giesselmann, MG

PDF: https://ieeexplore.ieee.org/document/552888

Abstract: Different models for switched reluctance machines (SRMs) are presented. All models are developed for the newest version (6.3) of PSpice for Windows. The models demonstrate the software's capabilities to define custom symbols and construct multilevel hierarchical models. PSpice also has strong analog behavioral modeling capabilities that are fully exploited. For this paper, 6-4 motors are simulated, but the models can be extended to other designs. The first model is based on an equivalent circuit representation with linear, voltage controlled inductors. The second model is based on a set of analytical equations which include saturation effects. In both cases, the electrical and mechanical system is modeled. Coupling between the windings is neglected. The models yield information about electrical as well as mechanical parameters such as induced phase voltage and torque. Both models produce comparable results in the unsaturated regime for the phase current. At higher current levels the model based on the analytical equations gives more accurate results.

Conference Paper/Presentation

Authors: Giesselmann, M; Mahmud, Z; Carson, S

PDF: https://ieeexplore.ieee.org/document/564446

Abstract: Operation of power MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) at cryogenic temperatures significantly reduces conduction losses and increases power handling capability. High voltage (1000V+) devices exhibit the largest reduction of conduction losses. The breakdown voltage of the devices is reduced by about 20% when cooled from 75 degrees F down to -319 degrees F.

Conference Paper/Presentation

Authors: CHOWDHURY, G; GIESSELMANN, M

PDF: https://arc.aiaa.org/doi/10.2514/6.1994-3810

Conference Paper/Presentation

Authors: GIESSELMANN, M; ELDRED, C; SEITZ, D

PDF: https://www.scopus.com/record/display.uri?eid=2-s2.0-0027885749&origin=inward&txGid=7c4a2bb1b0de4789c46ed68da174b31e

Conference Paper/Presentation

Authors: GIESSELMANN, M; LOREE, DL

PDF: https://www.scopus.com/record/display.uri?eid=2-s2.0-0027904205&origin=inward&txGid=10cf4925e71d4129011e5dd2736705d2

Conference Paper/Presentation

Authors: LOREE, D; GIESSELMANN, M; KRISTIANSEN, M; LARSON, D

PDF: https://www.osti.gov/biblio/5708171

Abstract: Project Hercules is a project to improve ignitron switches which will then be used on the upgrade of Lawrence Livermore's Nova Laser for their ICF program. The goals of Hercules, which stands for High Energy Research Concerning the Ultimate Lifetime of Experimental Switches, are to lifetime test (up to 10,000 shots) prototype ignitrons or other switches with the required Nova current and coulomb parameters (300 kA, 200 C), recommend design changes, and retest the second generation switches. This report describes the design and construction of the test circuit and necessary diagnostics. The details of the design and construction of a 0.5 MJ electrolytic capacitor bank and a semi-automatic diagnostic/ control system are described. The required test run data include peak current and corresponding tube voltage for every shot, entire current and voltage waveforms every few shots, and ignitor resistance values every few shots. Additionally, the conversion of a 120 kW, 12 kV constant voltage supply to an 8 A constant current supply with the use of six SCRs and a commercial control board will be described. The final results of this project will be lifetime data at high current and high coulomb for and improvements on some of the best of the new generation of pulsed power switches.

Journal

Authors: LOREE, D; GIESSELMANN, M; KRISTIANSEN, M

PDF: https://ttu-ir.tdl.org/bitstream/handle/2346/17351/31295006979529.pdf;sequence=1

Conference Paper/Presentation

Authors: LOREE, DL; GIESSELMANN, M; KRISTIANSEN, M; SHULSKI, A

PDF: https://ieeexplore.ieee.org/document/101020

Abstract: The development of high power ignitrons with peak current ratings of up to 1000 kA and simultaneous charge transfer rates of 250-500 C is currently under way in a joint effort between Texas Tech University (TTU), Lawrence Livermore National Laboratory (LLNL) and industry. Research at TTU is concentrated on plasma diagnostics, novel anode designs, electrode placements and trigger schemes. 1,2,3 Electrical measurements as well as optical plasma studies such as high speed framing photography, Mach-Zehnder interferometry and spectroscopy have been performed. The cooperative efforts have lead to the development of a new commercial tube (Richardson Electronics NL-9000). This paper describes plasma diagnostics performed on a demountable ignitron (DIG) which provides optical access to the discharge plasma through four viewports, two of which are on opposite sides on a common optical axis. The latter pair of viewports was used to perform plasma density studies using a Mach-Zehnder interferometer. Time resolved recordings of the interference patterns, either visually or electronically, during changes in plasma behavior (such as current conduction or plasma heating) yield time resolved information about the particle density This technique was applied to the demountable ignitron during high current discharges. The light source was a 2W CW argon laser which was pulsed using a ferroelectric liquid crystal light valve. The resulting fringe patterns were recorded with a mechanical high speed camera. In the paper all experimental details, results and a theoretical evaluation are given. In addition, high speed framing photography was used to study the influence on electrode design and placement on the discharge plasma.

Journal

Authors: LOREE, DL; GIESSELMANN, MG; KRISTIANSEN, M; SHULSKI, AP; KIHARA, R

PDF: https://ieeexplore.ieee.org/document/201007

Abstract: The development of high-power ignitrons with peak current ratings of up to 1000 kA and simultaneous charge transfer rates of 250-500 C is currently under way in a joint effort between Texas Tech University (TTU), Lawrence Livermore National Laboratory (LLNL), and industry. Two industrial manufacturers, Richardson Electronics, US, and English Electric Valve, UK, have participated with TTU and LLNL in three workshops to advance the state of the art in high-power ignitrons. Less than three years after the start of the program, the cooperative efforts have led to the development of a new commercial tube (Richardson Electronics NL-9000). High power testing of prototypes of this tube and other unique ignitrons was done by Kihara at LLNL. Research at TTU is concentrated on plasma diagnostics, novel anode designs, electrode placements, and trigger schemes. Electrical measurements as well as optical and microwave plasma studies, such as high-speed framing photography, Mach-Zehnder and microwave interferometry, and spectroscopy have been performed. This paper describes the advances made in high-power ignitron switching capabilities in a comparison study between conventional Size D and Size E tubes, demountable experimental tubes and the new NL-9000 (Richardson Electronics). The paper shows the differences in tube design, and the associated peak current and charge transfer capabilities and lifetime expectancies. The critical design criteria are the anode shape and placement in order to control the plasma and prevent prefires. Tube failure modes and recent studies on alternate ignitor schemes are presented. In addition, results of plasma diagnostics performed on a demountable ignitron with optical access to the discharge plasma are shown. Time resolved images of the interference patterns from an optical Mach-Zehnder interferometer were recorded with a mechanical high-speed camera and evaluated with the help of image processing.

Journal

Authors: ADKINS, DL; GIESSELMANN, M; KRISTIANSEN, M

PDF: https://ieeexplore.ieee.org/document/22499

Journal

Authors: SCHAEFER, G; GIESSELMANN, M; PASHAIE, B; KRISTIANSEN, M

PDF: https://aip.scitation.org/doi/10.1063/1.342114

Journal