An Advanced Three-Level Active Neutral-Point-Clamped Converter With Improved Fault-Tolerant Capabilities

A resilient fault-tolerant silicon carbide (SiC) three-level power converter topology is introduced based on the traditional active neutral-point-clamped converter. This novel converter topology incorporates a redundant leg to provide fault tolerance during switch open-circuit faults and short-circuit faults. Additionally, the topology is capable of maintaining full output voltage and maximum modulation index in the presence of switch open and short-circuit faults. Moreover, the redundant leg can be employed to share load current with other phase legs to balance thermal stress among semiconductor switches during normal operation. A 25-kW prototype of the novel topology was designed and constructed utilizing 1.2-kV SiC metal-oxide-semiconductor field-effect transistors. Experimental results confirm the anticipated theoretical capabilities of this new three-level converter topology

Radiation and temperature effects on electronic components investigated under the CSTI high capacity power project

The effects of nuclear radiation and high temperature environments must be fully known and understood for the electronic components and materials used in both the Power Conditioning and Control subsystem and the reactor Instrumentation and Control subsystem of future high capacity nuclear space power systems. This knowledge is required by the designer of these subsystems in order to develop highly reliable, long-life power systems for future NASA missions. A review and summary of the experimental results obtained for the electronic components and materials investigated under the power management element of the Civilian Space Technology Initiative (CSTI) high capacity power project are presented: (1) neutron, gamma ray, and temperature effects on power semiconductor switches, (2) temperature and frequency effects on soft magnetic materials; and (3) temperature effects on rare earth permanent magnets

Comparative Study of Power Semiconductor Devices in a Multilevel Cascaded H-Bridge Inverter

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET and IGBT modeling tools in Saber® were extensively utilized to create the models of the power devices used in the simulations. The inverter system is also analyzed using Saber-Simulink cosimulation method to feed control signals from Simulink into Saber. The results in this investigation show better performances using a SiC MOSFET-based grid-connected BESS inverter with a better return of investment

Switching Performance Evaluation, Design, and Test of a Robust 10 kV SiC MOSFET Based Phase Leg for Modular Medium Voltage Converters

10 kV SiC MOSFETs are one of the most promising power semiconductor devices for next-generation high-performance modular medium voltage (MV) converters. With extraordinary device characteristics, 10 kV SiC MOSFETs also bring a variety of challenges in the design and test of MV converters. To tackle these inherent challenges, this dissertation focuses on a robust half bridge (HB) phase leg based on 10 kV SiC MOSFETs for modular MV converters. A baseline design and test of the phase leg is established first as the foundation of the research in this dissertation. Thorough evaluation of 10 kV SiC MOSFETs’ switching performance in a phase leg is necessary before applying them in MV converters. The impact of parasitic capacitors and the freewheeling diode is investigated to understand the switching performance more extensively and guide the converter design. One non-negligible challenge is the flashover fault resulting from the premature insulation breakdown, a short circuit fault with extremely fast transients. A device model is established to analyze the behavior of 10 kV SiC MOSFETs when the fault occurs in a phase leg thoroughly. Subsequently, the gate driver and protection design considerations are summarized to achieve lower short circuit current and overvoltage and ensure the survival of the MOSFET that in ON state when the fault happens. Furthermore, it is challenging to design the overcurrent/short circuit protection with fast response and strong noise immunity under fast switching transients for 10 kV SiC MOSFETs. The noise immunity of the desaturation (desat) protection is studied quantitatively to provide design guidelines for noise immunity enhancement. Then, the protection scheme based on desat protection is developed and validated withimmunity, the strong noise immunity of the developed protection is also successfully validated. In addition, a simple test scheme is proposed and validated experimentally, in order to qualify the HB phase leg based on the 10 kV SiC MOSFET comprehensively for the modular MV converter applications. The test scheme includes the ac-dc continuous test with two phase legs in series to create the testing condition similar to what is generated in a modular MV converter, especially the high dv/dt. The test scheme can fully test the capability of the phase leg to withstand high dv/dt and its resulting noise

HIGH VOLTAGE RESONANT SELF-TRACKING CURRENT-FED CONVERTER

High voltage power supply design presents unique requirements, combining safety, controllability, high performance, and high efficiencies. A new Resonant Self-Tracking Current-Fed Converter (RST-CFC) is investigated as a proof-of-concept of a high voltage power supply particularly for an X-ray system. These systems require fast voltage rise times and low ripple to yield a clear image. The proposed converter implements high-frequency resonance among discrete components and transformer parasitics to achieve high voltage gain, and the self-tracking nature ensures operation at maximum gain while power switches achieve zero-voltage switching across the full load range. This converter exhibits an inherent indefinite short-circuit capability. Theoretical results were obtained through simulations and verified by experimental results through a complete test configuration. Converter topology viability was confirmed through hardware testing and characterization