Development and Application of the Light Triggered Emitter Turn-Off (LT-ETO) Thyristor

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Title: Development and Application of the Light Triggered Emitter Turn-Off (LT-ETO) Thyristor
Author: Chen, Bin
Advisors: Donald Warsing, Committee Member
John J. Grainger, Committee Member
Subhashish Bhattacharya, Committee Member
Mesut E. Baran, Committee Member
Alex Q. Huang, Committee Chair
Abstract: The performance of a power semiconductor device greatly determines the possible advancements of power electronics systems in regard to efficiency, volume, reliability, cost, cooling method, and even circuit topology. An advanced high power semiconductor device, the Emitter Turn-Off (ETO) thyristor, has been demonstrated to improve the performance of silicon thyristor-based high power devices. The Light Triggered Emitter Turn-Off (LT-ETO) thyristor was subsequently developed, which resulted in an optically controlled power device with excellent static and dynamic performance and expanded functionality through integrated sensors. This dissertation analyzes the design and verifies the performance of the LT-ETO. Conventional high power semiconductor devices require dedicated external power supplies with isolation capability. In contrast, the LT-ETO power switch is optically controlled, a capability not currently available in other commercial high power switches. Optical control greatly simplifies high power converter construction and lowers the overall cost of the system. The developed LT-ETO has been verified in converter circuits. If used in a pulse width modulation (PWM) voltage source converter (VSC), there is no minimum PWM carrier frequency or load current limitation for the LT-ETO if the VSC modulation frequency is greater than several Hz. The LT-ETO-based solid-state circuit breaker (SSCB) and solid-state fault current limiter (SSFCL)—which benefit greatly from the LT-ETO's high current interruption capability—optical control interface, and built-in sensors, are proposed. Comprehensive investigation of the LT-ETO as an AC switch is part of this research. A discussion of innovative methods to achieve complete sensor integration in the LT-ETO is also included in this research. The voltage, current, and temperature sensors are integrated in the device itself for the first time, another capability not currently available in other commercial high power switches. Conventional converters rely on expensive external sensors to gather the voltage, current, and temperature information; but the LT-ETO converter can utilize built-in sensors for protection and close-loop control. The experimental results show that the built-in sensors are very precise and the protection functions can effectively protect the LT-ETO and the converter in a timely manner. Through modeling and analysis, methods to improve the series operation of the LT-ETO are also proposed. Firstly, the static voltage balance is analyzed, and then a compensated gate driver is proposed to improve the dynamic voltage balance. Experimental results demonstrate excellent dynamic voltage balance of the LT-ETO in series operation using only a very small RC snubber. Finally, an active control gate driver method is proposed to automatically achieve dynamic voltage balance by utilizing the LT-ETO's built-in voltage sensor.
Date: 2008-05-06
Degree: PhD
Discipline: Electrical Engineering

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