Dc power systems are better system solutions than ac power systems in application areas such as data centers, electric ships and dc micro... Show moreDc power systems are better system solutions than ac power systems in application areas such as data centers, electric ships and dc micro-grids. But the lack of fast and cost effective dc circuit breakers impedes the development and application of dc power systems. This thesis introduces a new type of self-powered dc solid state circuit breakers (SSCB) which are inactive during normal operation but can be triggered and powered up by a short circuit event. The design of a unidirectional solid state circuit breaker and a bidirectional solid state breaker are proposed. The solid state circuit breakers are consisted of normally-on SiC JFETs as main power switches and gate drivers featuring fast start-up forward-flyback converters. The operation principles of the circuit breakers are analyzed in details. Prototypes are built and verified in short circuit tests. The circuit breaker prototypes can interrupt short circuit currents up to 180 amperes at a dc bus voltage of 400 volts within 1 microsecond. Chapter 1 introduces the safety considerations of dc power systems, characteristics of conventional ac circuit breakers, and the development of solid state circuit breakers. Chapter 2 introduces the concepts of the proposed self-powered SSCBs and operation principle of a fast start-up forward-flyback converter. Chapter 3 introduces the schematic design of a unidirectional self-powered SSCB, its operation principle and experimental results. Chapter 4 introduces the schematic design of a bidirectional self-powered SSCB, its operation principle and experimental results. Chapter 5 concludes the thesis and looks forward to future work. M.S. in Electrical Engineering, July 2015 Show less
