A 99.977% Efficient, 20 kV, 50 A, T-Type Modular Dc Circuit Breaker with SiC Based Full Bridge Modules

This paper elaborates the significant advantages of a T-Type Modular DC Circuit Breaker (T-Breaker) built with full-bridge silicon carbide (SiC) switching cells, accompanied by the presentation of a prototype rated at 20 kV, 50 A. The challenges in submodule design are overcome by incorporating a gate drive with high common-mode transient immunity and robust insulation capability, a PCB busbar designed for high conduction current and voltage insulation, and a compact thermal management system. The proposed functionalities of the full-bridge module based T-Breaker (FB T-Breaker) have been validated. The FB T-Breaker is capable of interrupting a 500 A current, whilst also exhibiting tolerance to control signal misalignment. The T-Breaker’s efficiency registers at 99.977% at 50 A rated current, and it achieves a power density of 60.2 MW/m³ at 250 A maximum continuous operating current.

I. Introduction

The merits of medium voltage direct current (MVDC) networks, including reduced power losses, cost-effectiveness, and enhanced power capacity, are becoming increasingly prominent given the rapid advancement of distributed energy resources, energy storage, microgrids, etc. [1]. Concurrently, technical challenges inherent in dc systems, such as swift fault detection and protection, power transient stability, and power quality improvement, continue to persist [2]. Solid-state circuit breakers (SSCBs) enable rapid fault detection and isolation, minimize arc formation, and eliminate wear and tear issues on mechanical parts. With the maturation of medium-voltage wide bandgap (WBG) devices, WBG-based solid-state circuit breakers (WBG-SSCBs) have emerged as promising solutions to these challenges in MVDC power systems. Owing to the characteristics of WBG devices, such as low on-state resistance, high switching speed, and smaller size compared to Si-based devices, WBG-SSCBs can achieve higher efficiency, faster fault response time, and greater power density compared with conventional SSCBs [3]. Furthermore, WBG-SSCBs can offer innovative integrated functionalities, including fault location [4], fault current limiting [2], and inrush current prevention during load start-up [5], thereby unlocking additional potential for WBG-SSCBs.