基于SiC MOSFET直流固态断路器关断初期电压尖峰抑制方法

摘要

For the transient overvoltage and oscillation phenomena in a solid-state DC circuit breaker based on silicon carbide metal oxide semiconductor field-effect transistor (SiC-MOSFET) caused by its high switching-off speed, a possible solution method was proposed in this paper. First, an equivalent circuit model for SiC MOSFET was established, and the impact of different stray inductances on the turn-off initial stage voltage waveforms of the DC circuit breaker was analyzed. And then, according to the difference in energy absorbed by metal oxygen varistors (MOVs) with different rated voltage levels, a voltage overshoot suppression method was presented, in which another MOV was used as a snubber circuit. Furthermore, on the basis of its operation principle and suppressive effects, a basic principle was presented on how to select the snubber MOV. Finally, an experimental platform of SiC MOSFET-based DC circuit breaker was established, switching off characteristics were analyzed and compared at different stray inductances and different solid-state devices. The experimental results show that the SiC MOSFET-based DC circuit breaker has relatively serious voltage overshoot and oscillation compared with Si IGBT-based breaker, which is more obvious with increasing stray inductance. And the feasibility of proposed method is also verified.%针对碳化硅金属氧化物场效应晶体管(SiC MOSFET)直流固态断路器关断速度快、关断初期易产生较大电压尖峰及振荡问题,提出一种抑制方法.首先,建立SiC MOSFET等效电路模型,分析其不同寄生电感对固态断路器关断初期电压波形的影响.其次,利用不同电压等级金属氧化物压敏电阻(MOV)吸收能量不同的思想,提出并联MOV作为缓冲电路来抑制断路器关断初期电压尖峰的方法,在分析其工作原理和抑制效果的基础上,提出了选择缓冲 MOV 额定电压的依据.最后,搭建了基于SiC MOSFET直流断路器实验平台,对不同寄生电感、不同器件下的开断特性进行了比较,并对所提方法的有效性进行了验证.结果表明,相比Si IGBT固态断路器,SiC MOSFET固态断路器具有更为严重的电压尖峰和振荡问题,且随着寄生电感的增加越来越严重,所提出的方法可有效抑制其电压尖峰并减弱振荡.