An Investigation of Snubber and Protection Circuits Connections for Power-Electronic Switch in Hybrid DC Circuit Breaker

Hybrid DC circuit breaker (HDCCB) which relies on power electronic switches (PE switch) to achieve current breaking is a suitable candidate for DC power system fault current removal. Power electronic switch, as the key component, must provide the capability of high surge current, high turn-off current and enough overvoltage establishment. Thus, suitable snubber and protection circuits are indispensable for PE switch in DC current breaking. However, the connection types of these circuits are various and it is hard to determine the characteristics and benefits of each type. This paper investigates the different connection types of snubber and protection circuits for PE switch in hybrid DC circuit breakers. First, the topologies, working principles and current paths of three types of circuit connections are introduced and analyzed. Next, the corresponding overvoltage suppression performance are analyzed and tested comparatively. Test results show that the nearest position to MOV is the most beneficial to overvoltage suppression. Then, the phenomenon of voltage oscillation across the PE switch is analyzed. We can conclude that equivalent junction capacitors are the causes for voltage oscillation. Finally, the selection preference of connection types of snubber and protection circuits for PE switch in HDCCB for practical use is given.