Breaking Current Balance Enhancement for Parallel IGBT Modules in DC Circuit Breaker

Limited by the turn- OFF ability of single power module, parallel connection of insulated-gate bipolar transistors (IGBTs) is essential to enable breaking ability of current in the order of tens of kA. To realize high utilization rate of parallel power modules with turn- OFF inconsistency in dc circuit breaker, breaking current balance enhancement method is proposed in this article. There are two main contributions. First, by addressing transient switching behavior of parallel IGBT modules with centralizedand decentralized-snubber circuit (C-SC, D-SC) which consists of RC and metal oxide varistor (mov), It is revealed D-SC exhibits superior switching performance than C-SC for the first time, especially in terms of breaking current balance and voltage overshoot suppression. Second, as breaking current imbalance is generated by the turn-OFF inconsistency of parallel IGBTs with D-SC, the imbalance current can be calculated by turn- OFF time difference, parasitic inductance and residual voltage of mov, and increasing parasitic inductance is a practical way to suppress this imbalance current. Theoretical analysis based on the circuit modeling and current commutation process elaborates the findings, which are then confirmed by simulation and experimental results.