Snubber and Metal Oxide Varistor Optimization Design of Modular IGCT Switch for Overvoltage Suppression in Hybrid DC Circuit Breaker

The power electronic switches have great influences on the performance of the hybrid dc circuit breaker (DCCB). Recently, the integrated gate commutated thyristor (IGCT) is considered to be a suitable alternative full-control power device due to its high surge capability, high gate driver reliability, and low cost. Remarkably, high economic efficiency overvoltage suppression is important to the practical use of the IGCT switch. In this article, snubber and metal oxide varistor (MOV) optimization design for the purpose of reducing the passive components' cost is studied. Theoretical and mathematical analysis shows that the highest overvoltage precedes MOV's peak current. Then, the dynamic MOV model considering the response delay and steep front effect is built up. Next, an improved simulation circuit for calculating the highest overvoltage is established. The comparisons with experiment indicate the feasibility and accuracy of the simulation circuit. Based on the simulation results, the optimization design for overvoltage suppression is demonstrated and a cost performance promotion of 8.5% is obtained. Furthermore, the guidance of stray inductance for the structural design is also determined. In the end, a prototype for 10-kV DCCB is constructed and the tests of the IGCT switches verify the feasibility and validity of the overvoltage suppression design.