A novel series switch module in high-voltage applications

Abstract The Tokamak power system requires a high-voltage fast switch because of safety and reliability concerns. This switch can cut off a high-voltage power supply within a short time (usually in microseconds) during faults and system tests. Insulated gate bipolar transistors (IGBTs) satisfy the fast-response requirement of the switch. Directly connecting multiple IGBTs in series is an essential procedure in high-voltage applications. However, voltage balance among IGBTs connected in series is very complex and difficult. No satisfactory method for addressing this issue is currently available. This paper presents a novel switch-circuit module that can operate easily as a modular-connecting high-voltage switch. The topology of the improved modular multilevel converter shows that the switch time is shorter and voltage adjustability is more advanced, respectively, than other switches. The module inhibits overvoltage when it is turned off, which occurs with increased voltage to a rated value by using a high-capacity capacitor. Two IGBTs in overvoltage module are turned on to balance the voltage when the switch is in conducting state. The operated mode increases the current-carrying capacity. A detailed analysis of the submodule is described in this paper. The test prototype is a 4 kV/50 A switch. Results show the excellent performance of the proposed submodule.