Voltage Balancing Circuit for Series-connected IGBTs Based on Multi-level Clamp Topology and Gate Drive Signal Adjustment

The top priority in guaranteeing the operation safety and reliability of a series-connected IGBTs-based system is to balance the collector-to-emitter voltage of individual IGBT when turned-off. Based on the multi-level voltage clamp topology, this paper proposed a novel voltage balancing circuit which takes effect on both load and gate sides simultaneously. It is achieved by phase-by-phase suppressing the collector-to- emitter voltage build-up rate of the firstly-turned-off IGBT. Furthermore, the dynamic and static voltage discrepancy was minimized by employing the static voltage balancing and voltage state feedback sub-circuit. The microcontroller is able to adjust the turn-off time of the IGBTs in real-time according to the feedback signals of the IGBTs' collector-to-emitter voltage states captured and sent by this sub-circuit. The circuit's topology, operating principle, and design procedure were given. Experimental results validate the proposed circuit and its control strategy exhibit an effective enhancement to the voltage consistency among series-connected IGBTs without decelerating the turned-off speed. © 2020 Chin. Soc. for Elec. Eng.