Parameter design of voltage balancing circuit for series connected HV-IGBTs

Applying power semiconductor devices in series connection is a direct and effective scheme to improve the voltage rating and power rating of power electronic converter. The key issue of device series connection is voltage balancing in static switching state and dynamic switching state. Active clamping circuit samples overvoltage on insulated gate bipolar transistor (IGBT), injects current into the gate and thus could increase the gate voltage and suppress the overvoltage effectively. In this paper, a voltage balancing circuit for high voltage IGBT (HV-IGBT) series connection is presented. The voltage balancing circuit is composed of static state voltage balancing sub-circuit across collector and emitter, dynamic state voltage balancing sub-circuit across collector and emitter and active clamping sub-circuit across collector and gate. The functions and principles of the three sub-circuits are then described. Besides the topology, the parameters of the voltage balancing circuit influence the voltage balance of series connected HV-IGBTs seriously. Based on quantitatively analyzing the relationships among the parameters of HV-IGBTs, the parameters of voltage balancing circuit and the voltage balancing indexes of the series connected devices, a parameter design method for the presented voltage balancing circuit is proposed. This parameter design method comprehensively considers the switching loss of HV-IGBT, the loss of voltage balancing circuit, the electrical stress on HV-IGBT and the switching frequency in order to guarantee the efficiency, reliability and performance of the system. The proposed parameter design method is applied to the development process of a series connection circuit with Infineon 6500V/600A HV-IGBTs. Experimental results verify the validity and feasibility of the proposed method.