Series-Connected HV-IGBTs Using Active Voltage Balancing Control With Status Feedback Circuit

Transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in high-voltage and high-power converters. Asynchronous gate delay causes series-connected IGBTs not to turn-on and turn-off at the same time resulting in severely unbalanced voltage sharing. An active voltage balancing control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage sharing, the microcontroller generates a time delay for the gate driver to compensate the asynchronous gate delay. The most vital part of active voltage balancing control, the status feedback circuit, is also discussed in detail in this paper. The function of the status feedback circuit and the effect of active voltage balancing control are verified in a two series-connected HV-IGBTs platform in rated operation (5 kV bus voltage and 600 A load current).