The connection of high voltage insulated gate bipolar transistors(IGBTs)in series is a key issue in the high voltage and power self-commuted coverter application

such as the voltage source converter based high voltage direct current(VSC-HVDC)transmission

the HVDC circuit breaker and other high voltage and high power control equipments. The bottleneck for the operation of high power IGBTs connected in series is balancing their voltage. The mechanism of unbalanced voltage of IGBTs connected in series is analyzed. It is concluded that the key to implementing voltage balance is to solve the off state voltage unbalance and turn-off transient voltage unbalance. The gate level side voltage balance control technique could be a good solution. The gate driver design based on the active voltage control(AVC)technology and the time-delay compensation control strategy are discussed. Through the driving control of turn-off voltage waveform tracked in the active area and the time-delay compensation between the IGBT modules during turn-off transient

the voltage balancing of the devices connected in series is effectively realized. A pulse experimental platform with six 3 300 V/1 200 A IGBT modules directly connected in series and a three-phase converter valve based on this valve arm are set up to verify the two methods. The experimental results show that the practical value of the methods proposed is its beneficial effect on voltage balancing. This work is supported by Jiangsu Provincial Natural Science Foundation of China(No. BK20140118).