中文摘要：

在IGBT构成的变流器主电路中常采用并联缓冲电容的缓冲电路来抑制开关管关断过程中引起的过大电压冲击,保护IGBT和变流器.基于IGBT的动态模型,从理论上分析了缓冲电容对IGBT关断时产生的电压冲击规律,比较了不同缓冲电容对IGBT关断时的电压冲击情况及负面影响,得出缓冲电容在降低IGBT关断过冲电压的同时也会引起母线上电流电压振荡的结论.给出了IGBT关断时由缓冲电容引起振荡的仿真和实验结果,并指出了减小缓冲电容的方法.

英文摘要：

Snubber capacitance is usually parallel connected to switches in power converters made up of IGBT to suppress voltage overshoot during the process of turn-off so as to protect the IGBT and converters.Based on a dynamic model of IGBT,the paper theoretically analyzed the impact law of snubber capacitance on turn-off voltage.Then the voltage-overshoot results with two different snubber capacitances were compared in detail.As a conclusion,the snubber capacitance can reduce the turn-off voltage of IGBT and produce the voltage-current oscillation in a DC-bus as well.Some simulation and experimental results reflecting voltage-oscillation caused by snubber capacitance during the turn-off process of IGBT were shown.At last one method to cancel or decries snubber capacitance was proposed.