特高压直流输电换流阀用晶闸管反向恢复特性研究与分析

Research and Analysis on Reverse Recovery Characteristics of Thyristor in Converter Valve of HVDC Power Transmission

为了掌握直流输电换流阀现场检测关键技术,搭建了晶闸管反向恢复特性实验电路,实验研究了正向电流幅值、换向电流变化率等参数对特高压换流阀用晶闸管反向恢复特性的影响。基于工频条件下晶闸管单元反向恢复特性研究结果,并结合特高压直流输电工程实际,从晶闸管器件物理特性的角度对上述影响的机制进行了分析。结果表明:反向恢复电荷随着正向电流、换向电流变化率的增大而增多,导致反向恢复时间增长、恢复电流峰值增大,从而引起反向恢复特性的改变;当换向电流变化率较小时,正向电流对反向恢复电荷量影响不大,反之亦然;反向恢复时间在某一正向电流幅值下发生跃变,而后随着正向电流的增大而缓慢增长。该研究可为换流阀晶闸管级单元现场检测试验提供可靠的理论依据。

In order to grasp the in - situ test technology of converter valve, the test circuit for reverse recovery characteristics of high - power thyristor is built. The effects of forward current amplitude and change rate of commutating current on reverse re- covery characteristics of high - power thyristors are studied experimentally. Based on the research results of reverse recovery characteristics of thyristor under power frequency condition, the mechanism of these effects is also analyzed as viewed from the physical characteristics of thyristor. The results show that the reverse recovery charge increases with the rise of peak current or commutating di/dt, which results in the increase of reverse recovery time and recovery current peak, and it would change the reverse recovery characteristics. And when the commutating di/dt becomes lower, the forward current has little effect on the reverse recovery charge, and vice versa. With the increase of forward current, the reverse recovery time changes sharply at a certain current, and then grows slowly. The research can provide a reliable theoretical support for the in - situ test of thyristor level of the converter valve.