基于交流故障快速检测的高压直流换相失败抑制方法

A Method Based on Fast Fault Detection of Inverter-side AC System to Suppress the Commutation Failure in HVDC System

交流侧故障是高压直流输电系统发生换相失败的主要原因。不对称故障时,换相电压的相位偏移会引起实际触发角偏移,当实际触发角大于指令值时,很可能导致换相裕度不足而引发换相失败。首先计算了交流单相短路接地故障下的最大换相电压相位偏移量,提出了基于交流故障快速检测的高压直流换相失败抑制方法。该方法可以快速检测单相故障发生相,计算出锁相环输出相位与偏移量最大的换相电压相位之间的差值,并取最大相位误差量对锁相环输出的同步相位进行修正。在PSCAD/EMTDC中利用CIGREHVDC标准测试模型测试,结果表明所提的方法在逆变侧弱系统及强系统中均能有效提高发生单相故障后的后续换相失败抵御能力。

AC fault is the main reason for the commutation failure of DC system. In the case of asymmetric fault, the phase offset of commutation voltage will cause the actual firing angle offset. When the actual firing angle is larger than its order, it is likely that commutation failure occurs due to insufficient commutation margin. In this paper, the maximum commutation voltage phase offset under single-phase ground fault is calculated firstly, and a method based on fast AC fault detection to suppress the commutation failure in HVDC system is proposed. In this method, the phase of single-phase fault can be quickly determined, then the phase error between the output of PLL and the largest phase offset of commutation voltage is calculated, by which the synchronous phase of PLL is corrected. The CIGRE HVDC benchmark model is used to test in PSCAD/EMTDC. Simulation results show that the proposed method can effectively improve the resistance to subsequent commutation failure during single-phase faults in both weak and strong power systems.