交直流混联电网突变量选相元件动作性能分析

Performance Analysis of Phase Selector Device Based on Fault Component in AC-DC Hybrid Power Grid

交直流混联电网受端交流系统发生故障时,其背侧系统正、负序等值阻抗不再近似相等,从而对现有继电保护产生不利影响。文中分析了交直流混联电网受端输电线路相电流差突变量选相元件的动作性能,指出现有相电流差突变量选相元件应用于交直流混联电网时,在单相接地故障情况下由于逆变侧系统正、负序阻抗相差较大,从而引起各侧正、负序电流分配系数不再相等,出现明显的非故障相电流差突变量,引起选相元件误动作。以实时数字仿真器(RTDS)试验数据验证了理论分析的正确性。

When faults occur at the receiving terminal of AC system in AC-DC hybrid power grid,the positive sequence equivalent impedance at the back side is no longer approximately equal to that of the negative sequence,which will bring about adverse influence on existing protection.The operating performance of phase selector device with fault component（PSDFC） at receiving terminal of AC system is discussed in detail.It shows that the difference between positive and negative sequence impedance at inverter side is very evident when PSDFC is used for single phase earthing fault arising in AC-DC hybrid power grid.So the positive sequence current distribution coefficient at both sides is no longer equal to that of negative sequence.As a result,significant fault component difference between the non-fault phases arises and it can lead to the mal-operation of PSDFC.Finally,the correctness of theoretical analysis is verified by experiment data of the real-time digital simulator（RTDS） simulation.