送端交流系统故障引发逆变侧换相失败机理分析及抑制策略

针对送端交流系统故障恢复期间引发逆变侧换相失败的问题，首先，基于交直流系统无功功率交互作用机理及关断角表达式深入剖析了逆变侧的运行特性，阐明了不同故障严重程度下直流电流上升速度与幅值变化规律，得出直流电流在轻微故障下过大的幅值及严重故障下过快的上升速度是导致换相失败的主要原因。其次，定量计算了不同故障严重程度下的整流器无功消耗量指令值，建立了整流器无功消耗量与直流电流、直流电压的数学关系，据此提出一种基于整流器无功功率控制的换相失败抑制策略。最后，基于PSCAD/EMTDC的仿真结果验证了理论分析的准确性以及所提抑制策略的有效性。

Mechanism analysis and prevention strategy of inverter side commutation failure causedby the sending end AC system

There is a problem of commutation failure (CF) at the inverter side caused by sending end AC system faults. First, based on the mechanism of reactive power interaction in AC-DC systems and the expression of extinction angle, the operational characteristics at the inverter side are analyzed in depth, and the variation laws of DC current rise speed and amplitude under different fault severity are clarified. It is concluded that the excessive amplitude of DC current in a slight fault and the excessive rise speed of DC current in a severe fault are the main reasons leading to CF. Secondly, the reactive power consumed by the rectifier order value with different fault severity is quantitatively calculated, the expression of DC current and voltage and the reactive power consumed by the rectifier is proposed. A CF prevention strategy based on rectifier reactive power control is proposed. Finally, the simulation results based on PSCAD/EMTDC verify the correctness of the mechanism and the effectiveness of the proposed prevention strategy.