相继换相失败对基于相位角的失步解列判据的影响机理

高压直流输电系统在相继发生换相失败过程中,即使两侧系统并没有发生失步振荡,换流站附近交流线路上的电气量也会周期性变化,可能导致失步解列装置的不正确动作。以基于电压、电流间相位角的失步解列判据为例,研究了相继换相失败对判据的具体影响。首先,在PSCAD/EMTDC上搭建交直流混联系统仿真模型,分析了相继换相失败过程中交直流系统电气量变化特征,总结了逆变侧换流母线电压周期性变化特点;继而对交流线路上的电压、电流间的相位角轨迹进行时域解析计算,分析了相关电气量对相位角变化规律的影响特点,揭示了相继换相失败对基于相位角的失步解列判据的影响机理;最后,以算例验证了理论分析的正确性。

Mechanism Analysis of Successive Commutation Failures Influence on Out-of-step Splitting Criterion Based on Phase Angle

In the process of high voltage direct current transmission system successive commutation failures, even though no out-of-step oscillation has occurred, electrical quantities on AC lines nearby inverter station will still vary cyclically, which may lead to maloperation of the out-of-step splitting device. By taking the out-of-step splitting criterion based on the phase angle between voltage and current phasor as an example, the effect of successive commutation failures on the splitting criterion is studied. An AC/DC hybrid system simulation model is established on PSCAD/EMTDC, the electrical quantities variation characteristics on AC/DC system during successive commutation failures are analyzed and periodic variation features of inverter bus voltage are summarized. Then, the phase angle trajectories on AC lines during the process of successive commutation failures are calculated for time-domain analysis, the influence of the corresponding electrical quantities on phase angle trajectories features are analyzed and the mechanism of effect of successive commutation failures on the out-of-step splitting criterion is revealed. A numerical example is given to demonstrate the validity of the theoretical analysis. This work is supported by State Grid Corporation of China.