柔性直流对交流系统短路电流影响因素分析

Influence of VSC-HVDC on short-circuit current of AC system

交流系统短路后,柔性直流可等效为具有一定幅值和相位的电流源。文中基于受端电网发生故障时的柔性直流等效模型,分别对影响柔性直流等效电流源相位、幅值的相关因素进行了分析。柔性直流等效电流源的相位主要受故障类型影响,而幅值主要受控制方式、限幅环节以及电气距离影响,且不同情况的相互组合对交流系统短路电流的影响更加复杂。研究表明,对于交流侧三相短路故障,柔性直流对短路电流的影响共有馈入为零、馈入为有功控制环节限幅值、馈入为无功控制环节限幅值和馈入为无功控制环节参考值4种情况。最后通过基于PSCAD的仿真结果验证了相关分析的正确性。

After the AC system is short-circuited,voltage source converter-high voltage direct current(VSC-HVDC)can be equivalent to a current source with a certain amplitude and phase.In this paper,based on the equivalent model of VSC-HVDC when the receiving end grid fault occurs,the factors affecting the phase and amplitude of equivalent current source of VSC-HVDC are analyzed respectively.Studies show that the phase of the equivalent current source is mainly affected by the type of fault,and the amplitude is mainly affected by the control method,the amplitude limiter and the electrical distance.Because of the combination of different situations,the influence on the AC system short-circuit current is bceorning more complicated.The research results show that for AC side three-phase short-circuit fault,the influence of VSC-HVDC on short-circuit current can be divided into four situations,which contain zero feed in,limited amplitude of active control link,limited amplitude of reactive power control link and reference value of reactive power control link.The simulation results based on PSCAD software verify the relevant analysis.