苏州同里±10 kV柔性直流配电系统直流故障特性研究

Grounding fault on DC side of Suzhou Tongli±10 kV flexible DC distribution system

基于苏州同里±10 kV直流配电系统参数,针对直流单极接地和极间短路故障暂态特性进行了研究。采用示范工程系统结构及控制策略,利用PSCAD建立了电磁暂态模型,针对系统交流侧、换流器侧、直流侧和负荷侧进行了故障过电压、过电流研究,分析了接地电阻对直流侧电压和电流的影响。结果表明:系统直流侧发生单极接地故障时,交流侧出现持续直流分量,换流器不闭锁,DC-DC变换器高压侧电容放电;故障接地电阻对直流侧电压、电流影响大;极间短路故障产生严重过电流,将触发换流器过电流保护,导致换流器闭锁;故障电流是产生过电压的重要原因;电感元件两端过电压较大,极间故障对系统交流侧影响较小。

Based on the parameters of the±10 kV DC distribution system in Tongli,Suzhou,the transient characteristics of DC unipolar grounding and inter-electrode short-circuit faults are studied.Using the system structure and control strategy of the demonstration project,the electromagnetic transient model is established in the environment of PSCAD.Many fault cases are considered in our work,including the AC side,the converter side,the DC side,as well as the load side.The overvoltage and overcurrent of the system are discussed.Furthermore,the impact of grounding fault resistance on the transients on the DC side of system is quantitatively studied.The simulation results indicate that there is a continuous DC component on the AC side in the case of single pole to ground fault on DC distribution system.The converter is not blocked,and the DC-DC converter high-voltage side capacitor is discharged.The grounding resistance of fault has a significant effect on the voltage and current transients of DC side.The pole-to-pole ground fault produces a severe overcurrent,which triggers the converter overcurrent protection,which triggers the converter overcurrent protection.The fault current is an important cause of the overvoltage.The overvoltage at both ends of the inductive element is large,which has little impact on the AC side of the system.