不平衡工况下星形链式STATCOM的控制策略及其能力分析

Control Strategies and Capability Analysis of Cascaded STATCOM with Star Configuration Under Unbalanced Condition

星形链式STATCOM广泛应用于高压大功率场合的电能质量治理。实际上,三相负载不可能完全平衡,STATCOM在治理无功的同时应尽其能力同时补偿负载三相不平衡。根据负载电流计算出STATCOM同时补偿无功、三相负载不平衡时的指令电流。给出STATCOM与电网连接的等效电路,根据每相链节吸收的有功功率为零计算出STATCOM的中性点电压,设计了电流跟踪控制策略、直流侧电压稳定与均衡控制策略。为避免出现过调制现象,分析了STATCOM补偿三相负载不平衡能力。在Matlab/Simulink中搭建了1.5 Mvar、2kV、七电平STATCOM仿真模型,通过不同的负载情况验证了STATCOM能够补偿的最大负载不平衡度以及STATCOM控制策略的正确性。

The cascaded STATCOM with star configuration is used widely in power quality control at high voltage and high power applications.In fact,the three phase load cannot be fully balanced.The STATCOM shall,while in the course of controlling reactive power,shall try is capability to compensate three-phase load unbalance simultaneously.The instruction current for compensating reactive power and three-phase un-balance is calculated simultaneously in accordance with the load current.The equivalent circuit of the STATCOM and grid connection is given.The neutral point voltage of the STATCOM is calculated based on the principle that the active power absorbed by each cluster should be zero.The current tracking and DC volt-age stabilization and balance control strategies are designed.The capability for the STATCOM to compensate threephaseunbalanceisanalyzedincaseofover-modulation.A1.5Mvar,2kV,seven-levelSTATCOM sim-ulation model is built in Matlab/Simulink.The maximum load unbalance to be compensated by the STATCOM and the correctness of the control strategy of the STATCOM are verified through different load conditions.