三相电压不对称时VSC-HVDC系统的控制策略

在三相电压不对称的情况下,电压源换流器(Voltage Source Converter,VSC)的传输功率会发生波动,从而影响高压直流系统的稳定运行.作者根据瞬时功率理论推导出了消除VSC传输功率波动需要满足的正、负序输出电压间的关系式.并通过坐标变换简化了VSC的功率传输方程,还采用不对称触发策略设计了VSC的传输功率控制系统.仿真结果表明,所设计的三相电压不对称条件下的控制系统具有良好的控制品质,有效地消除了有功功率的波动,并实现了有功、无功功率的独立调节.

CONTROL STRATEGY FOR VSC-HVDC SYSTEM UNDER UNSYMMETRY OF THREE PHASE VOLTAGE

The transmitted power of Voltage Source Converter (VSC) will fluctuate under unsymmetry of three phase voltage,which affects the operation of VSC-HVDC system. According to the theory of instantaneous power, the relational expression of the relation between positive sequence voltage and negative sequence voltage, which should be satisfied in order to eliminate the transmitted power of VSC, is deduced. The power transmission equation of VSC is simplified by coordinate transformation, and the control system for transmitted power of VSC is designed by use of unsymmetrical triggering method. Simulation shows that under unsymmetry of three phase voltage the designed control system possesses good control result, the fluctuation of active power is effectively eliminated and the individual regulation of active and reactive power is realized.