电网不对称时直驱风电机组双电流环控制策略

Dual Current-loop Control Strategy for Converter of Directly-driven Wind Generation under Unbalanced Grid Conditions

推导了电网不平衡情况下直驱风电机组网侧变流器的电磁暂态模型,基于输出有功功率无波动,提出了正负序双电流环控制策略,分析了该策略下直流电压的稳态特性,并设计了可选择的前馈环节。正负序电量的检测通过正负序旋转坐标下分别滤波、瞬时值矩阵运算2种方法实现。仿真结果表明,该控制策略有效地抑制了网压不平衡情况下输出有功功率的二次谐波,避免了故障瞬间直流电压的升高,并且保证了三相电压、电流的高正弦度。

An electromagnetic transient model for network-side convertor of directly-driven wind generation under unbalanced grid condition is derived. Based on the assumption of no fluctuation of the output active-power, a dual current-loop control strategy is proposed, the steady-state characteristic of DC voltage under this strategy is analyzed and the optional feed-forward controller is designed. Two methods are used to calculate the dq voltages and currents under the frame of positive and negative sequence rotary coordinate system. One is to transfer the AC components to positive and negative sequence components and then delete the 100 Hz ripples, and the other is to calculate out their instantaneous value. The simulation results indicate that the proposed control strategy could effectively reduce the 100 Hz ripples in the output active power and the instantaneous rise of DC voltage and it does not bring ripples to AC voltages and currents.