基于VSG的电网电压不平衡下并网逆变器控制策略

Control strategy of grid-connected inverter based on VSG under unbalanced grid voltage

当逆变器在电网电压不平衡的情况下工作时,传统的虚拟同步发电机(Virtual Synchronous Generator,VSG)控制方法无法抑制不平衡的并网电流,也无法减少有功、无功功率包含的振荡分量。文章提出了一种适用于VSG在不平衡电网电压下的改进型控制策略。改进后的策略基于交叉解耦复数滤波器(Double Complex Coefficient Filter,DCCF)的正负序分离,在dq旋转坐标系下根据瞬时功率理论计算出在平衡电流、恒定有功及无功3种目标下的电流指令值,实现电流和功率的协调控制,并可以灵活切换控制模式。通过搭建仿真系统,对改进的控制策略进行验证,仿真结果表明了控制策略的有效性和可行性。

When the inverter works in the case of unbalanced grid voltage,the traditional virtual synchronous generator(VSG)control method cannot suppress the unbalanced grid-connected current,nor can it reduce the oscillation component contained in active and reactive power.Therefore,an improved control strategy for VSG under unbalanced grid voltage is proposed.The improved strategy is based on the positive and negative sequence separation of the double complex coefficient filter(DCCF).According to the instantaneous power theory in the dq coordinate system,the three targets of balanced current,constant active power and reactive power are calculated.The current command value can realize power-current coordinated control according to different command values,and can switch the control mode flexibly.By building a simulation system,the improved control strategy is verified,and the simulation results show the effectiveness and feasibility of the control strategy.