电网电压畸变下的级联H桥光伏并网逆变器谐波抑制控制策略

Harmonic suppression control strategy of cascaded H-bridge grid-connected photovoltaic inverter under grid voltage distortion

三次谐波补偿策略可有效解决单相级联H桥光伏并网逆变器的功率不平衡问题,但在电网电压畸变下易发生并网电流畸变。针对这一问题,提出一种电流谐波抑制环来消除电网电压畸变所带来的影响,并降低电网电流畸变率。分析了电网电压畸变导致电流畸变的机理原因,在此基础上,提出了将并网电流中的谐波成分作为控制对象,实时反馈至系统中,通过闭环控制实现对电流谐波成分的抑制。该电流谐波抑制环不改变原有的控制策略,只是作为额外的补充环节。仿真和实验结果表明,所提控制策略可大幅降低逆变器在电网电压畸变时的电流畸变率,证明了该控制策略的有效性和可行性。

The third harmonic compensation strategy can effectively solve the power imbalance problem of single-phase cascaded H-bridge grid-connected photovoltaic inverter,but it is prone to contributing to gridconnected current distortion under grid voltage distortion.To solve this problem,a current harmonic suppression loop is proposed to eliminate the effects of grid voltage distortion and reduce the distortion rate of gridconnected current.The mechanism of current distortion caused by the grid voltage distortion is analyzed.On this basis,it is proposed that the harmonic components of grid-connected current are taken as the control objects and fed back to the system in real time.The current harmonic components can be suppressed by closed-loop control.The current harmonic suppression loop does not need to change the original control strategy,but only serves as an additional supplementary link.Simulative and experimental results show that the proposed control strategy can greatly reduce the current distortion rate of the inverter when the grid voltage is distorted,which proves the effectiveness and feasibility of the control strategy.