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

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 grid-connected 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 grid-connected 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. © 2022, Electric Power Automation Equipment Press. All right reserved.