Research on control strategy for PV inverter under unbalanced power grid

To enhance the operation performance of the PV inverter under unbalanced grid voltage, this paper proposes a control strategy, which is based on negative sequence voltage feedforward, to make the grid-connected current of the inverter balanced and sinusoidal. Firstly, to separate the positive and negative sequence voltage quickly and accurately, the paper proposes a scheme based on the Second Order Generalized Integrator (SOGI) and the experimental results validate the effectiveness of the proposed method. Secondly, to reject the negative sequence current component, a control strategy based on negative sequence voltage feedforward is designed in this paper. Finally, the proposed control strategy, which is validated effectively, is simulated and analyzed by PSCAD simulation software.