Research on control strategy of grid-connected inverter under unbalanced voltage conditions

In the case of unbalanced power grid, the grid-connected inverter with traditional control strategies will produce a large amount of harmonics at both the dc side and ac side, and then lead to fluctuations in power and performance deterioration. Therefore, more effective control is needed to improve the capability and functionality of grid-connected inverter interfaced distribute generator (IIDG). To overcome the problem, this paper analyzes the impacts of different control objectives on the inverter output power and grid current, presents a unified reference current vector expression, and proposes a control method that combines the dual current control loop for positive and negative sequence and linear reactive power control. The control strategy can effectively adjust the voltage at the point of common coupling, reduce the imbalance of the system, and the ability of the inverter is enhanced. The simulation results validated the effectiveness of the proposed method.