High Performance Current Control Strategy for Grid-Connected Boost DC-AC Inverter

The boost inverter can be an alternative grid interfacing power converter for renewable energy sources since it can generate an AC voltage whose peak value could be greater than the DC voltage. When it connects to the grid, high quality output current is required, therefore, grid current is hoped to be controlled directly. A novel control strategy to control grid current with only one closed control loop is proposed in this paper, where identical control structure is employed for its two DC/DC boost converters. In this way, the harmonic components of two capacitor voltages can be controlled into almost the same, therefore, they can be cancelled out in the output voltage, which will lead to very low distortion of grid current. To find out the resonance that may be generated in the grid-connected condition, an equivalent model in the AC side of boost inverter is presented. Furthermore, an inductor-current feedback is designed to damp the resonance based on the LCLCL equivalent model, which helps to improve the stability of control system. Moreover, DC input current ripple is suppressed by introducing the common harmonic compensation components. Compared with the existing control strategies, the proposed method can be easily implemented and achieve both high quality of grid current and DC current. Comprehensive experimental results are presented to validate the effectiveness of the proposed control strategy.