Research on Control of Three-phase Grid-connection Inverter under Conditions of Voltage Distortion

In this paper, a direct grid current control strategy for grid-connected voltage source inverters with an LCL-filter is proposed. The direct grid current control is used to mitigate the grid voltage disturbance, then the characteristics of the inverter system with the proposed controller are investigated and compared with those using traditional control strategies. In the proposed control strategy, the use of the virtual resistance based on the capacitance current is able to realize active damping, and zero compensation is brought in to enhance the stability, and the quasi proportional-resonant (QPR) controller under two-phase static coordinate is designed to track the ac reference current. The strategy integrates the QPR controller with harmonic compensator (HC) to restrain the distortion of the grid voltage. Experimental results are provided to verify the new current control strategy.