Double Closed-Loop Control Strategy for Photovoltaic Inverter Based on Improved Average Current Control

Aiming at the resonance peak problem existing in the LCL type three-phase photovoltaic inverter grid-connected system, this paper proposes a dual current control method combining capacitive current feedback and average current control. By introducing the capacitive current feedback link in the weighted average current outer loop to form a double closed-loop control method to suppress the resonance peak problem of the LCL filter, so as to improve the grid-connected current quality. However, due to the fluctuation of the output power of new energy sources, the voltage outer loop is introduced on the basis of the double closed-loop current control strategy. The current inner loop is used to track the capacitor current and the weighted average value of the grid side current and the inverter side current, and the voltage outer loop is used to control the stability of the DC side input voltage of the inverter. The simulation results show that the harmonic distortion rate of grid-connected current is reduced from 4.37% to 0.78
^%
, which proves the correctness and effectiveness of the proposed method.