Improved Single Current Loop Control of Grid-Connected PV for Harmonic Reduction in Distribution Network

This paper proposes an improved single current loop multiple quasi-proportional resonant (QPR) control strategy based on the traditional proportional resonant (PR) control strategy to address issues of system instability and high harmonic content in grid-connected current caused by the LCL filter at specific frequencies. The sliding mode controller (SMC) is employed in the voltage outer loop, while active damping single current loop feedback is used in the current loop to suppress the resonant peak. Additionally, the multiple QPR controller minimizes harmonic content and enhances power quality. The MATLAB/Simulink program is utilized to study the grid-connected three-phase photovoltaic (PV) system's anti-interference capabilities and the harmonic content of the grid-connected current. The results demonstrate that the proposed method enhances the system's anti-interference capability and significantly reduces the harmonic content of the grid-connected current.