A control strategy for harmonic suppression in LCL photovoltaic inverter based on QPR controller and grid voltage feed-forward

Aiming at the problem of grid voltage harmonics interfering with grid-connected current when LCL PV (photovoltaic) inverters are integrated into the grid, this investigation provides a control strategy that utilizes a quasi-proportional resonance (QPR) controller along with grid voltage feedforward. The system model of the LCL PV inverter is developed and the limits of the LCL filter are investigated. The current inner loop suppresses the resonance spikes produced by the LCL filter and enhances stability using capacitive current-weighted feedback. In the current outer loop design, the control performance of different controllers is analyzed and compared, and QPR controllers have been designed to enable differential-free tracking of the reference current. A feed-forward loop of grid voltage compensates for the distortion of grid-connected current. The proposed control strategy has a good control effect and also reflects certain robustness and practicality. A simulation experiment platform was developed in MATLAB to confirm the theoretical analysis and assess the effectiveness of the control method.