Harmonic current suppression of grid-connected PV power plant LCL filter based on PR control strategy

The repetitive control technique based on the internal model principle, can achieve low steady-state tracking error and total harmonic distortion in AC systems, so it is widely adopted in the inverter systems. The new PR current control strategy is developed and implemented to a grid-connected three-phase inverter with LC filter. The controller resulted in a low current total harmonics distortion (THD) of 3% to meet the grid requirement. Proportion-integral values above which can achieved output controller and proportion resonant controller are adopted to control the power adjustment and zero error control of harmonic restrain. The result of the simulation shows that the improved inverter control system can effectively control the grid current waveform which tends to sine wave. The detail design of the proposed controller is presented.