A Grid Current Single-loop Control Strategy of PV Inverter With LCL Filter

LCL filter for smoothing grid current of photovoltaic(PV) grid-connected inverter is better than simple L filter. However,there is possible instability of the LCL filter system caused by the zero impedance at the resonance frequency. A grid current single-loop control strategy without extra sensors and passive damping elements is proposed to realize the stable control of system by utilizing delay in digital control process.The design method of delay is suggested to achieve good performance of grid current harmonics and dynamic response.The effectiveness of the control strategy is verified by experimental results.