Zero-crossing distortion in grid-connected PV inverters

Zero-crossing distortion has been observed in the ac output current produced by some grid-connected photovoltaic inverters and this can cause a resonant response between the grid impedance and the inverter filter capacitor. In some cases, particularly with large numbers of parallel-connected inverters and with weak grids, the resonance can cause voltage distortion that may be large enough to disturb other nearby equipment. A number of commercially available inverters were tested to investigate the mechanisms of this distortion. A model was then developed to allow further simulations with different numbers of inverters and varying levels of distortion to be performed.