Zero-crossing distortion in grid-connected PV inverters

Zero-crossing distortion has been observed in the AC output current produced by some grid-connected PV inverters and this can cause a resonant response between the grid impedance 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.