AC bus-voltage control method based on load impedance characteristics for single-phase grid-connected inverters

Aiming at the problem of the grid connected and off grid switching control of grid connected inverters, an ac bus-voltage control method based on load impedance characteristics is proposed for single-phase photovoltaic grid-connected inverters with batteries in this paper. The proposed control method includes a detection algorithm for the load impedance angle and an AC bus-voltage control algorithm. Thus, grid-connected inverters can output active and reactive current in proportion to the load impedance characteristics without a special reactive power calculation module to support the AC bus voltage. At the same time, the proposed control method can avoid the switching action of the control algorithm when the grid-connected inverter is switched from grid-connected mode to island mode. Finally, simulation and experimental results verify the effectiveness of the proposed method.