Controller Design of Paralleled Quasi-Z-Source Inverters with Battery for Application in Grid-Connected Photovoltaic Power Generation System

In this paper, a new control method for the paralleled quasi-Z-source inverters (qZSI) with a battery for application in grid-connected photovoltaic (PV) power generation systems is proposed. The use of paralleled inverters in distributed generation (DG) applications has several advantages, such as high degree of redundancy, ease of maintenance and high reliability. By introducing the shoot-through states in the permissible switching states of the inverter bridge, the qZSI can boost/buck the output voltage of PV panel in a wide range. Also, the energy storage system, which is assisted with quasi Z-source network, provides the full use possibility of PV power. The proposed control method can manage the battery power, extract the maximum power from the PV panel, control the inverters output power with desired power factor and maintain the balance of power injected by the paralleled inverters into the grid, simultaneously. Also, the controller system is able to suppress both types of circulating-current, including cross and zero-sequence circulating-currents through a modification of the conventional control schemes. The ability of the proposed PV system is investigated by simulation results carried out using MATLAB/Simulink.