High-performance hybrid photovoltaic -battery system based on quasi-Z-source inverter: application in microgrids

This study presents a high-performance photovoltaic (PV)-battery hybrid power conversion system (HPCS) which is integrated to a microgrid using a quasi-Z-source inverter (qZSI). The battery system is directly connected to the intermediate dc link of the qZSI without any extra converter which reduces the size and the cost of the power electronic interface. A controller equipped with a harmonic compensator is designed to control the battery current in the grid-connected mode and to regulate the microgrid voltage in the islanded mode in the presence of unbalanced and non-linear loads. Furthermore, the proposed controller adjusts the shoot-through duty cycle of the qZSI to regulate the PV voltage to its reference value provided through the maximum power point tracking algorithm. Moreover, the proposed controller provides the microgrid with the capability to transfer between the two operation modes. A new strategy is adopted to keep the HPCS operational in case of severe reduction in the available power of the PV modules and its consequent voltage drop. The performance of the proposed control system is evaluated for the control of a typical microgrid simulated in MATLAB/SIMULINK environment.