Design and simulation of quasi-Z-source grid-connected PV inverter with bidirectional power flow for battery storage management

In a small to medium scale PV inverter system, energy storage functionality such as battery is significant to ensure the obtained energy is efficiently stored, used and delivered to the load. As for the grid-connected system, having a bidirectional power flow in the system is an advantage in case the power from the PV array is insufficient to fulfill the demand from the load. The grid power can also be used to charge the battery storage in case the energy stored is at the critical level and cannot be recovered immediately due to low/zero level of sun irradiation. In relation to this, the quasi-Z-source inverter (qZSI) topology, apart from other well known advantages for DC-DC-AC conversion, offers a flexible ways on how the battery storage can be added to the system. In this paper a new way of connection and control method for battery storage is proposed which can be attach to the system easily with minimal modification. It also realizes a bidirectional charging capability from the grid where its use can be extended for example in vehicle charging station. Apart from that, the paper also study on use of PV emulator which can be an alternative to realize the PV source behavior. The system configuration and design is detailed and simulation results demonstrate the system works according to the requirement.