Operation possibility of grid connected Quasi-Z-Source Inverter with energy storage and renewable energy generation in wide power range

In renewable energy generation systems, energy storage is needed not only for short-term smoothening of the electric supply, but also to supply power when there is no generation for a longer period of time. The Quasi-Z-Source Inverter (qZSI) enables the integration of energy storage easily in addition to the other energy source mainly used for output power smoothening. In this paper the possibility to integrate energy storage in qZSI structure is analyzed in case when the input voltage is low or when battery is the only source of energy. The operation limits of the converter and possible solutions to extend the operation range are analyzed theoretically and by means of simulations in PSIM software. Results show that low input voltage limits the operation range of energy stored qZSI; modified circuits that can be used to avoid these limitations are proposed.