An MPP Tracked SPV System Integrating Single-Stage Boost Inverter and Bi-directional Battery Charger

Commercial low-voltage solar photovoltaic (SPV) systems use front end DC-DC boost converters for voltage level boosting and this stage is followed by single/three phase inverters for generation of AC supply. This paper proposes a maximum power point tracked (MPPT) SPV system using a single-stage single-phase boost inverter replacing the two-stage power conversion of conventional SPV system and thus the active switch count and power conversion loss of the SPV system has been minimized. The proposed SPV system also uses a bidirectional DC-DC converter to charge/discharge a battery energy storage system (ESS). If the load power demand is less than the SPV power, then the battery ESS gets charged with the excess SPV power. Conversely, if the SPV power is less than the load power demand, the deficit power is supplied by the battery ESS. Thus, the proposed system can always track the MPP of the SPV source. In this work, operation of the boost inverter and the bidirectional dc-dc converter has been explained in detail along with the control strategy of the proposed system. Finally, the theoretical analysis has been validated by experimentation of a 500W laboratory scale hardware prototype. The boost inverter and the bidirectional charger are operated with a switching frequency of 10 kHz and 40 kHz respectively. All control functions are implemented with dsPIC30F4011 microcontroller. Real-time performance of the proposed SPV system has been found to match the predicted behaviour.