Control strategy for a standalone PV/battery hybrid system

A power management strategy for a standalone photovoltaic/battery hybrid system is investigated in this paper. A pair of DC-DC converters are used to interface a photovoltaic (PV) array and a lead-acid battery bank to a common DC-link. The presented control strategy manages the power flow between the converters and the load in order to maintain the power balance in the system and enable the battery to support the PV array when the available PV power is insufficient to meet the load. A multi-loop strategy is used to control the converters taking into account battery charge rate limits and state-of-charge constraints. The resulting control system is implemented without the need for discrete state or programmatic elements. One supplementary loop monitors the battery state-of-charge and the PV operating point is adjusted to avoid overcharge. Another loop ensures the system power balance when the battery is charging at its charging current limit. The controller design, analysis, and experimental validation results for a 2 kW prototype system under several operating scenarios are presented and discussed.