DESIGN OF A NOVEL BATTERY VOLTAGE REGULATOR FOR PHOTOVOLTAIC SYSTEMS

The battery voltage regulator (BVR) circuit is designed to protect the battery against heavy discharge and overcharge conditions, thus prolonging the battery lifetime. Conventional BVRs are designed to disconnect the load from the battery when the battery state of charge (SOC) drops below a specified value so that heavy discharge is prevented. Alternatively, when the SOC exceeds a certain value, the photovoltaic (PV) array is disconnected from the battery to avoid overcharging (and consequent gas formation) of the battery. However, disconnection of the PV array when the battery is fully charged results in a loss of part of the available array power. The novel BVR described in this paper is designed to prevent such power loss from the PV array when the battery is fully charged. Instead of disconnection of the PV array, there is disconnection of the battery, and the load is directly connected to the PV array through a chopper circuit which ensures operation at maximum power or constant voltage according to load requirements. The importance of the novel BVR increases when the battery storage size is relatively small, and the frequency of disconnection of the PV array increases during the summer season. © 1990.