Optimal charging of battery using solar pv in standalone dc system

In standalone dc system, dc-dc converter is used to interconnect solar photovoltaic (pv) and battery. To utilize solar pv to fullest, maximum power point tracking (MPPT) is incorporated in controller. However, in case when the state of charge (SoC) of battery is high and system is partially loaded, excess power flows into the battery, thereby reducing the life of battery. Technique suggested in literature use output (battery) voltage controllers. However, it is shown in this paper that output voltage controlled dc-dc converter fed by solar pv may lead to instability. To address these limitations, a charge controller scheme is proposed in this paper. This scheme ensures that the battery voltage remains below its gassing voltage. Salient features of the proposed scheme are optimal utilization of solar pv and battery capacities without effecting life of battery. The effectiveness of the scheme is verified through detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a scaled-down laboratory prototype developed for the purpose.