An improved method for controlling an EDLC-battery hybrid stand-alone photovoltaic power system

Stand-alone photovoltaic power systems are potential power sources for wireless and optical telecommunications equipment and solar home systems. For these systems to be practical, the batteries used to store the power must have a long lifetime. We have proposed a stand-alone photovoltaic power system that uses an electric double-layer capacitor (EDLC) with lead-acid batteries. This system reduces the number of battery charge-and-discharge cycles and maintains the optimal charging voltage by using EDLC discharge power. In this paper, we describe the system's circuit configuration, operation, and conversion efficiency analysis. An improved method is described for controlling the system. It increases the system's power-conversion efficiency by keeping the capacitor voltage high. Simulation of a 250 W photovoltaic system showed that it reduces the power conversion losses in the system by about 35%.