Power electronic configuration for the operation of PV system in combined grid-connected and stand-alone modes

A simple photovoltaic (PV) system capable of operating in both grid-connected mode and stand-alone mode using multilevel boost converter (MBC) and line commutated inverter (LCI) has been developed for extracting the maximum power and feeding it to a single phase utility grid and stand-alone system simultaneously. Theoretical analysis of the proposed system is done and the duty ratio of the MBC is estimated for extracting maximum power from PV array. For a fixed firing angle of LCI, the proposed system is able to track the maximum power with the determined duty ratio which remains the same for all irradiations. This is the major advantage of the proposed system which eliminates the use of a separate maximum power point tracking (MPPT) controller. Experiments have been conducted on a 80 V, 9.4 A PV array feeding a 110 V single phase grid and a 230 V, 100 W DC motor. The MBC extracts maximum power from the PV array and feeds the major portion of power to the single phase utility grid via LCI and the remaining power to separately excited DC motor. It was found that the theoretical analysis, simulation and experimental results closely correlate with each other and proves the effectiveness of the proposed configuration.