SPV Power Optimization Using Half Bridge Inverter and Voltage Multiplier

TLDR: A circuit topology working on differential power processing (DPP) concept has been analysed and an equalizer circuit which injects extra current in parallel with the shaded modules is employed.

Abstract: In a high power, grid connected photovoltaic (PV) array system a large number of PV modules need to be connected in series and parallel to get the required power level and dc bus voltage of around 700 – 760 V. Commercially available PV modules are provided with bypass diodes across each string of about 20-cells in, say, a 60-cells module. Among the series connected modules, some may get partially shaded mainly because of dust particles, clouds, bird droppings etc. The partially shaded module(s) or string(s) may get bypassed through the bypass diode(s), especially at higher output current. This may also cause multiple power peaks and may pose difficulty for the maximum power point tracking (MPPT) algorithm. As a result the overall power yield of the PV array may reduce. In this paper a circuit topology working on differential power processing (DPP) concept has been analysed. This topology employs an equalizer circuit which injects extra current in parallel with the shaded modules. This allows the series connected modules to operate at their individual maximum power points and the PV string sees a single peak in the power versus voltage curve. The present equalizer circuit topology has some additional advantages over various other equalizer topology reported in literature. Equalizer modeling equations in different modes of operation are reproduced and working of converter circuit is described based on derived dc equivalent circuit. The transformer turn ratio effect of the implemented converter topology is analyzed and discussed. Matlab simulation and experimental results show the efficacy of the employed converter.