Maximum Power Point Tracking Algorithm for a Grid Connected PV-Fuel Cell-Wind Hybrid System

This paper presents a method to operate a grid connected hybrid system. The hybrid system composed of a Photovoltaic (PV) array, Proton exchange membrane fuel cell (PEMFC) and wind energy is considered. Two operation modes, the unit -power control (UPC) mode and the feeder-flow control (FFC) mode, can be applied to the hybrid system. In the UPC mode, variations of load demand are compensated by the main grid because the hybrid source output is regulated to reference power. Renewable energy is currently widely used. One of these resources is solar energy. The photovoltaic (PV) array normally uses a maximum power point tracking (MPPT) technique to continuously deliver the highest power to the load when there are variations in irradiation and temperature. Other renewable sources are PEMFC and Wind mill installed in the hybrid system. By changing the FC output power and Wind power the hybrid source output becomes controllable. Therefore, the reference value of the hybrid source output must be determined. In the FFC mode, the feeder flow is regulated to a constant, the extra load demand is picked up by the hybrid source, and, hence, the feeder reference power must be known. The system can maximize the generated power when load is heavy and minimizes the load shedding area. When load is light, the UPC mode is selected and, thus, the hybrid source works more stably. The changes in operating mode only occur when the load demand is at the boundary of mode change; otherwise, the operating mode is either UPC mode or FFC mode. Besides, the variation of hybrid source reference power is eliminated by means of hysteresis. This operating strategy will minimize the number of operating mode changes, improve performance of the system operation, and enhance system stability.