The Design of Charging Device in Stand-Alone Photovoltaic System

To improve utilization ratio of the stand-alone photovoltaic system, a strategy of four-stage charging control is put forward for VRLA batteries. Considering system performance, the choice of charge converter´s structures and characteristics of driving circuit is analyzed in this paper. Perturbation and observation method is adopted to implement maximum power point tracking (MPPT) of solar cells and switch charging algorithm automatically and accurately. Experimental results show that the system runs stably, implements four-stage charging according to different status of battery, which consequently could make full use of solar energy and increase system efficiency to 90.32%.