Research And Design Of Stand-alone Solar Semiconductor Illuminating System

Photovoltaic power, which is a new clean and environment-friendly energy, is applied to practice widely in recent years. And it will gradually be one of the basic energy for human being. As a new generation of electric lighting source, white LEDs are entering to general illuminating area with the increase of luminous efficiency. In this paper, we mainly focus on photovoltaic power and white LED illumination, and demonstrate the design of stand-alone solar semiconductor illuminating system.The output P-V characteristic of solar array is single-peaked, and it has only one Maximum Power Point (MPP) at different temperature and irradiation. In order to increase the utilization ratio of solar array, a Maximum Power Point Tracking (MPPT) method should be taken to maximize its output power at any temperature and irradiation. An improved Incremental Conductance method which disturbs the output voltage with different step-length on the two sides of MPP is put forward. Then, the MPPT algorithm could increase the tracking velocity and decrease the oscillation amplitude around the MPP.The charging and discharging control of battery affects its operating life significantly. In this paper, we put forward a two-step charging strategy which consists of MPPT charging and constant voltage charging, and design a measuring circuit with DS18B20 to compensate the threshold voltage during the charging and discharging procedure. After analyzing the characteristic of power LED, we design a driving circuit based on HV9910 for LED lamp to meet its requirement.Finally, we design a controller for the illuminating system according to the characteristic of the whole system and make-up several LED lamps. Then we construct a stand-alone solar semiconductor illuminating system and test some parameters of it.