The Research On Application Of Fuzzy Control To PV Charger System

The PV charger system uses solar cell which produce electricity directly from sunlight using silicon cells and transfer energy to batteries through special designed controller. Photovoltaic, electronic and control theories etc. are involved in the system. However, since the output power of a PV array varies according to the sunlight conditions, atmospheric conditions, including cloud cover, local surface reflectivity, and temperature and so on. Therefore, to maximize the efficiency of the renewable energy system, it is necessary to track the maximum power point (MPPT) of the input source all the time.Based on the characteristic of photovoltaic array, and by analyzing the characteristics of MPPT control methods now available, such as CVT, Perturbation and Observation (P&O), Incremental Conductance (IncCond) etc., a new maximum power point tracking method using fuzzy set theory is proposed to improve energy conversion efficiency. Fuzzy algorithm based on linguistic rules describing the operator's control strategy is applied to control step-down converter for MPPT. MPPT algorithm is implemented by 8-bit single chip MC68HC908JK3CP microcontroller. The new style battery charge control system with high efficiency designed in this paper has all kinds of protection measures completely, such as over- current protection, low-voltage and over-voltage protection, over-temperature protection and so on.The experimental results show that performance of fuzzy controller in maximum power tracking of photovoltaic array is better than that of controller based on other control methods.