Study On Maximum Power Point Tracking Control Techniques In PV System

With the green and renewable energy be widely used, solar energy is accepted commonly because of its unusual advantages. But the output of photovoltaic(PV) array is influenced by the environmental factors, and PV array have relatively low conversion efficiency and is expensive. In order to reduce the overall system cost and extract the maximum possible solar energy, we should control the PV system effectively. This paper focuses on MPPT control techniques of PV array, analyses the theory particularly, establishes simulation model with MATLAB software, presents control strategies relevantly, and validated by experimental results.Firstly, this paper analyses the composing of the PV system. It is composed by PV array,power electronics converters,power storage system and loads. We can divide the PV system into two types: stand-alone PV system and grid-connected PV system by the relationship with the grid.Secondly, this paper analyses the electrical characteristics of PV cell and establishes simulation model, and also analyses commonly used MPPT methods, such as CVT method,Incremental Conductance method,P&O method. And then presents three improved methods: Open Circuit method,Optimal Gradient method,Three-Point Weight Comparison method. These methods each has his strong point and can be used in different field.Thirdly, for different PV system, we can use different control strategies. This paper analyses the characteristics of single-stage system and double-stage system, and then presents different MPPT control strategies. Simulation results show that both strategies are feasible.Finally, a hardware system is designed with double-stage to validate the feasibility of the control strategies. Experimental results show that the system can tract the maximum power point.