Maximum Power Point Tracking Scheme For PV Systems Operating Under Partially Shaded Conditions

Energy and power are material basis and driving force of human social development. On the one hand the rapid development of the world economy and the continued growth of the world’s population making total demand for energy growing, On the other hand the total reserve of fossil fuel is dwindling, even in the crisis of exhausted. In addition, extensive use of fossil fuels has caused serious environmental problems. So the discovery and exploitation of green and renewable energy is significant. Photovoltaic power generation is an emerging technology, getting people’s attention with its own characteristics. In this paper, the research object is the photovoltaic power generation system, and the research objective is the maximum power point scheme for PV systems operating under PSC. Research results can be summarized in the following aspects.1) Build simulation models of photovoltaic cells and boost circuit by matlab, and then analysis the output characteristics of PV cells and PV arrays operating under PSC based on the model. All of this are preparing for MPPT algorithm design of PV systems operating under PSC. The peak point data of a PV cell has been measured under two different weather conditions during two day?. The data agree with the above simulation result well.2) Comparing has been made between four traditional MPPT methods, that is constant voltage method, P&O method, INC method, FLC method. During the analysis of the algorithm, different variable step control strategies have been proposed for the last three algorithms. Simulation and analysis have been made for these algorithms’control performance. A method of gain control rules of the fuzzy logic controllers based on artificial neural network and data achieved online has been proposed. Provide possibility for the online generation of the control rules of the fuzzy logic controllers.3) Under partially shadowed conditions, power-voltage (P-V) and current-voltage (I-V) characteristics of PV array characterized by multiple steps and peaks, making conventional maximum power point tracking (MPPT) algorithm based on uniform insolation ineffective. To solve this problem, this paper proposes a novel MPPT algorithm with global search capability. The operating point of the PV system will move to the vicinity of the real peak power point using an improved particle swarm optimization (PSO) algorithm at first stage, and converge on the real peak power point by the variable step incremental conductance method at the second stage. The new algorithm focuses on reducing system oscillation and speeding up the search process. Simulation results show that the proposed algorithm not only overcome the large oscillation problem caused by using random initialize particle position in PSO algorithm, but also inherited the fast tracking speed and stable capability of the conventional single peak optimization algorithm.4) The hardware circuit has been designed for small-scale PV power generation system. Boost circuit based on soft-switching technology will improve the conversion efficiency of the system.