Research Of Equivalent Power Adaption MPPT Of Photovoltaic System

In response to the energy crisis and environmental pollution, photovoltaic powergeneration system has become research focus at home and abroad. In order to improve theenergy utilization rate, a fast tracking speed, high tracking precision, suitable for all kindsof environment of maximum power tracking technology has become the pursuit ofresearchers at home and abroad. From the perspective of establishing energy flowdynamic balance, a new maximum power point tracking method——the dynamicequivalent power adaption method(EPA) is extended out from the dynamic equivalentimpedance matching method(EIM).At first, the working principle of EPA is discussed. The meaning of power matchingdeviation and the feasibility of EPA are analyzed. Then the differences and relations ofEPA and EIM are briefly discussed. On this basis, the unique control characteristic ofEPA is analyzed in detail and the control algorithm flow chart of EPA is given.Secondly, after establishing the transfer function of Boost converter input voltage toduty ratio, according to the property of Laplace transformation, the transfer function ofdynamic equivalent external power increment to duty ratio is set up. Moreover, thevalidity of this transfer function is verified through simulation. On this basis, the PIparameter design progress is displayed in detail. After setting up the simulation model ofphotovoltaic cells, the tracking performance (mainly tracking velocity and trackingprecision) of EPA, perturbation and observation method(P&O), incremental conductancemethod(INC), and EIM are roundly compared in cases of starting track, light change, loadchange, light load, heavy load，along with the capacitive load. On the base of simulationcomparison, the advantages and disadvantages of EPA are summed up.Finally, making use of the designed Boost converter and four series of photovoltaiccells, the tracking experiments are done. The tracking performance of four MPPTalgorithms are compared in cases of starting tracking, load change and light changesuddenly. Through the experiments, the feasibility of EPA is verified. Meanwhile, theproposed EPA tracking method is a relatively ideal method and it improves the energy utilization rate of photovoltaic system.