The Research Of Maximum Power Point Tracking Control Algorithm In Photovoltaic Grid-connected System

With the development of society economy, energy need is becoming more and more, traditional fossil energy is facing depletion crisis and causes serious pollution when consumed. Energy conservation and environment protection have been necessary conditions for sustainable human development. Solar energy as one of renewable resources with the advantage of inexhaustible, unlimited, clean pollution-free has been paid great attention by government.For the moment, the main reason of photovoltaic grid-connected system not universal is low efficiency but high cost. In order to reduce system cost and advance utilization efficiency of solar energy, tracking maximum power point is one of the most efficient approaches. Up to now, the methods of maximum power point tracking are mostly constant voltage control, perturbation and observation, incremental conductance method, fuzzy control and etc.This paper combines single apex of solar cell output characteristic, applies loss-free resistor achieved by Buck-Boost in the maximum power point control system, proposes a new improved control way to make it more suitable for maximum power point tracking of solar cell. Through the verification of simulation, system with this method can track maximum power point of solar cell efficiently for each illumination intensity and rapid changing temperature. It can not only raises efficiency but also avoid unknown interference and misjudge of the traditional method.The main work of this paper is shown in detail as follows:Chapter 1 introduces the background, significance, work and innovation of the paper.Chapter 2 analysis the mechanism of solar cell, builds the model of solar cell and analysis detailed issues should be paid attention in the major component of photovoltaic grid-connected system.Chapter 3 Combines the nonlinear characteristic of solar cell , summarizes the already methods of maximum power point tracking and finds best access of loss-free resistor in maximum power point tracking.Chapter 4 builds iterative mapping equation of Buck-Boost converter, applies loss-free resistor achieved by Buck-Boost converter in maximum power point tracking control circuit, improves the already control method in order to advance the conversion efficiency of solar cell, analysis its principle detailed and gets validated by simulation.Chapter 5 summarizes the main points that this paper tries to achieve and points out the further study in future.