Research On Maximum Power Point Tracking Of Photovoltaic System

As a kind of green and renewable energy, Solar energy has a widelyapplication prospect. But output characteristics of photovoltaic battery aredeeply affected by external environment and conversion efficiency is verylow. It is an important research direction of photovoltaic system to improvethe output of solar battery based on existing photoelectric technologies.This thesis introduces the working principle, the electrical features andcharacteristics of the photovoltaic cells, analyses the influence factors of thephotovoltaic cells in detail. The influence factors include the batterymaterials, battery junction temperature, sunshine intensity, the seriesresistance and the load resistance. According to control theory of MaximumPower Point Tracking (MPPT) of photovoltaic array, disturbingself-optimization, optimizing model, intelligent and nonlinear controlprocessing methods and output control these four methods are summarizedand compared. Realizing principles, advantages and disadvantages of eachmethod is introduced in detail separately. Control algorithm of two newmaximum power point tracking methods which are combining constantvoltage method with incremental conductance and combining constantvoltage method with perturb-observe method are proposed. And improvedperturb-observe method is analyzed in detail.In this thesis, modular method is used to design the maximum powerpoint tracking control system. It discusses the determination of the circuitparameters and sets up two simulating model of photovoltaic cells, and thendynamic simulating model of a general photovoltaic array is mainlyintroduced. The model is built on the platform of MATLAB/SIUMLINKand it can be simulated with environment temperature, light intensity, seriesand parallel number and other parameters of photovoltaic array. Simulatingresults are analyzed, and these show that expected requirements of established model is meet well. Realizing strategies of MPPT control isproposed, photovoltaic system is divided into modules and simulating modelfor each modules is established. Different environmental conditions are setup for simulating and analyzing of the system. Moreover, a great deal ofsimulation results are provided to analyze traditional perturb-observemethod, improved perturb-observe method and incremental conductancemethod comparatively. The results show that the maximum power point canbe tracked exactly and quickly while MPPT module is added and energyloss because of the oscillation at the maximum power point is reduced, sothat energy conversion efficiency of photovoltaic system is improved.Moreover, proposed improved perturb-observe method can reduce powerloss which is produced because of erroneous judgments of traditionalperturb-observe method, and has certain advantages.