Study On Pv Array Model And MPPT Algorithm Of The Stand-alone Photovoltaic System

With the increasing demand of energy resources and decreasing reserves of thenon-renewable energy，exploiting alternative energy resources such as solar energy isextremely important. Photovoltaic power generation is one of the most significantsolutions. Recently，photovoltaic industry has been experiencing a rapid developmentand also arising a large number of problems at the same time.It’s a common phenomenon that PV system presents a poor photoelectricconversion efficiency which related to the environment factors such as irradiance andtemperature. When a PV system subjects to shaded conditions, it shows more complexoutput characteristics and becomes harder to be tracked to its maximum power point.Therefore, an accurate model of PV array is needed to analyze and simulate theinfluence of all sorts of factors. Meanwhile，the output power characteristic of PVarrays under partial shaded conditions appears multi-peaks and for the sake ofmaximum output power a novel MPPT algorithm is required to seek the one and onlyglobal MPP.Based on consulting a large number of relative literatures, this paper analyzed theresearch status of the PV power system. Then the structure and the operating principleof the components of the stand-alone PV power system were interpreted. After anin-depth analysis of the single cell circuit model，this paper introduced LambertW-Function to decouple the current and the voltage of the photovoltaic cells, whichderived explicit expression of the current about the voltage. Besides, with therelationship between the current and voltage, the model of the PV cell，PV module andPV array was proposed. It was analyzed and simulated that the output characteristics ofseries and parallel PV array on the non-uniform illumination and uneven temperaturedistribution conditions, as well as the PV array in any temperature and solar radiationlevels. The results showed that the influence of the distribution of illuminationintensity on the peaks of the power-voltage curve of the PV array. On the aspect ofMPPT，various kinds of MPPT algorithms were introduced and compared in this paper.With the purpose of improving the response speed and lessening the energy loss causedby perturbation, a modified P&O method was proposed in this paper. Given the partialshaded condition, a simple fast and easy-implementation global MPPT algorithm wasdeveloped. In conclusion, the integrated simulation model of the stand-alone PV powersystem was constructed in Matlab/Simulink environment. The next, using Simulinksimulated the PV array，MPPT controller，battery and the overall system with the ACload respectively. The correctness and effectiveness of the model and the algorithmwere verified by simulation results.