Research On PV System And Its MPPT Control Strategy

With the rapid development of the world economy and economic globalization process accelerateceaselessly, people's energy demand are increasing, energy shortages and environmental pollution problemhave become seriously, which restrict the sustainable development of human society. Looking for newenergy has become the urgent issue humanity is facing. At this time, people begin to pay close attention torenewable energy, hoping them can change the human energy structure and maintain long-term sustainabledevelopment. In these renewable energy, solar energy, because of its rich resources, light from the sundirectly to the earth and widely distributed radiation, renewable, clean enough, no pollution, maintenancemeasures, be internationally recognized as ideal alternative energy sources, has attracted worldwideattention, is one of the ideal alternative energy sources.One important field of solar energy application is photovoltaic power generation, its exploitationand utilization has been continuously development, which possess a good application prospect. In thephotovoltaic (pv) power system, one of the effective ways of improving the efficiency of the (pv) system isthrough the power electronic technology and control technology to realize the maximum power pointtracking (MPPT). Which have attracted a lot of attention all over the world at present. Therefore, Furtherstudy of photovoltaic (pv) power system, for relieving the energy crisis and protecting the environment andpromoting sustainable development, is of great theoretical and practical significance.The main content of this thesis is arranged as follows: First, this paper introduces the backgroundand significance about the photovoltaic (pv) power generation technology, the present situation and thedeveloping trends at home and abroad, the existing problems at present. And introduces principle andsorting methods of the photovoltaic (pv) grid-connected system, the equipments, and Building IntegratedPhotovoltaics(BIPV).Secondly, this paper gives a brief introduction of the classification of solar cell, and describes theoperating principle, current-voltage characters and the output power of solar cell. Solar cell is an importantcomponent of the (PV) system, and it usually works as photovoltaic arrays which are made of solar cells that in series, in parallel or parallel-series way. To obtain an optimum efficiency of a solar array, the solarcells need to have the same functional parameters, therefore, parameter extraction is necessary. Thetheoretical analysis and simulation study find that the series resistance makes the I-V characteristics curvemoves left while the shunt resistance makes it moves down. Based on this foundation, according to thecurrent equation, introduced a new method to estimate the Parameters. These all provides the theory basisto the practical application.Finally, this paper gives a detailed analysis about the maximum power point tracking (MPPT)control technology of the photovoltaic(PV)arrays, which is one of the key technology of the photovoltaic(PV)generation systems. After the analysis and comparison of several normal MPPT control method,based on the variable step size incremental conductance (INC) algorithm, a novel maximum power pointtracking(MPPT)algorithm is introduced, which can judge the step model is fixed or variable by extremepoints and adjust the step size by coefficient N automatically to track the maximum power point(MPP).Based on theoretical analysis, gives the system's hardware design, introduces the operating principle of theDC-DC conversion and the Boost circuit, and its simulation waveform, the operating principle of Sinewave of SPWM inverter waveform, and the main flow chart of the microcontroller output, last but not theleast, the algorithm is simulated in Matlab/Simulink. The results show that compared with the variablestep size incremental conductance (INC), the new algorithm can track MPP fast, reduce the systemoscillation at the MPP when insolation changing quickly, and improve the speed and accuracy of the PVsystem effectively, also achieve the anticipated goal.