Research On Photovoltaic Power Generation System And Its Maximum Power Tracking Control

Solar power is a kind of renewable energy with various features---environment-friendly, no noise, without production materials, and the application ofsolar energy has become a hot research topic in the field of new energy. Photovoltaicpower generation is one of the most important ways of human use of solar energy,and during the21st century, the global photovoltaic industry has developed rapidly.But it is a fact that the cost of solar cells is high and the utilization rate of that is low.To solve this problem, the especially important thing to do is to track the maximumpower point of solar cells.In the photovoltaic-power-generation system, solar cells can convert solar energyinto electric energy directly. The output characteristic of solar cells is affected by thelight intensity, environment temperature and load, being of obvious non-linearcharacteristic. When the external environment changes, the voltage and the outputpower will change. So, to improve the efficiency of photovoltaic-power-generationsystem, we should use maximum power tracking control technique and adjust theoperating point of photovoltaic cells real-timely to make it close to maximum powerpoint.Based on the photovoltaic power generation system KNT-SPV01, this paperanalyzes theoretically the principle and the structure of photovoltaic powergeneration system and studies the maximum power tracking control technique deeply.And the mini solar photovoltaic power generation systems with maximum powertracking controller is designed. There are four points as follows:Firstly, this paper studies the main characteristics parameters of the solar cell andachieves the output characteristic curve by real test in the external conditions, suchas different light intensity, temperature. It’s found that the output characteristic curveof solar cells is influenced by different external conditions and is nonlinear. It’sproved that it’s necessary and feasible to track the maximum power point. And thecharge and discharge protection circuit for the storage battery SFM250W is designed after analyzing the principle of solar cells, which will prolong the battery’s servicelife.Secondly, this paper introduces the working principles and equivalent circuits forthree kinds of DC/DC conversion circuit and compare the advantages anddisadvantages. According to the actual need, Buck-boost DC/DC conversion circuitis chosen to be the DC conversion circuit and the hardware circuit is designed totrack and control the maximum power point of solar battery.Thirdly, comparing some common maximum power point tracking algorithms,like incremental conductance method, actual measurement method and perturbationand observation method, this article analyzes their working principles, advantagesand disadvantages. On the basis of perturb and observe method, an improvedway--Variable-step Algorithm is designed, to avoid misjudging the maximum powerpoint and to improve the speed and accuracy of tracking and control.Fourthly, this paper designs a mini solar photovoltaic power generation systemand makes the hardware circuit of maximum power point tracking controller,achieving the maximum power point tracking control of solar cells. By thisexperiment, it’s proved that this system will improve response speed and trackingaccuracy effectively and will improve the work efficiency of solar photovoltaicpower generation system.