Research On Stand-alone Photovoltaic Power Systems

With the rapid development of economic,increase of population and progress of science and technology,more and more traditional energy will be on demand,which brings us a series of problems such as energy crisis and environment pollution.As a predominant energy,solar energy has been paid attention to and will be a potential one new energy.In order to improve property and achieve more credible running system,this paper has researched the structure,working principle and control strategy of stand-alone photovoltaic (PV) power system.Compared to grid system,it is more practical for solar energy exploiture of western region.Firstly,this paper discusses background of PV at home and abroad in detail,category, principle and output characteristics of PV cell.It mentions the composition of stand-alone PV system and running principle.The problems of we concern about such DC/DC convertor and the maximum power point tracking(MPPT) are discussed.Fused aforementioned technology,a 25W stand-alone PV system is designed.Next,a new adaptive voltage controlling scheme was proposed for MPPT,the coefficient of algorithm is different,the best algorithm based on the size of changed power is changeable. Compared to the traditional controlling algorithm of fixed step size simulation result under MATLAB,the result characteristics of high response speed,accurate and credible are achieved under the new MPPT controlling scheme.Finally,25W hardware circuit is built.From date of PV array under different installed angle,the best installation angle is obtained in Dalian.There is a lot of wok has been done during main circuit and peripheral circuits designed,including choice of PV array,parameter's design of Boost circuit,control circuit,drive circuit and detection circuit;as the energy storage device of stand-alone system,battery's charge and discharge circuit are designed.The charge current and voltage,discharge limited voltage and MPPT are analyzed at the same time by single chip dsPIC30F3011,the phenomenon of over charge and discharge is avoided efficiently and the stability of PV system is achieved.