Design And Research Of The Inverters In A Small Scale Off-Grid Photovoltaic Power System

With the development of human society and the progress of industry, human beings dependmore and more on how energy consumption,human is about to face enery shortage and the pollutionof the environment more serious. solar energy, as a inexhaustible and clean resource, has beenbecome a hot spot of research and exploitation for mankind development. the same time,we haveachieved significant results.as an ideal distributed generating energy,grid-off photovoltaic powergenerating system is very suitable for remote areas away from the grid,or island residents supplieddaily electricity.this paper present the situation and prospects of photovoltaic power generatingsystem.then analyzed the key technologies and difficulties of the existing PV inverter system. giventhe different ways of photovoltaic inverter system,the small off-grid photovoltaic inverter powergenerating system has beeb taken as the object of research and design.In this paper,the small off-grid photovoltaic inverter system with a high frequency transformerisolated as the object of study, describes the basic principle of the off-grid photovoltaic invertersystem and its development trend. and based on the small photovoltaic inverter system,the maintopologies of the PV system have been detaled analysis. the DC/DC, LLC series resonantconverter,inverter and other major topology are analysed,modeling and seleced. thereafter,the keyhardware part of the solar inverter system (sample circuit, drive and protection circuits,etc.) arecarried out for a detailed analysis and design. the strategy controlled often in PV system has madea brief analysis description. and study the working characteristics of the main power devices underthe conditions of high-freguency. so diodes,power switches and magnetic components are taken asthe object of research. the quantitative analyse and modeling of the inverter system losses havebeen given. which was introduced with the single full bridge inverter in this paper. According to thephysics loss model of the power switches,power diodes and magnetic components, this paper showthe main power components switching loss characteristics. And based on this power losscharacteristics, a mathematical model of the main circuit power loss is developed. So theoptimistic module frequency of the switches can be obtained from the loss mathematic model. and ifthe switches operate at this optimistic module frequency, the main devices power loss would beefficiently reduced.Finally,small off-grid photovoltaic inverter system hardware experiments was been turned andverify the design, through the observation of the voltage and current waveforms under different loadcondition,we can verified the design.the experiment has proved that this photovoltaic invertersystem basically meet the expectation.