Research On Control Technique Of 5kW Grid-on Photovoltaic Inverter

Nowadays,energy and environment are two major issues in the world.Humans are seeking renewable energy instead of oil?coal and other conventional energy.Development and utilization of renewable energy become the basic selection of energy development strategy in 21st century.Solar energy is nature's renewable green energy,which is inexhaustible in supply and always available for use for human beings.Photovoltaic(PV)Generation technology is an important way of solving energy crisis.Technique of Grid-on Inverter is the key part in Photovoltaic Power Generation system,5KW photovoltaic inverter can be used independent or grid on,Photovoltaic roof system is the typical applications.Photovoltaic roof is springing up exuberantly domestic and overseas by relevant policies.Photovoltaic Generation technology is becoming more and more important in the using of solar energy.Technique of Grid-on Inverter in Photovoltaic Power Generation system will be the main component in the using of solar energy in the near future.Technique of Grid-on Inverter in Photovoltaic Power Generation system is vital important to the efficiency and quality of electric energy which connect to the grid.This paper mainly focuses on the following aspects:a)This first chapter describes the worldwide energy crisis,development situation of the new energy technologies and grid-connected solar inverter.Then describes the various structures and characteristics of the grid-connect PV systems,and grid-connected solar inverter developing trends and direction.b)DC/DC conversion topology in the PV is discussed in this paper,flyback converter and interleaved flyback converter is mainly discussed,working principle of two types of DC-DC Boost Circuit is analysed in this paper,output voltage gain of these Circuit is inferred;then the advantages and disadvantages of the two types of circuit are compared by means of theoretical derivation and experimental analysis;Finally,it comes to the conclusion that:the output voltage gain of flyback converter and interleaved flyback converter is the same;By counterchange output of two-stage flyback converters,the interleaved flyback converter reduces the effective value of the ripple current through the input bulk electrolytic capacitor,which increases the life of the capacitor,the ripple of output current is reduced and then the total harmonic distortion is reduced.c)Working principle and transfer function of L?LC?LCL grid-connect filter is introduced.L grid-connect filter is mainly used in active power filter,which can restrain the attenuation of inversion output current,but is limited to restrain ripple current.;LC grid-connect filter is usually used for independent inverter because its capacitance can disturb the phase of grid-connect current and standard current;LCL grid-connect filter can restrain high frequency harmonic and gradually be used for high-power?low frequency grid-connect inverters.Finally,the design method of LC and LCL grid-connect filter is detailedly introduced,the mathematical of Grid-on Inverter in Photovoltaic Power Generation system is established an simulated in MATLAB successfully.d)A control nimble and easy to be realized double loop control program which based on capacitive current inner ring and grid-connect current outer ring is designed.e)The basic principle of island effects and active detection method is introduced,the active detection method and passive detection method of Island detection is summarized in this paper.