| In recent years,with the energy crisis occurs frequently all over the world, the traditional fossil energy reserves are facing steep status,phenomenon of environmental pollution also becoming more and more obvious.So,finding an important energy strategy with widely distuibuted, clean and high performance for every country is becoming very necessary.Solar energy as a green energy with a characteristic of great storage volume, widely distribution and no pollution has aroused wide public concern in new energy industry.Photovoltaic grid-connected system is an efficient energy saving system,it can transform solar energy emitted by the light into electrical energy back to the power grid.This paper studies the photovoltaic inverter as the core component of the system,its efficiency,electric energy quality and safety performance play a key role to grid-connected.So,there is a very important significance to research on the PV grid-connected inverter.The thesis comes from a company’s research and design projects which purpose is using DSP chip as the control core and programming proper software to design a grid-connected inverter system. This system ultimately achieves the aim of producing three-phase alternating current power which with the same frequency and phase to public power grid, and then accomplishes power energy feedback by digital control.In this project elements,I’ll complete the following work elements.First,the article analysis of solar panels in the basic model and principle and determine the cotrol strategy and control mode after compare different modes in the whole system.The method is using three-phase full bridge inverter with voltage input and current source output, and sampling the input DC voltage and input DC current in MPPT regulation at the same time. The purpose is reduce power loss and improve the quality of power supply. In short,control thought of system should in accordance with the strategy strictly.Secondly, grid-connected inverter is focused on the study of SVPWM(Space Vector Pulse Width Modulation)algorithm analysis,and research improvement method according to basic algorithm is improved in digital chip.In the past,mode of SVPWM technology often by calculating the function time of two adjacent vectors before vectors distribution, but this method occupies a long processing time and have large amount of calculation in digital processor (such as DSP),so we transform them to calculate duty ratios of every bridge of drive signals. The deduction of this algorithm have mentioned in the article. Through the programs debug and the experiments we can see the machine perform definitive feasibility and stability,it will achieve good effect of inverter.Thirdly,on the basis of the hardware circuit topology is determined and improved, the article mainly design control softwares and programming.On various technical difficulties of control of photovoltaic inverter,such as phase locked,zero adjustment, maximum power point tracking control,carried out a detailed analysis and processing. Then,writing overall control programs by using the SVPWM algorithm mentioned above.System control panel uses TMS320F2812DSP of TI company as main control chip.After program debug that according to actual situation of photovoltaic inverter, finally the results achieve the expected goal.Finally, in environment of MATLAB7.6.0/Simulink establish the simulation model,and get the subsystem circuit simulations’waveforms to improve the feasibility and rationality.Through testing photovoltaic inverter prototype machine to verifies the reliability and stability of the inverter system.The paper gives the simulation waveforms and the whole effect of debugging, and the hardware circuits are briefly analyzed. All the experiments’results can realize photovoltaic inverter parallel operation. Finally, summary and prospect of the work gives that all the works done in this paper, it also points the works which need further perfect in system and gives research directions in future. |
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