Research On Photovoltaic (PV) Power Grid-connected Inverter Control Technology

With the development of economy and the progress of science and technology,human demand for energy is growing. The future, human demand for energy has notbeen satisfied by the traditional fossil energy, therefore, the development ofalternative energy sources will be used as the main developed countries in the worldfocus on the future energy strategy. Solar energy as being the earliest humandevelopment and utilization of energy, because it is a clean, pollution-free and thereserves of nearly unlimited advantages back into a human vision. Utilization of solarenergy photovoltaic technology as an important technical means, the research hasimportant significance to alleviate the energy crisis.The thesis first introduces the PV grid-connected system structure, discusses thefunction of each part. As photovoltaic grid-connected generation system key,three-phase grid-connected inverter control technology research is the key content ofthe article. Prior to this, the paper first of three phase grid-connected inverter isstudied, analysis of the inverter structure, working principle and its main applicationtypes, especially on grid-connected inverter system commonly used current typeinverter with voltage type inverter for comparison and research, and summarizes theirfeatures. Then this paper selects voltage type inverter as main circuit of three phasephotovoltaic grid-connected system structure, and its mathematical model areanalyzed, this paper derives its in the DQ coordinates of the mathematical model, forthe inverter control technology research for.Through the research on the output characteristics of photovoltaic cells,photovoltaic cell output nonlinear characteristics are clearly explained. Severalcommonly used MPPT method were analyzed, after comparison, incrementalconductance method was selected for this paper to realize the specific MPPTalgorithm.A method based on double loop control inverter control strategy is proposed inthis paper. The basic idea of this method is: the photovoltaic grid-connected powersystem grid connected power tracking photovoltaic array maximum output power. SVPWM modulation is referenced articles of grid-connected current control, currentloop is as an inner loop with PI regulator to adjust its output, as a SVPWM modulatedsignal. By the photovoltaic cell MPPT link to get the maximum output power wasused as the outer power reference power, with its and outlets of the instantaneouspower compared with PI, adjust its output as a current loop reference volume.According to the control theory of PV and MPPT, simulation model, simulationmodel of three-phase photovoltaic grid-connected generation system is presented.Through the simulation experiment, obtained the incremental conductance method toachieve MPPT characteristic curves, the results show that this method has excellentcharacteristics; three-phase photovoltaic grid-connected inverter system thesimulation results show that, in the article mentioned power control strategies and thecontrol effect is fully consistent with the requirements of the grid, method is verifiedfeasible.Photovoltaic grid-connected generation system in the presence of the island atthe end of the article are introduced, several kinds of commonly used detectionmethods were also analyzed and studied.