Research On Grid-Connected Inverter Control In Photovoltaic Power Generation System

Energy crisis and the increasingly serious problem of environmental pollution have perplexed the pace of human progress, and have became the most serious and urgent global problem. The new kinds of clean energy such as wind energy, solar energy, bio-energy and so on are widely focused because of their incomparable advantages. Solar energy has been recognized as the most potential type of substituted energy, we may expect, in the near future, solar energy will hold an important position in the basic energy supplies.Solar energy generation technology is based on photoelectric effect, by the PV panels, sunlight is converted into electricity. Solar photovoltaic power generation system convert solar energy to AC electricity that meets the grid requirements, and access to the large grid realize grid-connected operation. Recently, the key techniques of solar photovoltaic power generation system mainly include several aspects:efficiency of solar panels, maximum power point tracking and the control of grid-connected inverter. Grid-connected inverter technology is the core of the whole system. Nowadays, popular research in our country is two-stage PV grid-connected power generation system. In this paper, grid-connected inverter of this structure system is researched as follows:Firstly, The development of current situation about solar photovoltaic power generation at home and abroad is discussed, The significance and advantage of China’s photovoltaic power generation technology are pointed out, types of grid-connected PV systems and the grid-connected technology standard are introduced. Secondly, the mathematical model of grid-connected inverter of two-stage PV grid-connected power generation system in different coordinates is established. Control strategy of grid-connecting based on the grid voltage space vector is extracted and analyzed detailed, provided theoretical support for the following grid-connecting control experiments. Several grid voltage orientation methods are compared, and then the hardware method that is based on the grid voltage zero crossing detection is used. The maximum power output and the obtaining method of the reference current in grid-connected PV system are introduced. Finally, SVPWM modulation technology is used in pulse width modulation of the inverter, the concrete steps of software method of SVPWM modulation in the DSP controller is given.In the experimental design, hardware experimental platform of the grid-connected inverter system is built, the compositions of hardware platform based on TMS320F2812includes power module, driving circuit, protection circuit and zero-crossing detection circuit, and design principles are introduced. Main program, interrupt subroutine, various sub-module programs are prepared according to control strategy algorithm. Better hardware and software support are provided for the following experiments.In this paper, software and hardware system have debugged on the designed experimental platform. Completed the independent experiments and some grid-connecting experiments, collected the waveforms of experiments. Through analysis the experimental results we can see, control strategies and procedures that used in the paper are right, hardware system can work reliably, these laid a foundation for the further experiments.