Research And Design Of The Grid-Connected Three-Phase Photovoltaic Inverter

With the fast development of market economy and modern industry, the exhaustion of energy resources and the environmental pollution have become two key points restricting the healthy development of human society. Developing and using the new energy sources become more and more important, solar energy has been gradually used because of its advantages such as clearness, enrichment etc. In recent years, photovoltaic (PV) inverter power supply as the leading part of power conversion has been well researched.The grid-connected photovoltaic inverter is researched and designed in this paper, to pursue the smaller volume,the higher efficiency,the bigger precision and the convenience. In the inverter, three power transmitting structures are designed , that are DC-HFAC-DC-LFAC. Some innovative and applied technologies are used, such as the SPWM,the SVPWM,the high frequency link,the DSP digital control,the digital PLL, and so on.The DC-DC converter is designed , based on the high frequency link, that make the inverter insolated between the DC-DC converter and the DC-AC inverter , and make it smaller. The DC-DC converter is not referred in this paper, and the DC-AC inverter is the main content:Firstly, four kinds of three-phase DC-AC inverter Topology are expounded. Based on the advantage of the three-phase four-leg inverter, it is selected as the main circuit, and it can be used for the loads unbalanced. SVPWM based on three inner loops current hysteresis and two-dimensional space vector are expounded. Thanks to the practicality, the two-dimensional space vector is selected as the control mean in this paper.Next, because of the TI's TMS320F2812, the system can live up to the digital realization,the smaller volume,the higher security and dependability. In this paper, the peripheral control circuit, sampling circuit, over-loading protection, short protection, phase-locked circuit, driver circuit, direct current capacitor, LC filter, LCL filter, cushioning circuit are designed. The circuits are simulated mostly in the ORCAD-Pspice, and they make it. Subsequently, the programming environment of DSP is introduced. Relations between voltage and flux space vector and the principle of the SVPWM is expounded. And the paper give the DSP software design for the SVPWM. All kinds of the maximum power point tracking (MPPT) algorithm are expounded, and the CVT Start, single variable INC algorithm is selected in this paper.Finally, the matlab simulating experiment is made, and a perfect result is getted.