Research On The Technology Of Photovoltaic Array Connected To Distributed Grid

With the increase of oil prices and the shortage of global energy supply, since the21st century, how to rationally develop and effectively use the green energy becomes the imminent problem all over the world. Solar energy, as a clean energy, is gradually exerting its advantages, the development of the key technology of grid-connected PV system will play a bigger role in promoting. A large number of DG accessing to the tradition power grid brought a lot of negative effects.The appearance of Micro-grid can alleviate the adverse effects, so Micro-grid is focused by many countries.The thesis researches on the control strategies of PV system which uses the SVPWM modulation as the base. Power injection DG usually implements MPPT control combined with PI control. The PV system which controls the Grid-Forming DG based on droop control implements PQ control of Grid-Forming DG by adding adjustment loop of the droop controller, and it also finishes the smoothly switching between the two control strategies.Firstly, analyses the advantages and disadvantages of the power systems which have different array structure. The criteria of PV grid-connected system is listed and compared, and introduces the maximum power point tracking method. Perturbation and observation method is carried out by MATLAB simulation.Secondly, it is designed, in the thesis, that the power injection DG uses the control strategy of double close loop (the voltage loop and the current loop) with PI control, which makes the current waveform become stably with less harmonic. It can make the output current of inverter and the grid voltage has the same frequency and the same phase, which ensures that the power factor is one approximately. The thesis establishes the simulation platform of Micro-grid, which consists of Power Injection DG and Grid-Forming DG, and the result proves that the Micro-grid can operate stable. The control scheme of Grid-Forming DG base on droop control, and it is improved by adding the line voltage drop compensation into the Q-V droop characteristic to achieve the precise sharing of reactive power. The control mode can be changed from droop control to PQ control by switching adjustment loop.Finally, hardware of PV system based on DSP is designed, and the software flow pattern is designed.