Research For Single-Phase Grid-Connected Photovoltaic System

For the strenuous energy sources currently, the application of solar energy is paid more attention by many countries all the word than before. Photovoltaic (PV) generation, one method of using solar energy, is very promising. The inevitable strend of the use of solar energy will be the grid-connected photovoltaic system.This paper analyzed the topology of the grid-connected system and conversation of energy , maximum power point tracing(MPPT),control strategy and the Phase Locked Loop(PLL) technology of grid-connected system.For the single-phase PV grid-connected system ,the paper expatiated a suitable topological construction, which doesn't use the industrial frequency transformer or high-frequency transformer with features which the small size, low cost and easy control strategy.The paper discussed the conversation of single-phase energy,also the integer structure basised on DSP the single-phase PV grid-connected system.The author analyzed several methods of MPPT of grid-connected system .And the arithmetic of incremental conductance has also been given to the MPPT of PV system. In this thesis it is demonstrated theoretically that the maximum power-output can be matched by adjusting the duty ratio of the DC/DC circuit.The manipulative model of the single-phase PV grid-connected system's inverted output is upbuilt and a kind of PV grid-connected feedback circuit control strategy is adopted, which is emulated. To eliminate the shortage the author presents an improved strategy based on double-loop control. The resultants of the simulation using MATLAB proved the feasibility and validity.For the current of PV grid-connected system must be the same phase and the same frequency as the grid voltage, the soft PLL based on DSP is introduced to keep the frequency and phase synchronous to the grid.