Research On Residential Photovoltaic Grid-connected System

The application of solar energy is paid more attention to by people than before and Photovoltaic (PV) generation, one method of using solar energy, is very promising. The goal for the use of solar energy will aim at the grid-connected photovoltaic generation system.The author provide a suitable topological construction for the Photovoltaic grid-connected system, which doesn't use the industrial frequency transformer or high -frequency transformer and features the small size, low cost and easy implement of the control scheme.It is demonstrated theoretically in this thesis that the maximum power-output can be matched by adjusting the duty ratio of the DC/DC circuit. And the arithmetic of conductance increment has also been given to trace the maximum power point.The model of the inverter is derived and a kind of circuit control strategy is applied. To eliminate the theoretical error the author presents an improved strategy based on the multi-variable double-loop control. Some resultants from the simulation using the SimPowerSystems tool of MATLAB prove the feasibility and validity. As to the disturbing variable resulted from the grid voltage the author provide the method of feedforward compensation.A flexible soft Phase Locked Loop is brought forward to keep the frequency and phase synchronous to the grid.Islanding phenomenon must be prevented in the application of the PV grid-connected system. A method of current disturbing are developed and the simulation is conducted.