Study on soft-switching technology of photovoltaic grid-connected system

To solve the problem of the control of conventional grid-connected with hard switch, the instant large surge current of connected-grid, the long time interval of grid-connected, the islanding effect of grid -connected and the PVGS (photovoltaic generation system) not being broken away from grid quickly, the flexible control strategy was proposed to realize connected-grid with bidirectional SCR. This technique can cancel the transformer-isolated in the PVGS and implement relay protection. After accomplishing grid-connected, by measuring real-time the active power and reactive power in grid, the SCR can be triggered, and then the PVGS provides stable and reliable power to the grid. The results of theoretical analyses shows the flexible control strategy is feasibility, the simulation results prove the feasibility of the system and control strategy above.