Design of grid-connected photovoltaic system using soft cut-in control

The paper describes a grid-connected photovoltaic system, which uses the SPWM technology to invert the solar battery voltage to the grid voltage. The system adopts the Boost circuit based on the MPPT to boost the photovoltaic arrays output voltage to the 350 V DC voltage, while using MPPT control to maximize the output power of photovoltaic arrays. The system uses the control strategy of the triangle wave comparison to achieve DC/AC inverter. In order to reduce impact on the grid in the process of the cut-in grid, the system adopts the soft cut-in control, that is, after the system detects the normal frequency of the power grid, the controller generates the increasing-amplitude reference sinusoidal current for output current closed-loop control. Using the feed-forward of the grid voltage, the system can eliminate the effect to output current from the gird voltage. In the paper, the simulation result proves the validity of soft cutin control, and the system hardware and software design based on soft cut-in control will be introduced.