Starter of grid-connected inverter and control method thereof

A starter of a grid-connected inverter, comprising:

• a first switch electrically connected between an AC electric grid and the grid-connected inverter;
• a precharge branch circuit connected with the first switch in parallel, wherein the precharge branch circuit comprises a second switch and a first resistor connected in series;
• and
• a controller comprising an input end, a first output end and a second output end, wherein the input end of the controller receives and inspects the DC voltage signal of the inverter, and when the DC voltage exceeds a predetermined voltage threshold, the first output end of the controller sends a first control signal to turn on the first switch, and the second output end outputs a second control signal to turn on or off the second switch,
• wherein there is a delay period td3 between the send time of the second control signal having a first level and the send time of the first control signal, and td3 is larger than 0.

A control method of a starter, wherein the starter comprises a first switch and a first resistor connected in parallel, and the first switch is electrically connected between an AC electric grid and a grid-connected inverter, and the control method comprises:

• a) inspecting a DC voltage of the grid-connected inverter;
• b) sending a first control signal to turn on the first switch when the DC voltage exceeds a predetermined voltage threshold;
• c) performing a delay for a time period td1 which is larger than zero;
• d) sending a second control signal to make the grid-connected inverter enter into a boost mode.

A control method of a starter, wherein the starter comprises a first switch and a precharge branch circuit connected in parallel, the first switch is electrically connected between an AC electric grid and a grid-connected inverter, the precharge branch circuit comprises a second switch and a first resistor connected in series, and the control method comprises:

• a) inspecting a DC voltage of the grid-connected inverter;
• b) sending a first control signal to turn on the first switch when the DC voltage exceeds a predetermined voltage threshold;
• c) performing a delay for a time period td4 which is larger than zero;
• d) sending a second control signal having a first level to turn off the second switch.