Photovoltaic system, relay detection method, and power supply system

A method, wherein the method is applied to a photovoltaic system, the photovoltaic system comprises an inverter, a filter capacitor, and a relay, an input of the inverter is configured to be connected to a photovoltaic array, an output of the inverter is connected to a first end of the relay, a second end of the relay is connected to an alternating current grid, the output of the inverter is connected to the filter capacitor, the method comprising:

• sending a turn-off instruction to the relay when a voltage of the filter capacitor and an alternating current grid voltage have a same frequency and a same phase;
• stopping driving of an action of a switch transistor in the inverter within a preset phase range of the voltage of the filter capacitor, wherein the voltage of the filter capacitor is greater than or equal to a preset threshold when the phase of the voltage of the filter capacitor falls within the preset phase range;
• and
• sending fault alarm information of the relay when it is detected that a valid value of a difference between the voltage of the filter capacitor and the alternating current grid voltage is less than a preset value.

A photovoltaic system, comprising:

• an inverter and a relay, wherein an input of the inverter is configured to be connected to a photovoltaic array, an output of the inverter is connected to a first end of the relay, and a second end of the relay is connected to an alternating current grid;
• a filter capacitor, wherein the output of the inverter is connected to the filter capacitor;
• and
• a controller, wherein the controller is configured to:
• send a turn-off instruction to the relay when a voltage of the filter capacitor and an alternating current grid voltage have a same frequency and a same phase, drive an action of a switch transistor of any phase in three phases in the inverter, and send fault alarm information of a relay of the any phase when a valid value of a difference between the voltage of the filter capacitor and the alternating current grid voltage is less than a preset value.