Photovoltaic system, power supply system, and insulation fault detection method

A power supply system, comprising:

• an insulation impedance detection circuit connected between a bus and the ground, wherein the bus comprises a direct current positive bus, a neutral bus, or a direct current negative bus, the direct current positive bus and the neutral bus correspond to a first direct current power supply, and the neutral bus and the direct current negative bus correspond to a second direct current power supply;
• and
• the insulation impedance detection circuit comprises at least a switch, and the direct current negative bus is connected to the neutral bus by using an electrical element or a voltage source;
• and
• a controller configured to:
• obtain insulation impedance based on voltages to ground of the bus that are separately corresponding to the switch before and after the switch is turned on, and detect, based on the insulation impedance, whether there is an insulation fault in the power supply system.

A method for a photovoltaic system, wherein the photovoltaic system comprises a first DC/DC circuit, a second DC/DC circuit, a negative voltage circuit, an insulation impedance detection circuit, and a controller, an input end of the first DC/DC circuit is configured to connect to a corresponding photovoltaic string, an input end of the second DC/DC circuit is configured to connect to a corresponding photovoltaic string, a positive output end and a negative output end of the first DC/DC circuit are respectively configured to connect to a direct current positive bus and a neutral bus, a positive output end and a negative output end of the second DC/DC circuit are respectively connected to a first input end and a second input end of the negative voltage circuit, a first output end and a second output end of the negative voltage circuit are respectively configured to connect to the neutral bus and the direct current negative bus, the negative output end of the second DC/DC circuit is configured to connect to the neutral bus, the insulation impedance detection circuit is connected between a bus and the ground, the bus comprises the direct current positive bus, the neutral bus, or the direct current negative bus, the insulation impedance detection circuit comprises at least a switch, and the direct current negative bus is connected to the neutral bus by using an electrical element or a voltage source;

• and
• the method comprising:
• obtaining a voltage to ground of the bus that is before the switch is turned on;
• obtaining a voltage to ground of the bus that is after the switch is turned on;
• obtaining insulation impedance based on the voltage to ground of the bus that is before the switch is turned on and the voltage to ground of the bus that is after the switch is turned on;
• and
• detecting, based on the insulation impedance, whether there is an insulation fault in the photovoltaic system.