PHOTOVOLTAIC SYSTEM, POWER SUPPLY SYSTEM AND INSULATION FAULT DETECTION METHOD

This application provides a photovoltaic system, a power supply system, and an insulation fault detection method. A positive output end and a negative output end of a first DC/DC circuit are respectively connected to a direct current positive bus and a neutral bus. A positive output end and a negative output end of a second DC/DC circuit are respectively connected to a first input end and a second input end of a 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 a direct current negative bus. The negative output end of the second DC/DC circuit is configured to connect to the neutral bus. An insulation impedance detection circuit is connected between a bus and the ground. The bus includes the direct current positive bus, the neutral bus, or the direct current negative bus. The insulation impedance detection circuit includes at least a switch. The direct current negative bus is connected to the neutral bus by using an electrical element or a voltage source. A controller obtains 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 determines, based on the insulation impedance, whether there is an insulation fault in the photovoltaic system, to perform protection in a timely manner.