Photovoltaic system, direct-current combiner box, and fault isolation method

This application discloses a photovoltaic system, a direct-current combiner box, and a fault isolation method. The photovoltaic system includes a fault isolation circuit and a DC/DC conversion circuit. A first end of the fault isolation circuit is connected to N photovoltaic strings, and a second end of the fault isolation circuit is connected to an input end of the DC/DC conversion circuit. The fault isolation circuit includes a multipole switch, and each group of photovoltaic strings in the N photovoltaic strings is connected to an input end of a power conversion circuit through one pole of switch in the multipole switch. Each group of photovoltaic strings includes at least two photovoltaic strings. When a reverse connection fault occurs in the N photovoltaic strings, the entire multipole switch is turned off in linkage.