Abstract: A direct current-direct current conversion circuit includes: an input inductor, a first capacitor, a second capacitor, a flying capacitor, a first switch, a second switch, a first inductor, a first diode, a first buffer circuit, a third switch, a fourth switch, a second inductor, a second diode, and a second buffer circuit. A power supply, the input inductor, the first diode, the second diode, the first capacitor, and the second capacitor are sequentially connected in series. A first terminal of the flying capacitor is connected between the first diode and the second diode. A second terminal of the flying capacitor is connected between the first switch and the third switch, and the second terminal of the flying capacitor is further connected between the second switch and the second inductor.

Abstract: 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.

Abstract: This application discloses a protection circuit for preventing a misconnection at an input end and a photovoltaic power generation system, and relates to the field of power electronics technologies. The protection circuit includes an input end, a misconnection detection unit, a mechanical interlocking unit, and a switch unit. The input end is configured to connect to an output end of a direct current power supply. A first input end of the misconnection detection unit is connected to a first port of the input end, and a second input end of the misconnection detection unit is connected to a second port of the input end. An output end of the misconnection detection unit is coupled to the mechanical interlocking unit. The mechanical interlocking unit is connected to the switch unit. A first end of the switch unit is configured to connect to the input end, and a second end of the switch unit is configured to connect to a next circuit.

Abstract: A direct current-direct current conversion circuit includes: an input inductor, a first capacitor, a second capacitor, a flying capacitor, a first switch, a second switch, a first inductor, a first diode, a first buffer circuit, a third switch, a fourth switch, a second inductor, a second diode, and a second buffer circuit. A power supply, the input inductor, the first diode, the second diode, the first capacitor, and the second capacitor are sequentially connected in series. A first terminal of the flying capacitor is connected between the first diode and the second diode. A second terminal of the flying capacitor is connected between the first switch and the third switch, and the second terminal of the flying capacitor is further connected between the second switch and the second inductor.

Abstract: A fault isolation apparatus includes a controller and a circuit breaker. When the circuit breaker is located on a bus connected to a DC/DC conversion unit, if a voltage collected by a first voltage collection terminal is a negative value, it indicates that input or output of the DC/DC conversion unit is reversely connected. In this case, if the circuit breaker is controlled to be opened, the DC/DC conversion unit can be prevented from being connected in series to other parallel DC/DC conversion units. If a voltage collected by a first voltage collection terminal is low and a current collected by a current collection terminal is large, it indicates that the DC/DC conversion unit is short-circuited. In this case, if the circuit breaker is controlled to be opened, another component connected in series to the DC/DC conversion unit can also be prevented from backfeeding energy to the DC/DC conversion unit.