A power conversion circuit, comprising: a first phase line, a second phase line, and a third phase line; at least one first power conversion unit connected in series to the first phase line, at least one second power conversion unit connected in series to the second phase line, and at least one third power conversion unit connected in series to the third phase line; characterized by a plurality of first start circuits, wherein the plurality of first start circuits are connected in series to the first phase line, each of the plurality of first start circuits comprises a first relay and a first resistor, the first relay and the first resistor are connected in parallel, and first relays in all the first start circuits are configured to be sequentially closed after the power conversion circuit is powered on, to start the power conversion circuit; and a plurality of second start circuits, wherein the plurality of second start circuits are connected in series to the second phase line, each of the plurality of second start circuits comprises a second relay and a second resistor, the second relay and the second resistor are connected in parallel, and second relays in all the second start circuits are configured to be sequentially closed after the power conversion circuit is powered on, to start the power conversion circuit, wherein the circuit is configured such that, after the power conversion circuit is powered on, in the first relays in the plurality of first start circuits, a resistance of a first resistor correspondingly connected in parallel to a first relay closed at a moment T1 is greater than a resistance of a first resistor correspondingly connected in parallel to a first relay closed at a moment T2, and the moment T1 is earlier than the moment T2; and in the second relays in the plurality of second start circuits, a resistance of a second resistor correspondingly connected in parallel to a second relay closed at a moment T3 is greater than a resistance of a second resistor correspondingly connected in parallel to a second relay closed at a moment T4, and the moment T3 is earlier than the moment T4, and such that a rated voltage of the first relay closed at the moment T1 is greater than a rated voltage of the first relay closed at the moment T2, and a rated voltage of the second relay closed at the moment T3 is greater than a rated voltage of the second relay closed at the moment T4. a first phase line, a second phase line, and a third phase line; at least one first power conversion unit connected in series to the first phase line, at least one second power conversion unit connected in series to the second phase line, and at least one third power conversion unit connected in series to the third phase line; characterized by a plurality of first start circuits, wherein the plurality of first start circuits are connected in series to the first phase line, each of the plurality of first start circuits comprises a first relay and a first resistor, the first relay and the first resistor are connected in parallel, and first relays in all the first start circuits are configured to be sequentially closed after the power conversion circuit is powered on, to start the power conversion circuit; and a plurality of second start circuits, wherein the plurality of second start circuits are connected in series to the second phase line, each of the plurality of second start circuits comprises a second relay and a second resistor, the second relay and the second resistor are connected in parallel, and second relays in all the second start circuits are configured to be sequentially closed after the power conversion circuit is powered on, to start the power conversion circuit, wherein the circuit is configured such that, after the power conversion circuit is powered on, in the first relays in the plurality of first start circuits, a resistance of a first resistor correspondingly connected in parallel to a first relay closed at a moment T1 is greater than a resistance of a first resistor correspondingly connected in parallel to a first relay closed at a moment T2, and the moment T1 is earlier than the moment T2; and in the second relays in the plurality of second start circuits, a resistance of a second resistor correspondingly connected in parallel to a second relay closed at a moment T3 is greater than a resistance of a second resistor correspondingly connected in parallel to a second relay closed at a moment T4, and the moment T3 is earlier than the moment T4, and such that a rated voltage of the first relay closed at the moment T1 is greater than a rated voltage of the first relay closed at the moment T2, and a rated voltage of the second relay closed at the moment T3 is greater than a rated voltage of the second relay closed at the moment T4.