A parallel power supply system, comprising a common wiring busbar, an input wiring busbar, an output wiring busbar, and at least two three-wire DC-DC converters, wherein each of the three-wire DC-DC converters comprises a DC-DC conversion circuit, an input wiring terminal (), an output wiring terminal (), and a common wiring terminal (); input wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the input wiring busbar, output wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the output wiring busbar, and common wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the common wiring busbar; the input wiring busbar is configured to connect to a first power input terminal of a first direct current power supply; the output wiring busbar is configured to connect to a first power terminal of a load; the common wiring busbar is configured to connect a second power terminal of the load and a second power input terminal of the first direct current power supply; and all the three-wire DC-DC converters convert a voltage of the first direct current power supply into a voltage required by the load and output the voltage, and output currents at the output wiring terminals () of all the three-wire DC-DC converters are consistent; wherein the parallel power supply system further comprises a controller, the at least two three-wire DC-DC converters comprise a first three-wire DC-DC converter and a second three-wire DC-DC converter, the parallel power supply system is characterised in that the parallel power supply system further comprises a first current detection circuit and a second current detection circuit; the first current detection circuit is configured to detect a first current at an output wiring terminal () of the first three-wire DC-DC converter, and transmit the first current to the controller; the second current detection circuit is configured to detect a second current at an output wiring terminal () of the second three-wire DC-DC converter, and transmit the second current to the controller; and the controller is specifically configured to control an output voltage of the first three-wire DC-DC converter to enable the first current to be consistent with a preset current and control an output voltage of the second three-wire DC-DC converter to enable the second current to be consistent with the preset current. input wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the input wiring busbar, output wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the output wiring busbar, and common wiring terminals () of all the three-wire DC-DC converters are connected in parallel to the common wiring busbar; the input wiring busbar is configured to connect to a first power input terminal of a first direct current power supply; the output wiring busbar is configured to connect to a first power terminal of a load; the common wiring busbar is configured to connect a second power terminal of the load and a second power input terminal of the first direct current power supply; and all the three-wire DC-DC converters convert a voltage of the first direct current power supply into a voltage required by the load and output the voltage, and output currents at the output wiring terminals () of all the three-wire DC-DC converters are consistent; wherein the parallel power supply system further comprises a controller, the at least two three-wire DC-DC converters comprise a first three-wire DC-DC converter and a second three-wire DC-DC converter, the parallel power supply system is characterised in that the parallel power supply system further comprises a first current detection circuit and a second current detection circuit; the first current detection circuit is configured to detect a first current at an output wiring terminal () of the first three-wire DC-DC converter, and transmit the first current to the controller; the second current detection circuit is configured to detect a second current at an output wiring terminal () of the second three-wire DC-DC converter, and transmit the second current to the controller; and the controller is specifically configured to control an output voltage of the first three-wire DC-DC converter to enable the first current to be consistent with a preset current and control an output voltage of the second three-wire DC-DC converter to enable the second current to be consistent with the preset current.