Power conversion system

A power conversion system configured to supply direct current power to an electrolysis device that electrolyzes a raw material to produce hydrogen, the power conversion system comprising:

• a power conversion device that converts source power into direct current power;
• a positive-side wiring and a negative-side wiring that connect the power conversion device and the electrolysis device to each other;
• a filter capacitor connected between the positive-side wiring and the negative-side wiring;
• a relay provided on at least one of the positive-side wiring and the negative-side wiring on the electrolysis device side of the filter capacitor;
• a first voltage detection device connected between the positive-side wiring and the negative-side wiring on the power conversion device side of the relay;
• a second voltage detection device connected between the positive-side wiring and the negative-side wiring on the electrolysis device side of the relay;
• and
• a control device configured to control the power conversion device,
• wherein the control device is configured to control the power conversion device so that a first voltage detected by the first voltage detection device is greater than or equal to a second voltage detected by the second voltage detection device, when connecting the relay.