CONTROLLER FOR POWER CONVERSION SYSTEM

A controller for a power conversion system includes a determination unit configured to determine whether a current time is in nighttime in an environment of a power converter that is connected to one or both of a direct-current power supply and an alternating-current power supply, and a control unit configured, in a case that the determination unit determines that the current time is in the nighttime, to maintain a switch in a closed state, the switch being provided between the power converter and one of the alternating-current power supply and the direct-current power supply, and to maintain power consumption by a resistor provided in a main circuit inside a housing of the power converter. The power conversion system can suppress lowering of temperature inside a housing without separately including a space heater.