An output converter includes a DCDC conversion section, a secondary side voltage/current monitoring section detecting a power from the DCDC conversion section, a maximum operation point control section determining what voltage is to be set by the DCDC conversion section so that the power detected by the secondary side voltage/current monitoring section is maximum, a DCDC short-circuit switch via which a current from a module bypasses the DCDC conversion section to outside, a primary side voltage/current monitoring section measuring the current from the module, a module short-circuit switch switching between a state where a secondary side cathode and a secondary side anode are short-circuited and a state where they are not short-circuited, the maximum operation point control section causing the DCDC short-circuit switch and the module short-circuit switch to switch.