Water electrolysis system and control method therefor

The invention relates to a water electrolysis system and a control method therefor. The water electrolysis system (10) produces hydrogen gas at a higher pressure than oxygen gas. A Peltier cooler (84)is disposed between a gas-liquid separator (80) and a back pressure valve (20) in a hydrogen gas flow path (18), and cools and dehumidifies the hydrogen gas. A temperature sensor (86) measures a temperature in the vicinity of the Peltier cooler (84), and outputs a temperature measurement value. A pressure sensor (78) measures a pressure of the hydrogen gas between a cathode (14) and the back pressure valve (20) in the hydrogen gas flow path (18), and outputs a pressure measurement value. A control unit (22) controls a cooling temperature by the Peltier cooler (84), in a manner so that the temperature measurement value becomes a target temperature that exceeds the freezing point of water corresponding to the pressure measurement value. At least a portion of the target temperature becomes lower as the pressure meas