PURPOSE: To enable synchronous throw-in of many generators through a single control board by performing combination control of a phase detector and a sequencer.

CONSTITUTION: A sequencer 100 detects interruption of normal power source and performs sequence control to start a reference generator AG1 thus establishing a voltage having predetermined frequency. Then generators AG 2∼AGn of such number as corresponding to necessary power are started quickly. Output voltages and frequencies of the generators AG1∼AGn are detected through potential transformers 13∼n3 and controlled through the sequencer 100, then they are fed to a phase detector ECU where phase differences against a reference generator phase are detected and fed to synchronization detectors 201∼n01 in order to perform phase regulation. When the phases are matched, circuit breakers 2∼n are thrown in through automatic synchronous throw-in units 202∼m02.