PURPOSE: To make it possible to share burden of stable effective and reactive power during parallel operation, to reduce fluctuations in system voltage and frequency and to restrict cross current immediately after synchronizing of generator.

CONSTITUTION: At the same time with the start of synchronizing, the voltage and frequency of each generator 1a, 1b are adjusted to reference values, breakers are closed at the phase matching point of each generator and, after synchronizing, terminal controllers 15a and 15b are provided, which share the effective and reactive power of the generator during parallel operation. In order to control the voltage and frequency of bus to constant values after synchronizing by the terminal controller, the voltage, frequency and effective and reactive power of generator at opposite sides are sent to and received by serial transmitting units 14a and 14b between the terminal controllers.