To reduce the rush current that flows, when an induction generator is connected to an electric power system.

After an induction generator G is rotated at synchronous speed with circuit breakers S1, S2, S3 open, the circuit breakers S2, S3 are closed. The voltage of the induction generator G is adjusted by the reactive power of a variable reactive power generator VQ. The circuit breaker S3 is opened, when a current flowing in the circuit breaker S3 becomes almost zero. The circuit breaker (S1) is closed, when the controlled voltage and phase angle of the induction generator G become equal to the voltage and to the phase of the electric power system.