Hitachi, Ltd.

Akira Brando

Takao Kuwabara

Yasuteru Oono

Kenzyu Ogiwara

Akihiro Sakayori

Isao Yokoyama

Shigeaki Hayashi

A variable-speed pumped-storage power generating system includes a variable-speed generator/motor, a frequency converter connected to an electric power system, and a pump/turbine driven by the generator/motor. The power generating system comprises an optimum rotation speed function generator calculating an optimum rotation speed of the motor for driving the pump, a speed detector generating a speed detection signal of the motor, a speed regulator receiving the output signals from the function generator and speed detector for generating an output correction signal, an adder adding the output correction signal to output command signal, a comparator comparing the output signal of the adder with an output power detection signal generated from a motor output detector and generating an error signal, and an output regulator controlling the excitation of the secondary winding of the motor through the frequency converter so as to decrease the output power error to zero, thereby controlling the output and rotation speed of the motor. The power generatign system also comprises an optimum guide-vane opening function generator calculating an optimum guide vane opening, a comparator comparing the output signal of the guide-vane opening function generator with a guide-vane opening detection signal from a guide-vane opening detector, and a guide-vane opening regulator controlling the opening of the guide vanes according to the result of the comparison.

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Hitachi, Japan

Akira Brando