Hitachi, Ltd.

The Kansai Electric Power Co., Inc.

The Kansai Elect. Power

Tadaatsu Kato

Akio Ito

Hiroto Nakagawa

Yasuteru Oono

Osamu Nagura

Masuo Goto

Yosio Furukawa

Hiroshi Sugisaka

Osamu Sugimoto

Shigehiro Kayukawa

Haruo Nohara

Sadahiko Niwa

Hidenori Sawa

A generator/motor system comprises a generator/motor having a primary winding and a secondary winding installed on the motor rotor coupled to a prime mover/load, a main circuit interposed between a power system and the primary winding of the generator/motor, an excitation circuit including a frequency converter inserted between a part of the main circuit and the secondary winding of the generator/motor, a frequency difference detector for determining the difference between the frequency of the power system and a frequency dependent on the rotational speed of the load, and a phase-shift control device for controlling the firing phase of the frequency converter in the excitation circuit by use of a signal from the frequency difference detector as a reference signal. In normal operation, a frequency signal following the frequency of the power system is produced, while at the time of a disturbance of the power system, the same frequency signal of the power system as before the disturbance continues to be produced thereby to keep the system in stable operation. For this purpose, a starting electric machine, a synchronous motor and a synchronous generator are aligned, and an output of the synchronous generator is applied to the frequency difference detector.

Variable-speed generator/motor system

A control system for controlling the load of an AC motor/generator of secondary AC excitation type connected to a power system in parallel to at least a synchronous machine. The AC motor/generator has the secondary excitation winding thereof controlled in the amount of excitation so as to generate an output in accordance with an external output command. In the case of variation of power flow between the power system and the synchronous machine, the output command is corrected in accordance with the variation, and the amount of the secondary excitation is controlled by the corrected output command, whereby the variation of power flow between the power system and the synchronous machine is absorbed by the AC motor/generator thereby to prevent the synchronous machine from stepping out.

Control system for AC motor/generator of secondary AC excitation type

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Takarazuka, Japan

Tadaatsu Kato