Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Akira Isono

Masuo Goto

Hiroaki Aotsu

Yasushi Momochi

Takaaki Kai

Koichi Kimura

Yoshihiro Uchiyama

Akihisa Kaihara

Mamoru Fukushima

Satoshi Kitamura

Yukio Yamaguchi

Tunehiko Takakusagi

Masanobu Araki

Haruo Ishikawa

Hirosi Okada

Tsutomu Inayama

Voltage, current and field voltage of a generator connected to an electric power system are sampled at a predetermined period for analog-digital conversion and then led to a digital computer. In addition to computation for AVR, the computer computes from its input the generator output power, and also monitors the occurrence of a fault, the removal of the fault and variation in the generator output in the system. After the occurrence of a fault, the field excitation of the generator is intensified until the generator output power reaches substantially a peak value, but after the peak value is substantially passed by, the excitation is conversely depressed to a value below the level which is present before the fault occurs. When the generator output power recovers the value which is present before the fault occurs, the computer returns to deliver the AVR output.

Method and apparatus for controlling excitation of a generator

A field control apparatus for a generator having a field winding comprises a terminal voltage control unit for controlling a field current of the generator in accordance with a difference between a terminal voltage signal of the generator and a reference voltage signal, which control unit has at least one of a line drop compensation function, an under-excitation limitation function, an over-excitation limitation function, a power factor regulation function, an armature winding over-current compensation function and a cross-current compensation function. The field control apparatus includes a detector as a common signal source for detecting active power and reactive power components at an output terminal of the generator and means responsive to the output of the detector for performing scalar operation in accordance with a function of the added compensation/control function described above. An output of the operating means is added to the differential signal as an added function signal to control the field current for excitation of the field winding.

Excitation control apparatus for a generator

Disclosed is an apparatus for carrying out normal stop of a synchronous generator in an advantageous manner without use of a field breaker. The apparatus comprises a six-phase thyristor converter for controlling field excitation of the synchronous generator in dependence upon terminal voltage thereof, which converter exhibits not only a forward conversion function (power rectifier) but also backward conversion function (power inverter). When a generator operation stop command is produced, the operation of the converter in power rectifier mode is changed over to power inverter mode. During the inverter mode operation, when the terminal voltage of the synchronous generator becomes lower than a preset value, a pair of counter part thyristors among the thyristors constituting the converter are simultaneously fired to bring about a short-circuited state in the excitation circuit with all the firing pulses supplied to the other thyristors being suppressed, thereby to complete the stopping operation for the synchronous generator.

Excitation control apparatus suited for normal stop operation of

In a control system for a hydroelectric power station system including upper and lower water reservoirs connected through a water channel, an intermediate water reservoir having a smaller storage capacity than those of the upper and lower reservoirs and provided on the water channel in cascade with the upper and lower reservoirs, and two power stations disposed between the upper and intermediate reservoirs and between the intermediate and lower reservoirs, respectively, the control system is arranged such that the water level of the intermediate reservoir is detected continuously and the detected value of the water level is used to correct the load instructions which are applied to the power stations for controlling outputs of the power stations whereby the water level of the intermediate reservoir is maintained substantially constant, while the power generation of the power stations is controlled so as to satisfactorily meet with the load instruction applied to the power system.

Control system for hydroelectric power station system

An intermediate intercept valve controlling method and system for use in a heat power plant wherein the occurrence of a fault in a transmission system is detected by an abrupt decrease in generator output, and the intercept valve is closed to a certain opening depending upon the magnitude of an output variation and is then opened when a rotor angle between the internal voltage and terminal voltage of the generator reaches the first peak value.

Intercept valve controlling method and system for use in a heat power

The field excitation flux of the synchronous generator is controlled in response to the summing rotor angle signal of a predetermined set signal and of a rotor angle signal representing a phase difference between the voltage equivalent to an infinite bus voltage and the output voltage from the pilot generator provided on the same rotating shaft as the synchronous generator.

Field excitation control system for the synchronous generator

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Hitachi, Japan

Akira Isono