Hitachi, Ltd.

The Kansai Electric Power Co., Inc.

Other

Anandenki Co., Ltd.

The Kansai Elect. Power Co.

The Kansai Electric

Hiroto Nakagawa

Akira Bando

Takao Kuwabara

Yasuteru Oono

Eiji Haraguchi

Osamu Nagura

Eizo Kita

Kenichi Ono

Keiji Saito

Hiroshi Sugisaka

Koji Watanabe

Chikara Tanaka

Tadao Kawai

Yosio Furukawa

Hiroshi Kashiwazaki

Junichi Shiozaki

Isao Yokoyama

Shigehiro Kayukawa

Kei Katayama

Haruki Hagiwara

Keiichi Mitsuhashi

Ezo Kita

Akio Ito

Yosuke Takahashi

Rintaro Katayama

Hideki Okita

Hisao Inoue

Yuichiro Katsu

Hashime Nagai

Yasuhiro Yasaka

Haruo Nohara

Sadahiko Niwa

Shigeaki Hayashi

Yoji Tanaka

Hidenori Sawa

Tadaatsu Kato

Kenichi Yamada

Ikuro Miyashita

Masataka Harada

Yasuteru Ohno

Mituru Hori

Takao Kuwahara

Akira Momiyama

Yukio Nakaya

A traffic management server is configured to determine a base station at which a handover occurs to a base station having a slower maximum communication speed as an area boundary base station, determine a terminal located within a coverage of the area boundary base station, and instruct a control apparatus included in a mobile network to limit a maximum usable bandwidth of the determined terminal.

Traffic management server

A multi-hop relay wireless communication system provided with an AGW (), a policy controller (), a base station (), one or more relay stations (), and a mobile station () collects data path setting information into the AGW () after the establishment of the wireless links between the base station and the relay stations and between the relay stations and the mobile station, selects a relay station () which becomes the data path from the one or more relay stations by using the collected information, and sets the optimal path from the AGW () to the mobile station ().

Multi-hop relay radio communication system, access gateway, and route selection method

To realize a handover in which a gateway connecting to the access networks using different protocols is an anchor. In a communication system, the gateway holds a service identifier management table for converting a service identifier of different kind with the protocol into a PDN identifier, and at the time of handover, specifies a session to be held with the user identifier and the PDN identifier, selects the same PDN connected to the movement source, and reassigns the same IP address that has been already assigned at the movement source.

Communication system and method, and gateway

A pump turbine includes a runner connected to a generator motor, a water discharge controller for adjusting the quantity of water passing through the runner and a governor for detecting a rotational speed of the runner and controlling the water discharge controller to get a predetermined rotational speed of the runner. Upon a load rejection which shuts off the generator motor from an electric power system, the governor is controlled to make a target speed value of the runner after a load rejection higher than a target speed value before the load rejection. The target speed value is a reference speed to be compared with actual speed so that the governor determines when or how to open or close a water discharge controller in response to a balance between the two speeds.

Pump turbine, method of controlling thereof, and method of stopping thereof

An object of the present invention is to provide a pump turbine capable of improving the stability of the governor by fully lessening the influences by the S-characteristics even when the running point of the pump turbine is in the S-characteristics region. For this purpose, in a pump turbine comprising a runner which is coupled with a generator motor, discharge control apparatus for controlling the quantity of water passing through the runner, and a governor for controlling said discharge control apparatus to keep the runner speed at a predetermined speed, the arithmetic apparatus of said governor is controlled to temporarily open said closing discharge control apparatus in the leading half of the speed decrease or earlier after the first speed increase upon a load rejection turns to a speed decrease upon a load rejection which abruptly shuts off power from the generator motor, so that the rotational speed of the runner goes down at much slower rate than the rate of increasing immediately after a load rejection.

Method of controlling a pump turbine

A safety fence for a square hatched formed in a slab of a building is provided. The fence has lids pivotable about opposed sides of the hatch, and has such a size that about half of the opening of the hatch is closed by each of the lids. Side frames having a predetermined height are pivotable about opposed sides of the hatch. A plurality of gear mechanisms is provided, with each mechanism comprising a first gear and a second gear in mesh with each other, a first shaft supporting the first gear, a second shaft supporting the second gear, the first and second shafts extending parallel to the opposed ends of the hatch, the first gears being secured to lower ends of the lids, and counterweights mounted to one of the second shafts. The safety fence is set up by erecting the lids and the side frames. A plurality of brackets each having a pair of bracket portions secured to the inner wall of the hatch. The pairs of bracket portions are provided on each side of each of the gear mechanisms and support the first and second shafts supporting the first and second gears.

Safety fence for a hatch formed in a slab

A variable speed pumping up generator includes a first speed control unit for outputting a rotating speed command signal for controlling a pump turbine in accordance with a power output command and outputting an excitation control signal to an AC excitation unit of the generator, and a second speed control unit for controlling, in a generation mode, an amount of AC excitation from an AC excitation unit when a rotating speed of a rotary shaft departs from a lower limit setting or an upper limit setting. The setting is set in accordance with the rotating speed generated during a normal operation.

Variable speed pumping-up generator

A method of detecting a counterflow in a pump comprises providing with detecting means for detecting variations in the discharge pressure of the pump and signal analyzing means for analyzing oscillation components contained in an output signal from the pressure detecting means, and detecting the pump's operating point to have entered a counterflow characteristic operation region when a waveform of the detection signal generated in association with the variations in the discharge pressure of the pump exhibits a predetermined spectrum distribution. Further, when it is detected that the operating point enters a counterflow characteristic operation region, the escape from that region is performed by temporally throttling the guide vane and temporally increasing the rotating speed.

Method of counterflow through a pump and method of controlling the

A semiconductor power conversion system comprising a multiphase bridge circuit which includes semiconductor devices having a controllable firing function and a reverse blocking characteristic, a gate control circuit which gives firing commands to the semiconductor devices, a short circuiting switch in which switching devices having a controllable firing function and a reverse blocking characteristic are connected in parallel with a DC output side of the multiphase bridge circuit, and a protection control device for performing a control for protecting the multiphase bridge circuit. The protection control device includes a device for detecting a commutation failure of the multiphase bridge circuit, and a device in response to the detection of the commutation failure for producing a blocking command for blocking the firing of the semiconductor devices of the multiphase bridge circuit and producing a short-circuiting command for firing the switching device which is short-circuited which bypasses current of the commutation failure. The protection control device further includes a device for detecting ending of a short-circuit based on the ceasing of current conduction of the short circuiting switch and for halting the blocking of the firing of the semiconductor devices of the multiphase bridge circuit.

Fault protection for a multiphase bridge power converter

An improved electric power conversion system comprising a multi-phase bridge circuit composed of semiconductors such as thyristors and an associated firing circuit. It is so constructed that: if the AC input current Iac flowing in the bridge circuit is equal to or larger in value that the DC output current Idc flowing out of the bridge circuit, it will be decided than an inner defect or fault is caused, and possible expansion of inner defect will be prevented by disabling the firing circuit to extinguish the thyristors in the bridge circuit, and if the AC input current Iac is smaller than the DC output current Idc in value, the bridge is permitted to continue the operation of power conversion, thus eliminating unnecessary interruption which otherwise would be caused by exterior disturbances. Also, an improved electric power conversion system may be equipped with a device to prevent an adverse effect from being caused by abnormal rise of thyristors' temperature.

Semiconductor electric power conversion system enabling fault and/or

Method of controlling the operation of a pump in a pumping installation

The operation of a variable speed electric driven pump turbine is monitored continuously during pumping to detect the operation point of the pump turbine, and to prevent it from falling into a hump characteristic region, which is recognizable on a graph of total dynamic head versus flow rate. Stalling occurs in the hump characteristic region as a result of a partial reverse flow of the water with respect to the runner. When the operation point of the pump turbine approaches the hump characteristic region, a corrective action is taken that includes increasing the output level of the electric driven pump turbine to increase its rotating speed, temporarily.

Variable speed pumping-up system

An AC-excited generator/motor apparatus comprising; an AC-excited generator/motor having an armature mounting thereon; an armature winding connected to an AC power system and a rotor mounting thereon; and an exciting winding excited by an AC current. An exciting device for supplying a controlled AC exciting current to the exciting winding comprises; a device for calculating a real slip frequency based on a difference between the phase of an armature voltage appearing on the armature winding and the rotational phase of the rotor; and a device for controlling the exciting current supplied to the exciting winding from the exciting means in response to a deviation of the real slip frequency from a predetermined allowable range of slip frequencies so as to restore the real slip frequency within the allowable range of slip frequencies.

AC-excited generator/motor apparatus

A generator-motor apparatus with economical protection measures for use in a variable speed pumping-up electric power plant, having a main transformer, a secondary winding of which is coupled to an electric power system, a power system breaker connected to a primary winding of the main transformer, a syncronizing breaker connected in series with the power system breaker, a generator-motor, a rotor of which is mechanically coupled to the pump-turbine and an armature winding of which is connected to the power system through the synchronizing breaker, the power system breaker and the main transformer, and an excitation circuit, including a frequency converter for supplying a field winding of the generator-motor with AC voltage of the variable frequency and a converter transformer for feeding the converter, which is branched from a junction of the power system breaker and the synchronizing breaker.

Power system and synchronizing breakers for a variable speed generator

A variable speed hydro-power plant includes a pump turbine (2) having a S-shaped characteristics at the turbine operation. A current time turbine operating point is grasped on a turbine characteristics diagram of the pump turbine (2). A limit operation characteristics curve (nr) of the pump turbine (2) is formed in advance so as to not reach the S-shaped characteristics turbine operation region. A reach of the limit operation characteristics curve (nr) is detected, a rotating speed (N) of the pump turbine (2) is lowered. An inrush of the pump turbine (2) into the S-shaped characteristics turbine operation region is eliminated, so the continuation of a stable and reliable turbine operation can be guaranteed.

Control system for a variable speed hydro-power plant apparatus

Growing community of inventors

Osaka, Japan

Hiroto Nakagawa