Hitachi, Ltd.

Hitachi Construction Machinery Co., Ltd.

Hitachi Vlsi Engineering Corp.

Hitachi Information & Telecommunication Engineering, Ltd.

Akira Kikuchi

Motoo Futami

Kouichi Miyazaki

Tomohiko Yasuda

Masaya Ichinose

Mitsugu Matsutake

Naoshi Sugawara

Kichio Nakajima

Takayuki Sato

Keizo Shimada

Takashi Ikimi

Hironari Kawazoe

Hiroyuki Kobayashi

Masahiro Watanabe

Shinjiro Saito

Toshikazu Minoshima

Yasuyuki Sugiura

Yasuhiro Imazu

Yoshio Eguchi

Masatoshi Kumagai

Fumikazu Takahashi

Tomomichi Ito

Yasuhiro Kiyofuji

Yuki Tsujii

Kazuhiro Imaie

Kimiaki Taniguchi

Takayuki Satou

Tomoyuki Hatakeyama

Akihiro Tomozawa

Kenedward Kawakita

Kensuke Nakata

Mitsumasa Satoo

Takashi Agastuma

Hirofumi Oyamada

Chia Tse Lee

Tetsuhiro Fujimoto

Koji Imazawa

The purpose of the present invention is to provide a power flow monitoring device for a power system, a power system stabilization device, and a power flow monitoring method for a power system, which are highly reliable and accurate. The present invention is characterized by being provided with: a power system information database which stores measurement data obtained at a first node of the power system; a phase measurement value database which stores temporally synchronized phase measurement data obtained at a second node of the power system; a fault condition database which stores a power flow state under an assumed fault condition of the power system; a state estimation unit which estimates a state quantity of the power system using information in the power system information database as an input; a stability error detection index calculation unit which calculates a stability error detection index using, as an input, a state quantity estimation value which is an output of the state estimation unit, information of the state quantity from the phase measurement value database, and information in the fault condition database; and an error detection alert generation unit which compares the stability error detection index with a threshold value thereof and generates an alert when the stability error detection index exceeds the threshold value, wherein the magnitude of deviation of the state quantity estimation value with respect to the information of the state quantity from the phase measurement data is evaluated according to the assumed fault condition before the alert is generated.

Power flow monitoring device for power system, power system stabilization device, and power flow monitoring method for power system

An apparatus includes: an inverter converting generated power of renewable energy resources to predetermined alternating-current power for output to a power transmission network; a PWM control unit controlling the inverter; a first detecting unit detecting the input voltage and current to the inverter; a second detecting unit detecting the output voltage, current, and frequency of the inverter; a power change deciding unit calculating the input and output powers of the inverter and the difference therebetween from the voltage and current of each of the input and output detected by the detecting units, and calculating a correction output power command with reference to an output power command; and a virtual synchronous inertia control unit calculating a virtual inertia characteristic based on the voltage, current, and frequency of the output detected by the second detecting unit and the correction output power command, and outputting a reference command to a PWM control unit.

Renewable energy resources integrating power conversion apparatus

Providing a power system and a method for stabilizing a system, in which the number of generators to be disconnected is reduced to narrow an area influenced by a grid fault in the case where the reliability of the state estimation calculation is judged to be high. The power system stabilizing method applied to a power system configured to include a plurality of feeders including circuit breakers, a plurality of nodes, a plurality of generators, and a plurality of loads, in which method: a protection relay detects a grid fault by using an output from a first sensor installed close to the circuit breaker, thereby opening-controlling the circuit breaker, and the circuit breaker is opening-controlled by a power system stabilization output; a state estimation value of a power system obtained by using the first sensor output and a state detection value, of the power system, containing information associated with measurement time measured in the power system are compared with each other to judge reliability of the state estimation value; the circuit breaker which is to be newly cut off from a viewpoint of power system stability after occurrence of a grid fault at a supposed grid fault point of the power system is stored, and the circuit breaker which is to be cut off every reliability judgment result of the state estimation value is stored; and at the time of occurrence of a grid fault of the power system, a turn-off command for the circuit breaker which is selected in response to the reliability judgment result of the state estimation value so as to be newly cut off is set as the power system stabilization output.

System and method for stabilizing power system

A power conversion system is capable of distinguishing easily and clearly between being interconnected to the power system and being in an isolated operation. The power conversion system converts DC power to AC power to interconnect with a power system and injects reactive power into a grid node for determining an isolated operation, including: a voltage detector that detects an output voltage at the grid node; a current detector that detects an output current at the grid node; a frequency measurement unit that measures a frequency of the output voltage at the grid node; a reactive-power measurement unit that measures reactive power at the grid node; and an isolated-operation determination unit that determines whether or not the power conversion system is in an isolated operation as disconnected from the power system. The isolated-operation determination unit includes a reactive-power-fluctuation determination unit that performs a first isolated-operation determination from the reactive power.

Power conversion system and method for detecting isolated operation of the same

An operation management system obviates such a situation that a power substation would trip and a supply of power to overhead wires would stop. The operation management system controls operation of electric drive vehicles, each of which is provided with a trolley mode, in which the electric drive vehicle runs by power supplied to the overhead wires, and a diesel mode, in which the electric drive vehicle runs by an output from an engine. A supply margin detection unit detects a current supply margin of power and a running position detecting unit detects a current running position of the electric drive vehicle. A running mode detection unit detects a current running mode of the electric drive vehicle and a running mode determination unit determines a next running mode based on the detection results of the supply margin detection unit, running position detecting unit, and running mode detection unit.

Operation management system

Provided is an electric drive vehicle which can control wheel speed so as to achieve an appropriate slip ratio of the wheels even when pitching vibration of the vehicle is large. This electric drive vehicle is provided with electric motors (), drive wheels (), driven wheels (), an electric motor controller () for controlling the electric motors, and speed detectors (-) for detecting the wheel speed of the drive wheels and the driven wheels. The electric motor controller is provided with: a slip ratio calculation unit () which calculates the slip ratio of the drive wheels from the wheel speed detected values detected by the speed detectors; a torque command calculation unit () which calculates torque commands for the drive wheels; a drive force calculation unit () which, from the wheel speed detected values of the drive wheels and the torque commands of the drive wheels, calculates the drive force generated in the drive wheels; and filters () which reduce the pitching vibration frequency components of the vehicle included in the slip ratio and the drive force.

Electric drive vehicle

Provided is an electrically driven vehicle that is capable of suppressing drive wheel slippage without increasing the pitching vibration of the vehicle. The electrically driven vehicle having electric motors (), drive wheels () driven by the electric motors respectively, and, when at least one of the drive wheels slips, an electric motor control device () for reducing the torque of at least one of the electric motors that drives the at least one wheel slipped, and for restoring the torque of the at least one electric motor when the slippage is stopped includes a pitching detection device () for detecting the amplitude of pitching vibration to which the vehicle is subjected. The amount of torque of the at least one electric motor to be restored by the electric motor control device over a predetermined period of time after the slippage is stopped varies depending on whether or not the amplitude A detected by the pitching detection device is greater than an assessment value A

Electrically driven vehicle

An electrically driven vehicle equipped with electric motors () for driving or braking drive wheels (), and an electric motor controller () for controlling the electric motors includes: wheel speed detectors (to) for detecting the wheel speed of the drive wheels and that of idler wheels (); computing means (toto) for computing the slip ratio of the drive wheels based on the wheel speed of the drive wheels and that of the idler wheels; and a determiner () for determining that the drive wheels are slipping if the slip ratio exceeds a slip ratio determination value. If the wheel speed of the idler wheels is lower than set speeds Va, Vb, then the determiner () changes the slip ratio determination value to a value having as the same sign as, and a larger absolute value than, the values &#x3bb;a, &#x3bb;bused when the wheel speed of the idler wheels is higher than the set speeds Va, Vb. This structure shortens acceleration time during acceleration traveling and reduces braking distance during deceleration traveling while inhibiting vibrations of the electrically driven vehicle.

An electric drive vehicle having an induction motor for braking or driving wheels, a motor controller for controlling the induction motor, and mechanical brakes for braking the wheels, wherein while the vehicle is in halt in a state that the mechanical breaks are not operating, the motor controller applies DC voltage or AC voltage in a frequency range of &#x2212;1 Hz to +1 Hz to the stator of the induction motor to make the induction motor generate torque for stopping the vehicle and maintain the vehicle in a halt state.

A wind turbine generator system can regulate the rotational velocity of the wind turbine within an operation range even when the wind velocity suddenly changes and can perform continuous operation of the wind turbine. The wind turbine generator system includes a generator connected to the shaft of the wind turbine and a converter connected to the generator. When the rotational velocity of the wind turbine is within a predetermined range, power outputted from the generator is controlled so as to follow the instruction concerning the generator output given from the wind turbine to the converter. When the rotational velocity of the wind turbine is out of the predetermined range, the power outputted from the generator is controlled without following the instruction concerning generator output given from the wind turbine to the converter.

Wind turbine generator system

A vehicle which evaluates tire wear properly even in a road condition that tires easily slip or lock up. The vehicle, which has a driven wheel and a driving wheel with tires attached thereto, includes: a revolution speed detector for detecting revolution speeds of the driven and driving wheels; a wheel speed detector for detecting wheel speeds of the driven and driving wheels based on the detected revolution speed data of the driven and driving wheels; a wheel speed ratio detector for detecting a wheel speed ratio between the driven and driving wheels based on the detected wheel speed data of the driven and driving wheels; and a tire condition evaluator for outputting an evaluation result indicating that the tire(s) attached to the driven wheel and/or driving wheel is(are) worn when the wheel speed ratio is higher than a preset threshold.

Vehicle having tire wear evaluation system

An electric drive vehicle having a power generator coupled to an engine, a first power converter connected with the power generator for converting the AC power generated by the power generator to DC power, a second power converter connected with the first power converter, for converting the DC power to AC power, a power consuming device for consuming the DC power, connected to a DC circuit between the first and second power converters, an electric motor connected with the second power converter, and at least one wheel driven by the electric motor, wherein the vehicle has a first control mode for controlling the output of the electric motor and a second control mode for controlling the power consumed by the power consuming device, and the second control mode performs such control that the operations of the second power converter and the electric motor in the first control mode are simulated.

An electric motor control system including a generator, an AC motor, a power converter for driving the AC motor using a DC output voltage of the generator, and an electric motor controller for controlling the power converter. The electric motor controller controls the power converter by predicting a change in the DC voltage.

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Hitachi, Japan

Akira Kikuchi