Mitsubishi Electric Corporation

Kazuyori Tahata

Shuhei Fujiwara

Toshiyuki Fujii

Takuya Kajiyama

Ryosuke Uda

Kenji Kamei

Yoshiyuki Kono

Kunio Kikuchi

Hiroki Ito

Makoto Miyashita

Sho Tokoyoda

Shinji Tominaga

Shigeo Hayashi

Masatoshi Takeda

Takashi Inagaki

Kenichi Kuroda

Fuminori Nakamura

Masaki Hiratsuka

Masashi Shigemitsu

Shota Midorikawa

Shiken Ka

Yusaku Horinouchi

Toshinobu Takeda

Frederick Page

An electric power control system includes a plurality of power converters connected in parallel. Each power converter, among the plurality of power converters, converts a direct-current power of an electricity storage device connected to the power converter into an alternating-current power, and outputs the alternating-current power to the power system. The electric power control system further includes: a power generator simulation unit to simulate characteristics of the synchronous generator based on an aggregate active power to generate a phase of the alternating-current voltage; a signal generation unit to generate a control signal for the power converter, based on the phase of the alternating-current voltage. The power generator simulation unit generates a first angular frequency based on a first difference between the aggregate active power and a target value for the aggregate active power, and generates, based on the first angular frequency, the phase of the alternating-current voltage.

Electric power control system simulating a synchronous generator

A power conversion device includes a power converter including a plurality of arms each having a plurality of converter cells cascaded to each other. A control device includes an AC current controller to control AC current flowing between the power converter and an AC circuit and a circulating current controller to control circulating current flowing between the arms of the power converter. The AC current controller reduces an effective value or amplitude value of AC current in a discharge operation mode in which a voltage of a power storage element of each converter cell is discharged, compared with in a normal operation mode. The circulating current controller increases an effective value or amplitude value of circulating current in the discharge operation mode, compared with in the normal operation mode.

Power conversion device

A power storage apparatus of one embodiment includes a storage bank including a plurality of power storage elements connected to each other; and one or plurality of first cells. The storage bank and the one or plurality of first cells are connected in series to each other. Each first cell includes a pair of input/output nodes, a bridge circuit including at least two semiconductor switching elements, and a power storage element connected to the pair of input/output nodes via the bridge circuit. A storage capacity of the power storage element of each first cell is smaller than a storage capacity of the storage bank.

Power storage apparatus and power system stabilization system

A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element, and a pair of output terminals. A control device controls voltages of the plurality of converter cells by phase shift PWM control using a carrier signal for each converter cell. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell within the arm, it has a failed converter cell within the arm bypassed and rectifies uneven intervals among phases of carrier signals of a plurality of normal converter cells within the arm caused by failure of the converter cell.

Power conversion device capable of suppressing a harmonic component in an output voltage from an arm that increases after bypass of a failed converter cell

A power conversion device includes a power converter including a plurality of arms and a control device to control voltages of a plurality of sub modules by PWM control using a carrier signal for each sub module. The sub module includes a plurality of switching elements, a power storage element, a pair of output terminals, and a bypass switch. When the control device detects failure of a sub module in an arm, it performs stop processing for stopping a switching operation of the plurality of switching elements included in at least one sub module of the plurality of sub modules in the arm and has the sub module failure of which was detected bypassed. After the control device performs the stop processing, it equalizes intervals among phases of carrier signals of a plurality of normal sub modules in the arm caused by failure of the sub module.

A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element, and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell within the arm bypassed and controls a normal converter cell within the arm to suppress a ratio of a harmonic component in an arm current that increases due to the failure.

A power conversion system includes: a self-excited power converter to perform power conversion between a first AC system and a DC system; a first transformer having a primary side connected to the first AC system and a secondary side connected to the self-excited power converter; and a first impedance circuit connected between a ground and a neutral point on the secondary side of the first transformer, or between the ground and an AC line connecting the secondary side of the first transformer and the self-excited power converter. The first impedance circuit includes one of a reactor and another transformer.

Power conversion system

A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell bypassed, estimates an output voltage lost by bypassing the failed converter cell, and has a normal converter cell supply the estimated output voltage of the failed converter cell.

A control device for controlling a power source connected to an alternating-current (AC) power system includes: a frequency control unit that controls a frequency of the power source operating in a constant-voltage constant-frequency control scheme; a power calculation unit that calculates, when the frequency control unit varies a frequency of the power source, a variation of an effective power output from the power source; an arithmetic unit that calculates a frequency characteristics constant of the AC power system, based on a variation of the frequency of the power source and the variation of the effective power output from the power source; and a selection unit that selects a control scheme for the power source, based on the frequency characteristics constant of the AC power system.

Control device and power control system

A power conversion device includes power conversion circuitry including a plurality of submodules connected in series to each other. The power conversion device further includes: a signal reception unit configured to receive a signal representing a voltage of a capacitor in each of the submodules; a time calculation unit configured to calculate at least one of a charging time of the capacitor and a discharging time of the capacitor based on the signal; and a determination unit configured to determine whether the capacitor has degraded or not based on at least one of a first result of comparison of the charging time with a reference charging time serving as a reference for determining degradation of the capacitor, and a second result of comparison of the discharging time with a reference discharging time serving as a reference for determining degradation of the capacitor.

Modular multilevel converter having capacitor degradation determination

A direct-current circuit includes: a breaker that is inserted into the direct-current line and becomes a path for direct current when in a steady state; a resonance circuit connected in parallel with the breaker and superimposing resonance current on the direct current; and a first disconnector and a second disconnector connected to first and second connection points of the breaker and the resonance circuit, respectively, and forming a path for the direct current together with the breaker. The resonance circuit includes a series circuit that includes a capacitor and a reactor and generates the resonance current, a charging resistor for charging the capacitor with a direct-current potential of the direct-current line, a high-speed switch connected in series with the series circuit on the capacitor side and superimposing the resonance current on the direct current, and an arrester connected in parallel with the capacitor and the high-speed switch.

Direct-current circuit breaker

A wind power generation system according to the present invention includes: a DC bus; a plurality of feeders connected to the DC bus for transmitting DC powers to the DC bus; a plurality of wind power generators; a plurality of AC/DC converters connected one by one to each of the wind power generators for converting AC powers generated by the connected wind power generators, into DC powers, and outputting the DC powers to the feeders; and a DC breaker and a diode, which serve as a current limiting unit installed on each of the feeders for preventing a DC current from flowing from the DC bus into the feeder.

Wind power generation system and DC power transmission system

An AC circuit breaker is provided between an AC system and an AC-DC converter, and a DC circuit breaker is provided between a DC line and the AC-DC converter. A bypass switch capable of short-circuiting a converter cell included in the AC-DC converter is connected to the AC-DC converter. At the time of a fault in the DC line, the bypass switch is turned on to interrupt the supply of DC power from the AC system to the DC line.

Protection system for DC power transmission system, AC-DC converter, and method of interrupting DC power transmission system

A direct-current circuit breaker includes a switching unit inserted in the direct-current line; and a commutation circuit that includes a series circuit including a first current-limiting element and an interrupting unit that forms a current zero point by superimposing a resonance current on a direct current flowing in the direct-current line and interrupts the direct current at the current zero point, that is connected in parallel with the switching unit, and that becomes a flow path for the direct current after the switching unit is opened, wherein current interruption is performed by the interrupting unit after the switching unit is opened.

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Tokyo, Japan

Kazuyori Tahata