Mitsubishi Electric Corporation

Toshiba Mitsubishi-electric Industrial Systems Corporation

Tmeic Corporation

Kaho Mukunoki

Toshiyuki Fujii

Osamu Mori

Shinzo Tamai

Yasuhiko Hosokawa

Sadao Funahashi

Kotaro Higashi

Ryosuke Uda

Taichiro Tsuchiya

Akihiro Matsuda

Hisanori Taguchi

Takeshi Kikuchi

Takuya Kajiyama

Ryota Okuyama

Takushi Jimichi

Hiroki Ishihara

Miwako Tanaka

Kota Hamanaka

A reactive power compensation device includes a power converter and a converter control unit, and compensates reactive power of an AC power grid by output reactive power of the power converter. The converter control unit includes an AC voltage detection unit and an output limit unit. The AC voltage detection unit detects voltage information of the AC power grid to which the power converter is connected. The output limit unit determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the voltage information detected by the AC voltage detection unit, and in a case where the output reactive power needs to be limited, limits the output reactive power of the power converter.

Reactive power compensation device

A power conversion device includes a power converter connected to a power storage element, and a control device. The control device includes a generator simulating unit to generate a voltage command value, and a signal generating unit to generate a control signal for the power converter based on the voltage command value. The generator simulating unit includes a first characteristics simulating unit to generate a first command value by simulating characteristics of a first synchronous generator, a second characteristics simulating unit to generate a second command value by simulating characteristics of a second synchronous generator different from the characteristics of the first synchronous generator, an adder to perform addition of the first command value and the second command value, and a voltage command generating unit to generate the voltage command value, based on an addition result of the first command value and the second command value.

Power conversion device

A power conversion device includes a voltage-type power converter and a current-type power converter each of which performs power conversion between AC and DC, and a controlling circuitry, and power is transmitted/received between AC sides via a DC circuit. In first starting control for starting the voltage-type power converter and the current-type power converter, the controlling circuitry controls a semiconductor element of at least one of the voltage-type power converter and the current-type power converter, to adjust DC voltage at DC terminals of the voltage-type converter to a set first voltage value, thereby controlling current flowing through the DC circuit to be first current not greater than a rated current value of the semiconductor elements.

Power conversion device preventing overcurrent at the time of starting

A power conversion device which is connected between an electric generation grid and a demand area grid and performs power conversion includes: a power converter which is connected to an electric generation grid and which converts AC power received from the electric generation grid to DC power and transmits the DC power via DC bus; and a control device for controlling the power converter. The control device includes a detection unit for detecting DC current of the DC bus, and a protection control unit for performing protection control for suppressing an amount of power received from the electric generation grid, on the basis of variation in the DC current, thereby continuing operation in the case of disturbance in the demand area grid.

Power conversion device and power system performing protection control for suppressing received power

A control device generates a voltage command value for controlling a current flowing between a three-phase AC power supply and a power converter such that a full voltage representative value representing voltage values of all power storage devices agrees with a DC voltage command value. The control device generates a zero-phase voltage command value for controlling a circulating current flowing in a delta connection such that the voltage values of the power storage devices are balanced among first to third arms. The control device combines the voltage command value and the zero-phase current command value to generate an output voltage command value for controlling an output voltage of each unit converter. The control device removes a control amount of the full voltage representative value from a computation of the zero-phase voltage command value to cause output current control and circulating current control not to interfere with each other.

Power conversion apparatus for interconnection with a three-phrase ac power supply

A DC power transmission system interconnects a plurality of AC systems via a DC line. A plurality of power conversion devices are connected between the plurality of AC systems and the DC line. One of the plurality of power conversion devices controls the voltage on the DC line, while the remaining power conversion device controls a current input and output to and from the DC line. In a restart which resumes power conversion from a stopped state for controlling a DC current on the DC line, the power conversion device performing current control monitors the voltage on the DC line and starts a restart operation without transmitting or receiving information to or from the other power conversion device.

Power conversion device and DC power transmission system

Since a power converter including a modular multilevel converter uses a large number of cells each combining a plurality of switching elements and a DC capacitor, there is a problem of conduction loss due to the switching elements. The conduction loss is reduced by connecting a bypass circuit between terminals of each of the cells, controlling to open and close the switching element, and controlling to short-circuit the bypass circuit connected to the cell controlled to output zero voltage.

Power converter

The present invention is provided with a power converter and a control device for controlling the power converter, wherein each of the positive arm and the negative arm is comprised one converter cell or a plurality of converter cells connected in series, each converter cell being comprised: a series unit in which a plurality of switching elements are connected in series to each other; and a DC capacitor connected in parallel to the series unit, and the control device includes a DC voltage command value calculation unit which calculates a voltage command value for outputting, during a DC short circuit fault, AC voltage similar to that in a steady state to the AC terminal of the power converter, and for outputting, to the DC terminal of the power converter, DC voltage that allows the protection relay in the DC line to operate.

When switching operations of converter cells are stopped due to temporary voltage reduction in an AC system, a voltage determination unit performs determination regarding a voltage of each DC capacitor after a predetermined period has passed, and a charge control unit transmits a charging gate signal, via a gate control unit, to select a converter cell at a voltage level at which a self-feeding circuit of the converter cell is operable. Thus, a DC capacitor of a converter cell whose voltage is lower than the voltage level at which a self-feeding circuit is operable is charged, thereby enabling switching operations of all the converter cells.

A power conversion device includes: a positive arm and a negative arm each of which is formed by connecting a plurality of converter cells in series, the converter cells each being composed of a plurality of semiconductor switching elements and a DC capacitor; and a control circuit. An arm balance control unit in the control circuit calculates a first voltage adjustment value for balancing voltage of the DC capacitors in the positive arm and voltage of the DC capacitors in the negative arm. The control circuit adjusts an AC control command using the first voltage adjustment value, thereby calculating an AC voltage command for AC voltage to be outputted to an AC line for each phase.

In a power conversion system in which one or more converter cells are connected in series to form an arm for each phase, a control device includes a voltage command generating unit for generating a positive arm voltage command and a negative arm voltage command for each phase. The voltage command generating unit includes an AC current control unit, a circulating current control unit, and a command distributing unit. On the basis of inputted voltage commands, the command distributing unit subtracts voltage drop portions due to inductance values in the arms from respective voltages assigned as outputs of the positive arm and the negative arm, to distribute voltage components, thereby determining the positive arm voltage command and the negative arm voltage command.

Power conversion system

A power conversion device performs power conversion between three-phase AC, and DC, and includes a positive arm and a negative arm for each phase, each of which includes one or more converter cells connected in series. A voltage command generating unit in a control device includes an AC current control unit, a circulating current control unit, and a command distributing unit, and generates a positive arm voltage command and a negative arm voltage command for each phase. In the circulating current control unit, a compensator calculates a first control command so that circulating current for each phase approaches a circulating current command value, a suppression unit generates a second control command so as to suppress a 2f component and a 4f component contained in the first control command, and then the first control command and the second control command are combined to generate a circulation control command.

In a power converter which performs power conversion between plural-phase AC and DC, variation in voltage of the DC capacitor in each converter cell is detected, and when the variation exceeds a predetermined value, a DC voltage command value as a control target value in a DC voltage control unit which controls DC voltage between DC buses is corrected by being increased or decreased. Thus, when AC grid failure occurs, the capacitor voltage of each converter cell is maintained and the operation continuity is improved.

Direct-current power transmission power conversion device and direct-current power transmission power conversion method

An electric power conversion device includes a power conversion unit and a converter control unit. The power conversion unit includes three arms connected to an AC circuit. The converter control unit includes a phase DC voltage control unit, a negative sequence current command value calculation unit, an output current control unit, a circulating current control unit, a voltage command value calculation unit, and a gate signal generation unit, and imbalance of cell DC capacitor voltages among phases due to grid imbalance is controlled by circulating current and negative sequence current.

Electric power conversion device

A power conversion device includes: a DC current calculation unit for calculating a circulating current component for each phase which circulates between the phases through first arms and/or second arms not via an AC power supply and a DC power supply; and a circulating current control unit for controlling the circulating current component for each phase so as to follow a predetermined circulating current command value, thereby reliably suppressing variation in voltages of DC capacitors of unit cells among the phases even in such a case where an impedance is additionally inserted in a DC circuit.

Growing community of inventors

Chiyoda-ku, Japan

Kaho Mukunoki