Abstract: A power conversion device includes, for respective phases of an AC circuit, leg circuits each having a pair of arms connected in series to each other, each arm including a plurality of converter cells which are connected in series and each of which has an energy storage element. A controlling circuitry includes a zero-phase-sequence voltage command value adjustment unit for correcting arm voltage command values for the arms by a zero-phase-sequence voltage command value. The command value correction circuitry performs adjustment control for adjusting the zero-phase-sequence voltage command value so that at least one arm voltage command value becomes equivalent to a limit value of the output voltage range of the arm.

Abstract: A first voltage control circuitry controls a first representative value, i.e., an average-value corresponding value of DC capacitor voltages of all converter cells to follow an overall voltage command value. A phase balance control circuitry controls second representative values, i.e., average-value corresponding values of DC capacitor voltages of the converter cells in leg circuits for respective phases to follow the first representative value. A positive-negative balance control circuitry controls deviations of third representative values, i.e., average-value corresponding values of the DC capacitor voltages of the converter cells in the positive and negative arms of the leg circuits for respective phases to become zero between the positive and negative arms. An individual balance control circuitry controls DC capacitor voltages of all the converter cells to follow the third representative values.

Abstract: A management apparatus periodically transmits information for setting a first voltage range and a second voltage range smaller than the first voltage range to a distribution power supply apparatus. The distribution power supply apparatus removes, from an interconnection point voltage at an interconnection point with the distribution system, a voltage fluctuation component with a cycle shorter than a cycle in which the information is transmitted from the management apparatus to thereby generate a voltage command value of the interconnection point, and performs reactive power control for eliminating a voltage deviation of the interconnection point voltage with respect to the voltage command value. In the reactive power control, the generation of the reactive power is started when an absolute value of the voltage deviation exceeds the first voltage range, and the reactive power is adjusted until the absolute value falls below the second voltage range.

Abstract: A power converter includes two arms for each phase between DC terminals, and each arm is formed by connecting a plurality of converter cells in series. A control device includes an arm voltage command generation unit which generates, for each arm, an arm voltage command for the plurality of converter cells. The arm voltage command is generated by superimposing a zero-phase-sequence voltage command having a frequency component that is three times an AC fundamental frequency. Phase adjustment of the zero-phase-sequence voltage command is performed on the basis of voltage of a DC capacitor in the converter cell and the arm voltage command.

Abstract: A power conversion device includes, for respective phases of an AC circuit, leg circuits each having a pair of arms connected in series to each other, each arm including a plurality of converter cells which are connected in series and each of which has an energy storage element. A controlling circuitry includes a zero-phase-sequence voltage command value adjustment unit for correcting arm voltage command values for the arms by a zero-phase-sequence voltage command value. The command value correction circuitry performs adjustment control for adjusting the zero-phase-sequence voltage command value so that at least one arm voltage command value becomes equivalent to a limit value of the output voltage range of the arm.

Abstract: A subtracting unit calculates a voltage deviation of an output voltage of a DC-to-DC converter from a target voltage. A feedback control variable calculator calculates a feedback control variable in each control cycle. In a control cycle in which a crossing of the output voltage and the target voltage is detected by a feedforward control determination unit, a feedforward control variable calculator calculates a feedforward control variable so that a change in the output voltage is prevented. A switching control signal generator generates a control signal for the DC-to-DC converter for controlling the output voltage, according to a summation of the feedforward control variable and the feedback control variable.

Abstract: A power conversion device includes: a power converter circuit which converts a direct-current power, output from a decentralized power supply, into an alternating-current power, and outputs the alternating-current power to a power distribution grid; a voltage target value generation unit which removes a high-frequency variation from a root mean square of a voltage detected by a voltage detection unit to generate a voltage target value; a correction unit which corrects the voltage target value when the correction unit detects that the automatic voltage regulator has performed an action; and a command unit which, if the voltage at the point of interconnection detected by the voltage detection unit deviates from a voltage control deadband referenced to the voltage target value, commands the power converter circuit to output a reactive power based on a magnitude of the deviated amount of voltage.

Abstract: An AC/DC converter and a DC/DC converter are disposed corresponding to a power generator. The AC/DC converter converts AC power generated by the power generator into a generated voltage, and outputs the generated voltage to a power line. The DC/DC converter converts the generated voltage on the power line into a collection voltage, and outputs the collection voltage to a collection line. DC power in a DC voltage grid formed of the collection line is transmitted through a DC/AC converter to an AC power grid. When a short-circuit fault occurs in the DC power grid or the AC power grid, a control command value for the AC/DC converter or the DC/DC converter is adjusted so as to suppress incoming electric power flowing from the power generator in accordance with fluctuations of a collection voltage.

Abstract: A power conversion device includes: a power converter circuit which converts a direct-current power, output from a decentralized power supply, into an alternating-current power, and outputs the alternating-current power to a power distribution grid; a voltage target value generation unit which removes a high-frequency variation from a root mean square of a voltage detected by a voltage detection unit to generate a voltage target value; a correction unit which corrects the voltage target value when the correction unit detects that the automatic voltage regulator has performed an action; and a command unit which, if the voltage at the point of interconnection detected by the voltage detection unit deviates from a voltage control deadband referenced to the voltage target value, commands the power converter circuit to output a reactive power based on a magnitude of the deviated amount of voltage.

Abstract: A management apparatus periodically transmits information for setting a first voltage range and a second voltage range smaller than the first voltage range to a distribution power supply apparatus. The distribution power supply apparatus removes, from an interconnection point voltage at an interconnection point with the distribution system, a voltage fluctuation component with a cycle shorter than a cycle in which the information is transmitted from the management apparatus to thereby generate a voltage command value of the interconnection point, and performs reactive power control for eliminating a voltage deviation of the interconnection point voltage with respect to the voltage command value. In the reactive power control, the generation of the reactive power is started when an absolute value of the voltage deviation exceeds the first voltage range, and the reactive power is adjusted until the absolute value falls below the second voltage range.

Abstract: A DC transmission system transmits AC power generated by a generator to an AC distribution grid and a DC distribution grid using DC power. The DC transmission system includes an AC/DC converter, a DC/DC converter, and a DC/AC converter. The AC/DC converter outputs DC power by converting AC power from the generator. The DC/DC converter boosts a first voltage of the DC power outputted from the AC/DC converter, into a second voltage. The DC/AC converter outputs, to the AC distribution grid, AC power by converting the DC power outputted from the DC/DC converter. When the second voltage changes, the DC/DC converter controls the first voltage in response to the change in the second voltage.

Abstract: An AC/DC converter and a DC/DC converter are disposed corresponding to a power generator. The AC/DC converter converts AC power generated by the power generator into a generated voltage, and outputs the generated voltage to a power line. The DC/DC converter converts the generated voltage on the power line into a collection voltage, and outputs the collection voltage to a collection line. DC power in a DC voltage grid formed of the collection line is transmitted through a DC/AC converter to an AC power grid. When a short-circuit fault occurs in the DC power grid or the AC power grid a control command value for the AC/DC converter or the DC/DC converter is adjusted so as to suppress incoming electric power flowing from the power generator in accordance with fluctuations of a collection voltage.

Abstract: A subtracting unit calculates a voltage deviation of an output voltage of a DC-to-DC converter from a target voltage. A feedback control variable calculator calculates a feedback control variable in each control cycle. In a control cycle in which a crossing of the output voltage and the target voltage is detected by a feedforward control determination unit, a feedforward control variable calculator calculates a feedforward control variable so that a change in the output voltage is prevented. A switching control signal generator generates a control signal for the DC-to-DC converter for controlling the output voltage, according to a summation of the feedforward control variable and the feedback control variable.

Abstract: In a power conversion system in which self-excitation-type power conversion devices performing bidirectional power conversion are mutually interconnected by direct current, when the power conversion device serving for power transmission is stopped, in the first power conversion device, a DC capacitor voltage control unit calculates a current amount for compensating capacitor voltage in accordance with voltage variation in a DC capacitor. A high-voltage-side DC current control unit determines that an electricity amount supplied from a power supply system to the first power conversion device is a predetermined value or higher, and subtracts the current amount for compensating the capacitor voltage from a DC current command value. Thus, while the DC voltage is kept to be constant, the power flow direction is changed and power transmission to a second DC system is continued.

Abstract: In a power conversion system in which self-excitation-type power conversion devices performing bidirectional power conversion are mutually interconnected by direct current, when the power conversion device serving for power transmission is stopped, in the first power conversion device, a DC capacitor voltage control unit calculates a current amount for compensating capacitor voltage in accordance with voltage variation in a DC capacitor. A high-voltage-side DC current control unit determines that an electricity amount supplied from a power supply system to the first power conversion device is a predetermined value or higher, and subtracts the current amount for compensating the capacitor voltage from a DC current command value. Thus, while the DC voltage is kept to be constant, the power flow direction is changed and power transmission to a second DC system is continued.

Abstract: A DC transmission system transmits AC power generated by a generator to an AC distribution grid and a DC distribution grid using DC power. The DC transmission system includes an AC/DC converter, a DC/DC converter, and a DC/AC converter. The AC/DC converter outputs DC power by converting AC power from the generator. The DC/DC converter boosts a first voltage of the DC power outputted from the AC/DC converter, into a second voltage. The DC/AC converter outputs, to the AC distribution grid, AC power by converting the DC power outputted from the DC/DC converter. When the second voltage changes, the DC/DC converter controls the first voltage in response to the change in the second voltage.

Abstract: 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.

Abstract: 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.