# US 2023/0411963 A1 · Reactive power compensation device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0411963 A1 - Document ID: US20230411963A1 - Status: Published application - Kind: A1 - Application number: 18/031,010 - Filed: 2020-10-21 - Published: 2023-12-21 - Earliest claimed: 2020-10-21 - Assignees: Mitsubishi Electric Corporation; Toshiba Mitsubishi-Electric Industrial Systems Corporation - Applicants: Mitsubishi Electric Corporation; Toshiba Mitsubishi-Electric Industrial Systems Corporation - Inventors: Kaho MUKUNOKI; Toshiyuki FUJII; Akihiro MATSUDA; Ryota OKUYAMA - Web page: https://patentgrep.com/patent/US20230411963A1 ## CPC - H02J 3/1857: the bridge converters being multilevel bridge converters or modular multilevel converters - G05F 1/70: Regulating power factor; Regulating reactive current or power - H02J 3/16: by adjustment of reactive power - H02J 3/1864: using reactive elements connected in series with semiconductor switches, e.g. static VAR compensators [SVC], thyristor-controlled reactors [TCR] or thyristor-switched capacitors [TSC] - Y02E 40/30: Reactive power compensation - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract 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. ## Claims ### Claim 1 A reactive power compensation device comprising: a power converter connected to an AC power grid with a plurality of phases, and having a self-turn-off switching element; and a converter control circuitry which controls the switching element of the power converter, wherein reactive power of the AC power grid is compensated by output reactive power of the power converter, the converter control circuitry includes an AC voltage detection circuitry and an output limit circuitry, the AC voltage detection circuitry detects voltage information of the AC power grid to which the power converter is connected, and the output limit circuitry 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 circuitry, and in a case where the output reactive power needs to be limited, limits the output reactive power of the power converter. ### Claim 2 (depends on 1) The reactive power compensation device according to claim 1, wherein in the case where the output reactive power needs to be limited, the output limit circuitry limits the output reactive power of the power converter so that output voltage of the power converter is kept within an output possible range of the power converter. ### Claim 3 (depends on 1) The reactive power compensation device according to claim 1, wherein in the case where the output reactive power of the power converter needs to be limited, the output limit circuitry limits output reactive current of the power converter. ### Claim 4 (depends on 3) The reactive power compensation device according to claim 3, wherein the AC voltage detection circuitry includes a positive-phase-sequence voltage detection circuitry for detecting positive-phase-sequence voltage of grid voltage of the AC power grid, and calculates a reactive current reference value on the basis of the positive-phase-sequence voltage detected by the positive-phase-sequence voltage detection circuitry and a voltage command value for the power converter, and the output limit circuitry subtracts a reactive current subtraction amount from the reactive current reference value, to calculate a reactive current command value, thus limiting the output reactive current of the power converter. ### Claim 5 (depends on 4) The reactive power compensation device according to claim 4, wherein the output limit circuitry subtracts the reactive current subtraction amount set in advance on the basis of an impedance of the AC power grid, from the reactive current reference value, to calculate the reactive current command value, thus limiting the output reactive current of the power converter. ### Claim 6 (depends on 1) The reactive power compensation device according to claim 1, wherein the AC voltage detection circuitry detects magnitudes of voltages for the respective phases of grid voltage of the AC power grid, and the output limit circuitry calculates a maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, and determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the maximum value among the magnitudes of the voltages for the respective phases. ### Claim 7 (depends on 6) The reactive power compensation device according to claim 6, wherein the output limit circuitry calculates the maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, calculates a deviation between the maximum value and a predetermined voltage maximum allowable value, and calculates a reactive current subtraction amount for reducing the deviation, thus limiting output reactive current of the power converter. ### Claim 8 (depends on 6) The reactive power compensation device according to claim 6, wherein the output limit circuitry calculates the maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, calculates a deviation between the maximum value and a predetermined voltage maximum allowable value, and calculates a reactive power subtraction amount for reducing the deviation, thus limiting output reactive current of the power converter. ### Claim 9 (depends on 1) The reactive power compensation device according to claim 1, wherein the AC voltage detection circuitry includes a positive-phase-sequence voltage detection circuitry for detecting positive-phase-sequence voltage of grid voltage of the AC power grid, a negative-phase-sequence voltage detection circuitry for detecting negative-phase-sequence voltage of the grid voltage of the AC power grid, and an unbalance factor detection circuitry for calculating an unbalance factor which is a ratio of the negative-phase-sequence voltage to the positive-phase-sequence voltage, and the output limit circuitry determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the unbalance factor calculated by the unbalance factor detection unit. ### Claim 10 (depends on 9) The reactive power compensation device according to claim 9, wherein the output limit circuitry calculates a deviation between the unbalance factor calculated by the unbalance factor detection circuitry and a predetermined threshold, and calculates a reactive current subtraction amount or a reactive power subtraction amount for reducing the deviation, thus limiting output reactive current of the power converter. ### Claim 11 (depends on 1) The reactive power compensation device according to claim 1, wherein the power converter includes three arms connected to the AC power grid, each of the arms is formed such that one unit cell or a plurality of unit cells connected in cascade, and a reactor, are connected in series, and the unit cell includes a series unit composed of a plurality of the switching elements connected in series to each other, and a DC capacitor connected in parallel to the series unit. ### Claim 12 (depends on 11) The reactive power compensation device according to claim 11, wherein the three arms are delta-connected. ### Claim 13 (depends on 11) The reactive power compensation device according to claim 11, wherein the unit cell has a full-bridge configuration in which a plurality of the series units each composed of the switching elements are connected in parallel. ### Claim 14 (depends on 2) The reactive power compensation device according to claim 2, wherein in the case where the output reactive power of the power converter needs to be limited, the output limit circuitry limits output reactive current of the power converter. ### Claim 15 (depends on 14) The reactive power compensation device according to claim 14, wherein the AC voltage detection circuitry includes a positive-phase-sequence voltage detection circuitry for detecting positive-phase-sequence voltage of grid voltage of the AC power grid, and calculates a reactive current reference value on the basis of the positive-phase-sequence voltage detected by the positive-phase-sequence voltage detection circuitry and a voltage command value for the power converter, and the output limit circuitry subtracts a reactive current subtraction amount from the reactive current reference value, to calculate a reactive current command value, thus limiting the output reactive current of the power converter. ### Claim 16 (depends on 15) The reactive power compensation device according to claim 15, wherein the output limit circuitry subtracts the reactive current subtraction amount set in advance on the basis of an impedance of the AC power grid, from the reactive current reference value, to calculate the reactive current command value, thus limiting the output reactive current of the power converter. ### Claim 17 (depends on 2) The reactive power compensation device according to claim 2, wherein the AC voltage detection circuitry detects magnitudes of voltages for the respective phases of grid voltage of the AC power grid, and the output limit circuitry calculates a maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, and determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the maximum value among the magnitudes of the voltages for the respective phases. ### Claim 18 (depends on 3) The reactive power compensation device according to claim 3, wherein the AC voltage detection circuitry detects magnitudes of voltages for the respective phases of grid voltage of the AC power grid, and the output limit circuitry calculates a maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, and determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the maximum value among the magnitudes of the voltages for the respective phases. ### Claim 19 (depends on 4) The reactive power compensation device according to claim 4, wherein the AC voltage detection circuitry detects magnitudes of voltages for the respective phases of grid voltage of the AC power grid, and the output limit circuitry calculates a maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, and determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the maximum value among the magnitudes of the voltages for the respective phases. ### Claim 20 (depends on 5) The reactive power compensation device according to claim 5, wherein the AC voltage detection circuitry detects magnitudes of voltages for the respective phases of grid voltage of the AC power grid, and the output limit circuitry calculates a maximum value among the magnitudes of the voltages for the respective phases detected by the AC voltage detection circuitry, and determines whether or not the output reactive power of the power converter needs to be limited, on the basis of the maximum value among the magnitudes of the voltages for the respective phases.