# US 11,451,214 B2 · Control device and active filter apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,214 B2 - Document ID: US11451214B2 - Status: Granted - Kind: B2 - Application number: 17/291,678 - Filed: 2018-12-18 - Published: 2022-01-06 - Granted: 2022-09-20 - Earliest claimed: 2018-12-18 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Masatoshi Takeda; Tomohiko Tatsumi; Shinichi Ogusa; Akihiro Matsuda - Web page: https://patentgrep.com/patent/US11451214B2 ## CPC - H02J 3/1828: with stepwise control, e.g. switched capacitor banks - H03H 11/04: Frequency selective two-port networks - H02J 3/01: Arrangements for reducing harmonics or ripples - H02M 1/12: Arrangements for reducing harmonics from AC input or output - Y02E 40/20: Active power filtering [APF] - Y02E 40/30: Reactive power compensation - Y02E 40/40: Arrangements for reducing harmonics - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A control device for an active filter connected in parallel with a load at an installation point with respect to an AC power supply provided in a power system includes a harmonic voltage detector to detect an m-order harmonic voltage (m is an integer not less than two) included in a voltage of the installation point, a phase corrector to correct a phase of the detected m-order harmonic voltage in accordance with whether an m-order harmonic impedance when an AC power supply side is seen from the installation point is capacitive or inductive, a command value generator to generate a first compensation command value for compensating for the m-order harmonic voltage included in the voltage of the installation point based on the m-order harmonic voltage after the correction, and an output controller to control an output of the active filter based on a first compensation command value. ## Claims ### Claim 1 A control device for an active filter connected in parallel with a load at an installation point with respect to an AC power supply provided in a power system, the control device comprising: a harmonic voltage detector to detect an m-order harmonic voltage (m is an integer not less than two) included in a voltage of the installation point; a phase corrector to correct a phase of the detected m-order harmonic voltage in accordance with whether an m-order harmonic impedance when an AC power supply side is seen from the installation point is capacitive or inductive; a command value generator to generate a first compensation command value for compensating for the m-order harmonic voltage included in the voltage of the installation point based on the m-order harmonic voltage after the correction; and an output controller to control an output of the active filter based on the first compensation command value, wherein the phase corrector does not correct the phase of the detected m-order harmonic voltage when the m-order harmonic impedance is inductive. ### Claim 2 (depends on 1) The control device according to claim 1, wherein the phase corrector advances the phase of the detected m-order harmonic voltage by a first angle when the m-order harmonic impedance is capacitive. ### Claim 3 (depends on 2) The control device according to claim 2, wherein the first angle is 60° to 90°. ### Claim 4 (depends on 1) The control device according to claim 1, further comprising a monitoring unit to monitor the first compensation command value, wherein the monitoring unit determines whether the m-order harmonic impedance has changed from an inductive state to a capacitive state based on the first compensation command value. ### Claim 5 (depends on 4) The control device according to claim 4, wherein the monitoring unit determines that the m-order harmonic impedance is capacitive when an effective value of the first compensation command value is greater than a first threshold. ### Claim 6 (depends on 4) The control device according to claim 4, wherein the phase corrector advances the phase of the detected m-order harmonic voltage by a reference angle when the m-order harmonic impedance is determined to be capacitive. ### Claim 7 (depends on 6) The control device according to claim 6, wherein when the m-order harmonic impedance is determined to be capacitive after advancing the phase of the detected m-order harmonic voltage by the reference angle, the phase corrector advances the phase of the m-order harmonic voltage advanced by the reference angle additionally by the reference angle. ### Claim 8 (depends on 1) The control device according to claim 1, further comprising: a harmonic current detector to detect an m-order harmonic current included in a current output to the installation point by the active filter; and an impedance computing unit to compute the m-order harmonic impedance based on the detected m-order harmonic voltage and the detected m-order harmonic current, wherein the impedance computing unit determines whether the m-order harmonic impedance is capacitive or inductive based on a polarity of a phase of the computed m-order harmonic impedance. ### Claim 9 (depends on 8) The control device according to claim 8, wherein the phase corrector advances the phase of the detected m-order harmonic voltage by an angle corresponding to magnitude of the phase of the m-order harmonic impedance when the m-order harmonic impedance is determined to be capacitive. ### Claim 10 (depends on 1) The control device according to claim 1, wherein the harmonic voltage detector further detects an n-order harmonic voltage (n is an integer different from m and not less than two) included in the voltage, the phase corrector corrects a phase of the detected n-order harmonic voltage in accordance with whether an n-order harmonic impedance when the AC power supply side is seen from the installation point is capacitive or inductive, the command value generator generates a second compensation command value for compensating for the n-order harmonic voltage included in the voltage of the installation point based on the n-order harmonic voltage after the correction, and the output controller controls the output of the active filter based on the first compensation command value and the second compensation command value. ### Claim 11 (depends on 5) The control device according to claim 5, wherein the phase corrector advances the phase of the detected m-order harmonic voltage by a reference angle when the m-order harmonic impedance is determined to be capacitive. ### Claim 12 (depends on 2) The control device according to claim 2, wherein the harmonic voltage detector further detects an n-order harmonic voltage (n is an integer different from m and not less than two) included in the voltage, the phase corrector corrects a phase of the detected n-order harmonic voltage in accordance with whether an n-order harmonic impedance when the AC power supply side is seen from the installation point is capacitive or inductive, the command value generator generates a second compensation command value for compensating for the n-order harmonic voltage included in the voltage of the installation point based on the n-order harmonic voltage after the correction, and the output controller controls the output of the active filter based on the first compensation command value and the second compensation command value. ### Claim 13 (depends on 3) The control device according to claim 3, wherein the harmonic voltage detector further detects an n-order harmonic voltage (n is an integer different from m and not less than two) included in the voltage, the phase corrector corrects a phase of the detected n-order harmonic voltage in accordance with whether an n-order harmonic impedance when the AC power supply side is seen from the installation point is capacitive or inductive, the command value generator generates a second compensation command value for compensating for the n-order harmonic voltage included in the voltage of the installation point based on the n-order harmonic voltage after the correction, and the output controller controls the output of the active filter based on the first compensation command value and the second compensation command value. ### Claim 14 (depends on 4) The control device according to claim 4, wherein the harmonic voltage detector further detects an n-order harmonic voltage (n is an integer different from m and not less than two) included in the voltage, the phase corrector corrects a phase of the detected n-order harmonic voltage in accordance with whether an n-order harmonic impedance when the AC power supply side is seen from the installation point is capacitive or inductive, the command value generator generates a second compensation command value for compensating for the n-order harmonic voltage included in the voltage of the installation point based on the n-order harmonic voltage after the correction, and the output controller controls the output of the active filter based on the first compensation command value and the second compensation command value. ### Claim 15 (depends on 5) The control device according to claim 5, wherein the harmonic voltage detector further detects an n-order harmonic voltage (n is an integer different from m and not less than two) included in the voltage, the phase corrector corrects a phase of the detected n-order harmonic voltage in accordance with whether an n-order harmonic impedance when the AC power supply side is seen from the installation point is capacitive or inductive, the command value generator generates a second compensation command value for compensating for the n-order harmonic voltage included in the voltage of the installation point based on the n-order harmonic voltage after the correction, and the output controller controls the output of the active filter based on the first compensation command value and the second compensation command value. ### Claim 16 An active filter apparatus comprising: an active filter connected in parallel with a load at an installation point with respect to an AC power supply provided in a power system; and a control device for the active filter, wherein the control device includes a harmonic voltage detector to detect an m-order harmonic voltage (m is an integer not less than two) included in a voltage of the installation point, a phase corrector to correct a phase of the detected m-order harmonic voltage in accordance with whether an m-order harmonic impedance when an AC power supply side is seen from the installation point is capacitive or inductive, a command value generator to generate a first compensation command value for compensating for the m-order harmonic voltage included in the voltage of the installation point based on the m-order harmonic voltage after the correction, and an output controller to control an output of the active filter based on the first compensation command value, wherein the phase corrector does not correct the phase of the detected m-order harmonic voltage when the m-order harmonic impedance is inductive.