# US 12,015,353 B1 · Attenuating harmonic current in power transmission lines > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,015,353 B1 - Document ID: US12015353B1 - Status: Granted - Kind: B1 - Application number: 17/571,151 - Filed: 2022-01-07 - Granted: 2024-06-18 - Earliest claimed: 2021-07-12 - Assignees: Smart Wires Inc. - Applicants: Smart Wires Inc. - Inventors: Govind Chavan - Web page: https://patentgrep.com/patent/US12015353B1 ## CPC - H02M 7/219: in a bridge configuration - H02M 1/12: Arrangements for reducing harmonics from AC input or output - H02M 7/7575: {for high voltage direct transmission link} - 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) ## Abstract A series connectable power flow module is for connection to a power transmission line. The module has a full bridge inverter and a controller. The full bridge inverter has inputs for controlling charging and discharging a DC link capacitor. The controller is coupled to the inputs of the full bridge inverter. The controller is configured to separate a harmonic current from a line current flowing in the power transmission line. The controller operates the full bridge inverter in accordance with the separated harmonic current, to attenuate the harmonic current flowing in the power transmission line through injection of a DC link capacitor voltage. ## Claims ### Claim 1 A series connectable power flow control module for connection to a power transmission line, comprising: a full bridge inverter having inputs for controlling charging and discharging a DC (direct current) link capacitor; and a controller coupled to the inputs of the full bridge inverter and configured to: separate, from a line current, a harmonic current flowing in the power transmission line, to produce a separated harmonic current, phase lock to the separated harmonic current to provide a phase locked harmonic current, produce a varying DC value of the separated harmonic current based on the separated harmonic current and the phase locked harmonic current, and operate the full bridge inverter based on the varying DC value, to inject an impedance into the power transmission line, wherein the injected impedance attenuates the harmonic current flowing in the power transmission line. ### Claim 2 (depends on 1) The power flow control module of claim 1, wherein the controller comprises a high-pass filter that separates the harmonic current from the line current. ### Claim 3 (depends on 1) The power flow control module of claim 1, wherein the controller comprises a phase locked loop to phase lock to the separated harmonic current to provide the phase locked harmonic current. ### Claim 4 (depends on 1) The power flow control module of claim 1, wherein the controller comprises a direct-quadrature (dq) converter coupled to a phase locked loop, to produce the varying DC value of the separated harmonic current based on the separated harmonic current and the phase locked harmonic current. ### Claim 5 (depends on 1) The power flow control module of claim 1, wherein the controller comprises a proportional integrator coupled to an output of a direct-quadrature (dq) converter, to produce a quadrature value based on the varying DC value. ### Claim 6 (depends on 1) The power flow control module of claim 1, wherein the controller comprises an inverse direct-quadrature (dq) converter coupled to an output of a first proportional integrator, to produce a command value based on a quadrature value produced by the first proportional integrator. ### Claim 7 (depends on 1) The power flow control module of claim 1, wherein the controller comprises an inverse direct-quadrature (dq) converter coupled to receive a reference DC value through a second proportional integrator arranged to produce a direct value based on a DC link capacitor voltage. ### Claim 8 (depends on 1) The power flow control module of claim 1, wherein the controller comprises a comparator having an output of an inverse direct-quadrature (dq) converter as a first input and arranged to have a sawtooth waveform as a second input. ### Claim 9 (depends on 8) The power flow control module of claim 8, wherein outputs of the comparator are coupled to the inputs of the full bridge inverter. ### Claim 10 (depends on 8) The power flow control module of claim 8, wherein a frequency of the sawtooth waveform is in a range of ten to fifty times a frequency of the separated harmonic current. ### Claim 11 A method for attenuating a harmonic current in a power transmission line, the method comprising: separating, through a high-pass filter, the harmonic current from a line current of the power transmission line to produce a separated harmonic current; determining a selected frequency of the separated harmonic current; producing a varying DC (direct current) representation of the separated harmonic current based on the separated harmonic current and the selected frequency; determining an injection voltage for charging and discharging a DC link capacitor, based on the varying DC representation of the separated harmonic current; comparing the injection voltage with a sawtooth waveform; and driving inputs to a full bridge inverter coupled to the DC link capacitor based on the comparison, to inject an impedance into the power transmission line in accordance with the separated harmonic current, wherein the injected impedance attenuates the harmonic current in the power transmission line. ### Claim 12 (depends on 11) The method of claim 11, wherein producing the varying DC representation of the separated harmonic current comprises direct-quadrature (dq) transforming. ### Claim 13 (depends on 11) The method of claim 11, wherein: determining the selected frequency of the separated harmonic current comprises determining the selected frequency of the separated harmonic current using a phase locked loop; and the method further comprises determining a frequency of the sawtooth waveform as a multiple of the selected frequency. ### Claim 14 (depends on 13) The method of claim 13, wherein the multiple is in a range of ten to fifty. ### Claim 15 A power flow control module, for series connection to a power transmission line, comprising: a full bridge inverter having a DC (direct current) link capacitor; and a controller coupled to the full bridge inverter the controller is configured to: separate a harmonic current from a line current of the power transmission line to produce a separated harmonic current; filter the separated harmonic current to determine a selected harmonic current; phase lock to the selected harmonic current to provide a phase locked selected harmonic current; produce a quadrature value based on the phase locked selected harmonic current; produce a direct value based on a DC link capacitor voltage; and operate the full bridge inverter in accordance with the quadrature value and the direct value, to inject an impedance into the power transmission line, wherein the injected impedance attenuates the harmonic current in the power transmission line. ### Claim 16 (depends on 15) The power flow control module of claim 15, further comprising: a current sensor, for the controller to detect and separate the harmonic current from the line current. ### Claim 17 (depends on 15) The power flow control module of claim 15, wherein the controller has a high-pass filter having at least one notch in a bandpass region, to filter the separated harmonic current and determine the selected harmonic current. ### Claim 18 (depends on 15) The power flow control module of claim 15, wherein the controller has a phase locked loop and a direct-quadrature (dq) converter, to phase lock and produce the quadrature value. ### Claim 19 (depends on 15) The power flow control module of claim 15, wherein the controller ha s a first comparator and a first proportional integrator to produce the quadrature value, a second comparator and a second proportional integrator to produce the direct value, and an inverse dq converter to produce a command variable for timing pulses to operate the full bridge inverter in accordance with the quadrature value and the direct value. ### Claim 20 (depends on 15) The power flow control module of claim 15, wherein the controller ha s a comparator and is to generate gate controls through the comparator, based on a sawtooth waveform and a command variable, to operate the full bridge inverter. ### Claim 21 A power flow control system comprising: a plurality of power flow control modules connected in series to a power transmission line, wherein each power flow control module is configured to isolate and attenuate a predetermined high frequency harmonic component of a line current flowing in the power transmission line through operating a full bridge inverter to inject an impedance into the power transmission line in accordance with a varying DC value produced based on a separated harmonic current and a phase locked harmonic current; wherein a harmonic current is separated from the line current flowing in the power transmission line to produce the separated harmonic current, the phase locked harmonic current is phase locked to the separated harmonic current, and the injected impedance attenuates the predetermined high frequency harmonic component of the line current flowing in the power transmission line.