# US 9,438,042 B2 · Direct current power delivery system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,042 B2 - Document ID: US9438042B2 - Status: Granted - Kind: B2 - Application number: 13/769,919 - Filed: 2013-02-19 - Published: 2014-08-21 - Granted: 2016-09-06 - Earliest claimed: 2013-02-19 - Assignees: General Electric Company - Applicants: General Electric Company - Inventors: Di Zhang; Luis Jose Garces; Jian Dai; Rixin Lai - Web page: https://patentgrep.com/patent/US9438042B2 ## CPC - H02J 13/1323: {using optical fibres} - H02J 3/36: Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links - H02J 3/381: {Dispersed generators} - H02J 13/12: Monitoring network conditions, e.g. electrical magnitudes or operational status - H02J 2101/20: Dispersed power generation using renewable energy sources - Y02E 40/70: Smart grids as climate change mitigation technology in the energy generation sector - Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation - Y02E 60/60: Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] - Y04S 10/123: the energy generation units being or involving renewable energy sources - Y04S 10/30: State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge - Y04S 40/124: using wired telecommunication networks or data transmission busses - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS ## Abstract A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component. ## Claims ### Claim 1 A power transmission system comprising: a first unit for carrying out the steps of: receiving high voltage direct current (HVDC) power from an HVDC power line; generating an alternating current (AC) component indicative of a status of the first unit; adding the AC component to the HVDC power line; a second unit for carrying out the steps of: generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit; generate a compensatory AC component to eliminate the added AC component in the HVDC power line; and determine the status of the first unit based on the generated compensatory AC component. ### Claim 2 (depends on 1) The power transmission system of claim 1, wherein the status of the first unit comprises one or more anomalies at the first unit. ### Claim 3 (depends on 1) The power transmission system of claim 1, wherein the status of the first unit comprises one or more load requirements at the first unit. ### Claim 4 (depends on 1) The power transmission system of claim 1, wherein the first unit comprises a plurality of modules coupled to one or more power loads, and wherein each of the plurality of modules generates an unique alternating current (AC) component based on at least the status of the respective module of the first unit. ### Claim 5 (depends on 4) The power transmission system of claim 4, wherein each of the modules in the first unit is configured to add the unique AC component to the HVDC power line in such a way that the added AC component is undetectable by at least one of other of the plurality of modules in the first unit. ### Claim 6 (depends on 1) The power transmission system of claim 1, wherein the first unit comprises an energy storage unit configured to provide reactive power for generating the AC component. ### Claim 7 (depends on 1) The power transmission system of claim 1, wherein the second unit is configured to identify at least one of a frequency, an amplitude, and a phase of the compensatory AC component to determine the status of the first unit. ### Claim 8 (depends on 1) The power transmission system of claim 1, wherein the added AC component comprises a plurality of encoded cycles indicating the status of the first unit. ### Claim 9 (depends on 1) The power transmission system of claim 1, wherein the second unit comprises a control unit for adjusting at least one of the DC voltage and a DC current in the HVDC power line based on the status of the first unit. ### Claim 10 (depends on 1) The power transmission system of claim 1, wherein the first unit is coupled to at least one power load comprising oil and gas equipment. ### Claim 11 A method comprising: generating an alternating current (AC) component by a first unit, wherein the AC component indicates a status of the first unit; adding, by the first unit, the AC component to a high voltage direct current (HVDC) power line coupled between the first unit and a second unit; generating a compensatory AC component, by the second unit, to eliminate the added AC component in the HVDC power line; and determining the status of the first unit, by the second unit, based on the compensatory AC component. ### Claim 12 (depends on 11) The method of claim 11, wherein adding the AC component to the HVDC power line comprises adding the AC component to the HVDC power line in such a way that the AC component is undetectable by at least one of other modules and regulators in the first unit. ### Claim 13 (depends on 11) The method of claim 11, wherein adding the AC component to the HVDC power line comprises adding the AC component to the HVDC power line in such a way that a direct current (DC) link current in the HVDC power line is maintained constant between the first unit and the second unit. ### Claim 14 (depends on 11) The method of claim 11, wherein determining the status of the first unit comprises identifying at least one of a frequency, an amplitude, and a phase of the compensatory AC voltage to determine the status of the first unit. ### Claim 15 (depends on 11) The method of claim 11, wherein determining the status of the first unit comprises decoding a plurality of encoded cycles comprised in the added AC component to determine the status of the first unit. ### Claim 16 (depends on 11) The method of claim 11, wherein determining the status of the first unit further comprises adjusting a DC voltage or a DC current in the HVDC power line at the second unit based on the status of the first unit. ### Claim 17 A power transmission system comprising: a first unit for carrying out the steps of: transmitting high voltage direct current (HVDC) power on an HVDC power line; generating an alternating current (AC) component indicative of a status of the first unit; adding the AC component to the HVDC power line; a second unit for carrying out the steps of: receiving the HVDC power from the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit; generating a compensatory AC component to eliminate the added AC component in the HVDC power line; and determining the status of the first unit based on the generated compensatory AC component. ### Claim 18 (depends on 17) The power transmission system of claim 17, wherein the first unit is coupled to a power generation unit comprising a wind turbine.