# US 11,309,702 B2 · Systems and methods for islanding protection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,702 B2 - Document ID: US11309702B2 - Status: Granted - Kind: B2 - Application number: 16/287,571 - Filed: 2019-02-27 - Published: 2019-08-29 - Granted: 2022-04-19 - Earliest claimed: 2018-02-27 - Assignees: Hitachi Energy Switzerland AG - Applicants: Hitachi Energy Switzerland AG - Inventors: Khoi Vu; Salman Khalid Gill - Web page: https://patentgrep.com/patent/US11309702B2 ## CPC - H02H 7/26: Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured (locating faults in cables G01R31/08) - H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)} - H02H 3/38: responsive to both voltage and current; responsive to phase angle between voltage and current - H02H 3/40: responsive to ratio of voltage and current - H02J 3/0012: characterised by the contingency detection means in AC networks, e.g. using phasor measurement units [PMU], synchrophasors or contingency analysis - H02J 3/381: {Dispersed generators} - H02J 3/388: Arrangements for the handling of islanding, e.g. for disconnection or for avoiding the disconnection of power - H02J 2101/10: Dispersed power generation using fossil fuels, e.g. diesel generators - H02J 2103/30: Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks - Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation - Y04S 40/20: Information technology specific aspects, e.g. CAD, simulation, modelling, system security - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - 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 Illustrative embodiments of systems and methods for detecting and responding to islanding of distributed energy resources are disclosed. In at least one illustrative embodiment, a method may include measuring voltage and current at a connection point between a distributed energy resource and an electrical grid, determining a Thévenin impedance of the electrical grid based upon the voltage and current measurements, and determining whether the Thévenin impedance has exceeded a predetermined threshold. In some embodiments, the method may further include disconnecting the distributed energy resource from the electrical grid in response to determining that the Thévenin impedance has exceeded the predetermined threshold. ## Claims ### Claim 1 A method comprising: measuring voltage and current at a connection point between a distributed energy resource and an electrical grid; determining a Thévenin impedance of the electrical grid based upon the voltage and current measurements; setting a predetermined threshold, wherein setting the predetermined threshold comprises: determining a first range of possible values for the Thévenin impedance under a normal condition using a computer simulation; determining a second range of possible values for the Thévenin impedance under an islanding condition using a computer simulation; and determining whether an overlap exists between the first and second ranges of possible values for the Thévenin impedance; and determining whether the Thévenin impedance has exceeded the predetermined threshold. ### Claim 2 (depends on 1) The method of claim 1, further comprising disconnecting the distributed energy resource from the electrical grid in response to determining that the Thévenin impedance has exceeded the predetermined threshold. ### Claim 3 (depends on 2) The method of claim 2, further comprising: determining, in response to disconnecting the distributed energy resource from the electrical grid, a subsequent Thévenin impedance of the electrical grid; and re-connecting, in response to determining that the subsequent Thévenin impedance is below the predetermined threshold, the distributed energy resource to the electrical grid. ### Claim 4 (depends on 1) The method of claim 1, further comprising setting the predetermined threshold based at least on a location of the distributed energy resource. ### Claim 5 (depends on 1) The method of claim 1, further comprising: setting, in response to determining that the overlap exists, a first predetermined threshold and a second predetermined threshold; determining whether the Thévenin impedance has exceeded the first predetermined threshold; and disconnecting the distributed energy resource from the electrical grid in response to determining that the Thévenin impedance has exceeded the first predetermined threshold. ### Claim 6 (depends on 5) The method of claim 5, further comprising: determining, in response to disconnecting the distributed energy resource from the electrical grid, a subsequent Thévenin impedance of the electrical grid; determining whether the Thévenin impedance has exceeded the second predetermined threshold; and re-connecting, in response to determining that the subsequent Thévenin impedance is below the second predetermined threshold, the distributed energy resource to the electrical grid. ### Claim 7 (depends on 1) The method of claim 1, wherein the normal condition includes the distributed energy resource providing power to the electrical grid, and wherein the islanding condition includes the distributed energy resource continuing to provide power to a subsection of the electrical grid after the subsection of the electrical grid has been isolated from a remainder of the electrical grid. ### Claim 8 (depends on 1) The method of claim 1, wherein the distributed energy resource includes at least one of a solar panel, a hydro system, a wind turbine, a geothermal power system, a biomass power system, and a diesel generator. ### Claim 9 A system comprising: a distributed energy resource; and a connection device coupled to the distributed energy resource to control distribution of power from the distributed energy resource to an electrical grid, wherein the connection device is configured to: measure voltage and current at a connection point between the distributed energy resource and the electrical grid; determine a Thévenin impedance of the electrical grid based upon the voltage and current measurements; set a predetermined threshold, wherein to set the predetermined threshold comprises to: determine a first range of possible values for the Thévenin impedance under a normal condition using a computer simulation; determine a second range of possible values for the Thévenin impedance under an islanding condition using a computer simulation; and determine whether an overlap exists between the first and second ranges of possible values for the Thévenin impedance; and determine whether the Thévenin impedance has exceeded the predetermined threshold. ### Claim 10 (depends on 9) The system of claim 9, wherein the connection device is further configured to disconnect the distributed energy resource from the electrical grid in response to a determination that the Thévenin impedance has exceeded the predetermined threshold. ### Claim 11 (depends on 10) The system of claim 10, wherein the connection device is further configured to: determine, in response to a disconnection of the distributed energy resource from the electrical grid, a subsequent Thévenin impedance of the electrical grid; and re-connect, in response to a determination that the subsequent Thévenin impedance is below the predetermined threshold, the distributed energy resource to the electrical grid. ### Claim 12 (depends on 9) The system of claim 9, wherein the connection device is further configured to set the predetermined threshold based at least on a location of the distributed energy resource. ### Claim 13 (depends on 9) The system of claim 9, wherein the connection device is further configured to: set, in response to a determination that the overlap exists, a first predetermined threshold and a second predetermined threshold; determine whether the Thévenin impedance has exceeded the first predetermined threshold; and disconnect the distributed energy resource from the electrical grid in response to a determination that the Thévenin impedance has exceeded the first predetermined threshold. ### Claim 14 (depends on 13) The system of claim 13, wherein the connection device is further configured to: determine, in response to a disconnection of the distributed energy resource from the electrical grid, a subsequent Thévenin impedance of the electrical grid; determine whether the Thévenin impedance has exceeded the second predetermined threshold; and re-connect, in response to a determination that the subsequent Thévenin impedance is below the second predetermined threshold, the distributed energy resource to the electrical grid. ### Claim 15 (depends on 9) The system of claim 9, wherein the normal condition includes the distributed energy resource providing power to the electrical grid, and wherein the islanding condition includes the distributed energy resource continuing to provide power to a subsection of the electrical grid after the subsection of the electrical grid has been isolated from a remainder of the electrical grid. ### Claim 16 (depends on 9) The system of claim 9, wherein the distributed energy resource includes at least one of a solar panel, a hydro system, a wind turbine, a geothermal power system, a biomass power system, and a diesel generator.