# US 11,112,437 B2 · Inertia characteristic > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,112,437 B2 - Document ID: US11112437B2 - Status: Granted - Kind: B2 - Application number: 16/433,258 - Filed: 2019-06-06 - Published: 2019-09-19 - Granted: 2021-09-07 - Earliest claimed: 2016-12-07 - Assignees: Reactive Technologies Limited - Applicants: Reactive Technologies Limited - Inventors: Mika Ventola; Timo Peltola - Web page: https://patentgrep.com/patent/US11112437B2 ## CPC - G01R 19/2513: {Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging} - G01R 21/133: by using digital technique - G01R 23/00: Arrangements for measuring frequencies; Arrangements for analysing frequency spectra - H02J 3/00142: {Oscillations concerning frequency} - H02J 3/14: by switching loads on to, or off from, the networks, e.g. progressively balanced loading - H02J 3/40: Synchronisation of generators for connection to a network or to another generator - H02J 3/38: Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel - H02J 3/381: {Dispersed generators} - H02J 2101/24: Photovoltaics - H02J 2101/28: Wind energy - H02J 2105/12: supplying households or buildings - Y02B 70/3225: Demand response systems, e.g. load shedding, peak shaving - Y02E 10/56: Power conversion systems, e.g. maximum power point trackers - Y02E 10/76: Power conversion electric or electronic aspects - Y04S 20/222: Demand response systems, e.g. load shedding, peak shaving - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS - 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 Apparatus and methods for determining an inertia characteristic of a synchronous area of an electric power grid are described. First data is determined. The first data represents a signal comprising a first variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid, the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band. Second data is determined. The second data is representative of the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band. An inertia characteristic of a synchronous area of the electric power grid is determined based on the first data and the second data. ## Claims ### Claim 1 Apparatus for determining an inertia characteristic of a synchronous area of an electric power grid, electricity flowing in the grid in accordance with a grid frequency, wherein the apparatus is arranged to: determine first data representing a signal comprising a first variation, the first variation being a variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid, the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band; determine second data representative of the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band; and determine an inertia characteristic of a synchronous area of the electric power grid based on the first data and the second data, wherein one of the first frequency band and the second frequency band is set on the basis of the other of the first frequency band and the second frequency band. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein the apparatus comprises a measurement device arranged to: measure the signal comprising the first variation. ### Claim 3 (depends on 1) The apparatus according to claim 1, wherein the apparatus comprises a first filter element arranged to: apply, to the signal, the first filter defining the first frequency band. ### Claim 4 (depends on 3) The apparatus according to claim 3, wherein the first filter element comprises a plurality of filters, each of the plurality of filters defining a respective band to at least attenuate frequencies outside of the respective band, wherein the first filter element is representative of a combination of the plurality of filters. ### Claim 5 (depends on 1) The apparatus according to claim 1, wherein the apparatus comprises a second filter element arranged to: apply, to the second variation, a second filter defining the second frequency band to at least attenuate frequencies outside of the second frequency band. ### Claim 6 (depends on 5) The apparatus according to claim 5, wherein the second filter and/or the first filter comprises one or both of an analogue filter and a digital filter. ### Claim 7 A computer program comprising instructions which, when executed by a computer, causes the computer at least to perform: determining first data representing a signal comprising a first variation, the first variation being a variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid, the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band; determining second data representative of the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band; and determining an inertia characteristic of the electric power grid based on the first data and the second data, wherein one of the first frequency band and the second frequency band is set on the basis of the other of the first frequency band and the second frequency band. ### Claim 8 A method of determining an inertia characteristic of a synchronous area of an electric power grid, electricity flowing in the grid in accordance with a grid frequency, the method comprising: determining first data representing a signal comprising a first variation, the first variation being a variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid, the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band; determining second data representative of the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band; and determining an inertia characteristic of the electric power grid based on the first data and the second data, wherein one of the first frequency band and the second frequency band is set on the basis of the other of the first frequency band and the second frequency band. ### Claim 9 (depends on 8) The method according to claim 8, the method comprising: transforming one or both of the first variation and the second variation into a frequency domain. ### Claim 10 (depends on 8) The method according to claim 8, the method comprising: determining a plurality of first inertia characteristics for each of a respective different variation frequency. ### Claim 11 (depends on 10) The method according to claim 10, the method comprising: fitting a function to the plurality of first inertia characteristics, the function being parameterised at least by a local inertia parameter, thereby to derive the local inertia parameter, wherein the local inertia parameter is representative of an inertia of a local area of the synchronous area of the electric power grid. ### Claim 12 (depends on 11) The method according to claim 11, wherein the function is parameterised at least by one or more power flow parameters representative of the flow of power between the local area and one or more neighbouring areas of the synchronous area of the electric power grid. ### Claim 13 (depends on 10) The method according to claim 10, the method comprising: extrapolating, from the plurality of first inertia characteristics, a total inertia characteristic associated with the total synchronous area of the electric power grid. ### Claim 14 (depends on 8) The method according to claim 8, the method comprising: determining the first data for a first area of the electric power grid; and determining, based on the first data for the first area of the electric power grid, and the second data, a local inertia value relating to the first area using a function parameterised by at least a parameter relating to power flow between the first area and a second area of the electric power grid. ### Claim 15 (depends on 8) The method according to claim 8, the method comprising: controlling a provision of electric power to and/or a consumption of electric power from the grid, to generate the second variation. ### Claim 16 (depends on 15) The method according to claim 15, the method comprising: controlling the provision of electric power to and/or consumption of electric power from the grid such that the generated second variation is periodic. ### Claim 17 (depends on 15) The method according to claim 15, the method comprising: controlling the provision of electric power to and/or consumption of electric power from the grid such that the generated second variation comprises substantially only one variation frequency. ### Claim 18 (depends on 15) The method according to claim 15, the method comprising: controlling the provision of electric power to and/or consumption of electric power from the grid in a plurality of local areas of the synchronous area of the electric power grid. ### Claim 19 (depends on 18) The method according to claim 18, the method comprising: controlling the provision of electric power to and/or consumption of electric power from the grid in each of the plurality of local areas to be at a different time and/or at a different variation frequency to that of each other of the plurality of local areas. ### Claim 20 A method of determining a local inertia parameter representative of an inertia of a local area of a synchronous area of an electric power grid, electricity flowing in the grid in accordance with a grid frequency, the method comprising: determining first data representing a signal comprising a first variation, the first variation being a variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid, the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band; determining second data representative of the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band; determining, based on the first data and on the second data, a plurality of first inertia characteristics for each of a respective different variation frequency; and fitting a function to the plurality of first inertia characteristics, the function being parameterised at least by a local inertia parameter, thereby to derive the local inertia parameter, wherein one of the first frequency band and the second frequency band is set on the basis of the other of the first frequency band and the second frequency band. ### Claim 21 A method of determining a local inertia value representative of an inertia of a local area of a synchronous area of an electric power grid, electricity flowing in the grid in accordance with a grid frequency, the method comprising: determining first data representing a signal in a first area of the electric power grid, the signal comprising a first variation, the first variation being a variation in the grid frequency over a period of time, the signal resulting from a second variation, the second variation being a variation in provision of electric power to and/or consumption of electric power from the grid the signal having been filtered according to a first filter defining a first frequency band to at least attenuate frequencies outside of the first frequency band; determining second data relating to the second variation on a second frequency band, the second frequency band being substantially the same as the first frequency band; determining, based on the first data, and the second data, a local inertia value relating to the first area using a function parameterised by at least a parameter relating to power flow between the first area and a second area of the electric power grid, wherein one of the first frequency band and the second frequency band is set on the basis of the other of the first frequency band and the second frequency band.