# US 8,751,177 B2 · Method and arrangement for estimating angular frequency > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,751,177 B2 - Document ID: US8751177B2 - Status: Granted - Kind: B2 - Application number: 13/075,827 - Filed: 2011-03-30 - Published: 2011-10-06 - Granted: 2014-06-10 - Earliest claimed: 2010-03-31 - Assignees: ABB Research Ltd. - Applicants: Gerardo Escobar; Antonio Coccia; Leonardo-Augusto Serpa; Sami Pettersson; Yales De-Novaes - Inventors: Gerardo Escobar; Antonio Coccia; Leonardo-Augusto Serpa; Sami Pettersson; Yales De-Novaes - Web page: https://patentgrep.com/patent/US8751177B2 ## CPC - G01R 23/02: Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage - G01R 19/2513: {Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract An exemplary method and arrangement for estimating the frequency and the positive sequence of a fundamental component of a measured three-phase voltage are disclosed (ναβ). The method includes measuring the three-phase voltage (ναβ), calculating estimates of a fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and a difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of the fundamental frequency voltage from an error ({tilde over (ν)}αβ) between the measured three-phase voltage (ναβ) and at least one of the calculated estimates of the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and from an estimate of the angular frequency ({circumflex over (ω)}0) of the fundamental frequency voltage component, wherein the estimate of the angular frequency ({circumflex over (ω)}0) of the fundamental frequency voltage component is calculated from at lest one of the estimated differences ({circumflex over (φ)}αβ,1) and from the error ({tilde over (ν)}αβ) between the measured three-phase voltage and at least one of the calculated estimates of the fundamental frequency voltage component. ## Claims ### Claim 1 A method for estimating the frequency of a measured three-phase voltage (ναβ) comprising: measuring the three-phase voltage; and calculating estimates of a fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and a difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of a fundamental frequency voltage, from an error ({tilde over (ν)}αβ) between the measured three-phase voltage (ναβ) and at least one of the calculated estimates of the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and from an estimate of an angular frequency ({circumflex over (ω)}0) of the fundamental frequency voltage component; generating at least a clean electrical signal corresponding to the measured three-phase voltage based on the estimates of the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) wherein the estimate of the angular frequency ({circumflex over (ω)}0) of the fundamental frequency voltage component is calculated from at least one of the estimated differences ({circumflex over (φ)}αβ,1) and from the error ({tilde over (ν)}αβ) between the measured three-phase voltage and at least one of the calculated estimates of the fundamental frequency voltage component. ### Claim 2 (depends on 1) The method according to claim 1, wherein the estimates are calculated by using an estimator, in which the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and the difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of the fundamental frequency voltage are the state variables, and the estimate of the angular frequency is reconstructed using an adaptive law. ### Claim 3 (depends on 1) The method according to claim 1, comprising: calculating a positive sequence component (ναβ,1p) of the fundamental frequency voltage component from the estimated fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and the difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of the fundamental frequency voltage, wherein the positive sequence component of the fundamental frequency voltage component has a frequency of the measured three-phase voltage (ναβ). ### Claim 4 (depends on 1) The method according to claim 1, comprising: calculating a negative sequence component (ναβ,1n) of the fundamental frequency voltage component from the estimated fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and the difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of the fundamental frequency voltage, wherein the positive sequence component of the fundamental frequency voltage component has a frequency of the measured three-phase voltage (ναβ). ### Claim 5 (depends on 1) The method according to claim 1, comprising: estimating selected harmonic components ({circumflex over (ν)}αβ,h) of the measured three-phase voltage by using the error ({tilde over (ν)}αβ) between the measured three-phase voltage (ναβ) and the calculated estimate of the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and the estimate of the angular frequency ({circumflex over (ω)}0) of the fundamental voltage component; and subtracting the estimated selected harmonic components ({circumflex over (ν)}αβ,h) from the measured three-phase voltage to eliminate the effects of harmonic distortion from the measured signal. ### Claim 6 An arrangement for estimating the frequency of a measured three-phase voltage (ναβ), comprising: means for measuring the three-phase voltage (ναβ); and means for calculating estimates of a fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and a difference ({circumflex over (φ)}αβ,1) between positive and negative sequence components of a fundamental frequency voltage from an error ({tilde over (ν)}αβ) between the measured three-phase voltage (ναβ) and at least one of the calculated estimates of the fundamental frequency voltage component ({circumflex over (ν)}αβ,1) and from an estimate of an angular frequency ({circumflex over (ω)}0) of the fundamental voltage component, wherein the estimate of the angular frequency ({circumflex over (ω)}0) of the fundamental frequency voltage component is calculated from at least one of the estimated differences ({circumflex over (φ)}αβ,1) and from the error (ναβ) between the measured three-phase voltage and at least one of the calculated estimates of the fundamental frequency voltage component.