Method and arrangement for estimating angular frequency

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.