Abb Research Ltd.

Yales De-Novaes

Sami Pettersson

Antonio Coccia

Gerardo Escobar

Leonardo-Augusto Serpa

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 (&#x3bd;). The method includes measuring the three-phase voltage (&#x3bd;), calculating estimates of a fundamental frequency voltage component ({circumflex over (&#x3bd;)}) and a difference ({circumflex over (&#x3c6;)}) between positive and negative sequence components of the fundamental frequency voltage from an error ({tilde over (&#x3bd;)}) between the measured three-phase voltage (&#x3bd;) and at least one of the calculated estimates of the fundamental frequency voltage component ({circumflex over (&#x3bd;)}) and from an estimate of the angular frequency ({circumflex over (&#x3c9;)}) of the fundamental frequency voltage component, wherein the estimate of the angular frequency ({circumflex over (&#x3c9;)}) of the fundamental frequency voltage component is calculated from at lest one of the estimated differences ({circumflex over (&#x3c6;)}) and from the error ({tilde over (&#x3bd;)}) between the measured three-phase voltage and at least one of the calculated estimates of the fundamental frequency voltage component.

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Yales De-Novaes