A double tuned filter based on controllable reactor

Conventional passive filters which consist of parameter-fixed capacitors and reactors cannot retain good filtering performance in case of the system frequency drifts or components parameters change. In this paper, a controllable reactor in replace of the fixed one is adopted to compensate the parameters´ variation. First the theory of double tuned filter is introduced. Then the advantage brought in by the controllable reactor and the PI closed loop control strategy are analyzed in theory. The experiments of 5th-7th and 3rd-5th harmonics filters validate the good filtering performances