Single-branch multi-tuned filter for power harmonic suppression

Single-tuned filter is a cost-effective device for harmonic mitigation, but the detuning derived from the variation of filter elements seriously decreases the filter´s performance and it only can resonate at one harmonic frequency. This paper propose a single-branch multi-tuned filter (SBMTF) which consists of a single LC series branch but can simultaneously resonate at multiple harmonics and also can accommodate the variation of element parameters. The key element is an active reactor with two coupled windings, one called main winding is in series with the filter capacitor to form a tuned filter, and the other called compensation winding is used to continuously adjust the inductance of the main winding at different harmonic frequencies by injecting selective harmonic magnetic flux compensation current. With an automatic tuning controller, the SBMTF not only can mitigate multi-harmonics, but also can eliminate filter´s detuning. A simulation model and an experimental prototype of the proposed single-branch multi-tuned filter have been implemented to investigate the static and dynamic characteristic of the filter. The results show that this SBMTF can well suppress multiple harmonics.