Advanced Active Output Filter for Low Acoustic Noise Adjustable Speed Drive (ASD) System

Abstract

In recent years, the acoustic noise emitted by electric motors has become an important topic. Many manufactures of adjustable speed drive (ASD) make effort to reduce the acoustic noise from electric motors. And low acoustic noise motors can be widely applied in the next generation transport system such as electric shipboard, more electric aircraft and electric vehicle. Traditionally, LC passive filters can be employed to decrease acoustic noise by mitigating the pulse-width modulation (PWM) generated voltage/current harmonics in the audible noise range. However, the bulky passive filters contribute to additional volume and cannot effectively eliminate harmonics at low switching frequency.

In this thesis, an active output filter (AOF) is proposed to replace passive filters in ASD. The proposed AOF is implemented by the harmonic injection strategy, which can compensate voltage/current harmonics at the arbitrary frequency. Therefore, the acoustic noise, which partly generates from PWM inverter-fed ASD, is decreased dramatically. In addition, AOF offers a substantial volume reduction and high power efficiency by using wide-band gap devices. In this thesis, two different motor drive structures including single-phase ASD, three-phase ASD are investigated to verify the advantages of the proposed AOF.