Investigation of harmonic filtering for the state-of-the-art variable speed drives

State-of-the-art low voltage (LV) medium and high power variable speed drives are voltage source converters. Frequently, frond-end stage is a diode rectifier. To reduce the amount of input current harmonics multi-pulse rectifiers are used. Due to the high cost of active front-end and the specific transformer requirements of multi-pulse rectification, alternative harmonic filtering solutions are sought. In this paper, the performance of several techniques, proposed for harmonic filtering, is analyzed in view of LV drive application. It is shown that regardless of the proposed solution, harmonic filtering presents additional design requirements to the drive system and compliance with harmonic standards challenges the harmonic filter design in terms of capacitor current capability.