A Hybrid Active Filter for a Three-Phase 12-Pulse Diode Rectifier Used as the Front End of a Medium-Voltage Motor Drive

TLDR

The study proposes a hybrid active filter to reduce line‑side harmonic currents in the front end of a medium‑voltage high‑power motor drive using a three‑phase 12‑pulse diode rectifier. The filter combines a series LC tuned to the 11th harmonic with a small‑rated three‑level NPC PWM active stage, yielding a low‑cost, compact, lightweight solution tested on a 400 V/15 kW experimental system connected to a multi‑winding transformer. Tests demonstrate that the hybrid filter effectively suppresses harmonics across no‑load to full‑load operating conditions.

Abstract

This paper describes a hybrid active filter intended for mitigating the line-side harmonic currents of a three-phase 12-pulse diode rectifier used as the front end of a medium-voltage high-power motor drive. This hybrid filter is characterized by series connection of a simple LC filter and a small-rated active filter. This circuit configuration brings low cost, small size, and light weight to the hybrid filter. A three-phase experimental system rated at 400 V and 15 kW is designed, constructed, and tested, which is a downscaled model of the medium-voltage motor drive system. In this experiment, the LC filter is tuned to the 11th-harmonic frequency, and the active filter is based on a three-level neutral-point-clamped pulsewidth modulation converter (NPC PWM) with a dc capacitor voltage as low as 28 V. This hybrid filter is connected on either first or fourth winding of a line-frequency transformer with a first Δ-winding voltage of 400 V in the primary, and a second Δ-winding voltage of 220 V, a third Y-winding voltage of 220 V, and a fourth Δ-winding voltage of 400 V in the secondary. Experimental results show that the hybrid filter performs satisfactory filtering in a range from no-load to full-load conditions.