Operations of the dominant harmonic active filter (DHAF) under realistic utility conditions

This paper presents laboratory test results of the dominant harmonic active filter (DHAF) prototype. The DHAF system achieves harmonic isolation at the dominant harmonics using square-wave active filter inverters. The key advantages of the DHAF system are the low rating and low bandwidth requirements of the active filter inverter. Such characteristics allow cost-effective and viable applications of the DHAF system to mitigate harmonic problems for high-power nonlinear loads (10-100 MW and above). Several practical situations, including source-sink resonance, ambient harmonic interferences, and unbalanced grid voltages are applied to the DHAF prototype to validate its performance. The operation principles of the DHAF system and the synchronous-reference-frame-based controller are discussed to explain how harmonic isolation at the dominant harmonics is accomplished. A design example of the DHAF system for a 20 MVA rectifier load at an industrial site is also given to illustrate its application.