Line harmonics reduction in high-power systems using square-wave inverters-based dominant harmonic active filter

This paper presents a dominant harmonic active filter (DHAF) scheme using small-rated square-wave inverters for supply line harmonic current reduction for high-power nonlinear loads in the range of 10 MW and above to meet IEEE 519 harmonic standard. The active filter inverters are connected in series with the fifth and seventh L-C tuned filters, respectively. A synchronous reference frame-based controller which achieves harmonic isolation for the dominant fifth and seventh harmonic load currents in the presence of supply voltage harmonic distortion is presented. Impact of mistuned passive filters on the operation and rating of the square-wave active filter inverters is examined. Simulation results validate the proposed harmonic isolation controller under mistuned fifth and seventh L-C tuned filter conditions and supply voltage harmonic distortion. The proposed scheme is general and applicable for high-power 6- or 12-pulse rectifier loads. The use of small-rated square-wave inverters (approximately 2% of load kilovoltampere rating) increases the cost effectiveness of the DHAF system for high-power applications.