Experimental verification of dominant harmonic active filter for high-power applications

A synchronous-reference-frame (SRF)-based controller for the dominant harmonic active filter (DHAF) system has already been proposed by the authors. The SRF controller is designed to achieve harmonic isolation at the dominant harmonic frequencies (such as at the 5th and/or 7th) between the supply and load. This allows implementation of the DHAF system by square-wave inverters switching at the 5th or 7th harmonic frequency. Compared to conventional active filter systems which require high-switching-frequency pulsewidth modulation inverters, the square-wave-inverter-based DHAF system provides a viable and cost-effective solution to achieve harmonic isolation for high-power nonlinear loads (10 MW and above) or cluster of nonlinear loads, to meet the IEEE 519 recommended harmonic standard. In this paper, a new feedforward command of the SRF controller is proposed which provides better dynamic performance. The improved feedforward command of the SRF controller can suppress any system resonances at the dominant harmonic frequencies and meet IEEE 519 harmonic current limits. Experimental results are presented to validate the effectiveness of the SRF controller and the DHAF system.