Abstract
A synchronous reference frame (SRF) based controller for dominant harmonic active filter (DHAF) system has been proposed by the authors in [1], [2]. The SRF controller is designed to achieve harmonic isolation at the dominant harmonic frequencies (such as the 5 th or the 7 th ) between supply and load. Such design allows implementation of the DHAF system by square-wave inverters switching at the 5 th and 7 th harmonic frequencies. Compared to the conventional active filter systems which require high switching frequency PWM inverters for implementation, the square-wave inverter based DHAF system is more viable and cost-effective for high power non-linear load (10 MW and above) or cluster of non-linear loads to meet IEEE 519 harmonic standard. In this paper, a new feedforward command of the SRF controller is proposed to provide better dynamic performance. If the resonance of source impedance and passive filter bank occurs near the dominant 5 th or 7 th harmonic frequency, the amplification effect at the harmonic frequencies will cause severe distortion in the supply current. The improved feedforward command of the SRF controller is able to suppress the resonance and meet the requirement of IEEE 519 harmonic standard. Experimental results are also presented in this paper to validate the effectiveness of the SRF controller and the square-wave inverter based DHAF system.