Fuzzy Logic Controller Based Hybrid Active Filter for Harmonic Mitigation

This project presents hybrid active filter to uppers harmonic resonances in industrial power systems. The proposed hybrid filter is composed of a seventh harmonic-tuned passive filter and an active filter in series connection at the secondary side of the distribution transformer. With the active filter part operating as variable harmonic conductance, the filtering performances of the passive filter can be significantly improved. Accordingly, the harmonic resonances can be avoided, and the harmonic distortion can be maintained inside an acceptable level in case of load changes and variations of line impedance of the power system. Simulation results verify the effectiveness of the proposed fuzzy logic controller based hybrid active filter. Extended discussions are s summarized as follows. ·        Large line inductance and large nonlinear load may result in severe voltage distortion. The conductance is increased to maintain distortion to an acceptable level. ·         Line resistance may help reduce voltage distortion. The conductance is decreased accordingly using fuzzy controller. ·        For low line impedance, THD∗ should be reduced to enhance filtering performances. In this situation, measuring voltage distortion becomes a challenging issue. ·         High-frequency resonances resulting from capacitive filters is possible t o be suppressed by the proposed method. ·        In case of unbalanced voltage, a band-rejected filter is needed to filter out second-order harmonics if the SRF is realized to extract voltage harmonics.

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