Most of the existing harmonic mitigation schemes for three-phase, four-wire systems focus on redirecting zero-sequence current harmonics from the neutral conductor back to the phase conductors. However, the portion of the neutral conductor that lies between the loads and the active filter is still burdened by the excessive current harmonics. In this article, a series active filter system for three-phase, four-wire distribution systems will be proposed. An active filter inverter will be placed in series connection with the neutral conductor to suppress the excessive current harmonics, thus preventing the overloading problem of the neutral conductor and the distribution transformer. Detailed analysis of the proposed system will be presented, and laboratory test results will be provided to validate the filtering performance of the proposed system.
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