A fuzzy-controlled versatile system for harmonics, unbalance and voltage sag compensation

In this paper, a proposed system comprising of a series active filter and passive branches tuned at some characteristic harmonics is introduced. The system is capable of compensating current and voltage harmonics, three-phase voltage unbalance, reactive power and voltage sags and swells in distribution networks supplying nonlinear loads. It combines the features of both the universal power quality conditioner and the dynamic voltage restorer. The series active filter is current-controlled to force the drawn current to be sinusoidal in phase with the mains voltage. A fuzzy logic-based controller is adopted to adjust the reference signal for the system. Thus, the source current and voltage waveforms are almost sinusoidal and in phase. Meanwhile, load voltage magnitude is fixed under a wide range of faulty and healthy operating conditions. Moreover, the compensation capacity of the proposed system is compared to the conventionally-controlled series active filter. The integrity and efficacy of the system are verified through simulation results.