A Fast and Robust Real-Time Detection Algorithm of Decaying DC Transient and Harmonic Components in Three-Phase Systems

Active power filters are conventionally utilized to compensate steady-state harmonic currents and reactive power in the utility, yet their capabilities are usually limited if the elimination of undesirable effects associated with decaying dc components during transients is the target, especially under the weak grid condition. In this letter, active cancellation of the typical first-order decaying dc-mode transients is explored. To this end, a real-time detection algorithm of decaying dc component is first developed for a generic single-phase distorted ac signal. Furthermore, fast and robust elimination of both decaying dc transient and harmonics can be performed simultaneously in three-phase grids, by adoption of moving average filters in d-q frame and subsequent calculations. Hardware-in-the-loop experiment results verified the effectiveness of the proposed technique.