Fast voltage detection for a single-phase dynamic voltage restorer (DVR) using morphological low-pass filters

In this paper, we introduce a Mathematical Morphology(MM) theory based low-pass filter to preprocess the single-phase voltage sag signal, to filter out noises and any other interferences in the sampled signal. A comparison between the MM filter and traditional low-pass filters is carried out to analyze the applicability and accuracy of the MM filter. The selection of structural element is discussed as well according to the filtering result. In addition, we introduce a "Specific Harmonic Elimination" method to eliminate certain low frequency harmonic of the sampled voltage after dq transformation, which could greatly simplify the design of the low-pass filter. Then a elliptic filter is used for constant component abstraction. Software simulation result has verified the practicability of the algorithm.