Two digital filtering algorithms for fast estimation of symmetrical components in power system: a static estimation approach

This paper presents the application of two digital filters working together for fast estimation of the system symmetrical components. The three-phase unbalanced system is transformed into αβ-transformation. Using such a transformation, harmonics of order 3 and their multiples can be eliminated from the input signal. Having identified the two-phase voltage, the positive and negative sequence phase voltage can be calculated using a constant transformation matrix as well. The zero sequence is easily estimated by averaging the unbalanced three-phase voltage at any sample instant. The least error square algorithm is the parameter estimation algorithm used to identify the magnitude and phase angle of each sequence component from the available samples of the specified component