Power System Frequency Estimation Algorithm for Electric Energy Metering of Nonlinear Loads

Abstract

In this paper, a discrete wavelet transform (DWT) based approach is proposed for power system frequency estimation. Unlike the existing frequency estimators mainly used for power system monitoring and control, the proposed approach is developed for fundamental frequency estimation in the field of energy metering of nonlinear loads. The characteristics of a nonlinear load is that the power signal is heavily distorted, composed of harmonics, inter-harmonics and corrupted by noise. The main idea is to predetermine a series of frequency points, and the mean value of two frequency points nearest to the power system frequency is accepted as the approximate solution. Firstly the input signal is modulated with a series of modulating signals, whose frequencies are those frequency points. Then the modulated signals are decomposed into individual frequency bands using DWT, and differences between the maximum and minimum wavelet coefficients in the lowest frequency band are calculated. Similarities among power system frequency and those frequency points are judged by the differences. Simulation results have proven high immunity to noise, harmonic and inter-harmonic interferences. The proposed method is applicable for real-time power system frequency estimation for electric energy measurement of nonlinear loads.

The Influence of Power Network Disturbances on Short Delayed Estimation of Fundamental Frequency Based on IpDFT Method with GMSD Windows

“…Spectrum interpolation can also be based on non-Fourier methods, e.g., Prony's method to model the signal using exponentially damped sinusoids [19] or the Aboutanios and Mulgrew's (HAM) method [20] and the cooperative weighted least squares (WLS) method representing HAM-WLS [20]. Spectrum estimation is also performed using time-frequency analyses e.g., discrete wavelet transform (DWT) [21] or Wigner-Ville transform [22].…”

Συμβολή Στην Ανάπτυξη Ολοκληρωμένης Μεθοδολογίας Εκτίμησης Εκπομπών Αρμονικών Από Ανεμογεννήτριες

“…Σύμφωνα με τους συγγραφείς, η μέθοδος είναι συμβατή με το πρότυπο IEC 61000-4-7 και παρέχει πολύ καλή ακρίβεια στο υπολογισμό των ανώτερων αρμονικών χωρίς να υστερεί σε υπολογιστικό χρόνο. Στην αντίθετη κατεύθυνση κινείται η αναφορά [198], όπου ο DWT εφαρμόζεται για τον υπολογισμό της θεμελιώδους συχνότητας του συστήματος με ικανοποιητική ακρίβεια αλλά με αρκετή επιβάρυνση σε χρόνο υπολογισμών.…”