A Method for Harmonic Measurement of Real Power Grid Signals with Frequency Drift using Instruments with Internally Generated Reference Frequency

Abstract

The authors have recently developed a number of instruments for measuring harmonic composition of power grid signals. These instruments have a simple, predominantly digital architecture and they are based on an assumption that the frequency of the measured signals equals its nominal value (50 Hz, 60 Hz or 400 Hz). This approach has enabled the measurement of a high number of harmonics within a single period. However, the internal oscillator in the instrument generates the nominal frequency and cannot adapt to frequency changes in the input signal. This paper presents a method for the improvement of the operation of the developed instruments in cases when the fundamental frequency drifts from its nominal value as is the case with real power grid signals. Based on this method, modified versions of the harmonic measurement instruments have been developed. A comparison of the measurement error with and without the application of the proposed method is presented in the paper.

Grid fundamental harmonic measurement in presence of Gaussian frequency deviation using 2-bit flash A/D converter

“…(2). The fourth central moment 4 µ which is a measure of distribution function kurtosis, should converge to value 3,5 in the case of Gaussian distribution. In this case, a value of the fourth central moment (4) is to some extent greater than 3,5, which indicates that the distribution function is slightly stretched along the vertical axis.…”

“…However, the accuracy is compromised when the frequency varies [2], which is the common occurrence in the European Interconnection [3]. In such a case, pseudo-harmonics are measured instead of real ones [4]. Conditions for detection of genuine mains voltage/current harmonics during frequency variations, as well as an algorithm for their calculation, are given in [4].…”

“…In such a case, pseudo-harmonics are measured instead of real ones [4]. Conditions for detection of genuine mains voltage/current harmonics during frequency variations, as well as an algorithm for their calculation, are given in [4].…”

Influence of Wilbraham-Gibbs Phenomenon on Digital Stochastic Measurement of EEG Signal Over an Interval

“…this quantization step is compared with previously found DSM errors. It can be noticed that DSM In the DSM approach, if there are no signal discontinuities, although measurement uncertainty can also be lowered by choosing an A/D converter with higher resolution, there are two other techniques of lowering measurement uncertainty [16][17][18][19][20]25]:…”

“…In [19] of this method to be applied for measurement of harmonics of any stationary signal. Improvement of this method is presented in [20], for the cases when fundamental frequency drifts from its nominal value as is the case with real power grid signals.…”