Recursive algorithm for real-time measurement of electrical variables in power systems

In this paper, a novel complex bandpass filter is presented which overcomes the pitfalls of the techniques in common use. This complex bandpass filter can correctly extract the phasor of the fundamental component and symmetrical components in voltage or current waveforms and then accurately estimate their instantaneous amplitude, phase angle, and frequency, even encountering various power disturbances. Further, a recursive algorithm is also developed for the complex bandpass filtering that updates current filtering output only using several previous sample values and filtering outputs. This attribute greatly reduces the computational complexity of complex bandpass filtering, which is the weakness of the continuous wavelet transform based on the well-known Morlet Wavelet. Thus, this recursive algorithm is highly desirable for real-time applications. The performance of the proposed technique is ascertained by using both simulated and practical power disturbance waveforms.

I. Introduction

Accurate and fast measurement of the instantaneous amplitude, phase angle, and frequency of the fundamental component and/or symmetrical components in three-phase power systems plays a key role in modern power instruments/meters, digital relays, control apparatus, and powerquality (PQ) studies. The performances of the techniques employed directly determine the functions of this equipment and affect their behaviors under various service conditions. Hence, the real-time accurate measurement of the phasor of the fundamental component and/or symmetrical components is essential and crucial to the safe and economic running of modern electric power systems.