An Iterative Technique for Real Time Tracking of Power System Harmonics

Abstract

Since the power quality became a serious concern for the utilities and consumers, harmonic monitoring has been of vital importance. A number of algorithms for estimating harmonics have been proposed in the past. Due to various power system conditions and number of computations involved, these algorithms are not suitable for real-time harmonic estimation. A short study of pitfalls in these techniques and their effect on harmonic estimates are presented. The thesis describes an iterative technique based on orthogonal filters and frequency tracking to estimate harmonic components in power systems. The technique use frequency interpolation to estimate fundamental frequency and harmonics when the nominal frequency of the signal is a non-integer value. Due to the number of computations involved during the generation of filter coefficients, off-line computations are suggested. The beneficial features of the proposed technique include fixed sampling rate and fixed data window. The performance of the proposed technique was studied by simulating different power system operating conditions and data from these simulations were used for evaluations. FFT based technique was also applied to estimate harmonic components for all the simulated signals. These estimates were compared with those obtained from the proposed technique. It has been shown that the proposed technique can converge to accurate fundamental frequency and therefore, provide accurate harmonic estimates even when the fundamental frequency is not equal to the nominal frequency.