A DIGITAL RECURSIVE MEASUREMENT SCHEME FOR ONLINE TRACKING OF POWER-SYSTEM HARMONICS

This paper presents an optimal measurement scheme for tracking the harmonics in power system voltage and current waveforms. The scheme does not require an integer number of samples in an integer number of cycles. It is not limited to stationary signals, but it can track harmonic with time-varying amplitudes. The paper starts with a review of the common frequency domain techniques for harmonics measurement. The common techniques are based on the discrete Fourier transform (DFT) and fast Fourier transform (FFT). The paper includes examples of pitfalls in the common techniques. The paper then introduces the concepts of the new scheme. The new scheme is based on Kalman filtering theory for the optimal estimation of the parameters of time-varying harmonics. The scheme is tested on simulated and actual recorded data sets.