Tracking simultaneous time-varying power harmonic distortions using filter banks

Abstract

Although it is well known that the Fourier analysis is only accurately applicable to steady-state waveforms, it is a widely used tool to study and monitor time-varying signals, such as are commonplace in electrical power systems. The disadvantages of the Fourier analysis, such as frequency spillover or problems due to sampling (data window) truncation can often be minimized by various windowing techniques, but they nevertheless exist. This paper demonstrates that it is possible to track and visualize amplitude and time-varying power systems harmonics, without frequency spillover caused by classical time-frequency techniques. This new tool allows for a clear visualization of time-varying harmonics, which can lead to better ways to track harmonic distortion and understand time-dependent power quality parameters. It has been applied to extract the harmonic contents of a rolling mill. It also has the potential to assist with control and protection applications.