Tracking simultaneous time-varying power harmonic distortions using filter banks

Abstract

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 timefrequency 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 timedependent 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.

Improved filter banks for time-varying power harmonic decomposition

“…Using the proposed filter bank structure and 69 th order filters, harmonic decomposition is done and reveals the timevarying nature of each harmonic. The harmonic decomposition has already been shown in references [1] and [2], and the decomposition using the proposed structure does not present visual differences. Table 1 shows a comparative result of the harmonic decomposition of the inrush current using different methods.…”

“…The first method is a Sliding-Window Recursive DFT used for harmonic decomposition in [3]. The second method is the filter bank structure presented in [1] [2]. In this second method are used filters with 69 th and 33 rd order.…”

“…In [11] and [12] the authors presented a methodology for separating the harmonic components up to 15 th , using selected digital filter and down-sampling to obtain the equivalent bandpass filters centered at each harmonic. After the signal is decomposed by the analysis filter bank, the signal is reconstructed using a synthesis filter bank, which is composed of band-pass filters and up-samplers, reconstructing each harmonic back into its original sampling rate.…”

“…After the signal is decomposed by the analysis filter bank, the signal is reconstructed using a synthesis filter bank, which is composed of band-pass filters and up-samplers, reconstructing each harmonic back into its original sampling rate. In this paper, is proposed a modification in the structure presented in [11] and [12]. This new structure does not require the use of notch filters to eliminate lateral components.…”

“…The paper is divided in the following sections: Section 2 presents a review of the structures presented in [11] and [12]; section 3 presents a proposed new structure; section 4 presents waveform decompositions. Finally, section 5 presents the conclusions.…”