Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Time-Domain Signal Analysis Using Adaptive Notch Filter

Abstract: Noise reduction and signal decomposition are among important and practical issues in time-domain signal analysis. This paper presents an adaptive notch filter (ANF) to achieve both these objectives. For noise reduction purpose, the proposed adaptive filter successfully extracts a single sinusoid of a possibly time-varying nature from a noise-corrupted signal. The paper proceeds with introducing a chain of filters which is capable of estimating the fundamental frequency of a signal composed of harmonically related sinusoids, and of decomposing it into its constituent components. The order of differential equations governing this algorithm is 2n+1, where n is the number of constituent sinusoids that should be extracted. Stability analysis of the proposed algorithm is carried out based on the application of the local averaging theory under the assumption of slow adaptation. When compared with the conventional Fourier analysis, the proposed method provides instantaneous values of the constituting components. Moreover, it is adaptive with respect to the fundamental frequency of the signal. Simulation results verify the validity of the presented algorithm and confirm its desirable transient and steady-state performances as well as its desirable noise characteristics

Power system harmonics research: a survey

Abstract: The increased use of power electronic controlled equipment, such as variable speed drives, automated production lines, personal computers and non-linear electronic devices in power systems has given rise to a type of voltage and current waveform distortion called as ‘harmonics’. Harmonic can be defined as the undesirable components of a distorted periodic waveform whose frequencies are the integer multiples (non-integer multiples in case of inter-harmonics, and the frequency less than fundamental frequency in case of sub-harmonics) of the fundamental frequency. Presence of these harmonics results in increased losses, equipment heating and loss-of-life, and interference with protection, control and communication circuits as well as customer loads. The research has been underway since very beginning for control of power system harmonics and to supply consumers with reliable and ‘clean’ fundamental-frequency sinusoidal electric power that does not represent a damaging threat to their equipment. This paper, therefore, reviews the progress made in power system harmonics research and development since its inception. Attempts are also made to highlight the current and future issues involved in the development of quality and reliable electric power technology for future applications. A list of 145 research publications on the subject is also appended for a quick reference. Copyright © 2007 John Wiley & Sons, Ltd.

Structures with Semiactive Variable Stiffness Single/Multiple Tuned Mass Dampers

Abstract: This paper proposes application of single and multiple semiactive variable stiffness tuned mass dampers (STMD/SMTMD) for response control of multistory structures under several types of excitation A new semiactive control algorithm is developed based on real-time frequency tracking of excitation signal by short time Fourier transform A parametric study is performed in the frequency domain to investigate the dynamic characteristics and effectiveness of STMDs Time history responses of single-degree-of-freedom and five-degree-of-freedom structures equipped with STMDs at the roof level, subjected to harmonic, stationary, and nonstationary excitations are presented STMD/SMTMD are most effective when they have low damping ratios and the excitation frequency can be tracked They are superior than their passive counterparts in reducing the response of the main structure both under force and base excitations In case the fundamental frequency changes due to damage or deterioration of the main structure then th

Comparing the fundamental frequencies of resolved and unresolved harmonics: Evidence for two pitch mechanisms?

Abstract: Four experiments measured sensitivity (d′) to differences in fundamental frequency (F0) between two simultaneously presented groups of frequency‐modulated harmonics. Each group was passed through a bandpass filter in either a LOW (125–625 Hz), MID (1375–1875 Hz), or HIGH (3900–5400 Hz) frequency region. In the first two experiments, a dynamic F0 difference (ΔF0) was created by introducing a 180° disparity between the frequency modulations imposed on the two groups. Experiment 1 measured sensitivity to such ΔF0’s between a MID group with a baseline F0 of 125 Hz and all components summed in sine phase, and a HIGH group, in four conditions. When the baseline F0 of the HIGH group was also 125 Hz, performance was good when its components were summed in sine phase and bad when they were in alternating phase. Conversely, when the HIGH F0 was 62.5 Hz, performance was better for alternating phase than for sine phase, consistent with alternating phase doubling the internal representation of HIGH group’s F0. Similar...