Fundamental frequency

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

Frequency-Adjustable Positive Sequence Detector for Power Conditioning Applications

Abstract: This paper proposes a novel and simple positive sequence detector (PSD), which is inherently self-adjustable to fundamental frequency deviations by means of a software-based PLL (phase locked loop). Since the proposed positive sequence detector is not based on Fortescue's classical decomposition and no special input filtering is needed, its dynamic response may be as fast as one fundamental cycle. The digital PLL ensures that the positive sequence components can be calculated even under distorted waveform conditions and fundamental frequency deviations. For the purpose of validating the proposed models, the positive sequence detector has been implemented in a PC-based power quality monitor and experimental results illustrate its good performance. The PSD algorithm has also been evaluated in the control loop of a series active filter and simulation results demonstrate its effectiveness in a closed-loop system. Moreover, considering single-phase applications, this paper also proposes a general single-phase PLL and a fundamental wave detector (FWD) immune to frequency variations and waveform distortions

Frequency domain identification of Hammerstein models

Abstract: This paper discusses Hammerstein model identification in frequency domain using the sampled input-output data. By exploring the fundamental frequency and harmonics generated by the unknown nonlinearity, we propose a frequency domain approach and show its convergence for both the linear and nonlinear subsystems in the presence of noise. No a priori knowledge of the structure of the nonlinearity is required and the linear part can be non-parametric.

Robust frequency-estimation method for distorted and imbalanced three-phase systems using discrete filters

Abstract: The continuous monitoring of voltage characteristics in electric power systems, such as in microgrids, is required for power quality assessment, grid control, and protection purposes. Due to the presence of disturbances in the grid voltage, such as harmonics, imbalances, noise, and offsets introduced by the instrumentation, among others, the frequency-estimation process has to be robust against all these disturbances to obtain an accurate estimation of the frequency value. This paper presents a fast and accurate method to estimate the fundamental frequency of an electric power system. The estimation method works properly in balanced and imbalanced three-phase systems, and even in single-phase systems. The proposed solution is based on an algebraic method, which is able to calculate the frequency of a pure sinusoidal signal using three samples. A filtering stage is used to increase the robustness of the algorithm against disturbances in a wide frequency range. Simulation and experimental results show the good performance of the method for single- and three-phase systems with a high level of harmonic distortion, even in the presence of amplitude, phase, and frequency changes.

Noise reduction using a soft-decision sine-wave vector quantizer

Abstract: Noise reduction is performed in the context of a high-quality harmonic zero-phase sine-wave analysis/synthesis system which is characterized by sine-wave amplitudes, a voicing probability, and a fundamental frequency. Least-squared error estimation of a harmonic sine-wave representation leads to a soft decision template estimate consisting of sine-wave amplitudes and a voicing probability. The least-squares solution is modified to use template-matching with nearest neighbors. The reconstruction is improved by using the modified least-squares solution only in spectral regions with low signal-to-noise ratio. The results, although preliminary, provide evidence that harmonic zero-phase sine-wave analysis/synthesis, combined with effective estimation of sine-wave amplitudes and probability of voicing, offers a promising approach to noise reduction. >

Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species.

Abstract: Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.