Efficient detection for multifrequency dynamic phasor analysis

Analysis of harmonic and interharmonic phasors is a promising smart grid measurement and diagnostic tool. This creates the need to deal with multiple phasor components having different amplitudes, including interharmonics with unknown frequency locations. The Compressive Sensing Taylor-Fourier Multifrequency (CSTFM) algorithm provides very accurate results under demanding test conditions, but is computationally demanding. In this paper we present a novel frequency search criterion with significantly improved effectiveness, resulting in a very efficient revised CSTFM algorithm

Design of Compressive Sensing Adaptive Taylor-Fourier Comb Filters for Harmonic Synchrophasor Estimation

In modern power systems, phasor measurements are expected to deal with challenging conditions, e.g., fast dynamics and high distortion levels. Taylor-Fourier Multifrequency models represent a promising solution, but their performance is strongly related to the accurate extraction of the signal spectral support. In this context, this paper proposes an enhanced method for support recovery that exploits the inherent block-sparsity properties of electrical signals. The proposed method is fully characterized in diverse and distorted test conditions, inspired by reference standards and real-world scenarios. The comparison against another Compressive Sensing based approach confirms the significant improvement in terms of both recovered support exactness and synchrophasor measurement accuracy

Monitoring Biosensor Activity in Living Cells with Fluorescence Lifetime Imaging Microscopy

Live-cell microscopy is now routinely used to monitor the activities of the genetically encoded biosensor proteins that are designed to directly measure specific cell signaling events inside cells, tissues, or organisms. Most fluorescent biosensor proteins rely on Förster resonance energy transfer (FRET) to report conformational changes in the protein that occur in response to signaling events, and this is commonly measured with intensity-based ratiometric imaging methods. An alternative method for monitoring the activities of the FRET-based biosensor proteins is fluorescence lifetime imaging microscopy (FLIM). FLIM measurements are made in the time domain, and are not affected by factors that commonly limit intensity measurements. In this review, we describe the use of the digital frequency domain (FD) FLIM method for the analysis of FRET signals. We illustrate the methods necessary for the calibration of the FD FLIM system, and demonstrate the analysis of data obtained from cells expressing “FRET standard” fusion proteins. We then use the FLIM-FRET approach to monitor the changes in activities of two different biosensor proteins in specific regions of single living cells. Importantly, the factors required for the accurate determination and reproducibility of lifetime measurements are described in detail

Adaptively Determination of Model Order of SVD-based Harmonics and Interharmonics Estimation

The singular value decomposition (SVD) is one of the most popular methods in harmonics and interharmonics estimation. However, its accuracy strongly depends on the correctness of the selected model order. To this purpose, this work aims at contributing to the correct estimation of the model order. This is achieved by exploiting the energy of the singular values (SVs). Firstly, the relationship between one frequency component and its corresponding SVs is theoretically investigated. Secondly, a new indicator is proposed for determining the model order, which denotes the energy of the k-th pair of consecutive SVs. Thirdly, an adaptive threshold is defined for separating signal components from noise. This way, the number of components can be obtained for unknown noise levels. Finally, the effectiveness and robustness of the proposed method has been validated by simulations. They have been run implementing typical signals designed according to the harmonics and interharmonics measurements standard, the IEC standard 61000-4-7

Intravital microscopy of biosensor activities and intrinsic metabolic states

Intravital microscopy (IVM) is an imaging tool that is capable of detecting subcellular signaling or metabolic events as they occur in tissues in the living animal. Imaging in highly scattering biological tissues, however, is challenging because of the attenuation of signal in images acquired at increasing depths. Depth-dependent signal attenuation is the major impediment to IVM, limiting the depth from which significant data can be obtained. Therefore, making quantitative measurements by IVM requires methods that use internal calibration, or alternatively, a completely different way of evaluating the signals. Here, we describe how ratiometric imaging of genetically encoded biosensor probes can be used to make quantitative measurements of changes in the activity of cell signaling pathways. Then, we describe how fluorescence lifetime imaging can be used for label-free measurements of the metabolic states of cells within the living animal

Statistical Behavior of PMU Measurement Errors: An Experimental Characterization

Different power system applications based on synchrophasors measured in different nodes of the electric grid require information about the statistical distribution of the errors introduced by the phasor measurement units (PMUs). The performance of these applications can be significantly affected by possible incorrect assumptions. The Gaussian distribution has been historically assumed in most of the approaches, but some more recent studies suggest the possibility of considering different distributions for more accurate modeling of the actual situation. In this article, proper statistical tools applied to the results achieved through a high-performance experimental test system are proposed to assess the statistical distribution of PMU errors under controlled steady-state conditions, thus providing a basis for defining suitable models to be used in specific applications

Tracking power system events with accuracy-based PMU adaptive reporting rate

Fast dynamics and transient events are becoming more and more frequent in power systems, due to the high penetration of renewable energy sources and the consequent lack of inertia. In this scenario, Phasor Measurement Units (PMUs) are expected to track the monitored quantities. Such functionality is related not only to the PMU accuracy (as per the IEC/IEEE 60255-118-1 standard) but also to the PMU reporting rate (RR). High RRs allow tracking fast dynamics, but produce many redundant measurement data in normal conditions. In view of an effective tradeoff, the present paper proposes an adaptive RR mechanism based on a real-time selection of the measurements, with the target of preserving the information content while reducing the data rate. The proposed method has been tested considering real-world datasets and applied to four different PMU algorithms. The results prove the method effectiveness in reducing the average data throughput as well as its scalability at PMU concentrator or storage level

Broadband classification and statistics of echoes from aggregations of fish measured by long-range, mid-frequency sonar

Author Posting. © Acoustical Society of America, 2017. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 141 (2017): 4354, doi:10.1121/1.4983446.For horizontal-looking sonar systems operating at mid-frequencies (1–10 kHz), scattering by fish with resonant gas-filled swimbladders can dominate seafloor and surface reverberation at long-ranges (i.e., distances much greater than the water depth). This source of scattering, which can be difficult to distinguish from other sources of scattering in the water column or at the boundaries, can add spatio-temporal variability to an already complex acoustic record. Sparsely distributed, spatially compact fish aggregations were measured in the Gulf of Maine using a long-range broadband sonar with continuous spectral coverage from 1.5 to 5 kHz. Observed echoes, that are at least 15 decibels above background levels in the horizontal-looking sonar data, are classified spectrally by the resonance features as due to swimbladder-bearing fish. Contemporaneous multi-frequency echosounder measurements (18, 38, and 120 kHz) and net samples are used in conjunction with physics-based acoustic models to validate this approach. Furthermore, the fish aggregations are statistically characterized in the long-range data by highly non-Rayleigh distributions of the echo magnitudes. These distributions are accurately predicted by a computationally efficient, physics-based model. The model accounts for beam-pattern and waveguide effects as well as the scattering response of aggregations of fish.This research was supported by the U.S. Office of Naval Research, the National Oceanographic Partnership Program, NOAA, WHOI, and the Oceanographer of the U.S. Navy

Contributions to the multi-frequency control of gridtied voltage source converters

El interés por la producción de energía limpia está en aumento y la generación de este tipo de energía se puede fomentar mediante la instalación de generadores locales. Dichos generadores son conectados a la red de distribución a través de convertidores de potencia. Al mismo tiempo el número de cargas conectadas a la red está incrementando y con ello el número de cargas no lineales. Estas últimas consumen corrientes armónicas y esto provoca distorsión armónica a la red. En esta tesis se estudia y se presentan contribuciones en el control de los convertidores de potencia para que al mismo tiempo que se inyecta potencia, el convertidor sea capaz de actuar adecuadamente frente a la distorsión armónica del voltaje de la red (control multifrecuencial). En primer lugar, esta tesis cubrirá el estudio de las diferentes técnicas de control de corrientes armónicas y también de las diferentes técnicas de sincronización y detección de componentes armónicas de tensión presentes en la red. En cuanto al cálculo de referencias de corrientes armónicas, se explican las principales variantes dependiendo de la funcionalidad deseada y se estudia la entrega de potencia instantánea constante incluso con red distorsionada. Además, se propone un nuevo método de cálculo para eliminar las principales oscilaciones de potencia sin exceder las limitaciones de distorsión de corrientes. También se describen las limitaciones del convertidor cuando se trabaja con componentes fundamentales y armónicas. Se analizan los principales saturadores multifrecuenciales para evitar la sobremodulación y se propone un nuevo saturador que no empeora la dinámica total del sistema y siempre consigue el mínimo THD de corriente. Por último, se aborda la problemática de la distorsión armónica del voltaje de red. Primero se estudia la compensación de las corrientes consumidas por cargas locales y después se propone la compensación directa de la tensión del PCC. En esta tesis se intenta incrementar el número de funcionalidades que puede desempeñar el convertidor para que además de entregar potencia, sea capaz de mejorar la calidad de la red, sin exceder las limitaciones físicas del convertidor. Cada una de las contribuciones es validada mediante resultados de simulación y experimentales