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Hilbert spectrum of c is2 (t). 

Hilbert spectrum of c is2 (t). 

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Conference Paper
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This paper describes a platform for obtaining and analyzing real-time measurements in Microgrids. A key building block in this platform is the Empirical Mode Decomposition (EMD) used to analyze the electrical voltage and current waveforms to identify the instantaneous frequency and amplitude of the monocomponents of the original signal. The method...

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Article
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This paper describes a platform for obtaining and analyzing real-time measurements in Microgrids. A key building block in this platform is the Empirical Mode Decomposition (EMD) used to analyze the electrical voltage and current waveforms to identify the instantaneous frequency and amplitude of the monocomponents of the original signal. The method...

Citations

... An extensive study of IEC Standard 6100-4-7 measuring methods states that these methods do not produce accurate results in environments with timevarying angular frequency [4]. Keeping the aforementioned problems of nonlinearities and time-varying quantities in mind, measurements and estimation in isolated microgrids should rather be based on instantaneous amplitude and frequency rather than the usage of average values [1,5]. With improved data acquisition-and measurement tools, the supervisory control systems in isolated microgrids may perform better actions, and earlier hidden distortions may be revealed. ...
Thesis
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Modern electrical systems have introduced distributed generations and power converters. This brings out different issues such as low inertia of the grids and an increasing number of harmonics and non linear distortions injected. However, the fluctuations of instantaneous frequency are arguably the most characteristic feature of microgrids. Frequency drift during step load change as well all quasi-periodic fluctuation has an impact on various conditions as generators’ prime movers and governor’s characteristic. Quasi periodic frequency fluctuations can have besides detrimental effect on electrical receivers’ work, especially electric motors will be affected. The thesis aims at providing a deep insight into the phenomena of non-constant instantaneous frequency. Origin of instantaneous frequency fluctuations are analyzed, tools for the phenomenon identification are proposed. These considerations are based on careful analysis of data from the Norwegian power system and behavior of three real marine systems onboard of a ro-ro ship with shaft generator, research-training ship during work of auxiliary generating sets as well as integrated power system of ship with electrical propulsion. For each ship, the cases of rough and calm sea are compared. To analyze data, the empirical mode decomposition algorithm and the Hilbert transform implemented in Matlab will be used.
... Within the fastest time scale of powerelectronics devices, such as that of the AC current controller, the assumption for stationary network may not be satisfactory since they are more sensitive and fragile to rapid fluctuations. As one example, in [7], an empirical mode decomposition analysis of the electrical voltage and current waveforms recorded from microgrids in the Royal University of Bhutan's College shows that the frequency of the microgrid network admittance model considering network dynamics is established in the frequency domain. In [10], a small signal impedance model of the dynamic network is established in the polar coordinates based on the transfer function matrix, and the generalized impedance concept of the network is defined. ...
Conference Paper
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In the traditional power systems, power flow studies focus on the stationary relationship of the active and reactive powers versus bus voltage under the quasi-steady state approximation. With increasing penetration of power electronics devices including renewable generations interfaced through converters , the system dynamical behaviour changes substantially. Due to the fast dynamics of converters, such as the AC current controller, the quasi-stationary state approximation may not be applicable. In order to catch the network characteristics accurately, we derive the explicit small-signal relation between instantaneous power and voltage vectors. Further, we study a simple power system model, which includes a network equation considering dynamics relationship and a swing equation. The numerical and analytical results demonstrate a novel negative resistance effect induced by generators on network dynamics. This effect may be weak for the traditional power systems, however, it may become significant for the new-generation power-electronic-based power systems.
... Steady and stable frequency has been one essential attribute of a stable electric power system and a pre-condition of stable operation. In this short communication, we discuss the notion of instantaneous frequency in electrical systems as first presented in [2] and use Hilbert Huang Transform [1] to detect its existence in a single-phase microgrid. This new notion might significantly change our understanding of the stability of electric power systems. ...
... Steady and stable frequency has been one essential attribute of a stable electric power system and a pre-condition of stable operation. In this poster, we discuss the notion of instantaneous frequency in electrical systems as first presented in [2] and use Hilbert Huang Transform [1] to detect its existence in a single-phase microgrid. This new notion might significantly change our understanding of the stability of electric power systems. ...
Research
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This short communication shows a case in which instantaneous frequencies are detected on synthetic signals by both Wavelet (WT) and Hilbert Huang Transform while Fourier Transnsform (FT) is not effective in identifying them. The selected synthetic signal is an example of how using FT in electric power systems with time varying frequencies, can mislead the interpretation of the results. The problem of leakeage is showcased in the example. This is confirmed by the results obtained from the analysis of a single-phase microgrid voltage in which Fourier based WT did not detect the presence of a time varying frequency on the microgrid, as this frequency fluctuates faster than the fundamental frequency.
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This paper aims to develop a combination method for the evaluation of power quality disturbances. First, we apply the Fast Fourier Transform, Wavelet Transform and Hilbert Huang Transform on a synthetic signal that represents typical behavior in a power system with high penetration of Renewable Energies. Then, we combine the methods to extract the best of each of these and achieve a better signal decomposition. The paper seeks to generate decision criteria on the method of analysis of signals to be used according to the application.
Chapter
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This paper describes the development and implementation of a methodology for the signal analysis in non-conventional energy systems. The proposed methodology involves the Hilbert-Huang transform supported by Empirical Mode Decomposition (EMD) to decompose one signal in its intrinsic mode function (IMF). A computational tool designed in MATLAB is used to detect oscillations and different frequencies of a non-linear and non-stationary system
Conference Paper
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The paper addresses the impact that time varying angular frequencies observed in electrical signals can have on the calculation and separation of components from the instantaneous electric power signal. Instantaneous power theories provide various methods for calculating the instantaneous power components in an electrical network. These methods are based on the basic assumption of constant fundamental frequency and harmonics that are multiple of the fundamental frequency. Recent field measurements in isolated electrical systems have however reported the existence of time varying angular frequencies or instantaneous frequencies. This new observation will affect the very foundation of the established methods for instantaneous power calculation and components separation. This paper analyses the separation of instantaneous average and oscillatory components of powers by using linear and non-linear filtering approaches in systems that exhibit time varying angular frequencies. The results of this comparison reveals the limitations of the assumption of fundamental and harmonic frequency when using linear filtering techniques in the presence of time varying angular frequencies. Non-linear filtering may offer a more robust and accurate estimation of the instantaneous values of powers and a power quality assessment that better reflects the actual system conditions.