Modified S transform and ELM algorithms and their applications in power quality analysis

Zhang, Shuqing; Pan, Li; Zhang, Liguo; Li, Hongjin; Jiang, Wanlu; Hu, Yongtao

doi:10.1016/j.neucom.2015.12.050

Cited by 46 publications

(28 citation statements)

References 33 publications

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“…This improvement can be attributed to the formation of uniformly dispersed ultrafine Li 2 S nanoparticles in highly conductive NCNF networks, which significantly reduces the energy barrier for the activation of Li 2 S. Two cathodic peaks are observed at ≈2.31 and 2.02 V due to the multistep reduction of sulfur with Li in organic electrolyte. The former is associated with the solid‐to‐liquid phase transition from S 8 to high‐order Li 2 S x (4 ≤ x ≤ 8), while the latter is due to the further reduction of soluble polysulfides to solid‐state Li 2 S . In the cycles sweeping between 1.7 and 2.8 V, the cathodic peaks are highly overlapped, suggesting a high degree of reversibility of the multistep redox reactions in Li 2 S@NCNF electrodes.…”

Section: Resultsmentioning

confidence: 99%

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Wang

et al. 2017

Advanced Energy Materials

158

104

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rate of active mass and high electrode polarization; ii) the dissolution of sulfur to soluble polysulfides in an organic electrolyte induces severe loss of active mass and notorious shuttle effect; iii) the huge volume change of sulfur (about 80%) upon lithiation/deli thiation results in fast pulverization and failure of the cathode; iv) highly reactive metallic-Li anode pairs with a flammable organic electrolyte to trigger serious safety hazards. The formation of dendrites on metallic-Li anodes during cycling may penetrate the separator and cause short-circuiting within the cell. Even though great efforts have been devoted to solving this problem, [7][8][9][10][11] the commercialization of metallic-Li anodes has not yet been achieved in rechargeable batteries with a liquid electrolyte.Replacing the sulfur with its fully lithiated phase, lithium sulfide (Li 2 S), paves an attractive way to partially address the above issues because of its high capacity of 1166 mA h g −1 and superior structural stability to sulfur for Li uptake. [12][13][14][15] With as high as 66.67 at% of Li in the structure, the Li 2 S phase already occupies the maximum volume to avoid volume expansion during lithiation/delithiation. [16,17] This remarkable feature makes it particularly suitable for manufacturing the electrode with high mass and energy loading, in which the negative effect of volume variation could not accumulate with thicker electrodes. The Li 2 S could also be the promising substitute of metallic Li to pair with Li-free high-capacity anode materials, such as Si-based materials, giving rise to the cell with attractive energy density and high safety. [13] Similar to sulfur, however, the Li 2 S cathode also suffers from low electronic conductivity (10 −13 S cm −1 ) and polysulfide shuttle problem. Confining micro/nanosized Li 2 S within conductive carbonaceous matrix, such as carbon nanotubes, graphene, and porous carbon, could significantly enhance the reaction kinetics and structural stability of Li 2 S cathodes for electrochemical cycling. [17][18][19][20][21][22][23][24][25][26] But the high melting point (1372 °C) of Li 2 S [27] makes it difficult to be conformably sealed into the carbon hosts by popular meltinginfiltration approach for making sulfur/carbon composites. Various alternative methods, such as ball-milling, solution impregnation, or precipitation from organic lithium compounds, have been developed to yield nanostructured Li 2 S/C composites with impressive performance. [16,[24][25][26][28][29][30][31][32] Nevertheless, there are still some obstacles for the implementation of Li 2 S cathodes in Li-S cells. For example, the high capacity Lithium-sulfur (Li-S) batteries are a very appealing power source with extremely high energy density. But the use of a metallic-Li anode causes serious safety hazards, such as short-circuiting and explosion of the cells. Replacing a sulfur cathode with a fully-lithiated lithium sulfide (Li 2 S) to pair with metallic-Li-free high-capacity anodes paves a feasible way to address this...

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Section: Resultsmentioning

confidence: 99%

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Wang

et al. 2017

Advanced Energy Materials

158

104

View full text Add to dashboard Cite

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“…Appropriate features must be selected to ensure classification efficiency. The PQDs include not only stationary signals such as flickers but also nonstationary signals such as oscillatory transients and notches, so signal‐processing tools like the wavelet transform (WT), the Gabor transform, the S‐transform (ST), and empirical mode decomposition (EMD) readily apply to feature extraction. Wavelet transform, unfortunately, is noise‐sensitive and ill‐suited to selecting proper basic wavelet functions; furthermore, it is not capable of directly providing the distinctive features which make each disturbance unique and salient.…”

Section: Introductionmentioning

confidence: 99%

“…Although ST has properties superior to WT and the features obtained from ST are distinct, understandable, and immune to noise, the oversize computational load of ST (O(N 2 log N )) limits its application in real‐time environments . Additionally, the resolutions in the ST's time domain and frequency domain cannot be optimized simultaneously due to constraint under the Heisenberg uncertainty principle . This renders ST unable to accurately identify both time and frequency domain disturbances simultaneously.…”

Section: Introductionmentioning

confidence: 99%

“…The ELM succeeds in many practical applications such as classification, feature selection, regression, and other applications and satisfies the 2 requirements described above. Zhang et al, for example, found that the ELM outperforms back propagation and SVM algorithms as a PQD classifier. Extreme learning machine requires that the quantity of hidden nodes be kept at a minimum, however, which can lead to the misclassification of boundary examples (which weakens its overall performance).…”

Section: Introductionmentioning

confidence: 99%

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Classification of power quality disturbances using dual strong tracking filters and rule-based extreme learning machine

Chen

Xiao

2018

Int Trans Electr Energ Syst

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SummaryThe classification of single and simultaneous power quality disturbances (PQDs) has become an issue of concern in the power system field. This paper proposes a novel approach based on dual strong tracking filters (STFs) and the rule-based extreme learning machine (ELM) for detecting and classifying single and simultaneous PQDs. Dual STFs are a hybrid structure of a low-order STF and high-order STF. The fading factor of the low-order STF is used to detect sudden changes in PQDs; the fundamental amplitude variation is tracked by the high-order STF. Six distinctive features extracted from the dual STFs serve as the input to the ELM classifier for PQD classification. The rule-based ELM technique, which is equipped with certain decision rules, can improve the ELM classification accuracy when the number of hidden nodes is insufficient. In consideration of special structures of matrices, the real-time computation of the proposed method can be realized. A PQD dataset is generated in MATLAB for simulation experiments; the results show that 20 types of PQDs, including single and simultaneous disturbances, can be accurately classified under the different levels of noise via the proposed method. The method is also tested on a real recorded waveform to verify its effectiveness in PQD classification. | INTRODUCTIONIn recent years, power quality (PQ) has become a critical issue for researchers and developers concerned with power system stability and the propagation of PQ-related effects in the grid. Poor PQ can lead to maloperations or failures of sensitive loads such as embedded systems or electronic devices, ultimately incurring substantial cost for end users. The increased use of unbalanced and nonlinear loads, line faults, switching devices, and power electric converters represents a wide variety of disturbances. Faults among lines to ground, unbalanced, or nonlinear loads can lead to amplitude (AM) variations of the fundamental frequency such as sags, swells, and interruptions. Flickers andThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…TT transform was proposed by Pinnegar and Mansinha [20,21] as a new transform in 2003, which came from the inverse Fourier form of the time-frequency analysis S transform [22][23][24][25]. Onedimensional time series is expressed as a two-dimensional time-time series by TT transform, which is good for observing the local features of the signal [26].…”

Section: Introductionmentioning

confidence: 99%

A Novel Interference Detection Method of STAP Based on Simplified TT Transform

Wang

Zhang

Liu

et al. 2017

Mathematical Problems in Engineering

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Training samples contaminated by target-like signals is one of the major reasons for inhomogeneous clutter environment. In such environment, clutter covariance matrix in STAP (space-time adaptive processing) is estimated inaccurately, which finally leads to detection performance reduction. In terms of this problem, a STAP interference detection method based on simplified TT (timetime) transform is proposed in this letter. Considering the sparse physical property of clutter in the space-time plane, data on each range cell is first converted into a discrete slow time series. Then, the expression of simplified TT transform about sample data is derived step by step. Thirdly, the energy of each training sample is focalized and extracted by simplified TT transform from energy-variant difference between the unpolluted and polluted stage, and the physical significance of discarding the contaminated samples is analyzed. Lastly, the contaminated samples are picked out in light of the simplified TT transform-spectrum difference. The result on Monte Carlo simulation indicates that when training samples are contaminated by large power target-like signals, the proposed method is more effective in getting rid of the contaminated samples, reduces the computational complexity significantly, and promotes the target detection performance compared with the method of GIP (generalized inner product).

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Modified S transform and ELM algorithms and their applications in power quality analysis

Cited by 46 publications

References 33 publications

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Classification of power quality disturbances using dual strong tracking filters and rule-based extreme learning machine

A Novel Interference Detection Method of STAP Based on Simplified TT Transform

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Modified S transform and ELM algorithms and their applications in power quality analysis

Cited by 46 publications

References 33 publications

Freestanding Flexible Li2S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Freestanding Flexible Li2S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Classification of power quality disturbances using dual strong tracking filters and rule-based extreme learning machine

A Novel Interference Detection Method of STAP Based on Simplified TT Transform

Contact Info

Product

Resources

About

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Freestanding Flexible Li₂S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries