62 research outputs found
Image Embedding of PMU Data for Deep Learning towards Transient Disturbance Classification
This paper presents a study on power grid disturbance classification by Deep
Learning (DL). A real synchrophasor set composing of three different types of
disturbance events from the Frequency Monitoring Network (FNET) is used. An
image embedding technique called Gramian Angular Field is applied to transform
each time series of event data to a two-dimensional image for learning. Two
main DL algorithms, i.e. CNN (Convolutional Neural Network) and RNN (Recurrent
Neural Network) are tested and compared with two widely used data mining tools,
the Support Vector Machine and Decision Tree. The test results demonstrate the
superiority of the both DL algorithms over other methods in the application of
power system transient disturbance classification.Comment: An updated version of this manuscript has been accepted by the 2018
IEEE International Conference on Energy Internet (ICEI), Beijing, Chin
Mitigating Multi-Stage Cascading Failure by Reinforcement Learning
This paper proposes a cascading failure mitigation strategy based on
Reinforcement Learning (RL) method. Firstly, the principles of RL are
introduced. Then, the Multi-Stage Cascading Failure (MSCF) problem is presented
and its challenges are investigated. The problem is then tackled by the RL
based on DC-OPF (Optimal Power Flow). Designs of the key elements of the RL
framework (rewards, states, etc.) are also discussed in detail. Experiments on
the IEEE 118-bus system by both shallow and deep neural networks demonstrate
promising results in terms of reduced system collapse rates.Comment: This paper has been accepted and presented in the IEEE ISGT-Asia
conference in 201
Optimization of Battery Energy Storage to Improve Power System Oscillation Damping
A placement problem for multiple Battery Energy Storage System (BESS) units
is formulated towards power system transient voltage stability enhancement in
this paper. The problem is solved by the Cross-Entropy (CE) optimization
method. A simulation-based approach is adopted to incorporate higher-order
dynamics and nonlinearities of generators and loads. The objective is to
maximize the voltage stability index, which is setup based on certain
grid-codes. Formulations of the optimization problem are then discussed.
Finally, the proposed approach is implemented in MATLAB/DIgSILENT and tested on
the New England 39-Bus system. Results indicate that installing BESS units at
the optimized location can alleviate transient voltage instability issue
compared with the original system with no BESS. The CE placement algorithm is
also compared with the classic PSO (Particle Swarm Optimization) method, and
its superiority is demonstrated in terms of a faster convergence rate with
matched solution qualities.Comment: This paper has been accepted by IEEE Transactions on Sustainable
Energy and now still in online-publication phase, IEEE Transactions on
Sustainable Energy. 201
Optimal Battery Energy Storage Placement for Transient Voltage Stability Enhancement
A placement problem for multiple Battery Energy Storage System (BESS) units
is formulated towards power system transient voltage stability enhancement in
this paper. The problem is solved by the Cross-Entropy (CE) optimization
method. A simulation-based approach is adopted to incorporate higher-order
dynamics and nonlinearities of generators and loads. The objective is to
maximize the voltage stability index, which is set up based on certain
grid-codes. Formulations of the optimization problem are then discussed.
Finally, the proposed approach is implemented in MATLAB/DIgSILENT and tested on
the New England 39-Bus system. Results indicate that installing BESS units at
the optimized location can alleviate transient voltage instability issue
compared with the original system with no BESS. The CE placement algorithm is
also compared with the classic PSO (Particle Swarm Optimization) method, and
its superiority is demonstrated in terms of fewer iterations for convergence
with better solution qualities.Comment: This paper has been accepted by the 2019 IEEE PES General Meeting at
Atlanta, GA in August 201
Design and Realisation of High Accuracy Emissivity Measurement Instruments for Radiation Thermometry
Emissivity is the quantity representing the radiative properties of materials that must be prior measured precisely to undertake accurate measurements for radiation thermometry. This work presents the development and validation of three emissivity measurement instruments to undertake studies on emissivity behaviours for materials with complex surface conditions from 200 to 1150 °C. These instruments aim to offer accurate emissivity references for use in non-contact temperature measurements and materials science
Photoelectrochemical and electrochemical ratiometric aptasensing: a case study of streptomycin
There has been much interest in constructing ratiometric sensors using different sensing techniques because of
their synergistic effect, although the simultaneous collection of the signals is challenging. Herein, we propose a
ratiometric aptasensing strategy based on the dual-detection model with a photoelectrochemical (PEC) “signalon” and an electrochemical (EC) “signal-off”. As a proof-of-concept study, CdTe quantum dots (CdTe QDs) and a
methylene blue-labeled aptamer (MB-Apt) were used to generate PEC and EC signals in the sensing system. The
target-induced conformational change of MB-Apt pushed MB away from the electrode, thereby decreasing the EC
signal; at the same time, the reduced steric hindrance favored the restoration of the PEC signal from the CdTe
QDs. Thus, this PEC-EC strategy can achieve the PEC “signal-on” and EC “signal-off” states simultaneously, as
well as allowing quantitative analysis of the target based on the ratio of the current intensities. As a model
application, an aptasensor fabricated for streptomycin detection showed a wide linear range from 0.03 to 100 μM
with a detection limit of 10 nM (S/N = 3). The proposed sensing platform displayed superior analytical properties compared with methods based on PEC or EC alone. Our work provides an efficient dual-detection modelbased ratiometric strategy for advanced analysis, and paves the way to the simultaneous acquisition of signals
Transportation Density Reduction Caused by City Lockdowns Across the World during the COVID-19 Epidemic: From the View of High-resolution Remote Sensing Imagery
As the COVID-19 epidemic began to worsen in the first months of 2020,
stringent lockdown policies were implemented in numerous cities throughout the
world to control human transmission and mitigate its spread. Although
transportation density reduction inside the city was felt subjectively, there
has thus far been no objective and quantitative study of its variation to
reflect the intracity population flows and their corresponding relationship
with lockdown policy stringency from the view of remote sensing images with the
high resolution under 1m. Accordingly, we here provide a quantitative
investigation of the transportation density reduction before and after lockdown
was implemented in six epicenter cities (Wuhan, Milan, Madrid, Paris, New York,
and London) around the world during the COVID-19 epidemic, which is
accomplished by extracting vehicles from the multi-temporal high-resolution
remote sensing images. A novel vehicle detection model combining unsupervised
vehicle candidate extraction and deep learning identification was specifically
proposed for the images with the resolution of 0.5m. Our results indicate that
transportation densities were reduced by an average of approximately 50% (and
as much as 75.96%) in these six cities following lockdown. The influences on
transportation density reduction rates are also highly correlated with policy
stringency, with an R^2 value exceeding 0.83. Even within a specific city, the
transportation density changes differed and tended to be distributed in
accordance with the city's land-use patterns. Considering that public
transportation was mostly reduced or even forbidden, our results indicate that
city lockdown policies are effective at limiting human transmission within
cities.Comment: 14 pages, 7 figures, submitted to IEEE JSTAR
Quantitative thermal imaging using single-pixel Si APD and MEMS mirror
Accurate quantitative temperature measurements are difficult to achieve using
focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of
calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE),
which is the dependence of an infrared temperature measurement on the area surrounding the
target area, is a major contributor to this problem and cannot be reduced using glare stops.
Measurements are affected by power received from outside the field-of-view (FOV), leading
to increased measurement uncertainty. In this work, we present a micromechanical systems
(MEMS) mirror based scanning thermal imaging camera with reduced measurement
uncertainty compared to focal-plane array based systems. We demonstrate our flexible
imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to
enable the measurement of lower target temperatures with an effective wavelength of 1 µm
and compare results with a Si photodiode. We compare measurements from our APD thermal
imaging instrument against a commercial bolometer based focal-plane array camera. Our
scanning approach results in a reduction in SSE related temperature error by 66 °C for the
measurement of a spatially uniform 800 °C target when the target aperture diameter is
increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring
target temperatures below 700 °C, over these near infrared wavelengths, with D* related
measurement uncertainty of ± 0.5 °C
Low-Cost Hyperspectral Imaging with A Smartphone.
Recent advances in smartphone technologies have opened the door to the development of accessible, highly portable sensing tools capable of accurate and reliable data collection in a range of environmental settings. In this article, we introduce a low-cost smartphone-based hyperspectral imaging system that can convert a standard smartphone camera into a visible wavelength hyperspectral sensor for ca. £100. To the best of our knowledge, this represents the first smartphone capable of hyperspectral data collection without the need for extensive post processing. The Hyperspectral Smartphone's abilities are tested in a variety of environmental applications and its capabilities directly compared to the laboratory-based analogue from our previous research, as well as the wider existing literature. The Hyperspectral Smartphone is capable of accurate, laboratory- and field-based hyperspectral data collection, demonstrating the significant promise of both this device and smartphone-based hyperspectral imaging as a whole
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