369 research outputs found
Modal Transformation based Fault Location in Radial Distribution Network
No full textThis paper introduces the technique of fault distance estimation based on modal transformation and signal processing. The recorded faulted phase currents are applied to the Karrenbauer model transformation and these model component currents are decomposed into detail coefficients by the use of Daubechies wavelet, db6. The fault recorder installed at the terminal of the feeder records different time delays between the modal components. In order to find fault distance, the time delay values and modal components velocity are used in traveling wave theory. This paper compares two different conditions: the first condition does not use a modal transformation and the second condition uses a modal transformation. When using modal transformation conditions, three different coefficient levels (detail coefficient level 1 (D1); the combination of detail coefficient level 1+2 (D1+2) and the combination of detail coefficient level 1+2+3 (D1+2+3) ) are used to estimate the fault distance. Different fault types with different fault locations are created in MATLAB simulation
Consistency in the AMSR-E snow products: groundwork for a coupled snowfall and SWE algorithm
No full text2019 Fall.Includes bibliographical references.Snow is an important wintertime property because it is a source of freshwater, regulates land-atmosphere exchanges, and increases the surface albedo of snow-covered regions. Unfortunately, in-situ observations of both snowfall and snow water equivalent (SWE) are globally sparse and point measurements are not representative of the surrounding area, especially in mountainous regions. The total amount of land covered by snow, which is climatologically important, is fairly straightforward to measure using satellite remote sensing. The total SWE is hydrologically more useful, but significantly more difficult to measure. Accurately measuring snowfall and SWE is an important first step toward a better understanding of the impacts snow has for hydrological and climatological purposes. Satellite passive microwave retrievals of snow offer potential due to consistent overpasses and the capability to make measurements during the day, night, and cloudy conditions. However, passive microwave snow retrievals are less mature than precipitation retrievals and have been an ongoing area of research. Exacerbating the problem, communities that remotely sense snowfall and SWE from passive microwave sensors have historically operated independently while the accuracy of the products has suffered because of the physical and radiometric dependency between the two. In this study, we assessed the relationship between the Northern Hemisphere snowfall and SWE products from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). This assessment provides insight into regimes that can be used as a starting point for future improvements using coupled snowfall and SWE algorithm. SnowModel, a physically-based snow evolution modeling system driven by the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) reanalysis, was employed to consistently compare snowfall and SWE by accounting for snow evolution. SnowModel has the ability to assimilate observed SWE values to scale the amount of snow that must have fallen to match the observed SWE. Assimilation was performed using AMSR-E, Canadian Meteorological Centre (CMC) Snow Analysis, and Snow Data Assimilation System (SNODAS) SWE to infer the required snowfall for each dataset. Observed AMSR-E snowfall and SWE were then compared to the MERRA-2 snowfall and SnowModel-produced SWE as well as SNODAS and CMC inferred snowfall and observed SWE. Results from the study showed significantly different snowfall and SWE bias patterns observed by AMSR-E. Specifically, snowfall was underestimated nearly globally and SWE had pronounced regions of over and underestimation. Snowfall and SWE biases were found to differ as a function of surface temperature, snow class, and elevation
Modal Transformation based Fault Location in Radial Distribution Network
No full textThis paper introduces the technique of fault distance estimation based on modal transformation and signal processing. The recorded faulted phase currents are applied to the Karrenbauer model transformation and these model component currents are decomposed into detail coefficients by the use of Daubechies wavelet, db6. The fault recorder installed at the terminal of the feeder records different time delays between the modal components. In order to find fault distance, the time delay values and modal components velocity are used in traveling wave theory. This paper compares two different conditions: the first condition does not use a modal transformation and the second condition uses a modal transformation. When using modal transformation conditions, three different coefficient levels (detail coefficient level 1 (D1); the combination of detail coefficient level 1+2 (D1+2) and the combination of detail coefficient level 1+2+3 (D1+2+3) ) are used to estimate the fault distance. Different fault types with different fault locations are created in MATLAB simulation
Coordinated Design of PSS and STATCOM for Power System Stability Improvement Using Bacteria Foraging Algorithm
No full textThis paper presents the coordinated controller design of static synchronous compensator (STATCOM) and power system stabilizers (PSSs) for power system stability improvement. Coordinated design problem of STATCOM-based controller with multiple PSSs is formulated as an optimization problem and optimal controller parameters are obtained using bacteria foraging optimization algorithm. By minimizing the proposed objective function, in which the speed deviations between generators are involved; stability performance of the system is improved. The nonlinear simulation results show that coordinated design of STATCOM-based controller and PSSs improve greatly the system damping oscillations and consequently stability improvement
Design Considerations of PV Water Pumping and Rural Electricity System (2011) in Lower Myanmar
No full textPhotovoltaic (PV) systems provides a viable means of
power generation for applications like powering residential
appliances, electrification of villages in rural areas, refrigeration and
water pumping. Photovoltaic-power generation is reliable. The
operation and maintenance costs are very low. Since Myanmar is a
land of plentiful sunshine, especially in central and southern regions
of the country, the solar energy could hopefully become the final
solution to its energy supply problem in rural area
Improved Parameterization of Snow Albedo in WRF + Noah: Methodology Based on a Severe Snow Event on the Tibetan Plateau
No full textSnowfall and the subsequent evolution of the snowpack have a large effect on the surface energy balance and water cycle of the Tibetan Plateau (TP). The effects of snow cover can be represented by the WRF coupled with a land surface scheme. The widely used Noah scheme is computationally efficient, but its poor representation of albedo needs considerable improvement. In this study, an improved albedo scheme is developed using a satellite-retrieved albedo that takes snow depth and age into account. Numerical experiments were then conducted to simulate a severe snow event in March 2017. The performance of the coupled WRF/Noah model, which implemented the improved albedo scheme, is compared against the model’s performance using the default Noah albedo scheme and against the coupled WRF/CLM that applied CLM albedo scheme. When the improved albedo scheme is implemented, the albedo overestimation in the southeastern TP is reduced, reducing the RMSE of the air temperature by 0.7°C. The improved albedo scheme also attains the highest correlation between the satellite-derived and the model-estimated albedo, which provides for a realistic representation of both the snow water equivalent (SWE) spatial distribution in the heavy snowbelt (SWE > 6 mm) and the maximum SWE in the eastern TP. The underestimated albedo in the coupled WRF/CLM leads to underestimating the regional maximum SWE and a consequent failure to estimate SWE in the heavy snowbelt accurately. Our study demonstrates the feasibility of improving the Noah albedo scheme and provides a theoretical reference for researchers aiming to improve albedo schemes further.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote Sensin
Study and Analysis of Machine Parameters Effect on Power System Stability
No full textThe stability study of a power system is an important factor in the planning or increasing of facilities. The studies are helpful in determining such thing as nature of the relaying system needed, critical clearing time of circuit breakers, voltage level, and transfer capability between systems. In this paper, the effects of machine parameters (inertia constant, damping constant and transient reactance) on the critical clearing time of the power system stability have been analyzed. These parameters are the main contribution to the angular acceleration and power transfer capability that affected the power system stability. The analysis has been done for two types of power system: single machine infinite bus system and multi-machine system. From the analysis, it is found that the stability of the system is affected by studied parameters and important in the design of the improving power system stability and protection system
Energy Management of Stand-Alone Hydrokinetic Power Supply System with Battery Energy Storage for Rural Electrification
No full textIn this paper, optimal energy management for a stand-alone hydrokinetic power supply system with a battery storage system isproposed to sufficiently explore hydrokinetic energy for customers at the demand side. The management of power flow aims tooptimal energy supply subject to a number of constraints, such as power balance, hydrokinetic power output, and battery capacity. The hydrokinetic turbine is connected with permanent magnet synchronous generator (PMSG), power electronic devicesand battery bank. The battery bank is used to store the surplus of energy when the load demand is low and discharges again thestored energy to the load when hydrokinetic power is not sufficient to supply the load. The proposed system can meet the load for every hour of the days without interruption. The average daily load requirement and available hydrokinetic power are calculated for three seasons. In this research, the average daily load requirement of the summer season is chosen because it is the highest in energy consumption from three seasons. The simulation results show that the management of the system is satisfied between available hydrokinetic power and load deman
Global re-analysis datasets to improve hydrological assessment and snow water equivalent estimation in a sub-Arctic watershed
No full textHydrological modelling in the Canadian sub-Arctic is hindered by sparse meteorological and snowpack data. The snow water equivalent (SWE) of the winter snowpack is a key predictor and driver of spring flow, but the use of SWE data in hydrological applications is limited due to high uncertainty. Global re-analysis datasets that provide gridded meteorological and SWE data may be well suited to improve hydrological assessment and snowpack simulation. To investigate representation of hydrological processes and SWE for application in hydropower operations, global re-analysis datasets covering 1979-2014 from the European Union FP7 eartH2Observe project are applied to global and local conceptual hydrological models. The recently developed Multi-Source Weighted-Ensemble Precipitation (MSWEP) and the WATCH Forcing Data applied to ERA-Interim data (WFDEI) are used to simulate snowpack accumulation, spring snowmelt volume and annual streamflow. The GlobSnow-2 SWE product funded by the European Space Agency with daily coverage from 1979 to 2014 is evaluated against in situ SWE measurement over the local watershed. Results demonstrate the successful application of global datasets for streamflow prediction, snowpack accumulation and snowmelt timing in a snowmelt-driven sub-Arctic watershed. The study was unable to demonstrate statistically significant correlations (p/0.05) among the measured snowpack, global hydrological model and GlobSnow-2 SWE compared to snowmelt runoff volume or peak discharge. The GlobSnow-2 product is found to under-predict late-season snowpacks over the study area and shows a premature decline of SWE prior to the true onset of the snowmelt. Of the datasets tested, the MSWEP precipitation results in annual SWE estimates that are better predictors of snowmelt volume and peak discharge than the WFDEI or GlobSnow-2. This study demonstrates the operational and scientific utility of the global re-analysis datasets in the sub-Arctic, although knowledge gaps remain in global satellite-based datasets for snowpack representation, for example the relationship between passive-microwave-measured SWE to snowmelt runoff volume.Water Resource
Validity and reliability of the Swedish version of the Children’s Sleep Habits Questionnaire (CSHQ-SWE)
No full textBackground: To translate and culturally adapt the Children’s Sleep Habits Questionnaire (CSHQ) to a Swedish version, CSHQ-SWE, and to assess its validity and reliability for use with children with attention deficit hyperactivity disorder (ADHD). Methods: A total of 84 children with ADHD (51 boys and 33 girls; 6–12 years) and parents (7 men and 77 women; 28–51 years) were included in the study. CSHQ was translated and culturally adapted to Swedish, and assessed for concurrent validity with sleep actigraphy (analyzed by Kendall’s Tau) and for reliability by internal consistency (analyzed by McDonald’s Omega H). Face and content validity was evaluated by parents (n = 4) and healthcare professionals (n = 6) qualitatively (comprehensiveness, relevance, and comprehensibility assessed by interviews and analyzed by thematic analysis) and quantitatively (analyzed by content validity ratio and content validity index for 33 items and four non-scored inquiries). Results: Parent-reported sleep problems (CSHQ-SWE total score) were moderately correlated with less “Sleep Efficiency” (Tau = −0.305; p < 0.001) measured by sleep actigraphy. Parent-reported problems with “Sleep Onset Delay” was moderately correlated with measured time for ”Sleep Onset Latency” (Tau = 0.433; p < 0.001). Parent-reported problems with “Night Wakings” were weakly correlated with measured time for “Wake After Sleep Onset” (Tau = 0.282; p < 0.001). Parents estimation of “Total daily sleep duration” was moderately correlated with measured “Total Sleep Time” (Tau = 0.386; p < 0.001). Five of the seven subscales reached an acceptable level for internal consistency (McDonald’s Omega H > 0.700). Comprehensiveness, relevance, and comprehensibility of CSHQ-SWE were satisfactory overall. Content validity ratio was 0.80 to 1.00 for six items, 0.00 to 0.60 for 22 items, and < 0.00 for nine items. Content validity index was 0.22. Conclusions: CSHQ-SWE demonstrated acceptable concurrent validity with objectively measured sleep and internal consistency, whereas the overall results of face and content validity assessment varied. The instrument needs to be further evaluated regarding construct validity, responsiveness, test-retest reliability, and its generalization to other populations. © The Author(s) 2024</p
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