准确统计地块现状负荷对配电网规划和负荷管理意义重大,供电部门现有各数据系统无统计地块负荷功能,传统统计方法依赖于人工,不适合大规模统计,为此提出一种基于地理信息系统(geographic information system,GIS)技术的统计方法。该方...准确统计地块现状负荷对配电网规划和负荷管理意义重大,供电部门现有各数据系统无统计地块负荷功能,传统统计方法依赖于人工,不适合大规模统计,为此提出一种基于地理信息系统(geographic information system,GIS)技术的统计方法。该方法首先根据城市总体规划和控制性详细规划建立地块GIS信息数据库;然后利用二次开发MapInfo功能,确定配用变压器与地块的耦合关系,模拟各配用变压器日负荷曲线,叠加统计各地块现状负荷。最后以某市配电网为例对全市地块现状负荷进行计算,结果表明该方法能够实现大规模地块现状负荷统计,提高统计效率和统计结果可靠性。展开更多
Designing an efficient distributed economic dispatch(DED)strategy for the smart grid(SG)in the presence of multiple generators plays a paramount role in obtaining various benefits of a new generation power syst em,suc...Designing an efficient distributed economic dispatch(DED)strategy for the smart grid(SG)in the presence of multiple generators plays a paramount role in obtaining various benefits of a new generation power syst em,such as easy implementation,low maintenance cos t,high energy efficiency,and strong robus tn ess agains t uncertainties.It has drawn a lot of interest from a wide variety of scientific disciplines,including power engineering,control theory,and applied mathematics.We present a state-of-the-art review of some theoretical advances toward DED in the SG,with a focus on the literature published since 2015.We systematically review the recent results on this topic and subsequently categorize them into distributed discrete-and continuous-time economic dispatches of the SG in the presence of multiple generators.After reviewing the literature,we briefly present some future research directions in DED for the SG,including the distributed security economic dispatch of the SG,distributed fast economic dispatch in the SG with practical constraints,efficient initialization-free DED in the SG,DED in the SG in the presence of smart energy storage batteries and flexible loads,and DED in the SG with artificial intelligence technologies.展开更多
For century, the need of change in the system of power grid is being felt and being considered as the most important change that we need in the modern era electrical system but before moving towards a new change the t...For century, the need of change in the system of power grid is being felt and being considered as the most important change that we need in the modern era electrical system but before moving towards a new change the things in past should be kept in mind so that there are better chances of great and beneficial change. The purpose of this research is to investigate the changes need to be incorporated in a conventional system to make a system self-sufficient and automated in order to make Electrical Power system more reliable. This paper assesses the current one way power system that is needed to be changed and has tried to provide an overview of the changes that we need in the system. The paper has focused more on the smart grid system and has explained the importance of smart grid system in terms of efficiency, automation and decision making capability in case of faults occurred on primitive grids with the help of comparative studies. The paper also highlighted the results in form of comparison with conventional grids and threw some light on the vision, control and the application of the smart grid system that will provide a two way system to the electrical network of the country and will make the distribution and consumption of energy more efficient also which is going to increase the reliability and accuracy in the system.展开更多
Due to the increasing share of renewable energy, new requirements are placed on control room software. Such software is often exclusive to the supplier, but other suppliers could offer new and better methods. For secu...Due to the increasing share of renewable energy, new requirements are placed on control room software. Such software is often exclusive to the supplier, but other suppliers could offer new and better methods. For security reasons, external applications often have no direct data access to control room software. Such software can provide information about the power grid via a periodic file transfer in CIM (Common Information Model) format. These files are often very large, containing complete records, delivering information not always relevant to the external applications. Extracting the relevant information required by external applications can be time-consuming, thus presenting a problem for time-critical applications. This paper presents a method allowing different applications to efficiently access the relevant data from the massive data stream contained in the CIM files. This method has been tested with a distribution system operator and clearly increases performance, allowing different applications to access the relevant data.展开更多
Given the increasing uncertainties in power supply and load,this paper proposes the concept of power source and grid coordination uniformity planning.In this approach,the standard deviation of the transmission line lo...Given the increasing uncertainties in power supply and load,this paper proposes the concept of power source and grid coordination uniformity planning.In this approach,the standard deviation of the transmission line load rate is considered as the uniformity evaluation index for power source and grid planning.A multi-stage and multi-objective optimization model of the power source and grid expansion planning is established to minimize the comprehensive cost of the entire planning cycle.In this study,the improved particle swarm optimization algorithm and genetic algorithm are combined to solve the model,thus improving the efficiency and accuracy of the solution.The analysis of a simple IEEE Garver’s 6-node system shows that the model and solution method are effective and feasible.Moreover,they are suitable for the coordinated planning of the power source and grid under a diversified nature of power supply and load.展开更多
The paper covers analysis and investigation of lighting automation system in low-traffic long-roads. The main objective is to provide optimal solution between expensive safe design that utilizes continuous street ligh...The paper covers analysis and investigation of lighting automation system in low-traffic long-roads. The main objective is to provide optimal solution between expensive safe design that utilizes continuous street lighting system at night for the entire road, or inexpensive design that sacrifices the safety, relying on using vehicles lighting, to eliminate the problem of high cost energy consumption during the night operation of the road. By taking into account both of these factors, smart lighting automation system is proposed using Pattern Recognition Technique applied on vehicle number-plates. In this proposal, the road is sectionalized into zones, and based on smart Pattern Recognition Technique, the control system of the road lighting illuminates only the zone that the vehicles pass through. Economic analysis is provided in this paper to support the value of using this design of lighting control system.展开更多
The aim of this paper is to present the concept of a simple and cheap upgrade for electric water boilers, allowing them to provide power quality services to the distribution grid. The upgrade requires only minimum add...The aim of this paper is to present the concept of a simple and cheap upgrade for electric water boilers, allowing them to provide power quality services to the distribution grid. The upgrade requires only minimum additional hardware and it is easily installable. “Smart Boilers”, as the upgraded boilers are named, perform precise active and reactive power control, but most significantly mitigate line current harmonics. Αctive and reactive power control is implemented by appropriate regulation of the modulation sinewave amplitude and phase, respectively. This type of control is easily customizable in order to accommodate a variety of power quality targets, depending on the required level of services and available grid monitoring equipment. The method used for line current harmonic compensation is based on the injection of mirror harmonics created at the modulation stage of the converter. It is indifferent of harmonic source: it is equally successful at mitigating harmonics caused by the power electronic converter of the Smart Boiler, other sources of current harmonics or loads. The achieved grid services are clearly beyond the “on/off” operation of electric boilers, currently implemented by Demand Side Management (DSM) in order to shift load away from peak hours. It has been demonstrated through simulations, that Smart Boilers can assist voltage regulation at terminal buses, compensate reactive power and suppress harmonic currents at lines.展开更多
The risks and challenges faced by human society at the moment are global warming, climate change and pollution. In addition to their effect on the atmosphere, the quantity of fossil fuels is beginning to decrease, and...The risks and challenges faced by human society at the moment are global warming, climate change and pollution. In addition to their effect on the atmosphere, the quantity of fossil fuels is beginning to decrease, and countries have taken steps to encourage greater use of renewable energy resources. This article explores the feasibility of supplying electricity from a hybrid power system (HPS) comprising wind/photovoltaic (PV) and batteries. Taking into account residential buildings that consume the largest portion of energy in Saudi grid<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Saudi Arabia, Riyadh is the preferred city with distinctive geographical and climatic conditions. The hourly electricity demand data must be over 8760 hours during a 1-year analysis in order to assess the optimum design and operational planning of the HPS. The economic analysis is carried out by applying HOMER software on the basis of net present cost (NPC), energy cost (COE) and the renewable fraction for all situations. In addition, to specify the effect of fuel costs on the scheme, sensitivity tests are carried out by considering two separate tariff rates for residential consumers. The results of the economic analysis show that current tariff is not economic to </span><span style="font-family:Verdana;">use HSP under warm and temperate climate conditions compare to using</span><span style="font-family:Verdana;"> electricity from grid and the expected forecasted tariff shows it’s economic to use HSP compare to grid electricity.</span></span></span></span>展开更多
The power grid is a fusion of technologies in energy systems, and how to adjust and control the output power of each generator to balance the load of the grid is a crucial issue. As a platform, the smart grid is for t...The power grid is a fusion of technologies in energy systems, and how to adjust and control the output power of each generator to balance the load of the grid is a crucial issue. As a platform, the smart grid is for the convenience of the implementation of adaptive control generators using advanced technologies. In this paper, we are introducing a new approach, the Central Lower Configuration Table, which optimizes dispatch of the generating capacity in a smart grid power system. The dispatch strategy of each generator in the grid is presented in the configuration table, and the scenario consists of two-level agents. A central agent optimizes dispatch calculation to get the configuration table, and a lower agent controls generators according to the tasks of the central level and the work states during generation. The central level is major optimization and adjustment. We used machine learning to predict the power load and address the best optimize cost function to deal with a different control strategy. We designed the items of the cost function, such as operations, maintenances and the effects on the environment. Then, according to the total cost, we got a new second-rank-sort table. As a result, we can resolve generator’s task based on the table, which can also be updated on-line based on the environmental situation. The signs of the driving generator’s controller include active power and system’s f. The lower control level agent carries out the generator control to track f along with the best optimized cost function. Our approach makes optimized dispatch algorithm more convenient to realize, and the numerical simulation indicates the strategy of machine learning forecast of optimized power dispatch is effective.展开更多
<strong>Background:</strong> Glaucoma is a serious public health problem since it causes visual impairment impacting social, mental and physical health of an individual. Diagnosis and management of glaucom...<strong>Background:</strong> Glaucoma is a serious public health problem since it causes visual impairment impacting social, mental and physical health of an individual. Diagnosis and management of glaucoma continue to be a challenge due to few qualified personnel and high cost of the equipment. The use of portable Eye Examination Kit such as Smartphone and tablets can be used in glaucoma screening for taking high-resolution fundus photos for optic disc and visual field parameters, respectively. This study was conducted to evaluate the applicability of mobile electronic device to detect optic disc and visual field parameters for glaucoma in a resource limited setting. <strong>Objective:</strong> To evaluate the applicability of mobile electronic devices to detect optic disc and visual field parameters for glaucoma. <strong>Methodology:</strong> Across-sectional study was conducted at KCMC Eye department from October 2018 to June 2019. Study included 140 participants attending eye clinic of which 67 had glaucoma and 73 without glaucoma. Clinical and socio-demographic data were collected using a structured questionnaire and analysed using Stata 15. Glaucoma examination was made on the right eye and photo comparison made between those with and without glaucoma. PEEK Smartphone fundus photo examination was compared with the gold standard machine (Slit Lamp Biomicroscopy), Amsler grid chart installed on a tablet (Microsoft surface, internal storage 256 GB, 2013) and contrast sensitivity compared with Humphrey field analyser (i series, model 740117434, Carl Zeiss Meditec). <strong>Results:</strong> The kappa (k) agreement between Slit lump biomicroscopy fundus view image and PEEK Smartphone concerning the optic disc measurement was 0.92 with sensitivity and specificity of 90.32% (95% CI: 80.12 - 96.37) and 93.59% (95% CI: 85.67 - 97.89) with a p < 0.001 respectively. An agreement between Amsler grid and Humphrey Field Analyser was 0.67 with sensitivity of 33.33% (95% CI: 20.76 - 47.92) and specificity of 86.52% (95% CI展开更多
This paper proposes a power control method to improve a stability of a small-scale power grid with renewable energy sources. In an isolated small- scale power grid such as an island, diesel power plant is main power s...This paper proposes a power control method to improve a stability of a small-scale power grid with renewable energy sources. In an isolated small- scale power grid such as an island, diesel power plant is main power source which has an environmental burden and expensive running cost due to high priced fossil fuel. Thus, expanding installation of the renewable energy sources such as a wind power is strongly desirable. Such fluctuating energy sources, however, harm power quality of the small-scale power grid, and in addition, conventional power plant in the small-scale power grid cannot, in general, stabilize the grid system with such fluctuating power sources. In this study, Variable Speed Doubly-Fed Induction Generator (VS-DFIG) is proposed to be in-stalled at a diesel power plant instead of a conventional Fixed Speed Synchronous Generator (FS-SG), because quick control of a power balance in the small-scale power grid can be achieved by using the inertial energy of VS-DFIG. In addition, utilization of a Battery Energy Storage System (BESS) is also considered to assist cooperatively the VS-DFIG control. As a result of the simulation analysis by using the proposed method, it is verified that frequency fluctuations due to renewable energy source can be effectively reduced by quick power control of the VS-DFIG compared to the conventional FS-SG, and further control ability can be obtained by utilizing BESS. Moreover, the transient stability of a small-scale power grid during a grid fault can also be enhanced.展开更多
The future of electricity systems will compose of small-scale generation and distribution where end-users will be active participants with localized energy management systems that are able to interact on a free energy...The future of electricity systems will compose of small-scale generation and distribution where end-users will be active participants with localized energy management systems that are able to interact on a free energy market. Software agents will most likely control power assets and interact together to decide the best and safest configuration of the power grid system. This paper presents a design of agents that can be deployed in real-time with capabilities that include optimization of resources, intensive computation, and appropriate decision-making. Jordan 51-bus system has been used for simulation with a total generation capacity of 4050 MW of which 230 MW represent</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> renewable energy. The economic analyses demonstrated the use of smart grid technologies with 2016 generation</span><span style="font-family:""><span style="font-family:Verdana;">—</span><span style="font-family:Verdana;">load profiles for nominal liquified gas (NLG) prices and </span><span style="font-family:Verdana;">±</span><span style="font-family:Verdana;">20% sensitivity analysis. The results have shown variations in the range of 1% in the price of MWh with smart grid technologies. These variations are mainly driven by the fact that agents shift power generation to renewable power plants to produce maximum power at peak hours. As a result, there is a positive economic impact in both NLG </span><span style="font-family:Verdana;">±</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">20% sensitivity analysis, due to the fact that agents coordinate to better displace expensive thermal generation with renewable generation. It is evident that renewable resources compensate for power at peak times and provide economic benefits and savings.展开更多
针对大数据聚类低效的问题,提出一种方形邻域快速网格密度聚类算法(square-neighborhood and gridbased DBSCAN,SGBSCAN)。首先给出方形邻域密度聚类定义,利用方形邻域代替圆形邻域,降低时间复杂度;其次提出方形邻域密度聚类的grid概念...针对大数据聚类低效的问题,提出一种方形邻域快速网格密度聚类算法(square-neighborhood and gridbased DBSCAN,SGBSCAN)。首先给出方形邻域密度聚类定义,利用方形邻域代替圆形邻域,降低时间复杂度;其次提出方形邻域密度聚类的grid概念,快速确定高密度区域内核心点与数据点之间的密度关系;最后提出grid密度簇,利用网格之间的关系加快密度簇的形成。算法应用于16个数据集,分别与已有文献算法进行对比,结果表明所提算法在聚类效率方面有显著提升,数据量越大算法效率提升越明显,且该算法适用于多维数据的聚类。展开更多
文摘准确统计地块现状负荷对配电网规划和负荷管理意义重大,供电部门现有各数据系统无统计地块负荷功能,传统统计方法依赖于人工,不适合大规模统计,为此提出一种基于地理信息系统(geographic information system,GIS)技术的统计方法。该方法首先根据城市总体规划和控制性详细规划建立地块GIS信息数据库;然后利用二次开发MapInfo功能,确定配用变压器与地块的耦合关系,模拟各配用变压器日负荷曲线,叠加统计各地块现状负荷。最后以某市配电网为例对全市地块现状负荷进行计算,结果表明该方法能够实现大规模地块现状负荷统计,提高统计效率和统计结果可靠性。
基金Project supported by the National Natural Science Foundation of China(Nos.61722303,61673104,and 61973133)the Six Talent Peaks Project of Jiangsu Province,China(No.2019-DZXX-006)the Australian Research Council(No.DP200101199)。
文摘Designing an efficient distributed economic dispatch(DED)strategy for the smart grid(SG)in the presence of multiple generators plays a paramount role in obtaining various benefits of a new generation power syst em,such as easy implementation,low maintenance cos t,high energy efficiency,and strong robus tn ess agains t uncertainties.It has drawn a lot of interest from a wide variety of scientific disciplines,including power engineering,control theory,and applied mathematics.We present a state-of-the-art review of some theoretical advances toward DED in the SG,with a focus on the literature published since 2015.We systematically review the recent results on this topic and subsequently categorize them into distributed discrete-and continuous-time economic dispatches of the SG in the presence of multiple generators.After reviewing the literature,we briefly present some future research directions in DED for the SG,including the distributed security economic dispatch of the SG,distributed fast economic dispatch in the SG with practical constraints,efficient initialization-free DED in the SG,DED in the SG in the presence of smart energy storage batteries and flexible loads,and DED in the SG with artificial intelligence technologies.
文摘For century, the need of change in the system of power grid is being felt and being considered as the most important change that we need in the modern era electrical system but before moving towards a new change the things in past should be kept in mind so that there are better chances of great and beneficial change. The purpose of this research is to investigate the changes need to be incorporated in a conventional system to make a system self-sufficient and automated in order to make Electrical Power system more reliable. This paper assesses the current one way power system that is needed to be changed and has tried to provide an overview of the changes that we need in the system. The paper has focused more on the smart grid system and has explained the importance of smart grid system in terms of efficiency, automation and decision making capability in case of faults occurred on primitive grids with the help of comparative studies. The paper also highlighted the results in form of comparison with conventional grids and threw some light on the vision, control and the application of the smart grid system that will provide a two way system to the electrical network of the country and will make the distribution and consumption of energy more efficient also which is going to increase the reliability and accuracy in the system.
文摘Due to the increasing share of renewable energy, new requirements are placed on control room software. Such software is often exclusive to the supplier, but other suppliers could offer new and better methods. For security reasons, external applications often have no direct data access to control room software. Such software can provide information about the power grid via a periodic file transfer in CIM (Common Information Model) format. These files are often very large, containing complete records, delivering information not always relevant to the external applications. Extracting the relevant information required by external applications can be time-consuming, thus presenting a problem for time-critical applications. This paper presents a method allowing different applications to efficiently access the relevant data from the massive data stream contained in the CIM files. This method has been tested with a distribution system operator and clearly increases performance, allowing different applications to access the relevant data.
基金supported by Theoretical study of power system synergistic dispatch National Science Foundation of China(51477091).
文摘Given the increasing uncertainties in power supply and load,this paper proposes the concept of power source and grid coordination uniformity planning.In this approach,the standard deviation of the transmission line load rate is considered as the uniformity evaluation index for power source and grid planning.A multi-stage and multi-objective optimization model of the power source and grid expansion planning is established to minimize the comprehensive cost of the entire planning cycle.In this study,the improved particle swarm optimization algorithm and genetic algorithm are combined to solve the model,thus improving the efficiency and accuracy of the solution.The analysis of a simple IEEE Garver’s 6-node system shows that the model and solution method are effective and feasible.Moreover,they are suitable for the coordinated planning of the power source and grid under a diversified nature of power supply and load.
文摘The paper covers analysis and investigation of lighting automation system in low-traffic long-roads. The main objective is to provide optimal solution between expensive safe design that utilizes continuous street lighting system at night for the entire road, or inexpensive design that sacrifices the safety, relying on using vehicles lighting, to eliminate the problem of high cost energy consumption during the night operation of the road. By taking into account both of these factors, smart lighting automation system is proposed using Pattern Recognition Technique applied on vehicle number-plates. In this proposal, the road is sectionalized into zones, and based on smart Pattern Recognition Technique, the control system of the road lighting illuminates only the zone that the vehicles pass through. Economic analysis is provided in this paper to support the value of using this design of lighting control system.
文摘The aim of this paper is to present the concept of a simple and cheap upgrade for electric water boilers, allowing them to provide power quality services to the distribution grid. The upgrade requires only minimum additional hardware and it is easily installable. “Smart Boilers”, as the upgraded boilers are named, perform precise active and reactive power control, but most significantly mitigate line current harmonics. Αctive and reactive power control is implemented by appropriate regulation of the modulation sinewave amplitude and phase, respectively. This type of control is easily customizable in order to accommodate a variety of power quality targets, depending on the required level of services and available grid monitoring equipment. The method used for line current harmonic compensation is based on the injection of mirror harmonics created at the modulation stage of the converter. It is indifferent of harmonic source: it is equally successful at mitigating harmonics caused by the power electronic converter of the Smart Boiler, other sources of current harmonics or loads. The achieved grid services are clearly beyond the “on/off” operation of electric boilers, currently implemented by Demand Side Management (DSM) in order to shift load away from peak hours. It has been demonstrated through simulations, that Smart Boilers can assist voltage regulation at terminal buses, compensate reactive power and suppress harmonic currents at lines.
文摘The risks and challenges faced by human society at the moment are global warming, climate change and pollution. In addition to their effect on the atmosphere, the quantity of fossil fuels is beginning to decrease, and countries have taken steps to encourage greater use of renewable energy resources. This article explores the feasibility of supplying electricity from a hybrid power system (HPS) comprising wind/photovoltaic (PV) and batteries. Taking into account residential buildings that consume the largest portion of energy in Saudi grid<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Saudi Arabia, Riyadh is the preferred city with distinctive geographical and climatic conditions. The hourly electricity demand data must be over 8760 hours during a 1-year analysis in order to assess the optimum design and operational planning of the HPS. The economic analysis is carried out by applying HOMER software on the basis of net present cost (NPC), energy cost (COE) and the renewable fraction for all situations. In addition, to specify the effect of fuel costs on the scheme, sensitivity tests are carried out by considering two separate tariff rates for residential consumers. The results of the economic analysis show that current tariff is not economic to </span><span style="font-family:Verdana;">use HSP under warm and temperate climate conditions compare to using</span><span style="font-family:Verdana;"> electricity from grid and the expected forecasted tariff shows it’s economic to use HSP compare to grid electricity.</span></span></span></span>
文摘The power grid is a fusion of technologies in energy systems, and how to adjust and control the output power of each generator to balance the load of the grid is a crucial issue. As a platform, the smart grid is for the convenience of the implementation of adaptive control generators using advanced technologies. In this paper, we are introducing a new approach, the Central Lower Configuration Table, which optimizes dispatch of the generating capacity in a smart grid power system. The dispatch strategy of each generator in the grid is presented in the configuration table, and the scenario consists of two-level agents. A central agent optimizes dispatch calculation to get the configuration table, and a lower agent controls generators according to the tasks of the central level and the work states during generation. The central level is major optimization and adjustment. We used machine learning to predict the power load and address the best optimize cost function to deal with a different control strategy. We designed the items of the cost function, such as operations, maintenances and the effects on the environment. Then, according to the total cost, we got a new second-rank-sort table. As a result, we can resolve generator’s task based on the table, which can also be updated on-line based on the environmental situation. The signs of the driving generator’s controller include active power and system’s f. The lower control level agent carries out the generator control to track f along with the best optimized cost function. Our approach makes optimized dispatch algorithm more convenient to realize, and the numerical simulation indicates the strategy of machine learning forecast of optimized power dispatch is effective.
文摘<strong>Background:</strong> Glaucoma is a serious public health problem since it causes visual impairment impacting social, mental and physical health of an individual. Diagnosis and management of glaucoma continue to be a challenge due to few qualified personnel and high cost of the equipment. The use of portable Eye Examination Kit such as Smartphone and tablets can be used in glaucoma screening for taking high-resolution fundus photos for optic disc and visual field parameters, respectively. This study was conducted to evaluate the applicability of mobile electronic device to detect optic disc and visual field parameters for glaucoma in a resource limited setting. <strong>Objective:</strong> To evaluate the applicability of mobile electronic devices to detect optic disc and visual field parameters for glaucoma. <strong>Methodology:</strong> Across-sectional study was conducted at KCMC Eye department from October 2018 to June 2019. Study included 140 participants attending eye clinic of which 67 had glaucoma and 73 without glaucoma. Clinical and socio-demographic data were collected using a structured questionnaire and analysed using Stata 15. Glaucoma examination was made on the right eye and photo comparison made between those with and without glaucoma. PEEK Smartphone fundus photo examination was compared with the gold standard machine (Slit Lamp Biomicroscopy), Amsler grid chart installed on a tablet (Microsoft surface, internal storage 256 GB, 2013) and contrast sensitivity compared with Humphrey field analyser (i series, model 740117434, Carl Zeiss Meditec). <strong>Results:</strong> The kappa (k) agreement between Slit lump biomicroscopy fundus view image and PEEK Smartphone concerning the optic disc measurement was 0.92 with sensitivity and specificity of 90.32% (95% CI: 80.12 - 96.37) and 93.59% (95% CI: 85.67 - 97.89) with a p < 0.001 respectively. An agreement between Amsler grid and Humphrey Field Analyser was 0.67 with sensitivity of 33.33% (95% CI: 20.76 - 47.92) and specificity of 86.52% (95% CI
文摘This paper proposes a power control method to improve a stability of a small-scale power grid with renewable energy sources. In an isolated small- scale power grid such as an island, diesel power plant is main power source which has an environmental burden and expensive running cost due to high priced fossil fuel. Thus, expanding installation of the renewable energy sources such as a wind power is strongly desirable. Such fluctuating energy sources, however, harm power quality of the small-scale power grid, and in addition, conventional power plant in the small-scale power grid cannot, in general, stabilize the grid system with such fluctuating power sources. In this study, Variable Speed Doubly-Fed Induction Generator (VS-DFIG) is proposed to be in-stalled at a diesel power plant instead of a conventional Fixed Speed Synchronous Generator (FS-SG), because quick control of a power balance in the small-scale power grid can be achieved by using the inertial energy of VS-DFIG. In addition, utilization of a Battery Energy Storage System (BESS) is also considered to assist cooperatively the VS-DFIG control. As a result of the simulation analysis by using the proposed method, it is verified that frequency fluctuations due to renewable energy source can be effectively reduced by quick power control of the VS-DFIG compared to the conventional FS-SG, and further control ability can be obtained by utilizing BESS. Moreover, the transient stability of a small-scale power grid during a grid fault can also be enhanced.
文摘The future of electricity systems will compose of small-scale generation and distribution where end-users will be active participants with localized energy management systems that are able to interact on a free energy market. Software agents will most likely control power assets and interact together to decide the best and safest configuration of the power grid system. This paper presents a design of agents that can be deployed in real-time with capabilities that include optimization of resources, intensive computation, and appropriate decision-making. Jordan 51-bus system has been used for simulation with a total generation capacity of 4050 MW of which 230 MW represent</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> renewable energy. The economic analyses demonstrated the use of smart grid technologies with 2016 generation</span><span style="font-family:""><span style="font-family:Verdana;">—</span><span style="font-family:Verdana;">load profiles for nominal liquified gas (NLG) prices and </span><span style="font-family:Verdana;">±</span><span style="font-family:Verdana;">20% sensitivity analysis. The results have shown variations in the range of 1% in the price of MWh with smart grid technologies. These variations are mainly driven by the fact that agents shift power generation to renewable power plants to produce maximum power at peak hours. As a result, there is a positive economic impact in both NLG </span><span style="font-family:Verdana;">±</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">20% sensitivity analysis, due to the fact that agents coordinate to better displace expensive thermal generation with renewable generation. It is evident that renewable resources compensate for power at peak times and provide economic benefits and savings.
文摘针对大数据聚类低效的问题,提出一种方形邻域快速网格密度聚类算法(square-neighborhood and gridbased DBSCAN,SGBSCAN)。首先给出方形邻域密度聚类定义,利用方形邻域代替圆形邻域,降低时间复杂度;其次提出方形邻域密度聚类的grid概念,快速确定高密度区域内核心点与数据点之间的密度关系;最后提出grid密度簇,利用网格之间的关系加快密度簇的形成。算法应用于16个数据集,分别与已有文献算法进行对比,结果表明所提算法在聚类效率方面有显著提升,数据量越大算法效率提升越明显,且该算法适用于多维数据的聚类。