Extreme events such as tropical storm,tornado,hurricane cause significant disruptions to infrastructure systems including power,water,transportation,telecommunication services.Faster restoration from power outages is ...Extreme events such as tropical storm,tornado,hurricane cause significant disruptions to infrastructure systems including power,water,transportation,telecommunication services.Faster restoration from power outages is critical since power outages substantially impact various sectors including education,financial transactions,healthcare,and leisure.Thus,it is important to study outage restoration patterns.To develop data-driven models and test its performance on unseen hurricanes,high-resolution data from multiple hurricanes are required.However,such high-resolution power outage data from utility companies are proprietary and not easily acces-sible to all.Thus,the aim of this study is to demonstrate the use of macroscopic location data available from Facebook for analyzing power outage during hurricanes.First,it shows the association between population activity in Facebook and hurricane-induced power outage using the data for Hurricane Ida at a ZIP Code level.Second,it develops a data-driven model to predict power outage restoration pattern at a ZIP Code level utilizing Facebook data for Hurricanes Ida and Ian.We found that Facebook data can explain 59%of variance in by power outages at daily level and it can explain 65%of variance in restoration times from power outages at a ZIP code level.The data-driven model can reliably predict the restoration pattern from power outages(R^(2)=0.816).This study can aid researchers to choose alternative data for power outage analysis and help emergency managers and utility companies gain data-driven insights enhancing their decision-making for an impending hurricane.展开更多
This work attempts to investigate some practical measures that may reduce severe power outages that lead to energy curtailments. The first step of this attempt is to explore, from the consumer’s perspective, the adve...This work attempts to investigate some practical measures that may reduce severe power outages that lead to energy curtailments. The first step of this attempt is to explore, from the consumer’s perspective, the adverse effects of the energy curtailments that reflect enormous damages (tangible and intangible) to the residential sector in the city of Riyadh (the capital of the Kingdom of Saudi Arabia). The second step is to propose, analyze, and employ energy conservation strategies that lead to both energy conservation and costs savings. The study results show that some customers will suffer enormous tangible and intangible losses should these outages occur during specific times, seasons, and for prolonged durations. In order to reduce these power outages and hence mitigate their adverse effects and consequences, the study proposes proper practical measures and solutions without compromising the consumers’ needs, satisfaction, and convenience.展开更多
The article provides outcomes of efforts taken by the specialists of radiation safety departments of Ukrainian Nuclear Power Plants （NPPs） to optimize and decrease exposure doses of personnel performing works during...The article provides outcomes of efforts taken by the specialists of radiation safety departments of Ukrainian Nuclear Power Plants （NPPs） to optimize and decrease exposure doses of personnel performing works during outages at NPP units. The article is written based on many years＇ experience and analysis of radiation hazardous works performed during scheduled maintenance of NPP equipment. It highlights significance of planning radiation doses （dose quotas） and organization of pending works during outages based on lessons learned. The results of works allowed to give due consideration to training of NPP maintenance personnel, improvement of labour conditions, workplace setup and enhancement of radiation protection means.展开更多
Since adopting reform and opening policy. the electric power industry in China developed rapidly. At present there are more than 200 units of 200 MW and above large generation units. Due to hasty development, problems...Since adopting reform and opening policy. the electric power industry in China developed rapidly. At present there are more than 200 units of 200 MW and above large generation units. Due to hasty development, problems are numerous, especially for the boilers. In the 1986-1990 period (Seventh Five-year Plan period), large capacity boiler outages accounted for 65.8% of all large units equipment outages, and "four tube"展开更多
This paper describes the significant cost saving opportunities for consumers in developing countries by the use of computational intelligence and demand-side-management techniques to mitigate the massive use of diesel...This paper describes the significant cost saving opportunities for consumers in developing countries by the use of computational intelligence and demand-side-management techniques to mitigate the massive use of diesel back-up during grid outages. Application of load scheduling optimization is investigated during scheduled power outages, for residential consumer in India. The specific load shifting approaches explored include a day ahead predicted load schedule which is generated by performing a DSM referring to the forecasted day ahead outage. Whereas in reality the predicted may not match the actual outage, thus in these cases a fuzzy logic rule base is referred on real time basis to take corrective action & reach the best optimal load schedule possible to attain the lowest cost. The load types modeled include passive loads and schedulable, i.e. typically heavy loads. It is found that this multi-level DSM schemes show excellent benefits to the consumer. The maximum diesel savings for the consumer due to load shifting can be approximately ranging from 45% to as high as 75% for a flat-tariff grid. The study also showed that the actual savings potential depends on the timing of power outage, duration and the specific load characteristics.展开更多
A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded ac...A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded accuracy for less than four visible GPS satellites with poor signal quality. Positions and velocities of the satellites were predicted by a GMDH neural network, and the pseudo ranges and pseudo range rates received by the GPS receiver were simulated to ensure the regular op eration of the GPS/SINS Kalman filter during outages. In the mathematical simulation a tightly cou pled navigation system with a proposed approach has better navigation accuracy during GPS outages, and the anti jamming ability is strengthened for the tightly coupled navigation system.展开更多
This paper aims at putting forward viewpoints regarding the use of stability technology to prevent and control cascading outages by examining recent blackout events.Based on the inquiry reports of the 2011 SouthwestAm...This paper aims at putting forward viewpoints regarding the use of stability technology to prevent and control cascading outages by examining recent blackout events.Based on the inquiry reports of the 2011 SouthwestAmerica blackout and the 2012 India power blackouts,event evolution features are first summarized from a stability perspective.Then a comparative analysis is conducted so as to propose suggestions of effective measures,either preventive or emergency,which could have avoided the blackouts.It is shown that applications of several mature technologies can create opportunities of preventing or interrupting the cascading development.These include offline dynamic simulation,online stability analysis and preventive control,real-time situational awareness and automatic emergency control.Further R&D directions are given to address the challenges of modern power systems as well.They cover system fault identification criterion of protection and control devices,verification of adaptability of control effect to system operating conditions,real-time operational management of emergency control measures and improvement of simulation accuracy.展开更多
The paper considers the quantity and causes of outages in electric grids of low and medium voltages using the example of an electric grid of a regional power supply company.The main types of damage to the equipment of...The paper considers the quantity and causes of outages in electric grids of low and medium voltages using the example of an electric grid of a regional power supply company.The main types of damage to the equipment of power lines and transformer substations were identified.Data on other areas of rural and urban electric grids are also analyzed.The main directions for reducing the quantity of outages in electric grids are proposed based on this analysis.Among them,there are the use of isolated wires in power transmission lines,the improvement of design of switching devices,switches and terminals of transformers,the application of technical condition diagnostics,the disaggregating of power lines and the increase of protection sensitivity of power lines.Most of the causes of equipment damage can be prevented by increasing the maintenance level of this equipment.展开更多
A terrestrial relay-aided reconfigurable intelligent surface(RIS)system with decode,re-encode and forward(DRF)relaying scheme is presented where the RIS effectively contributes to both sourceto-destination and relay-t...A terrestrial relay-aided reconfigurable intelligent surface(RIS)system with decode,re-encode and forward(DRF)relaying scheme is presented where the RIS effectively contributes to both sourceto-destination and relay-to-destination signaling.While in the conventional decode and forward(DF)relaying scheme,the source signal is merely duplicated in the relay and the time intervals are equally allocated to the source and relay nodes,this paper considers DRF relaying scheme where versatile time-sharing is adopted for the source and relay nodes which can be optimized based on the relative coordinates of the involved nodes.Two protocols namely unidirectional connection(UC)and bidirectional connection(BC)are proposed based on the source awareness from the relay’s successful reception.The outage probability(OP)performance for both protocols and both DF and DRF relaying schemes is analyzed and tight approximations are obtained.The numerical results show the out-performance of the DRF over the DF relaying scheme in the both UC and BC protocols.Equipped with the obtained system OP,the system throughput is defined and the optimum system throughput is obtained by optimizing the system rate and the timesharing between the source and the relay.Analytical results are corroborated in the numerical examples.展开更多
Addressed to the N-k_(1)-k_(2) cascading outages,it is computationally burdensome for the reliable calculation of active and reactive power flows.This paper builds a comprehensive framework with three algorithms,inclu...Addressed to the N-k_(1)-k_(2) cascading outages,it is computationally burdensome for the reliable calculation of active and reactive power flows.This paper builds a comprehensive framework with three algorithms,including the distribution factor(DF),the Newton-Raphson(NR),and the first iteration of NR algorithm(termed as 1J).Classifiers are designed to determine whether the NR algorithm should be employed for accuracy.Classifier features are extracted upon the analytical error of 1J.As reactive power is partially considered in the 1J but neglected in the DF algorithm,the deviation between the solutions is taken as one crucial feature.The support vector machine(SVM)is then utilized for classifier training.As the deep integration of the causal inference and the statistical paradigm,this framework calculates active and reactive power flows rapidly,reliably,and robustly.The effectiveness and robustness are fully validated in three typical IEEE systems.展开更多
Prolonged power outages debilitate the economy and threaten public health. Existing research is generally limitedin its scope to a single event, an outage cause, or a region. Here, we provide one of the most comprehen...Prolonged power outages debilitate the economy and threaten public health. Existing research is generally limitedin its scope to a single event, an outage cause, or a region. Here, we provide one of the most comprehensiveanalyses of large-scale power outages in the U.S. from 2002 to 2019. This analysis is based on the outage datacollected under U.S. federal mandates that concern large blackouts, typically of transmission systems and excludemuch more common but smaller blackouts, typically, of distribution systems. We categorized the data into fouroutage causes and computed reliability metrics, which are commonly used for distribution-level small outagesonly but useful for analyzing large blackouts. Our spatiotemporal analysis reveals six of the most resilient U.S.states since 2010, improvement of power resilience against natural hazards in the south and northeast regions,and a disproportionately large number of human attacks for its population in the Western Electricity CoordinatingCouncil region. Our regression analysis identifies several statistically significant predictors and hypotheses forU.S. resilience to large blackouts. Furthermore, we propose a novel framework for analyzing outage data usingdifferential weighting and influential points to better understand power resilience. We share curated data andcode as Supplementary Materials.展开更多
Major disasters such as wildfire, tornado, hurricane, tropical storm, and flooding cause disruptions in infrastructure systems such as power and water supply, wastewater management, telecommunication, and transportati...Major disasters such as wildfire, tornado, hurricane, tropical storm, and flooding cause disruptions in infrastructure systems such as power and water supply, wastewater management, telecommunication, and transportation facilities. Disruptions in electricity infrastructure have negative impacts on sectors throughout a region, including education, medical services,financial services, and recreation. In this study, we introduced a novel approach to investigate the factors that can be associated with longer restoration time of power service after a hurricane. Considering restoration time as the dependent variable and using a comprehensive set of county-level data, we estimated a generalized accelerated failure time(GAFT) model that accounts for spatial dependence among observations for time to event data. The model fit improved by 12% after considering the effects of spatial correlation in time to event data. Using the GAFT model and Hurricane Irma's impact on Florida as a case study, we examined:(1) differences in electric power outages and restoration rates among different types of power companies—investor-owned power companies, rural and municipal cooperatives;(2) the relationship between the duration of power outage and power system variables;and(3) the relationship between the duration of power outage and socioeconomic attributes. The findings of this study indicate that counties with a higher percentage of customers served by investor-owned electric companies and lower median household income faced power outage for a longer time. This study identified the key factors to predict restoration time of hurricane-induced power outages, allowing disaster management agencies to adopt strategies required for restoration process.展开更多
Social media,including Twitter,has become an important source for disaster response.Yet most studies focus on a very limited amount of geotagged data(approximately 1%of all tweets)while discarding a rich body of data ...Social media,including Twitter,has become an important source for disaster response.Yet most studies focus on a very limited amount of geotagged data(approximately 1%of all tweets)while discarding a rich body of data that contains location expressions in text.Location information is crucial to understanding the impact of disasters,including where damage has occurred and where the people who need help are situated.In this paper,we propose a novel two-stage machine learningand deep learning-based framework for power outage detection from Twitter.First,we apply a probabilistic classification model using bag-ofngrams features to find true power outage tweets.Second,we implement a new deep learning method-bidirectional long short-term memory networks-to extract outage locations from text.Results show a promising classification accuracy(86%)in identifying true power outage tweets,and approximately 20 times more usable tweets can be located compared with simply relying on geotagged tweets.The method of identifying location names used in this paper does not require language-or domain-specific external resources such as gazetteers or handcrafted features,so it can be extended to other situational awareness analyzes and new applications.展开更多
The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacki...The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacking sufficient exploration of scenarios where communication nodes are in motion.This paper presents a multi-destination vehicle communication system based on decode-and-forward(DF)UAV relays,where source and destination vehicles are moving and an internal eavesdropper intercepts messages from UAV.The closed-form expressions for system outage probability and secrecy outage probability are derived to analyze the reliability and security of the system.Furthermore,the impact of the UAV's position,signal transmission power,and system time allocation ratio on the system's performance are also analyzed.The numerical simulation results validate the accuracy of the derived formulas and confirm the correctness of the analysis.The appropriate time allocation ratio significantly enhances the security performance of system under various environmental conditions.展开更多
Recognized as a pivotal facet in Beyond Fifth-Generation(B5G)and the upcoming Sixth-Generation(6G)wireless networks,Unmanned Aerial Vehicle(UAV)communications pose challenges due to limited capabilities when serving a...Recognized as a pivotal facet in Beyond Fifth-Generation(B5G)and the upcoming Sixth-Generation(6G)wireless networks,Unmanned Aerial Vehicle(UAV)communications pose challenges due to limited capabilities when serving as mobile base stations,leading to suboptimal service for edge users.To address this,the collaborative formation of Coordinated Multi-Point(CoMP)networks proves instrumental in alleviating the issue of the poor Quality of Service(QoS)at edge users in the network periphery.This paper introduces a groundbreaking solution,the Hybrid Uplink-Downlink Non-Orthogonal Multiple Access(HUD-NOMA)scheme for UAV-aided CoMP networks.Leveraging network coding and NOMA technology,our proposed HUD-NOMA effectively enhances transmission rates for edge users,notwithstanding a minor reduction in signal reception reliability for strong signals.Importantly,the system’s overall sum rate is elevated.The proposed HUD-NOMA demonstrates resilience against eavesdroppers by effectively managing intended interferences without the need for additional artificial noise injection.The study employs a stochastic geometry approach to derive the Secrecy Outage Probability(SOP)for the transmissions in the CoMP network,revealing superior performance in transmission rates and lower SOP compared to existing methods through numerical verification.Furthermore,guided by the theoretical SOP derivation,this paper proposes a power allocation strategy to further reduce the system’s SOP.展开更多
The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the p...The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the primary user(PU)activity,it can re-sult in interference that limits the system performance.Additionally,since the wireless medium is broadcast in nature,there is a risk of eavesdroppers intercepting the cognitive users’data.Therefore,it is crucial to consider secrecy in the system analysis.In this paper,we analyze the secrecy outage probability(SOP)at the secondary receiver and derive the secret diversity gain for an interweave cognitive multiple-input multiple-output(MIMO)fading channel in the presence of an eavesdropper.Our study takes into account the ef-fects of the fading channel,the PU interference,and the eavesdropper on both spectrum sensing and data transmission phases.We demonstrate that utilizing all the antennas for sensing eliminates the limiting effects of missed detection probability and PU interference on the secret diversity gain.As a result,the cognitive user can achieve the same level of secret diversity gain as a conventional non-cognitive system(CNCS).Our an-alytical results are further validated through simula-tions.展开更多
Recently,wireless security has been highlighted as one of the most important techniques for 6G mobile communication systems.Many researchers have tried to improve the Physical-Layer Security(PLS)performance such as Se...Recently,wireless security has been highlighted as one of the most important techniques for 6G mobile communication systems.Many researchers have tried to improve the Physical-Layer Security(PLS)performance such as Secrecy Outage Probability(SOP)and Secrecy Energy-Efficiency(SEE).The SOP indicates the outage probability that the data transmission between legitimate devices does not guarantee a certain reliability level,and the SEE is defined as the ratio between the achievable secrecy-rate and the consumed transmit power.In this paper,we consider a Multi-User Multi-Input Single-Output(MU-MISO)downlink cellular network where a legitimate Base Station(BS)equipped with multiple transmit antennas sends secure information to multiple legitimate Mobile Stations(MSs),and multiple potential eavesdroppers(EVEs)equipped with a single receive antenna try to eavesdrop on this information.Each potential EVE tries to intercept the secure information,i.e.,the private message,from the legitimate BS to legitimate MSs with a certain eavesdropping probability.To securely receive the private information,each legitimate MS feeds back its effective channel gain to the legitimate BS only when the effective channel gain is higher than a certain threshold,i.e.,the legitimate MSs adopt an Opportunistic Feedback(OF)strategy.In such eavesdropping channels,both SOP and SEE are analyzed as performance measures of PLS and their closed-form expressions are derived mathematically.Based on the analytical results,it is shown that the SOP of the OF strategy approaches that of a Full Feedback(FF)strategy as the number of legitimate MSs or the number of antennas at the BS increases.Furthermore,the trade-off between SOP and SEE as a function of the channel feedback threshold in the OF strategy is investigated.The analytical results and related observations are verified by numerical simulations.展开更多
Aerial access networks are considered by one of the promising solutions for 6G technology with Unmanned Aerial Vehicles(UAVs)acting as aerial relays to fill coverage gaps,enhance line-of-sight communication,and improv...Aerial access networks are considered by one of the promising solutions for 6G technology with Unmanned Aerial Vehicles(UAVs)acting as aerial relays to fill coverage gaps,enhance line-of-sight communication,and improve network performance and user experience.To improve spectrum utilization,this paper studies a UAV-assisted wireless communication network based on Cognitive Radio(CR)and Non-Orthogonal Multiple Access(NOMA)technologies.Considering the presence of potential malicious eavesdroppers in complex practical communication scenarios,multiple transmitting nodes cooperate through UAVs.To enhance physical layer security performance,an efficient low-complexity transmitter-relay selection scheme is proposed,which selects the optimal transmitting node based on link channel quality,referred to as the Suboptimal Node Transmission Strategy(SNTS).To further enhance system security performance,another scheme is proposed,which selects the optimal transmitting node by maximizing the transmission capacity of the far user,known as the Optimal Node Transmission Strategy(ONTS).Under the decode-and-forward relay strategy,the security performance of the network under both schemes is studied.Under the joint constraints imposed by the primary interference power and secondary maximum transmission power,the secrecy outage probability for users is derived and validated through simulations.The results indicate that under identical conditions,as the number of transmitting nodes increases,the probability of establishing a line-of-sight link in ground-air communications rises,leading to a decrease in the system’s secrecy outage probability.Furthermore,in terms of multi-user diversity gain,ONTS significantly outperforms SNTS.However,the computational overhead of ONTS is relatively high.Therefore,when meeting the actual communication needs of users,a trade-off between complexity and performance must be considered.展开更多
In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source ...In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.展开更多
基金U.S.National Science Foundation for the grant CMMI-1832578 to support the research presented in this paper.
文摘Extreme events such as tropical storm,tornado,hurricane cause significant disruptions to infrastructure systems including power,water,transportation,telecommunication services.Faster restoration from power outages is critical since power outages substantially impact various sectors including education,financial transactions,healthcare,and leisure.Thus,it is important to study outage restoration patterns.To develop data-driven models and test its performance on unseen hurricanes,high-resolution data from multiple hurricanes are required.However,such high-resolution power outage data from utility companies are proprietary and not easily acces-sible to all.Thus,the aim of this study is to demonstrate the use of macroscopic location data available from Facebook for analyzing power outage during hurricanes.First,it shows the association between population activity in Facebook and hurricane-induced power outage using the data for Hurricane Ida at a ZIP Code level.Second,it develops a data-driven model to predict power outage restoration pattern at a ZIP Code level utilizing Facebook data for Hurricanes Ida and Ian.We found that Facebook data can explain 59%of variance in by power outages at daily level and it can explain 65%of variance in restoration times from power outages at a ZIP code level.The data-driven model can reliably predict the restoration pattern from power outages(R^(2)=0.816).This study can aid researchers to choose alternative data for power outage analysis and help emergency managers and utility companies gain data-driven insights enhancing their decision-making for an impending hurricane.
文摘This work attempts to investigate some practical measures that may reduce severe power outages that lead to energy curtailments. The first step of this attempt is to explore, from the consumer’s perspective, the adverse effects of the energy curtailments that reflect enormous damages (tangible and intangible) to the residential sector in the city of Riyadh (the capital of the Kingdom of Saudi Arabia). The second step is to propose, analyze, and employ energy conservation strategies that lead to both energy conservation and costs savings. The study results show that some customers will suffer enormous tangible and intangible losses should these outages occur during specific times, seasons, and for prolonged durations. In order to reduce these power outages and hence mitigate their adverse effects and consequences, the study proposes proper practical measures and solutions without compromising the consumers’ needs, satisfaction, and convenience.
文摘The article provides outcomes of efforts taken by the specialists of radiation safety departments of Ukrainian Nuclear Power Plants （NPPs） to optimize and decrease exposure doses of personnel performing works during outages at NPP units. The article is written based on many years＇ experience and analysis of radiation hazardous works performed during scheduled maintenance of NPP equipment. It highlights significance of planning radiation doses （dose quotas） and organization of pending works during outages based on lessons learned. The results of works allowed to give due consideration to training of NPP maintenance personnel, improvement of labour conditions, workplace setup and enhancement of radiation protection means.
文摘Since adopting reform and opening policy. the electric power industry in China developed rapidly. At present there are more than 200 units of 200 MW and above large generation units. Due to hasty development, problems are numerous, especially for the boilers. In the 1986-1990 period (Seventh Five-year Plan period), large capacity boiler outages accounted for 65.8% of all large units equipment outages, and "four tube"
文摘This paper describes the significant cost saving opportunities for consumers in developing countries by the use of computational intelligence and demand-side-management techniques to mitigate the massive use of diesel back-up during grid outages. Application of load scheduling optimization is investigated during scheduled power outages, for residential consumer in India. The specific load shifting approaches explored include a day ahead predicted load schedule which is generated by performing a DSM referring to the forecasted day ahead outage. Whereas in reality the predicted may not match the actual outage, thus in these cases a fuzzy logic rule base is referred on real time basis to take corrective action & reach the best optimal load schedule possible to attain the lowest cost. The load types modeled include passive loads and schedulable, i.e. typically heavy loads. It is found that this multi-level DSM schemes show excellent benefits to the consumer. The maximum diesel savings for the consumer due to load shifting can be approximately ranging from 45% to as high as 75% for a flat-tariff grid. The study also showed that the actual savings potential depends on the timing of power outage, duration and the specific load characteristics.
文摘A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded accuracy for less than four visible GPS satellites with poor signal quality. Positions and velocities of the satellites were predicted by a GMDH neural network, and the pseudo ranges and pseudo range rates received by the GPS receiver were simulated to ensure the regular op eration of the GPS/SINS Kalman filter during outages. In the mathematical simulation a tightly cou pled navigation system with a proposed approach has better navigation accuracy during GPS outages, and the anti jamming ability is strengthened for the tightly coupled navigation system.
基金This work is supported by State Grid Corporation of China(No.SGCC-MPLG003-2012).
文摘This paper aims at putting forward viewpoints regarding the use of stability technology to prevent and control cascading outages by examining recent blackout events.Based on the inquiry reports of the 2011 SouthwestAmerica blackout and the 2012 India power blackouts,event evolution features are first summarized from a stability perspective.Then a comparative analysis is conducted so as to propose suggestions of effective measures,either preventive or emergency,which could have avoided the blackouts.It is shown that applications of several mature technologies can create opportunities of preventing or interrupting the cascading development.These include offline dynamic simulation,online stability analysis and preventive control,real-time situational awareness and automatic emergency control.Further R&D directions are given to address the challenges of modern power systems as well.They cover system fault identification criterion of protection and control devices,verification of adaptability of control effect to system operating conditions,real-time operational management of emergency control measures and improvement of simulation accuracy.
文摘The paper considers the quantity and causes of outages in electric grids of low and medium voltages using the example of an electric grid of a regional power supply company.The main types of damage to the equipment of power lines and transformer substations were identified.Data on other areas of rural and urban electric grids are also analyzed.The main directions for reducing the quantity of outages in electric grids are proposed based on this analysis.Among them,there are the use of isolated wires in power transmission lines,the improvement of design of switching devices,switches and terminals of transformers,the application of technical condition diagnostics,the disaggregating of power lines and the increase of protection sensitivity of power lines.Most of the causes of equipment damage can be prevented by increasing the maintenance level of this equipment.
文摘A terrestrial relay-aided reconfigurable intelligent surface(RIS)system with decode,re-encode and forward(DRF)relaying scheme is presented where the RIS effectively contributes to both sourceto-destination and relay-to-destination signaling.While in the conventional decode and forward(DF)relaying scheme,the source signal is merely duplicated in the relay and the time intervals are equally allocated to the source and relay nodes,this paper considers DRF relaying scheme where versatile time-sharing is adopted for the source and relay nodes which can be optimized based on the relative coordinates of the involved nodes.Two protocols namely unidirectional connection(UC)and bidirectional connection(BC)are proposed based on the source awareness from the relay’s successful reception.The outage probability(OP)performance for both protocols and both DF and DRF relaying schemes is analyzed and tight approximations are obtained.The numerical results show the out-performance of the DRF over the DF relaying scheme in the both UC and BC protocols.Equipped with the obtained system OP,the system throughput is defined and the optimum system throughput is obtained by optimizing the system rate and the timesharing between the source and the relay.Analytical results are corroborated in the numerical examples.
基金This work was supported by the China State Grid Corporation Project of the Key Technologies of Power Grid Proactive Support for Energy Transition(No.5100-202040325A-0-0-00).
文摘Addressed to the N-k_(1)-k_(2) cascading outages,it is computationally burdensome for the reliable calculation of active and reactive power flows.This paper builds a comprehensive framework with three algorithms,including the distribution factor(DF),the Newton-Raphson(NR),and the first iteration of NR algorithm(termed as 1J).Classifiers are designed to determine whether the NR algorithm should be employed for accuracy.Classifier features are extracted upon the analytical error of 1J.As reactive power is partially considered in the 1J but neglected in the DF algorithm,the deviation between the solutions is taken as one crucial feature.The support vector machine(SVM)is then utilized for classifier training.As the deep integration of the causal inference and the statistical paradigm,this framework calculates active and reactive power flows rapidly,reliably,and robustly.The effectiveness and robustness are fully validated in three typical IEEE systems.
基金the National Science Foundation(NSF grant CMMI-1824681)。
文摘Prolonged power outages debilitate the economy and threaten public health. Existing research is generally limitedin its scope to a single event, an outage cause, or a region. Here, we provide one of the most comprehensiveanalyses of large-scale power outages in the U.S. from 2002 to 2019. This analysis is based on the outage datacollected under U.S. federal mandates that concern large blackouts, typically of transmission systems and excludemuch more common but smaller blackouts, typically, of distribution systems. We categorized the data into fouroutage causes and computed reliability metrics, which are commonly used for distribution-level small outagesonly but useful for analyzing large blackouts. Our spatiotemporal analysis reveals six of the most resilient U.S.states since 2010, improvement of power resilience against natural hazards in the south and northeast regions,and a disproportionately large number of human attacks for its population in the Western Electricity CoordinatingCouncil region. Our regression analysis identifies several statistically significant predictors and hypotheses forU.S. resilience to large blackouts. Furthermore, we propose a novel framework for analyzing outage data usingdifferential weighting and influential points to better understand power resilience. We share curated data andcode as Supplementary Materials.
基金the U.S.National Science Foundation for the Grant CMMI-1832578 to support the research presented in this article。
文摘Major disasters such as wildfire, tornado, hurricane, tropical storm, and flooding cause disruptions in infrastructure systems such as power and water supply, wastewater management, telecommunication, and transportation facilities. Disruptions in electricity infrastructure have negative impacts on sectors throughout a region, including education, medical services,financial services, and recreation. In this study, we introduced a novel approach to investigate the factors that can be associated with longer restoration time of power service after a hurricane. Considering restoration time as the dependent variable and using a comprehensive set of county-level data, we estimated a generalized accelerated failure time(GAFT) model that accounts for spatial dependence among observations for time to event data. The model fit improved by 12% after considering the effects of spatial correlation in time to event data. Using the GAFT model and Hurricane Irma's impact on Florida as a case study, we examined:(1) differences in electric power outages and restoration rates among different types of power companies—investor-owned power companies, rural and municipal cooperatives;(2) the relationship between the duration of power outage and power system variables;and(3) the relationship between the duration of power outage and socioeconomic attributes. The findings of this study indicate that counties with a higher percentage of customers served by investor-owned electric companies and lower median household income faced power outage for a longer time. This study identified the key factors to predict restoration time of hurricane-induced power outages, allowing disaster management agencies to adopt strategies required for restoration process.
基金the financial support received from Oak Ridge National Laboratory(ORNL)’s Liane Russell Distinguished Early Career Fellowship and grant no.TG0100000.
文摘Social media,including Twitter,has become an important source for disaster response.Yet most studies focus on a very limited amount of geotagged data(approximately 1%of all tweets)while discarding a rich body of data that contains location expressions in text.Location information is crucial to understanding the impact of disasters,including where damage has occurred and where the people who need help are situated.In this paper,we propose a novel two-stage machine learningand deep learning-based framework for power outage detection from Twitter.First,we apply a probabilistic classification model using bag-ofngrams features to find true power outage tweets.Second,we implement a new deep learning method-bidirectional long short-term memory networks-to extract outage locations from text.Results show a promising classification accuracy(86%)in identifying true power outage tweets,and approximately 20 times more usable tweets can be located compared with simply relying on geotagged tweets.The method of identifying location names used in this paper does not require language-or domain-specific external resources such as gazetteers or handcrafted features,so it can be extended to other situational awareness analyzes and new applications.
基金supported by the National Natural Science Foundation of China under Grants 62001359 and 61901201by the Key Science and Technology Research Project of Henan Province under Grants 232102211059the Natural Science Basic Research Program of Shaanxi under Grants 2022JQ-658 and 2022JQ-621。
文摘The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacking sufficient exploration of scenarios where communication nodes are in motion.This paper presents a multi-destination vehicle communication system based on decode-and-forward(DF)UAV relays,where source and destination vehicles are moving and an internal eavesdropper intercepts messages from UAV.The closed-form expressions for system outage probability and secrecy outage probability are derived to analyze the reliability and security of the system.Furthermore,the impact of the UAV's position,signal transmission power,and system time allocation ratio on the system's performance are also analyzed.The numerical simulation results validate the accuracy of the derived formulas and confirm the correctness of the analysis.The appropriate time allocation ratio significantly enhances the security performance of system under various environmental conditions.
基金supported in part by the National Key R&D Program of China under Grant 2022YFB3104503in part by the National Natural Science Foundation of China under Grant 62202054,and Grant 61931001+2 种基金in part by the National Natural Science Foundation of China No.62202054the Young Elite Scientists Sponsorship Program of the China Association for Science and Technology under Grant 2023QNRC001in part by the U.S.National Science Foundation under Grant 2136202.
文摘Recognized as a pivotal facet in Beyond Fifth-Generation(B5G)and the upcoming Sixth-Generation(6G)wireless networks,Unmanned Aerial Vehicle(UAV)communications pose challenges due to limited capabilities when serving as mobile base stations,leading to suboptimal service for edge users.To address this,the collaborative formation of Coordinated Multi-Point(CoMP)networks proves instrumental in alleviating the issue of the poor Quality of Service(QoS)at edge users in the network periphery.This paper introduces a groundbreaking solution,the Hybrid Uplink-Downlink Non-Orthogonal Multiple Access(HUD-NOMA)scheme for UAV-aided CoMP networks.Leveraging network coding and NOMA technology,our proposed HUD-NOMA effectively enhances transmission rates for edge users,notwithstanding a minor reduction in signal reception reliability for strong signals.Importantly,the system’s overall sum rate is elevated.The proposed HUD-NOMA demonstrates resilience against eavesdroppers by effectively managing intended interferences without the need for additional artificial noise injection.The study employs a stochastic geometry approach to derive the Secrecy Outage Probability(SOP)for the transmissions in the CoMP network,revealing superior performance in transmission rates and lower SOP compared to existing methods through numerical verification.Furthermore,guided by the theoretical SOP derivation,this paper proposes a power allocation strategy to further reduce the system’s SOP.
文摘The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the primary user(PU)activity,it can re-sult in interference that limits the system performance.Additionally,since the wireless medium is broadcast in nature,there is a risk of eavesdroppers intercepting the cognitive users’data.Therefore,it is crucial to consider secrecy in the system analysis.In this paper,we analyze the secrecy outage probability(SOP)at the secondary receiver and derive the secret diversity gain for an interweave cognitive multiple-input multiple-output(MIMO)fading channel in the presence of an eavesdropper.Our study takes into account the ef-fects of the fading channel,the PU interference,and the eavesdropper on both spectrum sensing and data transmission phases.We demonstrate that utilizing all the antennas for sensing eliminates the limiting effects of missed detection probability and PU interference on the secret diversity gain.As a result,the cognitive user can achieve the same level of secret diversity gain as a conventional non-cognitive system(CNCS).Our an-alytical results are further validated through simula-tions.
基金supported in part by the National Research Foundation of Korea(NRF)funded by the Korea government(MSIT)under Grant NRF-2022R1I1A3073740in part by the Institute for Information and Communications Technology Promotion(IITP)Grant funded by the Korea Government(MSIP,Development of Cube Satellites Based on Core Technologies in Low Earth Orbit Satellite Communications)under Grant RS-2024-00396992in part by Institute of Information&communications Technology Planning&Evaluation(IITP)grant funded by the Korea government(MSIT)(2022-0-00704,Development of 3D-NET Core Technology for High-Mobility Vehicular Service)。
文摘Recently,wireless security has been highlighted as one of the most important techniques for 6G mobile communication systems.Many researchers have tried to improve the Physical-Layer Security(PLS)performance such as Secrecy Outage Probability(SOP)and Secrecy Energy-Efficiency(SEE).The SOP indicates the outage probability that the data transmission between legitimate devices does not guarantee a certain reliability level,and the SEE is defined as the ratio between the achievable secrecy-rate and the consumed transmit power.In this paper,we consider a Multi-User Multi-Input Single-Output(MU-MISO)downlink cellular network where a legitimate Base Station(BS)equipped with multiple transmit antennas sends secure information to multiple legitimate Mobile Stations(MSs),and multiple potential eavesdroppers(EVEs)equipped with a single receive antenna try to eavesdrop on this information.Each potential EVE tries to intercept the secure information,i.e.,the private message,from the legitimate BS to legitimate MSs with a certain eavesdropping probability.To securely receive the private information,each legitimate MS feeds back its effective channel gain to the legitimate BS only when the effective channel gain is higher than a certain threshold,i.e.,the legitimate MSs adopt an Opportunistic Feedback(OF)strategy.In such eavesdropping channels,both SOP and SEE are analyzed as performance measures of PLS and their closed-form expressions are derived mathematically.Based on the analytical results,it is shown that the SOP of the OF strategy approaches that of a Full Feedback(FF)strategy as the number of legitimate MSs or the number of antennas at the BS increases.Furthermore,the trade-off between SOP and SEE as a function of the channel feedback threshold in the OF strategy is investigated.The analytical results and related observations are verified by numerical simulations.
基金supported by the National Natural Science Foundation of China(Nos.62461032 and 62001359)the Tianyou Youth Talent Lift Program of Lanzhou Jiaotong University,Chinathe Key Research and Development Project of Lanzhou Jiaotong University,China(No.ZDYF2304).
文摘Aerial access networks are considered by one of the promising solutions for 6G technology with Unmanned Aerial Vehicles(UAVs)acting as aerial relays to fill coverage gaps,enhance line-of-sight communication,and improve network performance and user experience.To improve spectrum utilization,this paper studies a UAV-assisted wireless communication network based on Cognitive Radio(CR)and Non-Orthogonal Multiple Access(NOMA)technologies.Considering the presence of potential malicious eavesdroppers in complex practical communication scenarios,multiple transmitting nodes cooperate through UAVs.To enhance physical layer security performance,an efficient low-complexity transmitter-relay selection scheme is proposed,which selects the optimal transmitting node based on link channel quality,referred to as the Suboptimal Node Transmission Strategy(SNTS).To further enhance system security performance,another scheme is proposed,which selects the optimal transmitting node by maximizing the transmission capacity of the far user,known as the Optimal Node Transmission Strategy(ONTS).Under the decode-and-forward relay strategy,the security performance of the network under both schemes is studied.Under the joint constraints imposed by the primary interference power and secondary maximum transmission power,the secrecy outage probability for users is derived and validated through simulations.The results indicate that under identical conditions,as the number of transmitting nodes increases,the probability of establishing a line-of-sight link in ground-air communications rises,leading to a decrease in the system’s secrecy outage probability.Furthermore,in terms of multi-user diversity gain,ONTS significantly outperforms SNTS.However,the computational overhead of ONTS is relatively high.Therefore,when meeting the actual communication needs of users,a trade-off between complexity and performance must be considered.
基金supported in part by the National Research Foundation of Korea(NRF)funded by the Korea government(MSIT)under Grant NRF-2022R1I1A3073740in part by the MSIT(Ministry of Science and ICT),Korea,under the ITRC(Information Technology Research Center)support program(IITP-2024-RS-2024-00436406)supervised by the IITP(Institute for Information&Communications Technology Planning&Evaluation)+1 种基金in part by the Institute for Information and Communications Technology Promotion(IITP)Grant funded by the Korea Government(MSIP,Development of Cube Satellites Based on Core Technologies in Low Earth Orbit Satellite Communications)under Grant RS-2024-00396992in part by the Korea Research Institute for Defense Technology planning and advancement(KRIT)grant,funded by the Korea government(DAPA(Defense Acquisition Program Administration))(21-106-A00-007,Space-Layer Intelligent Communication Network Laboratory,2022).
文摘In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.
