We present a new approach based on honey-bee mating optimization to estimate the state variables in distribution networks including distributed generators. The proposed method considers practical models of electrical ...We present a new approach based on honey-bee mating optimization to estimate the state variables in distribution networks including distributed generators. The proposed method considers practical models of electrical equipments such as static var compensators, voltage regulators, and under-load tap changer transformers, which have usually nonlinear and discrete characteristics. The feasibility of the proposed approach is demonstrated by comparison with the methods based on neural networks, ant colony optimization, and genetic algorithms for two test systems, a network with 34-bus radial test feeders and a realistic 80-bus 20 kV network.展开更多
This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA(Genetic Optimization algorithm).It is proved that GA method is fast and e...This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA(Genetic Optimization algorithm).It is proved that GA method is fast and easy tool to enable the planners to select accurate and the optimum size of generators to improve the system voltage profile in addition to reduce the active and reactive power loss.GA fitness function is introduced including the active power losses,reactive power losses and the cumulative voltage deviation variables with selecting weight of each variable.GA fitness function is subjected to voltage constraints,active and reactive power losses constraints and DG size constraint.展开更多
In this paper,a fault location method for the petal-shaped distribution network(PSDN)with inverter-interfaced distributed generators(IIDGs)is proposed to shorten the time of manual inspection.In order to calculate the...In this paper,a fault location method for the petal-shaped distribution network(PSDN)with inverter-interfaced distributed generators(IIDGs)is proposed to shorten the time of manual inspection.In order to calculate the fault position,the closed-loop structure of the PSDN is skillfully exploited,and the common control strategies of IIDGs are considered.For asymmetrical faults,a fault line identification formula based on the negative-sequence current phase differences is presented,and a fault location formula only utilizing the negative-sequence current amplitudes is derived to calculated the fault position.For symmetrical faults,the positive-sequence current at both ends of lines and the current output from IIDGs are used to identify the fault line,and the positive-sequence current on multiple lines are used to pinpoint the fault position.In this method,corresponding current phasors are separated into amplitudes and phases to satisfy the limitation of communication level.The simulation results show that the error is generally less than 1%,and the accuracy of the proposed method is not affected by the fault type,fault position,fault resistance,load current,and the IIDG penetration.展开更多
In this paper, the authors analyze the influence that connection of many distributed generators （DGs） has on the harmonics of the distribution network from the viewpoints of harmonic current, harmonic voltage, and v...In this paper, the authors analyze the influence that connection of many distributed generators （DGs） has on the harmonics of the distribution network from the viewpoints of harmonic current, harmonic voltage, and voltage total harmonic distortion （THD）, when it is assumed that the harmonic voltages or the harmonic currents in a distribution network increases by connection of many DGs through the inverters. The analysis on the influence of DGs is carried out by using a standard analytical model of distribution network with DGs based on the practical data. The authors evaluate quantitatively the influence which harmonics generated from DGs has on the harmonics of the distribution network, and analyze visually about propagation of harmonics within the distribution network. In addition, the authors also verify about the restraint effect of the harmonics in the network scale by the active filters installation.展开更多
This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. T...This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as a power system network diagram creation function and a voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.展开更多
The petal-shaped distribution network has high power supply reliability.However,the closed-loop operation mode and the access of inverter-interfaced distributed generators(IIDGs)bring great challenges to the protectio...The petal-shaped distribution network has high power supply reliability.However,the closed-loop operation mode and the access of inverter-interfaced distributed generators(IIDGs)bring great challenges to the protection schemes.The current amplitude differential protection is an effective means to solve this problem,but the existing criterions rarely consider both sensitivity to high-resistance faults and low requirements for data synchronization.Therefore,the general variation laws of the amplitude difference between the current steady-state components at both terminals and the phase differences between current fault components at both terminals are revealed.For external faults,the steady-state-component current amplitude difference is around zero and the fault-component current phase difference is around 180◦.For internal faults,either the amplitude difference is large or the phase difference is small.Accordingly,a current differential protection scheme based on the pre-fault and postfault steady-state current is proposed.The amplitude and phase of current at both terminals of the protected line are required in the proposed scheme,which has low requirements for data synchronization.The simulation results show that the proposed protection scheme is not affected by the fault type,position,resistance and capacity of the IIDGs.It can also be applied to radial distribution networks with IIDGs.展开更多
There are various types of distributed generators (DGs) with different grid integration strategies. The transient characteristics of the fault currents provided by the DGs are different to those of conventional synchr...There are various types of distributed generators (DGs) with different grid integration strategies. The transient characteristics of the fault currents provided by the DGs are different to those of conventional synchronous generators. In this paper, a distribution network with multi-type DGs is investigated, including consideration of DG low-voltage ride through (LVRT). The fault current characteristics of two typical DGs, i.e. an inverter-interfaced distributed generator (IIDG) and a doubly-fed induction generator (DFIG), are analyzed, considering the specific operation modes. Based on analysis of the fault characteristics, an equivalent model of the multi-type DGs under symmetrical/asymmetrical fault conditions is established. A fast-iterative fault calculation method for enhancing the calculation efficiency while avoiding local convergence is then proposed using an improved particle swarm optimization (PSO) algorithm. A simulation system of the distribution network with multi-type DGs is established in PSCAD/EMTDC. The simulation results validate the high accuracy and calculation efficiency of the proposed calculation method of the fault components. This can assist in the settings of the protection threshold.展开更多
The composite channel models of the generalized distributed antenna system （GDAS） such as Rayleigh-lognormal fading are studied. Then comparisons are performed between the GDAS and the traditional multiple-input mul...The composite channel models of the generalized distributed antenna system （GDAS） such as Rayleigh-lognormal fading are studied. Then comparisons are performed between the GDAS and the traditional multiple-input multiple-output （MIMO） system to analyze the ergodic capacity of the GDAS and make conclusions that it is impossible to achieve an analytical expression for the ergodic capacity of the GDAS. Moreover, in order to evaluate the performance of the ergodic capacity of the GDAS conveniently, the analytical lower bound and upper bound of the ergodic capacity of the GDAS are derived by using the results from multivariate statistics and matrix inequalities, under the scenarios of Rayleigh-lognormal fading and equal power allocation scheme at transmitter. Finally, the analytical bounds are verified by comparisons with the numerical results.展开更多
The rapid growth of distributed generator(DG)capacities has introduced additional controllable assets to improve the performance of distribution systems in terms of service restoration.Renewable DGs are of particular ...The rapid growth of distributed generator(DG)capacities has introduced additional controllable assets to improve the performance of distribution systems in terms of service restoration.Renewable DGs are of particular interest to utility companies,but the stochastic nature of intermittent renewable DGs could have a negative impact on the electric grid if they are not properly handled.In this study,we investigate distribution system service restoration using DGs as the primary power source,and we develop an effective approach to handle the uncertainty of renewable DGs under extreme conditions.The distribution system service restoration problem can be described as a mixed-integer second-order cone programming model by modifying the radial topology constraints and power flow equations.The uncertainty of renewable DGs will be modeled using a chance-constrained approach.Furthermore,the forecast errors and noises in real-time operation are solved using a novel model-free control algorithm that can automatically track the trajectory of real-time DG output.The proposed service restoration strategy and model-free control algorithm are validated using an IEEE 123-bus test system.展开更多
Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expr...Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expression of the solutions are given by the generalized inverse one of bounded linear operator. This is theoretically important for studying the stabilization and asymptotic stability of the second order generalized distributed parameter system.展开更多
To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When a...To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When an extreme event occurs,the controllable generators form temporary microgrids(MGs)to restore the load maximally.Simultaneously,a demand response program(DRP)mitigates the imbalance between the power supply and demand during extreme events.To cope with the fault uncertainty,a robust optimization(RO)method is applied to reduce the long-term investment and short-term operation costs.The optimization is formulated as a tri-level defenderattacker-defender(DAD)framework.At the first level,decision-makers work out the DG allocation scheme;at the second level,the attacker finds the optimal attack strategy with maximum damage;and at the third level,restoration measures,namely distribution network reconfiguration(DNR)and demand response are performed.The problem is solved by the nested column and constraint generation(NC&CG)method and the model is validated using an IEEE 33-node system.Case studies validate the effectiveness and superiority of the proposed model according to the enhanced resilience and reduced cost.展开更多
Owing to the wide range of applications in various fields,generative models have become increasingly popular.However,they do not handle spatio-temporal features well.Inspired by the recent advances in these models,thi...Owing to the wide range of applications in various fields,generative models have become increasingly popular.However,they do not handle spatio-temporal features well.Inspired by the recent advances in these models,this paper designs a distributed spatio-temporal generative adversarial network(STGAN-D)that,given some initial data and random noise,generates a consecutive sequence of spatio-temporal samples which have a logical relationship.This paper builds a spatio-temporal discriminator to distinguish whether the samples generated by the generator meet the requirements for time and space coherence,and builds a controller for distributed training of the network gradient updated to separate the model training and parameter updating,to improve the network training rate.The model is trained on the skeletal dataset and the traffic dataset.In contrast to traditional generative adversarial networks(GANs),the proposed STGAN-D can generate logically coherent samples with the corresponding spatial and temporal features while avoiding mode collapse.In addition,this paper shows that the proposed model can generate different styles of spatio-temporal samples given different random noise inputs,and the controller can improve the network training rate.This model will extend the potential range of applications of GANs to areas such as traffic information simulation and multiagent adversarial simulation.展开更多
Control design is important for PEMFC （proton exchange membrane fuel cell） distributed power generator to satisfy user requirement for safe and stable operation. For a complex multi-variable dynamic system, a dynami...Control design is important for PEMFC （proton exchange membrane fuel cell） distributed power generator to satisfy user requirement for safe and stable operation. For a complex multi-variable dynamic system, a dynamic simulation model is first established. In view of close coupling and non-linear relationships between variables, the intelligent auto-adapted PI decoupling control method is used. From the simulation results it is found that, by bringing quadratic performance index in the single neuron, constructing adaptive PI controller, and adjusting gas flow rates through the second pressure relief valve and air compressor coordinately, both anode and cathode pressures can be maintained at ideal levels.展开更多
In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code (STC), Joint Transmission (JT) and Multiple Input Multiple Output (MIMO), and to meet the requirement...In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code (STC), Joint Transmission (JT) and Multiple Input Multiple Output (MIMO), and to meet the requirements of high-bit-rate multimedia services, new network topologies should be studied. Generalized distributed multicell architecture can take full advantage of multi-antenna technologies and solve the problem of frequent handover caused by higher carrier frequencies. Group handover, the handover policy based on the architecture, can eliminate the cell edge effect. Furthermore, by applying the concept of group handover to 3G mobile communication systems, the Fast Cell Group Selection (FCGS) scheme can effectively improve the data rate for cell edge users.展开更多
Long-term regional extreme cold events(ECEs)garner significant attention due to their widespread impact and prolonged duration,posing critical threats to human society and ecosystems.Previous studies have examined ECE...Long-term regional extreme cold events(ECEs)garner significant attention due to their widespread impact and prolonged duration,posing critical threats to human society and ecosystems.Previous studies have examined ECE characteristics at single sites or grid points,however,it is crucial to recognize that such events generally manifest as spatiotemporally continuous regional phenomena.Here,we proposed an objective methodology based on spatiotemporal continuity to identify ECEs in the China-Pakistan Economic Corridor(CPEC)during the winters of 1961-2015.This approach successfully reproduced the dynamic evolution of ECEs,encompassing their initiation,development,and dissipation.We further analyzed the changes of ECE intensity,frequency,and duration,and assessed ECE trends within varying return periods by employing the generalized Pareto distribution(GPD).Our findings reveal a decline in the frequency and duration of ECEs in CPEC over the study period,while their intensity has increased by 50%.ECEs predominantly occur in the northern regions of Azad Kashmir and Balochistan’s Quetta in Pakistan,and Kashgar in China.High recurrence levels are associated with an expansion of ECE-prone areas,particularly in the northern Pamir Plateau,which emerges as a regional hotspot.These results highlight the critical need to remain vigilant to potential future surges in ECEs under global warming,underscoring their implications for regional climate resilience.展开更多
A new extended distribution called the Odd Exponential Generalized Exponential-Exponential distribution(EOEGE-E)is proposed based on generalization of the odd generalized exponential family(OEGE-E).The statistical pro...A new extended distribution called the Odd Exponential Generalized Exponential-Exponential distribution(EOEGE-E)is proposed based on generalization of the odd generalized exponential family(OEGE-E).The statistical properties of the proposed distribution are derived.The study evaluates the accuracy of six estimation methods under complete samples.Estimation techniques include maximumlikelihood,ordinary least squares,weighted least squares,maximumproduct of spacing,Cramer vonMises,and Anderson-Darling methods.Twomethods of estimation for the involved parameters are considered based on progressively type Ⅱ censored data(PTⅡC).These methods are maximum likelihood and maximum product of spacing.The proposed distribution’s effectiveness was evaluated using different data sets from various fields.The proposed distribution provides a better fit for these datasets than existing probability distributions.展开更多
Frequent extreme heat events exacerbated by global warming pose a significant threat to human health.However,the dynamic changes in human thermal comfort during such regional extremes remain understudied.This study in...Frequent extreme heat events exacerbated by global warming pose a significant threat to human health.However,the dynamic changes in human thermal comfort during such regional extremes remain understudied.This study investigates the spatiotemporal characteristics of the Universal Thermal Climate Index(UTCI)during 5-year return period extreme heat events across the Beijing-Tianjin-Hebei(BTH)region of China,utilizing 40 years of meteorological data from 174 stations.A non-stationary Generalized Extreme Value distribution model with a location parameter link function was identified as the optimal model(for 65.3%of stations)through the Akaike Information Criterion,capturing 16 regional extreme heat events.Results indicate that extreme heat thresholds rise with increasing return periods,with the highest thresholds concentrated around Beijing and Shijiazhuang.Air temperature and mean radiant temperature were found to be the dominant factors influencing UTCI,with daytime air temperature contributing 47.03%to 50.64%and nighttime mean radiant temperature contributing up to 48.55%.Spatially,“extreme heat stress”conditions,as defined by UTCI,were predominantly observed in the southeastern plains of Beijing and southern Hebei Province.Diurnally,UTCI peaked between 1200 and 1600 BT(Beijing time),generally returning to“no heat stress”levels across most areas between 0000 and 0600 BT.These findings provide crucial insights into the dynamics of human thermal comfort during extreme heat events in the BTH region,offering valuable scientific support for developing targeted heat mitigation and adaptation strategies.展开更多
To utilize residual redundancy to reduce the error induced by fading channels and decrease the complexity of the field model to describe the probability structure for residual redundancy, a simplified statistical mode...To utilize residual redundancy to reduce the error induced by fading channels and decrease the complexity of the field model to describe the probability structure for residual redundancy, a simplified statistical model for residual redundancy and a low complexity joint source-channel decoding（JSCD） algorithm are proposed. The complicated residual redundancy in wavelet compressed images is decomposed into several independent 1-D probability check equations composed of Markov chains and it is regarded as a natural channel code with a structure similar to the low density parity check （LDPC） code. A parallel sum-product （SP） and iterative JSCD algorithm is proposed. Simulation results show that the proposed JSCD algorithm can make full use of residual redundancy in different directions to correct errors and improve the peak signal noise ratio （PSNR） of the reconstructed image and reduce the complexity and delay of JSCD. The performance of JSCD is more robust than the traditional separated encoding system with arithmetic coding in the same data rate.展开更多
Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this...Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.展开更多
In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected ...In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected induction motors will also be used. In the circumstances, a smart power conversion unit is one of key components, which can integrate these DC or AC apparatus and trade power among them. Authors have developed an integrated power converter based on a well-known circuit topology of flying capacitor multilevel converter. This paper describes the detail of the circuit topology and its characteristics depending on designed parameters. The achieved power quality is also verified by simulation study.展开更多
文摘We present a new approach based on honey-bee mating optimization to estimate the state variables in distribution networks including distributed generators. The proposed method considers practical models of electrical equipments such as static var compensators, voltage regulators, and under-load tap changer transformers, which have usually nonlinear and discrete characteristics. The feasibility of the proposed approach is demonstrated by comparison with the methods based on neural networks, ant colony optimization, and genetic algorithms for two test systems, a network with 34-bus radial test feeders and a realistic 80-bus 20 kV network.
文摘This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA(Genetic Optimization algorithm).It is proved that GA method is fast and easy tool to enable the planners to select accurate and the optimum size of generators to improve the system voltage profile in addition to reduce the active and reactive power loss.GA fitness function is introduced including the active power losses,reactive power losses and the cumulative voltage deviation variables with selecting weight of each variable.GA fitness function is subjected to voltage constraints,active and reactive power losses constraints and DG size constraint.
基金supported by State Grid Science and Technology Project:Research on Key Protection Technologies for New-type Urban Distribution Network with Controllable Sources and Loads(5100-201913019A-0-0-00).
文摘In this paper,a fault location method for the petal-shaped distribution network(PSDN)with inverter-interfaced distributed generators(IIDGs)is proposed to shorten the time of manual inspection.In order to calculate the fault position,the closed-loop structure of the PSDN is skillfully exploited,and the common control strategies of IIDGs are considered.For asymmetrical faults,a fault line identification formula based on the negative-sequence current phase differences is presented,and a fault location formula only utilizing the negative-sequence current amplitudes is derived to calculated the fault position.For symmetrical faults,the positive-sequence current at both ends of lines and the current output from IIDGs are used to identify the fault line,and the positive-sequence current on multiple lines are used to pinpoint the fault position.In this method,corresponding current phasors are separated into amplitudes and phases to satisfy the limitation of communication level.The simulation results show that the error is generally less than 1%,and the accuracy of the proposed method is not affected by the fault type,fault position,fault resistance,load current,and the IIDG penetration.
文摘In this paper, the authors analyze the influence that connection of many distributed generators （DGs） has on the harmonics of the distribution network from the viewpoints of harmonic current, harmonic voltage, and voltage total harmonic distortion （THD）, when it is assumed that the harmonic voltages or the harmonic currents in a distribution network increases by connection of many DGs through the inverters. The analysis on the influence of DGs is carried out by using a standard analytical model of distribution network with DGs based on the practical data. The authors evaluate quantitatively the influence which harmonics generated from DGs has on the harmonics of the distribution network, and analyze visually about propagation of harmonics within the distribution network. In addition, the authors also verify about the restraint effect of the harmonics in the network scale by the active filters installation.
文摘This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as a power system network diagram creation function and a voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.
基金supported in part by Science and Technology Project of State Grid Corporation of China:Research on Key Protection Technologies for New-type Urban Distribution Network with Controllable Sources and Loads.
文摘The petal-shaped distribution network has high power supply reliability.However,the closed-loop operation mode and the access of inverter-interfaced distributed generators(IIDGs)bring great challenges to the protection schemes.The current amplitude differential protection is an effective means to solve this problem,but the existing criterions rarely consider both sensitivity to high-resistance faults and low requirements for data synchronization.Therefore,the general variation laws of the amplitude difference between the current steady-state components at both terminals and the phase differences between current fault components at both terminals are revealed.For external faults,the steady-state-component current amplitude difference is around zero and the fault-component current phase difference is around 180◦.For internal faults,either the amplitude difference is large or the phase difference is small.Accordingly,a current differential protection scheme based on the pre-fault and postfault steady-state current is proposed.The amplitude and phase of current at both terminals of the protected line are required in the proposed scheme,which has low requirements for data synchronization.The simulation results show that the proposed protection scheme is not affected by the fault type,position,resistance and capacity of the IIDGs.It can also be applied to radial distribution networks with IIDGs.
基金supported by National Natural Science Foundation of China under Grant 51807091the China Postdoctoral Science Foundation under Grant 2019M661846Open Research Fund of Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education,EPSRC under Grant EP/N032888/1,and the International Science and Technology Collaborative Project of Policy Guidance Plan of Jiangsu Province under Grant BZ2018026.
文摘There are various types of distributed generators (DGs) with different grid integration strategies. The transient characteristics of the fault currents provided by the DGs are different to those of conventional synchronous generators. In this paper, a distribution network with multi-type DGs is investigated, including consideration of DG low-voltage ride through (LVRT). The fault current characteristics of two typical DGs, i.e. an inverter-interfaced distributed generator (IIDG) and a doubly-fed induction generator (DFIG), are analyzed, considering the specific operation modes. Based on analysis of the fault characteristics, an equivalent model of the multi-type DGs under symmetrical/asymmetrical fault conditions is established. A fast-iterative fault calculation method for enhancing the calculation efficiency while avoiding local convergence is then proposed using an improved particle swarm optimization (PSO) algorithm. A simulation system of the distribution network with multi-type DGs is established in PSCAD/EMTDC. The simulation results validate the high accuracy and calculation efficiency of the proposed calculation method of the fault components. This can assist in the settings of the protection threshold.
基金Foundation item:The National Natural Science Foundation of China(No.60496311)
文摘The composite channel models of the generalized distributed antenna system （GDAS） such as Rayleigh-lognormal fading are studied. Then comparisons are performed between the GDAS and the traditional multiple-input multiple-output （MIMO） system to analyze the ergodic capacity of the GDAS and make conclusions that it is impossible to achieve an analytical expression for the ergodic capacity of the GDAS. Moreover, in order to evaluate the performance of the ergodic capacity of the GDAS conveniently, the analytical lower bound and upper bound of the ergodic capacity of the GDAS are derived by using the results from multivariate statistics and matrix inequalities, under the scenarios of Rayleigh-lognormal fading and equal power allocation scheme at transmitter. Finally, the analytical bounds are verified by comparisons with the numerical results.
基金the National Renewable Energy Laboratory(NREL)operated by Alliance for Sustainable Energy,LLC,for the U.S.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308the U.S.Department of Energy Office of Electricity AOP Distribution Grid Resilience Project.The views expressed in the article do not necessarily represent the views of the DOE or the U.S.Government.The U.S.Government retains and the publisher,by accepting the article for publication,acknowledges that the U.S.Government retains a nonexclusive,paid-up,irrevocable,worldwide license to publish or reproduce the published form of this work,or allow others to do so,for U.S.Government purposes.
文摘The rapid growth of distributed generator(DG)capacities has introduced additional controllable assets to improve the performance of distribution systems in terms of service restoration.Renewable DGs are of particular interest to utility companies,but the stochastic nature of intermittent renewable DGs could have a negative impact on the electric grid if they are not properly handled.In this study,we investigate distribution system service restoration using DGs as the primary power source,and we develop an effective approach to handle the uncertainty of renewable DGs under extreme conditions.The distribution system service restoration problem can be described as a mixed-integer second-order cone programming model by modifying the radial topology constraints and power flow equations.The uncertainty of renewable DGs will be modeled using a chance-constrained approach.Furthermore,the forecast errors and noises in real-time operation are solved using a novel model-free control algorithm that can automatically track the trajectory of real-time DG output.The proposed service restoration strategy and model-free control algorithm are validated using an IEEE 123-bus test system.
文摘Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expression of the solutions are given by the generalized inverse one of bounded linear operator. This is theoretically important for studying the stabilization and asymptotic stability of the second order generalized distributed parameter system.
基金supported by the Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.,China (J2022160,Research on Key Technologies of Distributed Power Dispatching Control for Resilience Improvement of Distribution Networks).
文摘To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When an extreme event occurs,the controllable generators form temporary microgrids(MGs)to restore the load maximally.Simultaneously,a demand response program(DRP)mitigates the imbalance between the power supply and demand during extreme events.To cope with the fault uncertainty,a robust optimization(RO)method is applied to reduce the long-term investment and short-term operation costs.The optimization is formulated as a tri-level defenderattacker-defender(DAD)framework.At the first level,decision-makers work out the DG allocation scheme;at the second level,the attacker finds the optimal attack strategy with maximum damage;and at the third level,restoration measures,namely distribution network reconfiguration(DNR)and demand response are performed.The problem is solved by the nested column and constraint generation(NC&CG)method and the model is validated using an IEEE 33-node system.Case studies validate the effectiveness and superiority of the proposed model according to the enhanced resilience and reduced cost.
基金the National Natural Science Foundation of China(61573285).
文摘Owing to the wide range of applications in various fields,generative models have become increasingly popular.However,they do not handle spatio-temporal features well.Inspired by the recent advances in these models,this paper designs a distributed spatio-temporal generative adversarial network(STGAN-D)that,given some initial data and random noise,generates a consecutive sequence of spatio-temporal samples which have a logical relationship.This paper builds a spatio-temporal discriminator to distinguish whether the samples generated by the generator meet the requirements for time and space coherence,and builds a controller for distributed training of the network gradient updated to separate the model training and parameter updating,to improve the network training rate.The model is trained on the skeletal dataset and the traffic dataset.In contrast to traditional generative adversarial networks(GANs),the proposed STGAN-D can generate logically coherent samples with the corresponding spatial and temporal features while avoiding mode collapse.In addition,this paper shows that the proposed model can generate different styles of spatio-temporal samples given different random noise inputs,and the controller can improve the network training rate.This model will extend the potential range of applications of GANs to areas such as traffic information simulation and multiagent adversarial simulation.
基金Project supported by National High-Technology Research andDevelopment Program of China (Grant No .2002AA517020)
文摘Control design is important for PEMFC （proton exchange membrane fuel cell） distributed power generator to satisfy user requirement for safe and stable operation. For a complex multi-variable dynamic system, a dynamic simulation model is first established. In view of close coupling and non-linear relationships between variables, the intelligent auto-adapted PI decoupling control method is used. From the simulation results it is found that, by bringing quadratic performance index in the single neuron, constructing adaptive PI controller, and adjusting gas flow rates through the second pressure relief valve and air compressor coordinately, both anode and cathode pressures can be maintained at ideal levels.
基金Program ofNational Natural Science Foundation of China(No. 60496312) Program of Beijing NaturalScience Foundation (No. 4042021)
文摘In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code (STC), Joint Transmission (JT) and Multiple Input Multiple Output (MIMO), and to meet the requirements of high-bit-rate multimedia services, new network topologies should be studied. Generalized distributed multicell architecture can take full advantage of multi-antenna technologies and solve the problem of frequent handover caused by higher carrier frequencies. Group handover, the handover policy based on the architecture, can eliminate the cell edge effect. Furthermore, by applying the concept of group handover to 3G mobile communication systems, the Fast Cell Group Selection (FCGS) scheme can effectively improve the data rate for cell edge users.
基金Under the auspices of the Key R&D Program of Xinjiang Uygur Autonomous Region(No.2022B03021)Tianshan Talent Training Program of Xinjiang Uygur Autonomous Region(No.2022TSYCLJ0011)+2 种基金Transformation of Scientific and Technological Achievements from the Qinghai Province(No.2020-SF-145)the 2020 Qinghai Kunlun Talents-leading Scientists Project(No.2020-LCJ-02)Key Program of International Cooperation,Bureau of International Cooperation,Chinese Academy of Sciences(No.131551KYSB20210030)。
文摘Long-term regional extreme cold events(ECEs)garner significant attention due to their widespread impact and prolonged duration,posing critical threats to human society and ecosystems.Previous studies have examined ECE characteristics at single sites or grid points,however,it is crucial to recognize that such events generally manifest as spatiotemporally continuous regional phenomena.Here,we proposed an objective methodology based on spatiotemporal continuity to identify ECEs in the China-Pakistan Economic Corridor(CPEC)during the winters of 1961-2015.This approach successfully reproduced the dynamic evolution of ECEs,encompassing their initiation,development,and dissipation.We further analyzed the changes of ECE intensity,frequency,and duration,and assessed ECE trends within varying return periods by employing the generalized Pareto distribution(GPD).Our findings reveal a decline in the frequency and duration of ECEs in CPEC over the study period,while their intensity has increased by 50%.ECEs predominantly occur in the northern regions of Azad Kashmir and Balochistan’s Quetta in Pakistan,and Kashgar in China.High recurrence levels are associated with an expansion of ECE-prone areas,particularly in the northern Pamir Plateau,which emerges as a regional hotspot.These results highlight the critical need to remain vigilant to potential future surges in ECEs under global warming,underscoring their implications for regional climate resilience.
文摘A new extended distribution called the Odd Exponential Generalized Exponential-Exponential distribution(EOEGE-E)is proposed based on generalization of the odd generalized exponential family(OEGE-E).The statistical properties of the proposed distribution are derived.The study evaluates the accuracy of six estimation methods under complete samples.Estimation techniques include maximumlikelihood,ordinary least squares,weighted least squares,maximumproduct of spacing,Cramer vonMises,and Anderson-Darling methods.Twomethods of estimation for the involved parameters are considered based on progressively type Ⅱ censored data(PTⅡC).These methods are maximum likelihood and maximum product of spacing.The proposed distribution’s effectiveness was evaluated using different data sets from various fields.The proposed distribution provides a better fit for these datasets than existing probability distributions.
基金supported by the Hebei Provincial Key Research and Development Program[grant numbers 23375401D and22375404D]the China Meteorological Administration[grant number FPZJ2024-011]the Hebei Meteorological Bureau[grant number21ky32]。
文摘Frequent extreme heat events exacerbated by global warming pose a significant threat to human health.However,the dynamic changes in human thermal comfort during such regional extremes remain understudied.This study investigates the spatiotemporal characteristics of the Universal Thermal Climate Index(UTCI)during 5-year return period extreme heat events across the Beijing-Tianjin-Hebei(BTH)region of China,utilizing 40 years of meteorological data from 174 stations.A non-stationary Generalized Extreme Value distribution model with a location parameter link function was identified as the optimal model(for 65.3%of stations)through the Akaike Information Criterion,capturing 16 regional extreme heat events.Results indicate that extreme heat thresholds rise with increasing return periods,with the highest thresholds concentrated around Beijing and Shijiazhuang.Air temperature and mean radiant temperature were found to be the dominant factors influencing UTCI,with daytime air temperature contributing 47.03%to 50.64%and nighttime mean radiant temperature contributing up to 48.55%.Spatially,“extreme heat stress”conditions,as defined by UTCI,were predominantly observed in the southeastern plains of Beijing and southern Hebei Province.Diurnally,UTCI peaked between 1200 and 1600 BT(Beijing time),generally returning to“no heat stress”levels across most areas between 0000 and 0600 BT.These findings provide crucial insights into the dynamics of human thermal comfort during extreme heat events in the BTH region,offering valuable scientific support for developing targeted heat mitigation and adaptation strategies.
文摘To utilize residual redundancy to reduce the error induced by fading channels and decrease the complexity of the field model to describe the probability structure for residual redundancy, a simplified statistical model for residual redundancy and a low complexity joint source-channel decoding（JSCD） algorithm are proposed. The complicated residual redundancy in wavelet compressed images is decomposed into several independent 1-D probability check equations composed of Markov chains and it is regarded as a natural channel code with a structure similar to the low density parity check （LDPC） code. A parallel sum-product （SP） and iterative JSCD algorithm is proposed. Simulation results show that the proposed JSCD algorithm can make full use of residual redundancy in different directions to correct errors and improve the peak signal noise ratio （PSNR） of the reconstructed image and reduce the complexity and delay of JSCD. The performance of JSCD is more robust than the traditional separated encoding system with arithmetic coding in the same data rate.
文摘Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.
文摘In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected induction motors will also be used. In the circumstances, a smart power conversion unit is one of key components, which can integrate these DC or AC apparatus and trade power among them. Authors have developed an integrated power converter based on a well-known circuit topology of flying capacitor multilevel converter. This paper describes the detail of the circuit topology and its characteristics depending on designed parameters. The achieved power quality is also verified by simulation study.
