The electric power enterprise is an important basic energy industry for national development,and it is also the first basic industry of the national economy.With the continuous expansion of State Grid,the progressivel...The electric power enterprise is an important basic energy industry for national development,and it is also the first basic industry of the national economy.With the continuous expansion of State Grid,the progressively complex operating conditions,and the increasing scope and frequency of data collection,how to make reasonable use of electrical big data,improve utilization,and provide a theoretical basis for the reliability of State Grid operation,has become a new research hot spot.Since electrical data has the characteristics of large volume,multiple types,low-value density,and fast processing speed,it is a challenge to mine and analyze it deeply,extract valuable information efficiently,and serve for the actual problem.According to the features of these data,this paper uses artificial intelligence methods such as time series and support vector regression to establish a data mining network model for standard cost prediction through transfer learning.The experimental results show that the model in this paper obtains better prediction results on a small sample data set,which verifies the feasibility of the deep transfer model.Compared with activity-based costing and the traditional prediction method,the average absolute error of the proposed method is reduced by 10%,which is effective and superior.展开更多
Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such l...Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,Newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.展开更多
In order to promote the tolerance and controllability of the multi-degree-of-freedom(M-DOF) ultrasonic motor, a novel two-degree-of-freedom(2-DOF) spherical ultrasonic motor using three traveling-wave type annular sta...In order to promote the tolerance and controllability of the multi-degree-of-freedom(M-DOF) ultrasonic motor, a novel two-degree-of-freedom(2-DOF) spherical ultrasonic motor using three traveling-wave type annular stators was put forward. Firstly,the structure and working principle of this motor were introduced, especially a spiral spring as the preload applied component was designed for adaptive adjustment. Then, the friction drive model of 2-DOF spherical motor was built up from spatial geometric relation between three annular stators and the spherical rotor which was used to analyze the mechanical characteristics of the motor.The optimal control strategy for minimum norm solution of three stators' angular velocity was proposed, using Moore-Penrose generalized inverse matrix. Finally, a 2-DOF prototype was fabricated and tested, which ran stably and controllably. The maximum no-load velocity and stall torque are 92 r/min and 90 m N·m, respectively. The 2-DOF spherical ultrasonic motor has compact structure, easy assembly, good performance and stable operation.展开更多
The low frequency oscillation characteristics of East China Power Grid after commissioning of the first ultra-high voltage alternating current(UHVAC)project-the Huai-Hu UHVAC project are studied.Several low frequency ...The low frequency oscillation characteristics of East China Power Grid after commissioning of the first ultra-high voltage alternating current(UHVAC)project-the Huai-Hu UHVAC project are studied.Several low frequency oscillation cases occurred in East China Power Grid in the past few years are reviewed and summarized.Based on the analysis of the different typical operation modes,the main low frequency oscillation modes in East China Power Grid in the early stages of development of ultra-high voltage(UHV)are summarized,and the impacts of the significant power grid maintenance on low frequency oscillation characteristics are analyzed.Besides,the oscillation mode of UHV generators to East China Power Grid is researched,and the importance of the power system stabilizator(PSS)is emphasized.Furthermore,the comparative analysis between the time domain and the frequency domain is carried out,and the influences of the governing system on low frequency oscillation characteristics are revealed.Finally,both the focus and the direction of low frequency oscillation research are presented.展开更多
The effective identifications of important nodes in power grid are foundations of differentiated management and stable operation of power grid. However, the current studies on this field are not thorough enough. This ...The effective identifications of important nodes in power grid are foundations of differentiated management and stable operation of power grid. However, the current studies on this field are not thorough enough. This paper applies the model based on co-citation(MBCC)-hypertext induced topic selection(HITS) algorithm used in web page ranking to power grid and proposes an index to determine node importance of power grid from the perspectives of inflow and outflow power. MBCC-HITS algorithm is modified considering load, power source, and line flow comprehensively for the differences between Internet and power grid in this paper. Then a method for evaluating node importance is proposed using the modified algorithm. Lastly, the rationality and validity of the proposed method are verified by comparisons with other methods in case studies of IEEE 14-bus and 118-bus systems.展开更多
To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that...To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that,He APPJ is first ignited,which is independent of the dielectric barrier discharge(DBD)between the two wrapped electrodes when the high voltage placed at the downstream.The intensity and APPJ length under positive discharge pulses are bigger than that under negative discharge pulses due to the space charge effect.The He APPJ is formed by the DBD development when the high-voltage electrode placed at the upstream side of tube.However,the plasma plume in Ar APPJ is formed by the propagation of DBD whatever the high-voltage electrode is arranged on upstream or downstream side of ground electrode.The difference in formation mechanism between He and Ar APPJs is mainly caused by the gas properties.Moreover,during the discharges,Ar tends to lead to thermal instability and electron Maxwellian instability.展开更多
Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application...Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.展开更多
Internet of Things(IoT)technology is rapidly evolving,but there is no trusted platform to protect user privacy,protect information between different IoT domains,and promote edge processing.Therefore,we integrate the b...Internet of Things(IoT)technology is rapidly evolving,but there is no trusted platform to protect user privacy,protect information between different IoT domains,and promote edge processing.Therefore,we integrate the blockchain technology into constructing trusted IoT platforms.However,the application of blockchain in IoT is hampered by the challenges posed by heavy computing processes.To solve the problem,we put forward a blockchain framework based on mobile edge computing,in which the blockchain mining tasks can be offloaded to nearby nodes or the edge computing service providers and the encrypted hashes of blocks can be cached in the edge computing service providers.Moreover,we model the process of offloading and caching to ensure that both edge nodes and edge computing service providers obtain the maximum profit based on game theory and auction theory.Finally,the proposed mechanism is compared with the centralized mode,mode A(all the miners offload their tasks to the edge computing service providers),and mode B(all the miners offload their tasks to a group of neighbor devices).Simulation results show that under our mechanism,mining networks obtain more profits and consume less time on average.展开更多
In this paper, a power allocation problem based on the Cournot game and generalized Nash game is proposed. After integrating dynamic average consensus algorithm and distributed projection neural network through singul...In this paper, a power allocation problem based on the Cournot game and generalized Nash game is proposed. After integrating dynamic average consensus algorithm and distributed projection neural network through singular perturbation systems, a normalized Nash equilibrium seeking algorithm is presented to solve the proposed power allocation problem in a distributed way.Combine Lyapunov stability with the singular perturbation analysis, the convergence of the proposed algorithm is analyzed. A simulation on IEEE 118-bus confirms that the proposed distributed algorithm can adjust the power allocation according to different situations, while keeping the optimal solution within the feasible set.展开更多
The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will ...The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will greatly deepen the coupling of the electricity-gas integrated energy system,improve the flexibility and safety of the operation of the power system,and bring a deal of benefits to the power system.On this background,an optimal dispatch model of RIES combined cold,heat,gas and electricity with SOP is proposed.Firstly,RIES architecture with SOP and P2G is designed and its mathematical model also is built.Secondly,on the basis of considering the optimal scheduling of combined cold,heat,gas and electricity,the optimal scheduling model for RIES was established.After that,the original model is transformed into a mixed-integer second-order cone programming model by using linearization and second-order cone relaxation techniques,and the CPLEX solver is invoked to solve the optimization problem.Finally,the modified IEEE 33-bus systemis used to analyze the benefits of SOP,P2G technology and lithium bromide absorption chillers in reducing systemnetwork loss and cost,as well as improving the system’s ability to absorb wind and solar and operating safety.展开更多
When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and p...When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and possibly induces insulator flashover. Lighting rod arrester is used to shield the tower and provide another routine for lightning current, decreasing the potential of tower overhead. In this paper, the performance of a 500 kV lighting rod arrester is tested used in AC transmission system under the current impulse. Besides, the influence of the lightning rod arrester performance on the top potential of tower is also studied. The results show that, when the rod arrester is connected to the tower, the top potential of tower can be obviously limited under the lightning strike.展开更多
In recent years, the increasing penetration level of renewable generation and combined heat and power(CHP) technology in power systems is leading to significant changes in energy production and consumption patterns. A...In recent years, the increasing penetration level of renewable generation and combined heat and power(CHP) technology in power systems is leading to significant changes in energy production and consumption patterns. As a result, the integrated planning and optimal operation of a multi-carrier energy(MCE) system have aroused widespread concern for reasonable utilization of multiple energy resources and efficient accommodation of renewable energy sources. In this context, an integrated demand response(IDR) scheme is designed to coordinate the operation of power to gas(P2 G) devices, heat pumps,diversified storage devices and flexible loads within an extended modeling framework of energy hubs. Subsequently, the optimal dispatch of interconnected electricity,natural gas and heat systems is implemented considering the interactions among multiple energy carriers by utilizing the bi-level optimization method. Finally, the proposed method is demonstrated with a 4-bus multi-energy systemand a larger test case comprised of a revised IEEE 118-bus power system and a 20-bus Belgian natural gas system.展开更多
This paper proposes a generation dispatch model based on the maximum entropy principle. The objective is to find an optimal generation dispatch strategy that minimizes the generation cost and satisfies the security co...This paper proposes a generation dispatch model based on the maximum entropy principle. The objective is to find an optimal generation dispatch strategy that minimizes the generation cost and satisfies the security constraints of power systems, while taking into account the uncertainty of wind power. Since in many situations, only partial information of the probabilistic variables can be obtained, the maximum entropy principle is introduced to find the most likely realized probability distributions of the power flow, thus providing an accurate probabilistic circumstance to solve the generation dispatch model. The proposed method is tested on the IEEE 39-bus system, and is compared with the methodologies based on Monte Carlo simulation and Gram-Charlier expansions.展开更多
Boosting the resilience of power systems is a core requirement of smart grids. In fact, resilience enhancement is crucial to all critical infrastructure systems.In this study, we review the current research on system ...Boosting the resilience of power systems is a core requirement of smart grids. In fact, resilience enhancement is crucial to all critical infrastructure systems.In this study, we review the current research on system resilience enhancement within and beyond smart grids. In addition, we elaborate on resilience definition and resilience quantification and discuss several challenges and opportunities for system resilience enhancement. This study aims to deepen our understanding of the concept of resilience and develop a wide perspective on enhancing the system resilience for critical infrastructures.展开更多
Universal Generating Function(UGF)techniques have been applied to Multi-State System(MSS)reliability analysis,such as long term reserve expansion of power systems with high wind power penetration.However,using simple ...Universal Generating Function(UGF)techniques have been applied to Multi-State System(MSS)reliability analysis,such as long term reserve expansion of power systems with high wind power penetration.However,using simple steady-state distribution models for wind power and large generating units in reliability assessment can yield pessimistic appraisals.To more accurately assess the power system reliability,UGF techniques are extended to dynamic probabilistic simulation analysis on two aspects of modelling improvement.Firstly,a principal component analysis(PCA)combined with a hierarchal clustering algorithm is used to achieve the salient and time-varying patterns of wind power,then a sequential UGF equivalent model of wind power output is established by an apportioning method.Secondly,other than the traditional two-state models,the conventional generator UGF equivalent model is established as a four discrete-state continuous-time Markov model by Lztransform.In the construction process of such a UGF model,the state values are transformed into the integral multiples of one common factor by choosing proper common factors,thus effectively restraining the exponential growth of its state number and alleviating the explosion thereof.The method is suitable for reliability assessment with dynamic probabilistic distributed random variables.In addition,by acquiring the clustering information of wind power,the system reliability indices,such as fuel cost and CO_(2) emissions through different seasons and on different workdays,are calculated.Finally,the effectiveness of the method is verified by a modified IEEE-RTS 79 system integrated with several wind farms of historical hourly wind power data of Zhangbei wind farm in North China.展开更多
The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established b...The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established by analyzing the characteristics of SAS,according to IEC 61850.Then,we propose a method,which combines topology value and information adjunction value by introducing a first-order linear feedback controller to quantify the value of LNs.On this basis,some definitions for equivalent network conversion are proposed to greatly reduce the complexity of the original network topology.Also,the absolute value and relative value are introduced to quantify LN importance from the perspective of the node’s necessity and influence,respectively.Finally,simulation results of the case study demonstrate that the proposed method is effective and provides a broader and clearer perspective for viewing the logical node importance for IEC61850 based SAS.展开更多
DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,b...DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,because the parasitic capacitances of the main equipment oscillate with the lumped inductances of the HVDC system,strong electromagnetic oscillations with multiple frequencies occur during clearance transients.These oscillations will disturb the HVDC system’s protection and control systems.Therefore,this paper focuses on the modeling of these oscillations.First,an equivalent circuit for the MMC-based HVDC system is proposed,taking into account the parasitic capacitances of the system’s major components,such as DC reactors,connecting cables,and DC circuit breakers(DCCBs).Second,four distinct oscillation stages are postulated based on action coordination of MMCs and DCCBs,and the associated analytical equations for the oscillation frequencies are derived.Third,a 200 kV MMC-based DC converter station is subjected to an 6ms/6kA pole-to-pole(PTP)short-circuit test.Electromagnetic oscillations have a frequency range of several kHz to several hundreds of kHz.The measured waveforms correspond well with simulated results,including the parasitic characteristics.Additionally,the relative errors between the simulated and measured frequencies are less than 5%.展开更多
Diagnosing insulation intrinsic ageing is essential for preventing insulation failure of submarine cables,and in case of failure,helping in any decision about maintenance actions.In this study,a novel aged cable diagn...Diagnosing insulation intrinsic ageing is essential for preventing insulation failure of submarine cables,and in case of failure,helping in any decision about maintenance actions.In this study,a novel aged cable diagnosis approach based on high-voltage frequency domain spectroscopy(HV-FDS)with broader frequency width is proposed to analyse the high-field polarisation characteristics and conductivity behaviour of 500 kV submarine polymeric cables insulation,aiming to support the evaluation of overall insulation ageing.The measurement principle of HV-FDS and relaxation mechanism are stated,and then focus is on studying the extent of change of polarisation and conduction properties of submarine cables insulation as a function of ageing stress and time.Moreover,the high-field polarisation characteristics and conductivity behaviour are discussed in-depth based on the carrier transport and trap properties.Finally,the novel diagnostic indicator based on the high-field characteristics is extracted to quantify the thermal ageing state of submarine cables insulation.Results show that the high-field polarisation characteristics and conductivity behaviour seem to become sensitive diagnostic quantities if measured at reasonably high voltage,which are able to reveal mechanisms associated with thermo-oxidative ageing as that generated in the testing procedure considered in this paper.Sensitivity is considerably higher than that experienced in typical dielectric spectroscopy approaches.展开更多
Charging piles are used for charging electric vehicles and are directly accessible to users in an energy internet entrance,while playing an important role in energy consumption.Currently,each enterprise constructs the...Charging piles are used for charging electric vehicles and are directly accessible to users in an energy internet entrance,while playing an important role in energy consumption.Currently,each enterprise constructs the center of operation and maintenance of their systems independently,along with their respective APP payment programs.This results in high operating costs,poor user experience,and low utilization rate of the pile,which limits the promotion and popularization of electric vehicles.To overcome this limitation,there is a need for a multi-center,fair,and transparent consortium blockchain,which can conform to the application requirements of a unified payment system and accommodate a range of diverse enterprise charging piles.In this paper,the design for a consensus and incentive program for consortium blockchain is presented.First,the application status of blockchain in an energy internet is described.Then,the logical structure and hierarchical model of the consortium blockchain are analyzed.Next,multicycle accounting and limiting the amount of accounting nodes in each round is presented to ensure the overhead of consensus remain constant.Finally,the accounting incentive mechanism and the bidding encouragement strategy based on“electric beans”are designed.展开更多
基金Supported by the program of science and technology of State Grid Zhejiang Electric Power Co.,Ltd.,named Research and application project of standard cost activity based on machine learning(5211JH1900LZ).
文摘The electric power enterprise is an important basic energy industry for national development,and it is also the first basic industry of the national economy.With the continuous expansion of State Grid,the progressively complex operating conditions,and the increasing scope and frequency of data collection,how to make reasonable use of electrical big data,improve utilization,and provide a theoretical basis for the reliability of State Grid operation,has become a new research hot spot.Since electrical data has the characteristics of large volume,multiple types,low-value density,and fast processing speed,it is a challenge to mine and analyze it deeply,extract valuable information efficiently,and serve for the actual problem.According to the features of these data,this paper uses artificial intelligence methods such as time series and support vector regression to establish a data mining network model for standard cost prediction through transfer learning.The experimental results show that the model in this paper obtains better prediction results on a small sample data set,which verifies the feasibility of the deep transfer model.Compared with activity-based costing and the traditional prediction method,the average absolute error of the proposed method is reduced by 10%,which is effective and superior.
基金supported in part by the National Natural Science Foundation of China(No.52177071).
文摘Medium-voltage distribution systems(MVDSs)mainly consist of a feeder head,lines,distribution transformers,and the equivalent load or power supply interfaced with the distribution transformers.The information of such load or power supply can be measured via the three-wattmeter method(THM)and the two-wattmeter method(TWM).The measurements can be used to perform the control of the power supply and simulate the characteristics of the load,so the models of the load and the power supply need to consider the measurement characteristics.Existing research works on three-phase power flow(PF)just consider the measurement characteristics of THM.Hence,the PF equation of the bus measured via TWM is firstly built.Based on conventional measurements,an accurate and general model of the grounded and ungrounded slack bus is proposed.Furthermore,the influence arising from the connection type and angle shift of distribution transformers on the admittance matrix is considered,and thus a general three-phase transformer model is summarized,which is applicable for all the transformers mentioned herein.Finally,Newton's method is adopted to solve the PF calculation,and the performance of the proposed PF model is demonstrated through designed tests.
基金Project(51107111)supported by the National Natural Science Foundation of China
文摘In order to promote the tolerance and controllability of the multi-degree-of-freedom(M-DOF) ultrasonic motor, a novel two-degree-of-freedom(2-DOF) spherical ultrasonic motor using three traveling-wave type annular stators was put forward. Firstly,the structure and working principle of this motor were introduced, especially a spiral spring as the preload applied component was designed for adaptive adjustment. Then, the friction drive model of 2-DOF spherical motor was built up from spatial geometric relation between three annular stators and the spherical rotor which was used to analyze the mechanical characteristics of the motor.The optimal control strategy for minimum norm solution of three stators' angular velocity was proposed, using Moore-Penrose generalized inverse matrix. Finally, a 2-DOF prototype was fabricated and tested, which ran stably and controllably. The maximum no-load velocity and stall torque are 92 r/min and 90 m N·m, respectively. The 2-DOF spherical ultrasonic motor has compact structure, easy assembly, good performance and stable operation.
文摘The low frequency oscillation characteristics of East China Power Grid after commissioning of the first ultra-high voltage alternating current(UHVAC)project-the Huai-Hu UHVAC project are studied.Several low frequency oscillation cases occurred in East China Power Grid in the past few years are reviewed and summarized.Based on the analysis of the different typical operation modes,the main low frequency oscillation modes in East China Power Grid in the early stages of development of ultra-high voltage(UHV)are summarized,and the impacts of the significant power grid maintenance on low frequency oscillation characteristics are analyzed.Besides,the oscillation mode of UHV generators to East China Power Grid is researched,and the importance of the power system stabilizator(PSS)is emphasized.Furthermore,the comparative analysis between the time domain and the frequency domain is carried out,and the influences of the governing system on low frequency oscillation characteristics are revealed.Finally,both the focus and the direction of low frequency oscillation research are presented.
基金supported by State Grid Technology Project(No.GY71-14-075)
文摘The effective identifications of important nodes in power grid are foundations of differentiated management and stable operation of power grid. However, the current studies on this field are not thorough enough. This paper applies the model based on co-citation(MBCC)-hypertext induced topic selection(HITS) algorithm used in web page ranking to power grid and proposes an index to determine node importance of power grid from the perspectives of inflow and outflow power. MBCC-HITS algorithm is modified considering load, power source, and line flow comprehensively for the differences between Internet and power grid in this paper. Then a method for evaluating node importance is proposed using the modified algorithm. Lastly, the rationality and validity of the proposed method are verified by comparisons with other methods in case studies of IEEE 14-bus and 118-bus systems.
基金Project supported by China National Fund for Distinguished Young Scientists(51125029)
文摘To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that,He APPJ is first ignited,which is independent of the dielectric barrier discharge(DBD)between the two wrapped electrodes when the high voltage placed at the downstream.The intensity and APPJ length under positive discharge pulses are bigger than that under negative discharge pulses due to the space charge effect.The He APPJ is formed by the DBD development when the high-voltage electrode placed at the upstream side of tube.However,the plasma plume in Ar APPJ is formed by the propagation of DBD whatever the high-voltage electrode is arranged on upstream or downstream side of ground electrode.The difference in formation mechanism between He and Ar APPJs is mainly caused by the gas properties.Moreover,during the discharges,Ar tends to lead to thermal instability and electron Maxwellian instability.
基金supported by SGCC Scientific and Technological Project(52110116004W)
文摘Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.
基金This work is supported by National Natural Science Foundation of China(61702048)。
文摘Internet of Things(IoT)technology is rapidly evolving,but there is no trusted platform to protect user privacy,protect information between different IoT domains,and promote edge processing.Therefore,we integrate the blockchain technology into constructing trusted IoT platforms.However,the application of blockchain in IoT is hampered by the challenges posed by heavy computing processes.To solve the problem,we put forward a blockchain framework based on mobile edge computing,in which the blockchain mining tasks can be offloaded to nearby nodes or the edge computing service providers and the encrypted hashes of blocks can be cached in the edge computing service providers.Moreover,we model the process of offloading and caching to ensure that both edge nodes and edge computing service providers obtain the maximum profit based on game theory and auction theory.Finally,the proposed mechanism is compared with the centralized mode,mode A(all the miners offload their tasks to the edge computing service providers),and mode B(all the miners offload their tasks to a group of neighbor devices).Simulation results show that under our mechanism,mining networks obtain more profits and consume less time on average.
基金supported by the National Natural Science Foundation of China (Grant No. 61673107)the Jiangsu Provincial Key Laboratory of Networked Collective Intelligence (Grant No. BM2017002)。
文摘In this paper, a power allocation problem based on the Cournot game and generalized Nash game is proposed. After integrating dynamic average consensus algorithm and distributed projection neural network through singular perturbation systems, a normalized Nash equilibrium seeking algorithm is presented to solve the proposed power allocation problem in a distributed way.Combine Lyapunov stability with the singular perturbation analysis, the convergence of the proposed algorithm is analyzed. A simulation on IEEE 118-bus confirms that the proposed distributed algorithm can adjust the power allocation according to different situations, while keeping the optimal solution within the feasible set.
基金Project Supported by National Natural Science Foundation of China(51777193).
文摘The Regional Integrated Energy System(RIES)has brought new modes of development,utilization,conversion,storage of energy.The introduction of Soft Open Point(SOP)and the application of Power to Gas(P2G)technology will greatly deepen the coupling of the electricity-gas integrated energy system,improve the flexibility and safety of the operation of the power system,and bring a deal of benefits to the power system.On this background,an optimal dispatch model of RIES combined cold,heat,gas and electricity with SOP is proposed.Firstly,RIES architecture with SOP and P2G is designed and its mathematical model also is built.Secondly,on the basis of considering the optimal scheduling of combined cold,heat,gas and electricity,the optimal scheduling model for RIES was established.After that,the original model is transformed into a mixed-integer second-order cone programming model by using linearization and second-order cone relaxation techniques,and the CPLEX solver is invoked to solve the optimization problem.Finally,the modified IEEE 33-bus systemis used to analyze the benefits of SOP,P2G technology and lithium bromide absorption chillers in reducing systemnetwork loss and cost,as well as improving the system’s ability to absorb wind and solar and operating safety.
文摘When the tower overhead is struck by the lightning impulse, the lightning current flows into the earth through the impedance of tower and the grounding resistance, which heightens potential of the tower overhead and possibly induces insulator flashover. Lighting rod arrester is used to shield the tower and provide another routine for lightning current, decreasing the potential of tower overhead. In this paper, the performance of a 500 kV lighting rod arrester is tested used in AC transmission system under the current impulse. Besides, the influence of the lightning rod arrester performance on the top potential of tower is also studied. The results show that, when the rod arrester is connected to the tower, the top potential of tower can be obviously limited under the lightning strike.
文摘In recent years, the increasing penetration level of renewable generation and combined heat and power(CHP) technology in power systems is leading to significant changes in energy production and consumption patterns. As a result, the integrated planning and optimal operation of a multi-carrier energy(MCE) system have aroused widespread concern for reasonable utilization of multiple energy resources and efficient accommodation of renewable energy sources. In this context, an integrated demand response(IDR) scheme is designed to coordinate the operation of power to gas(P2 G) devices, heat pumps,diversified storage devices and flexible loads within an extended modeling framework of energy hubs. Subsequently, the optimal dispatch of interconnected electricity,natural gas and heat systems is implemented considering the interactions among multiple energy carriers by utilizing the bi-level optimization method. Finally, the proposed method is demonstrated with a 4-bus multi-energy systemand a larger test case comprised of a revised IEEE 118-bus power system and a 20-bus Belgian natural gas system.
文摘This paper proposes a generation dispatch model based on the maximum entropy principle. The objective is to find an optimal generation dispatch strategy that minimizes the generation cost and satisfies the security constraints of power systems, while taking into account the uncertainty of wind power. Since in many situations, only partial information of the probabilistic variables can be obtained, the maximum entropy principle is introduced to find the most likely realized probability distributions of the power flow, thus providing an accurate probabilistic circumstance to solve the generation dispatch model. The proposed method is tested on the IEEE 39-bus system, and is compared with the methodologies based on Monte Carlo simulation and Gram-Charlier expansions.
基金supported by the Key Program of National Natural Science Foundation of China (Grant No. 51537010)the National Basic Research Program (973 Program) (Grant No. 2013CB228206)supported by the U.S. Department of Energy’s Office of Electricity Delivery and Energy Reliability
文摘Boosting the resilience of power systems is a core requirement of smart grids. In fact, resilience enhancement is crucial to all critical infrastructure systems.In this study, we review the current research on system resilience enhancement within and beyond smart grids. In addition, we elaborate on resilience definition and resilience quantification and discuss several challenges and opportunities for system resilience enhancement. This study aims to deepen our understanding of the concept of resilience and develop a wide perspective on enhancing the system resilience for critical infrastructures.
基金This work was supported by the National High Technology Research and Development Program of China(863 Program)(No.2011AA05A101)National Natural Science Foundation of China(No.51177092).
文摘Universal Generating Function(UGF)techniques have been applied to Multi-State System(MSS)reliability analysis,such as long term reserve expansion of power systems with high wind power penetration.However,using simple steady-state distribution models for wind power and large generating units in reliability assessment can yield pessimistic appraisals.To more accurately assess the power system reliability,UGF techniques are extended to dynamic probabilistic simulation analysis on two aspects of modelling improvement.Firstly,a principal component analysis(PCA)combined with a hierarchal clustering algorithm is used to achieve the salient and time-varying patterns of wind power,then a sequential UGF equivalent model of wind power output is established by an apportioning method.Secondly,other than the traditional two-state models,the conventional generator UGF equivalent model is established as a four discrete-state continuous-time Markov model by Lztransform.In the construction process of such a UGF model,the state values are transformed into the integral multiples of one common factor by choosing proper common factors,thus effectively restraining the exponential growth of its state number and alleviating the explosion thereof.The method is suitable for reliability assessment with dynamic probabilistic distributed random variables.In addition,by acquiring the clustering information of wind power,the system reliability indices,such as fuel cost and CO_(2) emissions through different seasons and on different workdays,are calculated.Finally,the effectiveness of the method is verified by a modified IEEE-RTS 79 system integrated with several wind farms of historical hourly wind power data of Zhangbei wind farm in North China.
基金This work was supported in part by the National Natural Science Foundation of China(U1866209)。
文摘The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established by analyzing the characteristics of SAS,according to IEC 61850.Then,we propose a method,which combines topology value and information adjunction value by introducing a first-order linear feedback controller to quantify the value of LNs.On this basis,some definitions for equivalent network conversion are proposed to greatly reduce the complexity of the original network topology.Also,the absolute value and relative value are introduced to quantify LN importance from the perspective of the node’s necessity and influence,respectively.Finally,simulation results of the case study demonstrate that the proposed method is effective and provides a broader and clearer perspective for viewing the logical node importance for IEC61850 based SAS.
基金supported by the National Key Research and Development Program of China(2021YFB2400602)。
文摘DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,because the parasitic capacitances of the main equipment oscillate with the lumped inductances of the HVDC system,strong electromagnetic oscillations with multiple frequencies occur during clearance transients.These oscillations will disturb the HVDC system’s protection and control systems.Therefore,this paper focuses on the modeling of these oscillations.First,an equivalent circuit for the MMC-based HVDC system is proposed,taking into account the parasitic capacitances of the system’s major components,such as DC reactors,connecting cables,and DC circuit breakers(DCCBs).Second,four distinct oscillation stages are postulated based on action coordination of MMCs and DCCBs,and the associated analytical equations for the oscillation frequencies are derived.Third,a 200 kV MMC-based DC converter station is subjected to an 6ms/6kA pole-to-pole(PTP)short-circuit test.Electromagnetic oscillations have a frequency range of several kHz to several hundreds of kHz.The measured waveforms correspond well with simulated results,including the parasitic characteristics.Additionally,the relative errors between the simulated and measured frequencies are less than 5%.
基金Project of Chongqing Human Resources and Social Security Bureau,Grant/Award Number:2020LY19Innovative Research Groups of the National Natural Science Foundation of China,Grant/Award Number:51321063111 Project,Grant/Award Number:BP0020005。
文摘Diagnosing insulation intrinsic ageing is essential for preventing insulation failure of submarine cables,and in case of failure,helping in any decision about maintenance actions.In this study,a novel aged cable diagnosis approach based on high-voltage frequency domain spectroscopy(HV-FDS)with broader frequency width is proposed to analyse the high-field polarisation characteristics and conductivity behaviour of 500 kV submarine polymeric cables insulation,aiming to support the evaluation of overall insulation ageing.The measurement principle of HV-FDS and relaxation mechanism are stated,and then focus is on studying the extent of change of polarisation and conduction properties of submarine cables insulation as a function of ageing stress and time.Moreover,the high-field polarisation characteristics and conductivity behaviour are discussed in-depth based on the carrier transport and trap properties.Finally,the novel diagnostic indicator based on the high-field characteristics is extracted to quantify the thermal ageing state of submarine cables insulation.Results show that the high-field polarisation characteristics and conductivity behaviour seem to become sensitive diagnostic quantities if measured at reasonably high voltage,which are able to reveal mechanisms associated with thermo-oxidative ageing as that generated in the testing procedure considered in this paper.Sensitivity is considerably higher than that experienced in typical dielectric spectroscopy approaches.
基金This research is supported by the Science and Technology Project of State Grid Corporation of China(SAP No.52110417000G).
文摘Charging piles are used for charging electric vehicles and are directly accessible to users in an energy internet entrance,while playing an important role in energy consumption.Currently,each enterprise constructs the center of operation and maintenance of their systems independently,along with their respective APP payment programs.This results in high operating costs,poor user experience,and low utilization rate of the pile,which limits the promotion and popularization of electric vehicles.To overcome this limitation,there is a need for a multi-center,fair,and transparent consortium blockchain,which can conform to the application requirements of a unified payment system and accommodate a range of diverse enterprise charging piles.In this paper,the design for a consensus and incentive program for consortium blockchain is presented.First,the application status of blockchain in an energy internet is described.Then,the logical structure and hierarchical model of the consortium blockchain are analyzed.Next,multicycle accounting and limiting the amount of accounting nodes in each round is presented to ensure the overhead of consensus remain constant.Finally,the accounting incentive mechanism and the bidding encouragement strategy based on“electric beans”are designed.