Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant infl...Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.展开更多
This paper investigates the anomaly-resistant decentralized state estimation(SE) problem for a class of wide-area power systems which are divided into several non-overlapping areas connected through transmission lines...This paper investigates the anomaly-resistant decentralized state estimation(SE) problem for a class of wide-area power systems which are divided into several non-overlapping areas connected through transmission lines. Two classes of measurements(i.e., local measurements and edge measurements) are obtained, respectively, from the individual area and the transmission lines. A decentralized state estimator, whose performance is resistant against measurement with anomalies, is designed based on the minimum error entropy with fiducial points(MEEF) criterion. Specifically, 1) An augmented model, which incorporates the local prediction and local measurement, is developed by resorting to the unscented transformation approach and the statistical linearization approach;2) Using the augmented model, an MEEF-based cost function is designed that reflects the local prediction errors of the state and the measurement;and 3) The local estimate is first obtained by minimizing the MEEF-based cost function through a fixed-point iteration and then updated by using the edge measuring information. Finally, simulation experiments with three scenarios are carried out on the IEEE 14-bus system to illustrate the validity of the proposed anomaly-resistant decentralized SE scheme.展开更多
In this paper,we optimize the spectrum efficiency(SE)of uplink massive multiple-input multiple-output(MIMO)system with imperfect channel state information(CSI)over Rayleigh fading channel.The SE optimization problem i...In this paper,we optimize the spectrum efficiency(SE)of uplink massive multiple-input multiple-output(MIMO)system with imperfect channel state information(CSI)over Rayleigh fading channel.The SE optimization problem is formulated under the constraints of maximum power and minimum rate of each user.Then,we develop a near-optimal power allocation(PA)scheme by using the successive convex approximation(SCA)method,Lagrange multiplier method,and block coordinate descent(BCD)method,and it can obtain almost the same SE as the benchmark scheme with lower complexity.Since this scheme needs three-layer iteration,a suboptimal PA scheme is developed to further reduce the complexity,where the characteristic of massive MIMO(i.e.,numerous receive antennas)is utilized for convex reformulation,and the rate constraint is converted to linear constraints.This suboptimal scheme only needs single-layer iteration,thus has lower complexity than the near-optimal scheme.Finally,we joint design the pilot power and data power to further improve the performance,and propose an two-stage algorithm to obtain joint PA.Simulation results verify the effectiveness of the proposed schemes,and superior SE performance is achieved.展开更多
The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topolo...The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.展开更多
The effects of stage numbers on power dissipation of pipeline analog-to-digital converter （ADC） are studied and a novel design method aiming for power optimization is presented. In this method, a minimum comparator ...The effects of stage numbers on power dissipation of pipeline analog-to-digital converter （ADC） are studied and a novel design method aiming for power optimization is presented. In this method, a minimum comparator number algorithm （MCNA） is first introduced, and then the optimum distribution of resolutions through pipeline ADC stages is deduced by MCNA. Based on the optimum stage-resolution distribution, an optimization method is established, which examines the precise function between ADC power and stage resolutions with a parameter of power ratio （Rp）. For 10-bit pipeline ADC with scaling down technology, the simulation results by using MATLAB CAD tools show that an eight-stage topology with 1-bit RSD correction achieves the power optimization indicated by the power reduction ratio.展开更多
New method for determination of optimal placement and value of installed capacity of renewable source of energy (RES) by the criterion of minimum losses of active power, that allows taking into consideration the depen...New method for determination of optimal placement and value of installed capacity of renewable source of energy (RES) by the criterion of minimum losses of active power, that allows taking into consideration the dependence of RES on natural conditions of region, schedule of energy supply, parameters and configuration of distribution network is suggested in the paper. Results of computations of test scheme confirm the efficiency of the proposed method and its simplicity as compared with the methods considered in literature sources.展开更多
Unit stream power is the most important and dominant parameter for the determination of transport rate of sand,gravel,and hyper-concentrated sediment with wash load.Minimum energy dissipation rate theory,or its simpli...Unit stream power is the most important and dominant parameter for the determination of transport rate of sand,gravel,and hyper-concentrated sediment with wash load.Minimum energy dissipation rate theory,or its simplified minimum unit stream power and minimum stream power theories,can provide engineers the needed theoretical basis for river morphology and river engineering studies.The Generalized Sediment Transport model for Alluvial River Simulation computer mode series have been developed based on the above theories.The computer model series have been successfully applied in many countries.Examples will be used to illustrate the applications of the computer models to solving a wide range of river morphology and river engineering problems.展开更多
In this paper we study the relationship between minimum rank of graph G and the minimum rank of graph for some families of special graph G, where is the jth power of graph G.
As an open network architecture,Wireless Computing PowerNetworks(WCPN)pose newchallenges for achieving efficient and secure resource management in networks,because of issues such as insecure communication channels and...As an open network architecture,Wireless Computing PowerNetworks(WCPN)pose newchallenges for achieving efficient and secure resource management in networks,because of issues such as insecure communication channels and untrusted device terminals.Blockchain,as a shared,immutable distributed ledger,provides a secure resource management solution for WCPN.However,integrating blockchain into WCPN faces challenges like device heterogeneity,monitoring communication states,and dynamic network nature.Whereas Digital Twins(DT)can accurately maintain digital models of physical entities through real-time data updates and self-learning,enabling continuous optimization of WCPN,improving synchronization performance,ensuring real-time accuracy,and supporting smooth operation of WCPN services.In this paper,we propose a DT for blockchain-empowered WCPN architecture that guarantees real-time data transmission between physical entities and digital models.We adopt an enumeration-based optimal placement algorithm(EOPA)and an improved simulated annealing-based near-optimal placement algorithm(ISAPA)to achieve minimum average DT synchronization latency under the constraint of DT error.Numerical results show that the proposed solution in this paper outperforms benchmarks in terms of average synchronization latency.展开更多
大规模风电机组并网使得电力系统等效惯量迅速下降,系统惯量逐渐接近临界水平,系统频率运行安全受到影响。为量化计算含大规模风电电力系统的最小惯量需求,文章首先基于经典系统频率响应(System Frequency Response,SFR)模型,建立了考...大规模风电机组并网使得电力系统等效惯量迅速下降,系统惯量逐渐接近临界水平,系统频率运行安全受到影响。为量化计算含大规模风电电力系统的最小惯量需求,文章首先基于经典系统频率响应(System Frequency Response,SFR)模型,建立了考虑大规模风电并网的SFR模型。首先,基于改进的SFR模型量化推导电力系统初始频率变化率、频率最低点等频率特征指标;其次,计算了风电场等效虚拟惯量,并结合电力系统惯量理论量化分析含大规模风电电力系统的理论惯量和计算惯量;再次,以动态频率特征为约束,提出含大规模风电电力系统最小惯量需求评估流程;最后,利用Matlab/Simulink对所提评估方法进行验证。展开更多
随着风电大规模的并网,其所具有的“零惯量”特征使电网惯量水平降低,频率特性恶化。为寻求风电并网对系统惯量水平的影响规律,明晰系统运行边界,对风电并网系统的惯量特性及最小惯量需求展开研究评估。首先,在同步发电机不同运行方式下...随着风电大规模的并网,其所具有的“零惯量”特征使电网惯量水平降低,频率特性恶化。为寻求风电并网对系统惯量水平的影响规律,明晰系统运行边界,对风电并网系统的惯量特性及最小惯量需求展开研究评估。首先,在同步发电机不同运行方式下,基于理论推导出评估风电并网系统惯量特性变化的计算表达式,并分析系统惯量特性的变化规律。在风电附加虚拟惯量控制情况下,以惯量响应过程提供的能量为出发点,基于系统惯量削弱量和风电虚拟惯量的平均惯量支撑功率,定义了一项惯量变化系数COIC,以此来判定系统惯量水平变化情况。其次,建立考虑风电渗透率的改进系统频率响应模型(System frequency response,SFR),量化系统惯量与风电渗透率的关系,给出了风电并网系统最小惯量评估方法。最后,搭建了含风电接入的4机2区域模型,对理论分析结果和评估方法进行了仿真验证。展开更多
文摘Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.
基金supported in part by the National Natural Science Foundation of China(61933007, U21A2019, 62273005, 62273088, 62303301)the Program of Shanghai Academic/Technology Research Leader of China (20XD1420100)+2 种基金the Hainan Province Science and Technology Special Fund of China(ZDYF2022SHFZ105)the Natural Science Foundation of Anhui Province of China (2108085MA07)the Alexander von Humboldt Foundation of Germany。
文摘This paper investigates the anomaly-resistant decentralized state estimation(SE) problem for a class of wide-area power systems which are divided into several non-overlapping areas connected through transmission lines. Two classes of measurements(i.e., local measurements and edge measurements) are obtained, respectively, from the individual area and the transmission lines. A decentralized state estimator, whose performance is resistant against measurement with anomalies, is designed based on the minimum error entropy with fiducial points(MEEF) criterion. Specifically, 1) An augmented model, which incorporates the local prediction and local measurement, is developed by resorting to the unscented transformation approach and the statistical linearization approach;2) Using the augmented model, an MEEF-based cost function is designed that reflects the local prediction errors of the state and the measurement;and 3) The local estimate is first obtained by minimizing the MEEF-based cost function through a fixed-point iteration and then updated by using the edge measuring information. Finally, simulation experiments with three scenarios are carried out on the IEEE 14-bus system to illustrate the validity of the proposed anomaly-resistant decentralized SE scheme.
基金supported by the Fundamental Research Funds for the Central Universities of NUAA(No.kfjj20200414)Natural Science Foundation of Jiangsu Province in China(No.BK20181289).
文摘In this paper,we optimize the spectrum efficiency(SE)of uplink massive multiple-input multiple-output(MIMO)system with imperfect channel state information(CSI)over Rayleigh fading channel.The SE optimization problem is formulated under the constraints of maximum power and minimum rate of each user.Then,we develop a near-optimal power allocation(PA)scheme by using the successive convex approximation(SCA)method,Lagrange multiplier method,and block coordinate descent(BCD)method,and it can obtain almost the same SE as the benchmark scheme with lower complexity.Since this scheme needs three-layer iteration,a suboptimal PA scheme is developed to further reduce the complexity,where the characteristic of massive MIMO(i.e.,numerous receive antennas)is utilized for convex reformulation,and the rate constraint is converted to linear constraints.This suboptimal scheme only needs single-layer iteration,thus has lower complexity than the near-optimal scheme.Finally,we joint design the pilot power and data power to further improve the performance,and propose an two-stage algorithm to obtain joint PA.Simulation results verify the effectiveness of the proposed schemes,and superior SE performance is achieved.
文摘The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.
基金Supported by the National Natural Science Foundation of China (No. 60072004)
文摘The effects of stage numbers on power dissipation of pipeline analog-to-digital converter （ADC） are studied and a novel design method aiming for power optimization is presented. In this method, a minimum comparator number algorithm （MCNA） is first introduced, and then the optimum distribution of resolutions through pipeline ADC stages is deduced by MCNA. Based on the optimum stage-resolution distribution, an optimization method is established, which examines the precise function between ADC power and stage resolutions with a parameter of power ratio （Rp）. For 10-bit pipeline ADC with scaling down technology, the simulation results by using MATLAB CAD tools show that an eight-stage topology with 1-bit RSD correction achieves the power optimization indicated by the power reduction ratio.
文摘New method for determination of optimal placement and value of installed capacity of renewable source of energy (RES) by the criterion of minimum losses of active power, that allows taking into consideration the dependence of RES on natural conditions of region, schedule of energy supply, parameters and configuration of distribution network is suggested in the paper. Results of computations of test scheme confirm the efficiency of the proposed method and its simplicity as compared with the methods considered in literature sources.
文摘Unit stream power is the most important and dominant parameter for the determination of transport rate of sand,gravel,and hyper-concentrated sediment with wash load.Minimum energy dissipation rate theory,or its simplified minimum unit stream power and minimum stream power theories,can provide engineers the needed theoretical basis for river morphology and river engineering studies.The Generalized Sediment Transport model for Alluvial River Simulation computer mode series have been developed based on the above theories.The computer model series have been successfully applied in many countries.Examples will be used to illustrate the applications of the computer models to solving a wide range of river morphology and river engineering problems.
文摘In this paper we study the relationship between minimum rank of graph G and the minimum rank of graph for some families of special graph G, where is the jth power of graph G.
基金supported by the National Natural Science Foundation of China under Grant 62272391in part by the Key Industry Innovation Chain of Shaanxi under Grant 2021ZDLGY05-08.
文摘As an open network architecture,Wireless Computing PowerNetworks(WCPN)pose newchallenges for achieving efficient and secure resource management in networks,because of issues such as insecure communication channels and untrusted device terminals.Blockchain,as a shared,immutable distributed ledger,provides a secure resource management solution for WCPN.However,integrating blockchain into WCPN faces challenges like device heterogeneity,monitoring communication states,and dynamic network nature.Whereas Digital Twins(DT)can accurately maintain digital models of physical entities through real-time data updates and self-learning,enabling continuous optimization of WCPN,improving synchronization performance,ensuring real-time accuracy,and supporting smooth operation of WCPN services.In this paper,we propose a DT for blockchain-empowered WCPN architecture that guarantees real-time data transmission between physical entities and digital models.We adopt an enumeration-based optimal placement algorithm(EOPA)and an improved simulated annealing-based near-optimal placement algorithm(ISAPA)to achieve minimum average DT synchronization latency under the constraint of DT error.Numerical results show that the proposed solution in this paper outperforms benchmarks in terms of average synchronization latency.
文摘大规模风电机组并网使得电力系统等效惯量迅速下降,系统惯量逐渐接近临界水平,系统频率运行安全受到影响。为量化计算含大规模风电电力系统的最小惯量需求,文章首先基于经典系统频率响应(System Frequency Response,SFR)模型,建立了考虑大规模风电并网的SFR模型。首先,基于改进的SFR模型量化推导电力系统初始频率变化率、频率最低点等频率特征指标;其次,计算了风电场等效虚拟惯量,并结合电力系统惯量理论量化分析含大规模风电电力系统的理论惯量和计算惯量;再次,以动态频率特征为约束,提出含大规模风电电力系统最小惯量需求评估流程;最后,利用Matlab/Simulink对所提评估方法进行验证。
文摘随着风电大规模的并网,其所具有的“零惯量”特征使电网惯量水平降低,频率特性恶化。为寻求风电并网对系统惯量水平的影响规律,明晰系统运行边界,对风电并网系统的惯量特性及最小惯量需求展开研究评估。首先,在同步发电机不同运行方式下,基于理论推导出评估风电并网系统惯量特性变化的计算表达式,并分析系统惯量特性的变化规律。在风电附加虚拟惯量控制情况下,以惯量响应过程提供的能量为出发点,基于系统惯量削弱量和风电虚拟惯量的平均惯量支撑功率,定义了一项惯量变化系数COIC,以此来判定系统惯量水平变化情况。其次,建立考虑风电渗透率的改进系统频率响应模型(System frequency response,SFR),量化系统惯量与风电渗透率的关系,给出了风电并网系统最小惯量评估方法。最后,搭建了含风电接入的4机2区域模型,对理论分析结果和评估方法进行了仿真验证。
