Load Distribution of Base Stations in User-Centric Heterogeneous UDN

In ultra-dense networks(UDN),multiple association can be regarded as a user-centric pattern in which a user can be served by multiple base stations(BSs).The data rate and quality of service can be improved.However,BSs in user-centric paradigm are required to serve more users due to this multiple association scheme.The improvement of system performance may be limited by the improving load of BSs.In this letter,we develope an analytical framework for the load distribution of BSs in heterogeneous user-centric UDN.Based on open loop power control(OLPC),a user-centric scheme is considered in which the clustered serving BSs can provide given signal to interference plus noise ratio(SINR)for any typical user.As for any BS in different tiers,by leveraging stochastic geometry,we derive the Probability Mass Function(PMF)of the number of the served users,the Cumulative Distribution Function(CDF)of total power consumption,and the CDF bounds of downlink sum data rate.The accuracy of the theoretical analysis is validated by numerical simulations,and the effect the system parameters on the load of BSs is also presented.

THEORETICAL INVESTIGATION ON STATE OF LOAD DISTRIBUTION AMONG CONTACT BEARINGS OF DOUBLE CIRCULAR ARC HELICAL GEARS

A dynamic analysis approcach to investigate the state of load distribution among contact bearings of double circular are belical gears is proposed and a computer program is developed for calculating the factor of iced distribution based on the theory of W-N gears. The changing situations of load distribution among contact bearings of the gears influenced by main issues are analyzed by a series of parametric studies.

An Improved Differential Evolution Whale Algorithm for Economic Load Distribution

An improved optimization algorithm combining the differential evolution algorithm and the whale algorithm is proposed for the problem of not being able to get rid of the local optimum in the economic load distribution algorithm. The algorithm adopts a nonlinear convergence strategy, a crossover strategy of differential evolution and the introduction of an elimination mechanism, which balances the global search and local exploitation ability of the algorithm and improves the accuracy of the solved optimal solution. The 13-unit and 40-unit systems are selected for economic load distribution calculation, and the experimental results show that the proposed improved algorithm is superior in distributing the economic load of the power system and can effectively reduce the economic cost.

Load distribution strategy for multi-lift system with helicopters based on power consumption and robust adaptive game control

It is of great significance to reasonably distribute the slung load to each helicopter while considering difference in power consumption,relative position and interaction comprehensively.Therefore,the load distribution strategy based on power consumption and robust adaptive game control is proposed in this paper.The study is on a"2-lead"multi-lift system of four tandem heli-copters carrying a load cooperatively.First,based on the hierarchical control,the load distribution problem is divided into two parts:the calculation of expected cable force and the calculation of the anti-disturbance cable force.Then,aimed at minimizing the maximum equivalent power of heli-copter,an optimization problem is set up to calculate the expected cable force.Specially,the agent power model is trained by BP neural network,the safe distance constraint between helicopters is set to 2.5 rotor diameters to reduce aerodynamic interference,and the helicopters with different perfor-mance can be considered by introducing the equivalent power factor into the objective function.Next,considering the difference and interaction between helicopters,the robust adaptive differen-tial game control is proposed to calculate the anti-disturbance cable force.Particularly,to solve the coupled Hamiltonian equations,an adaptive solving method for value function is proposed,and its stability is proved in the sense of Lyapunov.The simulation results indicate that the proposed load distribution method based on power consumption is applicable to the entire flight trajectory even there are differences between helicopters.The game control can consider interaction between heli-copters,can deal with different objective functions,and has strong robustness and small steady-state error.Based on the entire strategy,the cable force can be reasonably allocated so as to resist disturbance and improve the flight performance of the whole system.

Electric Vehicle Charging Capacity of Distribution Network Considering Conventional Load Composition

At present,the large-scale access to electric vehicles(EVs)is exerting considerable pressure on the distribution network.Hence,it is particularly important to analyze the capacity of the distribution network to accommodate EVs.To this end,we propose a method for analyzing the EV capacity of the distribution network by considering the composition of the conventional load.First,the analysis and pretreatment methods for the distribution network architecture and conventional load are proposed.Second,the charging behavior of an EVis simulated by combining the Monte Carlo method and the trip chain theory.After obtaining the temporal and spatial distribution of the EV charging load,themethod of distribution according to the proportion of the same type of conventional load among the nodes is adopted to integrate the EV charging load with the conventional load of the distribution network.By adjusting the EV ownership,the EV capacity in the distribution network is analyzed and solved on the basis of the following indices:node voltage,branch current,and transformer capacity.Finally,by considering the 10-kV distribution network in some areas of an actual city as an example,we show that the proposed analysis method can obtain a more reasonable number of EVs to be accommodated in the distribution network.

A novel approach to the dynamic response analysis of Euler-Bernoulli beams resting on a Winkler soil model and subjected to impact loads

This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less importance in controlling the maximum response to impulsive loadings because the maximum response is reached in a very short time,before the damping forces can dissipate a significant portion of the energy input into the system.The development of two sine series solutions,relating to different types of impulsive loadings,one involving a single concentrated force and the other a distributed line load,are presented.This study revealed that when a simply supported Euler-Bernoulli beam,resting on a Winkler soil model,is subject to an impact load,the resulting vertical displacements,bending moments and shear forces produced along the span of the beam are considerably affected.In particular,the quantification of this effect is best observed,relative to the corresponding static solution,via an amplification factor.The computed impact amplification factors,for the sub-grade moduli used in this study,were in magnitude greater than 2,thus confirming the multiple-degree-of-freedom nature of the problem.

Numerical Investigation of the Load Distribution between the Main Blade and the Splitter Blade in a High-Loading Centrifugal Compressor

In the traditional design of the centrifugal compressor,the splitter blade and the main blade always keep the same shape.However,to enable high efficiency of the high-loading centrifugal compressor,the matching of design parameters of the splitter blade and the main blade needs to be optimized.In this paper,the influence of the load distribution between the main blade and the splitter blade on the aerodynamic performance,the flow field,and the internal vortices of a high-loading centrifugal compressor were studied by means of CFD prediction.Four cases with different values of the variable CR which is defined as the load-ratio of splitter blade to main blade were set up.In each case,the splitter blade and the main blade were shaped according to different laws of circulation distribution(_(r)V_(u))while the average circulation of the splitter blade and the main blade at any meridional position were consistent with that of the prototype.The results showed that a proper reduction of the load-ratio of splitter blade to main blade is beneficial to suppress the leakage vortex of the splitter blade and reduce the scale of the wake in the channel near the suction-side of the splitter blade,which consequently improves the flow uniformity at the impeller outlet and enhances the aerodynamic performance of both the stage and the component.The stage isentropic efficiency of the optimal case was found to be 0.7%higher than that of the prototype and the stage total pressure ratio was also improved.The optimal value of CR,which in this investigation is 94%,is supposed to be the result of the trade-off between the development of the wake and the leakage vortices in adjacent two channels.The optimization of the load distribution between the main blade and the splitter blade provides an opportunity to further improve the high-loading centrifugal compressor performance.

Load Distribution on the Hull-Leg Connection Components of a Jack-Up

The jacking pinions and rack chocks of the fixation system of a jack-up sustain tremendous load in the elevated condition, especially when there exists a remarkable non-uniformity of the load distribution. Failures of these structural components may lead to disastrous consequence of the jack-up. Despite the importance of these components, it is difficult to give an accurate prediction of the load distribution on these components in engineering application due to the complex nonlinear interaction mechanism, which is influenced by the relative stiffness of the components, leg-guide clearance and backlash. Previous studies mainly focus on the global performance of the jack-up and pay little attention to the load distribution on the pinions and chocks. The strength of the jacking system is often guaranteed by the manufacturer for an estimate load level, which brings in uncertainty to the safety of the jack-up. The characteristics of the hull-leg interaction are discussed in this paper, and a simplified method using gap elements is proposed. The nonlinear structural analyses are carried out for a specific jack-up using the proposed method and the three-dimensional finite element method(FEM) with contact algorithm. The proposed method is proved accurate and effective for the engineering application. The characteristics of the load distribution of the specific jack-up are discussed, and the conclusions are presented.

Adaptive Load Balancing for Parameter Servers in Distributed Machine Learning over Heterogeneous Networks

In distributed machine learning(DML)based on the parameter server(PS)architecture,unbalanced communication load distribution of PSs will lead to a significant slowdown of model synchronization in heterogeneous networks due to low utilization of bandwidth.To address this problem,a network-aware adaptive PS load distribution scheme is proposed,which accelerates model synchronization by proactively adjusting the communication load on PSs according to network states.We evaluate the proposed scheme on MXNet,known as a realworld distributed training platform,and results show that our scheme achieves up to 2.68 times speed-up of model training in the dynamic and heterogeneous network environment.

基于KL散度距离处理风电不确定性的负荷恢复分布鲁棒优化

在构建以新能源为主体的新型电力系统的背景下,在恢复控制过程中积极利用新能源并充分应对其对运行安全带来的潜在风险对于减小停电损失具有重要意义。首先,为了表征风电出力的不确定性,采用KL散度(Kullback-Leibler)距离作为筛选极端风电出力场景的控制条件,并据此构建模糊集作为风电出力典型场景。在满足相关运行安全约束的前提下,建立了以最大化加权负荷恢复量为优化目标的分布鲁棒优化模型以制定计及风电的负荷恢复方案。经松弛处理和对偶转换所得到的混合整数二阶锥模型可调用商业求解器求解。以接入规模风电场的IEEE 10机39母线系统为例进行仿真,结果表明:相比于传统的鲁棒优化方法,该方法降低了优化结果的保守性,有助于加快负荷恢复,减小停电损失。

考虑生物质能和农业柔性负荷的农业产业园区综合能源系统规划方法

农业产业园区规划是实现农业产业园区用能低碳灵活的基础,而生物质资源高值化利用和农业柔性负荷对于促进农业产业园区的合理规划十分重要。因此,该文提出了一种考虑生物质能和农业柔性负荷的农业产业园区综合能源系统(integrated energy system,IES)规划方法。首先,为实现秸秆高值化利用,引入热解气化炉生产生物质气和生物炭,并通过高厌氧发酵粪污制沼,实现生物质的充分利用。其次,引入农作物日积温作为确定种植业热负荷参与需求响应量的衡量指标,并结合农业负荷特性建立农业柔性负荷模型。然后,以园区投资运行总成本最小为优化目标,考虑设备投资约束和满足农业生长需求的农业用能约束及生物质能成本等运行约束,建立农业产业园区规划模型。随后,为减小天气概率分布不确定性对农业生产和园区供能的影响,基于历史天气数据生成盒式不确定性集合,构建农业产业园区IES分布鲁棒优化模型。最后,通过算例结果分析得出,该文所提的农业产业园区IES规划方法可以显著减少碳排放和系统总成本,并充分利用生物质资源。

基于分布鲁棒优化的广义共享储能容量配置方法

共享储能通过储能资源的复用,能有效应对高成本和利用率低的难题。迅速发展的需求侧资源在共享储能中具有潜在应用,但其不确定性问题亟待解决。文中引入了电动汽车和温控负荷的虚拟储能模型,结合实体储能,建立了考虑不确定性的广义共享储能模型和相应的优化算法,以确定实体储能的最佳容量配置。共享储能运营商根据用户需求,实现多类型储能的优化配置,并设计虚拟储能持有者的满意度补偿,以保障其用户体验和经济利益。此外,采用Wasserstein距离描述电动汽车和温控负荷的不确定性,并结合基于风险价值的分布鲁棒机会约束算法进行求解。算例结果表明,采用广义共享储能模型和分布鲁棒机会优化算法,能够充分考虑不确定性,有效降低用户的能源消费成本和运营商的储能配置成本。

Analysis of overload-based cascading failure in multilayer spatial networks

Many complex networks in real life are embedded in space and most infrastructure networks are interdependent,such as the power system and the transport network.In this paper,we construct two cascading failure models on the multilayer spatial network.In our research,the distance l between nodes within the layer obeys the exponential distribution P(l)~exp(-l/ζ),and the length r of dependency link between layers is defined according to node position.An entropy approach is applied to analyze the spatial network structure and reflect the difference degree between nodes.Two metrics,namely dynamic network size and dynamic network entropy,are proposed to evaluate the spatial network robustness and stability.During the cascading failure process,the spatial network evolution is analyzed,and the numbers of failure nodes caused by different reasons are also counted,respectively.Besides,we discuss the factors affecting network robustness.Simulations demonstrate that the larger the values of average degree<k>,the stronger the network robustness.As the length r decreases,the network performs better.When the probability p is small,asζdecreases,the network robustness becomes more reliable.When p is large,the network robustness manifests better performance asζincreases.These results provide insight into enhancing the robustness,maintaining the stability,and adjusting the difference degree between nodes of the embedded spatiality systems.

Cascading failures of overload behaviors using a new coupled network model between edges

With the development of network science,the coupling between networks has become the focus of complex network research.However,previous studies mainly focused on the coupling between nodes,while ignored the coupling between edges.We propose a novel cascading failure model of two-layer networks.The model considers the different loads and capacities of edges,as well as the elastic and coupling relationship between edges.In addition,a more flexible load-capacity strategy is adopted to verify the model.The simulation results show that the model is feasible.Different networks have different behaviors for the same parameters.By changing the load parameters,capacity parameters,overload parameters,and distribution parameters reasonably,the robustness of the model can be significantly improved.

计及精细化氢能利用的综合能源系统多时间尺度鲁棒优化策略

能源结构改革背景下,构建以氢能驱动、电-热为主体的综合能源系统(HEH-IES)具有重要意义。为提高含电氢耦合单元的IES运行灵活性,同时减小功率波动对系统的影响,提出含多元储能与综合需求响应的氢能精细化利用两阶段调度方法。首先,分析电制氢(P2H)两阶段运行过程与电氢耦合单元运行特性,对氢能的用能过程与设备进行精细化建模;其次,计及多元储能与综合需求响应提出了日前-日内两阶段多时间尺度优化策略,日前阶段充分考虑能源系统的不确定性,构建数据驱动的分布鲁棒优化(DRO)模型,日内阶段遵从日前计划,考虑多能流在灵活性调节时间尺度上的差异,通过多时间尺度的滚动优化降低功率波动的影响;最后,仿真算例证明了所提模型与策略对提升IES的运行灵活性具有积极作用。

考虑燃料电池汽车加氢负荷的电-氢系统协同优化运行

在建设新型电力系统背景下,为提高能源利用率,降低交通系统碳排放,促进配电网与交通网络融合,考虑燃料电池汽车加氢行为影响下负荷时空分布特性,构建计及燃料电池汽车交通流量与加氢行为的优化调度模型。首先,采用起止点对刻画燃料电池汽车交通流量模型,为模拟燃料电池汽车出行,采用Dijkstra算法搭建燃料电池汽车最短加氢路径模型。其次,针对可再生能源出力不确定性,基于Wasserstein距离建立风电功率预测误差模糊集,考虑电力-交通网络约束,并构建含加氢站优化调度的分布鲁棒优化模型。最后,利用强对偶理论将分布鲁棒优化模型转化为混合整数线性规划模型进行求解,采用改进的33节点配电网和24节点交通网对调度方法进行验证。结果表明,所提方法相比于鲁棒优化系统总成本有所降低,加氢站调度方案在保守和乐观之间达到平衡,实现加氢站与上级网络之间良性互动。

An optimization-oriented modeling approach using input convex neural networks and its application on optimal chiller loading

Optimization for the multi-chiller system is an indispensable approach for the operation of highly efficient chiller plants.The optima obtained by model-based optimization algorithms are dependent on precise and solvable objective functions.The classical neural networks cannot provide convex input-output mappings despite capturing impressive nonlinear fitting capabilities,resulting in a reduction in the robustness of model-based optimization.In this paper,we leverage the input convex neural networks(ICNN)to identify the chiller model to construct a convex mapping between control variables and the objective function,which enables the NN-based OCL as a convex optimization problem and apply it to multi-chiller optimization for optimal chiller loading(OCL).Approximation performances are evaluated through a four-model comparison based on an experimental data set,and the statistical results show that,on the premise of retaining prior convexities,the proposed model depicts excellent approximation power for the data set,especially the unseen data.Finally,the ICNN model is applied to a typical OCL problem for a multi-chiller system and combined with three types of optimization strategies.Compared with conventional and meta-heuristic methods,the numerical results suggest that the gradient-based BFGS algorithm provides better energy-saving ratios facing consecutive cooling load inputs and an impressive convergence speed.

省间-省内两级市场协调下两阶段分布鲁棒经济调度模型

为促进全国范围内资源优化配置,我国积极开展跨省电力交易,并将逐步形成省间-省内两级电力市场运作的模式.在此背景下,提出一种考虑省间-省内两级市场协调运行的日前-日内两阶段经济调度框架.在日前调度阶段,构建省间-省内双层日前经济调度模型;在日内调度阶段,建立考虑源-荷预测偏差的日内经济调度模型.进一步,为应对源-荷预测偏差不确定性对经济调度的影响,提出日前-日内两阶段分布鲁棒优化模型及其求解方法,实现随机场景模糊集表征下日前-日内两阶段经济调度.最后,利用IEEE 39节点和118节点系统构建多送端-多受端互联的测试系统,利用算例仿真验证了所提模型及方法的有效性.

计及源荷时序特性的低压台区分布式光伏接入分布鲁棒优化方法

为提高低压配电台区中分布式光伏(DPV)的接入容量,促进光伏消纳,本文提出一种计及源荷时序特性的低压台区DPV接入分布鲁棒优化方法.首先,针对低压台区中分布式光伏出力和负荷需求的不确定性,提出一种基于优化聚类的源-荷联合时序场景生成方法;其次,计及电压约束、线路容量约束、逆变器无功补偿约束及光伏消纳约束等,构建低压台区分布式光伏接入分布鲁棒优化模型,在保证各典型场景最恶劣概率分布下的弃光率期望值符合要求的情况下,最大化低压台区中分布式光伏接入容量;然后,建立低压台区分布式储能接入的数学模型,以研究储能接入及其充放电机制对低压台区分布式光伏接入的影响;最后,以实际配电台区为例进行仿真计算,验证了本文模型的有效性.

Experimental investigation on dynamic response and damage models of circular RC columns subjected to underwater explosions

Reinforced concrete(RC) columns are widely used as supporting structures for high-piled wharfs.The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharfs antiknock security.In this study,the dynamic response and damage model of circular RC columns subjected to underwater explosions were investigated by means of scaled-down experiment models.Experiments were carried out in a 10.0 m diameter tank with the water depth of 2.25 m,under different explosive quantities(0.025 kg-1.6 kg),stand-off distances(0.0 m-7.0 m),and detonation depths(0.25 m-2.0 m).The shock wave load and dynamic response of experiment models were measured by configuring sensors of pressure,acceleration,strain,and displacement.Then,the load distribution characteristics,time history of test data,and damage models related to present conditions were obtained and discussed.Three damage models,including bending failure,bending-shear failure and punching failure,were identified.In addition,the experie nce model of shock wave loads on the surface of a RC column was proposed for engineering application.