Reliability indices for electric-power wheeling

Transmission networks are being used more extensively to accommodate energy transactions that use the economic benefits of pooling. This paper evaluates the probabilistic wheeling capability of an interconnected power transmission system. Large electric power wheeling can degrade the reliability of the electric power network. This problem is also important for power system control and planning purposes. This paper discusses, from the viewpoint of power network reliability, the problem of power wheeling from Western Europe to Greece through the Yugoslav electric power system. The relative cost of the wheeling due to reliability indices is 2% of the production cost for the power wheeled. The calculation of reliability indices of wheeling enable more adequate estimation of the wheeling rate for power transactions between utilities. This paper describes an approach to calculate cost of the average energy not supplied and load curtailed due to wheeling. This cost can even be negative, which depends mostly on the amount of wheeling power and consumer loads. The reliability index EENS (expected energy not supplied) is more comprehensive than PI (performance index) for the contingency severity selection procedure     

A low-cost cellular mobile communication system: a hierarchicaloptimization network resource planning approach

This paper deals with the optimization of the design and radio network resource planning for cellular mobile communication systems. The key element to be considered for mobile network planning is cost. A hierarchical optimization planning method (HOP) is utilized since there are so many factors like system performance, terrain features, base station parameters, and cost factors which are involved in the large-scale system design. We present a three-level optimization approach for designing a cellular mobile system. It determines the cell number, cell site allocation, and the specific base station parameters in order to minimize the total system cost and to comply with the required system performance. The problem is formulated as a large combinatorial optimization model which can determine the optimal number of cells and select the best base stations' locations. The simulated annealing approach is developed to solve the hard combinatorial problem. Simulation results demonstrate the feasibility and effectiveness of the HOP approach for radio network planning     

Optimal design improving a communication network reliability

Improvement of the reliability of a communication network is an optimal problem that finds some links to add to the network such that the reliability of the network reaches a given level and the total cost of these links is minimized. A decomposition method based on branch and bound is used for solving the problem. In order to speed up the solution procedure, an upper bound on system reliability in terms of node degrees is applied. Specially, when the threshold P_o is large enough, a new algorithm, the cut tree algorithm, can more effectively give the optimal solution.     

Reliability optimization of computer-communication networks

The evaluation of the reliability of a given computer communication network is a NP-hard problem. Hence, the problem of assigning reliabilities to links of a fixed computer communication network topology to optimize the system reliability is also NP-hard. A heuristic method is developed to assign links to a given topology so that the system reliability of the network is near optimal. The method provides a way to assign reliability measures to the links of a network to increase overall reliability. It is based on the principle that the most reliable link should be assigned to the most vulnerable edge. The method computes an importance order for the edges of the network and uses the order to assign link reliabilities. If there are fewer than six links in a network, it can be shown that the method gives optimal assignment     

基于列生成的毫米波多连接链路配置调度算法

多连接技术允许用户同时建立和保持与多个小区/接入点的连接,通过网络元素之间的协调在吞吐量和可靠性方面大幅提高网络性能。针对毫米波通信中超高频段的链路中断问题,研究了多连接基于链路配置的调度算法,以提高链路调度效率,降低复杂度。首先,在系统模型中采用链路配置作为优化变量;其次,设计了多连接比例公平的调度准则;最后,提出一种基于列生成算法的链路配置调度优化算法,利用Dantzig-Wolfe分解将原问题分解为限制主问题和定价问题,并结合分支定界方法获得最优解。仿真结果表明,所提算法能够在数值上逼近全局最优,并且比现有的毫米波蜂窝网络链路调度方案增益平均提高40%以上。     

面向多层次、多指标的光网络规划与评估方法

首先深入分析了影响业务可靠性的关键指标,并建立了面向可靠性和建设成本的网络规划模型,然后设计了自适应免疫算法以求解网络规划方案。进而,建立了面向多层次、多指标的网络规划方案评估模型,并使用神经网络算法获得指标权重,实现对网络规划方案的全面、有效评估。通过仿真可知,提出的面向多层次、多指标的光网络规划与评估方法能够提高光缆资源利用率和站点成环率、降低网络建设成本以及保障网络可靠性,有助于提高运维人员的工作效率和运维水平。     

基于Google Earth的无人机中继布局优化软件

建立了一个无人机作为中继的通信网络系统,并通过对中继链路和高空中继覆盖区域进行几何建模,推导获得了无人机在一定飞行高度的信号覆盖区域。在此基础上,基于Google Earth和Visual C++6.0软件平台,开发了一套无人机中继系统可视化网络优化软件。测试结果表明,该软件操作简便且运行稳定,能够实现无人机的静态最优布置与动态飞行路径规划,对于解决网络节点高速和大范围移动导致的网络中断问题,具有重要的工程应用价值。     

Reliability modeling for expansion-planning of electric-powerplants

The author presents a simple analytic approach for solving the problem of expansion planning of electric power plants. The relationship between the long-range generation investment and the plant size is studied to determine generation capacity. The reliability level, as an important limiting factor of the expansion planning process, is discussed and the corresponding systems costs are determined based on the reliability specification. The stochastic behavior of each plant is represented using a six-state model. The reliability level of the generation system is evaluated using a recursive convolution of the weekly load duration curve with the stochastic availability of the generating units. Central to the reliability calculation is the selection of the unit size; the relationships between plant size and the corresponding investment and production cost are calculated for each expansion alternative. The techniques are also applied to a practical power system and a comparative study is used to select the optimal plant size     

Optimal Design of a Series-Parallel System with Time-Dependent Reliability

The paper formulates an optimal reliability design problem for a series system made of parallel redundant subsystems. The variables for optimization are the number of redundant units in each subsystem and the reliability of each unit. There is a cost-constraint. The time for which the system reliability exceeds a specified value is to be maximized. Similarly the cost could be minimized for a constraint on the mission time and reliability. A solution method for the formulated problems is presented along with an example.     

基于复合量度的电力光纤多电路配置可靠性

能源互联网的一个本质特征是通过先进的通信网络实现能源供给与消费间的双向互动。以光纤通信为基础的高可靠通信网络优化配置以满足多业务的服务质量(QoS)需求成为亟需解决的关键问题。从电力光纤传输网络的可靠性入手,并考虑电力通信业务的多QoS传输需求,设计一种基于复合量度的电路配置优化方法。有别于传统最短路配置算法,新方法在一次配置过程中同时规划m条可行配置方案,并且通过分析路径集的带宽、时延、丢包率、衰耗和成本等不同量度和光路全程可靠性,最终获得满足可靠性和传输QoS需求的光路配置方案,并给出优先选择序列。多电路优化配置将有效提升电力通信的可靠性,也可为未来多路流量分摊提供电路配置保证。通过某城区35~500 kV电力通信站网实例仿真计算,新配置方法能够一次获取4条同时满足业务多QoS需求的传输电路,实现主备电路保护。对电力光纤传输网络的规划和运行优化,提高电力通信网的资源调配能力和可靠性提供参考。     

Optimization of connecting two communication networks subject to a reliability constraint

This paper considers optimization of two networks with a reliability constraint. The objective is to find some links to connect two networks, at a minimal cost, under the constraint that the system reliability of the resultant network is not less than a given level. A decomposition method based on branch and bound is used for solving the problem. In order to speed up the solution procedure, an upper bound on system reliability in terms of node degrees is applied. In particular, when the threshold P_o is large enough, a new algorithm, the cut tree algorithm, can more effectively give an optimal solution.     

Reliability analysis of industrial power systems with sensitive loads

A method for the reliability analysis of power system has been developed that includes the behaviour of the system during a disturbance. The power system is modelled as an electrical network in which branches are removed and inserted by stochastic events, generated by a Monte Carlo simulation. This method considers short circuits followed by an interruption of the protection, in stead of just the removal of a component. By using a maximum-permissable voltage sag as an interruption criterion the method can be used for industrial power systems with sensitive loads. The (correct and incorrect) behaviour of the protection, ageing of components, and the influence of preventive maintenance are also included in the method.An example of the use of the method is given: a power system feeding four industrial plants. The influence of plant voltage solidity and of preventive maintenance in the feeding network are investigated. Both turn out to have considerable influence.     

The use of game theory to measure the vulnerability of stochastic networks

Conventional approaches to network reliability analysis are based on either connectivity or capacity. This paper proposes an alternative method which seeks to identify those links or nodes whose failure would impair network performance the most. It is assumed that all links have two costs, a normal cost and a failed cost, both of which can be traffic-dependent. A 2-player, noncooperative, zero-sum game is envisaged between a router, seeking a least-cost path, and a virtual network tester, seeking to maximize trip-cost by failing 1 link. At the mixed strategy Nash equilibrium, link-use probabilities are optimal for the router, and link-failure probabilities are optimal for the tester. Finding the equilibrium involves solving a maximin programming problem. When link costs are fixed (not traffic-dependent), the maximin problem can be recast as a linear programming problem. Two forms of the linear programming problem are presented, one requiring path enumeration, and the other not. The interpretation of the primal and dual variables is elucidated by two propositions. Where link costs are traffic-dependent (e.g., where queuing is a feature), the mixed strategy Nash equilibrium can be found by the VISA (method of successive averages). A numerical example illustrates the approach on a stochastic network with queuing. While the example relates to single commodity e.g., where there are multiple origins and destinations.     

随机需求下的多阶段供应链库存问题研究

多阶段库存问题是供应链研究的重要课题，随着供应链思想的发展，控制各个存储环节的成本是整个供应链降低成本及规避风险的有效方法，对这一问题的解决方法主要有2种：(1)在分散决策下应用单阶段方法依次求优；(2)销售需求计划(类似MRP)。这两种方法适用于不同的企业环境，本文采用了第一种方法。产品需求数量的不确定性是多阶段库存和分销系统难以实施优化的主要原因之一．本文研究的是一个批发商，Ⅳ个零售商的销售系统，批发商对零售商的订单采取的是先到先服务机制。通过将各个水平的需求依据其概率特性进行随机的描述，然后运用单阶段的方法对其优化，进而得出各个阶段的最优库存。     

Service function chain construct algorithm based on reliability

With the continuous expansion of network size and content quantity,network operators often face the problem of data transmission interruption,thus how to improve the reliability of data transmission has become a research hotspot.Started with the huge advantages of NFV environment over traditional TCP/IP architecture based on the background that every network node has the capability of security service,a reliability algorithm for constructing functional service chains was proposed.First,the network topology was introduced and abstracted it into a digraph for a better analyzation.Then,several quantitative indices were used to define the upper and lower bounds of failure probability and resolved the model through a heuristic algorithm.The experimental results show that the proposed algorithm increases the reliability of service chain selection and spends less time.     

Directional Sensor Placement with Optimal Sensing Range,Field of View and Orientation

This paper introduces a new wireless sensor network planning problem referred to as the Optimal Sensor Configuration (OSC) problem. In this problem, the goal is to find an optimal subset of locations where directional sensors and base stations are installed in order to minimize the total network cost while satisfying the requirements of coverage and connectivity. This goal is achieved by appropriately choosing the base station type and configuring each sensor to be installed in the sensor field. The optimal configuration of each sensor is determined by three parameters which are sensing range, field of view and orientation. The paper also gives an integer linear programming formulation of the OSC problem. The viability and effectiveness of the proposed formulation are illustrated through numerical results.     

ATC ground communications system optimization techniques

The authors address the optimization of three major components of the US Federal Aviation Administration's (FAA's) hybrid leased/owned ground communications system supporting air traffic control (ATC). The optimizations are performed with respect to cost, performance, and reliability. First, optimization of the radio communications link (RCL) backbone microwave transmission system is discussed. A heuristic optimization procedure that minimizes cost subject to capital cost and availability constraints is presented. Second, two levels of user access network (UAN) optimization are discussed. The first level is optimization of the selection of RCL sites to open as drop-and-insert points for access by private leased-line UANs. The second level is optimization of the selection of transmission media used for implementing UANs. A dynamic programming method is presented for identifying FAA facilities where low-density microwave UANs are cost-effective. Third, optimization of the National Airspace Data Interchange Network (NADIN) II packet data switching system is discussed. Because this network will use the FAA-owned RCL transmission resources, the primary measures for optimization are performance and reliability instead of cost. Two methods are presented for this problem: an analytic method and a simulation method     

Topological optimization of a communication network subject to areliability constraint

Network topological optimization with a reliability constraint is considered. The objective is to find the topological layout of links, at a minimal cost, under the constraint that the network reliability is not less than a given level of system reliability. A decomposition method, based on branch and bound, is used for solving the problem. In order to speed up the procedure, an upper bound on system reliability, in terms of node degrees, is applied. A numerical example illustrates the effectiveness of the method     

Solving the Redundancy Allocation Problem With a Mix of Components Using the Improved Surrogate Constraint Method

When designing a system, there are two methods that can be used to improve the system's reliability without changing the nature of the system: 1) using more reliable components, and/or 2) providing redundant components within the system. The redundancy allocation problem attempts to find the appropriate mix of components & redundancies within a system in order to either minimize cost subject to a minimum level of reliability, or maximize reliability subject to a maximum cost and weight. Redundancy allocation problems can be classified into two groups; one allows the system to have a mix of components with different characteristics incorporated in the system, while the other only allows one type of each component. The former group has a much larger solution space compared to the latter, and therefore obtaining an exact optimal or even a high quality solution for this problem may be more difficult. Optimization techniques, based on meta-heuristic approaches, have recently been proposed to solve the redundancy allocation problem with a mix of components. However, an exact solution method has not been developed. In this paper, we develop an exact solution method, based on the improved surrogate constraint (ISC) method, and use this method to find optimal solutions to problems previously presented in the literature     

Topological layout of links for optimising the overall reliability in a computer communication system

Overall reliability or global availability is an important parameter in the design of the large scale computer communication systems having efficient resource sharing amongst the various computer centres. In order to design an optimal topological layout of the various links connected between the set of various geographically-distant computers, one should have knowledge of the cost and reliability of all the possible links and the maximum permissible cost. In this paper a heuristic algorithm is presented for obtaining an optimal network topology which gives the maximum overall reliability of the computer communication network. The method is general and is easily implemented on a computer.