基于熵权法的供电商竞争力组合评价

针对单一评价方法的局限性,提出了基于熵权法的组合评价方法。该方法是对原有的单一评价方法进行组合的一种评价方法。此方法克服了单一评价方法的片面性,同时使各单一评价方法所包含的主客观性相统一。该方法首先应用多种单一评价方法对评价对象进行综合评价,而后运用关联度、最大误差、平均绝对误差三个评价指标对单一评价方法的评价效果进行评价计算,将计算结果经处理后形成多种单一评价方法的评价矩阵,利用熵权法对各单一评价方法所包含的显信息和隐性信息进行挖掘求得各单一评价方法的权重,据此构成组合评价方法。最后,应用此方法对供电商竞争力进行了实例验证。     

实现制冷的途径

制冷的方法很多，可分为物理方法和化学方法。而绝大多数的方法是物理方法。目前广泛应用的制冷方法有以下几种。     

基于熵权法的供电商竞争力组合评价

针对单一评价方法的局限性,提出了基于熵权法的组合评价方法.该方法是对原有的单一评价方法进行组合的一种评价方法.此方法克服了单一评价方法的片面性,同时使各单一评价方法所包含的主客观性相统一.该方法首先应用多种单一评价方法对评价对象进行综合评价,而后运用关联度、最大误差、平均绝对误差三个评价指标对单一评价方法的评价效果进行评价计算,将计算结果经处理后形成多种单一评价方法的评价矩阵,利用熵权法对各单一评价方法所包含的显信息和隐性信息进行挖掘求得各单一评价方法的权重,据此构成组合评价方法.最后,应用此方法对供电商竞争力进行了实例验证.     

无网格数值求解方法

无网格方法是近年发展起来的一种新的数值计算方法,根据近似函数构建方法和微分方程离散方法的不同,可以构建出许多不同的无网格方法。该文简述了无网格方法的理论基础;介绍近似函数的构建方法和微分方程的离散方法,并以移动最小二乘近似方法为例,分析了权函数和形函数的特征。分析结果显示:径向基函数和点插值法均具有δ函数属性,但计算稳定性差;移动最小二乘近似函数不具有δ函数属性,但计算比较稳定;无网格方法中的3种离散方法不同之处在于:配点法不需要积分,计算量小,计算稳定性差;Galerkin方法需要借助背景网格进行积分,它不是真正的无网格方法;Petrov-Galerkin方法,是一种真正的无网格方法,它需要对每个子域进行积分,计算工作量较大。     

电网故障诊断方法综述

介绍电网故障诊断问题的复杂性所在,并总结归纳近10多年来国内外学者在故障诊断领域提出的主要方法,包括专家系统方法、模糊集方法、数据挖掘和粗糙集方法、人工神经网络、Petri网、贝叶斯网、优化算法及信息理论方法等。说明各种方法的基本概念和方法思路,分析各种方法的特点和不足,探讨新形势下电网故障诊断技术的发展趋势。     

PLC程序设计中的定时问题

用定时器编程的方法,实现长延时、脉冲定时器的方法、交替控制的方法和高精度周期性定时的方法.     

PLC应用知识问答（7）：PLC程序设计中的定时问题

用定时器编程的方法,实现长延时、脉冲定时器的方法、交替控制的方法和高精度周期性定时的方法.     

基于ITAE指标的PID参数整定方法比较研究

时间乘以误差绝对值积分(ITAE)的性能指标是一种具有很好工程实用性和选择性的控制系统性能评价指标。该文针对具有实参数不确定性的热工对象，基于蒙特卡罗实验原理，提出了一种PID控制系统性能比较方法。该方法利用大量随机实验，研究了几种典型的PID控制器参数整定方法如：Ziegler-Nichols方法、Chien-Hrones-Reswick方法、Cohen-Coon方法、IMC方法、IST^2E最优方法、极点配置方法、幅值相位裕量方法等。所设计的PID控制系统的ITAE性能指标通过ITAE指标对参数整定方法进行分析和选择。最后通过超临界锅炉过热汽温控制的仿真实例验证了方法的有效性。     

基于码存储的SGR信号跟踪实时性提高方法

在GPS软件接收机信号跟踪过程中,为了解决传统的八通道GPS跟踪方法耗时较长,提出了一种基于码存储的SGR信号跟踪方法。本文对传统的八通道的GPS码跟踪方法进行了分析与理论介绍,基于传统跟踪方法码产生耗时较多,提出了预存码的方法,并介绍了预存码方法的原理与程序流程,最后对两种方法进行了实验测试,通过传统方法与码存储方法的比较分析与仿真实现,证明了码存储方法能够消除码产生的时间,并且输出导航信息幅值不受影响。     

改进的三维多重网格法及其工程应用

本文针对多重网格强度校核方法中的不足之处--滑面子结点应力的有限元网格依赖性,提出了相应的改进方法.改进方法把滑面网格结点作为虚拟的高斯点,其应力的计算方法与有限元中高斯点应力的计算方法相同.改进的方法在继承原方法特点的同时,比原来的方法具有更好的理论基础.数值算例分析表明改进方法中子网格结点应力的取值更为准确可靠,降...     

岩土工程稳定性分析方法研究动态及展望

本文简要介绍了岩土工程中多种稳定性分析方法 ,并对它们进行了初步的讨论。此外就地下洞室稳定性问题进行了探讨。并在此基础上论述了岩土工程稳定性分析方法的发展     

Efficiency improvements in meta-heuristic algorithms to solve the optimal power flow problem

This paper presents three efficient approaches for solving the Optimal Power Flow (OPF) problem using the meta-heuristic algorithms. Mathematically, OPF is formulated as non-linear equality and inequality constrained optimization problem. The main drawback of meta-heuristic algorithm based OPF is the excessive execution time required due to the large number of load flows/power flows needed in the solution process. The proposed efficient approaches uses the concept of incremental power flow model based on sensitivities, and lower, upper bounds of objective function values. By using these approaches, the number of load flows/power flows to be performed are substantially, resulting in the solution speed up. The original advantages of meta-heuristic algorithms, such as ability to handle complex non-linearities, discontinuities in the objective function, discrete variables handling, and multi-objective optimization, are still available in the proposed efficient approaches. The proposed OPF formulation includes the active and reactive power generation limits, Valve Point Loading (VPL) effects and Prohibited Operating Zones (POZs) of generating units. The effectiveness of proposed approaches are examined on the IEEE 30, 118 and 300 bus test systems, and the simulation results confirm the efficiency and superiority of the proposed approaches over the other meta-heuristic algorithms. The proposed efficient approaches are generic enough to use with any type of meta-heuristic algorithm based OPF.     

短期风电功率预测概念和模型与方法

随着并网风电容量的持续增加,风电强随机性给电力系统安全稳定运行带来了挑战,风电功率预测受到广泛的关注。文中较为全面地综述了国内外对风电功率预测的研究现状,着重从风电预测基本理论、风电预测方法和风电预测热点研究问题3个方面展开,主要介绍了确定性风电预测、概率性风电预测、风电爬坡事件预测、大数据和深度学习方法等方面的研究进展。     

Probabilistic Game Approaches for Network Cost Allocation

In a restructured power market, the network cost is to be allocated between multiple players utilizing the system in varying capacities. Cooperative game approaches based on Shapley value and Nucleolus provide stable models for embedded cost allocation of power networks. Varying network usage necessitates the introduction of probabilistic approaches to cooperative games. This paper proposes a variety of probabilistic cooperative game approaches. These have variably been modeled based upon the probability of existence of players, the probability of existence of coalitions, and the probability of players joining a particular coalition along with their joining in a particular sequence. Application of these approaches to power networks reflects the system usage in a more justified way. Consistent and stable results qualify the application of probabilistic cooperative game approaches for cost allocation of power networks.      

风力发电机组结构建模研究进展

基于分析力学建模、基于多体动力学建模和基于有限元法建模是3种常见的风力发电机组结构建模方法。从历史以及逻辑的角度对这3种建模方式进行了梳理,给出了各自的共同特征与发展前景,并对三者进行了系统比较,为风力发电机组结构建模提供参考。     

Transmission Outage Performance Prediction: Unit or Component Approach?

The key information required for quantitative evaluation of bulk power system reliability includes frequency and duration of multiple transmission line outages that cause system problems. Two fundamental approaches to reporting and analyzing transmission performance data to predict these multiple outages have evolved in the industry. These have been referred to as "unit" and the "component" approaches. A third approach "hybrid" has also been suggested. This paper interprets these approaches and discusses their relative advantages. Their relative accuracies are also discussed applying these approaches to Commonwealth Edison Company's 345 kV transmission outage data.     

电力系统负荷预报方法综述

评述了电力系统负荷预报传统方法和近代方法 ,指出了传统负荷预报方法存在的问题 ,介绍了负荷预报方法发展的趋势。     

Differential Game Theory Applied to a Model of the Arms Race

The arms race model of L. F. Richardson is considered within a differential game theoretic context. Five different approaches to the game are considered and the results compared. The particular model considered is a three nation arms race model which becomes a three player differential game. The five approaches to the game are the minimax, Nash, and Pareto approaches as well as two coalition approaches: C.P.O. (Coalitive Pareto Optimality) and N.C.O. (Nash Coalitive Optimality). Some suggestions are made for future research and some possible economic, social, and political implications of this work are considered.     

基于SoC规范的存储器内建自测试设计与对比分析

集成电路深亚微米工艺技术和设计技术的迅速发展使得SoC存储器的测试问题日益成为制约其技术发展的“瓶颈”。为解决SoC中存储器走线和多IP核测试等问题,本文从嵌入式核测试标准IEEE P1500出发,采用了基于该规范的专用硬件方式内建自测试的设计及实现方法,并通过与传统的存储器内建自测试结构进行比较和分析,证明了基于该规范的内建自测试方案可以在满足功耗约束下减少走线,实现多IP核测试。     

Generator maintenance scheduling in power systems using metaheuristic-based hybrid approaches

The effective maintenance scheduling of power system generators is very important for the economical and reliable operation of a power system. This represents a tough scheduling problem which continues to present a challenge for efficient optimization solution techniques. This paper presents the application of metaheuristic approaches, such as a genetic algorithm (GA), simulated annealing (SA) and their hybrid for generator maintenance scheduling (GMS) in power systems using an integer representation. This paper mainly focuses on the application of GA/SA and GA/SA/heuristic hybrid approaches. GA/SA hybrid uses the probabilistic acceptance criterion of SA within the GA framework. GA/SA/heuristic hybrid combines heuristic approaches within the GA/SA hybrid to seed the initial population. A case study is formulated in this paper as an integer programming problem using a reliability-based objective function and typical problem constraints. The implementation and performance of the metaheuristic approaches and their hybrid for the test case study are discussed. The results obtained are promising and show that the hybrid approaches are less sensitive to the variations of technique parameters and offer an effective alternative for solving the generator maintenance scheduling problem.