Optimal Load Curtailment in Bulk Power System Reliability Evaluation

This paper studies the question for considering optimal load curtailment in bulk power system adequacy evaluation. A minimization model of load curtailment is utilized for the contingency states which may have load curtailment. In order to calculate realistic bus indexes, two practical load curtailment philosophies are incorporated in the minimization model of load curtailment, which is achieved in computer program developed for bulk power system reliability evaluation. The minimization model of load curtailment, correlated algorithms, and flow chart of program are given in this paper. The effectiveness and availability of the model are verified from two case studies.     

NLPNN Model in Power Systems Reliability Evaluation

The purpose of a power system is to deliver the power the customers require in real time, on demand, within acceptable voltage and frequency limit, and in a reliable and economic manner. Using NLPNN (New Linear Programming Neural Network) model, the behavior analysis of power system under fault conditions is carried through. The stability and convergence theorems are set up to obtain the resolution for the problem of the load curtailment strategy. A new way is open up to evaluate the reliability of power systems and the great progress in calculation analysis model is achieved. The new calculation technique and theory foundation of reliability evaluation are supplied.     

Reliability Evaluation for Bulk Power System Including Dependent Outage of Transmission Line

In order to calculate and analyze the effect of two transmission lines in parallel on the reliability evaluation of bulk power system, a model including independent outage, common mode outage and dependent outage of these lines is deduced and a new algorithm corresponding to the model is presented. Two transmission lines in parallel including common mode outages and dependent outages can be really simulated as a multi-state component. While reliability indices are calculated, the probability and frequency of independent outage, common mode outage and dependent outage of a system failure state can be calculated at the same time, and computation complexity is reduced. The proposed model and algorithm are applied to the RBTS system, IEEE One Area RTS96 system and a real power system for reliability computation and analysis. Results show that the new algorithm is credible and validity.     

An Improved Learning Algorithm for BP Model and its Application to Load Forecasting in Power Systems

This paper analyses the cause of very slow learning rate during the time of ap-proaching the minim um poi nt in con vertional BP algorithm, by introducing weight factor into themodification of the connection weight,an improved leavning algorithm for BP model is presented,itcan sign ificantly in crease the learning rate and improve con vergent behaviour.As an illustrative ap-plication example,the n umeriCal resu It of the medium-term load forecasting is given.     

Reliability Evaluation of Middle Voltage Distribution Networks

A reliability evaluation algorithm for middle voltage radial distribution network is presented. The algorithm applied ahead-searching-method to determining the area of breaker influencing, applied bidirectional-searching-method to determining faulting area, and applied behind-searching-method to determining connection switch. Then the type of nodes is determined. The reliability index of nodes,feerders and system can be easily computed by the type of nodes.So the computing effeciency is improved. At the same time, the curtailing load algorithms for low-voltage of buses and over-capacity of lines are presented and the foundation for the reliability assessment is established considering the power flow restriction. From the RBTS68-bus and other middle radial distribution networks,the effectiveness and availability of the method are verified.     

Multiple Load Flow Solutions in Electric Power Systems Based on Genetic Algorithm

Methods for satisfying the power balance requirement and the voltage magnitude costraint are developed and incorporated into the genetic algorithm method to form a constrained genetic algorithm for solving the load flow problem.The robustness of the load flow algorithm is enhanced by the dynamic population.the technique for accelerating the convergence of the optimisation process and the network node sequencing procedure described in the paper.The efficiency and feasibility of the developed CGALF algorithm have been tested using KK 11 node system under light load and heavy load conditions.     

Computer Aided Decision-Making System of Power System Reliability Evaluation Based on Object-oriented

The reliability is an important component part of research fields in power system. This paper presents an application of object oriented programming to develop reliability evaluation system of electric networks. A new approach to reliability evaluation and graph expression is proposed, and a computer aided decision making system of electric network reliability evaluation using Visual C++ 5.0 under Windows95 environment is developed. The system can provide reliability data for power system operation and plan, which is the foundation for operation and decision making. It has the characteristics of better expansibility, convenient usage, user friendly interfaces and so on.     

The Application of Fuzzy Theory to Power Load Forecasting

A new method was presented for power load forecasting.Based on the fuzzyclustering technique,the historical samples of power load and its relative environmental factors wereclassified into several typical categories,the fuzzy numbers and sets were then used to describe thepatterns of load variation and the features of the environmental factors for every class. Finally,byunderstanding the state of future environmental factors, the future power load can be predictedthrough determining the category of load variation pottern. The validity of the proposed method wasverified with a practical medium-term load forecasting.     

A New Algorithm for Open Conductor Faults in Power Systems with Variable Structures

A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples.     

Reliability Evaluation Model of Composite Generation and Transmission System Incorporating FACTS Devices

The utilization of Flexible AC Transimssion System(FACTS)technology has significant impact on power system reliability performance.Series FACTS devices such as Thyristor Controlled Phase Shifting Transformers(TCPSTs) and Thyristor Controlled Series Compensators(TCSCs) can change the natural allocation of the power flow and effectively alleviate transmission congestion.Parallel FACTS devices such as Static Var Compensators(SVCs)can provide reactive power support and maintain voltage stability.So it is important to quantitatively evaluate their benefits to the power system reliability.The traditional models of the composite generation and transmission system reliability evaluation are mainly focused on conventional generation and transmission facilities.This paper researches the power flow model of TCPST and TCSC,and then presents the optimal load shedding model incorporating TCPSTs,TCSCs and SVCs and effectively incorporates them into the reliability evaluation model.The proposed method is tested on the RBTS and the obtained results show that the system reliability can be improved effectually by FACTS devices.     

Content-aware Load Balancing Strategy in Web Cluster System

The capacity problem of web server can be solved by web cluster technology. The key point is load balancing strategy and algorithm. Traditional slrategies are effective to some kinds of web sites, but not suitable for all. The paper analyses the load characters of different kind of web sites. A content-aware web cluster load balancing strategy and algorithm is proposed. The efficiency will be evaluated through emulation experiments.     

An Improved Method of the Transient Waveform Analysis in Power Systems

The angular frequency and decaying constant of each copmonect for the transient waveform in power systems were obtained by using the discrete Fourier transform; the amplitude and phase angle were calculated in the linear curve fitting method. And all of the parameters obtained above were treated in an unified optimization by using the curve fitting optimization of the least square method of general nonlinear funcrion so as to get the results of waveform analysis. Two examples are included.     

Reliability evaluation algorithm for complex electrical distribution networks using the storage structure of adjacency multilist

A section algorithm of reliability evaluation for complex medium voltage Electrical Distribution Networks (EDNs) using adjacency multilist (AM) is proposed. The constructing method for AM is introduced. The AM can be used to store the structure data of EDNs and to solve the problem of space & time complexity. A new power flow algorithm of backward / forward sweep is proposed and a fast algorithm of forming sections in distribution network is put forward. The proposed algorithm makes a perfect combination of the power flow algorithm and the section algorithm of reliability evaluation, which makes efforts to decrease the work of programming and saves the computing time. Applying the proposed algorithm in RBTS-BUS6 system and actual EDNs, the reliability assessment results show that the algorithm has an advantage of saving time and possesses efficiency in engineering practicality.     

A New Method of Piece-Wise Solution in Faulted Power Systems with Variable Configurations

A new model and its algorithm are presented in this paper to simulate calculating the electric values of short circuit fault in large-scale power systems with variable configurations. The method proposed herein reduces the computer storage requirements compared with the available approaches. And it completely avoids the modification computation of nodal impedance (or admittance) matrices of the original networks and the repeated calculations for each type of faults.     

Application of Combination Grey Model in Power Load Forecasting

Based on the gray forecast theory, this paper studies the principle and deficiency in power load forecasting by the basic grey model and other improved models, and introduces a new method -the combination grey model to forecast the long-medium power load. Based on an example, the basic grey model, other improved models and combination grey model are used to forecast power load and results of all models are analyzed and compared. The calculation results show that forecasting power load by grey theory is credible and simple. For this type of complex problems such as forecasting the long-medium power load, the combination grey model is specially useful because of it's high precision and facility. The method can be used as one of the tools of forecasting the long-medium power load.     

Reliability Analysis of Human-Machine System in Continuous Industry

As the research objective changing from a small simple system to a large complex one, traditional reliability theory can not adapt to the requirement of the great transformation. Based on the specialty of continuous process industry, the necessity and urgency to study the reliability of this kind of system is stated out. The research structural model of the reliability of complex continuous industries is presented also which involved in the reliability of human, network, software and devices.     

Fuzzy Optimization for Reliability Apportionment of Series system

This paper points out that there are many factors which affect the reliability optimization apportionment of the series system which is in nature a problem of fuzzy optimization. In the light of this paper puts foreword a method for the reliability apportionment of the series system. Moreover, it is discussed with fuzzy optimization apportionment of the system reliability under the conditions of given source constraints.