Qingfen Liao

Multi-level Fuzzy Comprehensive Evaluation of Power Supply Service Quality

Quantitatively evaluating the service quality of power supply is significant in electricity market, and it is beneficial to improve service quality. This paper proposed an applicable method to assess service quality with four grades based on fuzzy set theory. Considering the attributes and main factors that influence service quality, a two-level evaluation index system was set up. It is effective to determine the weights of each factor with Fuzzy Analytic Hierarchy Process (FAHP), which is easier than AHP in verifying the consistency of judgment matrix. At the same time, the paper carried out fuzzy evaluation of single factor and fuzzy comprehensive evaluation. Calculation results of actual example show that the proposed fuzzy comprehensive evaluation method is effective to distinguish service quality level.

Study on the Electrical Power Fault Recorder Integrated Analysis & Application System

This paper introduces an electric power fault recorder integrated analyzing & application system, which interconnects digital fault recorders of several substations and power houses that are widespread in Jiangxi province of China and has the fault information gathered, processed, transmitted, shared and utilized automatically and effectively. A method based on the Newton iterative algorithm for precise fault data analysis was introduced into this system. In addition to realize the conventional analysis functions that are provided by similar systems, this system realizes extended functions of flexible protection action judgment. Besides, functions of formula editor and protective relaying testing simulation have been added and provide a novel approach for the comprehensive fault analysis applications. This system is now running steadily at the dispatch center of Jiangxi Province. The good results obtained reveal the superiority and effectiveness of this system.

Parameter Identification of Excitation Systems Based on Hopfield Neural Network

The parameter identification based on Hopfield neural network (HNN) was applied to a static excitation system. The applicable algorithm of the identification method was given in detail. Nine-parameter excitation system was studied. The HNN of twenty neurons were designed in order to identify these parameters. Finally model validation was performed. Numerical simulation results testify that this method has high precision and quick convergence. The method can be implemented with electronic circuit, so it will benefit the on-line parameter identification of the excitation system and will have significance to any system that can be described by state space model.

Stator Flux Observation and Speed Estimation of a Doubly Fed Induction Generator

This paper developed the theory of decoupled control of active and reactive power for a doubly fed induction generator and discussed the methods to determine the stator flux and the rotor position. A closed-loop observer of stator flux is constructed, to which the deviations of the observed and measured rotor current were fed back. The observer constructed in the paper can eliminate the original errors of flux and restrain the errors arisen from the deviation of machines parameters. The rotor speed observation model is derived based on Lypunovs stability theory. The observers were implemented in a DSP excitation control device and the tests of rotor exciting current control without position sensors are developed. The results prove that the observers have good astringency and the rotor speed observation is effective.

Study on a fast controlled partition scheme based on improved Dinic max-flow strategy

When power system is subjected to severe disturbances and then will be out of step. The interconnected power grid should be split into several islands to avoid blackout. The controlled islanding is an active control technique based on the information from Wide Area Measurement System (WAMS) to accomplish the islanding task. This paper proposes a fast islanding strategy for large power networks. Firstly, the grid structure is mapped to point sets and edge sets in the graph theory. Secondly, the model is built by adopting the minimum power flow impact as the objective function and considering several constraints which includes generator coherency constraint and connective constraint. Finally, the optimal splitting strategy is searched by the improved Dinic maximum flow algorithm. Simulation results on IEEE 118-bus power system show that the proposed strategy is correct, effective and fast.

Transient stability analysis based on dimension reduction transform of rotor angles

Transient stability is of essential concern in power systems. With the widespread of wide area measurement system, the method using geometric features of trajectory in phase plane to detect power system transient instability online were proposed. This paper provides a graphical method based on phase plane. The dimension of the power angle trajectory was reduced in power-angle space so the trajectory was projected in a one-dimensional coordinate, to intuitively show stability characteristics, a new phase plane is defined based on the motion parameters obtained by dimension reduction and the transient stability could be judged by the convexity of trajectory in the new phase plane. The simulation of the New England 39-bus system shows that the proposed method provides an intuitive and effective approach for multi-machine system transient stability analysis and is useful in field applications.

A transient stability assessment method based on the trajectory in the dimension-reduced power-angle space

This paper proposed a new transient stability assessment (TSA) method based on the power angle space reduction on the trajectory phase plane (TPP). Firstly, the dimension of the power angle trajectory was reduced in power-angle space. Secondly, the trajectory was projected in a one-dimensional coordinate axis in order to present its physical significance. Thirdly, a new phase plane was formed according to the motion parameters that obtained by dimension reduction. Finally, the transient stability can be judged by the convexity of trajectory in the new phase plane. Concluded from the simulations of the New England 39-Bus system, our method is effective, efficient and can be applied on-line.

The Comparison and Analysis of Technology of Electric Power Information

With the continuous development of the Power market and the power of information technology, communication networks become increasingly complex and the number communication services is rapidly growing, the study of power of information technology become more important, this paper analysis the different communication needs of Power communication and study the characteristics and the requirements in various communication network. KEYWORD: Electric Power information; Power communication; fibre-optical International Conference on Industrial Technology and Management Science (ITMS 2015)