Showing papers in "Electric power automation equipment in 2003"

Research on commutation failure in HVDC transmission system Part 1:Commutation failure factors analysis

Abstract: Commutation failure,one of the most common faults in HVDC(High Voltage Direct Cur-rent )system,is related to many factors,such as voltage of commutation bus,ratio of converter trans-former,DC current ,firing angle,commutating voltage zero-crossing phase shift for system unsymmet rical fault,firing pulse control system of converter,AC system frequency spectrum and so onBased on the CIGRE HVDC benchmark model,the affect of these factors on commutation failure in the inverter is analyzed in detail and the general rules of commutation failure are obtained

High-speed transmission line relaying using artificial neural networks

Abstract: An ANN(Artificial Neural Network)is presented,which has the functions to determine and locate the faults within or outside the protection zone of a transmission line.The EMTP simulative tests for single-phase grounding fault and three-phase fault show that the fault can be exactly located and indicated by ANN within one period.It verifies this method is practical.

Short-term load forecasting based on wavelet neural network

Abstract: A short-term load forecasting model based on WNN(Wavelet Neural Network)is presented.WNN combines the time-frequency localization ability of wavelet and the self-education character of ANN(Artificial Neural Network),so its ability of reaching the global best results is more flexible and effective than that of ANN.At the same time ,WNN helps to improve the defects of ANN,such as the difficulty of determining rationally the structure,the existence of partial minimum points.The results of experimental research show that this method is accurate and fast.

Research on commutation failure in HVDC transmission system Part 2:Measures against commutation failure

Abstract: The sensitivities of the parameters that affect commutation failure in HVDC system are analyzed and the relations between them are discovered.Based on the sensitivity analysis and the analysis in Part one,the measures against commutation failure are given,including the preventive measures and the measures against followed commutation failure.

Issues and technology assessment on power quality Part 3:Voltage sags in power system

Abstract: The general aspects of voltage sags are discussed. New characterization methods consi-dering the magnitude and duration of voltage sags are used for classification. An assessment approach is presented in terms of reliability analysis methods. The performance indices relative to the requi-rements of sensitive loads and the quantities of voltage sags are given to assess effect of voltage sags. Several products for mitigating the effect of voltage sag are briefly described.

Application of GPRS technology in automatic meter reading system

Abstract: A new automatic meter reading system based on GPRS (General Packet Radio Service) ispresented to meet the demands for the reliability and real time performance of data communication. This scheme utilizes direct connection between GPRS network and internet, setting a server in In-ternet to take the charge of data communication between master station and terminal units for real-time data acquisition and transfer. Its structure and operational principle are introduced in detail. It is characterized by higher speed, great data throughput,teal-time performance and reliable communication. Its application in Dezhou Power Supply Company is proved successful and steady.

Incorporating weather effect in bulk power system reliability evaluation

Abstract: Incorporating weather effect in the reliability evaluation of bulk power system is studi ed.The transmission line model considering diverse weather conditions is constr ucted.Monte Carlo method is used to sample the weather regions and transmission lines,to determine the weather states and transmission line states.The proposed method can treat the situation,in which a trans-mission line may traverse several weather regions.The flowchart of reliability evaluation program considering weather effect is given and the inf luence of weather conditions on system adequacy is compared by case study.

Study of dynamic voltage restorer and its detecting method

Abstract: Dynamic Voltage Restorer(DVR)is used to protect the sensitive loads.The working prin-ciple of DVR and its structure are analyzed.An improved detecting algorithm based on"a bc-d q"transaction is brought forward,which is precise and fast.According to the different sensitivities of different loads to the phase angle jump of voltage sag,different compensating voltage waveforms and different control strategies are applied.The simulating results have verified the advantages of the improved detecting method.

On opening 500 kV- 220 kV electromagnetic loop circuit

Abstract: With the development of power transmission networks,electromagnetic loop circuits of 500 kV-220 kV appear in many places,some of which should be opened because they threaten the power system security. The insecurity, such as 220 kV-system overload caused by opening 500 kV-system,is analyzed. The security and stability of power system and the economic factors should be considered before breaking the electromagnetic loop circuit. A general procedure whether a loop circuit should be opened is proposed. The north power system of Shandong is analyzed as an example. This project is supported by State Power Corporation of China(SP11-2001- 04 -50 -10).

Chaotic oscillation control of electric power system based on adaptive backstepping

Abstract: Electric power system is likely to emerge chaotic oscillation or instability under stronger periodic load perturbationBackstepping controller has been designed to restrain chaotic oscillation when the magnitude of the periodic load perturbation is certainAdaptive backstepping controller has been designed to restrain chaotic oscillation when the magnitude of the periodic load perturba-tion is uncertain,it is proved by Lyapunov stability theory that the controlled system with which can obtain asymptotical stabilityThe performance of the controlle r has been evaluated by numeri-cal simulationIt is concluded that such a controller can drive chaotic or unstable trajectory of powe r system under stronger periodic load perturbation to the initial position,ie,the controller can restrain chaotic oscillation and make power system obtain asymptotical stabilityThe project is supported by Natural Science Research Project Foundation of higher education of Jiangsu prounce(03KJB470035)and Foundation of Science Research Development of Nanjing Uni-versity of Science and Technology

Adaptive PID controller based on single neuron for permanent magnet synchronous machine

Abstract: By analying the PMSM(Permanent Magnet Synchronous Machine)mathematics model and conventional control means,the adaptive PID(Proportional Integral Differential)controller based on single neuron is applied to regu-late the velocity and torque of PMSM.A great deal of simulative analy-ses has been conducted.The study result shows that,this control means has better dynamic adju-stment property and adaptive capacity,while the controller design is easier and parameter adjustment is convenient .It is suitable for engineering application.

Survey of bilateral contracts in power market

Abstract: As tremendous financial risk are brought to the participants by the power market,bilate-ral contracts,such as forward contract and future contract,are introduced into power market as an efficient risk-managing tool.Although a majority of electricity transaction is conducted through bi-lateral contracts,its research is far not enough until the failure of Californian electricity market.Based on the research papers of bilateral contract published recently,a brief summary is presen-ted,such as:the basic types and pricing theory,the risk management ,the strategy of participant and its influence on real time market.Combined with China power market,the future research emphases in this domain are brought forward.

Application of data fusion technology in substation locating

Abstract: Substation locating involves the information of power net,as well as the geo-spatial in-formation,within the planning areaIn order to consider more relative factors and improve the scien-tificalness and work efficiency of substation locating,data fusion technology is appliedFrom the D-S(Dempster-Shafer)evidential theory for image element level data fusion to the Analytic Hierar-chy Process general evaluation method for decision making level data fusion,it provides a new so-lution for multi-factor substation locatingThe example shows its efficiencySupported by Henan's science and technology key project(991140229)

Neural network decoupling control strategy and its applications in combustion system of fluidized bed boiler

Abstract: A neural network decoupling control strategy based on BP arithmetic is presented,which is applied in the combustion system of fluidized bed boiler.The idea is to make the prima -ry coefficient matrix of the broad controlled object including the decoupling unit a diagonal matrix.With its help,the com bustion system control of main steam pressure and bed temperature is successfully achieved.The simulation re sult shows that the coal supply and the primary air supply are controlled at the same time.This strategy can be used in complicated process con trol as in the combustion sys-tem control of circulating fluidized bed boiler.

Available transfer capability calculation based on continual power flow for transmission network

Abstract: A method for calculating ATC(Available Transfer Capability) based on continual power flow iterative linear estimation is presented A mathematical model of ATC evaluation is formulated and its computing method and flow are described It has been tested with IEEE30 bus-system and proved practical,reliable and effective The computation accuracy is compared between the continual power flow method and the DC sensitivity method,which shows the former is better Furthermore,the computation accuracy and speed are discussed for both fixed and variable augment of load parameter It is found that the computation accuracy is similar and the speed of variable augment case is faster

Instantaneous harmonic detection based on DFT

Abstract: A simple and practical instantaneous harmonic current detecting method is introduced,which realizes a special filter based on DFT(Discrete Fourier Transform)The filter has no fundamen-tal frequency decay and phase delay,and all harmonics above2nd order are filteredThe recursion of filtering algorithm is obtained according to filter’s response character and the calculation is thus greatly simplifiedThe digital harmonic detecting method based on this kind of filter can be used in any kind of power harmonic compensation systemThe theoretical analysis and simulation have shown that it keeps the accuracy and proves the following performance of digital filters

Fault locating algorithm for double-circuit line based on distributed parameter

Abstract: Based on the distributed parameter model of power transmission line,a new fault loca-ting algorithm for double-circuit line using the data of two terminals is presentedAccording to the distribution regularity of positive voltage's fault component along the transmission line and app-lying search method,it determines accurately the distance of fault point for various symmetric or non-symmetric inter-circuit or single-circuit faultsFurthermore,it does not require the synchronized data of two terminals and fault type identification,eliminates the influence of S/C resistance,line load and system impedance,and there is on false root

Study of power system load forecast based on wavelet neural networks

Abstract: The characters of WNN(Wavelet Neural Network)are analyzed and the advantages and disadvantages of its applications in power system load forecast are studiedBy theoretic analyzing the network structures and algorithms of WNN and BP Net and comparing the forecast results of power load,it is pointed out that WNN is suitable for forecasting the variable signalsWhen they have same number of network node,WNN is better than BP NET in forecast accuracyTherefore,WNN may be applied to reduce the number of hidden nodeIt is also indicated that current WNN has a poor convergence performance because of adopting the random initialization method and gradient training algorithm of traditional BP NET

Buyer's bidding strategies based on the static game theory with incomplete information

Abstract: The bidding process of electricity auction market with the der eg ulation of both genera-tion side and distribution side is studiedSeveral opti mal bidding strategies from a buyer’s point of view are also presented,which are based on the static game theory with incomplete informationFor the differ ence between buyers and market in evaluating the market-clearing price,a varia ble錳s introducedAccording to buyer’s different pay off functions,pure str ategies and mixed strategies are developed respectivelyThe bidding strategies for a supposed simplified market model are givenThe simulative results show th e correctness and feasibility of the proposed methods

Remote monitoring system with Modbus-based controllers

Abstract: The effective implementation of Modbus protocol in remote monitoring system with Mod-bus-based controllers is studied.Its main techniques and specific definitions are introduced.The hardware structure of remote monitoring system and the design of monitoring software are presented with an example.The development of remote monitoring system with Modbus-based controllers has been accomplished and operated effectively in power plants.

Integrating reliability cost and reliability benefit of distribution system

Abstract: Based on their concepts,the objective function for the optimization of investment strate-gy combining reliability cost with reliability benefit is given.In accordance with the characteristics of distribution system,two criterions for deciding if the fuse and the backup transformer should be mounted in load branch respectively are presented.According to the two criterions,the objective function is then simplified.A test example is given.

Risk control for power suppliers in power market

Abstract: Power suppliers take into account not only the profit,but also the risk in power market.Based on the definition of risk for generation bidding,a bidding model of single period and its risk management for power suppliers are studied.Using the certainty equivalence model theory,which is mature among the traditional investment risk theories,the balance curve of profit and risk,which reflects the risk tendency of investors,is obtained through inquiring and testing.With the comparison and analysis of profit and risk,the practical method and bidding concept based on MCP(Market Clearing Price)for power suppliers in bidding strategy selection is given.

Issues and technology assessment on power quality Part1:General concepts on power quality

Abstract: The general concepts are defined,such as power quality,EMC(Electro Magnetic Compati-bility),etc.In view of both supply quality and custom demand,the impact of quality indices on sys-tem and the approaches to isolate a special load from disturbing sources are in vestigated.Ancillary services of power quality with respect to custom power are proposed.

Automatic meter reading system solution and its realization

Abstract: The structure and functions of AMR(Automatic Meter Reading)system are improved and extended,and a solution linking with internet is put forward.The master center's software is deve-loped,which has powerful functions such as meter-reading and billing,power utilization analysis,line-loss and transformer-operation analysis,distribution-system monitoring,user query via internet,and interconnection with MIS(Management Information System)and DMS (Distribution Management System).It enriches the methods of power utilization management and improves the economy of ope-ration expense.The system structure,the functions and design of master center's software are intro-duced and its further improvement and development are discussed.

Studies on quality control center and unified power quality conditioner

Abstract: Power quality problems are becoming an emphasis of related research fields nowadays due to the higher demands of social and economical development.Based on the detailed study of the QCC(Quality Control Center)in FRIENDS(Flexible,Reliable and Intelligent Electrical eNergy Delive-ry System),which is first put forward by Japanese scholars,the functions of QCC is expanded and its basic types and structures are defined.A detailed study on UPQC(Unified Power Quality Condi-tioner),the chief part of QCC,is carried out ,its multiple adjusting functions are introduced and its typical topological circuit is presented.The synthesis tracking compensation of voltage and current for UPQC is realized by using H ∞ control technology and the satisfactory simulation results are given.

Single load shifting of power distribution systems based on shortest path arborescence

Abstract: After analyzing the multi-power-supply distribution system,the model of close-loop path selection based on shortest path arborescence is delivered and an efficient reasoning algorithm is proposed.This algorithm makes full use of the shortest path arborescence theory and considers the economical factors in selecting the close-loop path.The example given proves its practicability and feasibility.

Reserve capacity for load variation in power market environment

Abstract: Profits is one of the important goals of grid company in power market environment.Using probabilistic method,the feasibility of load shedding,the costs of reserve capacity for load and load shedding are analyzed.It is proposed that,in power market environment ,the optimal reserve capacity for load variation(in economic sense)should be determined in light of costs of reserve capacity and load shedding.The simulation results show that the method is feasible and economic.

Combined power load forecast model based on Matlab neural network toolbox

Abstract: Combined forecast is an effective method in power load forecast,which usually adopts weighted processing of each forecast model and requires stable model error in combined forecast.But the forecast errors are not well proportioned in power load forecast.An artificial neural network based combined forecast model is presented,which automatically adjusts the weight of each forecast model by network training for complicated non-linear system.The Matlab artificial neural network toolbox is used to avoid the complicated model structure and long training time in establishing the combined forecast model.The model is not only simpler in programming,but also quicker in convergence.The calculation example shows that it is practical and effective.

Design of MAX125/126 based data acquisition unit for on-line monitoring system electrical equipment

Abstract: Usually it is necessary to simultaneously sample several signals in the on-line monitoring of electrical equipmentThe high speed,14bit,multi-channel simultaneous sampling A/D converter of MAXIM realizes the accurate phase measurement for several waves,which can be used in the on-line monitoring system of electrical equipment for multi-channel simultaneous data acquisitionIts HW and SW design is presentedThe practical verification shows that its performance is excellent and its realization is easy and economic

Improved principal component analysis to feature selection for transient stability assessment

Abstract: The principal component analysis is used to select the input features premising no original data lost.With the consideration of its limitations in data standardization and nonlinearity processing,an improved principal component analysis is presented.Since the feature vectors affecting power system transient stability are dramatically similar to each other in the input space,the dy-namic clustering analysis is applied to divide the data set into several parallel subsets for further reducing the dimensionality of input space and improving calculation speed and effact.The associa-tive classification is employed to classify the data and assess the transient stability.The simulative calculation of a3-machine9-bus system verifies its effectiveness.