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TENCON '93. Proceedings. Computer, Communication, Control and Power Engineering.1993 IEEE Region 10 Conference on

Date 19-21 Oct. 1993

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Displaying Results 1 - 25 of 146
  • The practical criterion of generator self excitation and its field example analysis

    Page(s): 1 - 4 vol.5
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    Power stations in a large power system (especially hydroelectric power stations) are usually located far from the load center. Therefore EHV long range power transmission is inevitable. The generator will likely to be self excited due to the long transmission line charging current under the no-load state. This paper introduces four self-excitation criteria for a generator in a power system possessing a no-load long transmission line. They are: the fast estimation method; the impedance comparison method; the circle diagram method; and the charging characteristic method. Each method is checked by actual power system self-excitation contingency and field self-excitation tests together with calculations and analyses. It is proved that these four methods of self-excitation criterion are accurate, fast and reliable as well as practical.<> View full abstract»

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  • An expert system approach to unit commitment problem

    Page(s): 5 - 8 vol.5
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    This paper describes a hybrid expert system dynamic programming approach to the power system unit commitment problem. Here the scheduling output of the usual dynamic programming is enhanced by supplementing it with the rule based expert system. The proposed system limits the number of constraints and also checks the possible constraint violations in the generated schedule. The expert system communicates with the operator in a friendly manner and hence the various program parameters can be adjusted to have an optimal, operationally acceptable schedule.<> View full abstract»

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  • Daily reliability dispatch of generating units

    Page(s): 9 - 13 vol.5
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    In accordance with a new viewpoint of operating risk, probabilistic power system unit commitment is studied in this paper. The proposed approach takes the unit stochastic failure characteristics and uncertainty of load forecasts into account. With the prediction of operating risk, a dynamic programming model for daily unit commitment is established to minimize the objective function of spinning reserve throughout a day, and an algorithm is also proposed. A numerical example is given to illustrate the application of the proposed approach, and the results show that the approach and algorithm are both feasible and efficient.<> View full abstract»

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  • Coordinative control of excitation and fast valving using artificial neural networks

    Page(s): 14 - 18 vol.5
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    A cooperative control scheme of power system generation excitation and fast valving based on artificial neural networks is proposed in this paper. Two neural networks are used to coordinate excitation and fast valving control. Digital simulation and physical laboratory experiments of a simple neural network controller are presented.<> View full abstract»

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  • Nonlinear thyristor-controlled SVC control for power system stability enhancement

    Page(s): 19 - 22 vol.5
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    In this paper, a nonlinear feedback method based on differential geometry theory is employed to derive a novel control approach for static VAr compensation (SVC). The paper first constructs the nonlinear model for the power system with SVC control. The conditions to algebraically transform the nonlinear model to a linear system are then verified. The linearized model is obtained by feedback linearization, and optimal SVC control laws are then derived for power system stability improvements. The paper concludes with presenting some interesting simulation results.<> View full abstract»

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  • The nonlinear excitation control of generators

    Page(s): 23 - 26 vol.5
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    In this paper, a new nonlinear control principle based on Lyapunov stability theory is studied. By using the principle, a new nonlinear excitation control method is analyzed. The computer simulation and the experiment study on the micromachine system in the laboratory show that the control method is robust. It possesses better control effect, when the system parameters or operation conditions are varied.<> View full abstract»

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  • An adaptive turbogenerator excitation controller based on artificial neural network

    Page(s): 27 - 31 vol.5
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    In this paper, an adaptive turbogenerator excitation controller based on an artificial neural network (ANN) is developed. The proposed controller is a four layered feedforward neural network. The third layer produces the control signal and the fourth layer gives the output signal. The signs of plant error are introduced. The control strategy is reached continuously by adjusting weights and thresholds of the network. This controller is applied to a sample excitation system and is compared with an optimized PID controller. The computer simulation shows that the result is effective.<> View full abstract»

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  • The most compact digital regulator for thyristor excitation of large alternators

    Page(s): 32 - 36 vol.5
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    The paper presents a new variety of the microprocessor-based excitation regulator (MPER), which has been operating on thyristor excitation systems of many large alternators. Several essential improvements significantly reducing the hardware as much as possible are introduced. The hardware elements are replaced by software elements leading to the most compact digital regulator.<> View full abstract»

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  • An approach of object oriented database for open energy management system

    Page(s): 37 - 39 vol.5
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    In this paper an approach of object oriented database for an open energy management system is introduced. The requirement of an open system and the merit of the object oriented programming technique are briefly described. An example of object oriented database design is proposed.<> View full abstract»

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  • An asynchronously coordinating load flow calculation algorithm for the distributed energy management system (DEMS)

    Page(s): 40 - 43 vol.5
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    Trends in modern power systems are promoting traditional EMSs to develop towards the form of distributed energy management system (DEMS). The communication network is a very important composing part of DEMS. Based on the two-level hierarchically coordinating mechanism model of a DEMS presented in this paper and by taking the unpredictable communication time delay into account, an asynchronously coordinating load flow algorithm for DEMS has been proposed. The test results show that the asynchronous algorithm is of much more practical value than its synchronous counterpart.<> View full abstract»

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  • A microcomputer real-time supervisory system with management and dispatch functions for the hydropower stations

    Page(s): 44 - 50 vol.5
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    The constituent principle of a new two-level microcomputer real-time supervisory system is discussed. It can be used for medium- and large-sized hydropower stations. The system has several functions: acquisition, processing, regulation, optimum operation, control, synchronism, event recording; fault reminiscing, waveshape record, diagnosis and process; relay protection, dispatch terminal and the work station of the management system, etc. The system is composed of a main supervisory system of the station room, monitor system of the chief office and monitor system of the engineering office. A two-level microcomputer configuration is used in the main supervisory system , and two-way parallel interrupt communication is used between two levels. The communication between the main system and the monitor system of the engineering office is realized with a string communication interface, and the communication between the monitor system of the station chief office and the dispatch centre of the electric power network is realized with a telecommunication interface. The lower position microcomputer uses AC sampling to acquire the field AC analog signal and uses DC sampling to acquire the nonelectrical signal through a transducer. Modularized programming is used in the system software. The module is dispatched by a real-time operation system.<> View full abstract»

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  • Online security analysis based on database method for electrical power system

    Page(s): 51 - 54 vol.5
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    Online security analysis (OSA) is one of the important functions of dispatching automation for modern power systems. In this paper, a new method of OSA based on a database is presented. The fundamental principal of this method is that a large amount of real time calculation would be substituted by a small amount of processing data which are obtained from the OSA database. This database is established by means of organizing the offline calculation data. The results of finite and reasonable offline calculation are taken as an OSA database. Then the theory of OSA using the database and its algorithm are developed. The application of this method to two practical power systems shows that it is a new way to carry out OSA in large power systems and has a wide spectrum in power system real time applications.<> View full abstract»

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  • A new active power corrective control algorithm based on sensitivity method

    Page(s): 55 - 58 vol.5
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    This paper proposes a new algorithm to solve the problem of active power corrective control in power systems. This algorithm is based on a swift decoupling sensitivity matrix, in which the power value of each part is denoted by a function with corresponding control sensitivity as the variable. Through this function and a defined static power transfer coefficient (SPTC), one can evaluate the control variables by minimizing this nonrestraint objective function, hence over-limit values will be removed or avoided. The least square method is utilized to get the final values of control variables. Positive results from analogue computing proves the rationality and validity of this new algorithm.<> View full abstract»

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  • Automatic generation control for Gezhouba Erjiang Hydropower Plant

    Page(s): 59 - 63 vol.5
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    The authors present a new approach to solving the automatic generation control (AGC) problem stage by stage, using in each stage different methods, namely dynamic programming, known as "priority indices of generating unit start/stop" and the principle of equal incremental of water flow, which was implemented at Gezhouba Erjiang Hydropower Plant. Since June 1989 the AGC program has operated continuously and successfully. Plant operation security was significantly improved. The plant automation level was raised. Considerable economical benefits were obtained. In comparison with other methods, this approach has many important advantages. The proposed approach is suitable for use in various hydropower plants.<> View full abstract»

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  • Short-term thermal unit commitment including reliability and dynamic economic dispatch

    Page(s): 64 - 67 vol.5
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    This paper presents a probabilistic technique which can be used to develop unit commitment schedules for continually changing loads in a power system for a specified period. The technique is developed on the basis of a system fulfilling reliability and dynamic economic dispatch. Typical unit commitment cases are illustrated with numerical examples.<> View full abstract»

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  • H/sub /spl infin// controller design for power system load frequency control

    Page(s): 68 - 71 vol.5
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    In this paper, an H/sub /spl infin// controller, based on the standard H/sub /spl infin// control design approach, is proposed for power system load-frequency control with system parametric uncertainties. The variation bounds of power system parameters are obtained by changing parameters by 30% to 50% simultaneously from their typical values. The proposed H/sub /spl infin// controller is effective and can ensure that the overall system is asymptotically stable for all admissible uncertainties. The simulation results show that for the example system the proposed H/sub /spl infin// load-frequency controller can achieve good performance even in the presence of generation rate constraint.<> View full abstract»

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  • On-line transient stability assessment in operation-DEEAC in Northeast China Power System

    Page(s): 72 - 76 vol.5
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    Achievements in on-line transient stability assessment of the Northeast China Power System are reported in this paper. The improved dynamic extended equal area criterion (DEEAC) is interfaced to a state estimator with DBMS in an advanced EMS environment. Thousands of DEEAC results, recorded from snapshots of on-line estimations have been thoroughly checked with an off-line numerical integration method. For first swing stability assessment of both symmetrical and asymmetrical faults, there are only less than 1% of cases whose errors exceed 10%. Moreover, all large errors occur with mild contingencies only. Each critical clearing time (CCT) calculation takes about 10 s CPU time of a VAX-11/785 computer. In an HABITAT environment (developed by ESCA Corp.), the on-line EEAC package is very user-friendly.<> View full abstract»

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  • Novel extended equal area criteria with detailed power system models

    Page(s): 77 - 81 vol.5
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    Incorporated into extended equal area criteria (EEAC) in a parametric manner, detailed models of generators with field flux decays and excitation systems in varying degrees are taken into consideration. A simple and convenient cluster of modular EEACs with excellent adaptability both in model and application environment are developed in this paper. Corresponding methods to calculate the critical clearing angle (CCA) of the one machine infinite bus (OMIB) system are constructed in fully analytical forms. A new approach for correction of large errors of EEAC resulting from inaccurate OMIB equivalency is proposed. The invalidity of EEAC is greatly minimized.<> View full abstract»

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  • Application of extended equal area criterion to asymmetrical faults with successive single-phase reclosing

    Page(s): 82 - 86 vol.5
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    The extended equal area criterion (EEAC) succeeds in expressing critical clearing time, stability margin and their sensitivity coefficients in algebraic forms. Single phase switching and reclosing are widely used in China to enhance the stability performance under asymmetrical contingencies. This makes direct methods to face new challenges and provides the motivation to enhance EEAC further to deal with all kinds of single asymmetrical contingencies and some double asymmetrical contingencies. While keeping the previous simplicity, accuracy and fast speed, this new extension makes the EEAC method even more powerful.<> View full abstract»

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  • Estimation of transient stability limits using artificial neural network

    Page(s): 87 - 90 vol.5
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    In this paper, the nonlinear mapping relation between the transient energy margin and the generator power at different fault clearing time was established by using the multi-layer feedforward neural network of the perceptron type, Lyapunov's direct method based on the system dynamic equivalents was used as a fast method to obtain the training set of the artificial neural network (ANN), the transient stability power limits of the generator at different fault clearing time were estimated very quickly by ANN. The proposed approach has been tested on a practical 59-generator power system, and the results were found to be quite accurate.<> View full abstract»

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  • Using artificial neural network to assess transient stability of power systems

    Page(s): 91 - 94 vol.5
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    For the safe running of a power system, it is very important to assess, online, power system transient stability. The frequency domain and time domain calculation methods for stability assessment are time consuming, therefore, neither one is suitable for the purpose. ANNs have recently been proposed as an alternative method for solving certain traditional problems in power systems where conventional techniques have not achieved the desired speed, accuracy or efficiency. The application areas of ANNs are mainly regression, classification and combinatorial optimization. Using ANNs to assess power system transient stability is a classification problem. An ANN needs quite a long time for offline training, however, having been trained, it needs only a very short time to make a classification for a problem. Here, the authors describe how a multilayer feedforward ANN is suitable for the online transient stability assessment of power systems.<> View full abstract»

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  • A simple method for studying the influence of bus loads on power system transient stability

    Page(s): 95 - 98 vol.5
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    Transient stability is an important problem in power systems. The influence of bus loads on power system transient stability is one of the main concerns by operators. This problem is studied and a simple method for studying the influence of bus loads on transient stability is presented in this paper. It can avoid recomputing the new power flow and reforming the reduced admittance matrices. Furthermore, sensitivity analysis can be used to speed up transient stability assessment. Some simulation results and comparisons are given.<> View full abstract»

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  • Steady-state stability analysis of a power system containing power system stabilizers and SMES controllers: a comparative study

    Page(s): 99 - 102 vol.5
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    The paper presents the results of a comparative study of two damping controllers, i.e., the power system stabilizer (PSS) and the superconducting magnetic energy storage (SMES) controller, on damping generator oscillations. The developed scheme employs proportional-integral-derivative (PID) damping controllers to enhance the damping of both the mechanical mode and exciter mode of the studied power system. The parameters of the proposed controllers are determined by using a unified approach based on modal control theory. A frequency-domain approach based on root loci analysis and a time-domain approach based on nonlinear model simulations are accomplished in order to demonstrate the effectiveness of the proposed schemes and to compare the different damping effects provided by two damping controllers.<> View full abstract»

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  • A fast calculating method of determining generator transient stability power limit

    Page(s): 103 - 106 vol.5
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    This paper proposes a new fast calculating method for the transient stability limits for the output power of generators, using the fast higher order Taylor series expansion and the equal area criterion for multimachine power systems. The results of calculation experiments show that this method not only has better accuracy but also possesses fast execution speed, and therefore has practical value.<> View full abstract»

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  • Application of robustness theory in the analysis of subsynchronous oscillation [of power systems]

    Page(s): 107 - 110 vol.5
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    In this paper, the applicability of the recently developed frequency-domain, matrix-norm robustness theory for the analysis of subsynchronous oscillations in a power system is explored. Based upon structure preserving multivariable feedback model, a set of new robustness theorems are developed. These theorems can be used to analyse the effects of parameter perturbations on the stability of subsynchronous oscillations in a power system and can provide useful measures for evaluating the tolerance of the system to modeling errors. An example is provided to demonstrate the effectiveness of these theorems.<> View full abstract»

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