Showing papers in "Electric Machines and Power Systems in 1990"
TL;DR: In this paper, the authors present an energy fundiment analysis for power system stability, focusing on the reliability of the power system and its reliability in terms of power system performance and reliability.
Abstract: (1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.
1,080 citations
TL;DR: In this paper, an analysis of the automatic generation control based on a new area control error strategy for an interconnected hydrothermal system in the discrete mode considering generation rate constraints (GRCs) is presented.
Abstract: The paper presents an analysis of the automatic generation control based on a new area control error strategy for an interconnected hydrothermal system in the discrete-mode considering generation rate constraints (GRCs). The investigations reveal that the system dynamic performances following a step load perturbation in either of the areas with constrained optimum gain settings and unconstrained optimum gain settings are not much different, hence optimum controller settings can be achieved without considering GRCs in the mathematical model.
60 citations
TL;DR: In this article, a new method of computer-aided design optimization of a three-phase induction motor is proposed, which is based on the modified Hooke-Jeeves method.
Abstract: A new method of computer-aided design optimization of a three-phase induction motor is proposed. Due to the highly non-linear nature of the design optimization problem an approach using the modified Hooke-Jeeves method is employed. The optimization of the objective function (motor efficiency) is deduced in terms of eight independent motor design variables which are then used to predict seven performance indices and the cost index of the machine. The method is applied to optimize the design of a 5-HP motor. The results obtained are compared with those of an optimally designed motor [3].
45 citations
TL;DR: A review of the existing techniques for the reactive power allocation in large power systems is presented in this article, where the authors describe the problem with its significance to the operation and planning of power systems.
Abstract: This paper reviews of the existing techniques for the reactive power allocation in large power systems. The description of the problem with its significance to the operation and planning of power systems is presented. Merits of the corresponding techniques are reviewed according to their types of formulation.
23 citations
TL;DR: In this article, the authors determine the loss distribution in a 11 kW, fan-cooled, slip-ring, induction machine using a simple thermal model which splits the machine into elementary blocks.
Abstract: In this paper we determine the loss distribution in a 11 kW, fan-cooled, slip-ring, induction machine. We use a simple thermal model which splits the machine into elementary blocks. The parameters of this model are determined by temperature measurements yielded during typical tests. We then use our model to analyse and localize the losses under several operating conditions.
14 citations
TL;DR: A microcontroller-based controller for SRM drives with only an EPROM and two ICs for the logic access constituting the peripheral circuits is introduced.
Abstract: There is a growing interest in the use of switched reluctance motor (hereafter referred to as SRM) drive systems for various applications in diverse areas such as defense, home appliances, etc. Hence the design of a low cost controller for the SRM drive with high performance capabilities gains added significance. Microcontrollers (single chip computers) have emerged to fill this need in motion control. They provide both software control and flexibility in the reconfiguration of control algorithms. They also minimize the number of chips thus enhancing the system reliability at a low cost. This paper introduces a microcontroller-based controller for SRM drives with only an EPROM and two ICs for the logic access constituting the peripheral circuits. The entire control scheme including the pulse width modulator is implemented by software. A Siemens 80535 microcontroller chip has been chosen for this study.
14 citations
TL;DR: In this paper, the problem of transmission networks expansion has been solved by considering the cost of losses as well as the investment in the objective function using an exact quadratic programming technique.
Abstract: In this paper, the problem of transmission networks expansion has been solved by considering the cost of losses as well as the cost of investment in the objective function. The problem is solved using an exact quadratic programming technique. This new formulation has been applied to a 6- bus system. The final configurations, which are characterized by minimum cost of losses show that as the cost of the Kwh increases, the total system cost decreases.
13 citations
TL;DR: In this paper, the influence of different levels of complexity in modelling various constituent subsystems on the dynamic stability of power systems compensated by static var systems (SVS) operating on pure voltage control is discussed.
Abstract: This paper is concerned with the influence of different levels of complexity in modelling various constituent subsystems on the dynamic stability of power systems compensated by static var systems (SVS) operating on pure voltage control. The system components investigated include thyristor controlled reactor (TCR) transients, SVS delays, network transients, the synchronous generator and automatic voltage regulator (AVR). An overall model is proposed which adequately describes the system performance for small signal perturbations. The SVS performance is validated through detailed nonlinear simulation on a physical simulator.
11 citations
TL;DR: In this article, the authors present a method for the optimal design of overhead high voltage 3-phase transmission lines, where the optimization objective is to minimize the line total annual cost, both fixed and running cost items have been considered.
Abstract: This paper presents a method for the optimal design of overhead high voltage 3-phase transmission lines. The optimization objective is to minimize the line total annual cost. Both fixed and running cost items have been considered. The optimization procedure takes also the line relevant technical constraints into account. The solution yields the main design parameters of the line as well as the optimal values of transmission voltage and the optimal number of bundles. The load factor of the transmitted power is taken as one of the optimization input data. Several case studies are presented to compare the suggested methods to other available design procedures.
9 citations
TL;DR: In this article, an analytical method to determine the instantaneous electromechanical torque on PM machines for a known quasi-square phase current and the corresponding maximum, minimum, average and pulsating torque was presented.
Abstract: This paper presents an analytical method to determine the instantaneous electromechanical torque on PM machines for a known quasi-square phase current and the corresponding maximum, minimum, average and pulsating torque. The influence of some of the design parameter on the performance of the machine will be investigated on this paper.
6 citations
TL;DR: Two fast and efficient algorithms are developed, one for the enumeration of loops of the network graph, and the other for the determination of the minimum break point set, which show the computational efficiency of the proposed algorithms over the existing methods and establish their superiority.
Abstract: Ensuring proper coordination of relays in transmission protection system is a vital task. Determination of break points is of great significance in the computer aided design of a transmission protection system. In this paper, two fast and efficient algorithms are developed, one for the enumeration of loops of the network graph, and the other for the determination of the minimum break point set. These algorithms are compared with the existing methods and the results are presented. The results clearly show the computational efficiency of the proposed algorithms over the existing methods and establish their superiority.
TL;DR: In this paper, an alternate method of determining the harmonic currents of a six-pulse AC-DC converter is described, which uses the harmonic voltages to predict the firing angles and the resulting injected harmonic currents.
Abstract: An alternate method of determining the harmonic currents of a six pulse AC-DC converter is described. This method uses the harmonic voltages to predict the firing angles and the resulting injected harmonic currents. The model avoids the complexities of power flow solutions methods and offers more accuracy than the usual current injection techniques. Also, the model is able to operate under balanced or imbalanced conditions. Its accuracy is shown with time domain solutions.
TL;DR: In this article, a method of computing the quasi-stationary magnetic field in steel laminations in presence of hysteresis was presented, where the authors used the finite element method based on Galerkin formulation to solve the nonlinear diffusion equation.
Abstract: This paper presents a method of computing the quasi—stationary magnetic field in steel laminations in presence of hysteresis The related nonlinear diffusion equation is solved using the finite-element method based on Galerkin formulation For the inclusion of hysteresis, B—H loops are simulated by Preisach theory The computed results are compared with experimental results A good correlation is obtained between the two results
TL;DR: In this paper, the properties of an ironless rotor synchronous machine with null-flux windings on the stator and radial displacement of the rotor are derived based on an analytic representation of a three-dimensional excitation field and on considering the SM as a dynamic system with three generalized coordinates.
Abstract: The properties of an ironless rotor synchronous machine (SM) with null-flux windings on the stator and radial displacement of the rotor are considered. The system of the SM equations are derived. These equations are based on an analytic representation of a three-dimensional excitation field and on considering the SM as a dynamic system with three generalized coordinates, two of which are the coordinates of the Center of rotor mass and one is the angle coordinate which characterizes the rotation of the rotor on its own axis. On the basis of the solution of the equations we obtain the relations for all the basic quantities: radial and centering forces, radial suspension stiffness and parameters of the null-flux circuit. They characterize all the properties of the SM in the state when the rotating rotor undergoes a radial displacement.
TL;DR: In this paper, the authors derived simple approximate closed expressions for both the output frequency and the magnetizing reactance of an induction generator under steady state conditions and for a given capacitor value.
Abstract: For an induction generator to be self excited a capacitor with a sufficient value has to be connected to its stator terminal. Under steady state conditions and for a given capacitor value, two unknowns have to be found to resolve the machine unknowns: the output frequency and the magnetizing reactance. Finding these two unknowns requires simultaneous solution of two high degree polynomials. Numerical techniques are usually involved. It is typical, however, for the induction generator to have a small but negative slip. This fact is used in this paper to derive simple approximate closed expressions for both the output frequency and the magnetizing reactance. The calculations using these expressions show excellent agreement with the exact values obtained by numerical techniques
TL;DR: Preliminary tests on a standard test system, reveal that the number of network solutions required for convergence per time step can be reduced by half, which provides ample scope for speeding up the algorithm without sacrificing accuracy.
Abstract: The simultaneous implicit approach proposed in [1] has become the state-of-the-art for transient stability simulation.The associated algorithm results in considerable saving in CPU time and elimination of interface errors between the set of algebraic equations of the network and the synchronous machines,and the set of differential equations of synchronous machines and associated control systems. In this paper, certain significant changes are proposed to this approach, with the aim of speeding up the algorithm without sacrificing accuracy. These changes are (i) convergence criterion based on generator real power output rather than rotor angle, (ii) a two—tier approach for the iterative solution of algebraic and differential equations, and (iii) better corrector formula for rotor angle [2]. Preliminary tests on a standard test system, reveal that the number of network solutions required for convergence per time step can be reduced by half. This feature of the algorithm provides ample scope for redu...
TL;DR: In this paper, the authors deal with the combined hydraulic-thermal effects in radial channels of electric machines, where the results are given in the form of dimensionless relations and coefficients which make their practical application much more easier.
Abstract: This article deals with the combined hydraulic-thermal effects in radial channels of electric machines. The introductory part describes survey information gathered from the relevant literature and gives the objective as well as purpose of the presented article. This is followed by a description of the model facilities after which the author describes the method of measuring. The results are given in the form of dimensionless relations and coefficients which make their practical application much more easier. For the evaluation and comparison purposes the following data were used: - Characteristics of the heat transfer in rotating channels, both in laminar and turbulent region of flow. - Data for the computation of the hydraulic resistance of the air gap between rotor and stator, above all when taking the effect of rotation into account. - Basic information on the effects of filling the channels round stator coils. - Data on the existence of pressure pulsations in the radial channels of both stator...
TL;DR: In this article, the performance of a 3-hp cage induction motor fed from a load commutated inverter is analyzed for a wide range of speed; and is verfied experimentally.
Abstract: An approach, to analyse the performance of a variable speed cage induction motor drive fed from load commutated inverter (LCI), is presented. Induction motor with an appropriate capacitor across its stator terminals constitutes the load on the inverter. A fully controlled bridge converter, supplied by a variable dc voltage source, commutated with the back emf of the motor, acts as an inverter. An algorithm to compute the motor performance, is developed using equivalent circuit representation of the system. Strategies for the selection of control variables, in order to achieve the desired speed range for satisfactory performance of the drive are given. The performance of a 3-hp, cage induction motor fed from LCI is computed, using the developed algorithm for wide range of speed; and is verfied experimentally.
TL;DR: In this paper, an unique microprocessor based thyristor controlled method of controlling the VAR supply at the load node of a typical distribution system has been developed, which is a totally software dependent static VAR compensator enhancing its reliability and flexibility of control.
Abstract: An unique microprocessor based thyristor controlled method of controlling the VAR supply at the load node of a typical distribution system has been developed. The developed model is a totally software dependent static VAR compensator (SVC) enhancing its reliability and flexibility of control. The conventional hardware complexity being eliminated, a prototype working model has been developed for application in the laboratory. The developed scheme has also been found to be advantageous due to its symmetrical and accurate triggering control and quick response.
TL;DR: The information matrix that approximates the Hessian matrix in the WLS estimator is updated using the Brown-Dennis technique such that the linear convergence of the W LS algorithm is improved to nearly second order convergence ofThe Newton method.
Abstract: This paper describes the Newton method for state estimation in electric power systems using the weighted least square approach (WLS). The information matrix that approximates the Hessian matrix in the WLS estimator is updated using the Brown-Dennis technique such that the linear convergence of the WLS algorithm is improved to nearly second order convergence of the Newton method. This proposed method is particularly effective in state estimation of ill-conditioned power systems which encounter difficulties in converging to the solution. The additional computing time for implementing the new algorithm is quite small as the nonzero elements of the Hessian matrix are not re-computed but are extracted from the Jacobian stored in the computer memory. However, there is a slight increase in the storage requirement. Digital computer results are presented for both the static and tracking state.
TL;DR: In this paper, the authors investigated the solid state speed control of a repulsion motor using a triac in the stator circuit, which was accomplished by varying the triac firing angle.
Abstract: This paper investigates the solid state speed control of a repulsion motor using a triac in the stator circuit. The speed control is accomplished by varying the triac firing angle. In addition, this paper investigates the harmonic contents of the rotor current, stator current and stator voltage. The waveforms of these variables were generated and then analyzed numerically for their harmonic content using a Fouries Series Subroutine. The results were validated by comparison with obtained experimental results.
TL;DR: In this paper, a 3-phase induction motor supplied through a distribution transformer and during starting period, subjected to a very short time supply disturbance from the primary side of the transformer, while the secondary side is still connected to the machine, has been studied.
Abstract: The dynamical behaviour of a 3-phase induction motor supplied through a distribution transformer and during starting period, subjected to a very short time supply disturbance from the primary side of the transformer, while the secondary side is still connected to the machine, has been studied. The analysis has been made by simulating the machine in time domain by using traditional d-q model, including the effect of transformer secondary vinding impedance during the disturbance period. To verify the accuracy of the digital model, the normal starting transient torque-time pattern under free acceleration is computed and compared with the previously measured results. The transient torque-time, speed-time and current-time patterns of two different machines are computed for the phenomenon under investigation and are compared with their counterparts resulting from starting under free acceleration. Also the effect of the supply disturbance time duration on the transient torque peak has been studied. It w...
TL;DR: In this paper, a decoupled method for ranking contingencies based on voltage deviation, overload and reactive power limit violation performance indices is described, which is based on non-iterative compensation technique.
Abstract: This paper describes a decoupled method for ranking contingencies based on voltage deviation, overload and reactive power limit violation performance indices. It is based on non-iterative compensation technique. A novel method of secondary injections at voltage controlled buses (including slack) to maintain their voltages constant and secondary injections at slack bus to maintain its angle constant has been developed. Results for four sample test systems have been obtained to test the effectiveness of the method. The rankings obtained by the new method are in good agreement with those generated by rigorous A.C. load flow solutions for all the test systems investigated.
TL;DR: In this article, a high-speed induction motor with active magnetic bearings: both radial and axial, is discussed, and a decentralized control system of active magnetic bearing is proposed to provide robustness to parameter detuning and perturbations.
Abstract: Active magnetic bearings are credited with high performance in terms of low energy consumption, high speeds, increased reliability and low maintenance costs. This paper discusses a high-speed induction motor with active magnetic bearings: both radial and axial. The decentralized control system of active magnetic bearings is based on sliding mode variable structure principle to provide robustness to parameter detuning and perturbations. Test results on a laboratory model of 300 W and 25000 rpm motor designed and built for the scope are very promising for applications to high speed machine tools, vacuum pumps etc.
TL;DR: In this article, an analytical approach and stability criteria for the sustained subharmonic ferroresonance phenomenon was presented, and certain comparisons between experimental and calculated results are included.
Abstract: An increasing use of series capacitors to overcome the inductive voltage drops and to improve the power factor in distribution systems has revived the interest in ferrorsonance phenomenon. In this paper, an analytical approach and stability criteria for the sustained subharmonic ferroresonance phenomenon presented. Certain comparisons between experimental and calculated results are included.
TL;DR: In this article, the authors present a method of analyzing the ferroresonance phenomenon solving the performance equations with generalized parameters including the effects of hysteresis, using normalized loop and standard coefficients.
Abstract: Inclusion of hysteresis effect on ferroresonance usually requires a detailed knowledge about the hysteresis loop of the material used in the core. Using normalized loop and standard coefficients reduces this requirement. Thus, it is possible to represent the magnetic material in performance equations in terms of circuit parameters, constructional parameters and supply parameters. On the other hand, generalizing these parameters consequently allows to reduce their number, computation time is reduced when the response of the circuit to any change in these parameters is studied. This paper presents a method of analyzing the ferroresonance phenomenon solving the performance equations with generalized parameters including the effects of hysteresis.
TL;DR: In this paper, the authors presented new contributions to the optimization of size and control setting of continuous shunt capacitors on distribution feeders to reduce power and energy losses in the feeders.
Abstract: This paper presents new contributions to the optimization of size and control setting of continuous shunt capacitors on distribution feeders to reduce power and energy losses in the feeders. The current profile is assumed to be a nonlinear function of the distance from the substation, we assume a quadratic function for the current profile. As a result, the loss reduction function to be maximized is a highly nonlinear function, we apply the minimum norm theorem in the frame work of functional analysis optimization technique to maximize this function. A set of linear simultaneous equations is obtained. These equations are solved iteratively using the conjugate-gradient methods. We compare our results with that obtained for a uniform current profile that has been done in the literature. Our contributions show a saving in the size of the capacitors and great loss reductions in the feeder.
TL;DR: In this paper, three digital filtering methods based on frequency-spectral analysis for microprocessor based relaying: unit-combined filters, assigned zero-points filters and narrow band-pass filters.
Abstract: Most protective relaying schemes use single frequency information from transient current/voltage signals to discriminate faults In microprocessor based protective relaying, digital filtering is an attractive method of extracting effective frequency components This paper presents three digital filtering methods based on frequency-spectral analysis for microprocessor based protective relaying: unit-combined filters, assigned zero-points filters and narrow band-pass filters Test results are also presented
TL;DR: In this article, the reluctance series motor (RSM) with electronic commutation having a rotor made of longitudinal laminations with insulations spacers is considered for the scope of direct-axle traction.
Abstract: Direct–axle traction may be achieved with high-specific torque (5–6 Nm/kg), low—loss electric motors. Given the rotor vibration in traction applications, a winding–less rotor would be preferable. The reluctance series motor (RSM( with electronic commutation having a rotor made of longitudinal laminations with insulations spacers is considered here for the scope. The power electronics for commutation of phases and speed control is proposed and tested on a laboratory model. The results are very encouraging but further performance/costs investigations are required before the RSM is established as a practical solution for direct-axle traction
TL;DR: In this article, the authors introduce the concept of time-varying state feedback to inter the desired closed-loop state transition matrix and estimator design, which can be used to design motor control with any desired performance.
Abstract: The concepts of time-varying state feedback inter the desired closed loop state transition matrix and estimator design are introduced in this paper. By introducing the estimation error concept, (i.e. e(t) = x - x) under the assumption that e(t) = = 0(i.e. x = x), the time-varying state feedback (k(t)) and estimator matrix [L] can be designed separately. The motor control with any desired performance can be achieved under the design of time-varying state feedback regulator. Any system with desired performance can be designed in the same.way.