Synchronous Machine Parameters Research Articles

Maximum likelihood estimation of synchronous machine parameters and study of noise effect from DC flux decay data

The paper presents an evaluation of the performance of the maximum likelihood (ML) method when used to estimate the linear parameters of a synchronous machine model from the standstill time-domain flux decay test data. It is shown that a unique set of parameters can be obtained and the noise effects can be dealt with effectively when the ML estimation technique is used. The results also show that accurate machine parameters can be identified when the signal/noise ratio is approximately 200:1.

Estimation of synchronous machine parameters from performance relations

The parameters of synchronous machines are required in system analysis, fault calculations, sizing of cables, circuit breaker selection, power factor correction, and voltage drop calculations. One of the major stumbling blocks is the general lack of design and application data. The design information is generally restricted and not commonly available to all users. Furthermore, the parameters are difficult to obtain through field measurements. In this paper, a mathematical model is presented to estimate the parameters of a synchronous machine from name-plate details. The data used in the estimation include output kVA, voltage, current, speed, rated power factor, field voltage, field current, and short-circuit ratio. The equations are derived from a well-known performance model and solved using a spreadsheet program available on any personal computer. Two case studies are presented in this paper. There is reasonable agreement between the estimated and available parameter values. Finally, the usefulness of this procedure and some of the limitations are outlined.

The D.c. Decay Test for Determining Synchronous Machine Parameters: Measurement and Simulation

The d.c. flux decay test has been proposed as an alternative and attractive method of extracting synchronous machine parameters. With the machine stationary, direct current is passed through two phases and the decay of current is observed following the short-circuiting of the supply. Tests on two large turbinegenerators have been performed and simulated by finite element electromagnetic calculations. The combination of tests, calculations and analysis has enabled the cause of various difficulties associated with the test to be isolated. Recommendations are made to improve the accuracy of measurements.

Synchronous machine parameters from sudden-short tests by back-solving

The calculation of synchronous machine parameters from sudden short-circuit measurements has been subject to unnecessary assumptions and approximations. The authors describe the nature of these approximations and a procedure to remove them, and illustrate how a new philosophy for problem formulation and solution using backsolving programs can simplify and clarify the solution process. They introduce a method of calculating eigenvalues that is based on a generalization of the eigenvalue problem. Approximations are unnecessary, and the formulation is much cleaner than in previous efforts. Even for large values of armature resistance, the time constants are correctly computed, since the coupling between axes is considered. >

Synchronous Machine Parameters from Sudden-Short Tests by Back-Solving

The calculation of synchronous machine parameters from sudden short-circuit measurements has been subject to unnecessary assumptions and approximations. The authors describe the nature of these approximations and a procedure to remove them, and illustrate how a new philosophy for problem formulation and solution using backsolving programs can simplify and clarify the solution process. They introduce a method of calculating eigenvalues that is based on a generalization of the eigenvalue problem. Approximations are unnecessary, and the formulation is much cleaner than in previous efforts. Even for large values of armature resistance, the time constants are correctly computed, since the coupling between axes is considered. >

A new algorithm for optimal parameter estimation of a synchronous machine from frequency tests based on LAV approximations

Many techniques exist for estimation of synchronous machine parameters from tests. In these techniques, a good initial guess is essential for convergence of the parameters. This paper presents a new algorithm to estimate synchronous machine parameters from tests. The proposed algorithm is based on least absolute value (LAV) error approximations. It does not require an initial guess, and it is a non-iterative technique. The solution is obtained in two steps. In the first step, the problem is formulated as a linear least squares (LS) estimation problem, as formulated in Reference 2. The solution to this problem yields approximate parameter values. The residual of each measurement is then calculated. In the second step, a number of residuals equal to the rank of the matrix <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> are put to zero. The residuals selected are those with the smallest values. A numerical example from the literature is reported, in which results obtained using the proposed algorithm are compared with those obtained using the standard least squares algorithm.

The DC decay test for determining synchronous machine parameters: measurement and simulation

The DC flux decay test has been proposed as an attractive method of extracting synchronous machine parameters. This test is an attractive alternative to the variable-frequency static impedance test. It is quicker and easier to perform and with carefully chosen short-circuit resistance can give good values for transient and subtransient parameters (although ideally a test is required for each). With the machine stationary, direct current is passed through two phases and the decay of current is observed following the short-circuiting of the supply. Tests on two large turbine-generators performed and simulated by finite-element electromagnetic calculations are reported. The combination of tests, calculations, and analysis has enabled the cause of various difficulties associated with the test to be isolated. Recommendations are made to improve the accuracy of measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of Synchronous Machine Parameters by a Modified Frequency Response Method???Part II: Measured Results

Measurement of Synchronous Machine Parameters by a Modified Frequency Response Method???Part II: Measured Results

Measurement of Synchronous Machine Parameters by a Modified Frequency Response Method - Part I: Theory

De Mello and Hannett [1] have theoretically proposed a method for determining the operational inductances Ld(j2w), Lq(j2w) of a synchronous machine at low values of generator speeds. Eitelberg and Harley [2] extended these ideas to obtain the inductances and time constants from the Ld(j2w), Lq(j2w) curves by a numerical procedure which allows one to attach different levels of importance to either the magnitude or phase fitting of the operational inductance expressions to the computed curves. The first part of this two-part paper extends these ideas [1-2] by proposing an improved MODIFIED data-processing method which uses a Fourier analysis of the open-phase voltage and short-circuit current to compute the operational inductances Ld(j2w), Lq(j2w) and avoids integration of the d,q axes flux linkages; providing that the fundamental and the third harmonic present in the recorded waveforms are considered. The second part [3] of this paper applies the improved MODIFIED data-processing method to a 3 kVA, 220 V microalternator.

Measurement of Synchronous Machine Parameters by a Modified Frequency Response Method - Part II: Measured Results

De Mello and Hannett [1] have proposed a theoretical method for determining the operational inductances of a synchronous machine at low values of generator speeds. Eitelberg and Harley [2] extended these ideas to obtain the inductances and time constants from the Ld(j2w), Lq(j2w) curves by a numerical curve fitting procedure. Part I [3] of this paper broadens these ideas [1-2] by proposing an improved MODIFIED data-processing method which avoids the tedious integration of the d,q axes flux linkages [1]. Part II continues by performing a line-to-line short-circuit test on a 3 kVA, 220 V microalternator at different speeds covering the range which is of interest to subsynchronous resonance (SSR) studies [4]. Measured results illustrate the practical feasibility of this proposed frequency response method [1-3]. Practical problems associated with this test are also mentioned.

Forces and parameters of permanent magnet linear synchronous machines

The determination of electromagnetic forces and parameters of permanent magnetic linear synchronous machines (PMLSM's), based on an evaluation of electromagnetic fields, as reported earlier, is considered. Analytical techniques applied to permanent magnet rotary synchronous machines are modified and adapted to PMLSM's. Fields were determined analytically in a single-sided PMLSM and computed results by the finite-element method were compared with those obtained experimentally in an earlier paper. A good correlation between the results were obtained by three procedures-analytical, finite-element computational method, and experimental. From these field evaluations the PMLSM parameters and performance are obtained.

A Quasilinearization Based Algorithm for the Identification of Transient and Subtransient Parameters of Synchronous Machines

A Quasilinearization Based Algorithm for the Identification of Transient and Subtransient Parameters of Synchronous Machines

A Quasilinearization Based Algorithm for the Identification of Transient and Subtransient Parameters of Synchronous Machines

This paper, a result of EPRI RP 1999-5, presents a powerful identification algorithm and assesses its strength for the determination of the transient and subtransient parameters of the synchronous machine. Quasilinearization, the least-squared-error concept and the transition matrix are used to derive the algorithm. In order for this algorithm to identify parameters, a mathematical structure of the system together with the trajectories of all the input variables and a set of output variables captured during a transient performance of the physical system are required. To assess this algorithm, the rotor speed, field voltage, terminal voltages and currents of a generator for a variety of transient performances are simulated. The simulated trajectories are mixed with various levels and types of noise, and are used as input to a computer program in which the identification algorithm under assessment is incorporated. The mathematical structure selected for the synchronous machine in this program, is one of the most detailed one adopted by many utilities. Values determined for transient and subtransient parameters by the identification algorithm are compared with those employed in the simulation program and hereby the strength of the algorithm is assessed.

Determination of model parameters of synchronous machines

Until now, different assumptions have been made during the determination of model parameters of synchronous machines from the characteristic quantities obtained from measurements (or calculations). This can lead to considerable errors in the results of simulation for certain machines. The paper shows how one can analytically compute these model parameters rigorously from characteristic quantities, without making any simplifying assumptions or iteration. The pertinent additional measurements are given. Comparisons in four examples demonstrate the extent to which the common assumptions can affect modelling a synchronous machine.

Measurements of Synchronous Machines Parameters under Operating Condition

Measurements of Synchronous Machines Parameters under Operating Condition

Synchronous Machine Models by Standstill Frequency Response Tests

An approach to determining synchronous machine parameters by low-voltage frequency response tests with the machine stationary will be described. The tests are simple and safe. In addition, they provide a more detailed and complete model of the machine than the accepted standard methods/1/. The standard tests rely heavily on the measurement of large transients. As such, they are susceptible to any changes in saturation during the course of the measured transient. Furthermore, the accuracy and resolution with which a single transient can be measured are frequently insufficient to provide the detail required to model the solid iron rotor of a turbogenerator. The test method described herein avoids both of these problems as well as providing complete q-axis data which is not done by the standard tests.

Effect of Synchronous Machine Parameters on its Harmonic Analysis Under Thyristor Bridge Operation

This paper investigates the effect of the machine parameters as well as the operating conditions on the waveforms and the harmonic analysis of the various variables of the synchronous machine when supplying a thyristor bridge load. In this regard, a description of the method of obtaining the harmonic analysis of the currents, terminal voltage and electric developed torque of the machine is presented. In the analysis, the machine is represented by a detailed model which takes into consideration the effect of saliency, damper windings and all the machine resistances.

Discussion on “Implementation of new approach to determination of synchronous-machine parameters from tests” and “Prediction of load characteristics of turbogenerators”

Discussion on “Implementation of new approach to determination of synchronous-machine parameters from tests” and “Prediction of load characteristics of turbogenerators”

Derivation of synchronous machine parameters from tests

This paper describes a test procedure for derivation of synchronous machine parameters. The tests can be conducted with ease and without hazard on generators in utility systems. Unlike textbook methods involving short circuit and slip tests which are inconvenient and hazardous, the proposed method involves simple procedures, which can be implemented in normal operation of the machine.