This paper reviews experience in the control design and tuning of power system stabilizers for thermal generating units. Special problems encountered in obtaining satisfactory performance at a particular generating station due to specific generator characteristics is highlighted. Analytical techniques used for establishing suitable stabilizer settings are described and their effectiveness in duplicating field measurements is demonstrated

Power System Stabilizers for Thermal Units: Analytical Techniques and On-Site Validation

Adaptive nonlinear excitation control of large-scale power systems is considered in this paper. The approach used is an adaptive feedback linearizing control to enhance the robustness to unknown or varying interconnection parameters like equivalent reactances of the transmission lines. Control design based on external feedback linearization may not be robust to handle varying power-system configurations. Inexact cancellation of terms due to uncertainties may result in performance deterioration like inter-system oscillations. Adaptation in estimated parameters is utilized to achieve an asymptotically exact cancellation of terms. It is shown that the adaptive control results in bounded states and maintains the desired performance. The control scheme developed is applied to a power system with two generators and an infinite bus connected through a network of transformers and transmission lines. Simulation studies for unknown interconnections arising due to faults and subsequent line switchings in the transmission network are carried out. The performance using the nonadaptive feedback linearizing control is shown to degrade for network configuration variations arising due to transmission line faults. The response obtained using the proposed scheme is compared with that using a conventional IEEE Type I excitation control. The studies validate the fact that connective stability and robust performance is maintained for unknown interconnection topology using the adaptive feedback linearizing scheme. >

Adaptive nonlinear excitation control of power systems with unknown interconnections

A novel technique for deriving direct and quadrature axis equivalent circuit models of turbogenerators from standstill frequency response measurements is proposed. This technique differs from that proposed by previous investigators, and results in better representation of rotor body effects, particularly in the d-axis. This new method is applied to results of measurements on three large turbogenerators of similar rating but different rotor construction.

Development of Detailed Turbogenerator Equivalent Circuits from Standstill Frequency Response Measurements

Some applications of synchronous machine models with a desired structure require parameter values which are frequently not readily and satisfactorily obtainable from design data or field tests. An iterative algorithm based on weighted-least-squares estimation theory is proposed to determine directly all standard parameters for a hypothesized model structure by repeatedly processing the armature and field current data of a sudden short-circuit test. Results for a simulated salient-pole synchronous machine with damper winding are included, where the parameters X d , X' d ,X'' d ,X l , X q , X'' q , R a , T' do ,and T'' qo are readily identified in a few iterations with high accuracy.

A weighted-least-squares parameter estimator for synchronous machines

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.

Synchronous Machine Models by Standstill Frequency Response Tests

Models of a synchronous machine for use in stability studies have been derived by measurements off-line at standstill. The method involves accurate determination of magnitude and phase of the impedance as seen at the stator terminals, for a range of frequency from 0.005 to 100 Hz. The data obtained pertains particularly to establishment of parameters for equivalent rotor circuits of varying degrees of complexity.

G. Manchur

Papers

Synchronous Machine Operational Impeadances From Low Voltage Measurements at the Stator Terminals