Date of Award


Degree Type


Degree Name

Master of Engineering Science


Electrical and Computer Engineering


Dr. R.M.Mathur


This thesis establishes new guidelines to aid a system planning engineer in the process of improving the small signal stability of power systems. These guidelines help in designing controllers to increase the positive damping of poorly damped or unstable electromechanical modes of oscillations. Design strategies for damping controllers on generators (called power system stabilizers) and on Static Var Compensators (called supplementary controls) are described. The same procedure can be used for designing damping controllers on other dynamic devices like HVDC link, Flexible AC Transmission System (FACTS) elements etc.

In this thesis the particulars of the appropriate system representation and the use of various analysis techniques are treated in detail. Also, in this thesis certain new techniques and innovations to the existing techniques for the small signal stability investigations and design of damping control on a power system are introduced, namely, modal torque calculations, use of voltage participation and observability factors and innovations to the standard pole placement technique of designing damping control to make it more robust.

Modal torque calculations, used to determine in a qualitative and quantitative manner the dynamic interaction between various devices and


their effect on system stability, is shown to be a very powerful for small signal stability studies.

A systematic procedure for the selection of a suitable location to place damping control is presented considering the controllability and observability of the device and feedback signal respectively, for the mode under consideration (the mode whose damping is to be enhanced). The controllability and observability aspects using the well known state participation factors are augmented by the use of a new sensitivity index called the voltage participation factor and a novel method for calculating the observability of a potential feedback signal to the mode under consideration respectively. The effectiveness of this procedure for the selection of a suitable site is validated through a case study of a test system.

The effectiveness of the standard pole placement technique used for the design of the damping control is enhanced from robustness considerations by certain innovations with regard to selecting the new location for the mode under consideration and the constraints placed on the phase characteristics of the damping control compensation network.

The proposed guidelines developed for the generalized procedure of designing damping control is validated through an extensive case study of a 39-bus test system presented in this thesis.



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