Coherency concept to increase the effectiveness of wide-area damping controller

Low-frequency inter-area oscillation is a potentially dangerous phenomenon in large interconnected power systems involving exchange of power among generators in different areas. In recent years there has been an increasing trend towards the use of wide-area controllers for damping inter-area oscillations in power systems. It is found that if wide area signals are applied to the controller design the system dynamic performance can be enhanced and the effect of inter-area oscillations can be reduced. This paper reports on results of a study whose objectives is to demonstrate that one wide-area control loop can be applied on several generators in order to increase the effectiveness of the wide-area controller. The generators are selected based on the coherency concept. Case studies are undertaken on a two-area four-machine power system and the New England 10-machine 39-bus power system, respectively. Modal analysis and time domain simulations are performed to illustrate the feasibility and validity of the proposed schema.