DISTURBANCE REJECTION IN MULTIAREA POWER-SYSTEMS - A DECOUPLING APPROACH

This paper deals with the problem of disturbances occurring in a multiarea power system. Disturbances in power systems, which may be due to the variation of load consumption, area kinetic energy and/or the export of power via tie lines, yield harmful steady-state errors or even instability. It is well known that state feedback can be used to decrease disturbance effects. However, this paper employs the decoupling theory towards this object. It is proved that decoupling of multiarea power systems can be achieved through state feedback alone. Moreover, at least two closed-loop poles for each area can be assigned arbitrarily. Using these results, a general feedback matrix formula is constructed such that the effect of disturbances occurring in any area of the compensated system is completely rejected from other areas. The steady-state error of the voltage angle deviation and tie-line exchange power of the disturbed area are also minimized. Also, the steady-state error of the angular frequency deviation of the disturbed area tends to zero. The presented technique yields a faster steady-state error rate than the interaction-prediction method. It also has the advantage of using local state feedback, so that telemetering is avoided. A practical example of a two-area system with ten states is given for illustration and comparison purposes.