Control loops selection to damp inter-area oscillations of electrical networks

This paper reports on results of a study whose objectives is to demonstrate that a systematic, yet straightforward method based on well-known system theoretical analysis tools can be applied to select the control loops which improve the inter-area dynamic stability while minimizing the interactions among local and global controllers. Two complementary measures are involved in the measurement and control signals selection: the geometric measures which allow choice of signal pairs maximizing the controllability and observability of inter-area modes, and the singular-value based total interaction measure which focuses on minimizing the interactions between the local or global loops at the inter-area natural frequency. As a practical illustration of the proposed measurements and controllers pairing scheme, the linearized model of a nine areas twenty three generators power system involving nine inter-area modes is used. The results obtained show that communication links between areas may deem necessary on one hand to improve the inter-area modes observability-controllability and on the other hand to reduce the interaction between the control loops at the inter-area natural frequencies. The usefulness of such an analysis in minimizing the number of communication links without degrading the overall control system performance is highlighted.