Unified Smith predictor-based loop-shaping H ∞ damping controller for mitigating inter-area oscillations in power system

Abstract

Low-frequency inter-area oscillation is one of the major problems to transfer the bulk power from one area to another area in an interconnected large power system. A wide-area signal-based controller is more effective to improve the damping of the inter-area oscillation than a local area signal-based controller. A wide-area measurement system makes it easier to transmit the wide-area signal through the communication system from the remote location to the controller site. However, the involvement of the unavoidable time delay in the wide-area signal transmission from a remote area to a controller site is to possess a great deal of challenge to design a damping controller. In this study, a unified Smith predictor (USP)-based loop shaping controller is designed to handle the negative effect of the delay using the wide-area signal. The robust stabilization normalised co-prime factor problem is converted into a generalised H _∞ optimisation problem for additional pole placement constraints. The performances of the USP-based loop-shaping H _∞ controller are compared with the USP-based H _∞ controller. From the obtained results, it is verified that the proposed controller gives an excellent damping performance and handles the effect of time delay.