Multilevel load-frequency control of interconnected power systems

Abstract

This paper presents a two-level optimal control for the load-frequency control of interconnected power systems using modern optimal control and multilevel system techniques. The controller minimises the deviations in frequency and scheduled tie-line power resulting from sudden disturbances. The interconnected power system considered in the paper is decomposed into subsystems each of which has a first level local controller. The local controller controls each subsystem according to the interaction variables provided by a second level controller (co-ordinator). The co-ordinator improves the interaction variables to satisfy interaction feasibility by means of an iteration technique. This paper differs from previous works in that the proposed controller is fast and simple and usually only a few iterations are required. Using the proposed controller the instability problem of subsystems is eliminated. Moreover, the proposed controller guarantees practically zero steady-state error in both frequency and tie-line power at the final time.