Gradual Developments in the Area of Automatic Load Frequency Control

Large power systems are normally divided into control areas based on the principle of coherency. The coherent areas are interconnected through tie lines which are used for contractual energy exchange between areas and provide inter area support during abnormal condition. A mismatch in the real power balance affects primarily the system frequency but leaves the bus voltage magnitude unaffected. The problem of real power balance in a power system is termed as automatic load frequency control problem. The main functions automatic load frequency control are (a) Frequency to be maintained constant i.e at 50 Hz (b) the tie line power to be maintained between specified limits and (c) the economic operation of the generators. If the above parameters are maintained with in desired limits the generation control is said to be most effective. The present work deals with the literature review of automatic load frequency control during last four decades and its possible scope of future work.