Now days due to the increase in load demand, in the interconnection of the power system, load as well as power flow in tie-line are varying dynamically. So there is a need of robust control of both systems frequency and tie-line power flows. This robust control can be attained using fuzzy logic controller rather than the conventional proportional integral and proportional integral derivative controllers. Because gain values of conventional controllers are constant, for load changes. Load can't

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... e constant, load changes time to time but gain values of conventional controllers are constant. In order to overcome the drawbacks of the conventional controllers, many techniques have been proposed in literature. A new load frequency control (LFC) for multi-area power systems is developed based on the direct-indirect adaptive fuzzy control technique. LFCs for each area are designed based on availability of frequency deviation of each area and tie-line power deviation between areas. The fuzzy logic system approximation capabilities are exploited to develop suitable adaptive control law and parameter update algorithms for unknown interconnected LFC areas. An H∞ tracking performance criterion is introduced to minimize the approximation errors and the external disturbance effects. The proposed controller guarantees stability of the overall closed-loop system. Simulation results for a real three-area power system prove the effectiveness of the proposed LFC and show its superiority over a classical PID controller and a type-2 fuzzy controller. INDEX TERMS-Adaptive fuzzy control, fuzzy approximation, GDB, GRC, load frequency control (LFC), multi-area.