Sliding modes control allow for finite-time convergence, precise retention of constraint and robustness against internal and external disturbances. First order sliding mode control demonstrates finite time convergence and robustness against disturbances and uncertainties but exhibits higher frequency switching in control signal which is not desirable from practically design point of view. It is minimized by using quasi stable sliding mode control. In this method signum function is approximated as sigmoid function which reduces the chattering in control signal but with loss of robustness property. In order to maintain the robustness property of controller with chattering free control signal an integral higher order sliding mode control is used. In this thesis the design of higher order sliding mode observer-based integral higher order sliding mode controller for load frequency problems in multi area power system. This method is proposed to estimate all states without the use of costly sensors, results in reduces the cost of overall system with consideration of various types of certain and uncertain disturbances leads to design of overall system more practically and economically. To reduce the mathematical discrepancy between system and mathematical model, Exogenous and Brownian white noise as stochastic perturbation along with uncertain load disturbance is considered. In practice, uneven and abnormal disturbance which are often unpredictable in multi area power system is also taken into consideration. The said design ensures finite time convergence of frequency and area control error under above said disturbances with chattering free control signal. Higher order sliding mode observer estimates all the system states which are difficult to measure or are unavailable. The frequency deviation is found to be within acceptable range under random load disturbance and matched uncertainty confirming robustness of the said design. Further, performance is also observed with power system nonlinearities like generation rate constraints and dead band. The result of proposed method is validated using simulation in MATLAB 2013b.

Keywords : Observer-Based Sliding Mode Control, Nonlinear Systems, Uncertain Systems