ROBUST CONTROL OF TCSC COMPANSATED POWER SYSTEM USING LMI APPROACH

Abstract

The electromechanical oscillations present in power system are caused by inadequate damping torque. In modern power system, interconnected generators and long transmission lines further reduce damping torque. Thyrister Controlled Series Capacitor with controller is used to damp these oscillations. Robust output feedback TCSC controller is designed for Single Machine Infinite Bus System and Multi Machine System. Since the performance of the system depends upon closed loop poles, a convex region for closed loop poles is formulated in term of Linear Matrix Inequality. H-infinity norm of the sensitivity function is also formulated in term of LMI for reducing the impact of disturbance on output. These two LMIs are combine into single LMI. Optimization technique is used to solve this LMI. The gamma (infinity norm) plus diagonal element of Lypanov matrix is the performance index. In performance index infinity norm is also added to improve the robustness. The designed controller is tested on linear and non-linear Simulink model of SMIB system. Change in loading condition, mechanical input disturbance, one line outage and 3-phase fault are given to check the robustness of the controller. Different structured disturbances are also given to check the performance of the closed loop system. For multi machine system, the eigenvalues of the system with and without controller is analysed at different loading condition for robust stability. Frequency response of sensitivity in dB is plotted to check the impact of disturbance on output