Enhancement of FACTS stability through robust adaptive control

Adaptive control theory has been recently used in damping the growing oscillations in power systems, enhancing the system response and improving system dynamic stability. This paper proposes a new robust adaptive control mechanism for FACTS. The adopted concept is the dead-zone modification based on model reference adaptive control (MRAC) technique. The developed controller aims to overcome the variation in system parameters and the negative effect of external disturbances that may act on the system by limiting the output error signal, defined as the error in the load terminal voltage, within a prescribed horizontal strip named as the dead-zone. This is achieved by adaptive tuning and optimization of PI controller parameters using quadratic Lyapunov function (QLF) and non quadratic Lyapunov function (NQLF). The case study is a 14^th order state-space model of a power network, equipped with one of the FACTS devices, namely a static VAR compensator (SVC). Developed MATLAB/SIMULINK programs are used to obtain system responses when subjected to a variation in the voltage reference signal of the PI controller. Simulation results for the output error signal are compared while using fixed controller parameters with those obtained when using adaptive loops based on QLF and NQLF. Results obtained verify the validity of the proposed control technique in improving system dynamic performance.