© 2019 IEEE. A supplemental controller for static var compensator (SVC) is developed for the voltage regulation in a power system. The control objectives are to suppress voltage fluctuations and to maintain voltage at nominal levels in different parts of power system within ANSI C84.1 limits (or ±5 % tolerance). Voltage fluctuations are mainly caused by disturbances such as random power load changes and loss of major equipment. These disturbances degrade voltage/power quality and could lead to catastrophic voltage collapse and black out. SVC itself can regulate voltage flicker but its robustness against the disturbances is inadequate. Therefore, an active disturbance rejection controller (ADRC) is applied to the SVC system for enhancing its performance. The ADRC is independent of the accurate mathematical model of the SVC system and able to compensate for external disturbances in real time. An ADRC is implemented on the power system with SVC in Simscape Power Systems. Simulation results demonstrate that the ADRC reach the control objectives successfully, and have superior performance to PI controller in disturbance rejection. In addition, the stability of the control system is justified. The comparison between both PI and ADRC is discussed.