This paper proposes a hybrid system approach to a single machine infinite bus system with a static var compensator (SMIB-SVC). The SMIB-SVC model is represented in terms of a hybrid system capturing the continuous and discrete behaviors of SVC and SMIB. The discrete state of the SVC is controlled by a least restrictive controller to guarantee the system stays in a safety set, and a supplementary controller is used to improve damping of the power system. The proposed approach is exactly describable complex interactions between the continuous dynamics and discrete events in the system. The controller is able to guarantee that the system is working within the safety set in spite of the variations of system's parameters.