At the recent years, power system becomes a large complex interconnected network that contains of hundreds of buses and generating stations. In addition, to provide the required power, new installation of power generators and transmission lines are required. Due to the environmental and economic constraints of installation of new generators and increasing demands, transmission line flows has been
... [Show full abstract] increased on the existing transmission lines which may increase the risk of losing voltage stability and blackouts in the system. This paper presents an overview on definition and principles of voltage stability. Furthermore, common proposed techniques in the literature to enhance the steady-state voltage stability, such as excitation control and FACTS devices are also addressed.