Transient Stability Improvement via Combined Method

In this article, a combined method is used to improving transient stability. In power systems, the maximum use of existing capacities along with the increased powers transferred through the transition lines make transient stability studies even more important. When the fault occurs, the kinetic energy of system is increased, and if the system kinetic energy exceeds a certain amount, system instability will occur. Generator tripping is one of the most effective methods for improving stability in case of serious faults. In this method, we trip a number of units of a certain power plant unit for stabilizing the system. In fact, by removing the generator, we decrease the kinetic energy of the system so that stability can be achieved. In generator tripping, for the above-mentioned, we should reach stability by tripping the least generator possible. Due to its thermal limitations, fixed place of resistor bank and possibility of back swing, the braking resistor is less efficient than generator tripping. In combined method, system stability against severe turbulence is reached through minimization tripping of generator units. In this method, we first decrease intensity of fault by applying braking resistor, and then, for the purpose of improving transient stability, we try to reduce kinetic energy by removing the least possible amount of producing the desired units at the right time. Simulations on 9-bus or 3-generator system were conducted, and satisfactory results were obtained.