Transient stability preventive control using CCT and generation margin

Power systems have become larger and more complicated. Deregulation of electric power industries has begun in some countries and power system operation is becoming more difficult. But the stability of the power supply is a most important consideration for customers. Therefore power system operators consider not only economic load dispatch but also the on-line stability aspect. In this paper, we pay attention to one of the most important transient stability indices, critical clearing time (CCT), and propose a new transient stability preventive control method using generation rescheduling to satisfy predefined target CCTs. At first, contingency screening is carried out to select severe contingencies that have smaller CCTs than the target CCT. Rescheduled generator outputs are determined using the linear relationship between the generator output at the faulted bus and CCT and generation margins that indicate the surplus generation capabilities of generators. The proposed method is demonstrated using a 9 machine 20 bus system.