Reactive power rescheduling with generator ranking for voltage stability improvement

In a power system, voltage stability margin improvement can be done by regulating generators voltages, transformers tap settings and capacitors/reactors rated reactive powers (susceptances). In this paper, one of these methods which we name ldquoreactive power rescheduling with generator rankingrdquo is considered. In this method, using ldquoranking coefficientsrdquo, the generators are divided into ldquoimportantrdquo and ldquoless-importantrdquo ones and then, voltage stability margin is improved by increasing and decreasing reactive power generation at the important and less-important generators, respectively. These ranking coefficients are obtained using ldquomodal analysisrdquo. In this paper, the methodpsilas performance for another type of ranking coefficients (which presents ranking coefficient for ldquoallldquo generators) and using IEEE 30 bus test system is analyzed. The simulation results show that in this method, voltage stability margin is considerably improved and, also, the system active loss and the system operating cost are increased.