Probabilistic Contingency Severity Index for Dynamic Reactive Power Planning

Planning of Flexible AC Transmission systems (FACTS) and other reactive power sources has traditionally been done considering steady state conditions. The strength of FACTS is mainly seen when considering the dynamic behavior after the occurrence of any disturbance like when a fault occurs, because they can stabilize the system voltage and control power flow. At the same time, transient voltage dips and slow voltage recovery issues are most effectively addressed by fast responding dynamic VAR sources. So, this paper proposes a probabilistic contingency severity index based on the probability of occurrence of the faults and the dynamic impacts on the network measured in trajectory voltage deviations that can be included as a dynamic constraint for reactive power planning. In this way, the objective of dynamic reactive power planning is to determine where and with what capacity shunt-FACTS should be located to obtain a voltage profile within acceptable limits. The proposed probabilistic contingency severity index shows its effectiveness as dynamic criteria for optimization of location and sizing of shunt-FACTS devices by testing on the IEEE 9 nodes system and on the IEEE 39 nodes system.