Optimal Sizing and Allocation of SVC and TCSC in Transmission Network by combined Sensitivity index and PSO

Nowadays electrical power system usually operates close to its maximum load-ability point, because of increasing load demands and contingencies. Thus avoiding voltage collapse and maintaining power system stability are main concerns for power system operators and utilities. Flexible AC transmission system (FACTS) are modern technologies which can increase power system stability, improve voltage profile and can increase real power transfer, by controlling different parameter like impedance, voltage, and angle of power system, however there optimal allocation and sizing in power system network is important to gain maximum benefits and to control power flow in efficient manners. This paper presents a method for optimal allocation and sizing of FACTS devices. Two type of FACTS devices are selected, thyristor controlled series compensator (TCSC) and shunt VAR compensator (SVC). TCSCs can control impedance of the line while SVCs can control bus voltages. For optimal allocation of these devices weak lines and weak buses are determined using Fast voltage stability index (FVSI) and voltage collapse proximity index (VCPI). Lines with higher values of FVSI are considered as optimal locations for TCSC placements, similarly buses with VCPI value close to unity are considered as weak buses and optimal locations for SVC placement. Particle swarm optimization (PSO) with objective to reduce real power losses and voltage deviations is utilized to find optimal rating of these devices. The technique is applied on IEEE 14 bus test system. Results shows significant reduction in real power losses and improvement in voltage profile.