This book mainly concentrates on performing optimal power flow (OPF) in the presence of considered FACTS devices such as TCSC and SVC in their optimal location. Total cost objective functions are formulated by combining FACTS investment costs to the conventional quadratic and non-convex fuel costs to increase the effectiveness of the problem. The proposed problem is solved while satisfying equality, in-equality, practical constraints, and FACTS device limits. While considering the practical constraints, the variation of generators output is also analyzed.