Optimal reactive power dispatch considering multi-type FACTS devices using harmony search algorithms

Optimal Reactive Power Dispatch (ORPD) plays an important role for the secure and reliable operation of power systems. The main purpose of ORPD is to find the settings of control variables such as voltage rating of generators, reactive power injection of VAr compensators and tap ratios of the tap setting transformers in order to minimize the total active power losses of the network while satisfying a given set of constraints. In this paper, Flexible AC Transmission System (FACTS) controllers such as Static Var Compensator (SVC), Thyristor Controlled Series Capacitor (TCSC) and Thyristor Controlled Phase Shifting Transformer (TCPST) are considered in addition with the conventional ORPD control variables for additional active power loss minimization. The whole ORPD problem is considered as a non-linear multi-modal optimization problem. Harmony search algorithm is a recent meta-heuristic algorithm which mimics the musician’s improvization process. In this paper, two versions of harmony search algorithm, namely Basic Harmony Search Algorithm (HSA) and Improved Harmony Search Algorithm (IHSA) are applied to solve conventional ORPD, as well as ORPD considering FACTS devices. Studies on the proposed algorithm are carried out on IEEE 14 and 57 bus systems. Comparison of simulation results reveals the effectiveness of proposed algorithms over other well-established population-based optimization techniques.