Voltage security constrained reactive power planning considering the costs and performance of VAR devices

This paper deals with optimal allocation of fast and slow VAR devices under different load levels. These devices are utilized to maintain system security in normal and contingency states, where corrective and preventive controls are implemented for the contingency cases. Load shedding and fast VAR devices are used in the corrective state in order to quickly restore system stability even though they are expensive, while cheap slow VAR devices can be used in the preventive state to obtain the desired security level. The main objective of this paper is to make a trade-off between economy and security by determining the optimal combination of fast and slow controls (load shedding, new slow and fast VAR devices). To meet the desired security limits, a variety of constraints have to be considered during the investigated transitions states. The proposed RPP problem is a combinatorial optimization problem, which cannot be solved easily by conventional optimization methods. Swarm optimization methods are reported to be efficient to solve combinatorial optimization problems. This paper discovers the efficiency of Particle Swarm Optimization (PSO) and Evolutionary PSO (EPSO) in solving the proposed RPP problem. The proposed approaches have been successfully tested on IEEE 14 bus system and a comparative study is illustrated.