This paper describes a new approach to generation expansion planning (GEP) problem to optimise simultaneously multiple objectives such as cost and stability margin. It is formulated as a combinational optimisation problem in order to determine the type and capacity of the new generations as well as their timing and placement. This study presents a comprehensive model of hierarchical optimisation problem to solve the GEP problem. The proposed method has investigated cost index and security margin of voltage stability of power systems by using loadability index. In this new approach, the GEP is done via expansion coordination pattern, and a trade-off between cost and stability has taken place. To solve the modelled optimisation problem, the imperialist competitive algorithm is used and tested on two test (standard) power systems consisting of 30 and 57 buses for a 15-year planning horizon. The results have been compared with hybrid algorithm genetic-particle swarm.
Keywords: generation expansion planning, GEP, static voltage stability, loadability limit, multi-objectives optimisation, imperialist competitive algorithm, ICA