A multi-objective gravitational search algorithm based approach of power system stability enhancement with UPFC

Ajami Ali¹, Armaghan Mehdi²

(1. Electrical Engineering Department, Azarbaijan Shahid Madani University, Tabriz 537517379, Iran;2. Young Researchers Club, Ardabil Branch, Islamic Azad University, Ardabil 537517379, Iran)

Abstract:On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robus t UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective func tion comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage devia tion, DC voltage deviation and electrical power devia tion responses are studied with the effect of this flexible AC transmission systems (FACTS) controller. The re sults reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capabil ity in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.

Key words:unified power flow controller; gravitational search algorithm; power system stability