Improvement of small signal performance of multi machine power system using SMIB based PSS and STATCOM designs Bilal Hussain 1 , M.Usman 1 , Affan Ahsan 1 , Ahmad Talha 1 , and Farhan Mahmood 1 1 University of Engineering and Technology, Electrical Department, Lahore, Pakistan gillani_89@yahoo.com, m.usman.64@hotmail.com, affanahsan9@hotmail.com, ahmad.talha.80@gmail.com fmahmood@uet.edu.pk Abstract. This paper discusses the improvements in small signal performance of a multi machine power system under the impact of Power System Stabilizer (PSS) and Static Compensator (STATCOM) devices. Parameters of both devic- es are optimized independently using MATLAB control system tools. PSS lead- lag network is designed using bode plot technique by analyzing Single Machine Infinite Bus (SMIB) based Heffron-Phillips model of network generators. STATCOM voltage regulator is optimized using a reduced STATCOM-Infinite bus model. The proposed designs are tested on a modified IEEE 14 bus system using MATLAB/SIMULINK. Simulations reveal that the system gains an ap- preciable damping ability against local modes of oscillation with PSS employed while STATCOMs increase this strength further. Results have validated the ef- fectiveness of these SMIB based approximate modeling techniques in a multi machine environment where comprehensive system modeling is complex and often require information about whole power system which is sometimes hard to achieve. Keywords: Heffron-Phillips Model, Multi machine system, Power System damping, Power System Stabilizer (PSS), STATic COMpensator (STATCOM), Single Machine Infinite Bus (SMIB) 1 Introduction Generally, whenever a power system is disturbed, synchronizing and damping forces act until the state variables converge back to steady state. Damping forces remain sufficiently strong until the generators are in unregulated condition which is due to two main phenomena [1-3] • Voltage induced in damper windings opposes change in speed. • Rotor flux linkage varies due to accelerating or decelerating rotor causing torque variations proportional to change in rotor speed.