Design A STATCOM supplementary Controller for Stability Studies using various state feedback algorithm N. MAGAJI, A.U. LAWAN, ADO DAN-ISA AND M W MUSTAFA Department of Electrical Engineering Bayero University .Kano and Universiti Teknologi Malaysia Gwarzo Road Kano State and Jahor Bahru NIGERIA and MALAYSIA nmagaji2000@yahoo andwazir@fke.utm.my Abstract: - The authors present a state feedback control approach to the Single Infinite bus Machine in- cooperating a static synchronous compensator (STATCOM). The proposed controllers’ designs are based on a linear time invariant model of the plant and state feedback scheme. First, the linear mathematical model of STATCOM is derived. Then, using polynomial algorithm and pole placement algorithm, a state feedback control law is derived. The proposed control strategy is tested on SMIB system, by digital computer simulations using matlab/simulink program for various types of loads and/or disturbances. Comparison of these results with those methods and without controller establishes the elegance of these control approaches. . Key-Words: - STATCOM, State feedback, damping controller, ITAE and Low frequency oscillations. 1 Introduction Power system oscillations are as a result of lack of sufficient damping torque at the generators rotors .This situation may happen as a result of heavy load in the lines, weak interconnection, high gain excitation systems etc [1]. The oscillation of the generators rotors cause the oscillation of other power system variables such as transmission line active and reactive powers, bus voltage, bus frequency, etc.. Depending on the number of generators involved the frequency of the oscillation is usually between 0.1 and 2Hz [2]. There are several types of oscillations: Local mode, Inter area mode, Control mode and Torsion mode [3]. Many devices can be used as damping controllers for power system oscillation such as Statcom devices, power system stabilizers (PSS), HVDC links, Thyristor controller series capacitor, Statcom etc. PSS is applied on selected generators to damp the local mode oscillation and sometimes inter-area mode oscillation but supplementary controller is better for inter-area mode oscillation applied to the FACTS devices [4]. In most cases the design of these controllers are based on a linearised model which, for wide range of operating points and under large disturbances, will not provide satisfactory performance[4-5]. STATCOM is a voltage source converter FACTS device similar with SVC that is usually used for voltage regulation. It can also be used to improve power system stability by injecting reactive power to the network [6-9]. Evaluation study of STATCOM on stability enhancement has been introduced in [10]. Liner quadratic regulator (LQR) provides an optimal control law for a linear system. It’s a control strategy based on minimizing a quadratic performance index [11]. A wide attention has been directed for investigating the use state feedback controller by different authors like [12-14]. In this paper, a state feedback controller has been proposed for STATCOM supplementary controller. Several algorithms have been utilized for different appropriate operating conditions. Two different models have been taking into considerations (1) Single machine infinite bus and (2) three area five machine system. The remaining sections of this paper are arranged as follows. Section 2 discusses statcom compensating model. The relevant equations for modeling the Statcom current and reactance are derived. In Section 3 an overview of state feedback concepts are discussed. Section 4 details the actual power system model and the results are presented in Section 5. The paper is concluded in Section 6. Recent Researches in Circuits and Systems ISBN: 978-1-61804-108-1 38