Design and Performance Evaluation of STATCOM Supplementary Modulation Controller in Power Systems

Abstract

Damping of low-frequency electro-mechanical oscillations is essential for reliable operation of power systems. The fast acting, power electronics based FACTS controllers which are capable of improving both steady state and dynamic performance permit enhanced approaches to system stabilization. This paper presents the control laws and location index proposed for a static synchronous compensator (STATCOM) based on a circuit analogy of the electro-mechanical system. The signals which are used can be synthesized using locally available measurements. A detailed study of small signal analysis is carried out to study the effectiveness of the control law and strategic location of the damping controller. With the objective of damping oscillations, a nonlinear constrained optimization technique has been presented for tuning the controller parameters with and without phase compensation. Transient stability analysis has then been performed with STATCOM for a multimachine power system. Comparison of the optimization technique with that of the classical root locus method shows improvement of stability obtained with the former. Case studies on a single machine infinite bus system, three machine system and ten machine systems illustrate the effect of STATCOM on transient stability and its accurate prediction.