APPLICATION OF AN ONLINE CONTROLLER FOR STATCOM TO MITIGATE THE SSR OSCILLATIONS

Abstract

This paper presents an on-line controller for a Static Synchronous Shunt Compensator (STATCOM) to damp subsynchronous frequency oscillations. Series capacitors in transmission lines can increase stability margin and power transfer capability but also result in shaft failure or fatigue in a thermal production unit. Flexible AC Transmission System (FACTS) devices are widely employed to control several features of the power system. Recent surveys demonstrated that FACTS devices, equipped with well-designed controllers, can be effective in damping Subsynchronous Resonance (SSR) oscillations. To achieve this goal, PI controllers are mostly used that are simple controllers. However, they need exact and accurate information about the power system, which is hard to get. Therefore, they lose their desired performance by changing the operating conditions. The proposed on-line controller is based on an identifier and a pole-shifting controller. This controller estimates system parameters on-line and shifts the location of system poles radially with a factor (α) to guarantee the system stability. The considered structure for the system is Autoregressive Moving Average Exogenous (ARMAX) model and the used identifier is Recursive Least Squares (RLS) method. Simulations have been performed by MATLAB/SIMULINK. The eigenvalue analysis has been obtained to study the SSR characteristics of the power system and the studied system is IEEE first benchmark model on SSR.

Keywords

• Adaptive controller
• ARMAX
• FACTS devices
• Pole shifting controller
• RLS
• STATCOM
• Subsynchronous resonance