Design of linear quadratic regulator for SCIG based wind farm to damp SSR oscillations

As the penetration of wind energy to the grid is increasing drastically, the transmission line must be capable of handling large power which demands the series capacitor compensation for the lines. This can result in Sub-synchronous oscillations in the system. This paper explains the detailed mathematical modeling of a Squirrel Cage Induction Generator (SCIG) based wind farm, which is interconnected to the grid through a series, compensated transmission line. The detailed Sub-synchronous Resonance (SSR) analysis has been conducted under various operating conditions such as varying wind penetration levels, varying series compensation levels and varying grid impedance levels. Damping of different modes of SSR oscillations are analysed using the eigen value method. A Linear Quadratic Regulator has been designed for damping of these oscillations. The performance of the system with the proposed controller is analyzed for different operating conditions and the performance was satisfactory.