Abstract

The manuscript presents a new effective method to damping Sub Synchronous Resonance (SSR) – shaft torsional oscillations for synchronous generators. The proposed scheme with a dynamic 3 φ PWM SSSC and Power Oscillation Damping controller can be achieved damping of SSR oscillation.

This  method is  based  on  using  the  SSSC  to  inject  unbalanced  series quadrature voltages and unbalanced shunt reactive currents in transmission line just after clearing faults.  When the sub synchronous oscillations drive unsymmetrical phase currents, the developed electromagnetic  torque  will  be  lower  than  the  condition  when  the  three-phase  currents  are symmetrical.  The unsymmetrical  currents  result  in  a  lower  coupling  strength  between  the mechanical  and  the  electrical  system  at  asynchronous  oscillations.    Therefore, the  energy exchange between the electrical  and the mechanical systems at sub synchronous oscillations will be  suppressed,  thus,  avoiding  the  build-up  of  torsional  stresses  on  the  generator  shaft  systems under sub synchronous resonance condition.

Keywords:  Torsional Oscillation, SSR Mitigation, SSSC, Power Oscillation Damping controller