SERIES COMPENSATION SCHEMES REDUCING THE POTENTIAL OF SUBSYNCHRONOUS RESONANCE

The paper presents new series compensation schemes which reduce the potential of subsynchronous resonance problems in series compensated electrical power systems. The schemes are phase-wise compensation schemes with three different combinations of inductive and capacitive elements. The combinations are chosen such that their frequency characteristics give equal reactances at the power frequency and unequal reactances at the other frequencies. This implies that subsynchronous oscillations drive unsymmetrical three phase currents. The developed electric torque will be, therefore, lower than what it would be if the three phase currents are symmetrical. This results in a lower coupling strength between the mechanical and the electrical systems 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 subsynchronous resonance conditions. The validity and effectiveness of the schemes have been demonstrated on the Second IEEE Benchmark Model, by means of time simulation analysis using the EMTP Program. © 1990 IEEE