Suppression of transmission system oscillations by thyristor-controlled series compensation

The role of a variable series compensator in a multimachine infinite-bus system is investigated. The proposed compensator a combination of thyristor-switched (TSCs) and a thyristor-controlled reactor (TCR). The role of the TSCs is to suppress large power oscillations while that of the TCR is to damp out small power perturbations. A performance index to quantify the overall power imbalance in the system is proposed and is used to formulate the control strategies for the TSCs and TCR. The coordination between the control actions of the TSCs and TCR is established on the basis of the magnitudes of the power oscillations. Computer simulations show that the proposed scheme is effective in suppressing power flow oscillations in transmission networks.