Shunt-connected reactors and capacitors controlled by thyristors

Two basic schemes for thyristor-controlled static compensators are described, namely, thyristorswitched capacitors (TSC) and thyristor-controlled reactors (TCR). A more advanced scheme using a combination of TSC and TCR is presented. It is shown that this combination gives a greater degree of flexibility in the designing of a compensator. The paper also briefly describes the control system in a compensator comprising both thyristor.controlled reactors, thyristor-switched capacitors and reactors (TSR). One method to damp power oscillations, using TSC with a certain control strategy, is presented. The problem of unbalanced loads and load balancing methods using TSC and TCR aie discussed. It is shown that the combined system (TSC/TCR) generates very low harmonics, because the TSC does not generate any harmonics. Finally, some pictures from the first installations comprising both TSC and TCR are shown