Thyristor-controlled phase-shifters for AC transmission

A novel scheme for four-quadrant thyristor-controlled static phase-shifters is presented. The technical feasibility of the proposed phase-shifter for damping power system torsional oscillations is examined. An optimization procedure is introduced to obtain the maximum damping for power system oscillations, by determining the optimum phase angle and magnitude of the phase-shifter out-put voltage. An eigenvalue analysis method is used to investigate the damping effect of the phase-shifter on the torsional phenonenon. The studies are performed on the first IEEE benchmark for SSR studies. The analytical results are verified by detailed digital computer simulation studies, using the BPA´s Electromagnetic Transients Program (EMTP). The investigation results demonstrate the technical feasibility of the four-quadrant phase-shifter for damping the torsional oscillations, as a result of small signal disturbances.