Development and field experiments of a generator terminal subsynchronous damper

This paper presents a novel controlling device, named generator terminal subsynchronous damper (GTSSD), to mitigate subsynchronous resonance (SSR) in the power system. The proposed GTSSD consists of a multimodal complementary current calculator (MCCC) and a complementary current generator (CCG). The CCG is composed of a current tracking controller and a power-electronic converter. The rotor speed deviation of the generator is fed back to the MCCC to calculate the current references of the CCG. The outputs of CCG consist of both sub-and supersynchronous complementary current, part of which flows into the generator and creates damping torque on the rotor. The relationship between the control parameters of the GTSSD and the resultant damping improvement is derived. A 10-MVA GTSSD prototype has been developed and tested in an actual series-compensated power system. The experimental results fully demonstrate its ability to enhance torsional damping and to depress subsynchronous oscillation, proving that the GTSSD provides a new and effective approach to solve SSR problems.