SSTI and its mitigation in wind farms connected with an HVDC line

Frequent oscillation occurs at the wind farms of Santanghu District, which are connected to a ±800 kV high voltage direct current line (HVDC). After analysis of the oscillation frequency and its characteristics, it is concluded that the oscillation occurs because of subsynchronous torsional interaction (SSTI) caused by the interaction between the wind turbine generators and the HVDC link. To suppress the SSTI phenomenon, an additional SSTI stabilizer is proposed and installed in Wind Farm 1 of Santanghu. The additional SSTI stabilizer exhibits good performance in mitigating oscillation, with the advantage of low cost and a low additional area footprint.