Frequency-domain modelling of sub-synchronous torsional interaction of synchronous machines and a high voltage direct current transmission link with line-commutated converters

The authors describe a model of a system that includes a high voltage direct current (HVDC) transmission link with line-commutated current source converters (LCC) closely connected to a synchronous generator used to perform analysis of sub-synchronous torsional interaction (SSTI) in the frequency domain. The model of the HVDC transmission link adequately represents the converters in the frequency domain and includes all essential controls for the operation of the converters, including a new sub-synchronous damping control used to mitigate interaction between the rectifier LCC and the shaft of the synchronous machine. The frequency domain model has been validated against time domain simulations showing good agreement.