Subsynchronous resonance damping by specially controlling a parallel HVDC link

A previous investigation has shown, in principle, that subsynchronous resonance (SSR) can be damped by adding a HVDC link in parallel with an existing resonating AC line, provided that the rectifier end of the HVDC link is equipped with an auxiliary damping controller (ADC). This paper investigates the feasibility of applying these principles to a newly commissioned SSR prone power station. However, the ADC is modified and extended not only to allow for the transmission of greater quantities of power from the power station to the national grid, but, more importantly, to raise the level of modal damping for the turbogenerator system, thereby reducing its susceptability to subsynchronous resonance and allowing for higher levels of compensation on the existing AC line, and thus, in addition, enhancing the power transfer capability of the AC line.