Assessing the subsynchronous damping capability of an HVDC link using grid-forming control

The aim of this paper is to introduce simple test systems to assess the damping performance of an HVDC system connected between two asynchronous grids and the subsynchronous oscillation propagation between them. This paper focuses on the grid- forming (GFM) control effect on sub-synchronous oscillatory modes. A GFM control was implemented either one side only or two sides and used to show the HVDC active power response when submitted to AC network oscillations: inter-area modes or rotor angle oscillations. The results demonstrate the capability of the HVDC link to respond to system subsynchronous oscillations providing a positive damping without relying on measurements or external controller.