This thesis refers to the expansion of the COBRAcable by adding an offshore wind farm converter into the existing point--to--point HVDC link, as envisioned by Cigre. The focus is placed on the examination of the influence of the added terminal into the existing power oscillation damping control function and the tuning of the latter for the expanded three--terminal system. Initially, a simple two--area AC system modelled in DIgSILENT PowerFactory is utilized in order to excite inter--area oscillations in it. The HVDC system is modelled as a half-bridge modular multilevel converter based voltage-sourced converter system. The POD control function is added on top of the converters' main control configuration and the HVDC link is connected to the AC system. The latter is subjected to a disturbance and the POD performance is assessed. Subsequently, the additional offshore terminal is added to the existing PtP configuration with the onshore converters operating under two different control modes, i.e. master--slave and DC voltage droop control mode and its influence into the POD function is examined by varying the output power profiles of the wind farm. Finally, the output of the POD controller is compensated with the aim of improving the damping performance when the converters operate in DC voltage droop control mode.