Frequency support using multi-terminal HVDC systems based on DC voltage manipulation

This study investigates the use of multi-terminal high-voltage direct current(HVDC) systems to provide primary frequency support to connected AC networks via coordinated DC voltage manipulation. Control schemes for multi-terminal HVDC systems to allow redistribution of active power, based on the idea of 'power priority' are proposed. Inertia response from DC connected large offshore wind farms can also be incorporated based on the detection of DC voltage derivation at the offshore converter terminal without the need for telecommunication between the DC terminals. Simulation studies based on a three-terminal HVDC system connecting one large wind farm and two separate AC networks validate the operation of the system during frequency events.