Fast Frequency Control in Multi-Terminal DC Networks

This paper analyzed the frequency support characteristics of multiterminal direct current (MTDC) networks based on voltage source converter technology using the active power transferred from wind farm turbines and other ac systems as recovery power. A control scheme for Multi-Terminal – High Voltage Direct Current (MT-HVDC) to allow redistribution of active power, based on the idea of “power balance” is proposed. The goal of the paper was to ensure frequency deviations to be very minimal and to maintain the frequency around its rated value under normal conditions in the Multiterminal DC section. The control scheme uses droop controllers that were designed through formulation, in order to transfer the recovery power from wind farms to the main grid system which prevented a formation of frequency dips in the AC grid terminals and the entire MTDC system.