Frequency regulation participation of offshore wind farm integrated by diode‐rectifer HVDC system

Abstract

Large-scale wind farms integrated with multi-terminal direct current (MTDC) system decouples the frequency between the wind farms and the receiving end, resulting in weakened frequency regulation ability of the onshore AC grid. Recently a new topology is proposed, called diode rectifier based HVDC, which recouples the wind farm and onshore AC system due to its characteristics, where offshore AC voltage changes with the DC voltage of HVDC system. A coordinated power control strategy for frequency regulation participation is proposed in this paper for offshore wind farms connected with diode-rectifier based high voltage direct current (HVDC) system. Considering the primary frequency and inertia response control, variable power supplementary control is implemented in wind turbines, and a telecommunication-less method of frequency event detection via detection of offshore AC voltage is proposed, avoiding communication delay and communication failure. Simulations using EMTDC/PSCAD show that frequency dip can be accurately detected by the AC voltage of offshore wind farm, and wind farm can quickly compensate active power.