Comparison of control strategies for multiterminal VSC-HVDC systems for offshore wind farm integration

A study of six different control strategies has been undertaken to determine the most effective control schemes to achieve acceptable operation of multiterminal VSC-HVDC systems. The control strategies analysed are combinations of five types of voltage-current characteristics: DC slack voltage bus, voltage margin, voltage droop, two-stage voltage droop and power-based voltage droop. Transient responses of the DC link voltage and the transmitted power of each grid-side converter are investigated during wind power variations and disconnection of one grid-side converter. Simulation results suggest that the most effective control strategies are voltage droop control and two-stage voltage droop control.