Analysis and Control of Offshore Wind Farms Connected With Diode Rectifier-Based HVDC System

This paper analyzes the control and operation of offshore wind farms connected with diode rectifier based HVDC (DR-HVDC) system. A small-signal state-space model of the offshore wind turbines (WTs) connected with DR-HVDC system is developed to design the WT Q-f droop control. The use of WT P-V and Q-f control during individual WT active power variation is clearly clarified. In order to reduce the interaction between WT active power and reactive power, an angle feedforward control is proposed where an additional phase shift is directly added to the WT output voltage based on the WT's active power output. The effectiveness of the proposed control on improving dynamic response and reducing active and reactive power interaction is verified by frequency-domain analysis and time-domain simulations in PSCAD/EMTDC.