Advanced LVRT Control Scheme for Offshore Wind Power Plant

Offshore wind farms (OWF) are being rapidly integrated to the power systems, which can be primarily attributed to saturation of the mainland onshore area, and high wind speed in offshore sites. However, to maintain stable grid operation, OWFs are required to comply with Low Voltage Ride Through (LVRT) capability. OWF during LVRT period should not only stay grid connected, but also support the grid during the disturbance. In this paper, a new communication-independent LVRT control scheme for HVDC connected OWF has been proposed. Under the proposed strategy, OWFs not only successfully ride through a fault induced voltage dip, but also comply with active power recovery ramp rate during the fault recovery period. Besides complying with LVRT requirement and ramp rate limit, the proposed strategy improves voltage dip induced frequency (VDIF) issue by increasing active power injection from the OWF during LVRT period. The proposed LVRT strategy also exploits the stored energy in HVDC link capacitors in order to reduce the impact of VDIF issue. The proposed and the conventional LVRT strategies for HVDC connected OWF have been implemented and evaluated on IEEE 39 bus benchmark system.