Control of an HVdc Link Connecting a Wind Farm to the Grid for Fault Ride-Through Enhancement

This paper studies the issue of the fault ride-through capability of a wind farm of induction generators, which is connected to an AC grid through an HVDC link based on voltage sourced converters (VSCs). National grid codes require that wind turbines should stay connected to the power system during and after short-circuit faults. In the latest literature, when the technology of HVdc based on VSCs is used to connect a wind farm to the power system, the blocking of the VSCs valves for a predefined short time interval is applied, in order to avoid the overcurrents and the tripping of the wind turbines. This paper proposes a control strategy that blocks the converters for a time interval which depends on the severity of the fault and takes special actions in order to alleviate the post-fault disturbances. In this way, the overcurrents are limited, the wind turbines manage to remain connected, and the AC voltage recovers quickly.