Offshore grid frequency control design for line-commutated converters high-voltage direct-current link connected wind farms

The design for the grid frequency control in an offshore wind farm with line-commutated converters high-voltage direct-current (HVDC) link connection is considered. The control paradigm is based on using the local grid frequency control to regulate the HVDC-link current and hence control the power flow in the system. The derived dynamic equations form the basis for the design of the grid frequency controller. The mathematical analysis and the control design are verified through PSCAD simulations. Good modelling agreements are obtained for the closed-loop system, and the work provides a good basis for wider research investigation into wind-farm operation. The operational conditions and ride through of the worst-case short-circuit fault in the receiving end AC system are investigated.