Grid frequency control design for offshore wind farms with naturally commutated HVDC link connection

This paper considers the formal design for the grid frequency control in an offshore wind farm connected with LCC HVDC link. The control paradigm is based on using the grid frequency control to regulate the HVDC rectifier firing angle or DC-link current and hence control the power flow in the system. The dynamic behaviors of the system are verified by comparing the response from derived transfer functions and PSCAD simulations; hence the grid frequency controllers are designed. Good modeling agreement is obtained for both open and closed loop systems and the work provides a good basis for wider research investigation into wind farm operation including fault behavior.