A novel control strategy is designed for the offshore doubly fed induction generator (DFIG) based wind farm connected to the onshore system through a hybrid high voltage direct current (HVDC) transmission topology. The hybrid HVDC is composed of a modular multilevel converter and a diode rectifier. Detailed analysis is made to prove that the offshore AC-grid voltage can be maintained in a proper range during normal operation. Based on this precondition

a control strategy for the offshore AC-grid frequency and maximum power point tracking (MPPT) of the DFIG is proposed. In order to ensure that the voltage of the HVDC link is lower than its upper limit during the onshore point of common coupling (PCC) short-circuit

the fault ride-through control of the DFIG is also designed. Finally

a digital simulation system of the offshore DFIG-based wind farm and the hybrid HVDC link is established with the effectiveness of the proposed control strategy verified by simulation results.