A novel FRT strategy based on an analytical approach for PMSG-based wind turbines with ESS power rating reduction

In this paper an analytical approach is proposed to formulate the proper set of phase currents reference to ride the permanent magnet synchronous generator (PMSG)-based wind turbine (WT) through faults properly, regardless of fault type. Hence, the WT is forced to inject required reactive current by grid codes together with active power injection, to help support grid frequency during faults and reduce the energy storage system (ESS) power rating. Moreover, it prevents pulsating active power injection to the grid. During grid faults, the DC-link voltage is controlled by the ESS instead of the grid-side converter (GSC) and the GSC controller applies calculated reference currents. The ESS helps DClink voltage oscillations to be significantly suppressed during the fault. MPCC is applied to handle fast transient states. The main contributions of this paper are first presenting an analytical approach to calculate a proper set of unbalanced reference currents to ride the PMSG-based WT through faults, disregarding grid fault type, while considering phase current protection threshold and second ESS power rating reduction. Different simulations have been carried out to verify the validity of the proposed approach and the efficiency of the whole control system.