Ride-through and grid support of the DFIG based wind farm during asymmetrical faults

Abstract

Grid codes require wind farm to ride through disturbances such as faults and support the grid during such events. Doubly fed induction generator (DFIG) based wind farm with conventional design has limited capability to ride through severe asymmetrical faults due to low capacity of the rotor-side-converter (RSC). DFIG wind turbine with series grid-side converter (SGSC) can help to extend the operation areas during the fault and satisfy the future grid codes. This paper addresses the capacity design and coordinating control scheme of the SGSC-DFIG based wind farm to ride through the severe asymmetrical fault and support the power grid. Considering the control capability of the RSC and the requirements of the present grid code, the SGSC capacity can be minimized if it is employed to compensate part of the negative-sequence grid voltages. By coordinating the control of SGSC and the DFIG, the positive- and negative-sequence reactive current can be carefully regulated to support the grid and satisfy the code requirements. At the same time, the torsional oscillation of the generator shaft can be mitigated by the negative current control. Simulation results verify the effectiveness of the design and scheme.