Supervisory control strategy for optimal integration of direct drive wind turbine to the grid

The main attention of this paper is to improve the integration of wind energy systems to the grid. Therefore, a new supervision scheme for a 2MW direct drive wind turbine is proposed. It aims to satisfy the new Grid Connection Requirements (GCR), where the lowest voltage dip that wind farms must withstand can reach 0% of nominal voltage. The power electronics interface of the investigated wind turbine consists of a back-to-back voltage source converter. The three-level, Neutral Point Clamped topology is used since multi-level converters are suitable for high power applications. Power limitation is achieved by pitch control. Supervision algorithm adapts the control strategy according to the different operating conditions. Thus, wind turbine safety during faults is guaranteed and it can provide ancillary services, necessary for power system stability. Performances are evaluated in terms of accordance with GCR including, low voltage ride-through capabilities, power limitation and reactive power control.