Hybrid parallel three-level converter topology for large wind turbine generation systems

This paper proposes a hybrid parallel three-level converter topology for large wind turbine generation (WTG) systems and its control method. The proposed topology focuses on a machine side of a back-to-back converter. It consists of one conventional three-level neutral-point clamp (NPC) converter and numerous reduced-part converters, which are connected in parallel depending on rated power of a WTG system. In comparison with a conventional parallel three-level converter topology, in the proposed topology, switching devices are reduced by using reduced-part converters. Moreover, the proposed topology achieves the existing advantages of the parallel converter topology. The reduced-part converter guarantees the sinusoidal current at a particular power factor which does not become a unity power factor. Therefore, a power factor compensation control is performed in one conventional three-level NPC converter to mitigate the disadvantage related with the power factor. The simulation of 2-parallel three-level converters topology is conducted to identify the practicality of the proposed topology and validity of its control method.