Sliding mode direct power control of RSC for DFIGs driven by variable speed wind turbines

In spite of its several advantages, a classic direct power control (DPC) of doubly fed induction generators (DFIGs) driven by variable speed wind turbines has some drawbacks. In this paper, a simple and robust total sliding mode controller (TSMC) is designed to improve the classical DPC performance without complicating the overall scheme. The TSMC is designed to regulate the DFIG stator active and reactive powers. Two integral switching functions are selected for describing the switching surfaces of the active and reactive powers. Reaching phase stability problem of the classical sliding mode controller is avoided in the proposed TSMC. Neither current control loops nor accurate values of machine parameters are required in the proposed scheme. In addition, axes transformation of the stator voltage and current are eliminated. The grid side converter is controlled based on DPC principle to regulate both DC-link voltage and total reactive power. The feasibility of the proposed DPC scheme is validated through simulation studies on a 1.5 MW wind power generation system. The performance of the proposed and conventional DPC schemes is compared under different operating conditions.