IROGI–PNSE Based Control of Grid-Interactive DFIG Under Unbalanced Network With Wind Power Leveling Capability

Unbalanced grid voltages, appearing at stator terminals of a doubly fed induction generator based wind energy conversion system, deteriorate its performance by instigating unwanted oscillations and distortions in output grid power and rotor currents, respectively, as well as by introducing unbalanced currents in the stator and the grid. This article aims to address these challenges using a coordinated control strategy based on an improved reduced order generalized integrator (IROGI) for positive and negative sequence estimation (PNSE). The IROGI–PNSE further enhances the control performance by eliminating the effects of dc component or unbalance in sensed voltages, on the grid synchronization. The coordinated control strategy uses hysteresis scheme for current control. The hysteresis-based current control requires fewer rotational transformations, and eliminates the need for PI/PIR regulators and notch filters for inner current control loops. This renders the control, computationally efficient. Moreover, the presented system is equipped to exhibit wind power leveling functionality through a battery energy storage. An approach, employing the region-specific wind speed frequency distribution graph, is utilized to constitute the power leveling operation modes. The effectiveness of the control scheme is demonstrated through test results on a prototype developed in the laboratory.