Low voltage ride-through of DFIG wind turbines complying with Western-Power grid code in Australia

Western Power has recently imposed stringent low voltage ride-through (LVRT) requirements on wind power plants that seek connection to the Western Australian transmission system. Doubly-fed induction generators (DFIGs) are the dominant technology used in wind generation systems. However, this type of wind generator is very sensitive to fault conditions and without efficient “ride-through” strategy, continuous operation of DFIG may fail due to destructive overcurrents in the rotor winding or large overvoltages in the dc-link capacitor. This paper introduces a hybrid current control scheme, implemented in the rotor-side converter of DFIG, to enhance its LVRT capability in compliance with the Western Power grid code. The proposed control scheme is constituted of two switching strategies: standard PI current controllers for normal operating conditions and vector-based hysteresis current controllers for DFIG protection during severe fault conditions. Simulation studies are carried out to examine the effectiveness of the proposed LVRT strategy under symmetrical and asymmetrical voltage sags. It is shown that this hybrid control scheme can constrain the rotor current and dc-link voltage within the safety limits of DFIG and as a result, the wind generator meets the strict regulations defined by Western Power.