Low-Voltage Ride-Through of a Synchronous Generator-Based Variable Speed Grid-Interfaced Wind Energy Conversion System

Wind energy conversion systems (WECSs) based on synchronous generators devoid of rotor windings, such as permanent magnet synchronous generators and synchronous reluctance generators, have become popular due to their maintenance-free operation. As per grid codes, WECSs ought to stay connected, at least for a short while, to ensure reliability and stability, even if there is a fault in the grid. There are various techniques proposed in the literature, for implementing low-voltage ride-through (LVRT). This article explores a few methods for achieving LVRT for a synchronous machine-based WECS connected to the grid through a back-to-back connected full-rated converter. The machine-side converter is controlled by field-oriented control methodology to drive the generator at an optimum speed to harvest maximum power from the wind turbine. The grid-side converter makes use of the grid-voltage-oriented control algorithm to achieve decoupled control of real and reactive powers. The LVRT capability of the system is attained using four different control techniques, namely modulation index (MI) control, deloading, crow-bar protection, and interchanging the roles of the two converters to arrest the rise in dc-link voltage. These methods have been simulated in Simulink/MATLAB environment, and the results obtained show that these techniques work very effectively for realizing LVRT in a synchronous machine-based WECS. Finally, experimental results are presented to demonstrate the successful working of the maximum power point tracking algorithm and LVRT capability on a laboratory prototype; a comparison of LVRT techniques is presented to enable the users to make an informed choice.