An Adaptive DC-link Voltage Control for Doubly Fed Induction Generator Wind Turbine System

This paper presents an adaptive DC-link voltage control for Doubly Fed Induction Generator (DFIG) wind turbine. Generally, DC-link voltage reference is constant which lead to DC voltage rise and oscillations during sag. A hardware is also used to enhance low voltage ride through (LVRT) and protect the rotor converter from overcurrent's. However, during the converter start-up and transients time, the dynamic decoupling of the converter is no longer valid. The inner and outer loop interact as a consequence the controller design by linearization cannot guaranty the expected performance. In order to enhance the system transient response and avoid DC voltage rise during the dips, an adaptive DC-link voltage control is proposed. In this method, the DC-link voltage is controlled to follow the change of grid voltage and its reference is calculated from the grid voltage taking into account the voltage drop across the grid filter. As the result, the current and voltage ripples are significantly attenuated and transient Vdc response is improved. Also, this control strategy allows avoiding activation of protective equipment for faults up to 70% of voltage deep. The simulation performed by Simulink software demonstrates the effectiveness of the control strategy.