Observer-Based Adaptive Backstepping Control of Grid-Connected Wind Turbine Under Deep Grid Voltage Dip

The stator windings of the DFIG are directly connected to the grid. This makes the DFIG susceptible to grid fault in form of short-circuit among the phases. The stator and rotor of the DFIG are electromagnetically coupled; therefore, the resulting stator current surge during low-voltage dips provokes inrush current at the delicate back-to-back converters and DC-link capacitor voltage swell. When rotor current and DC-link voltage increase above their admissible Save Operating Zone (SOZ), rotor converters are damaged and active–reactive power control is consequently lost even after the fault is cleared. In this paper, a robust nonlinear disturbance rejection controller, under the context of Lyapunov stability theory, is first employed to control the Rotor and Grid Side Power Converters under normal grid conditions. Then, an active crowbar and DC-link chopper are designed to be switched on at the detection of grid fault to serve as protection for the turbine. A comparative analysis under MATLAB/Simulink is carried out using the PI-controller (PIC) and Adaptive Backstepping Controller (ABC) for a 1.5 MW turbine.