Adaptive backstepping control of grid-connected doubly-fed induction generator during grid voltage dip

Abstract

The most significant drawback of the grid-connected Doubly-Fed Induction Generator is its susceptibility to grid fault due to its stator windings being directly connected to the grid. The stator and rotor of the DFIG are electromagnetically coupled; therefore, the resulting stator current surge during low voltage dip provokes inrush current at the delicate back-to-back converters and an overcharge of the DC-link capacitor. When rotor current and DC-link voltage increase above their predefined 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. Under grid fault, the nonlinear controller is then coupled with active crowbar and DC chopper protection schemes to ameliorate the performance of the DFIG system to ride through fault. Simulation of a 1.5MW wound rotor induction generator under MATLAB/SIMULINK is carried out using the PI-controller (PIC) and Adaptive Backstepping Controller (ABC).