Nonlinear Controller with Rotor Crowbar and DC-Chopper Fault Ride Through Technique for Grid-Connected Doubly-Fed Induction Generator

Abstract

The most significant drawback of the Doubly Fed Induction Generator (DFIG) 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. In this paper, a robust nonlinear 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). Analysis and comparisons are made for different operating scenarios: speed variation, grid fault, grid fault with protection schemes activated.