The Internal Model Current Control for Wind Turbine Driven Doubly-Fed Induction Generator

Abstract

The doubly-fed induction generator (DFIG) is widely used in the variable-speed constant-frequency (VSCF) wind power generation system with the vector control scheme, which provides good performance in maximum wind energy capturing. In the traditional vector control scheme, the reduced DFIG model, which neglects the stator flux transients, is employed to simplify the rotor current inner-loop controller using the standard proportional-integral (PI) regulation. This scheme works well under normal grid conditions, but when a grid fault occurs, the performance is degraded with rotor over current, and the fault-ride through (FRT) capability of the DFIG wind power generation system deteriorates. In this paper, a full DFIG model, based on the stator voltage orientation (SVO), is proposed to introduce the internal model control (IMC) into the rotor current controllers design. Compared with standard PI regulators, the decoupled capability and robustness against erroneously known parameters of this control scheme were evaluated both analytically and numerically under the normal and fault grid conditions. The validity of the IMC-based regulators for controlling the rotor current and improving the FRT capability of the DFIG wind power generation system is also proved by the simulation results with the magnetic saturation of the generator considered during external grid voltage sags