Transient stability improvement of a DFIG-based network-connected wind power plant by control of the flux neutralization current during the voltage drop

Abstract

In order to protect a doubly fed induction generator (DFIG) against voltage drops, it is essential to maintain its transient stability. The passive "crowbar and dc-chopper" technique has been employed to protect DFIGs. However, it may not be sufficient for some of the transient profiles. For this reason, the Low Voltage Ride Through (LVRT) has been employed by implementing Control of Flux Neutralization Current (CFNC) for transient response assessment. Moreover, the induced electromotive forces (IEFs) in both circuits (stator and rotor) were modeled on the DFIG, and the comparative performance of the DFIG models with and without CFNC was examined. The system behavior was examined for symmetrical three-phase faults, considering the cases with and without the stator/rotor coupling dynamics. This study uses numerical modeling and time-domain simulations with MATLAB/Simulink to analyze the transient behavior of the DFIG system under fault conditions. No experimental tests have been carried out, and future work will aim at a real-time implementation to assess practical feasibility. DFIG quantities were analyzed and compared, including 0.69 kV output voltage, mechanical speed response, electromagnetic torque variations, rotor and stator direct quadrature (d-q) axis currents, 22 kV bus terminal voltage, and, a DC-Link voltage. The results reveal that CFNC reduces the duration of oscillations by more than 50%, stabilizing currents in 1.18 s instead of 3.5 s and the DC-Link voltage in 1.1 s instead of 3.5 s, significantly improving LVRT capability and transient stability.