Effective protection for doubly fed induction generator-based wind turbines under three-phase fault conditions

Abstract

This paper proposes an effective protection strategy which combines three-crowbar circuit configuration (TCCC), a small bypass resistor (SBR) for wind turbines (WTs) based on the doubly fed induction generators (DFIGs). The TCCC includes (i) resistive crowbar, (ii) inductive crowbar, and (iii) capacitive crowbar. Conventionally, applying only resistive-crowbar circuit as the only means of protection on the DFIG WT, the rotor-side power converter (RSPC) and dc-link capacitor are protected against the effects of a severe voltage dip. However, tripping the RSPC leads to loss of excitation control, and the DFIG behaves like the squirrel-cage induction generator which obtains its magnetization current from the grid which further deepen the terminal voltage. Moreover, integrating the resistive crowbar with series R–L branch keeps the RSPC connection active, but the generator excitation control is partially retained and the oscillations of the rotor currents and dc-link voltage can heavily deteriorate the performance of the generator. Thus, the TCCC-SBR circuit is proposed to compensate for the deficiency when the two conventional circuits are applied. Its performance validation is performed via extensive simulation studies using MATLAB/Simulink software. From the comparative simulation results, more improved fault ride-through capability of the DFIG is achieved with the proposed protection circuit than the conventional protection circuits.