Mechanism Analysis of the Required Rotor Current and Voltage for DFIG-Based WTs to Ride-Through Severe Symmetrical Grid Faults

Doubly-fed induction generator (DFIG)-based wind turbines is prone to suffering from overcurrent during severe grid faults, due to the high electromotive force. To overcome this problem, various fault ride-through (FRT) control strategies are proposed, but they do not theoretically elaborate how to coordinate the rotor current and voltage to ride-through severe grid faults under the limited capacity of the rotor side converter. To fill this gap, a time-domain analysis is presented in this letter. It reveals the fundamental requirements of the rotor current and rotor voltage for DFIG-based WTs to ride-through severe symmetrical faults. Moreover, the analysis results are conductive to understand the existing FRT control strategies and stimulate new FRT method. Finally, the analysis results are validated by simulation and experiment.

I. Introduction

Nowadays, doubly-fed induction generator (DFIG)-based wind turbine (WT) (see Fig. 1) has occupied a great share of the wind energy market [1]. Unfortunately, DFIG is difficult to fulfill the fault ride-through (FRT) requirement of the grid codes, because the rotor electromotive force (EMF) will far exceed the dc-bus voltage under severe grid faults [2]. Fig. 1.

Structure of DFIG-based wind turbine.