Dynamic behavior analysis and improved fault ride-through control strategy for DFIGs considering the nonlinear arc resistance of grid faults

Doubly fed induction generators (DFIGs) are confronted with fault ride through (FRT) issues during grid faults whose fault path resistance often comprises a transition resistance and a time-varying resistance of AC arcs. In existing FRT analyses for DFIGs, the arc resistance is often simplified to a fixed value, whose nonlinear characteristics have been neglected. This paper quantitatively analyzes the arc-induced distortions in the stator voltage, stator flux and rotor electromotive force. Under a severe arc fault, the impact of the additional arc component on the FRT process is found to be nonnegligible. In view of this unique signature, an improved arc component-based FRT control strategy with proposed flux observation and component separation method is developed for enhancing the FRT abilities from multiple perspectives, including overcurrent suppression, reactive power supply, and power and electromagnetic torque oscillation elimination. The correctness of the analysis and the advancement of the approach are demonstrated on real-time digital simulator (RTDS). The findings provide new insights when developing FRT methods based on the separated components and the approach can be universally applicable to FRT scenarios of DFIGs with notably distorted stator voltages.