Nonlinear Hybrid Flatness Control for Suppressing Overcurrent of Dfig During High Voltage Ride Through

Abstract

High voltage ride-through (HVRT) technology plays a crucial role for the security and stability of of doubly fed induction generator (DFIG). The HVRT capability can be enhanced by suppressing the inrush transient overcurrent and reducing their duration time in the stator and rotor. To dealing these challenges, a nonlinear hybrid flatness control (NHFC) is proposed, which consists of three parts: 1) a differentiate flatness control (DFC) strategy is designed for improving the dynamic response performance of the overcurrent. 2)a time-based virtual resistance control (TBVRC), which adopts the resistance varying with the fault voltage occurrence time, is employed to regulate and suppress the stator and rotor overcurrent. 3) Considering optimum droop coefficient calculation, a coefficient backpropagation droop control (CBDC) is developed to provide outstanding reactive power injection for voltage support. Simulation results and comparisons with the existing control strategy show the correctness and effectiveness of the proposed NHFC.

Keywords: High voltage ride-through (HVRT), doubly fed induction generator (DFIG), differentiate flatness control (DFC) strategy, time-based virtual resistance control (TBVRC), coefficient backpropagation droop control (CBDC)