Enhanced Low-Voltage Ride-Through Capability of DFIG by Explicit Model Predict Control Based Decoupled Virtual Impedance

Abstract

The power grid requires doubly-fed induction generators (DFIGs) to effectively suppress rotor currents and provide reactive power support during low voltage ride-through (LVRT) events. However, traditional virtual impedance methods struggle to flexibly coordinate different control objectives under various fault conditions, thereby failing to fully realize their control potential. To address this, this paper proposes a decoupled virtual impedance control strategy. Virtual resistance and inductance are independently designed to suppress zero-sequence and negative-sequence overcurrents, achieving effective overcurrent mitigation. Furthermore, explicit model predictive control (E-MPC) is employed to dynamically adjust the virtual impedance values, enhancing the LVRT capability of DFIGs. Additionally, the E-MPC cost function incorporates reactive power support to coordinate current suppression and voltage support. Since the control law of E-MPC is designed offline, the online computation time can be greatly reduced. The proposed strategy is verified by 1.5 MW DFIG model in Matlab/Simulink and experiment. Results show that LVRT performances under diverse fault conditions have been significantly improved.