LVRT Control Strategy for Asymmetric Faults of DFIG Based on Improved MPCC Method

Abstract

In the case of asymmetric fault, the modern new power grid requires that the doubly-fed induction generator (DFIG) still has good low voltage ride-through (LVRT) capabilities. To solve this problem, a low voltage ride-through control strategy based on an improved model predictive current control method in the two-phase stationary coordinate system is proposed in this paper. Firstly, the transient characteristics of DFIG are analyzed, and an improved flux extraction method is proposed. The traditional flux linkage measurement link is simplified by the method and the one-beat delay problem of model predictive control is solved by controlling the step length. Then, the induced voltage and flux attenuation are introduced into the model predictive control method. It can effectively eliminate the double-frequency oscillation component in the DC bus voltage and electromagnetic torque. Therefore, the grid-connected power quality is improved. Finally, an example shows that the control strategy has a good effect on the realization of LVRT under asymmetric faults. The two control goals of self-preservation and support of a double-fed induction generator during low voltage ride-through can be achieved.

Keywords

• Doubly-fed induction generator
• low voltage ride-through
• predictive current control
• flux measurement
• two-phase stationary coordinate system