LVRT Control Strategy for Asymmetric Faults of DFIG Based on Improved MPCC Method
Can Ding, Yunwen Chen, Taiping Nie
Abstract
In the case of asymmetric faults, modern new power grids require a double-fed induction generator for the grid-connected operation of wind turbines to still have good low voltage ride-through capabilities. To solve this problem, it proposes a low voltage ride-through control strategy based on an improved model predictive current control strategy in the two-phase stationary coordinate system. First, it analyzes the transient characteristics of a double-fed induction generator and proposes an improved flux extraction method based on the analysis results. The method simplifies the traditional flux linkage measurement link and solves the one-beat delay problem of model predictive control by controlling the step length. Then, the paper also introduces the induced voltage and flux attenuation into the predictive control, which 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, by building a model as a case, it is verified that the control strategy has a good effect on the realization of low voltage ride-through under asymmetric faults. It can achieve the two control goals of self-preservation and support of a double-fed induction generator during low voltage ride-through operation.