An Adaptive LVRT Control Strategy for DFIG Considering the Risk of Voltage and Frequency Drop

In view of the problem that the large-scale access of new energy causes the decrease of the equivalent inertia of the power system, the virtual inertia control strategy arises at the historic moment, but the low voltage ride through (LVRT) control strategy applied to fault scenario has not been improved. When the grid fault occurs, due to the traditional low voltage ride through control strategy giving priority to output reactive power, the successful LVRT of large area wind turbines may lead to the transient low-frequency process of the system, and cannot give full play to the advantages of virtual inertia control. At present, there are few literatures that comprehensively analyze the voltage regulation and frequency regulation requirements during fault simultaneously. In order to solve this problem, this paper proposes an adaptive low voltage ride through control scheme that considers voltage and frequency drop risk comprehensively for doubly fed induction Generator(DFIG) with virtual inertia control. Firstly, the lowest point of the system frequency is predicted quickly at the beginning of the fault, and the voltage and frequency reliability evaluation indexes are constructed. Based on this, the reference value of the rotor current is adjusted adaptively to realize the reasonable optimal allocation of wind turbine active power and reactive power during fault, so as to meet the differential demand of wind turbine active power and reactive power in the process of fault ride through and system frequency response. Finally, the simulation model of wind power-thermal power combined system is established in Matlab / Simulink to verify the effectiveness of the proposed control scheme.