Research And Design On Low Voltage Ride Through Technique Of The Grid Connected Doublyfed Wind Turbine

Under the background of the crisis of traditional energy,wind power generation,as a clean and pollution-free renewable energy,has become one of the hot spots of new energy research since its appearance.As the proportion of wind power generation in the new energy system is increasing year by year,the impact of large-scale wind farm failures on the power grid is more obvious.Therefore,countries all over the world have formulated corresponding regulations to protect the safety of wind turbines and power grids,especially requiring that wind turbines must have LVRT capability when the voltage of the power grid falls dramatically.During the Grid-connected operation of DFIG,when the grid voltage drops sharply,a single traditional improved algorithm can improve the fault performance of the system to some extent,but it is difficult to reduce the rotor overcurrent to a specified range and effectively maintain the stability of DC bus voltage,so the wind turbines cannot realize low voltage ride-through under the condition of the grid voltage drops sharply.Aiming at the above problems,on the basis of consulting a large number of literatures at home and abroad,it is found that the method based on the combination of rotor side series resistance and power cooperative control can more effectively realize the low-voltage ride-through of doubly-fed wind turbines when the grid voltage drops dramatically.In the scheme,the rotor side series resistance can consume the excess energy generated by the system,quickly and effectively reduce the rotor overcurrent to the specified range,and at the same time better maintain the stability of DC bus voltage.and the power cooperative control strategy can redistribute active and reactive power on the basis of ensuring the rotor side and the system transient stability,and supplement the grid voltage recovery in time.This paper builds a corresponding simulation model in the MATLAB/Simulink environment and carries out simulation verification and comparison of the low voltage ride through scheme.Simulation and verification results show that the proposed scheme has better transient performance than the traditional single control scheme and improves the controllability of the unit during faults is conducive to the rapid restoration of the grid voltage and the safe operation of other grid-connected loads,making the double-fed wind generators have a fast and efficient LVRT capability under the condition that the grid voltage drops dramatically.