Research On High Voltage Ride Through Technology Of Doubly-Fed Wind Power Generation System

In recent years,wind power generation with doubly-fed wind turbines as the main model has been vigorously developed and widely used,and the problem of its grid-connected fault survivability has also become a hot topic for domestic and foreign experts.Among them,the grid voltage swell fault and the grid voltage sag fault are two typical voltage faults in the power grid.At present,the research on low voltage ride through(LVRT)is relatively mature,and the research on high voltage ride through technology(HVRT)is still in its infancy.Therefore,there is an urgent need to study effective technologies to achieve high voltage ride through.In this paper,the control strategy of the dual PWM converter built under ideal conditions usually ignores the situation of grid voltage fluctuations,and an improved control strategy that takes into account the grid voltage fluctuations is designed,and the improved control strategy and traditional control strategy are verified by simulation.Compared with a better control effect.Based on the transient process of the wind turbine in the case of grid voltage surge and the theoretical analysis of the reactive power regulation capability and reactive power output limit of the doubly-fed wind turbine,a high voltage ride-through scheme based on dynamic reactive power support is proposed.Under constant voltage control,by comparing the three typical distribution methods of the simulated reactive power reference command between the rotor-side converter and the grid-side converter,the optimal reactive power coordination control strategy was selected.Considering the limitation of the reactive power output capability of the doubly-fed wind turbine,and the deficiency of the Crowbar protection circuit that is the most used,the control method of the rotor-side series resistance is proposed.The resistance and structure of the series resistance are optimized and theoretically analyzed to determine the reasonable range of resistance selection.On this basis,the HVRT control scheme of virtual resistance is proposed,that is,the control method of the rotor inner current loop is changed.By introducing the virtual resistance Ra,it achieves the same effect as the series resistance on the rotor side,and improves the problem that the dynamic response of the rotor side series resistance protection circuit is not timely.The advantages and disadvantages of the two HVRT schemes areexplained.The work in this paper lays a foundation for further research on the high-voltage ride-through of wind turbines in the case of asymmetrical surge in grid voltage.