Research On Low Voltage Ride Through Technology Of Doubly-fed Wind Power System

With the proposal of "3060 Goals",renewable energy represented by wind energy will not only be vigorously developed in the past,but even in the future."The wind in Zhangbei lights up the lamp in Beijing",the rapid development of my country’s wind power industry has helped to achieve the "double carbon" goal of "carbon peaking and carbon neutrality".The increase in the capacity of wind power systems has had an important impact on the power grid.How to improve the low voltage ride through capability of wind power systems in the case of faulty grids is of great theoretical and practical significance.This paper studies the trend of installed capacity of wind power generation in the past ten years,as well as the technical criteria of low voltage ride through of wind power generation at home and abroad,and selects the most widely used doubly-fed wind power generation system as the object.According to its own capacity limitation,the fault ride through capability is weak.The mainstream control strategy improvement and hardware protection measures proposed at home and abroad for wind power generation systems are analyzed,and the fault ride through coordination based on model prediction current control to deal with mild voltage sag and severe voltage sag using Crowbar protection circuit is proposed.Firstly,the mathematical modeling and coordinate transformation are carried out,and the finite control set model prediction is combined with it,and the system based on model predictive current control is proposed.The number of voltage vectors selected in a single sampling period is increased,and the dual-vector model predictive current control scheme is designed considering the influence of the voltage vector action time on the value function.Compared with traditional vector control and traditional model predictive current control,it effectively reduces current fluctuation and torque ripple,and has good steady state performance,which further improves the system’s operating performance under steady-state conditions.Secondly,the transient analysis of system under the faulty power grid is carried out,and an improved model predictive control strategy is proposed that takes into account the transient characteristics of the stator flux linkage,so as to improve the operating characteristics of the doubly-fed wind power system under mild drop faults.At the same time,in view of the severe drop of grid voltage and the large overcurrent generated by the rotor side converter,which exceeds the safe threshold range of the rotor current and is not conducive to the safe operation of the system,a hardware protection measure based on the Crowbar protection circuit is proposed,which is combined with the model predictive control strategy for coordination.It realizes the improvement of the low voltage ride through capability of the doubly-fed wind power system.Finally,the proposed control strategy and hardware protection measures are simulated and analyzed on the MATLAB/Simulink platform for the 2MW doubly-fed wind power generation system.For the high-power wind power system,the low voltage ride through experiment on the traditional experimental platform has the characteristics of certain safety hazards,and the large moment of inertia is not easy to simulate on the low-power doubly-fed induction motor.The hardware-in-the-loop verification is carried out by combining the actual rotor side controller.The relevant results show the effectiveness and correctness of the proposed method.