Research On Low Voltage Ride Through Control Of New Bridge Resistive Fault Current Limiter With Stator Current Feedback

With the use of renewable energy in the field of energy supply more and more,wind power generation has gradually become one of the most competitive power generation with its advantages of clean and efficient.Double-fed induction generator(DFIG)have become popular induction motors in wind power generation systems due to their advantages in price and performance.When the Grid voltage sags,due to the limited capacity of the dual PWM Converter,the over-current and over-voltage phenomenon in the system would seriously threaten the rotor side converter(RSC)and grid side converter(GSC)operation.It can even cause the system to crash.Therefore,it is urgent for countries to conduct in-depth studies on the low voltage ride through capacity of DFIG units from different angles.This article first summarizes the development of domestic and overseas wind power,and analyzes the research status of low voltage ride through technology,reactive power compensation technology and fault limiter.Then this paper elaborates the physical structure and working principle of DFIG,analyzes the wind turbine model and DFIG mathematical model under different coordinate systems.And the structure of dual PWM converter and traditional vector control strategy are described.Then,the causes of rotor side overcurrent and DC side overvoltage phenomenon during the transient state of the double-fed wind power system are analyzed.And aiming at the poor performance of traditional vector control and forward stator current feedback control in the severe voltage sag period,this paper proposes a collaborative control strategy based on the combination protection circuit of the new bridge resistive fault current limiter(NBRFCL)and the reverse proportional stator current feedback is proposed to improve over current and over voltage phenomenon.At the same time in order to speed up the terminal voltage recovery,the grid-side converter proposes to use reactive power priority compensation control strategy to make it send a certain reactive power during the power grid failure.The rationality of the proposed strategy under different voltage sag depths is verified by simulation.The results show that the proposed collaborative control scheme can significantly reduce the peak current of the rotor side and the peak voltage of the DC side,accelerate the dynamic response of the system,and improve the low voltage ride through capability of the system.Finally,the DFIG hardware experiment platform was built,and the real-time monitoring platform of the double-fed wind power system was designed by combining the PXI hardware acquisition system and LabVIEW software.The correctness of the experimental platform and the control strategy of the dual PWM converter was verified by steady-state experiments.