Research On Low-voltage Ride Through Control Strategy Of Doubly Fed Wind Farm

With the rapid economic development,wind power has become the most representative form of new energy power generation technology,and double-fed wind farms are the most widely used power generation method in wind power.The core part of a doubly-fed wind farm is a double-fed induction generator.Its stator side is directly connected to the power grid,and the rotor side is connected to the power grid through dual PWM converters.Bidirectional energy feeding.When the grid voltage drops,the stator flux linkage will be distorted,which will cause overvoltage and overcurrent on the rotor side of the doubly-fed induction motor,which will seriously damage the fan and the controller.In response to this problem,many countries have already made corresponding requirements for the low-voltage ride through capability of wind farms.When the grid voltage is faulty,because the stator flux is the integral of the voltage and cannot be abruptly changed,the distortion of the flux will generate overvoltage and overcurrent on the rotor side and accumulate excess energy on the DC side through the rotor-side converter,resulting in The DC bus voltage rises,so the low-voltage ride-through control strategy of the doubly-fed wind farm must be studied.This article first analyzes the structure and working state of the doubly-fed induction motor,and then proposes a new type of demagnetization control based on dynamic demagnetization current and Crowbar protection circuit for cooperative control,thereby improving the low-voltage ride through capability of the double-fed wind farm.Based on the traditional control theory,a new type of demagnetization control based on dynamic demagnetization is proposed and the control is coordinated with the Crowbar protection circuit.A double-fed wind farm simulation experiment platform is built on the MATLAB / Simulink platform,and different control strategies are used for simulation experiments.The simulation results of different strategies are compared and analyzed.When the grid voltage fails,the cooperative control strategy can help the double-fed wind farm achieve low-voltage ride-through.The hardware and software design of the dual PWM converter in the double-fed wind farm is designed,and a functional verification experiment platform based on TMS320F28335 is set up,and a signal acquisition system based on PXI hardware is set up.A steady-state operation platform for a doubly-fed wind farm is set up in the Lab VIEW software system,which realizes real-time monitoring of the doubly-fed wind farm during steady-state operation.Write a signal acquisition program in Lab VIEW system software,and finally verify the accuracy of the design scheme.