Research On Harmonic Torque Suppression Method Of Brushless Doubly-Fed Machine

Brushless doubly-fed machine.According to different control winding power supply modes,it can run in the corresponding mode.Compared with the brushed double-fed motor,its advantages are: the structure is simpler,the brushless makes the brushless doubly-fed motor have strong reliability,and the control winding can adjust the power factor.By providing different control modes for the control windings,the motor can run in the corresponding modes,including: asynchronous mode,synchronous mode,sub-synchronous mode and super-synchronous mode.Both sub-synchronous and super-synchronous are called doubly-fed modes.The control winding is capable of controlling the operating mode of the motor while its power is only a fraction of the total power of the motor.It can both draw energy from the grid and return energy to the grid,which can effectively reduce the capacity of the inverter system.This makes the brushless doubly-fed machine have great potential in the speed control system.It also has excellent potential in other areas,including wind power,hydropower and variable speed constant frequency power generation.The research object in this thesis is the reluctance rotor brushless doubly-fed motor,which needs to solve the torque ripple that exists during operation.On the basis of reading references at home and abroad,the development history of the brushless doubly-fed motor and the latest research status are introduced.By analyzing the working principle of the brushless doubly-fed motor,magnetic field modulation,and electromagnetic power and torque,the mathematical model of the reluctance type brushless doubly-fed motor is established.By analyzing the mathematical model of electromagnetic torque,find the expression of torque in the rotating coordinate system.The main factor of torque ripple is: the power three-phase winding current as the main electromagnetic torque source,containing a large number of harmonic current components.Current distortion affects the stable supply of electromagnetic torque,resulting in electromagnetic torque ripple during motor operation.After obtaining the factor of electromagnetic torque ripple,a method using instantaneous power harmonic torque current detection and a control strategy of real-time power harmonic torque current tracking compensation are proposed to suppress electromagnetic torque ripple.Instantaneous power harmonic torque current detection,and real-time power harmonic torque current tracking compensation key factors are: detection and compensation speed and accuracy.The control strategy adopted in this thesis is hysteresis and SVPWM to ensure the accuracy and real-time of harmonic torque current detection and compensation.The simulation model of the reluctance type brushless doubly-fed motor and the simulation model of the torque ripple suppression control strategy are built.The simulation results show that the proposed method is correct and effective.The core of this thesis is to suppress the torque ripple of the brushless doubly-fed motor during operation.The mathematical model of the brushless doubly-fed motor in the rotating coordinate system is established,and the electromagnetic torque equation under this model is obtained.By collecting three-phase power winding current.The power harmonic torque current detection circuit,power harmonic torque current tracking circuit and power harmonic torque current compensation circuit are designed.The torque ripple of the brushless doubly-fed motor is successfully suppressed.