Brushless Doubly-fed Machine Based On Harmonic Current Compensation Method Research On Torque Ripple Suppression

As a new type of AC motor,the brushless doubly-fed motor is very similar to the traditional induction motor in structure,and can operate in asynchronous,synchronous and doubly-fed modes.Compared with the conventional brush doubly-fed motor,this kind of motor cancels the brush and slip ring,and has two sets of windings on the stator side with different pole pairs,so it can’t directly transmit energy.It needs a specially designed rotor winding structure to achieve the purpose of indirect coupling.After rotor modulation,it will form rotating magnetic fields with different rotating speeds and directions.Among them,the existence of harmonic magnetic field can always lead to torque pulsation of the motor,reduce the working efficiency of the motor,and lead to greater motor loss.Therefore,it is of great practical significance to suppress the torque ripple of brushless doubly-fed machine.This paper focuses on the application of brushless doubly-fed machine as a motor in the field of AC speed regulation.The main research contents include the following aspects:Firstly,the basic operation principle of brushless doubly-fed machine is analyzed,and the rotor winding structure design is optimized according to the tooth harmonic principle and double sinusoidal winding theory.The winding coefficient and harmonic magnetic potential of the optimized rotor winding are calculated through programming analysis,and the analytical calculation and simulation results show the rationality of the design method.The magnetic field of brushless doubly-fed machine is studied,and the modulation mechanism of magnetic field is verified by finite element method.Secondly,the mathematical model of brushless doubly-fed machine in the power winding synchronous speed two-phase rotating coordinate system is deduced.According to the expression of torque in rotating coordinate system,the relationship between current and torque is analyzed,and it is clear that the existence of harmonic current component will lead to torque pulsation when the motor is running.Finally,the harmonic compensation current is proposed to counteract the harmonic components generated during the motor operation to suppress the torque ripple of brushless doubly-fed motor.The detection method that can instantly detect the harmonic current of the power winding and the control strategy that tracks and compensates the harmonic current of the power winding in real time are adopted,so that the harmonic current component is compensated and the harmonic torque ripple is suppressed.SVPWM hysteresis comparison control method is used to meet the real-time and accuracy of detection results and compensation effects.Finally,the simulation platform is used to build the simulation model of torque ripple suppression control system of wound rotor brushless doubly-fed motor,and the effectiveness of this method is verified.