Research On Dynamic Torque Control Strategy Of Brushless Doubly-Fed Machine

In recent years,Brushless Doubly-Fed Machines(BDFM)as a new type of motor has emerged.With its unique stator structure,low-power inverters can be used to control high-power motors in industrial production and life,which greatly reduces the use of cost.In addition to supporting small-capacity variable frequency speed regulation systems,BDFM also have the advantages of adjustable power factor,stable performance and low production costs.On the stator of a brushless twin-motor motor,there are two sets of windings with different pole pairs,namely the power winding(main winding)and the control winding(auxiliary winding).The main winding is a high voltage winding that is directly connected to the mains,and an accessory low voltage winding inverter is attached to the auxiliary winding.Adjust or change the speed of motor by controlling the secondary winding.Due to the particularity structure of two windings,the control of BDFM have certain difficulties and technical requirements.This thesis mainly focuses on the torque control of BDFM in dynamic state,the magnetic field and torque of the motor are detailed,and the vector control strategy based on the motor’s control winding field orientation is proposed.Firstly,the prerequisites for the study and the significance of the topic are systematically worked out,the history of BDFM research and the current status of research in the country and abroad are being worked out,and then the control method of the motor is comprehensively analyzed.Therefore,in-depth analysis and research on the brushless doubly-fed motor as the research object.Secondly,based on the investigation of the design of the stator and rotor of the BDFM,the dependency of the electromechanical energy conversion of the BDFM is analyzed.While modulating the magnetic field of the rotor,two different sets of poles in the motor stator windings will generate different rotating magnetic fields.By analyzing the relationship between each component of the magnetic field in the air gap and the electromagnetic torque of the motor,it simultaneously lays the foundation for defining the motor torque control strategy.Thirdly,taking the magnetic field torque component of the control winding as the research object,the relationship between the mutual inductance magnetic field generated by the equivalent power winding current with the same frequency and the control winding field torque component is analyzed,and the equivalent circuit mathematical model in steady state is established.Through a series of transformations of the coordinates and the orientation of the magnetic field,the magnetic field created by the auxiliary winding current is controlled and the connection between it and the electromagnetic torque through the motor is established,and finally a vector control strategy based on the orientation of the magnetic field of the auxiliary winding is determined.Finally,a vector control simulation model of the brushless doubly-fed motor based on the field orientation of the control winding was built,and the simulation results were analyzed and verified,and conclusion were drawn.