Research On Power Factor Control Strategy Of Power Winding Of Brushless Doubly-fed Motor

With the increasing demand of high-power variable frequency speed regulation system,the variable frequency speed regulation system composed of brushless doublyfed motor has gradually entered the industrial production.The brushless doubly-fed motor can be driven by a low-voltage frequency converter,and there are two sets of windings on the stator that can be connected to different power sources.The two windings are connected by the mutual inductance magnetic field modulated by the reluctance rotor to realize electromechanical energy conversion.The power factor of the control winding side can be guaranteed by the frequency converter,but the power factor of the power winding can not be directly and effectively controlled,which seriously restricts the application range of the brushless doubly-fed motor speed control system.Taking the power factor of the power winding of the brushless doubly-fed motor with reluctance rotor as the research object,a power factor vector control strategy for the power winding of the brushless doubly-fed motor was established.Firstly,the stator and rotor structure of the motor are introduced in detail.The different wiring modes of power windings and control windings and six different air gap magnetic field components modulated by the reluctance rotor under different operating states of the motor are analyzed,and the different functions of each magnetic field component and the electromechanical energy conversion principle of the motor are obtained.By analyzing the relation of each magnetic field component in the air gap,it lays a foundation for the establishment of power factor control strategy of motor power winding,and also provides a reference basis.Secondly,adjusting the power factor of the power winding of the brushless doublyfed motor is taken as the research objective of this thesis.The connection between the control winding and the power winding is established through the equivalent rotating control winding.Combined with the analysis of the front magnetic fields,the different effects of the magnetic field components of each air gap on the operation of the power winding are obtained.In the six air-gap magnetic field components,there are magnetics field component which has no effect on the operation of the power winding.Therefore,the reactive power of the power winding can be adjusted by adjusting the proportion of the magnetic field generated by the two windings in the excitation field of the power winding.The mathematical model of the power factor of the power winding is established,and a set of vector control strategy of the power factor of the power winding of the brushless doubly-fed motor is established.Finally,based on the above mathematical model and control strategy,the simulation model of power factor vector control system for power winding is built.Through the analysis and verification of the simulation results,it is concluded that the active power and reactive power of the power winding can establish a direct and effective relationship with the magnetic field of the control winding respectively after adopting the control strategy.The simulation results show that the control strategy is feasible and solves the problem that the power factor of the power winding cannot be adjusted effectively.