Research On Control Of Instantaneous Torque Estimation For Power Windings Of Brushless Doubly-fed Machines

In modern society,with the development of electrical technology,it is well-known that the application of asynchronous motors in practical applications is quite mature.It already has a fairly mature set of control theory.However,the mature theory has not been applied to the emerging brushless doubly-fed motor.The difference between the name of the brushless double-fed machine and the ordinary motor is that it does not have a brush,which greatly reduces the energy consumption of the motor during operation.It is a very significant topic.Power winding supplied by power,control winding supplied by variable frequency power.In this thesis,the reluctance brushless doubly-fed motor and its speed control system are taken as the research object.Combining domestic and foreign references,the development of history and research status of brushless double-fed machine are briefly introduced.The development of modern AC speed regulation is also introduced.The working principle,magnetic field modulation and analysis,power analysis and torque analysis of BDFM are analyzed,which provides a theoretical basis for motor control.Based on the principle of BDFM speed regulation,the principle of direct torque control of BDFM is described.The conventional direct torque control uses a hysteresis controller.And the inverter switch state is selected by the hysteresis controller based on the torque error and stator flux amplitude error.Distortion occurs in current and flux linkage when passing through the sector,resulting in large torque fluctuations at low speed,affecting the control effect of the system.Vector control has higher precision than direct torque control in control effect,but it needs complex calculations such as coordinate transformation and magnetic field orientation,and its operation is relatively complicated.In view of these two problems,this thesis combines direct torque control and vector control to propose a control strategy based on BDFM instantaneous torque estimation,which uses speed PI regulator,torque observer and current controlled inverter.Based on the BDFM instantaneous torque estimation,the current real-time comparison strategy can generate the voltage pulse equivalent to the sinusoidal voltage.This makes the motion path of the magnetic chain closer to the circle.Compared with the traditional DTC control,it reduces the adjustment time when the speed rises,and at the same time,the torque ripple is greatly reduced and strengthens the system's ability to interfere with the load.The steady and dynamic performance of the system is improved greatly.Based on the principle of BDFM direct torque control,the control system circuit was designed.In the thesis,the system's voltage,current,and speed signal acquisition methods are introduced.Through the design of the control system protection system and functions,the motor parameters of the control system simulation are determined.