Research On Speed-sensorless Field-weakening Control System Of Asynchronous Motor

As time goes,people’s lifestyle has undergone profound changes.A series of new era products,such as high-speed trains,new energy vehicles and flywheel energy storage,which meet social needs,have entered the historical arena,in which asynchronous motors play a vital role.Asynchronous motor has become the most widely used motor because of its simple structure,low cost,reliable and durable operation and convenient maintenance.Starting from the steady-state model of asynchronous motor,the thesis presents a new field-weakening control method of asynchronous motor with simplified idea,improved precision and deep design for load capacity and efficiency optimization.Moreover,speed-sensorless singlecurrent-regulator field-weakening control system of asynchronous motor is built based on sliding-mode theory for system implement.Field orientation control is generally applied to asynchronous motors in the low-speed range while field-weakening control is required to achieve higher speed.It is necessary to fully utilize the voltage and current under the limit of drive system to increase speed and load capacity.In the traditional field-weakening control system,two current regulators are usually used to adjust the two components of the current in the two-phase rotating coordinate system.However,the coupling relationship between the currents resulting in the insufficient current.In this thesis,a method connecting the stator current coupling relationship with voltage is proposed,and a control system with one single current regulator is designed accordingly,which simplifies the control idea and fully utilizes the current regulator,then load capacity is improved or light-load efficiency is optimized.PLECS simulation and experimental results are given in this thesis,which verifies the effectivity and reliability of the system.At the same time,measurement accuracy of speed sensor is unreliable in high-speed range,and the asynchronous motor requires higher accuracy and robustness for the speed sensorless system.Speed sensorless field weakening control system of asynchronous motor is studied in the thesis.The single-current-regulator-based field-weakening control system of asynchronous motor with sliding-mode speed observer is implemented by DSP.The stability and speed estimation accuracy in high-speed range are verified in simulation and experiments.