Research On Sensorless Vector Control Strategy Of Permanent Synchronous Motor For Fan

Permanent magnet synchronous motors have the advantages of simple structure,small size,large power density,high torque inertia ratio,etc.,and they have been widely used in daily production and life.In some special occasions,the mechanical encoder of the motor cannot be used or its reliability is degraded.To realize the high-performance vector control of the motor,the research on the position sensorless control technology is very necessary.Firstly,this paper introduces the research status of permanent magnet motors in the field of position sensorless control,which introduces three parts of zero-low speed,medium-high speed and position sensorless composite control technology in detail,explaining the significance of position sensorless control technology.At the same time,the structure and mathematical model of the permanent magnet motor are described,and the vector control technology and space vector pulse width modulation technology are introduced.Secondly,in view of the error accumulation and DC offset accumulation caused by the pure integrator,a magnetic flux observer model with a modified vector is designed in the two-phase stationary coordinate system to improve the accuracy of the rotor position observation.A sliding mode observer model was designed according to the sliding mode variable structure control theory,and the phase locked loop was used to estimate the rotor position and speed of the motor.Through simulation comparison and analysis,the magnetic flux observer model with a modified vector was selected as the position sensorless algorithm of the fan system.Thirdly,in order to solve the problem that the magnetic flux observer is not applicable at the zero and low speed stages of the motor,IF open-loop control is adopted to achieve zero-low speed operation of the motor.And two switching methods are designed for switching between zero-low-speed open-loop and medium-high-speed closed-loop control modes of the motor to realize two-way free switching of the motor.Considering that the fan may be in the speed state before starting under the influence of the external environment,the initial speed of the motor is detected by the two shortcircuit current method.According to the forward and reverse of the motor,the corresponding control strategy for starting with the speed is determined,which improves the success rate and safety of the motor control system when starting up.Finally,the hardware platform of the sensorless field oriented control system of the permanent magnet motor is set up,the corresponding software program is designed,and the relevant sensorless algorithm of the motor is verified by experimental experiments,which proves the stability of the proposed control algorithm,reliability of the switching methods and effectiveness of the starting strategy.