Design Of Sensorless Control System For PMSM In Full Speed Range

Permanent magnet synchronous motor(PMSM)has many advantages,such as high efficiency,high power density,wide speed range and fast dynamic response.It is widely used in fan,pump and electric vehicle fields.In order to achieve high-efficiency vector control of permanent magnet synchronous motor(PMSM),it is necessary to acquire the position and speed information of motor rotor in real time.However,mechanical sensors have exist some problems,such as high installation cost,poor signal reliability and poor stability in harsh environment.Sensorless control technology is conducive to improving the reliability of PMSM drive system,simplifying the system structure,reducing the operating environment requirements,and achieving low-cost and high-reliability operation of the motor.Therefore,based on the surface mounted permanent magnet synchronous motor,the sensorless control in the full speed range is studied theoretically and experimentally.Aiming at the problems of low observation accuracy,severe chattering and poor dynamic performance of traditional sliding mode observers,an extended sliding mode observer control method is proposed.The chattering problem of extended sliding mode observers can be effectively improved by feeding back the estimated value of extended back EMF to the stator current observer,replacing the traditional switching function with the switching function and choosing the appropriate boundary layer thickness.At the same time,the position of the rotor is obtained by phase-locked loop with eliminating the influence of rotation,which eliminates the influence of speed variation and further improves the observation accuracy.Based on the analysis of the principle of "torque power angle self-balancing" of permanent magnet synchronous motor,the phase relationship mechanism of I/F control is given put forward,and a composite control method using I/F control strategy in low-speed phase and extended sliding mode observer position estimation strategy in medium-high-speed phase is constructed.A switching method with decreasing current slope is designed to achieve a smooth transition between the two control strategies.When the motor is running at low or even zero speed,it is difficult to extract the position information through the back EMF because of the low content of the fundamental wave of the motor's back EMF.The sensorless control in the full speed range is realized.It solves the problem that when the motor is running at low or even zero speed,it is difficult to extract the position information through the back EMF as a result of the low content of the fundamental wave of the motor's back EMF,and the sensorless control in the full speed range is realized.In order to validate the theoretical analysis effectively,based on the C2000 series of TMS320F28335 digital processing chip of TI company,the hardware design of sensorless control system of permanent magnet synchronous motor in full speed range is made set up,and the experiment is carried out on the towing platform of 2.9kW SPMSM to verify,which verified the validity of the research method.