Vector Control Of Sensorless Permanent Magnet Synchronous Motor Based On Back EMF

With the continuous progress of the society and technology,permanent magnet synchronous motor has been applied more and more widely because of its unique advantages.Along with the development of permanent magnet synchronous motor and its control system to a certain extent,the application of permanent magnet synchronous motor in AC drive systems is more and more widely,the people have increasingly demand in PMSM’s control precision and dynamic performance.PMSM used the Holzer sensor in the motor rotor position detection before to control the motor,however the external position sensor made PMSM’s structure more complex and too large in the volume,which limits the application of PMSM in the field of precision.So in recent years,researchers pay more attention to the research of sensorless vector control of PMSM and commit to a new drive control of PMSM in sensorless condition.In this way,the new driving mode will gradually replace some old driving mode,which will become a main trend in the future.This paper first introduces the technology of PMSM in control strategy and the development trend of rotor position detection under the sensorless condition.And then introduce the working principle of PMSM and the commutation logic,and the working principle of PMSM based on the back EMF method to obtain the rotor position information,and design back EMF zero crossing detection circuit.Because the detection circuit to determine the rotor position signal includes voltage filter circuit,there will exist delay time,which needs to be compensated in the motor commutation point.Then I establish the sensorless vector control system of PMSM and use adaptive control strategy in the position control.Because the driving module in the motor power requires voltage space vector pulse width modulation(SVPWM),so SVPWM technology and realization method are briefly introduced.In the adaptive control algorithm,the recursive least squares(RLS)has faster convergence speed and dynamic characteristics than the least mean squares(LMS).This paper uses the RLS algorithm as the detection algorithm of adaptive control.Because the forgetting factor of the ordinary RLS algorithm is fixed,it has some defects in the control performance,so the RLS algorithm is optimized and improved.Set up the experimental platform,use the dsPIC33 FJ chip as the control core processor,design the control program with C language,use IGBT as the power switch device,set up the protection circuit,isolation circuit and control circuit,and complete the debugging,experiment and simulation of the vector control system of permanent magnet synchronous motors’ vector control.The results show that the zero position detection based on back EMF method can perfectly determine the position of permanent magnet synchronous motors’ rotor.Through improving the common RLS adaptive control algorithm,the vector control of permanent magnet synchronous motor is optimized.