Research On Optimization Of Current Loop Of Permanent Magnet Synchronous Motor Vector Control System

With the continuous improvement of the performance,the application range of the permanent magnet synchronous machine becomes more extensive.The strict industrial standards require that the control technology of PMSM has the characteristics of high precision and high dynamic quality.Vector control is a common control method of PMSM.The accuracy of current loop is an important factor affecting the stable operation of the system.In order to improve the control performance of the current loop,this paper optimizes the current loop from three aspects: eliminating sampling noise,compensating measurement error and restraining harmonic current,so as to reduce the speed and torque ripple.In order to reduce the current noise produced by the sampling and conditioning circuit,recursive least square(RLS)adaptive filtering method is used to filter the stator phase current in PMSM vector control system.The RLS filtering algorithm is compared with the least mean square(LMS)filtering algorithm to show its performance.After comparing and analyzing the waveform and mean square deviation value,it shows that RLS algorithm has more obvious filtering effect,and the motor speed and output torque are more stable,while significantly improving the stability of the system.In order to eliminate the gain error and offset error caused by the detection link,the causes of the errors are analyzed,the influence of the errors on the PMSM speed and electromagnetic torque is studied,and the q-axis current compensation is carried out on the premise of the adaptive filtering.By the simulation,it is found that the measurement deviation error and gain error of current will cause the electromagnetic torque and speed to oscillate at twice fundamental frequency and single fundamental frequency.The q-axis current compensation method can reduce the motor speed and torque ripple,as well as improve the stability of the system.The nonlinearity of inverter will lead to high-order harmonics in the current.Therefore,the coordinate transformation method is used to extract the harmonic current in the current loop,and the corresponding voltage harmonics are injected into the voltage feedback to suppress the current harmonics.At the same time,in the simulation experiment,a dead time generation method of inverter is used to generate the dead time,which is the source of harmonic generation.Through the simulation test,it is found that the harmonic suppression method can achieve the high-order current harmonic suppression,thus reducing the torque and speed ripple.