Research On Sensorless Direct Torque And Flux Control Of PMSM

Permanent magnet synchronous motor has been widely used in various industrial fields by virtue of its high power density and high efficiency.It is very important to realize high efficiency and high performance sensorless control of PMSM to seize market share.Based on the DTFC closed-loop system,this dissertation takes the high efficiency and high performance full speed sensorless control of PMSM as the research object.The MTPA control of DTFC frame,the disturbance suppression of sensorless control based on active flux and the noise suppression of high frequency signal jection methods are studied in depth.In order to reduce torque ripple and fix switching frequency of traditional DTC,the space vector modulation is introduced to build DTFC closed-loop system.In addition,aiming at the low efficiency and instability of the traditional constant stator flux aplitude reference DTFC,a flux adaptive DTFC is proposed in this dissertation.Firstly,the concept of active flux is introduced,and then the relationship between the optimal current and active flux is theoretically analyzed.On this basis,the optimal stator flux amplitude reference is easily calculated through active flux to run the motor to the MTPA point.The proposed flux adaption DTFC can effectively reduce the additional current used to maintain stator flux amplitude,thus greatly improving the efficiency and stability of DTFC.Due to poor observation accuracy of the traditional stator flux observer,the performance of sensorless control method based on active flux is really deteriorated.Thus,a novel second-order sliding mode flux observer based on the super-twisting algorithm is proposed in this dissertation.Firstly,the influence of disturbance on the traditional sator flux observer is analyzed.Furthermore,the influence of poor observation accuracy on position observation performance is analyzed.Based on the above analysis,the super-twisting alogorithm is introduced to design a stator flux observer,which can accurately observe the stator flux without any amplitude and phase compensation.In addition,it can also improve the performance of sensorless control method based on active flux.At last,the stability of the proposed second-order sliding mode flux observer is proved by Lyapunov function.In order to reduce the harsh noise of the traditional fixed frequency signal injection method,the pseudorandom frequency signal injection method is used to balance the current power density spectrum.First of all,the reason of noise caused by the fixed frequency signal injection method is analyzed by power spectral density analysis of phase current.Based on this,the optimal frequency combination of n kinds of frequency pseudorandom signal injection method is analyzed and the influence of the number of injected frequency on current power density spectrum is compared.Furthurmore,a set of injection frequency selection scheme of the pseudorandom signal injection method is proposed.In addition,in order to realize sensorless control in the full speed range,the position weighted switching method is used to smoothly switch between the zero-low speed range and the medium-high speed range.The correctness and effectiveness of the above algorithms are verified by MATLAB simulation and 60 k W IPMSM experiment on the experimental platform.There are 70 figures,4 tables and 92 references in this dissertation.