Research On Active Suppresion Of Vibration For Permanent Magnet Synchronous Machine Based Traction Drive System

Achieving emission peak and carbon neutrality is our country’s commitment to the world in the field of energy conservation and emission reduction,which is also a significant way to achieve the construction of lucid waters and lush m ountains.The transportation sector accounts for more than 15% of the country’s total emission and it is one of the three crucial industrial fields for energy conservation and emission reduction at present.The permanent magnet synchronous machine(PMSM)based traction drive technology has advantages of high efficiency and energy saving,high power density,and small size.It has become the preferred driving force solution for electric locomotives,new energy vehicles,military and civilian ships.It is als o of great significance for realizing the energy saving and emission reduction of above mentioned traditional traffical transportation.However,the permanent magnet synchronous machine based traction drive system is a strongly nonlinear coupled system,which will face load disturbances,voltage source inverter(VSI)nonlinearities,cogging torque disturbances and mechanical resonance during the operation and will further introduce harmful vibrations into the system.The harmful vibrations have a great impact on the control performance of whole drive system,and evenresult in damages in equipments.Nevertheless,the conventional passive vibration suppression technology is difficult to realize the early perception and real-time vibration suppression.In response to this problem,three main vibration sources of traction drive system are modeled and analyzed in this thesis,and corresponding active suppression solutions are proposed afterwards.The main work and contribution of this paper is as follows:(1)The structure and mathematical model of the permanent magnet synchronous machine based traction drive system is studied.The potential harmful vibration sources produced by the traction drive system are theoretically analyzed,while the modeling and analysis of harmonic features of three main vibration sources such as the VSI,PMSM,and elastic coupling systems,are conducted afterwards.(2)Aiming to solve the difficulty in the compensation of VSI nonlinearities during the zero-crossing of phase current,a compensation method based on current zero-crossing prediction is proposed in this thesis.Compared with the conventional compensation method,this strategy improves the accuracy of determination of current polarity,so that the accuracy of compensation of VSI nonlinearity is improved.According to the test on an experimental platform,the proposed method shows a good compensation effect under both the traditional vector control and the current predictive control.Meanwhile,it can greatly reduce the current harmonics distortion.(3)Three strategies for suppressing the fluctuation due to cogging torque of the PMSM are proposed.Firstly,a speed error based feedforward compensator for reconstructing the harmonic torque is studied.Since this feedforward compensator needs a long time to converge,an online compensation strategy based on cogging torque map being offline measured is studied in this thesis,which has a faster convergence but relies on the accuracy of off-line cogging torque measurement.In order to overcome the shortcomings of above strategies,a cogging torque suppression strategy based on harmonic analysis of the q-axis current is studied,which does not need additional hardware devices and only needs to extract the harmonic amplitude and initial phase corresponding to the cogging torque frequency in the q-axis current and superimpose them into the reference torque current.Consequently,the real-time suppression of the speed fluctuation caused by the cogging torque can be realized.(4)Aiming to solve the difficulty in the suppression of mechanical resonance of elastic coupling system,suppression methods based on negative feedback of speed and notch filters are both studied in this thesis.Firstly,the characteristics of the above two methods are compared and tested,of which results show that the resonance suppression method based on the notch filter has a simpler parameter tuning process and a faster response speed.Besides,since the key parameter for designing a notch filter is to determine the resonance frequency,three fast resonant frequency identification methods such as the fast sweep frequency method,the resonance frequency identification based on ANF and the cut-off frequency searching based method,are investigated and verified by experiments.The experimental results show that the converge speed of cut-off frequency searching based method is the fastest and whose accuracy is also the highest.Hence,in order to improve the adaptability of the proposed method,this resonant frequency identification method is appli ed for the notch filter based vibration suppression and the experimental verification is carried out under different load-side moment of inertia.The results have manifested that this method can effectively suppress mechanical resonance and also has a good anti-interference performance.