Research On Oscillation Suppression Of Electric Vehicle Transmission System Based On PMSM Vector Control

With the progress and development of society,energy saving and environmental protection are gradually becoming the consensus of all mankind.Thanks to the emergence of power electronic devices,pure electric vehicles using electric motors as power sources have become the main research direction of new energy vehicles.Because of the difference in torque output characteristics between electric motors and internal combustion engines,there are also new features in the structure and dynamic performance of electric vehicle transmission systems.As a power source,the torque characteristics of the motor output will greatly affect the dynamic performance of the transmission system.In order to reduce the vibration of the transmission components and improve the comfort and durability of the whole vehicle,from the perspective of electrical control,this dissertation optimizes the motor control algorithm to achieve the vibration suppression of the transmission system.In order to reveal the causes of electric vehicle transmission system oscillations,this dissertation studies the torque ripple characteristics of the motor under vector control,and deduces the torque harmonics introduced by the motor body design and electrical control.The maximum torque current ratio(MTPA)control method is used to simulate the torque ripple caused by the nonlinearity of the inverter(mainly due to the dead zone)to provide conditions for the forced vibration analysis of the transmission system.Model and analyze the electric vehicle transmission system.A centralized parameter branching model based on a two-speed automatic transmission is constructed.In order to analyze the inherent characteristics of the system,through reasonable simplification,the vehicle transmission system is transformed into a multi-body dynamics model,and the free oscillation equation of the system is derived using the D’Alembert principle,and then the natural frequency and mode of the system are obtained.For each natural frequency,the corresponding critical motor speed is calculated to prepare for the subsequent coupled vibration analysis.Deduce the cause of torsional vibration of shafting caused by electromechanical coupling.The forced vibration of the transmission system is divided into two aspects: dynamic response and steady state response.Simulate the steady-state operating conditions at the critical speed of the motor,and discuss the vibration response under steady-state conditions.Simulate dynamic conditions such as rapid acceleration,gentle acceleration and emergency braking,and discuss the vibration of each component when the system is subjected to dynamic shock torque.Combined with the system vibration mode,analyze the influence of transmission system parameters on the forced vibration of the system.In order to weaken the resonance phenomenon of the transmission system under steady-state conditions,starting from reducing the torque ripple of the excitation source-the motor,a harmonic compensation algorithm based on an expanded state observer(ESO)is designed.By compensating the voltage deviation introduced by the nonlinearity of the inverter estimated by the observer in the current loop,the torque harmonics caused by the nonlinearity of the inverter are suppressed,and the suppression effect of the algorithm on the resonance of the transmission system is verified by simulation experiments.Aiming at the oscillation phenomenon of the transmission system under sudden acceleration and emergency braking conditions,a torque observer is designed to use the load torque feedback signal to adjust the output of electromagnetic torque to achieve oscillation suppression.Finally,based on the existing experimental conditions,the algorithm proposed in this dissertation is experimentally verified.