| In the field of rail transit,the performance and stability of high-power permanent magnet synchronous motor(PMSM)traction system are limited by the application environment,operating conditions and other conditions.To further improve the robust performance of high-power permanent magnet synchronous motor traction system,apply it to more complex working conditions and realize safe and stable operation in the full speed range,there are still the following technical difficulties:(1)In rail transit traction system,the low switching frequency of power devices leads to large motor harmonic and temperature rise pressure,which leads to the poor performance of PMSM under low carrier wave ratio synchronous modulation;(2)The coupling effect of PMSM and the problem of more control parameters and more complex control caused by hybrid PWM method;(3)The control stability of PMSM is affected by the change of motor parameters and external disturbance;(4)In the application of permanent magnet synchronous motor traction system in the field of rail transit,the problems of wide motor operation range,large field weakening area and frequent switching between field weakening control and non field weakening control.Breaking through the above core technical difficulties has certain theoretical and practical significance for improving the control performance and stability of rail transit permanent magnet synchronous motor traction system.In the high-power traction system of rail transit,due to the limitation of heat dissipation conditions of traction converter,the maximum switching frequency is low,and the hybrid PWM method is mostly used.In the low carrier wave ratio modulation region with large motor harmonics,torque ripple and temperature rise pressure,the corresponding synchronous modulation method is particularly key.Aiming at the poor performance of PMSM under low carrier wave ratio synchronous modulation caused by low switching frequency of power devices,a PWM index analysis method based on mathematical model of PMSM is proposed.Two typical modulation methods of selective harmonic elimination pulse width modulation(SHEPWM)and central 60 degree modulation are selected.Analyze the current harmonics and torque ripple indexes of the two modulation methods under different carrier ratios,as well as the advantages and disadvantages of the two modulation methods and the scope of application,which provides an effective basis for the scheme design of traction system.Finally,the application of SHEPWM and central 60 degree modulation in high-power permanent magnet traction system is realized through experiments.The experimental results verify the effectiveness of the PWM index analysis method based on the mathematical model of PMSM.At the same time,the research of low carrier wave ratio synchronous modulation method provides a foundation for the research of high-power PMSM control method.The mathematical model of PMSM is coupled,and the hybrid PWM method increases the complexity of motor control under the constraint of low switching frequency.In order to realize the decoupling control of high-power PMSM and optimize the problem of more control parameters when using hybrid PWM method,a control method of high-power PMSM based on internal model control(IMC)is proposed,which is applied to the field of electric locomotive.Combined with the mathematical model of PMSM,the design of internal model controller is implemented,and the d-q axis decoupling control of motor is realized.Under the premise of guaranteeing the control performance,the control method is simplified,and the application in different PWM methods is realized.Finally,experiments verify the effectiveness of the PMSM control method based on IMC in the application of high-power low switching frequency platform.In the process of PMSM running with the vehicle,the motor parameters will change due to the changes of operating environment and operating conditions,and the model mismatch will inevitably occur.The stator inductance of permanent magnet synchronous motor is easily affected by the stator current,the permanent magnet flux and stator resistance will also change due to temperature,and the external disturbance will also affect the traction system.Aiming at the problem that the control stability of PMSM is affected by motor parameter changes and external disturbances,a control method of PMSM based on IMC with adaptive disturbance observer(IMC-ADO)is proposed.In the process of modeling the mathematical model of PMSM,the changes of motor parameters and unmodeled disturbances are fully considered,The mathematical model of motor current loop considering disturbance factors is constructed,the adaptive disturbance observer(ADO)is designed as an uncertain function,the control law is derived based on Lyapunov function,the gain selection criterion of ADO is obtained through stability analysis,and the ADO is integrated into IMC,the combination of IMC and ADO is realized,and the robustness of PMSM control system is improved.Finally,experiments verify the effectiveness of the vector control method of permanent magnet synchronous motor based on IMC-ADO in the application of high-power and low switching frequency platform.Aiming at the problems of wide motor operation range,large field weakening area and frequent switching between field weakening control and non field weakening control in the application of PMSM traction system in the field of rail transit,an off-line calculation method of current and voltage trajectory of PMSM is proposed,the voltage constraints and current constraints of motor in the operation process are analyzed,and combined with motor parameters and operation conditions,the current and voltage trajectories of the motor in non field weakening control and field weakening control are analyzed,and a motor flux weakening control method based on single q-axis current regulator is studied.The switching strategy between non flux weakening control and flux weakening control is designed to realize the stable operation of PMSM under flux weakening control.Finally,the effectiveness of the flux weakening control method of PMSM based on single q-axis current regulator is verified by experiments,and the stable and reliable operation of high-power PMSM in low switching frequency and full speed range is realized. |
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