Research On Traction Control Strategy Of Permanent Magnet Synchronous Motor For Tram

Tram has a large number of passengers,complex and changeable operating conditions,built-in permanent magnet synchronous motor because of its high power density,wide range of speed regulation,relying on the magnetoresistive torque can obtain the ability to obtain weak magnetic control speed,used in tram traction electric drive system.However,due to the low switching frequency of the traction converter and the low utilization rate of the DC bus,the ordinary motor control strategy and the modulation strategy of the traction converter are difficult to meet the operating conditions of the tram.In this paper,taking the built-in permanent magnet synchronous motor traction system as the research object,the motor vector control strategy and the multi-mode hybrid pulse width modulation strategy of the traction converter under the traction condition of the tram are studied respectively,and the control of the entire traction system is completed.First of all,for the permanent magnet synchronous motor for trams,the output torque is large and the speed regulation range is wide,and the control of the maximum torque-to-current ratio is used in the constant torque area to replace the control of the traditional straight shaft current equal to zero.According to the torque characteristic curve of the permanent magnet synchronous motor,the current trajectory is planned,and the algorithm of feed-forward decoupling compensation combined with the weak magnetic field control of the forward angle is used to make up for the adjustment ability of the maximum torque-to-current ratio in the constant power region,and the dynamic response characteristics of the motor are improved.Secondly,it is aimed at the requirements of low switching frequency and high voltage utilization of traction converters on trams.The multi-mode hybrid pulse width modulation technology is introduced,and the harmonic interference problem of traditional spatial vector modulation is improved by using specific harmonic elimination pulse width modulation combined with spatial vector modulation technology.The cosine term of the even harmonic,odd harmonic and the multiple harmonic of 3 are eliminated,so that the torque ripple is reduced,the utilization rate of the DC bus is increased,the steady-state performance of the motor is improved,and the motor is stably operated in the over-modulation area under square wave conditions.Finally,on the basis of the above theoretical analysis,the vector control strategy of permanent magnet synchronous motor for trams is verified by MATLAB/Simulink simulation platform to improve the torque output ability of the motor and the spreading ability of the weak magnetic field.The hardware experimental platform combined with the software algorithm verifies the optimization effect of the multi-mode hybrid pulse width modulation strategy in improving torque ripple and maximizing the DC voltage utilization rate,and completes the practical research on the traction control strategy of the permanent magnet synchronous motor for trams.