| Due to the characteristics of the single-phase rectifier in the EMUs electric drive system,the DC link voltage contains a pulsating component whose frequency is twice of the grid's.Under the influence of the pulsating component,the loss increases,the heating and the mechanical jitter problems appear in the motor.The dissertation does research on the secondary pulsation of DC voltage in EMUs.It proposes a strategy applied to traction motor control to suppress the effect caused by secondary pulsation.The effectiveness and feasibility of the strategy are being verified by theoretical analysis and simulation.The mechanism of secondary pulsation and the topology mathematical model of main circuit are studied.Through the analysis and calculation of the key components of the main circuit,the mathematical model of the main circuit is derived.And the model that can be used for MATLAB simulation and HIL is constructed.The accuracy of the model is verified by comparing with the ideal model in MATLAB.The generation and influence mechanism of DC voltage secondary pulsation are deduced and verified by simulation.The basic suppression strategy of secondary pulsation is studied.In this dissertation,the frequency domain analysis of the motor is carried out,and the suppression strategies of the secondary pulsation influence on low frequency band and high frequency band are studied respectively.Combining motor vector control,this dissertation analyzes two key problems that is pulse width modulation and pulsating voltage sampling.On the basis of the main circuit model of traction drive system,the motor control program is written,and the motor vector control method under the secondary pulsation of DC voltage is studied.The suppression strategy optimization of traction motor under pulse-width modulation with full speed range is studied.This dissertation introduces and deduces the method of pulse width modulation at different operating speeds.The effect of DC voltage secondary pulsation on pulse width modulation and the effect of suppression strategy are analyzed.Combining the suppression strategy,simulation model and control program,the program of pulse width modulation in full speed range is written,and the application of suppression strategy in motor is optimized.The DC voltage sampling of suppression strategy at low switching frequency is studied.The defects of direct sampling are analyzed.The internal model in repetitive control is improved.Analyze and calculate the improved parameters,and determine the form and parameters of compensator.A periodic voltage prediction model based on repetitive control is constructed.The prediction effect and motor control effect are verified by simulation.Figures: 75,Tables: 1,References: 57. |
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