Research On Suppression Of Electromagnetic Noise And Optimization Of Power Loss Control In Traction Drive System

Rail transportation is one of the essential transportation modes in China’s transportation system,which plays a crucial role in economic and social development.As the core of train power,the traction drive system can be affected by certain inherent problems and aging of key components during long-term operation.And this can result in a significant reduction in the indicators and synergy performance of the system the failure of key components,which will pose a serious threat to the safe operation of trains and passenger comfort.At present,excessive electromagnetic noise,IGBT life loss,and common-mode voltage effects are three main problems in traction drive systems.In order to solve the proposed problems,this thesis mainly researches electromagnetic noise suppression,IGBT life loss optimization and common-mode voltage suppression strategies in train traction drive systems.The main research contents of this thesis are as follows:Firstly,the main components,working principles,mathematical models and related control strategies of the train traction drive system are introduced in detail.Moreover,the problems of electromagnetic noise overload,IGBT lifetime loss and common mode voltage of dual threephase motors in traction drive systems are analyzed in depth from the root cause.The main cause of motor noise is the resonance between the electromagnetic forces and the intrinsic modes of the motor,caused by harmonics.This problem can be optimised in terms of harmonics and motor modes.Common mode voltages are caused by the drive topology and modulation strategy.From this point of view,if the topology can be improved and zero-voltage vector control can be avoided,the commonmode voltage can be effectively suppressed and its effect reduced.In addition,for the IGBT lifetime loss problem,if the number of power cycles can be reduced by certain control optimisation strategies to meet the traction power requirements during train operation,the IGBT lifetime can be effectively extended,thus achieving the goal of optimised traction converter loss control.To solve the problem of excessive motor noise,if the electromagnetic structure is optimised and designed from the perspective of the motor device composition,it may lead to problems such as complex modelling,high design modification costs,and unclear engineering optimisation methods and principles.In this thesis,the content and distribution of current harmonics are optimised from the perspective of traction motor control to achieve the purpose of suppressing motor noise more directly and effectively.In this thesis,the whole vehicle is tested through a test line to study the motor noise characteristics and the effects of the traction system under different operating conditions.Furthermore,based on the premise that the engine body remains unchanged,an optimised control strategy for traction engine electromagnetic noise is proposed.By optimizing the modulation scheme and the distribution of switching frequencies,the harmonic content can be suppressed and the excitation effect of radial electromagnetic force on the motor can be weakened,thereby effectively reducing the electromagnetic noise content of the traction motor.In order to solve the common mode voltage problem,the possibility of achieving zero common mode voltage in a dual three-phase motor can significantly reduce the common mode currents in the bearings and insulated components of the traction motor,and can improve reliability.In order to meet the actual winding connection requirements,based on the connection of the dual three-phase motor windings,forward zero common mode voltage pulse width modulation(Zero CM PWM: phase aligned,ZCM PWM)and reverse zero common mode voltage pulse width modulation(Zero CM PWM: phase reversed,RW PWM)algorithms are designed to eliminate the common mode voltage effects.Moreover,the zero common mode modulation algorithms are combined with synchronous modulation algorithms for practical railway traction applications to achieve variable switching frequencies with zero common mode and segmented synchronous modulation to meet railway traction requirements.To address the issue of IGBT lifespan degradation,a traction force dynamic allocation strategy aimed at reducing IGBT lifespan loss is proposed at the system level without changing the vehicle hardware structure and the performance of the traction transmission system.This strategy divides the running trajectory of the train into multiple subintervals,and dynamically allocates the traction force in each sub-interval with the goal of minimizing the sum of IGBT module losses of the traction inverter,effectively reducing the lifespan loss of IGBTs in the inverters that operate within the planned interval.Furthermore,this strategy does not require changes to the real-time control algorithm of the motor,and can achieve the above objectives through system-level control strategies alone.Finally,this thesis summarizes the research contents mentioned above and based on this,provides prospects for future research work.