Research On Traction Drive Control Technology And Simulation Of Urban Rail Vehicles Based On VVVF

Urban rail vehicles are the main modes of transportation in public transportation.This year,there has been an upsurge in urban rail transit construction.Most urban rail vehicles use electric traction to supply power through the traction transmission system of catenary vehicles.The traction motor on the vehicle drives the vehicle's moving wheel to rotate and realizes the traction brake function of the train.There are also many types of traction Motors,and there are also a wide range of choices,such as DC traction Motors,AC traction Motors,linear Motors,etc..The control method of AC traction control system using AC asynchronous traction Motors is studied in this paper.The AC traction system has superior running performance,which is mainly embodied in the excellent traction characteristics and braking characteristics;Large installed power;Light weight;Wide range of speed regulation;Dynamic response is fast;Through the reasonable design of the inverter;Reducing the harmonic of the traction system;Increased efficiency and reliability;Full use of converter can reverse operation,can easily achieve regenerative braking.In the transmission control of the AC traction system,VVVF(Varible Voltage and Variable Frequency)variable frequency speed control system is used for speed control.The traction transmission system of the city rail vehicle should have a fairly wide range of speed regulation.During the speed regulation process,each speed point must correspond to a suitable output torque.The VVVF speed control system based on the PWM method is an open-loop control method.If the open-loop control is used during the traction drive speed regulation process,it can not guarantee that the sudden acceleration and deceleration of the train will not exceed the subduction of the motor.point,This will affectthe speed adjustment of the vehicle,extend the vehicle start-up and braking,speed adjustment of the dynamic response time.Therefore,to solve one of the problems,a VVVF control system based on SVPWM is used.This is a closed-loop control system that can have rapid dynamic response and accurate steady state performance when the voltage and load fluctuate.The speed of the vehicle and the output torque of the traction motor are taken as the adjusted quantity and as the feedback signal in the closed-loop control.Urban rail transit vehicles require high-performance asynchronous motor transmission systems.In order to establish an effective torque control ring and combine the mechanical characteristics of asynchronous Motors,there are usually two control methods.One is to directly determine or estimate the moment value as a feedback signal.Then,compared with the given moment value,the input deviation signal of the torque regulator can also be generated,and the actual value can be measured as a feedback signal by indirectly measuring the physical quantities related to the given signal,such as the air gap flux and the stator current as the given signal.It can also achieve the purpose of controlling the output torque of the traction motor.In order to make the asynchronous traction motor have better dynamic performance,there are two main control methods in the control scheme selection,namely magnetic field directional vector control and direct torque control.Under certain conditions,the vector control system is equivalent to discoupling two independent linear systems of nonlinear and strongly coupled asynchronous motor speed regulation system,namely speed regulation and flux regulation,which are implemented by speed regulator and flux regulator.The regulator of the linear regulating system is easy to design,so the static and dynamic response of the vector control AC speed regulating system is comparable to that of DC speed regulating system.In order toachieve the good motor traction characteristics of AC traction system during speed regulation,this paper will focus on the control method of VVF inverter in AC traction drive system,and adopt the magnetic field directional vector control method based on SVPWM modulation.To determine whether this control method can achieve high performance AC traction speed regulation.In the process of proving the magnetic field-oriented vector control method based on SVPWM modulation,MATLAB/SIMULINK will be used to establish a simulation model of the system urban rail vehicle AC traction system and conduct validation tests.The feasibility of vector control in urban rail AC traction system is verified by analyzing the simulated experimental waveform.