Study On High-speed Train Traction System Beat-less Control With No LC Resonant Circuit

the DC-link voltage of the single-phase rectifier of AC-DC-AC transmission system contains a ripple component with a frequency that is twice of the grid frequency,which is called the beat voltage.The beat voltage will cause the beat phenomena.The beat phenomena will affect the normal operation of the train.Therefore,it is very important to study the beat-less control method.LC resonant circuit are often used in DC-link in order to suppress the beat phenomenon.But LC resonant circuit is difficult to maintain and conflicts with lightweight requires because it needs huge volume and mass to eliminate the harmonic.Therefore,in the case of no LC resonant circuit,it is very important to study the control and modulation algorithm of converter to realize dead-less control.In this paper,it takes the two level traction drive system as the research object.On the basis of the fundamental principle of Multi-mode modulation and vector control algorithm in order to suppress the beat phenomena of rectifier and inverter,the electric traction converter optimal control algorithm with no LC resonant circuit is researched.Firstly,working principle and 8 working states of traction inverter are introduced.Then,the mathematical model of asynchronous motor in A-B-C coordinate system are studied.In order to simplify model,the mathematical models in α-β and d-q coordinate system are given by using Clark transformation and Park transformation.What’s more,the vector control algorithm of motor and multi-mode modulation algorithm of inverter are studied.The algorithms are verified by the Matlab simulation.Secondly,in order to study the beat phenomenon of inverter-motor system,phase voltage、impedance characteristics and harmonic characteristic of asynchronous motor are analyzed in depth.What’s more,analysis of beat phenomenon in d-q coordinate system is introduced to prove the correctness of the theory.Thirdly,the principle of beat-less control methods including modulation compensation,frequency compensation based on DC-link voltage and frequency compensation based on q-current.The validity of the control methods is verified by the Matlab simulation.The results show that the beat-less control methods are effective,but modulation compensation can not use in square wave area.Finally,the hardware-in-the-loop(HIL)testing system are introduced.The beatless control methods proposed in this paper are tested.It is proved that both the frequency compensation methods can suppress the beat phenomena effectively no matter the motor is in traction and braking.