Low Frequency Oscillation Suppression Of High-speed Railway Based On Nonlinear Control Of Locomotive Rectifier

In recent years,the traction blockade in the depots of multiple electric multiple units(EMUs)of high-speed railway has been reported,which is caused by the low-frequency oscillation(LFO)of traction network overvoltage.The LFO seriously affects the normal order of railway transportation and threats the development of high-speed railway in our country.So,it is urgent to carry out the study on its mechanism and suppression measures.The control of EMUs rectifier is the key factor that induces the LFO phenomenon.Firstly,this paper built a EMUs-traction network coupled system model by simplifying traction network.Then treats the control strategy of rectifier as the main research object.Considering the nonlinear control strategy has the obvious advantage in three-phase rectifier control.The H?controller is designed and realized based on the d-q decoupling control of the rectifier.In order to improve the external disturbance rejection characteristics of the rectifier,a first order nonlinear nonlinear active disturbance rejection control(ADRC)is designed.Through the simulations,analysis and comparisons,the improvement in control performance and LFO suppression capability of the proposed methods are verified.Firstly,according to the LFO phenomenon in our country,as a case study of CRH3,traction network,inverter and traction motor models are reasonable simplified,and a EMUs-traction network system model is designed.Secondly,a mathematical model of single-phase rectifier based on d-q coordinates is established,the state variables are determined,the weighting function is selected through introduce the H? mixed sensitivity,the Riccati equation is solved by bringing into the particle swarm optimization(PSO)algorithm.Finally,the H? controller is designed.Compared with the traditional transient direct current control(TDCC),the Matlab/Simulink simulation and RT-LAB platform validation show that the method has better control performance and LFO suppression effect.Thirdly,improve the external disturbance rejection characteristics of the rectifier,use ADRC theory,transition process is set up,and the extended state observer and nonlinear control law are calculated.Finally,a first order nonlinear ADRC is designed.The performance of the controller is optimized by introducing nonlinear control function.External disturbance and internal system disturbance are regarded as a total disturbance.In addition,corresponding dynamic nonlinear compensation is given.The robustness of rectifier to external disturbance and the insensitivity to the change of the controller parameters are improved.Compared with the traditional method,LFO suppression effect of the proposed method are demonstrated by double rectifier and EMUs-traction network coupled system simulations.