Research On Passivity Based Control Of Rectifier In Urban Rail Traction Power Supply System

With the social progress and economic development,rail transit business in the world shows a good momentum of development.Urban rail transit as an important way of urban traffic passenger transport has been solving the problem of urban congestion to a certain extent.The equivalent 24 pulse rectifier is the mainstream of DC traction power supply system,which is taking the place of 12 pulse rectifier.Multi-pulse rectifier as the core equipment of DC power supply system is the main source of harmonics,which causes harmonic pollution and cannot achieve energy feedback.So three-phase voltage PWM rectifier with the great advantages of unity power factor,bi-directional energy flow characteristics,has attracted wide attention from domestic and foreign scholars in the relevant research of the current traction power supply system.The harmonics is greatly suppressed and the project cost is reduced with the help of continuous improvement and innovation of the rectifier control method of urban rail system.PBC strategy is from the energy point to control the passivity system for real-time,and its theoretical basis is the system stability theory.Based on the theory of passivity based control,the idea of applying three-phase voltage PWM rectifier to the traction power supply system is put forward in this thesis.The passivity based power controller of three-phase voltage PWM rectifier is designed to reach the target of global stability and no singularity of the rectifier system.Firstly,the current situation of urban rail transit and the related research on various control strategies of PWM rectifier is introduced into this thesis.12-pulse rectifier and equivalent 24-pulse rectifier are commonly used in urban and outdoor urban rail transit.The simulation of 12-pulse rectifier and equivalent 24-pulse rectifier are carried out to contain the number of harmonics.Because of the character of energy one-way flow of multi-pulse rectifier,the energy generated by the train brake cannot be fed back to the grid,bringing about the profligacy of energy.Secondly,the content of the passivity control theory is discussed in detail,and the mathematical model of the three-phase voltage-type PWM rectifier is deduced.The Euler-Lagrange(EL)model of the rectifier in the two-phase synchronous rotating dq coordinate system is obtained by the coordinate transformation.The passivity of the three-phase voltage-type PWM rectifier is verified through the determination of the passivity.Thirdly,according to the EL model of the rectifier,the passivity power control law is deduced.The expected equilibrium point of the rectifier is determined,and the response speed of the system is improved by injecting damping.The error storage function of the system is designed to obtain the control law through the EL model and the expected error.The simulation analysis of the rectifier control is carried out,including the performance of the rectifier under the condition of load disturbance,locomotive braking and unbalanced power grid.Finally,the control effect of the passivity power controller and the double closed-loop controller on the rectifier of urban rail transit are simulated and analyzed,including the impact on the voltage,current,harmonics and power factor.The results show that the passivity based power control has a better control effect.