Research On Distributed Cooperative Control Of Urban Rail Transit Traction Power Supply System

In recent years,urban rail transit has developed rapidly in China.Through the medium-pressure energy feeding device,the regenerative braking energy of the train can be reused to save energy.However,at present,the traction power supply of the entire urban rail transit still has problems such as insufficient utilization of braking energy,low power factor and large harmonics of the network.Therefore,from the overall consideration of urban rail transit traction power supply system,this paper proposes distributed cooperative control technology,distributed cooperative control for multiple substations,including distributed cooperative absorption control,decentralized reactive power compensation control and distributed carrier phase shifting.Control,etc.Through the cooperative work between multiple substations,the regenerative braking energy can be better utilized,the higher power factor of the main substation and the lower harmonics of the network current can be achieved.Firstly,the mathematical model and control strategy of the energy-feeding device are studied.The mathematical model of the energy-feeding device in the stationary coordinate system and the mathematical model in the rotating coordinate system are established.The current inner loop and the voltage outer loop are designed according to the mathematical model of the energy feeding device and the double closed-loop control method.Secondly,research on distributed collaborative absorption technology.The external characteristics of the energy-feeding device are studied,and the methods for realizing the characteristics of the droop are studied.The absorption scheme of the distributed system is modeled and discussed.The influence of different external characteristics on the absorption effect is studied,and a suitable equivalent internal resistance is proposed.Take the value and verify it by simulation.Third,the decentralized reactive power compensation technology has been studied.According to the principle of reactive power compensation,the reactive power distribution of the medium voltage network of the urban rail transit traction power supply system is analyzed.Based on this,the strategy of decentralized reactive power compensation is proposed and verified by anactual subway line.Finally,the distributed carrier phase shifting technology is studied.By analyzing the principle of carrier phase shift,the difficulty of carrier phase shifting in distributed control converter parallel system is proposed.Then,a distributed carrier phase shifting technique based on AC network voltage synchronization is proposed,which detects the zero crossing of network voltage.Synchronization is achieved,which solves the delay problem caused by traditional hard-wire synchronization and is verified by simulation.