Research On Power Distribution And Compensation Scheme Of The Interconnected Power Supply System Of Traction Substation Group

Interconnected power supply system of traction substation group is one of the methods to effectively cancel electrical phase separation,and is the most suitable interconnected power supply scheme for the existing traction lines reconstruction without laying cables or special transmission line than other systems.The system relies on a special external power supply structure to connect multiple traction stations under the same power supply node,which allows the power supply to traction load without phase separation.When supplied power,the same locomotive is jointly supplied by multiple traction stations in the system.The system power flow distribution,regenerative energy utilization,and the negative sequence content without phase separation are different from the existing traction power supply system.Therefore,a detailed analysis of the power supply characteristics of the traction power supply group system will help to improve the theoretical system and promote the application and popularization of the system in engineering.Firstly,the structure of interconnected power supply system of traction substation group is introduced,through the method of establishing equivalent circuit,the equivalent circuit models are established respectively for interconnected power supply system of traction substation group based on the direct feeding system and the autotransformer(AT)system,and the mathematical expressions of current distribution of each branch in the system,equivalent impedance of traction system,voltage drop and voltage loss are emphatically deduced.Then,aiming at the increase of negative sequence content after canceling the rotation sequence,according to the power transformation relationship of traction transformer,the general expression of compensation power for negative sequence is deduced,and the compensation principle is discriminated.Based on this theory,a complete set of centralized negative sequence satisfaction compensation scheme is established,which includes the capacity configuration method of compensation device before installation,the working operation method of compensation device and the corresponding control strategy.Based on the above theoretical derivation and the actual line parameters,the equivalent impedance of the system is significantly lower than that of the existing traction power supply system;the capacity of the traction transformer can be reduced due to the common burden of traction load between traction stations;the grid voltage in the middle of the two traction substations in the whole section is the lowest,but it can still maintain a higher voltage level than the existing system,which can correspondingly increase the power supply distance or reduce the number of traction stations;regenerative locomotives can effectively improve the grid voltage;the regenerative locomotive can effectively improve the network loss,and the energy can be directly used by the locomotives on the same line,the utilization rate of regenerative energy is high.Aiming at the negative sequence problem,the compensation scheme is verified by the measured traction load data,which proves that the scheme has good compensation effect.Compared with the full compensation scheme,the scheme needs smaller device capacity;the effectiveness and fast response speed of the control strategy for negative sequence compensation are proved by Simulink simulation.The above analysis proves the superiority of the interconnected power supply system of traction substation group and plays a certain role in promoting its engineering application.