Capacity configuration of combined co-phase power supply system is crucial to the compensation effect and project cost.In the case of full compensation and under compensation of traction load reactive power and negative sequence

we analyzed the relationship between the power factor as well as unbalance of the compensated grid and the parameters such as the capacity ratio of the compensation device and the traction transformer

the reactive power compensation

and the traction load power factor by combining co-phase supply system with a single-phase modular and co-phase power supply system based on the single-phase and three-phase transformer.Moreover

considering it as a constraint for satisfactory compensation whether the power factor at the grid side and the unbalanced degree after compensation meet the national standard

and treating it as an objective function which is the capacity of the compensation device

minimum capacity of the compensation device and the traction transformer

we established two optimization models.Finally

the established objective function

set constraints

and the correctness of the optimization result are verified by Matlab/Simulink simulation.Under the same traction load conditions

the calculation and simulation results are as follows:the network side power factor of co-phase power supply system based on the single-phase and three-phase transformer is higher than that of combined co-phase supply system with a single-phase modular.The grid side unbalanced current of co-phase power supply system based on the single-phase and three-phase transformer is higher than that combined co-phase supply system with a single-phase modular.The grid side negative sequence unbalance degree is 0 when the capacity ratio of the traction transformer and the compensation device is 1.