Research On Equipment Capacity And Compensation Characteristics Of Cophase Power Supply Substation

Combining different transformers wiring forms with balance convert device could constitute a new type of cophase traction power supply system, which could eliminate the unbalanced system, filter harmonics and compensate reactive currents. Compared to power systems, asymmetrical single-phase traction load with high harmonics content and low power factor was a pure resistive three-phase symmetrical load. The principal contradiction between the railway sector and the power sector could be effectively solved. This system also Cancelled the part of the electrical sectioning and conformed to the trend of passenger traffic and freight transport high-speed. The central device of cophase traction power supply system was traction transformer and balance convert device.In this study, firstly, we introduced the structure and compensation principle of cophase power supply system, which was constructed wit three kinds of different wiring transformers. Then, we deduced the common expression of traction side compensation current when reactive current and negative sequence current were compensated. We also deduced the comprehensive expression of three types of transformer secondary side compensation current when the compensation degree was considered. Secondly, the initial investment of cophase traction substation with active compensation depended on the investment of traction transformer and active filter device, which related to the capacity, respectively. For the traction transformer, according to the analytical expression of transformer side compensation current, we calculated transformer capacity utilization ratio under full compensation, and discussed the relationship between transformer capacity, load capacity and system capacity. In addition, in order to achieve optimal delivery transformer capacity by adjusting the compensation degree, we also discussed the relationship between the transformer capacity and compensation degree. Passive compensation device was involved with the transformer wiring and the load port, and there is minimum compensation device capacity. For compensation device of cophase power supply system with active compensation, whether the capacity related to these impact factors. About the above questions, there is no relevant conclusions currently. Because of the active power compensator capacity was decided by compensation current or compensation capacity, this study focused on the general expression of compensation current, established the model of minimum compensation device capacity and obtained some relevant conclusions. The results showed that compensation device capacity has nothing to do with the load port, the alteration of the load port could change distribution of the each phase compensation current, but it could not change the capacity of compensation device. Compensation device capacity was related to the load capacity, load power factor and compensation degree of reactive and negative sequence. However, the compensation device capacity has nothing to do with the transformer wiring forms when the difference of two ports connection angles has no difference. It was meaningless that used special forms of transformer to improve the economic performance of active compensation system.Finally, these above derived results were simulated and analyzed by MATLAB software, the emulational results could be used for further analyzing the relationship between the main equipments capacities in cophase power supply substation, load capacity, load connection angle and load power factor.