Research On Traveling Wave Protection Of Traction Network Of Through-type Cophase AT Traction Power Supply System

At present,China’s railway traction power supply system is mainly under different-phase feeding mode,and has power quality problems(negative sequence,harmonics,reactive power)of three-phase unbalance in the public grid and electric phase break between the substations along the railway.In order to solve the power quality problems,the methods such as two-phase reactive power compensation and filtering are generally adopted.In order to solve the problem of electric phase break,the phase break insulators,automatic electric phase splitting or other devices are additionally mounted in the system.However,the requirements for railway heavy haul traffic and high-speed passenger transport cannot be met.The continuous co-phase power supply system based on three-phase/single-phase converter combined two phases of the original traction substations into single phase,thus solving the problem of phase break at the substation outlets;a balanced transformer was used for active power transmission in such a way that the output power of two supply arms was exactly equal and their power factors were the same,partially solving the power quality problems of the power grid.However,due to the hugeness and complexity of the system,its normal operation was guaranteed only by effective protection.The existing traction network was under power frequency variable distance protection as the main way,and was significantly affected by fault transition resistance and other factors.However,traveling wave protection featured quick speed,and was not affected by transition resistance,saturation of current transformer,system oscillation,distributed capacitance of long lines and other factors.We had achieved great research achievements in protection of UHV AC transmission lines and high-voltage DC transmission lines and applied them into practice.Therefore,it was of significance to study the traveling wave protection of the continuous co-phase power supply system.Based on the models of the continuous co-phase traction power system and phase-mode transformation matrix of the traction network,this paper introduced wavelet modulus maximum and ensemble empirical mode decomposition(EEMD)method,proposed the criteria for traveling wave differential protection and travelling wave amplitude comparison protection based on EEMD and wavelet modulus maximum and travelling wave comparison pilot protection based on EEMD and Teager energy operator for the continuous co-phase traction network,and provided simulation experiments and theoretical analysis based on fault position,transition resistance and fault inception angle.Besides,the faults were simulated and fault signals were processed by PSCAD/EMTDC electro-magnetic transient simulation software and MATLAB software,and the protection principle was verified.The conclusions had positive effects on further deepening theoretical research and practical application of the continuous co-phase traction power supply system.