| With the rapid development of high-speed railways,the in operation and commutation power supply technology used in current traction power supply systems gradually exposes many problems such as excessive phase separation,harmonics,power quality,negative sequence,and power system efficiency.Through a large number of theoretical research,simulation experiments and pilot projects,it has been proved that the new through-in-phase traction power supply system based on the full line through technology and in-phase compensation technology can effectively solve the negative sequence problem and cancel the electrical phase separation at the exit of the traction substation.And improve the reliability of power supply capacity,reduce braking energy loss.Traditional power frequency protection has been difficult to meet the needs of traction network protection.Some researchers have proposed that traveling wave protection,which is very mature in the field of high-voltage DC,can be applied to traction power supply systems,and its theoretical performance has been proven through simulation experiments.Due to the superior comprehensive performance of the AT power supply system,most current high-speed railways choose this power supply method.Therefore,this paper takes the through-phase in-phase AT traction power supply system as the research object,uses the PSCAD platform to build a simulation model of the power supply system,and gives some important model parameters.This paper proposes that the physical boundary of the traction network is formed by the capacitance at the exit of the traction substation and a section of the trolley line outside the area.A large number of simulations show that the boundary formed by the 3m trolley line and the output capacitance of the traction substation can effectively distinguish between internal and external failure Therefore,the length of the trolley line forming the boundary in this article is 3m.Analyze the frequency domain characteristic model of the continuous co-phase AT traction power supply system and the traction network boundary.Study the frequency characteristics of the traction network and the boundary of the continuous co-phase AT traction power supply system,study the attenuation of the high-frequency components of the fault transient signal by the traction network and the traction network boundary,and give the attenuation of the high-frequency transient of the fault by the traction network.The traction net length critical value whose strength exceeds the boundary to the attenuation strength of the fault high-frequency transient quantity,and the influence of the change of the fault location on the fault high-frequency transient signal detected at the protection installation placeBased on the boundary of traction network of the continuous co-phase AT traction power supply system has a strong attenuation effect on the high-frequency components of the transient current,a through-phase in-phase traction network single-end current transient protection is proposed.Firstly,the multi-resolution morphological gradient is used to perform signal processing on the fault current line mode components collected at the protection installation site to obtain the polarity of the fault current line mode waveform abrupt point.Then judge the location of the fault by the polarity of the sudden change point of the fault current line mode component waveform:if the polarity is negative,the fault occurs outside the side area,and the protection does not operate;if the polarity is positive,the line mode of the fault current is the component performs morphological spectrum calculation and calculates the morphological spectrum value at different scales.After normalizing the spectral value,it is converted to the frequency domain and compared with the value to determine whether the fault occurred in the area or outside the opposite area.If the morphological spectrum value is greater than the threshold,it is a fault within the zone,otherwise it is a fault outside the opposite zoneThis paper proposes a single-ended protection method for the traction network of the continuous co-phase AT traction power supply system based on the combination of compressed sensing theory and second-order differential method.First,the compressed transient reconstruction of the fault transient current line-mode signal collected by the protection equipment is performed by compressed sensing technology.The constructed signal is very similar to the original signal with less noise content;then the reconstructed fault current line mode signal is processed by the second order differential method to obtain the traveling wave head wave amplitude of the fault current line mode component;finally by comparing the magnitude of the first wave head amplitude of the fault current line mode component with the threshold value,it is judged that the fault occurred within or outside the area.A large number of fault simulation experiments are performed using the simulation model built in this paper The effectiveness of the protection method is verified by analyzing the experimental results. |
