Optimal Design of Urban Rail Transit Power Supply System Based on Wavelet Analysis

The urban rail in-phase power supply system is an urban rail transit power supply system based on the power frequency AC25kV power supply system and adopts a combined in-phase power supply scheme. It has the technical advantages of no stray current and no phase separation. In this paper, wavelet is used to extract and decompose the instantaneous signal, and get the transient value transformation of each outgoing line at the time of the fault, and then the fault line can be selected very accurately. This article uses the wavelet packet transform in the wavelet toolbox, through the decomposition of the transient value, the method of comparing the modulus maximum value is used to make the fault line selection. According to the time range defined by the fault analysis method, the initial traveling wave at the fault point, the secondary reflected wave at the fault point and the modulus maximum point corresponding to the reflected wave at the opposite bus bar are correctly identified, and the fault location calculation is realized based on the time information of these three points. Through the traction power supply simulation, parameters such as the contact wire current of each power supply arm, the output power of the main substation and the terminal voltage of the contact wire are obtained. When the locomotive is located at different positions on the line, its changing trend is the same, but the amplitude difference is large. When the locomotive uses electricity at the line exit position, the current amplitude can reach about 3000A, which makes the protection equipment need to adjust the fixed value to Avoid the influence of this current. The results show that the effectiveness and correctness of the wavelet analysis are verified through transformation and simulation analysis of the measured DC feeder current under various conditions.