Research Of Train Passing Neutral Section With Load Based On Current Information

ABSTRACT:In the traction power supply system, there are some sections without power supply, which is called neutral section. Trains pass through these sections without power supply, and speed of trains reduces greatly. Over-voltages occur when pantograph transits from catenary to neutral section or from neutral section to catenary. It is not only harmful to the equipments, and also makes passengers uncomfortable. Neutral section is bottle-neck in the traction power supply system to preclude development of high speed railway and heavy haul railway. This dissertation researches a new system to achieve trains passing neutral section with traction load, and no shock. Meanwhile a new position detection method is proposed and studied. Simulations and experiments demonstrate the correctness of the research results.In this dissertation, influnece of trains passing neutral section has been discussed. The existed systems and train position detect methods for trains passing neutral section were compared. Based on it, two improved system schemes of grouding switch passing neutral section with electronic switches are proposed, which are one position sensor installed in neutral section and no position sensor installed in neutral section respectively. Switching logic in different system conditions has been investigated based on voltage and current of train. Deadtime when grouding switches changing-over has been discussed. The conclusion is that trains pass neutral section with traction power in the new system.This dissertation researches simple chain catenary structure. Catenary impedance has been modeled by unit, which includes a length of carrier cable, hanger and contact wire. Based on current distribution of catenary, new train position detection methods are proposed, which monitor current changing in the catenary, to detect the position of pantograph. These methods don’t need to install equipment on the train, nor interact with the train control signal, so it shows a high security performance. Then position sensor has been designed, it was based on new type current transformer and optical fibre transmission technique. The train’s position signal can be transmitted to the control system on the ground accuratly and reliable.Equivalent circuits of traction power supply system and train has been modeled, and electrical transient state process has been researched theorily. The reason of over-voltage and over-current has been discussed. Then the control strategy to avoid over-voltage and over-current is proposed. Base on the analysis and control, the new system utilizing electronic switches can eliminate over-voltage and over-current completely, so trains pass neutral section smooth and steady.This dissertation researched and contrasted several phase detection method to detect voltage phase and current phase. Through the analysis and comparison, weighted least squares method has high precision and good robustness when phase or amplitude of voltage changing suddenly, and also it has outstanding ability to obtain the phase of fundamental voltage accurately, even if voltage contains rich harmonic content. This method is the most suitable phase detection method in the electronic switches system.Finally, engineering of electronic switches were designed, including device selection, parameters design, and series thyristor drive. An improved gate driver circuit topology is proposed, in which DC power is self-created from high voltage side. It is fit for drive thyristors connected in series through experimental verification.