| Models of Auto Transformer (AT) traction power supply grids and Electric Multiple Unit (EMU) are fundamental in investigating relationship between grids and EMUs. Existing models are either too complicated or inacuurate. Existing contact resistance and temperature distribution models of pantograph and catenary mostely mostly depend on field tests and test data fitting. Due to the advantages of pantographs with active control in decreasing pantograph arcs and improving the quality of current collection between pantagraph and catenary, I aim at integrated investing electro-magnetic, electric contact, heat conduction and control, focusing on their interactions by using theoretical analysis, experiments and numerical computation in this dissertation. My major contributions are outlined as the following1. Proposal of models of separating catenary wires with contact wires for AT traction grids with single-direction of feeding, and integrated equivalent models of traction drive systems for CRH2 type EMU with traction property consideration. Compared to existing models, my proposed models of coupling grids and EMUs have improved accuracy by (1) considering capacitances between lines; (2) considering rectifiers in details with control; and (3) assuming nonlinear load of inverters and motors under traction conditions for CRH2 start and rated speeds. Research results using my coupling model demonstrate that EMUs are equivalent to nonlinear load at public networks connection spots during start and rated speed, which is a weak capacitive circuit in the steady state.2. Investigation of current and voltage distribution for uni-direction feeding AT traction grids, located within 10km of substations, based on the coupling model of grids and EMUs. My results reveal that dropper currents at three positions are non-negligible, and the thermal stability and mechanics property should be emphasized:(1) the first dropper is located near the substation; (2) droppers connected to train; (3) the dropper is located near the AT substation. And the track current near AT substation is non-negligible, which will impact on track signal circuits. Based on the coupling model of grids and integrated equivalent circuits of trains, we compute overvoltage values of passing on-board neutral section, which shows that suppression is not considered under uni-directional feeding AT traction grids.3. Proposal of models to compute steady state contact resistance and dynamic contact resistance. The proposed model of steady state contact resistance aims to give a theoretical minimum bound. The model of dynamic contact resistance is not derived by test data fitting and we assume the coefficient of attrition should be constant. Our research results are as follows:(1) dynamic contact resistance is much higher than steady state contact resistance; (2) when a train is in rated speed, dynamic contact resistance is in scale of milli-ohms; (3) when a train is in static to lift or lower pantographs, dynamic contact resistance is in scale of ohms.4. Proposal of models to compute compute steady state and transients heat conduction by current, contact resistance and arcs for pantograph and catenary systems, in which coefficients of heat convection and radiation are considered. I provided theoretical solutions to the proposed models under different conditions, and studied temperature distribution properties based on the solution results.I also studied the impact of coefficient of heat convection, current and contact area on heat distribution. Results obtained from FEM (finite element method) are used to verify the effectiveness of my proposed models and solutions. The following are concluded:(1) Temperature rise by current is in normal scale under rated conditions, whereas temperature rise caused by current at special droppers need to be verified, and those droppers are tend to be softened or even be disconnection when over-load or under severe weather; (2) Criteria for loss of contact should be stringent, that is duration of an arc lasting should be less than 10ms and then serious arcs which duration is longer 100ms should be suppressed. Pantograph with active control should be applied where serious arcs cannot be inhabited.5. Rigidity and flexible types of setups to generate pantograph arcs are designed and measurement of electric, optical, mechanics and thermal quantities are studied in this dissertation. We show that harmonics generated by motion arcs is more than by static arcs, and third harmonics is a major component, and DC component should not be neglected. Arcs reignition occurs more frequently in motion pantograph arcs, and overvoltage values by reignition are significant.6. Proposal of coupling models for pantograph and catenary with two degrees of freedom, aiming at solving dynamic problems.I also designed a strategy of Model Reference Adaptive Control (MRAC) based on Lyapunov stability theory. Numeric results show that vibration of displacement and contact force of pantograph head is decreased, compared to that without MRAC, and properties of steady state and transients of MRAC are improved. I also designed a setup to simulate pantograph with active control, which was driven by an electric motor. Test results prove validity of the setup.My proposed coupling model of train and grid helps to optimize match between EMUs and traction grids. My coupling model of thermal and electric provides insights of field test results by using theoretical analysis. A motor-driven pantograph with active control has superior response than a hydraulically driven system. It potentially improves relationship between pantograph and catenary system in the future. |
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