Research On Load Modeling And Power Flow Calculation Of Traction Power Supply System For The Tramcar

ABSTRACT:Modern tramcar is a new type of urban rail transportation, the safety and reliability of traction power supply system are essential to guarantee the normal operation of the tramcar. However, we just do a few specialized researches on traction power supply system for tramcars. In order to serve the tramcar better, the thesis does research on power supply system, load modeling and power flow calculation for the tramcar.The tramcar is a kind of middle-low urban rail transportation and its power supply system is similar with the mass capacity of the subway. Considering the lines of the tramcar most are urban land-lines and small amount of overhead lines, moreover, stations are simple, we cannot directly copy the methods of the subway when designing the power supply system for the tramcar. Based on the experience in the subway, the thesis combines the characteristics of the tramcar and discuses the overall structure, medium voltage network and box-type substation of the power supply system.Electric locomotives are the main power load of the power supply system. To build the power load modeling of traction power supply system for the tramcar, traction calculation is used. Referring to "train traction calculation procedure"(TB/T1407-1998), the author takes the multi-particle model which could accurately describe the force on tramcar when running on the rail. Considering the subsequent needs of power flow calculation, the author achieves the traction calculation underling the traction strategy of the maximum power consumption model.The traction power supply system of the tramcar is a complex chain network. In order to build mathematical model easily, the author divides sections in the location of substations and tramcars. After dividing sections, each contact line can be treated as a resistance. Considering the impact of the leakage resistance, the author uses pi equivalent circuit to replace the rail. For the traction substation, which has a different output with the load current changing, so the traction substation can be seen as a Thevenin circuit but the voltage and resistance differ with different load current. In actually, the network voltage almost makes no difference to the power of the tramcar, what’s more, to simulate the interaction of multiple tramcars, the thesis uses the power source model. To solve the whole network, the node voltage equation is built for each node. Because the node admittance matrix is large and sparse symmetric matrix, the LU decomposition method should be used to solve the network. The power source model of the tramcar leads to a nonlinear problem, the author designs the iterative methods for solving equations. What’s more, the author uses an example to prove that the calculation model is validity and the results are correct.At the same time, the author uses MATLAB software to make a program for the traction calculation and power flow calculation of the tramcar. The results can be a reference for the related operators and design personnels.