| Summary: | 博士 === 國立臺北科技大學 === 電機工程系博士班 === 102 === Accurate solution of ungrounded DC rail system load flow requires the inclusion of detailed negative path components in the traction power network circuit model, resulting in large numbers of circuit nodes and branches. Such modeling complexity brings about heavy computational burden, ill numerical conditions, and nonlinear circuit components not readily solved for by nodal equations. In this dissertation we present a novel methodology utilizing the ladder-circuit topology of ungrounded DC rail traction networks to perform accurate and efficient load flow computation. We first study the circuit configuration of traditional grounded traction networks, and introduce a ladder-circuit load flow solution formulation based on the similarity to AC radial power distribution systems. Compare with the common-used nodal equation formulation, this solution scheme can do without large scale simultaneous circuit equations or the need to perform large-dimensional matrix manipulations, hence can achieve computational efficiency as well as numerical stability. Modern ungrounded DC traction power systems have cross bondings in the negative return circuits to reduce resistance, adding more complexity and asymmetry to the traction circuit. Thus we propose an approximate model of the so-called double ladder circuit to preserve the simplicity of grounded DC track networks without sacrificing analytical accuracy. The ladder circuit model is implemented by diakoptics to decompose an ungrounded DC traction networks into individual track circuits and substations. By iterative solution of load flows in two loops of calculations for track circuit layers and substation layers, respectively, the proposed algorithm requires computational burden proportional to the number of substations and track circuits. The computation results from two transit lines in Taiwan show that the proposed algorithm achieves the objectives of computational proficiency, numerical robustness, and versatility to various network configurations such as branch lines.
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