【作者】 王海田；

【导师】 李格；

【作者基本信息】 上海交通大学 ， 电气工程， 2011， 博士

【摘要】 故障短路严重威胁了电网和大电源的安全与稳定运行,装备故障电流限制器是解决该问题的主要技术手段之一,这在交流系统中已成功应用。高压直流的发展同样需要抑制直流故障短路电流,因此,研究限制直流故障短路电流的关键理论与方法已成为当前直流电力系统研究的前沿课题之一。本文旨在研究具有直流故障电流限制功能的高压缓冲器(snubber),研究其限流机理、拓扑结构、涡流损耗、磁滞损耗,研制出微型缓冲器模型并对3.5nF/100kV高压缓冲器进行了仿真与测试验证。本文的主要研究工作包括以下几个方面:给出了考虑高压缓冲器内层铁心完全饱和时等效电阻的分析方法:利用安培环路定律,在Fink-Baker高压缓冲器分析方法的基础上,推出不同铁心叠片中涡流大小与饱和深度的关系,导出整个高压缓冲器随铁心饱和深度变化的等效涡流电阻。根据高压缓冲器的等效涡流电阻及NBI系统的杂散电容,建立杂散电容的放电模型。采用变量替换法,给出了详细求解过程,得到了铁心叠片饱和深度的指数时间常数、电弧电流及峰值等。在此基础上给出饱和至某层铁心叠片时的等效时变电阻与弧流衰减时间的表达式。优选出高压缓冲器的铁磁材料:从分析铁磁材料的基本理论出发,对几种铁磁材料进行了对比分析,优选出适于制造高压缓冲器的铁磁材料。分析了弧流控制参数与高压缓冲器的尺寸关系,得到高压缓冲器应为细长结构的结论。在确定传输线方案的基础上,进一步明确高压缓冲器的内径、外径尺寸,以确定高压缓冲器的总长度。提出并建立了包含高压缓冲器等效电阻与并接电感的仿真模型:该仿真模型的参数仅与高压缓冲器的工况、尺寸及材料特性有关,并进行了仿真研究。研究结果表明:二次侧接入负载电阻能提高高压缓冲器的饱和阈值电压,同时也提高其限流与吸能能力。该研究为微型高压缓冲器的研制及大容量高压缓冲器的研究提供了理论依据。参照高压缓冲器的仿真设计方案,研制出微型缓冲器并进行试验测试。试验证明本文研究的高压缓冲器能较好地限制直流故障电流。测试得到的弧流放电时间常数、电流峰值与相应理论值基本吻合,验证了前述高压缓冲器理论分析的正确性。参加研制了3.5nF/100kV高压缓冲器和在EAST NBI试验平台的测试,测试结果与理论值基本吻合。但由于NBI测试平台的杂散电容超过预期值,东方超环EAST NBI系统建议采用两台3.5nF/100kV高压缓冲器。本文提出的高压缓冲器具稳态电压损耗小、限流阻抗大、响应速度快、限制电流效果好、吸收能量能力强等优点,是NBI高压系统中有应用前景的保护设备。所研制的微型缓冲器模型验证了本文理论分析和模型的正确性,这些为设计和建设用于EAST和ITER的高压缓冲器提供了依据。更多还原

【Abstract】 At present, the short-circuit fault seriously threatens the security and stability of power system & large-scale power supply. The fault current limiter (FCL) installed in these systems is one of main measures. And this technology is already successful application in AC power system. Development of high voltage DC power system requires DC FCL also. As a consequence, research on key theory and measure of high voltage DC power system has become the leading edge for power system research.A snubber with function of DC FCL is proposed in this paper. The theory, topology, eddy current loss and magnetic hystersis loss of the snubber have been studied, and a minitype sunbber has been manufactured. Then, 3.5nF/100kV snubber has been simulated and tested. The conclusions are as follows:The analysis of the equivalent resistance for snubber considering magnetic saturation is presented in this paper. Using Ampere’s law, the eddy current and the thickness of saturated regions can be deduced in each core tape referring to Fink-Baker method. The equivalent resistance of the snubber is obtained. The transient eddy current model based on the stray capacitance and the equivalent resistance is analyzed. The solving process is listed in detail with variable substitution. Parameters, which are exponential time constant and arc current and peak current of the arc current, are obtained. The equivalent resistance of snubber and the decay time of arc are been obtained when some core tape just fully saturated.The core material of the snubber has been confirmed. From analytical method of ferromagnetic material, several kinds of ferromagnetic material have been compared, and suitable one has been chosen. The relation between the controlling parameter and the dimension of the snubber has been analysed. And results show that the snubber should be slightness. The inside radius and outer radius are determined referring to the dimensions of transmission line, and the length of snubber is confirmed.A simulation model consisting of a parallel resistance and inductance is been presented and set up. The two parameters can be directly calculated according to the work condition, dimensions and material characteristics of the snubber. And simulation study has been researched. The simulation results show that saturation threshold voltage of snubber can be enhanced with secondary resistor, and also show that the capacity of limitting current and absorbing stored energy can be improved. The theoretic analysis laid theory base for snubber test model manufacture and high voltage, high capacity snubber research.Minisnubber was constructed for Experimental Advanced Superconducting Tokamak (EAST) neutral beam injector (NBI) referring to the simulation design scheme. A sequence of experiments has been completed. And results show that snubbers have good ability of current-limiting function. Exponential time constant and peak current of the arc current are approximately the same as measured ones. The validity of the analytical method is validated.The 3.5nF/100kV snubber of EAST NBI has been manufactured. We conducted a sequence of tests on the EAST NBI experimental system. And the results show that a very good agreement between the experimental test results and the simulated ones. Because the stray capacitance of test stand is much larger than its expectation value, EAST NBI system should introduce two 3.5nF/100kV snubber prestnted in this paper.A snubber proposed in this paper has the advantages of low voltage loss under steady state, high limiting resistance, fast dynamic response, satisfied current limiting effect and powerful ability of absorption stored energy. It is a promising apparatus as the NBI system protection. Experimental study on the minisnubber validated the theory analysis and proposed simulation model are validity in this paper, which make a ready for research and designing International Thermonuclear Experimental Reactor (ITER) snubber.更多还原