【摘要】 城市轨道交通牵引供电系统用于为城轨车辆提供电能。当前世界各国城市轨道交通牵引供电系统仍采用传统的多脉波二极管整流方式,其具有结构简单、可靠性高、易于维护等优点,但是由于其能量只能单向传输,无法回收列车多余的再生制动能量,造成能量的极大浪费。本文提出一种基于大功率PWM整流器和二极管整流器的新型能馈式牵引供电变流系统方案,充分利用二者的优点,在保证系统良好的节能效果和直流电压稳定性的基础上,使系统具有较高的可靠性和性价比。文中对新型能馈式牵引供电变流系统主电路及控制的关键技术展开研究,并通过大量的仿真和实验进行了验证。首先,对PWM整流机组主电路及优化进行研究。以大容量、低谐波、模块化、高可靠性为目标进行主电路拓扑选择,得到一种基于隔离型多重化拓扑的无环流PWM整流机组主电路方案。提出了一种利用变压器漏感替代交流电感的系统优化方案,分析了变压器一二次侧不同连接方式对PWM整流器控制的影响,给出了“一次侧控制模式”和“二次侧控制模式”两种不同的PWM整流器控制模式。基于多重化谐波抵消机理,分析了多绕组变压器二次侧连接方式对谐波抵消效果的影响,并得出采用相同连接方式有利于谐波抵消的结论。其次,对基于器件级并联的单变流器扩容技术进行研究。将器件级并联分为IGBT直接并联和智能功率模块并联两个层面展开论述。分析了影响IGBT直接并联均流效果的主要因素,并给出了相应的解决措施。提出一种新的基于智能功率模块并联的单变流器扩容方案,并对其存在的动态环流问题进行了重点研究。在深入分析动态环流产生机理及影响因素的基础上,提出一种利用差模电抗抑制动态环流的解决方案,并借助仿真和实验进行了验证。第三,对PWM整流器多重化串并联控制进行研究。介绍了PWM整流器基于dq旋转坐标系的数学模型和控制方法。分析了基于电压源和电流源模型的串并联控制方案的工作原理和优缺点,提出了一种基于功率源模型的串并联控制方案,解决了多变流器复杂系统的串并联控制问题,并大大简化了控制系统结构。第四,对新型能馈式牵引供电的协调控制策略进行研究。分析了现有二极管整流机组的输出特性,给出了PWM整流机组下垂特性的两种实现方法——“减弱电压环控制”和“输出电流前馈控制”。建立了包含供电站、线路和列车的牵引供电系统简化模型,给出了供电站优化控制目标,提出三种典型的协调控制策略,并对各自的工作机理及优缺点进行了对比分析。搭建了基于二极管整流机组和PWM整流机组的新型能馈式牵引供电变流系统仿真模型,对三种典型的协调控制策略进行了仿真验证。最后,搭建了基于2MW能馈式牵引供电变流器样机的实验系统,分别进行了对拖实验、串并联实验、输出特性实验等多种实验。通过对大量实验波形、测量数据的分析和总结,验证了本文提出的主电路拓扑和控制策略的可行性,以及理论分析的正确性。
【Abstract】 Traction power supply system for urban mass transit is responsible for providing energy for railway vehicles. At present, the multi-pulse diode rectifier is still used in the most of the country in the world. Because it is simple, reliable, and easy to maintain. However, the energy can only be transmitted from AC to DC. So, it can not recover the extra train’s regenerative braking energy, causing great waste of energy. In this dissertation, a new scheme of traction power supply system based on diode rectifiers and high-power PWM rectifiers is proposed. Which will fully use the advantages of both diode rectifiers and PWM rectifiers, making the system have not only good energy-saving effect and DC voltage stability, but also high reliability and cost-effective. The main circuit topology and key control technology will be studied in the dissertation. A great deal of simulation and experiments verify the theoretical analysis and design.Firstly, the study work has been focused on the selection and optimization of the main circuit for the PWM rectifier set. High capacity, low harmonics, modularity, and high reliability are looked upon as the object to select the main circuit topology. Because of avoiding zero-sequence circulating current, the isolated multiple topology with muti-windings transformer is selected. After that, an optimized system scheme is proposed, in which the AC inductance will be replaced by transformer leakage inductance. The Feasibility is analyzed and influence on the PWM rectifier is assessed. In addition, from the perspective of system control and harmonic cancellation, selects the viable connect-type of the transformer.Secondly, the capacity expansion technology of single converter based on device-parallel has been studied. It is divided into two levels including IGBT-parallel and IPM-parallel. First of all, the influencing factors of IGBT-parallel is analyzed, the corresponding solutions are given. Then, the capacity expansion scheme based on intelligent power module (IPM) is proposed. The problem about dynamic circulating current (DCC) is studied. Bye means of the in-depth analysis on the generating mechanism of DCC, a new suggestion that use differential mode inductance to attenuate DCC is given. Its effect is verified by simulation and experiments. Thirdly, the series and parallel control schemes for PWM rectifier set have been studied. By way of studying on the basic mathematical model and control method in the dq coordinate system, the series and parallel control schemes based on voltage source-current source model, and based on power source model are both proposed. The theoretical analysis and simulation results show that they can meet the demands of series and parallel of PWM converters.Fourthly, the coordinated control strategy aiming at PWM rectifier set and diode rectifier set have been studied in this dissertation. First of all, the output characteristic of diode rectifier is studied, as the base of coordinated control. Next, the two basic output characteristics such as voltage-stabilizing and voltage-droop are discussed. The corresponding realizing methods and feature are given. At last, the simplified model including the power station, overhead contact line, and train is built. Referring to three control objectives, three kinds of coordinated control strategies are presented. Their merits and defects are both introduced.Finally, an experimental system based on energy-fed traction power supply prototype rated 2MW is built. The experimental items include back-to-back experiment, series and parallel control strategy experiment, output characteristics experiment. The experimental waveforms and data demonstrate that the selected main circuit topology and control strategy in this dissertation are correct and feasible.
