DC auto-transformer (DCAT) traction power supply system has been studied to suppress the rail potential and stray current for urban rail transit (URT), which generally takes the constant train load to simplify the analysis. However, in practice, the train is a non-linear load with frequent accelerating and braking, which leads to the rail potential and stray current changing with different train operating conditions. Therefore, the dynamic performance analysis and optimization of DCAT system are discussed in this article. The rail potential and stray current dynamic emulator (RSDE) for DCAT system verification is proposed because it is difficult to test the DCAT system directly in the actual URT. Based on the configurations and operation principles of both DCAT system and RSDE, the comparisons between DCAT system and the existing system on the rail potential and stray current are discussed. Meanwhile, considering the train dynamic performance, define the dynamic performance index (DPI) to evaluate the effects of the DCAT system on the rail potential and stray current mitigation and optimize the DCAT system with DPI. Finally, the correctness and effectiveness of DCAT system on the rail potential and stray current mitigation are validated by the simulation results and experimental verification.

多电平均压型直流变换器(MVBDC)在中高压直流变换领域具有良好的应用前景,然而随着电平数的提高,MVBDC中谐振单元数目增加,易引起较大的输入电流纹波,进而影响变换器效率和器件寿命.该文以常见的耦合型和解耦型MVBDC为例,在分析MVBDC输入电流纹波与各级谐振电流之间关系基础上,提出一种输入电流纹波抑制策略.通过调整各谐振电流之间的相位,可有效降低MVBDC输入电流纹波、提高变换器效率.最后,通过搭建仿真模型和实验平台验证了上述理论分析的正确性和有效性.

For urban rail transit (URT), high-voltage AC (HVAC) power is generally transmitted from main substation (MS) to traction substations (TS), and then TS utilizes transformers and diode rectifiers to convert AC power to DC traction power. However, the traditional traction power supply (TTPS) shows the limitations in braking energy waste, high rail potential and stray current, etc. So high-voltage DC traction power supply (HDTPS) is proposed in this paper for URT. Both configuration and principle of HDTPS are analyzed, which mainly includes DC main substation (DMS) and DC traction substation (DTS). Then, the comparisons between HDTPS and TTPS on braking energy utilization, rail potential and stray current mitigation are discussed in detail. Finally, the simulation model of HDTPS is built to verify the above theoretical analysis.

传统多电平均压型DC-DC变换器(multilevel voltage-balancing DC-DC converter,MVBDC)由于能量逐级传递而使得效率普遍偏低,从而限制其在大功率直流变换场合的应用,为此提出一种高效率多电平均压型DC-DC变换器(high-efficiency multilevel voltage-balancing DC-DC converter,H-MVBDC),即通过缩短能量传递路径来降低系统损耗.通过分析H-MVBDC拓扑结构和工作原理,研究其软开关特性,且对H-MVBDC和MVBDC在开关管电流电压、输出电压偏差和效率等方面进行对比,最后搭建仿真模型和实验平台对理论分析进行验证.仿真和实验结果表明,H-MVBDC在提高变换器效率的同时,亦能降低开关器件电流应力和输出电压偏差.

采用走行轨回流的直流牵引供电系统存在轨道电位与杂散电流问题,给城市轨道交通的安全运行带来隐患.上述问题的抑制措施开展现场验证难度大,为此,提出一种基于可变电阻模块的电力电子动模实验平台.首先,分析了双边供电系统中不同接地方式下的任意位置轨道电位和杂散电流随列车位置变化的三维分布规律;然后,将动模实验平台、牵引变电所和列车牵引电流相结合,通过动模实验平台可再现不同接地方式下列车与牵引变电所处的轨道电位及总杂散电流;最后通过仿真与实验结果验证了轨道电位与杂散电流动模实验平台的正确性与可行性.

The rails are generally employed as the return path of traction current in urban rail transit. As the rails are not totally earth isolated, there exist the rail potential and stray current issues inevitably, which may lead to the electric shock, corrosions, and other hazards. In the past decades, different mitigation measures have been adopted to solve these issues. However, there are some limitations in the existing mitigation measures, such as poor performance, weak applicability, and so on. Therefore, the dc autotransformer (DCAT)-based traction power supply system is proposed in this article for the rail potential and stray current issues. The configurations, principles, and current distributions of DCAT system are analyzed in this article. Then, the comparisons between the DCAT system and the existing system for the rail potential and stray current issues are discussed, considering the different grounding schemes. Finally, the correctness and effectiveness of DCAT system on the rail potential and stray current issues are validated by both simulation and experimental results. Moreover, it is shown that DCAT system transfers the traction current from the rail to other lines and solves the rail potential and stray current issues much effectively.

DC auto-transformer (DCAT) traction power supply system has been studied for the rail potential and stray current issues in urban rail transit. By transferring rail current to the specific lines with supply voltage doubling, DCAT system helps mitigate the voltage drop and power loss issues additionally. Both voltage drop and power loss analysis of DCAT system with dynamic characteristics are carried out based on its equivalent model. Moreover, the voltage drop and power loss comparisons between DCAT system and the existing system are analyzed in detail. Finally, extensive simulation results verify the theoretical analysis effectively.

DC auto-transformer (DCAT) traction power supply system has been studied to solve the rail potential and stray current issues for urban rail transit. However, the previous research of DCAT system mainly focused on the constant load without considering the dynamic performance in real conditions. Thus the dynamic performance index (DPI) is introduced in this paper to evaluate the dynamic performances, which is based on the rail potential and stray current comparisons of DCAT system to the existing system. And DPIs can be adopted to predict the DCAT system’s performances in real applications. Finally, the simulation model is built and the results verify the correctness of theoretical analysis effectively.

DC auto-transformer (DCAT) traction power supply system has been studied for the stray current and rail potential issues in DC railways, and the solidly grounded DCAT system of equal sections has been analyzed in detail. However, in practice, the floating scheme more tends to be adopted in DC railways, and the sections of DCAT system is hard to achieve complete equality. Therefore, the performance evaluations of DCAT position for the floating DCAT system were proposed in this paper. The performances of floating DCAT system with equal sections were analyzed comparing with the existing system. Then the theoretical analysis and the relationships between DCAT position, rail potential, and stray current were discussed in detail. Finally, the correctness of the proposed analysis was verified by the simulation results.