Dear Colleagues,

As a major means of transportation, railways are responsible for a large proportion of the transportation of people and goods, and play an important role in economic and social development. Electrified railways have become a major trend in the development of the railway industry by virtue of their safer, more environmentally friendly, faster and more efficient travel experience and transportation services. However, with the development of electrified railways, their power supply and electricity quality are increasingly areas of concern for relevant departments, enterprises and scholars. On the one hand, the safe and stable operation of electric locomotives is closely related to the level and quality of traction power supply. On the other hand, since the traction power supply system directly draws power from the high-voltage power grid through the traction transformer, the reactive power, negative sequence and harmonic components generated in the traction power supply system can be directly injected into the public grid. This has many adverse effects on surrounding power users and key electrical components including generators and transformers.

As a dynamic time-varying nonlinear system, the load of the electrified railway system is based on time-varying parameters such as the number of EMUS or electric locomotives running on the power supply arm of the traction power supply system, the position of each locomotive, the apparent power of consumption/feedback and harmonic output content. It is very important to evaluate the power quality level of the traction power supply system, calculate the dynamic power flow (including fundamental power flow calculation and harmonic power flow calculation), evaluate the traction load, check the traction transformer capacity and so on. Therefore, the modeling of the electrified railway system is the basis, and then the power flow, power quality, impedance characteristics and system oscillation of the traction power supply system can be analyzed and evaluated.

With the rapid development of electrified railways, the power quality problem of the railway system is becoming more and more serious. The whole world pays more and more attention to the power quality problem of electrified railways, actively carrying out research on the comprehensive compensation technology of the power quality of the railway system. At present, the comprehensive compensation methods of negative sequence, harmonic and reactive power for electrified railways can be divided into active control and passive control. The passive governance scheme is more economical and feasible. Passive management methods mainly include: (1) passive compensators—mainly Static Var Compensators (SVCs); (2) active compensators—there are Active Power Filters (APFs) for single-phase access, Static Var Compensators (STATCOM) for three-phase access, Railway Power Conditioners (RPCs) and various variants. With the development of modular multilevel converters (MMCs), an MMC-based railway power conditioner has been proposed that has a comprehensive compensation performance, flexible system without step-down power frequency transformers and modular structure. In terms of active control, high-power PWM rectifiers, power electronic transformers (PETs) and control methods for the traction power supply system are worthy of in-depth study.

Recently, distributed renewable energy systems (RESs), due to their pollution-free and flexible features, have been extensively applied in various practical fields, such as DC microgrids and electric vehicles. Naturally, the wide dissemination of these new power supply modes integrated with RESs has also resulted in rethinking and reformation in other industries, typically including railway traction power supply systems (TPSSs). Moreover, the contradiction between dramatic development and distressed power supply capacity has exacerbated the dilemma of the current high-speed railway TPSS, which urgently needs new methods to achieve balance between supply and demand. Hence, in order to ease the tension in TPSSs, the conventional TPSS should be transformed to provide access for RESs, eventually realizing the coexistence of them. Some multi-port railway power conditioners integrated with RES access are proposed to achieve the comprehensive management of power quality and RES access. On the other hand, research and development of the structure of the DC traction power supply system are needed and meaningful, which can facilitate the access and integration of various new energy sources.

This Special Issue is focused on railway power supply system modeling, power quality analysis, power quality compensation, new energy access and control of the railway power supply system.

Prof. Dr. Fujun Ma
Prof. Dr. Lei Wang
Dr. Xiaofeng Yang
Dr. Wei Liu
Dr. Ke Wang
Guest Editors

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• System modeling and stability analysis
• Impedance characteristics and oscillation analysis
• Power analysis of railway traction system
• Railway power conditioners (RPCs) and control
• Railway power compensators and control
• Power electronic transformers and control
• New energy access and control
• Multi-port railway power conditioners and control
• DC traction power supply network
• Energy management of multi-energy system