The power converters based on modular structure have gained importance for electric transportation applications including electric vehicles (EV), EV charging stations, railway traction, and electric ships. Modular multilevel converters (MMCs) are recognized as one of the promising topologies to improve the energy conversion efficiency and fault-tolerant ability of power conversion systems. This paper aims at a review of latest research contributions regarding the evolution of circuit topologies, operational challenges, control schemes and fault-tolerant strategies of the MMC. Finally, the current state of the art, opportunities and their further perspective of MMC in the electric transportation applications are addressed.

Fault detection/diagnosis has become a crucial function of the battery management system (BMS) due to the increasing application of lithium-ion batteries (LIBs) in highly sophisticated and high-power applications to ensure the safe and reliable operation of the system. The application of Machine Learning (ML) in the BMS of LIB has long been adopted for efficient, reliable, accurate prediction of several important states of LIB such as state of charge, state of health and remaining useful life. Inspired by some of the promising features of ML-based techniques over the conventional LIB fault detection/diagnosis methods such as model-based, knowledge-based and signal processing-based techniques, ML-based data-driven methods have been a prime research focus in the last few years. This paper provides a comprehensive review exclusively on the state-of-the-art ML-based data-driven fault detection/diagnosis techniques to provide a ready reference and direction to the research community aiming towards developing an accurate, reliable, adaptive and easy to implement fault diagnosis strategy for the LIB system. Current issues of existing strategies and future challenges of LIB fault diagnosis are also explained for better understanding and guidance.

Existing charging techniques for lithium-ion batteries use a largely open-loop approach, where the charge profile is predecided based on a priori knowledge of cell parameters. There is a need for closed-loop charging techniques that use instantaneous cell voltage and/or temperature to modulate the charging current magnitude. This paper addresses this gap by proposing a constant-temperature constant-voltage (CT-CV) charging technique, considering cell temperature as a key degradation metric. The proposed CT-CV charging scheme employs a simple and easy-to-implement proportional-integral-derivative (PID) controller aided by a feed-forward term. The charging current is dynamically adjusted in response to the battery temperature, which indirectly reflects its aging and thermal environment. As per experimental results, the proposed method achieves 20% faster charging with the same total temperature rise as constant-current constant-voltage (CC-CV) technique. Alternatively, it causes 20% lower cell temperature rise for given total charge time. It can easily accommodate applications that demand even faster charging by simply raising the set temperature. This paper establishes the benefits of the proposed CT-CV charging at cell level and raises the possibility of extending it to the pack level by integrating it with battery management systems.

This paper reviews the modern electric propulsion architectures and configurations for railway traction, which are currently in practice. The development and advancement of power electronics and digital controllers led to the standardization of the insulated gate bipolar transistor (IGBT)-based converter fed induction motor drives. This paper summarizes the state-of-the-art technology of IGBT-based rolling stock in terms of both power and control. Control hierarchy of traction system and drive control techniques are explored. Special emphasis has been put on the technologies, which can improve energy efficiency as well as reliability to develop high-speed rails and metro trains in the near future in both urban and suburban areas. Specific attention is given to power electronic transformer technologybased traction drives and on-board energy storage systems. In addition, advances in traction drive technology and widebandgap power devices are addressed. Finally, major issues faced in rolling stock including the challenges for further improvement are highlighted.

With the growing fleet of a new generation electric vehicles (EVs), it is essential to develop an adequate high power charging infrastructure that can mimic conventional gasoline fuel stations. Therefore, much research attention must be focused on the development of off-board DC fast chargers which can quickly replenish the charge in an EV battery. However, use of the service transformer in the existing fast charging architecture adds to the system cost, size and complicates the installation process while directly connected to medium-voltage (MV) line. With continual improvements in power electronics and magnetics, solid state transformer (SST) technology can be adopted to enhance power density and efficiency of the system. This paper aims to review the current state of the art architectures and challenges of fast charging infrastructure using SST technology while directly connected to the MV line. Finally, this paper discusses technical considerations, challenges and introduces future research possibilities.

Resonant Inductive Power Transfer (RIPT) is gaining in popularity for wireless charging applications of future electric transportation. A fundamental impediment to the efficient operation of an RIPT system is the existence of bifurcation phenomenon in a doubly tuned circuit. Bifurcation can be avoided by either selecting complicated control strategies or by proper design strategies. Many control strategies have been presented in literature for avoiding bifurcation. However, systematic design strategies for avoiding bifurcation are still unknown. This paper presents a novel, simplified, and easy to follow set of design guidelines for series-series compensated RIPT (SS-RIPT) systems. The design guidelines avoid bifurcation by calculating the parameters for a given load profile in a systematic and easy to follow approach. Following the design guidelines, a 3.6 kW setup has been fabricated as an example and verified using finite element analysis as well as experimental testing. Selection of resonant frequency and output voltage for 3.6 kW was influenced by the availability of testing equipment available in the lab. However, the design guidelines are generalized, and by following it, an SS-RIPT system of any frequency and output voltage rating, applicable for EV charging, can be designed.