This study addresses a 1.8kV bilateral feeding system for DC railway applications, composed of multi-pulse diode rectifiers at both ends and a storage unit with a DC/DC converter located at an intermediate station. The storage system introduces an additional degree of freedom to control power flows by applying a specific voltage at a strategic point between the passive rectifiers. This paper formulates a voltage compensation problem aimed at reinforcing the network while minimizing conduction losses along the catenary. Due to the nonlinear nature of the power balance equations, a closed-form analytical solution is not directly obtained. To overcome this, the paper proposes an approximation method for the pantograph voltage to enable an analytical formulation of the optimization problem. A comparison between the proposed analytical approach and a numerical iterative optimization method is presented and discussed.

Magnetic windings, in general, and small drives, in particular, are typically associated with thin round copper wires. This group of small drives includes electrical machines for automotive applications, ranging from ancillary units to traction machines for both hybrid electric vehicle (HEV) and battery electric vehicle (BEV)[1],[2]. Wire-wound machines can refer to well-established techniques for widely automatic manufacturing except for traction machines with distributed windings, which still contain manual steps in most assembly lines, particularly after the insertion process[3]. Machines typically wind the loops of continuous wires on a bobbin with a linear or flyer-winding technique outside the stator and pull them from one side of the stator to the other into the slots. The overhang on both ends of the stator, the so-called end turns, forms automatically from the continuous loops.

Electric vehicle (EV) charging infrastructure will play a critical role in decarbonization during the next decades, energizing a large share of the transportation sector. This will further increase the enabling role of power electronics converters as an energy transition technology in the widespread adoption of clean energy sources and their efficient use. However, this deep transformation comes with challenges, some of which are already unfolding, such as the slow deployment of charging infrastructure and competing charging standards, and others that will have a long-term impact if not addressed timely, such as the reliability of power converters and power system stability due to loss of system inertia, just to name a few. Nevertheless, the inherent transition toward power systems with higher penetration of power electronics and batteries, together with a layer of communications and information technologies, will also bring opportunities for more flexible and intelligent grid integration and services, which could increase the share of renewable energy in the power grid. This work provides an overview of the existing charging infrastructure ecosystem, covering the different charging technologies for different EV classes, their structure, and configurations, including how they can impact the grid in the future.

Electromobility has been growing rapidly in recent years, as a result of green and sustainability policies that promote it, but its growth has been hampered by having less autonomy than combustion vehicles, not being able to directly replace them especially in heavy-duty electric vehicles powertrains. The main objective of this work is to propose an improvement to an already implemented Bidirectional Dual-Active-Bridge (DAB) Partial Power Converter (PPC) topology, seeking to boost efficiency by testing different modulations. The modulation study applied to PPC is interesting in order to identify the cases where the RMS current in the transformer is minimized. Results of the study shows that efficiency of the DAB-based PPC can be optimized by using the correct modulation, with a possible maximum efficiency of 99.41% at 6.526 kW.

Hybrid Energy Storage Systems (HESSs) are based on different storage elements such as batteries or ultra capacitors (UC), aiming to implement a system with high energy and power density. These HESSs using multi-modular power converters to incorporate in each power electronics module a different storage element and then, these modules are interconnected to create the total system. On the other hand, the Modular Multilevel Series Parallel Converter (MMSPC) not only allows dynamic interconnection among the modules in series connection but also in parallel connection. This extra switching state among the modules allows new features and operation modes. In this paper, a HESS based on MMSPC topology is presented. The novel HESS-MMSPC topology is simulated with UC and batteries as storage units, and this proposed system is interconnected to an electrical grid. The control strategy and evaluation of the operation of the proposed system are presented.

This paper presents a comparison of buck-boost partial power converters (PPC) for the DC-DC conversion stage of an electrical vehicle (EV) fast charging station. By using a DC-DC buck-boost structure, the proposed fast charger can operate with wide output voltage range. The proposed topology can be used to charge either 400V or 800V batteries. Since the PCC only processes a fraction of the total power, high efficiency is obtained. Two different buck-boost PPC topologies are compared. First structure consider two-quadrant switches in order to obtain bipolar voltage, while the second structure uses an unfolding bridge to change the voltage polarity. Results show that the first solution with two-quadrant switches allows better efficiency. The proposed converter operation is then evaluated for fast charging applications for both 400V and 800V batteries, showing high efficiency up to 99%, making the proposed solution very attractive for fast charging application.

The Modular Multilevel Series Parallel Converter (MMSPC) not only allows dynamic interconnection among the modules in series connection, like the traditional Modular Multilevel Converter (MMC), but also in parallel connection. This extra switching state among the modules allows new features and operation modes. The parallel connection between modules enabled by the MMSPC, is not only limited to those modules belonging to the same arm, but can also be extended to the parallel connection of modules from different arms or even from different phases. All these different interconnections brings operational benefits as well as some constraints. In this paper, the power topology, operation and comparison of different MMSPC configurations are presented. Specifically, this paper describes in detail the traditional MMC (without parallel interconnection), the MMSPC with parallel connection of modules of the same arm only, the MMSPC with the option of paralleling connection among the phases of the system, the MMSPC with parallel connection between arms of the same phase and finally, the MMSPC with full-parallel capability.

This paper proposes an interleaved partial power converter (PPC) for the DC-DC conversion stage of electric vehicles (EVs) fast charging stations. The proposed converter topology is based on the H-bridge DC-DC converter. PPC allows the converter to process only a fraction of the total power, the rest being bypassed and directly supplied to the load. This increases the converter efficiency, as only a portion of the power goes through the converter, thus increasing its efficiency. The principle of operation of the proposed PPC is theoretically analyzed. Simulations of the behavior of the proposed PPC are provided for the charging of an EV battery. Results show the good behavior of the proposed system. It is in particular verified that the proposed converter only process a fraction of the power around 36% for the entire output power range. Comparison with a classical full power converter is provided showing that the proposed topology leads to a significant improvement in terms of conversion efficiency, from 95.1% to 98.3%.

The use of conventional half-bridge submodules in the Modular Multilevel Converters brings important benefits such as the reduction in the power losses and semiconductor devices. However, the system with half-bridge submodule lacks the capability of blocking DC-faults currents. In this paper, a 5-level submodule with DC-fault blocking capability is presented. The proposed submodule allows to operate with different internal capacitances in order to reduce the cost of the system. Furthermore, a control and balance strategy for the novel 5-level submodule is proposed.

The technical challenges associated with distributed generation along with the increased adoption of electric vehicles has motivated the development of new configurations for dc microgrids. In this paper, a novel unidirectional multi-port power converter acts as the building block for interfacing different configurations of PV energy conversion systems, allowing it to reach high efficiency for a wide range of input power. Additionally, depending on the connection of the sources, the converter can act as a buck-boost converter or a buck converter, where the former offers wider input voltage range and the latter offers higher efficiency. Additionally, a sum/difference control scheme suitable for both configurations is presented. Simulation results are provided for a 32 kW PV system, establishing a comparison between the two configurations and validating the proposed topology and control scheme.

This paper proposes a bipolar-dc-bus Electric Vehicle (EV) charging station without a line-frequency transformer at the medium-voltage grid side. It is mainly composed of the Neutral Point Clamped (NPC) converter based central ac-dc station and the parallel isolated three-level dc-dc converter based fast chargers. Due to the elimination of the line-frequency transformer, the volume and cost of the system are reduced. Meanwhile, the isolation and step-down between high dc-bus voltages and low load voltages are performed through the high-frequency transformers, leading to increased voltage utilization of switching devices. In order to guarantee the bipolar dc buses balance and minimize the dc-bus voltage ripples, the 180°-interleaved operation for the two parallel isolated three-level dc-dc converters is proposed to make the total neutral-point current zero so that all fast chargers do not bring any unbalance problems. The proposed 180°-interleaved operating principle has been analyzed in detail, then simulation results are presented to verify its performance.

This investigation presents a grid-connected five-level H-bridge neutral-point-clamped converter operating with a single dc-link as photovoltaic power source. The operation with a single dc-bus is enabled by adding a transformer with open-end winding secondary, where each power cell of the converter is connected. The proposed control scheme is validated trough simulation results and tested under dynamic conditions. It can be implemented with a good tracking of the active and reactive power references injected to the grid. The results serve as a preliminary validation to potential utilization of the converter in large scale photovoltaic energy conversion systems.

This paper proposes a new power converter topology for the Wave Dragon multi-megawatt wave energy conversion platform. The current wave dragon power converter system is composed of several low-voltage two-level voltage source converters in back-to-back configuration; one per turbine-generator. Although this is a well known and proven technology, the use of distributed power electronic converters among all turbines does not bring any additional benefit in terms of efficiency and power quality. The proposed topology remains operating at low voltage and distributed at the generator side, but is combined at the grid side into a three-phase cascaded H-bridge (CHB) multilevel converter operating at medium voltage. This is achieved interfacing each PMSG through a low-voltage full bridge diode rectifier, followed by a boost dc-dc converter connected to the dc-link of the power cells of a 7-level CHB. The proposed configuration allows to concentrate the whole Wave Dragon platform into a single grid-tied converter with higher power quality and efficiency. Control schemes for both grid- and generator-side converters, and simulation results are presented in this paper.

The automotive industry is making important changes towards the electrified transportation. Several Electric Vehicles (EVs) and Plug-in Hybrid EVs are currently on the market offering a clean and environment friendly alternative to conventional vehicles. However, limited mileage capacity and long refueling times have lead to a lukewarm reception from the consumers. In order to reduce the charging time fast charging architectures are being developed, usually as off-board solutions located in public installations. This paper presents a centralized charging station architecture, using a bipolar dc grid to power off-board chargers and integrate of DGs and storage systems. The central converter topology is an NPC and a novel balancing technique is implemented to extend the operating range of the power converter.