Increasing the power rating of electric vehicles (EV) fast charging stations to reduce charging times is considered critical to accelerate the adoption of electric vehicles. Besides increasing the power, other drivers pushing the development of EV fast chargers include the improvement of efficiency and reliability. Partial power converters (PPC) have emerged as an interesting option for some of the power converter stages in fast charging stations due to their potential to increase efficiency and power rating. However, some PPCs operate as switched autotransformers by using high frequency (HF) isolation transformers but without providing galvanic isolation. This is a drawback due to cost, size and losses introduced by the transformer. This paper presents a transformerless DC–DC Type I step-up PPC for a DC–DC regulation converter for EV fast charging stations. The proposed converter replaces the transformer commonly used in Type I PPC by an impedance network, resulting in a more efficient, cheaper, and less complex converter option. This concept is verified through simulations and experimentally validated with a laboratory prototype.

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.

This paper proposes a new buck-boost flying-capacitor (FC) converter for the DC-DC stage of an Electric Vehicle (EV) fast charging station. The proposed converter is capable of delivering a wide output range of voltage to charge different battery configurations. The converter has two modes of operation, buck and boost. Thanks to this feature, the proposed converter allows higher efficiency and a wide operating range. The proposed converter is capable of supplying a voltage range from 200 V to 1000 V at its output, which shows the feasibility of occupying the converter inside a charging station that allows charging 400 V and 800 V battery systems. The average efficiency reported is over 97%. It is concluded that the proposed buck-boost FC converter is suitable for modern wide-output EV fast charging applications.

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.

This paper proposes a new transformerless partial power converter for the DC-DC stage of a Electric Vehicle (EV) fast charging station. Partial power converters (PPC) are very attractive for this purpose thanks to their high efficiency. Based on this concept, it is proposed a new transformerless PPC using an impedance network instead of the transformer used in classical PPC. The proposed solution allows similar efficiency compared to traditional PPC, but improved power density since no transformer is required. Simulation results show the effectiveness of the proposed converter in both cases of 400V and 800V DC-DC fast charging stations. Efficiency of the proposed converter has been evaluated, and results show high efficiency over a wide range of operation, with a maximum of 98%. It is conclude that the proposed transfromerless partial power converter is suitable for EV fast charging application.

Electrification has been a key component of technological progress and economic development since the industrial revolution. It has improved living conditions, spurred innovation, and increased efficiency across all sectors of our economy and all aspects of our lives. During the coming decades, electrification is expected to reach further and deeper into the transportation, building, and industry sectors, mainly motivated by the energy transition to a zero-carbonemission-based economy to mitigate climate change.

Currently, more decoupled photovoltaic (PV) systems demonstrate significant advantages in terms of efficiency increasing the competitiveness of the produced energy. This trend has been performed specifically in string and multistring configurations, where DC-DC converters are used to perform more distributed maximum power point tracking (MPPT). However, high variability in PV sources requires wide input voltage range capacity for the DC-DC converter affecting the efficiency of a classical DC-DC converter topology. Serial partial power converters (S-PPC) have drawn the attention in the last years due to its high efficiency processing only a fraction of the total power. In this paper it is proposed a two-stage approach for high efficiency step-up/down performance for a partial power conversion. Compared with the Type 1 or Type 2 step-up/down S-PPC, the proposed converter can operates with wider range of operation and presents higher partiality over the full operating range, leading to a higher global efficiency. Simulations are provided to verify the validity of the proposed two stage approach.

This paper explores a novel three-port series-partial-power converter structure to enable electric vehicle (EV) fast chargers. Besides handling a fraction of the power being delivered to the battery, the converter provides both step up and step down of its output voltage, hence being able to interface legacy 400-V as well as state-of-the-art 800-V EVs. Compared to existing partial power converters with both buck and boost capability, the proposed three-port structure is shown to be able to operate over a wider range of operation. Simulation results show the effectivness of the proposed converter, reaching 98.65% maximum efficiency. The proposed topology is finally verified to be an interesting alternative for the dc-dc stages in EV charging stations.

This article provides a detailed analysis of the power electronics solutions enabling bipolar dc grids. The bipolar dc grid concept has proven to be more efficient, flexible, and higher in quality than the conventional unipolar one. However, despite its many features, these systems still have to overcome their issues with asymmetrical loading to avoid voltage imbalances, besides meeting regulatory and safety requirements that are still under development. Advances in power electronics and the large-scale deployment of dc consumer appliances have put this growing architecture in the spotlight, as it has drawn the attention of different research groups recently. The following provides an insightful discussion regarding the topologies that enable these architectures and their regulatory requirements, besides their features and level of development. In addition, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

In conventional EV powertrains the main energy storage system is based on battery banks. Potential higher current stress on battery during transient operation can considerably reduce its expected lifetime, while battery size is overrated to respond under heavy transient demands. The regenerative braking capability is also getting limited due to its charging dynamic constraints. Hybrid Energy Storage Systems (HESS) based on batteries and supercapacitors (SC) have the potential to solve this issue. However, SCs size and weight can deteriorate the power density of the solution. In this paper, a Partial Power Configuration (PPC) based on Dual-Active-Bridge (DAB) is proposed as a power interface to increase the power density of an HESS-based EV powertrain. A comprehensive efficiency analysis is provided, while transient dynamic results are provided to validate the proposed power configuration.

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.

This paper presents a new partial power converter (PPC) for the DC-DC stage of electric vehicle (EV) fast charging stations. The proposed converter handles only a fraction of the total power delivered from the grid to the battery, increasing the overall system efficiency and power density, while potentially reducing the cost of the charger. The proposed topology is based on a switched capacitor between the AC terminals of an H-bridge converter, and does not require high frequency isolation transformers to provide a controllable voltage source between the DC-link and the battery. The proposed concept can be implemented using interleaved power cells, which can improve the power quality, reduce inductor size, and enable scalability for higher power rating chargers. The operating principle, partial operation analysis, control scheme, and simulation results are presented to validate the proposed concept.

During the last decades, AC systems dominated the power transmission and distribution applications almost exclusively. However, a recent convergence of needs originated in different sectors (renewable energy conversion, information technology and transportation) have accelerated the development of DC systems. Nowadays, DC systems are present at both transmission and distribution levels, offering high-performance solutions with enhanced efficiency and reliability, besides reducing the number of power conversion stages involved and uninterrupted power delivery. For LVDC active networks, two kinds of architectures are possible: unipolar and bipolar. Despite being a more sophisticated and technically complex solution, bipolar structure provide several advantages over conventional unipolar ones. Higher availability, efficiency and flexibility are just a few advantages featured by bipolar systems. This chapter presented a brief overview covering the different aspects of bipolar LVDC networks. Distribution converter topologies, balancing stages and also their control schemes are discussed in order to highlight the efforts being made in this growing architecture.

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%.

Medium voltage grids are a suitable selection for the connection of high power applications. However, for certain applications, such as PV energy conversion systems or fast charging stations for PEVs, the DC voltages are limited to be below 1000 V, making difficult their connection to such grids without the use of a step-up transformer. Multilevel converters allow the grid connection of such DC loads, by connecting them in one of their multiple dc sources, however, due the nature of these applications unbalanced operation is inherent, and cannot be completely solved by the modulation stage, thus additional circuitry is required. On the other hand, the use of a multilevel converter provides higher efficiency in the power conversion stage, higher power quality and reduced stress on the switching devices, which is also beneficial due the power ratings being reached by the mentioned applications. This paper explores a four-level double star multilevel converter as interface for central or mul-tistring inverter for grid-connected photovoltaic energy systems. The topology is capable of handling three PV arrays with different MPPT (with or without additional DC-DC converters), with the use of an additional balancing stage. The four-level output voltage improves the power quality of the PV energy conversion system, while reducing the grid filter size. This paper presents the operating principle of the converter, the control scheme and the simulation results, that show this topology can be an interesting alternative for large-scale PV plants.

This paper introduces a study on the charging infrastructures, integrated with distributed energy sources, showing their ability to support the electric and hybrid mobility in a smart grid scenario. This analysis starts from a description of the main AC and DC architecture and then goes through the advantages derived by the integration of renewable energy sources within the existing electric power network. A section of this paper is then dedicated to the main technologies of energy storage systems, which allow and support the integration of unpredictable energy sources into the grid. Finally, the power on-board and off-board vehicle charging devices are analyzed with specific focus on PWM control schemes, for the regulation of AC/DC and DC/DC power converters, and on grid operations (V2G) related to different aggregation schemes.

This chapter provides an overview of the different charging architectures available for electric vehicles and plug-in hybrid electric vehicles. The charging architectures are addressed following two main categories: onboard chargers, used mainly for slow and semi-fast charging (generally AC connection), and off-board chargers, used for fast charging (DC connection). The chapter focuses on the mainstream solutions available in the industry, and also presents some recent advances and trends found in the literature. In addition, the chapter provides an introduction to well-established charging standards being used by manufacturers. Finally, the control schemes used in charging configurations, including the control schemes for DC-DC and AC-DC converter stages, are discussed, the latter considering both single- and three-phase control schemes.

This paper presents a grid-connected seven-level cascaded H-bridge converter operating as photovoltaic inverter. The main issue with this topology are the natural power imbalances between the power cells and the phases of the converter. The control problem is addressed with a Multiobjective Finite Control Set Model Predictive Control, where a dc-link voltage balance among the cells and good tracking of the active and reactive power references injected to the grid are achieved. Furthermore, an average switching frequency control per cell has been included. The proposed control scheme is validated trough simulation results and tested under dynamic conditions.

This paper proposes a novel architecture for plug-in electric vehicles (PEVs) dc charging station at the megawatt level, through the use of a grid-tied neutral point clamped (NPC) converter. The proposed bipolar dc structure reduces the step-down effort on the dc-dc fast chargers. In addition, this paper proposes a balancing mechanism that allows handling any difference on the dc loads while keeping the midpoint voltage accurately regulated. By formally defining the unbalance operation limit, the proposed control scheme is able to provide complementary balancing capabilities by the use of an additional NPC leg acting as a bidirectional dc-dc stage, simulating the minimal load condition and allowing the modulator to keep the control on the dc voltages under any load scenario. The proposed solution enables fast charging for PEVs concentrating several charging units into a central grid-tied converter. In this paper, simulation and experimental results are presented to validate the proposed charging station architecture.