High-power Charging System Research Articles

Cell Architecture Design for Fast-Charging Lithium-Ion Batteries in Electric Vehicles

This paper reviews the growing demand for and importance of fast and ultra-fast charging in lithium-ion batteries (LIBs) for electric vehicles (EVs). Fast charging is critical to improving EV performance and is crucial in reducing range concerns to make EVs more attractive to consumers. We focused on the design aspects of fast- and ultra-fast-charging LIBs at different levels, from internal cell architecture, through cell design, to complete system integration within the vehicle chassis. This paper explores battery internal cell architecture, including how the design of electrodes, electrolytes, and other factors may impact battery performance. Then, we provide a detailed review of different cell format characteristics in cylindrical, prismatic, pouch, and blade shapes. Recent trends, technological advancements in tab design and placement, and shape factors are discussed with a focus on reducing ion transport resistance and enhancing energy density. In addition to cell-level modifications, pack and chassis design must be implemented across aspects such as safety, mechanical integrity, and thermal management. Considering the requirements and challenges of high-power charging systems, we examined how modules, packs, and the vehicle chassis should be adapted to provide fast and ultra-fast charging. In this way, we explored the potential of fast and ultra-fast charging by investigating the required modification of individual cells up to their integration into the EV system through pack and chassis design.

Application of safety and stability optimization algorithms for charging connection devices in high-power charging systems

In response to the safety and stability issues of current electric vehicle charging connection devices, this study proposes a charging system planning for electric vehicles with different capacity charging piles based on the user behavior characteristics of electric vehicles and Monte Carlo methods. It is found that the predicted results under the set management strategy are most consistent with the trend of actual load changes. Moreover, in the prediction of weekly load, the research strategy has better performance than traditional unmanaged strategies. Under the research scheme, the average charging speed of charging piles with capacity of A and B in the peak period was 41.4 min/ and 18.8 min/, respectively, which increased by 29.3% and 11.7% respectively compared with 58.6 min/ and 21.3 min/ in the normal period. The total economic cost of the research plan was 4.871 million yuan, which was 67.0 million yuan and 3.833 million yuan lower than the control methods 1 and 2, respectively. The total number of charging stations of types a and b that need to be purchased for the research method decreased by 18.47% and 63.24% compared to the comparative method 3. The results indicate that the research method significantly improves the utilization rate of charging stations in the electric vehicle charging system. This study has important application value in the intelligent management of electric vehicle charging systems.

Power unit architecture in a high-power charging system for EVs

The paper proposes a methodology to define the architecture of the power unit of a UFC (Ultra Fast Charging) station for electric vehicles (EVs), capable of reaching a power of 350 kW. The main goal is to improve the efficiency of the system defining the best configuration by a MATLAB software (BEA – Best Efficiency Architecture) developed by the authors. The software allows defining the best architecture taking into account efficiency-power curves of all AC/DC and DC/DC power modules currently available on the market, thus increasing energy savings.Architectures based on different connection of AC/DC and DC/DC converters using DC bus have been taken considered. The best configuration found has been simulated using Simulink software, performing time-domain electrical simulations in order to verify and validate the architecture chosen.

Survey results on high power charging in low voltage grids

To advance the electrification of the transport sector, it is essential to develop innovative charging solutions for electric vehicles and to expand the existing charging infra-structure comprehensively. In this context, the HPC-ukf project is investigating the possibilities of a low-voltage connection for high-power charging systems. A high-power charging system supplies a high amount of energy to an electric vehicle in a short time, which increases the charging speed. Due to the high power demand, it is usually installed in the medium voltage. However, this slows down a comprehensive expansion. If installed in the low voltage, it naturally leads to more grid congestions. Therefore, alternative solutions need to be considered, such as the additional use of battery storage systems. In that regard, this paper provides the basis for the HPC-ukf project by investigating the need for a high-power charging system in the low voltage and identifying essential requirements based on a stakeholder survey. The survey interviews 35 stakeholders involved in the operation of electric grids, electric vehicle fleets or charging stations. In addition, 159 electric vehicle users are polled. Based on the survey, the experience and needs of the participants are identified and requirements for high-power charging in the low voltage grid are derived.

Design Optimization and Electro-Thermal Modeling of an Off-Board Charging System for Electric Bus Applications

This paper proposes a co-design optimization procedure of a high-power off-board charger for electric vehicle (EV) applications. The primary purpose is to design a 175 kW SiC DC-charging system with high power density to achieve high efficiency at a wide operating range. For the active part of the DC off-board charger, a three-phase active front end (AFE) rectifier topology is considered in the design optimization and the modelling. The design methodology focuses on the optimal design of the passive filters, accurate electro-thermal modelling of the converter, inductor design, capacitor selection, loss and geometric modelling of the passive filters and control system design. The design optimization of the high-power charging system is performed in MATLAB Simulink using a closed-loop dynamic electro-thermal simulation of the off-board charger. The switching frequency, loss and temperature-dependent efficiency of the charger is investigated in parallel. Through this proposed technique, efficiency greater than 96% is achieved at a switching frequency of 40 kHz, along with a smaller size and lower weight of the system. Moreover, it operates with a current total harmonic distortion (THDi) below 3% and a power factor (PF) above 99% at rated power condition.

Low Frequency Magnetic Fields Emitted by High-Power Charging Systems

The new generation of fast charging systems faces a formidable technological challenge, aiming to drastically reduce the time needed to recharge an electric vehicle as a way to tackle the range anxiety issue. To achieve this, high power (up to 350 kW) is transferred from the grid to the vehicle, leading to potentially high values of low frequency magnetic fields. This study presents the results of measurements of magnetic flux density (B-field) emitted by two different high power charging systems. The electric vehicle used for the recharge was able to digest up to 83 kW of delivered power. The test procedure was designed to identify the locations where the maximum B-field levels were recorded and to measure the exposure indices according to reference levels for general public exposure defined in the Council Recommendation 1999/519/EC. Measurements in close proximity to the power cabinets during the recharge revealed that, at some points, exposure indices were higher than 100%, leading to the identification of a distance from the system components at which the value was lower than the reference level. In the worst case, this distance was 31 cm.

Lifecycle costs and charging requirements of electric buses with different charging methods

Electric city buses and high power charging systems have been rapidly developed in recent years. Battery electric buses are energy efficient and emission free but due to the expensive technology, lifecycle costs can be much higher in comparison to diesel or hybrid buses. This research presents a lifecycle cost analysis for a fleet operation of electric city buses in different operating routes. The objective is to define charging power and battery requirements as well as energy consumption and lifecycle costs. A specific simulation tool was developed to comprehensively evaluate electric buses in different operating conditions. The tool allows to systematically generate and simulate different operating scenarios with a chosen bus configuration, charging method and operating route. Based on the simulation results and predefined cost parameters, lifecycle costs are calculated for each operating scenario. The considered charging methods include overnight, end station and opportunity charging. Simulation results are presented for four operating routes which were measured from existing bus lines in Finland and California, USA. The results show that high energy capacity of the battery system is crucial for the overnight charging buses to achieve adequate daily operation whereas the battery size has a minor impact on the energy consumption and lifecycle costs of the fast charging buses. The lifecycle costs of electric buses are heavily impacted by capital costs including purchase costs of the buses and charging devices. When considering 12 years of service life, the end station charging electric buses can have slightly lower lifecycle costs than diesel buses but on average they have 7% higher lifecycle costs. The overnight charging buses have on average 26% and opportunity charging buses 35% higher lifecycle costs than diesel buses.