Electric Vehicle Fast Charging Research Articles

Influence Analysis of Voltage Imbalance in Input-Series, Output-Parallel (ISOP) Multichannel IPT System

In order to solve the demand for efficient and stable low-voltage, high-power energy transmission capacity of electric vehicle (EV) fast charging, an ISOP-IPT system based on inductor-capacitor-capacitor series (LCC-S) compensation network is proposed. Firstly, the influence of compensation parameter inconsistency on the system is analyzed. On this basis, considering the resistance of coupler coils, the overall transmission efficiency of the system is analyzed. It is found that the voltage imbalance of the system will affect the working state of inverters, and then affect the stability of the system. The system transmission efficiency increases with the increase in mutual inductance. Moreover, the voltage imbalance caused by the inconsistency of compensation parameters and mutual inductance will reduce the transmission efficiency of the system. Finally, it is concluded that in the parameter design of the ISOP-IPT system, mutual inductance should be improved on the basis of ensuring the input voltage equalization of each channel so as to improve the transmission efficiency and working stability of the system. The experimental platform of a two-channel ISOP-IPT system is built and the maximum efficiency is 94.03%, which verifies the correctness of theoretical analysis.

Decision Process for Identifying Appropriate Devices for Power Transfer between Voltage Levels in Distribution Grids

During the energy transition, new types of electrical equipment, especially power electronic devices, are proposed to increase the flexibility of electricity distribution grids. One type is the solid-state transformer (SST), which offers excellent possibilities to improve the voltage quality in electricity distribution grids and integrate hybrid AC/DC grids. This paper compares SST to conventional copper-based power transformers (CPT) with and without an on-load tap changer (OLTC) and with additional downstream converters. For this purpose, a corresponding electricity distribution grid is set up in the power system analysis tool DIgSILENT PowerFactory 2022. A DC generator like a photovoltaic system, a DC load like an electric vehicle fast charging station, and an AC load are connected. Based on load flow simulations, the four power transformers are compared concerning voltage stability during a generator-based and a load-based scenario. The results of load flow simulations show that SSTs are most valuable when additional generators and loads are to be connected to the infrastructure, which would overload the existing grid equipment. The efficiency of using SSTs also depends on the parameters of the electrical grid, especially the lengths of the low-voltage (LV) lines. In addition, a flowchart-based decision process is proposed to support the decision-making process for the appropriate power transformer from an electrical perspective. Beyond these electrical properties, an evaluation matrix lists other relevant criteria like characteristics of the installation site, noise level, expected lifetime, and economic criteria that must be considered.

Piece-Wise Droop Controller for Enhanced Stability in DC-Microgrid-Based Electric Vehicle Fast Charging Station

The need for public fast electric vehicle charging station (FEVCS) infrastructure is growing to meet the zero-emission goals of the transportation sector. However, the large charging demand of the EV fleet may adversely impact the grid’s stability and reliability. To improve grid stability and reliability, the development of a DC microgrid (MG) leveraging renewable energy sources to supply the energy demands of FEVCSs is the sustainable solution. Balancing the intermittent EV charging demand and fluctuating renewable energy generation with the stable DC bus voltage of a DC MG is a challenging objective. To address this objective, a piece-wise droop control strategy is proposed in this work. The proposed scheme regulates DC bus voltage and power sharing with droop value updating in a region-based load current distribution. Voltage compensation in individual regions is carried out to further improve the degree of freedom. In this paper, the performance of the proposed strategy is evaluated with the consideration of real-time solar PV dynamics and EV load dynamics. Further, to showcase the effectiveness of the proposed strategy, a comparative analysis with a maximum power point tracking (MPPT) controller against various dynamic EV load scenarios is carried out, and the results are validated through a hardware-in-loop experimental setup. Despite the intermittent source and EV load dynamics, the proposed piece-wise droop control can maintain voltage regulation with less than 1% deviation.

Hybrid charging station integration of solar power and IGBT technology for sustainable electric vehicle fast charging

The automotive industry, evolving since the industrial revolutions, has adapted to increasing energy demands, witnessing a significant shift from internal combustion engines to electric motors. Anticipating the end of internal combustion engines due to environmental concerns, there is a growing prevalence of zero-emission electric vehicles (EVs). However, the surge in EVs amplifies energy needs and charging infrastructure challenges, urging the consideration of renewable energy integration to alleviate grid overload.

Optimal Allocation of Fast Charging Stations on Real Power Transmission Network with Penetration of Renewable Energy Plant

Because of their stochastic nature, the high penetration of electric vehicles (EVs) places demands on the power system that may strain network reliability. Along with increasing network voltage deviations, this can also lower the quality of the power provided. By placing EV fast charging stations (FCSs) in strategic grid locations, this issue can be resolved. Thus, this work suggests a new methodology incorporating an effective and straightforward Red-Tailed Hawk Algorithm (RTH) to identify the optimal locations and capacities for FCSs in a real Aljouf Transmission Network located in northern Saudi Arabia. Using a fitness function, this work’s objective is to minimize voltage violations over a 24 h period. The merits of the suggested RTH are its high convergence rate and ability to eschew local solutions. The results obtained via the suggested RTH are contrasted with those of other approaches such as the use of a Kepler optimization algorithm (KOA), gold rush optimizer (GRO), grey wolf optimizer (GWO), and spider wasp optimizer (SWO). Annual substation demand, solar irradiance, and photovoltaic (PV) temperature datasets are utilized in this study to describe the demand as well as the generation profiles in the proposed real network. A principal component analysis (PCA) is employed to reduce the complexity of each dataset and to prepare them for the k-means algorithm. Then, k-means clustering is used to partition each dataset into k distinct clusters evaluated using internal and external validity indices. The values of these indices are weighted to select the best number of clusters. Moreover, a Monte Carlo simulation (MCS) is applied to probabilistically determine the daily profile of each data set. According to the obtained results, the proposed RTH outperformed the others, achieving the lowest fitness value of 0.134346 pu, while the GRO came in second place with a voltage deviation of 0.135646 pu. Conversely, the KOA was the worst method, achieving a fitness value of 0.148358 pu. The outcomes attained validate the suggested approach’s competency in integrating FCSs into a real transmission grid by selecting their best locations and sizes.

Thermal Management of Nonuniform Heat Fluxes in an Electric-Vehicle Fast-Charger: Experimental and Numerical Analysis

Thermal Management of Nonuniform Heat Fluxes in an Electric-Vehicle Fast-Charger: Experimental and Numerical Analysis

The Impact of Operational and Environmental Conditions on Battery Lifetime in Fast Electric Vehicle Charging Systems

The Impact of Operational and Environmental Conditions on Battery Lifetime in Fast Electric Vehicle Charging Systems

An improved equalization technique for fast charging of Electric vehicles

This paper describes a lithium-ion battery (LIB) hybrid equalization (HE) structure. There are two primary strategies for voltage equalization (EQ): passive and active. Active equalization (AE) moves energy between the LIBs, whereas passive equalization (PE) wastes energy. PE strategy has the benefit of being easy to put into action, but at the same time, it requires more time to equalize and results in a loss of energy. Although it is difficult to implement, AE has a shorter EQ time and less energy loss. Combining these two methods simultaneously controls a pack of LIBs and equalizes voltage. This article offers recommendations on a cell level (CL) and between stacks. Some LIBs were outfitted with varying state of charge (SOC) levels to simulate a cell imbalance. Different topologies were tested, including combined AE and PE at the pack level and PE and AE topologies at the CL. Response times and SOC levels are used to compare the results. Compared to strictly AE or PE strategies, the HE showed encouraging results regarding EQ time and autonomy. This combination offers a solution that enables one to achieve minimal HE time while maintaining appropriate SOC.

A Review of Capacity Allocation and Control Strategies for Electric Vehicle Charging Stations with Integrated Photovoltaic and Energy Storage Systems

Electric vehicles (EVs) play a major role in the energy system because they are clean and environmentally friendly and can use excess electricity from renewable sources. In order to meet the growing charging demand for EVs and overcome its negative impact on the power grid, new EV charging stations integrating photovoltaic (PV) and energy storage systems (ESSs) have emerged. However, the output of solar PV systems and the charging demand of EVs are both characterized by uncertainty and dynamics. These may lead to large power fluctuations in the grid and frequent alternation of peak and valley loads, which are not conducive to the stability of the distribution network. The study of reasonable capacity configuration and control strategy issues is conducive to the efficient use of solar energy, fast charging of EVs, stability of the distribution network, and maximization of the economic benefits of the system. In this paper, the concept, advantages, capacity allocation methods and algorithms, and control strategies of the integrated EV charging station with PV and ESSs are reviewed. On the basis of the above research, the current problems and challenges are analyzed, and corresponding solutions and ideas are proposed.

Multilayered Energy Management Framework for Extreme Fast Charging Stations Considering Demand Charges, Battery Degradation, and Forecast Uncertainties

To achieve a cost-effective and expeditious charging experience for extreme fast charging station (XFCS) owners and electric vehicle (EV) users, the optimal operation of XFCS is crucial. It is however challenging to simultaneously manage the profit from energy arbitrage, the cost of demand charges, and the degradation of a battery energy storage system (BESS) under uncertainties. This paper, therefore, proposes a multi-layered multi-time scale energy flow management framework for an XFCS by considering long- and short-term forecast uncertainties, monthly demand charges reduction, and BESS life degradation. In the proposed approach, an upper scheduling layer (USL) ensures the overall operation economy and yields optimal scheduling of the energy resources on a rolling horizon basis, thereby considering the long-term forecast errors. A lower dispatch layer (LDL) takes the short-term forecast errors into account during the real-time operation of the XFCS. Per the latest research, monthly demand charges can be as high as 90% of the total monthly bills for EV fast charging stations; to this end, this paper takes the first attempt at the reduction of demand charges cost by considering the trade-off between the energy cost and monthly demand charges. Contrasting literature, this work allocates an energy reserve in the BESS stored energy to deal with the impact of short-term forecast errors on the optimized real-time operation of the XFCS. Moreover, degradation modeling considers the trade-off between short-term benefits and long-term BESS life degradation. Lastly, case studies and a comparative analysis prove the efficacy of the proposed framework.

Comparison of EV Fast Charging Protocols and Impact of Sinusoidal Half-Wave Fast Charging Methods on Lithium-Ion Cells

In electric vehicle fast charging systems, it is important to minimize the effect of fast charging on the grid and it is also important to operate the charging system at high efficiencies. In order to achieve these objectives, in this paper, a sinusoidal half-wave DC current charging protocol and a sinusoidal half-wave pulsed current charging protocol are proposed for the fast charging of Li-ion batteries. A detailed procedure is presented for implementing the following proposed methods: (a) a pre-defined half-sine wave current function and (b) a pulsed half-sine wave current method. Unlike the conventional full-wave sinusoidal ripple current charging protocols, the proposed study does not utilize any sinusoidal full-wave ripple. The performance of these new charging methods on Ni-Co-Al-type Li-cells is studied and compared with the existing constant current and positive pulsed current charging protocols, which have been discussed in the existing literature. In addition, the changes in the electrochemical impedance spectrograph of each cell are examined to study the effects of the applied charging methods on the internal resistance of the Li cell. Finally, the test results are presented for 250 life cycles of charging at 2C (C: charging rate) and the degradation in cell capacities are compared among the four different methods for the Ni-Co-Al-type Li cell.

Strategies and sustainability in fast charging station deployment for electric vehicles.

This comprehensive review investigates the growing adoption of electric vehicles (EVs) as a practical solution for environmental concerns associated with fossil fuel usage in mobility. The increasing demand for EVs underscores the critical importance of establishing efficient, fast-charging infrastructure, especially from the standpoint of the electrical power grid. The review systematically examines the planning strategies and considerations for deploying electric vehicle fast charging stations. It emphasizes their unique dual role as loads and storage units, intricately linked to diverse road and user constraints. Furthermore, the review underscores the significant opportunity surrounding these stations for the integration of distributed renewable energy sources. It thoroughly explores the challenges and opportunities intrinsic to the planning and localization process, providing insights into the complexities associated with these multifaceted stations. Renewable resources, including wind and solar energy, are investigated for their potential in powering these charging stations, with a simultaneous exploration of energy storage systems to minimize environmental impact and boost sustainability. In addition to analyzing planning approaches, the review evaluates existing simulation models and optimization tools employed in designing and operating fast charging stations. The review consolidates key findings and offers recommendations to researchers and grid authorities, addressing critical research gaps arising from the escalating demand for electric vehicle fast-charging infrastructure. This synthesis is a valuable resource for advancing understanding and implementing robust strategies in integrating EVs with the electrical power grid.

Optimizing Thd of Pi, Flc, and Anfis Controller for Electric Vehicle Fast Charging System: A Comparative Study

Optimizing Thd of Pi, Flc, and Anfis Controller for Electric Vehicle Fast Charging System: A Comparative Study

Evaluation of PV-based Buck-Boost and SEPIC Converters for EV Charging Applications

In recent decades, environmental issues have become an area of greatest concern due to changes in global climate conditions. The transportation sector is a major contributor to carbon dioxide emissions, accounting for more than 22.9% of total carbon dioxide emissions. At present, most vehicles run on gasoline/diesel as fuel which is unsustainable and unviable as fossil fuels produce carbon emissions and fuel costs are rising. To address these issues, electric vehicles (EVs) offer an attractive solution as alternative to internal combustion engine vehicles that use electricity as an energy source. It is logical to use renewable energy to charge vehicles, which makes renewable energy an end-to-end clean energy source. In electric vehicles, energy conversion plays an important role. In the energy conversion process, alternating current (AC) can be converted to direct current (DC), or direct current can be converted to alternating current. In EV fast charging applications, DC-to-DC conversion is used, which requires DC-to-DC converters. In this paper, a detailed evaluation of the Buck-Boost and Single-Ended Primary Inductance Converters (SEPIC) with PV as input is analyzed for EV charging applications to make it end-to-end clean energy. For this purpose, a 5-by-5 PV system with a Buck-Boost, SEPIC converters with particle swarm optimization technique is considered, which is simulated in a MATLAB/SIMULINK environment. The simulation results showed that the ripples in output are minimal in SEPIC which supports the smooth and efficient charging of EV battery.

Medium Voltage Direct Current Distribution System for an Electric Vehicle Fast Charging Park

There is an increasing shift towards the electrification of automobiles to meet zero-emission standards set by many nations. As electric vehicles become more common, their power demand on the power system becomes greater. A substantial modernization or upgrade of the current distribution power grid is required to meet such demand. Since most Level 3 fast chargers utilize DC power, medium voltage direct current (MVDC) provides a feasible alternative to the present AC distribution infrastructure. This study proposes an MVDC distribution model for powering a large EV park consisting of 40 EV charging stations with a 9.6-MW total power demand. Calculation and simulation are used to evaluate the model and compare it with an equivalent MVAC system. The outcomes show that implementing an MVDC distribution system is an efficient approach to meeting the increasing power demand for electric vehicles. The proposed 40-kV MVDC system power loss (13.1kW) is six times lower than that of the equivalent MVAC system (89.74kW). Further, since MVDC systems do not require AC step-down transformers and AC/DC converters at the equipment end, they can be a lower-cost option for powering large EV charging parks. The findings help enhance EV charging infrastructure, which expedites the adoption of EVs for reducing carbon emissions in the transportation sector.

Visualization of Lithium Plating Morphologies on Graphite Electrode By O perando X-Ray Tomography

The plating of lithium metal on graphite electrodes in Li-ion batteries is a major factor limiting the fast charging of electric vehicles. Lithium metal plating leads to the growth of dendritic structures that can pierce through the battery’s separator resulting in an internal short circuit and catastrophic failure of the battery. Moreover, the plating of lithium metal on graphite is not reversible, manifesting in poor Coulombic efficiency, severe reduction of the battery’s life expectancy, and safety issues. Understanding how and when plating occurs in Li-ion batteries is crucial in the development of strategies to prevent plating under fast charging conditions. Thus, we have conducted an operando X-ray tomographic microscopy experiment to directly monitor the plating of lithium metal in a Li/Graphite cell when applying electrolytes with the additives vinylene carbonate (VC) and Lithium bis(fluorosulfonyl)imide (LiFSI). The experiment was performed at the ID19 beamline (ESRF, France) where tomographic scans, linked with the lithiation state of graphite, made it possible to gain a strong understanding of the mechanisms behind Li-deposition and stripping at high current rates in addition to understand the effect of the VC and LiFSI additives.

Transformerless partial power converter topology for electric vehicle fast charge

AbstractIncreasing 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.

Battery Energy Storage System Optimal Sizing in a Battery Electric Vehicle Fast Charging Infrastructure

The growing number of battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV) brings the need of more fast charging stations across cities and highway stops. This charging stations toned to be connected to the electrical grid via existent facilities, causing constraints such as power availability.
 This study brings an approach for the planning and operation of such energy hubs by coping with this challenge by deploying a Battery-based Energy Storage System (BESS). With the BESS integration, it is expected to minimize utilization and overall energy costs, preventing infrastructure upgrades, and enhancing the integration of renewable energy resources.
 This approach sizes a stationary energy storage system with lithium-ion technology batteries through a co-optimization of the planning and operation stages, integrated in an electrical installation that will implement fast charging stations. This sizing is a result of an optimization based on the interior point algorithm, where the objective is to minimize the costs of maintenance, operation, and installation of a BESS, while properly modelling the different resources such as the BESS, the charging station and EV charging and PV generation.

Power electronics converters for an electric vehicle fast charging station based energy storage system and renewable energy sources: Hybrid approach

AbstractA hybrid method is proposed for electric‐vehicle (EV) fast charging station (FCS)‐based power electronics converters with energy‐storage‐systems (ESS) and renewable‐energy‐sources (RESs). The proposed approach is the combination of the fire hawk optimizer (FHO) and gradient boost decision tree (GBDT) algorithms; hence called as FHO‐GBDT approach. The key objective of the FHO‐GBDT approach is to lessen the peak power demand on the grid. The proposed method is incorporated into EV‐FCS with the capability of a mixture of RESs and energy‐storage‐systems. The capacities of energy‐storage aid in improving power‐demand by lessening the demand for peak power. The structure of the energy storage system minimizes the net cost of the DC micro‐grid (MG). The ESS is mostly composed of batteries, which are reused by EVs. The proposed approach and the ESS enable a decrease in obtaining the greatest amount of power possible from the power‐grid (PG). By then, the performance of the proposed approach is simulated in MATLAB, and it is compared to various existing methods. The simulation result shows that the proposed method offers more power than the existing methods.

Fast Charging Station for Electric Vehicles Based on DC Microgrid

Increasing numbers of electric vehicles (EVs) have led to an increased power demand from the grid. The fast-charging station requires very high power for charging the EVs in a short time (30mins). The rapid high-power (80-240kW) demand results in voltage instability in the power grid. It is important to reduce the impact on the grid due to fast charging of EVs. The effect on the grid due to EVs fast charging is included in this paper. The grid instability is visible during the fast-charging period of the battery. As a solution, a renewable energy source integrated DC microgrid using a multi-step constant current fast charging method is proposed to reduce the effect on the grid. Additionally, the proposed system provides solar PV and/or vehicle to grid power transfer during the no charging/the peak demand period of the grid. The simulation and analysis of the proposed system using the coulomb counting based state of charge estimation method is implemented to show the grid impact and reduction using DC microgrid. A hardware prototype is developed to validate the proposed fast charging method and also to reduce grid impact during the fast-charging operation.