DC Fast Charging Research Articles

User-needs-oriented shared DC charging resources optimal configuration and operation for improving EV penetration in old residential communities

The charging limitation of electric vehicles (EVs) in old residential communities (ORCs) derived from insufficient electricity capacity and parking spaces significantly impacts residents' quality of life and impedes urban sustainability. Considering economic and social factors, ORCs are likely to persist worldwide for the foreseeable future. To tackle these challenges, this paper proposes the scheme of shared DC fast charging stations to address the EV charging issues in ORCs. Specific methods involve minimizing the charging station spaces and charging infrastructure investment, while optimizing the photovoltaic (PV) and energy storage capacity. Additionally, a coordinated charging strategy based on dynamic price is designed to guide users in choosing the initial charging time, enhancing EV charging infrastructure utilization and EV penetration. This work is predominantly driven by human needs, integrating surveys on human behavior related to charging station locations and charging times. This case study is based on a real-life ORC in Shenzhen, China. By utilizing the proposed dynamic-pricing coordinated charging strategy tailored to the station capacity, the maximum EV penetration rate is to be achieved with satisfying EV charging demand. Furthermore, the implementation of dynamic pricing effectively guides users to adjust charging behavior, achieving the peak-shaving and valley-filling performance of load curves.

Enhancing Transient Response in a DC-DC Converter for Electric Vehicle DC Fast Charging Applications Using Fractional-Order PI Control

DC fast charging is critical for the widespread adoption of electric vehicles (EVs) due to its impact on convenience, economics, and environmental sustainability. Due to the critical role of DC fast charging in EV adoption, improving its efficiency and performance is paramount. This paper presents a Fractional-Order PI (FOPI) controller for obtaining a well-regulated output voltage of a Dual Active Bridge (DAB) converter, a widely used topology in EV applications. The proposed FOPI is validated to the conventional PI controller in a simulated DAB model that is relevant to DC fast charging applications. The evaluation is performed, and various time-domain parameters and performance indices to evaluate the dynamic response of the model are considered. The results are expected to demonstrate significant improvement in the converter’s transient and steady-state response using the proposed FOPI controller compared to the conventional PI controller, contributing to a more efficient and robust DC fast charging system. This improvement can translate to faster charging times, better stability, and potentially reduced stress on the EV battery during DC fast charging.

Modeling the Impact of Microstructure Variation on Charging Capability in Lithium-Ion Batteries

Battery models can be used to predict conditions ripe for lithium metal plating in the anode during rapid charging. One common procedure is to simulate a rapid charge using a pseudo-two-dimensional (P2D) model and determine if and when the minimum local potential reaches 0.0 V with respect to metallic lithium in the anode. This normally occurs at higher states of charge during a DC fast charging or rapid regenerative charging event. However, we have recently determined that three-dimensional (3D) models, while broadly agreeing with P2D results, demonstrate much variation in the in-plane and through plane direction, which P2D models cannot resolve. Because P2D models employ effective medium approximations, any “local” value in the P2D space along the through-plane coordinate represents an average across a slice of the domain. Therefore, it may be insufficient to use minimum anode potentials from P2D models as indicators of local plating and may only be representative of global lithium plating onset.The results of rapid-charge 3D microstructure simulations are compared to P2D results. This allows us to verify whether rapid charging induces negative local potentials at the anode active material surface that are left undetected in a P2D model. The expected result implies that the 3D microstructure model is necessary to predict the onset of lithium plating. We then extend our previous study to look at the impact of design changes on the microstructure performance, and then link the microstructure performance changes to performance metrics at the battery cell, module, pack, and vehicle level. Finally, the impact of variation in the microstructure domain considering particle size variation is quantified to understand tolerances that may be necessary when developing charging schemes.

Novel resistance control scheme for mitigating current sharing mismatches in parallel dual active bridge converters for DC fast charging stations

Abstract Dual Active Bridge (DAB) converters have gained popularity in electric vehicle charging stations due to their high efficiency and electrical isolation. As the demand for high-powered devices and large-capacity energy storage systems grows, charging systems that integrate multiple interconnected DAB modules are emerging as a promising solution. However, prolonged operation of these modules at high power levels can cause parameter deviations from the initial DAB circuit, resulting in power variations between modules. To overcome parameter deviations, this study presents an enhanced power control approach based on output resistance adjustment, intending to achieve consistent output capacity for multiple DAB modules. In the proposed enhanced power control method, the output resistance of the DAB module is considered to be controllable, and the current-sharing mismatches among DAB modules are fed back to tune the converter output resistance for mitigating current mismatches between modules. Thanks to the proposed control method, each DAB module can operate autonomously and balance the charging current between modules. When one DAB module is suddenly cut out of the system, the other DAB modules still maintain their stability with fully guaranteed load capacity. To demonstrate the feasibility of the enhanced control approach, the small signal model of the DAB system with three modules is derived together with its frequency-amplitude diagram. Then, the effect of virtual resistance on current balancing is comprehensively tested, and the proper control signal with virtual resistance is added to the DAB voltage control loop. The simulation results have demonstrated the reliability of the proposed control method with the ability to balance the charging current between modules and stabilize the system when a single DAB module fails.

Advancing Electric Vehicle Infrastructure: A Review and Exploration of Battery-Assisted DC Fast Charging Stations

Concerns over fossil fuel depletion, fluctuating fuel prices, and CO2 emissions have accelerated the development of electric vehicle (EV) technologies. This article reviews advancements in EV fast charging technology and explores the development of battery-assisted DC fast charging stations to address the limitations of traditional chargers. Our proposed approach integrates battery storage, allowing chargers to operate independently of the electric grid by storing electrical energy during off-peak hours and releasing it during peak times. This reduces dependence on grid power and enhances grid stability. Moreover, the transformer-less, modular design of the proposed solution offers greater flexibility, scalability, and reduced installation costs. Additionally, the use of smart energy management systems, incorporating artificial intelligence and machine learning techniques to dynamically adjust charging rates, will be discussed to optimize efficiency and cost-effectiveness.

A Comprehensive Review of Developments in Electric Vehicles Fast Charging Technology

Electric vehicle (EV) fast charging systems are rapidly evolving to meet the demands of a growing electric mobility landscape. This paper provides a comprehensive overview of various fast charging techniques, advanced infrastructure, control strategies, and emerging challenges and future trends in EV fast charging. It discusses various fast charging techniques, including inductive charging, ultra-fast charging (UFC), DC fast charging (DCFC), Tesla Superchargers, bidirectional charging integration, and battery swapping, analysing their advantages and limitations. Advanced infrastructure for DC fast charging is explored, covering charging standards, connector types, communication protocols, power levels, and charging modes control strategies. Electric vehicle battery chargers are categorized into on-board and off-board systems, with detailed functionalities provided. The status of DC fast charging station DC-DC converters classification is presented, emphasizing their role in optimizing charging efficiency. Control strategies for EV systems are analysed, focusing on effective charging management while ensuring safety and performance. Challenges and future trends in EV fast charging are thoroughly explored, highlighting infrastructure limitations, standardization efforts, battery technology advancements, and energy optimization through smart grid solutions and bidirectional chargers. The paper advocates for global collaboration to establish universal standards and interoperability among charging systems to facilitate widespread EV adoption. Future research areas include faster charging, infrastructure improvements, standardization, and energy optimization. Encouragement is given for advancements in battery technology, wireless charging, battery swapping, and user experience enhancement to further advance the EV fast charging ecosystem. In summary, this paper offers valuable insights into the current state, challenges, and future directions of EV fast charging, providing a comprehensive examination of technological advancements and emerging trends in the field.

Power management and optimized control of hybrid PV-BESS-grid integrated fast EV charging stations

The rapid growth of on-road electric vehicles (EVs) empowered the increasing demand for charging stations, hindering widespread EV adoption due to factors like limited range and insufficient charging infrastructure. To address these concerns, the implementation of DC fast charging stations (FCSs) has emerged as a solution to reduce charging time and promote industry adoption. However, the integration of such FCSs poses challenges in terms of power management, power quality and charging service stability, especially in weak grid infrastructures. This paper proposes a power management strategy for a DC-FCS located near highways, aiming to provide stable, fast, and reliable charging services to EVs while minimizing grid dependency. The proposed strategy incorporates various energy sources and operation modes to ensure charging service stability. Additionally, an optimized tuning control based on an improved Snake optimization (ISO) algorithm is introduced to enhance the performance of the grid-connected voltage source inverters (VSIs) in the DC-FCS. The optimized tuning method using the proposed algorithm shows superior performance compared to other methods. Simulation and experimental tests validate the effectiveness of the proposed system, showcasing its potential for efficient management, stable charging service, and improved power quality in the DC-FCS.

DC fast charging stations for electric vehicles: A review

AbstractThe expansion of the DC fast‐charging (DCFC) network is expected to accelerate the transition to sustainable transportation by offering drivers additional charging options for longer journeys. However, DCFC places significant stress on the grid, leading to costly system upgrades and high monthly operational expenses. Incorporating energy storage into DCFC stations can mitigate these challenges. This article conducts a comprehensive review of DCFC station design, optimal sizing, location optimization based on charging/driver behaviour, electric vehicle charging time, cost of charging, and the impact of DC power on fast‐charging stations. The review is closely aligned with current state‐of‐the‐art technologies and encompasses academic research contributions. A critical assessment of 146 research articles published from 2000 to 2023 identifies research gaps and explores avenues for future study based on the literature review.

ELECTRIC VEHICLE CHARGING INFRASTRUCTURE: A COMPARATIVE REVIEW IN CANADA, USA, AND AFRICA

This research paper comprehensively analyzes electric vehicle (EV) charging infrastructure in Canada, the USA, and Africa. Examining technological landscapes, regulatory frameworks, funding mechanisms, and socio-environmental impacts, the study reveals key trends and challenges. The technical overview encompasses Level 1, Level 2, and DC fast charging, focusing on interoperability and advancements. Government grants, public-private partnerships, and international funding drive infrastructure funding, fostering job creation and economic growth. The analysis reveals diverse cultural and behavioral factors influencing EV adoption, emphasizing the need for tailored communication strategies. The future envisions ultra-fast charging, wireless technologies, and smart ecosystems, demanding collaborative solutions to grid capacity and standardization challenges. This research contributes valuable insights for policymakers, industry stakeholders, and researchers, guiding the sustainable development of EV charging infrastructure globally. 
 Keywords: Electric Vehicles, Charging Infrastructure, Sustainability, Socioeconomic Impact.

A Bilevel EV Charging Station and DC Fast Charger Planning Model for Highway Network Considering Dynamic Traffic Demand and User Equilibrium

The rapid electric vehicle (EV) adoption and relatively short EV driving range urge city planners to expand charging infrastructure (i.e., EV charging stations (EVCSs) and direct current fast chargers (DCFCs)) in the highway network for supporting long-distance intercity EV travels. To properly address distinct roles as well as interactions of the EVCS planner, traffic network, power distribution networks (PDNs), and drivers, this paper explores a bilevel planning model in which the upper level determines EVCS and DCFC construction plans and the two lower-level subproblems describe the user equilibriumbased traffic assignment model of the traffic network and the operation model of PDNs. Moreover, the statistical charging time is modeled in the traffic network subproblem as a function of statistical charging demand and the number of DCFCs, leveraging the macro traffic pattern and micro charging behavior of individual drivers with balanced accuracy and computational complexity. The proposed model also captures the impacts of social factors, charging infrastructure, and driver behaviors on dynamic EV traffic demands. Reformulation and linearization techniques are applied to convert the proposed bilevel problem into a tractable single-level mixed-integer linear programming model for effective computation. The effectiveness of the proposed approach is tested on an intercity highway network with multiple PDNs. The findings from numerical case studies highlight the important interplay among the construction plans of EVCSs and DCFCs, the PDN constraints, the user equilibrium traffic network, and the EV drivers. Case studies illustrate the feasibility and necessity of considering the number of DCFCs to calculate the macro-perspective charging time in the user equilibrium traffic network model. The dynamic traffic demand, induced by social factors and traffic demand elasticity, was also found to be a crucial factor in reshaping EV traffic. Thus, properly considering these important factors would lead to a more accurate quantification of traffic demands and ultimately result in a more reasonable charging facility construction plan.

Linking Microstructure Modeling of Lithium-Ion Batteries during Rapid Charging to System Performance

Battery models can be used to predict conditions ripe for lithium metal plating in the anode during rapid charging. One common procedure is to simulate a rapid charge using a pseudo-two-dimensional (P2D) model and determine if and when the minimum local potential reaches 0.0 V with respect to metallic lithium in the anode. This normally occurs at higher states of charge during a DC fast charging or rapid regenerative charging event. However, we have recently determined that three-dimensional (3D) models, while broadly agreeing with P2D results, demonstrate much variation in the in-plane and through plane direction, which P2D models cannot resolve. Because P2D models employ effective medium approximations, any “local” value in the P2D space along the through-plane coordinate represents an average across a slice of the domain. Therefore, it may be insufficient to use minimum anode potentials from P2D models as indicators of local plating and may only be representative of global lithium plating onset.The results of rapid-charge 3D microstructure simulations are compared to P2D results [1,2]. This allows us to verify whether rapid charging induces negative local potentials at the anode active material surface that are left undetected in a P2D model. The expected result implies that the 3D microstructure model is necessary to predict the onset of lithium plating. We then extend our previous study to look at the impact of design changes on the microstructure performance, and then link the microstructure performance changes to performance metrics at the battery cell, module, pack, and vehicle level.References J. S. Lopata, T. R. Garrick, F. Wang, H. Zhang, Y. Zeng and S. Shimpalee, ECSarXiv (2022).J. S. Lopata, T. R. Garrick, F. Wang, H. Zhang, Y. Zeng and S. Shimpalee, J Electrochem Soc, 170, 020530 (2023).

Design and Simulation of DC Fast Charger for Electric Vehicle

Elektrikli araçlar geleneksel fosil yakıtlı araçlarla kıyasla sıfır emisyon, azaltılmış bakım maliyetleri, daha yüksek motor verimliliği, gelişmiş sürüş konforu gibi önemli avantajlar sunmaktadır. Ancak, sınırlı menzil kapasitesi, şarj altyapısının eksikliği ve uzun şarj süreleri gibi zorluklar, elektrikli araçların yaygın olarak benimsenmesinin önünde önemli engeller oluşturmaktadır. Elektrikli araçların geliştirilmesi sürecinde, büyük bir öneme sahip olan kritik bileşenler arasında, batarya ve şarj sistemleri dikkate değer bir role sahiptir. Bu çalışma, 45kWh pil kapasitesiyle donatılmış bir elektrikli araç için 90kW DA hızlı şarj cihazının tasarımı ve simülasyonuna odaklanmaktadır. Önerilen sistem ile bataryanın %20’den %80’e doluluk oranına ulaşması için gereken toplam şarj süresinin 30 dakikanın altına indirilmesi hedeflenmektedir. Tasarlanan DA hızlı şarj cihazı; aktif güç faktörü düzeltici işlevini gerçekleştiren bir AA/DA dönüştürücü ve şarj işlevini gerçekleştiren bir DA/DA dönüştürücüden oluşmaktadır. Önerilen hızlı şarj sisteminin geçerliliği ve etkinliği simülasyon sonuçları ile doğrulanmıştır.

ZVS Boundary Analysis and Design Guideline of MV Grid-Compliant Solid-State Transformer for DC Fast Charger Applications

A solid-state transformer comprising a cascaded H-bridge and a dual-active bridge converter is a promising solution for a megawatt medium voltage DC fast charger application. The new IEEE Std 1547.9-2022 comprehensively discusses extending the minimum reactive power capability to electric vehicle chargers. This paper analyzes the impact of operating the grid compliant single-phase solid-state transformer on the overall system. The impact of the DC-link voltage due to the single-phase implementation of the H-bridges on the dual-active bridge converter zero-voltage switching mode at light-load operation is highlighted. The system’s operational boundary is analyzed, which defines the reactive power capability limit while ensuring the dual-active bridge converter zero-voltage switching mode operation for the defined operating points. This zero-voltage switching mode boundary analysis is then used to develop a design guideline as part of the solid-state transformer design process. The proposed guideline allows a simultaneous design of a DC-link capacitor and dual active bridge inductance to ensure zero-voltage switching mode for the defined operating points. It leads to DC-link capacitance reduction that offers cost-and footprint-savings. The proposed concept is validated through simulations and experimental results. Further, a potential benefit analysis is provided to emphasize the effectiveness of the proposed concept. A supplementary video is included to showcase the system’s dynamic active and reactive power operation.

A system efficiency improvement of DC fast-chargers in electric vehicle applications: Bypassing second-stage full-bridge DC-DC converter in high-voltage charging levels

A system efficiency improvement of DC fast-chargers in electric vehicle applications: Bypassing second-stage full-bridge DC-DC converter in high-voltage charging levels

3D Microstructure Modeling of Lithium Ion Batteries during Rapid Charging

Battery models can be used to predict conditions ripe for lithium metal plating in the anode during rapid charging. One common procedure is to simulate a rapid charge using a pseudo-two-dimensional (P2D) model and determine if and when the minimum local potential reaches 0.0 V with respect to metallic lithium in the anode. This normally occurs at higher states of charge during a DC fast charging or rapid regenerative charging event. However, we have recently determined that three-dimensional (3D) models, while broadly agreeing with P2D results, demonstrate much variation in the in-plane and through plane direction, which P2D models cannot resolve. Because P2D models employ effective medium approximations, any “local” value in the P2D space along the through-plane coordinate represents an average across a slice of the domain. Therefore, it may be insufficient to use minimum anode potentials from P2D models as indicators of local plating and may only be representative of global lithium plating onset.In this work, the results of rapid-charge 3D microstructure simulations are compared to P2D results. This allows us to verify whether rapid charging induces negative local potentials at the anode active material surface that are left undetected in a P2D model. The expected result implies that the 3D microstructure model is necessary to predict the onset of lithium plating.

Multi-layer control on DC fast charging stations equipped with distributed energy storages and connected to distribution network: Managing power and energy following events

In this paper, DC fast charging (DCFC) stations are integrated into the distribution network (DN). The designed DCFC stations are equipped with several charging devices (CDs) at different rated powers, which can charge electric vehicles (EVs) at various power levels through charging points (CPs). A central control system (CCS) is designed for each DCFC, which is applied for managing its local controllers. The CDs also use distributed energy storage (DES) alongside the DC chargers in order to increase the speed of the charging process and utilize the stored energy for improving the DN operation. The DN central controller scheme is as well designed to control the CCS of DCFCs and make positive effects on the upstream distribution grid. The CCS of DN, in addition to managing the CCS of DCFCs, is responsible for controlling the charge level of DCFCs according to four control strategies in each station including improving voltage fluctuations on the DN side, injecting reactive power from DCFCs to DN during a fault on the DN side, increasing DN resiliency by supplying critical loads in the time of upstream network outage, and supplying loads with time-varying active-reactive powers. The nonlinear simulations using MATLAB-SIMULINK demonstrate that the proposed strategies can effectively improve the performance of DN in addition to accurate control of the charging process in the EVs.

Technical Review and Survey of Future Trends of Power Converters for Fast-Charging Stations of Electric Vehicles

The development and implementation of electric vehicles have significantly increased and are profoundly reshaping the automotive sector. However, long charging times, limited driving range, and difficulties as to suitable charger converter design are the main limitations of the adoption of EV technology. DC fast-chargers offer the best solution for mitigating the charging time problems of EVs. This paper provides an extensive review of the status of the technical development of fast-charging infrastructure architectures and standards, and a classification of fast-charging methods. Key power electronic converter topologies for fast-charging systems, with their advantages and comparisons, are also addressed.

Hybrid Energy Storage System Taking Advantage of Electric Vehicle Batteries for Recovering Regenerative Braking Energy in Railway Station

Nowadays, nations are moving toward the electrification of the transportation section, and the widespread development of EV charging stations and their infrastructures supplied by the grid would strain the power grid and lead to overload issues in the network. To address this challenge, this paper presents a method for utilizing the braking energy of trains in railway stations to charge EVs located in strategic areas like park-and-ride regions close to railway stations improving energy efficiency and preventing grid overload. To validate the feasibility of the proposed system, a metro substation in Milan city is considered as a case study located in outskirts of the city and contains large number of parking space for vehicles. Three different scenarios are evaluated including DC fast charging station, AC low charging station and collaborative hybrid energy storage based AC charging station as EV charging station type. The results are studied for different EV population number, charging rate and the contractual power grid. Meanwhile, the possibility of proposed system in participating as V2G technology and taking advantage of the EV’s batteries to provide ancillary support to accelerating trains is investigated regarding peak shaving objective. The results indicated that the suggested interconnected system operates effectively when a significant quantity of EVs are parked at the station. However, the results revealed that the performance of the proposed system is notably influenced by other factors and a limited number of EVs during the early morning and late evening periods. Overall, this study confirms the feasibility of energy transfer between two types of transportation means in intermodal areas.

A Novel MIMO Control for Interleaved Buck Converters in EV DC Fast Charging Applications

This brief proposes a new multiple input multiple output (MIMO) control for off-board electric vehicle (EV) dc fast chargers. The proposed feedback matrix design avoids multiple tuning of controllers in multiple and interconnected loops while improving the performance of interleaved dc buck converters over classical PI/PID controls. The innovative features of the presented strategy are the reference current monotonic tracking from any initial state of charge with an arbitrarily fast settling time and the fast compensation of both load variations and imbalances among the legs. Numerical results validate the performance improvements of the proposed discrete-time MIMO algorithm for interleaved buck converters over classical PI/PID controls. Full-scale hardware-in-the-loop (HIL) and scaled-down prototype experimental results prove the feasibility and effectiveness of the proposal.

Real-Time Open-Circuit Fault Diagnosis Method for T-Type Rectifiers Based on Median Current Analysis

T-type rectifiers are widely used in DC fast chargers, super uninterrupted power supplies, renewable energy, and other low-voltage and medium-voltage rectifier applications. High equipment reliability and high-quality power are often required in these applications but are damaged by the transistor open-circuit fault. This paper proposes a novel real-time open-circuit fault diagnosis method for the T-type rectifier based on median current analysis. The method only uses the three-phase currents to obtain the median current and realize the diagnosis. In the rectifier, partial open-circuit faults result in weak fault signals, making the diagnosis challenging. To solve this, the median current obtained by the currents performs fault frequency modulation to enhance the fault signals at first. Then, the ratio of the fundamental frequency to the dc component is used to realize fault detection. The inner/outer fault is identified at the same time. At last, the fault transistor is located by simple change point detection. The change points determine the fault phase and transistor fault. The effectiveness and robustness of the proposed method are verified by the experiment results.