Electric Vehicle Charger Research Articles

Review of Power Quality and Stability of EV Charging with Grid and PV Solar

As a sustainable mode of transportation, electric vehicles (EVs) are gaining popularity, and their integration with the power grid and photovoltaic (PV) solar systems is essential for their widespread adoption. Solar PV and EV systems have improved based on the generation and demands of the power grid. However, incorporating EV chargers with the grid and PV solar systems can cause power quality issues and stability problems that can impact the charger's performance and affect the charging procedure. EV technologies are divided into two major components: electric propulsion systems and EV charging systems. The electric propulsion system delivers the necessary energy for the EV motor in an EV system. In addition, with higher penetration, EVs and PVs are anticipated to emerge as new participants in the energy market operation and can play a crucial role in redefining the market. Many have integrated into the electricity network to reach renewable energy sources (RES), such as wind and solar PV. The study concludes that continued research and development are necessary to upgrade the power quality and solidness of EV charging frameworks, to ensure the seamless integration of PV solar systems and electric vehicles into the grid, and to promote sustainable transportation.

An industrial design of 400 V – 48 V, 98.2% peak efficient charger usingE‐mode GaNtechnology with wide operating ranges for xEV applications

AbstractThis paper offers a wide‐operating range electric vehicle charger design by employing an interleaved inductor–inductor–capacitor iL2C DC–DC converter. It uses two parallel L2C converters with 8‐GaN switches on the primary side and a shared rectifier circuit on the secondary side, which it also enhances the circulating current, conduction losses, and current sharing. For iL2C converter, a constant voltage charging mode of operation is designed, also it proposes a hybrid control scheme of variable frequency + phase shift modulation (VFPSM). The entire concept is designed, simulated, and validated with a rated input voltage and load voltage of three different load conditions with converter line and load regulations are analyzed. To evaluate controller and converter performance, the idea is proven experimentally for variable load condition of full load, half load, light load with a rated input and output voltage of 400Vin–48V0. In addition, line regulation is also performed and validated for wide input voltage application of 300Vin–500 Vinwith an output voltage of 48V0at full load and peak efficiency of 98.2% is determined. Further, to provide the system effectiveness converter efficiencies are presented at various load operations from 3.3 kW to 330 W.

Assessing levels of urban public electric vehicle charging service in different-level cities: A case study of the 35 cities of the Chengdu–Chongqing Urban Agglomeration, China

Urban Public Electric Vehicle Charger (PEVC) services are crucial for sustainable development in countries with low rates of single-family home ownership, promoting vehicle electrification and contributing to the achievement of the Sustainable Development Goals (SDGs). PEVC provision differs across Chinese regions and cities, especially among various city levels. However, this disparity has not been adequately addressed, impeding strategic PEVC development planning. To clarify these disparities, this study combines an analysis of the supply-demand and usage costs of PEVCs, which are the main factors affecting vehicle electrification, and evaluates the disparities in PEVC service among 35 cities of varying levels in Chengdu–Chongqing Urban Agglomeration. The results indicate that mega-cities demonstrate the highest service levels, attributed to their robust supply capacity and well-developed pricing mechanisms, but they also face higher actual demand pressures. Medium-sized and small cities show intermediate PEVC service, while large cities unexpectedly demonstrate the lowest supply-demand level and highest usage costs due to the mismatch between PEVC supply and demand size. Additionally, the study highlights the priority of PEVC station scale in enhancing the supply. These findings inform policymakers in shaping targeted strategies and policies, adapting to the varying PEVC service levels across different cities.

Bidirectional wide range and high voltage gain buck‐boost DC‐DC converter for EV chargers empowering V2G‐G2V applications

AbstractThis paper proposes a new wide range bidirectional buck‐boost dc‐dc converter with improved voltage gain in either forward (discharging) or backward (charging) direction for electric vehicle (EV) applications. The converter has high‐voltage gain ratio with no theoretical limits in the output voltage in both directions, and presents a good balance between the component count, number of conducting components, semiconductor device ratings, having direct connection between input and output terminals, and efficiency which makes it a practical solution for the EV charger levels 1, 2, and 3 power converter unit. The operating principle, steady‐state characteristics including the current and voltage stress of the switches, and comparison with other state of the art dc‐dc bidirectional converters are explained in detail. In order to validate the theoretical analysis, a 500 W, 200 V or 40 V to 180 V laboratory prototype is implemented. The obtained results confirm the applicability of this structure and demonstrate a peak efficiency of 97.2% in the forward and 97.6% in the backward direction modes of operation.

Advanced off-board bidirectional electric vehicle charger with enhanced power quality and supporting grid resilience

Advanced off-board bidirectional electric vehicle charger with enhanced power quality and supporting grid resilience

Control method based on real–imaginary decomposition at the switching frequency for multiple active bridge converters

AbstractIsolated multiple port DC/DC converters, such as the Multiple Active Bridge (MAB) converter, have many recent applications, such as interconnection between grids, isolated uninterruptible power sources (UPSs) and electric vehicle chargers. MAB converter is an attractive solution from the point of view of the hardware because of its symmetry and its capability to be extended to any number of bridges with a moderate number of components. However, the main challenge of this converter is the control method in order to achieve independent control between the different ports and to minimize recirculating currents. For that reason, three‐port power converters have been already investigated, but many improvements can be done for a larger number of ports. This paper proposes to use a Fourier decomposition for the main power signals to separate their real and imaginary parts. As the signals work at the switching frequency, this decomposition is developed with analog electronics. Based on that, a general control method for regulating the power at the different ports is presented using the first harmonic component, which delivers most of the power. In this proposal, two nested control loops ensure accuracy for the DC power flow. Simulation and experimental results validate the proposal.

An analytical framework for assessing equitable access to public electric vehicle chargers

Inequitable distribution of public electric vehicle (EV) charging facilitiesmay result in disparities in charging accessibility, potentially impeding the uptake of EVs. In response, this paper proposes an analytical framework to assess the accessibility-based equity of public EV charging infrastructure systematically, using Hong Kong (HK) as the study area. The results demonstrated severe spatial inequity of charging facilities in central, north, and southwest HK. Meanwhile, the Gini index of all public EV charger types for the total population was 0.751, and the indices for low-income, low-education level, and government-funded housing subgroups were 0.791, 0.809, and 0.893, respectively. These indicated considerable horizontal and vertical inequity from a statistical perspective. Furthermore, age, education level, family structure, and housing type were identified as significant socio-demographic characteristics correlated to the accessibility-based equity of public EV charging infrastructure in HK. These findings are expected to be useful for future policymaking and infrastructure planning.

Power Quality Improvement and Signal Conditioning of PV Array and Grid Interfaced Off-Board Charger for Electric Vehicles with V2G and G2V Capabilities

Power Quality Improvement and Signal Conditioning of PV Array and Grid Interfaced Off-Board Charger for Electric Vehicles with V2G and G2V Capabilities

Low Harmonics Plug-in Home Charging Electric Vehicle Battery Charger BMS State of Charge Balancing using Priority and Sequencing Technique

Poor battery state of health (SOH) or unit cell replacement of a damaged battery may cause an imbalance in the state of charge (SOC) or battery voltage terminal of electric vehicle (EV) batteries, which can negatively impact EV performance and EV batteries when charging. Battery Management System (BMS) monitor charges safely and efficiently. BMS can maximize battery life, can estimate SOC and State of health (SOH). EV Charger charge batteries individually in sequence (parallel) or, at once while in series connection. BMS cell balance controls battery charging in series or parallel using macro charging circuits. This study discusses series motor DC drive Electric Car (EC) Battery Management System (BMS) utilizing macro charging circuit and cell balancing control method. The MATLAB/Simulink software used to test the control algorithm shows that the proposed BMS cell balancing algorithm works effectively and meets our expectations.

Reconfigurable LLC Resonant Converter for Bidirectional Electric-Vehicle Chargers

Reconfigurable <i>LLC</i> Resonant Converter for Bidirectional Electric-Vehicle Chargers

Safety assessment of wireless chargers for electric vehicles considering thermal characteristics.

This study employs the transient finite element method and electromagnetic heat transfer theory to assess the heating generated by high-power wireless chargers during electric vehicle charging. The analysis includes simulating and analyzing the temperature distribution of two different types of shielding plates of the wireless charger and the specific absorption rate (SAR) and head temperature rise of both adults and children in close proximity to the charger. Simulation results show that the maximum temperature rise of the copper shielding plate is 16°C lower than that of the aluminum shielding plate after charging for 1h. This temperature increase does not affect the chassis' s equipment. Regarding human safety, the induced electric field strength and SAR values in the child's head tissue are higher than those in the adult, meeting the International Commission on Non-Ionizing Radiation Protection (ICNIRP) limits. When the initial temperature is set to 37°C, the temperature rise in the heads of both adults and children is approximately equal after 1h of charging, reaching a maximum temperature rise of 0.21 and 0.23°C, respectively. These values remain below the thermal limit of ICNIRP (2°C for Type 2 tissues). The findings indicate that the copper shielding plate can provide both electromagnetic shielding and heat dissipation functions, and the electromagnetic exposure absorbed by the human body and head temperature rise within safe ranges.

Reliability of Open Public Electric Vehicle Direct Current Fast Chargers.

The aim was to systematically evaluate the usability of all public electric vehicles (EV) direct current fast chargers (DCFC) in the San Francisco region. To achieve a rapid transition to EVs, a highly reliable and easy to use charging infrastructure is critical to building confidence among consumers. The functionality and usability of all 182 open, public DCFC charging stations with CCS connectors (combined charging system) in the 9 counties of the Bay Area were tested (655 electric vehicle service equipment (EVSE) ports). An EVSE was classified as functional if it charged an EV for 2minutes. Overall, 73.3% of the 655 EVSEs were functional. The causes of the nonfunctioning EVSEs (23.5%) were blank or unresponsive screens or error messages; payment system failures; charge initiation failures; network failures; or broken connectors. In addition, the cable was too short to reach the EV inlet for 3.2% of the EVSEs. A random sampling of 10% of the EVSEs, approximately 8 days after the first evaluation, found no overall change in functionality. The level of functionality found with field testing conflicts with the 95-98% uptime reported by the EV service providers (EVSPs) who operate the EV charging stations. There is a need for precise and verifiable definitions of uptime, downtime, and excluded time, as applied to public EV chargers. The level of failure of the existing public EV DCFC charge infrastructure highlights the importance of improving the system design and maintenance to improve adoption of EVs.

Retracted: High-Performance Control Simulation of PFC Converter for Electric Vehicle Charger

Retracted: High-Performance Control Simulation of PFC Converter for Electric Vehicle Charger

Efficiency optimisation and converterless PV integration by applying a dynamic voltage on an LVDC backbone

A low-voltage DC (LVDC) backbone with a battery energy storage system (BESS) and distributed photovoltaics (PV) is proven to be a more efficient alternative compared to the traditional AC architecture. However, previous research has also proven the fact that the benefit strongly depends on the operating voltage level. In this study, a dynamic backbone voltage on architectures with and without distributed maximum power point trackers (MPPT) is investigated. The dynamic voltage is driven by a multi-objective optimisation algorithm that will minimise the cable and converter loss. Applying the dynamic voltage with MPPT leads to a massive decrease of the loss compared to a static voltage with MPPT. Although, if the optimisation objective is extended with the minimisation of the PV curtailment loss, the MPPT can be eliminated without causing a considerable curtailment loss while maintaining a high efficiency. The sensitivity analysis showed that even when the cable is longer, the orientations of the PV distributed systems are different or the PV system is exposed to dynamic shading, dynamic voltage without maximum power point is still competitive compared to the alternatives. However, heavy static shading conditions could cause a notable shift of the MPP making it very hard to track this operating point by the algorithm. The elimination of the MPPT leads to a simpler design and installation, lower investment costs and a reduction of the raw material use. The proposed strategies and architectures are hence favourable to be applied in LVDC backbones massively fed by roof-mounted or building-integrated PV systems. This study provides the general approach which could be extended with distributed electric vehicle chargers.

A cost-effective and high-efficient EV shared fast charging scheme with hierarchical coordinated operation strategy for addressing difficult-to-charge issue in old residential communities

Charging infrastructures are being deployed widely in urban and rural areas to solve the so-called “last one-kilometer” charging problem. However, for old residential communities, the existing difficult-to-charge issue is not easily solved solely by the widespread deployment of charging infrastructure owing to limited spaces, complex reconstruction, and huge costs. In this context, this paper introduces a cost-effective and high-efficient shared fast charging scheme for old residential communities. The comprised registration-based queuing charging mechanism is proposed to schedule electric vehicle (EV) charging. An integrated and multi-stage power electronic device called smart interlinking unit (SIU) is introduced for grid reconstruction. The SIU-based charging station architecture features flexible control capability, enabling DC power supply for terminal EV chargers. For this architecture, a novel hierarchical coordinated operation strategy is designed, comprising the upper-level real-time vehicle-to-grid (V2G) dispatching and lower-level coordination strategies. Case studies demonstrate that the proposed scheme could accommodate 40 % EV penetration, while exhibiting a significant decline in system investment and occupied area compared to the slow charging scheme. Additionally, a 1.3 % improvement in average transfer efficiency is verified under this architecture. The proposed strategy is proven to realize a prominent power peak-shaving and valley-filling, effective transformer load balance, and DC voltage restoration.

Prospective Analysis of Massive Integration of Electric Vehicle Chargers and Their Impact on Power Quality in Distribution Networks

The increasing presence of electric vehicles (EVs) requires a thorough understanding of their impact on distribution assets. EV chargers are characterized as nonlinear and multi-state loads due to their unique electrical consumption patterns. This paper presents a comprehensive study focused on modelling diverse EV charging units deployed in the industrial, commercial, and residential sectors. To conduct this analysis, a simulation environment utilizing the ETAP tool is employed, taking into account time variations. This approach facilitates the comprehension and anticipation of the effects that EV charging may impose on distribution networks, thereby supporting well-informed decision-making for the adaptation and enhancement of the electrical system. Detailed data on current and voltage from operational EV charging stations were collected to create consumption, current, voltage, and harmonic profiles for these charging units. Subsequently, general models or libraries applicable to Level 1, Level 2 and Level 3 EV chargers available in Colombia were developed. These models underwent rigorous validation and were subjected to a comprehensive analysis using the IEEE 13-bus test system. The research yielded valuable insights and conclusions regarding the integration of EV chargers into the current Colombian distribution systems, as well as the potential impact of adopting these devices on power quality issues within the distribution grid. This study contributes to the improved management of distribution assets, thereby facilitating the integration of sustainable electric mobility in the national electrical system.

Grid integrated multifunctional EV charging infrastructure with improved power quality

This paper presents a grid integrated multifunctional electric vehicle (EV) charging infrastructure to power the EV batteries and simultaneously improve grid power quality. The EV charger control function is designed to operate the charger in grid-to-vehicle (G2V), vehicle-to-grid (V2G), and proposed active-filtering-mode (AFM) operating modes. In AFM mode, the proposed self-tuning filter (STF) based control algorithm effectively compensates the grid current harmonic distortions arising from nonlinear charging station load. Furthermore, the charger controller uses STF to estimate the synchronizing voltage templates for reference current generation instead of conventional phase-locked-loop (PLL) and second-order generalized integrator (SOGI) to address the nonideal grid voltage conditions. The charger controller is designed to operate in AFM operating mode simultaneously with G2V and V2G operating modes. Furthermore, to achieve these multifunctional operations in a single charger, the power electronics circuitry of the charger is developed by using an AC/DC voltage source converter and a DC/DC dual active bridge (DAB) converter. The embedded isolation in the DAB converter ensures the safety of the EV batteries from the disturbance in the AC and DC side of the charger. Furthermore, a 3.6 kVA EV charger prototype is developed in the laboratory to show the effectiveness of the control techniques.

Optimal locating and sizing of charging stations for large‐scale areas based on GIS data and grid partitioning

AbstractThis research proposes an optimisation model for identifying the optimal locations and sizes of public charging stations for large‐scale areas based on geographic information system (GIS) data and grid partitioning. A grid partitioning technique is utilised to generate subareas and investigate the demand for electric vehicle (EV) chargers calculated based on the number of EVs in each subarea. The optimal locations are formulated as a maximum covering location problem and solved by integer programming to ensure that all vehicle access subareas, according to the GIS data, are covered by charging stations. The sizes of charging stations are formulated as a knapsack problem and solved by the EV‐charge point ratio to guarantee each subarea has the appropriate number of chargers. The Voronoi diagram is integrated to estimate vehicle density and improve visualisation. The model is extended to include potential power loss reduction by adjusting the distribution of chargers in relation to the proximity to electrical substations. The developed methodology has been implemented by the whole country area of Thailand, which covers an area of approximately 510,000 km2. The study results are represented in a map blueprint that is very useful in strategic planning to support the so‐called EV30@30 government policy's ambitious national target of 2,050,000 units of EVs in 2030.

Classifying Invention Objectives of Electric Vehicle Chargers through Natural Language Processing and Machine Learning

The gradual adoption of electric vehicles (EVs) globally serves as a crucial move toward addressing global decarbonization goals for sustainable development. However, the lack of cost-effective, power-efficient, and safe chargers for EV batteries hampers adoption. Understanding the research needs and identifying the gaps in EV charger innovation informs investments and research to address development challenges. This study developed a unique text mining workflow to classify themes in EV charger technology and product development by analyzing U.S. patent award summaries. The text mining workflow combined the techniques of data extraction, data cleaning, natural language processing (NLP), statistical analysis, and unsupervised machine learning (ML) to extract unique themes and to visualize their relationships. There was a 47.7% increase in the number of EV charger patents issued in 2022 relative to that in 2018. The top four themes were charging station management, power transfer efficiency, on-board charger design, and temperature management. More than half (53.8%) of the EV charger patents issued over the five-year period from 2018 to 2022 addressed problems within those four themes. Patents that addressed wireless charging, fast charging, and fleet charging accounted for less than 10% each of the EV charger patents issued. This suggests that the industry is still at the frontier of addressing those problems. This study further presents examples of the specific EV charger problems addressed within each theme. The findings can inform investment decisions and policymaking to focus on R&amp;D resources that will advance the state of the art and spur EV adoption.

Hosting capacity of distribution networks for controlled and uncontrolled residential EV charging with static and dynamic thermal ratings of network components

AbstractThe ongoing electrification of road transportation sector, which is expected to continue to strongly increase over the next years, will result in the connection of a significant number of electric vehicle (EV) chargers in LV and MV distribution networks, particularly in residential applications with on‐board (“slow”) EV chargers. In order to evaluate loading limits of existing distribution networks for the maximum number of EV chargers that can be safely connected (commonly denoted as a network EV “hosting capacity”, HC), this paper introduces a general approach to determine one commonly used network design parameter (after‐diversity maximum demand, ADMD) and one new parameter (maximum daily energy demand, MDED), which are both obtained from the load profiles of maximum per‐hour demands for uncontrolled residential EV charging. The presented approach uses actual EV charging data from the UK as the inputs in Monte Carlo simulations to generate daily EV charging profiles for arbitrary numbers of EVs, enabling to identify related ADMD, MDED and per‐hour maximum demand values, as well as their seasonal variations. The assessed ADMD, MDED and hourly maximum EV charging demands for uncontrolled EV charging are then combined with available UK residential daily load profiles before the EVs are connected (“pre‐EV demands”), where their combined coincidental and noncoincidental maximum demands are evaluated against the static thermal rating (STR) and dynamic thermal rating (DTR) loading limits of network components (transformers and overhead lines), taking into account relevant weather/ambient conditions. This is denoted as a network HC for uncontrolled EV charging. Finally, evaluating the resulting per‐hour maximum demand values against the STR and DTR loading limits and MDED values allows to select one particular scheduling method for controlled EV charging, which gives the absolute maximum number of EVs that can be safely connected in the considered network, that is, maximum network HC for fully controlled EV charging. The presented approach is illustrated on the example of the IEEE 33‐bus test network (modelled using typical UK network components), for the pre‐EV residential demands taken from the recordings at a UK MV substation, and for ambient data taken from a UK Met Office weather station. Obtained results allow to evaluate the range of network EV HC values for uncontrolled and controlled EV charging, that is, lower and upper HC limits, which can be correlated with the commonly used allocations of the firm and non‐firm network HC, respectively.