DC Charging Research Articles

AI and Machine Learning in V2G technology: A review of bi-directional converters, charging systems, and control strategies for smart grid integration

Electric Vehicles (EVs) are transforming the transportation sector, and their integration with the grid is crucial for a sustainable energy future. EVs can serve as distributed energy resources, aiding in peak shaving, frequency management, and voltage support, thus enhancing grid stability. This comprehensive review explores the transformative potential of EVs in the power grid, focusing on Vehicle-to-Grid (V2 G) technology. We discuss different bidirectional Converter types, including AC-DC and DC-DC converters, to optimize power flow and voltage regulation. AC-DC converters rectify AC grid power for DC charging, while DC-DC converters optimize DC power flow and voltage regulation. Charging station safety is paramount, with electrical shock protection, fire protection, and cybersecurity measures essential for ensuring safe and reliable charging. The review also delves into energy trading and security in blockchain management, highlighting the use of blockchain technology to address hacking vulnerabilities. We explore the potential of Artificial Intelligence (AI) and Machine Learning (ML) algorithms to optimize V2 G performance. By leveraging AI and ML, we can improve the efficiency, reliability, and scalability of V2 G systems. AI-powered predictive analytics can forecast energy demand and supply, enabling proactive charging and discharging strategies. ML algorithms can optimize charging rates, battery health, and grid stability while also detecting anomalies and preventing potential faults. By integrating AI and ML into V2 G systems, we can unlock new possibilities for sustainable energy management, grid resilience, and electric vehicle adoption.

Solar PV powered DC charger for electric vehicles with reconfigurable power electronic interface

ABSTRACT Global expansion of the EV market has led to widespread DC charging infrastructure. Consumers prefer DC charging over AC to reduce charging time per kilometer. However, grid-connected DC chargers can cause issues such as grid instability, power quality problems, demand imbalance, and conversion losses. This paper proposes an off-grid photovoltaic (PV) fed DC charger for EVs along with a battery energy storage system (BESS) to mitigate these challenges. The work aims to increase the use of clean energy for EV charging, to ensure uninterrupted EV charging with minimum power conversion stages, and to improve PV utilization. BESS serves as a backup power source that charges or discharges based on PV availability. Additionally, the system powers the non-critical adjustable loads of domestic/industrial sites with the available PV power when both EV and BESS are fully charged. The system can be reconfigured to operate in six distinct modes using two DC-DC converters and five relays. Among six modes, four modes operate in single-stage power conversion. A buck converter is used to extract power from PV. A bidirectional buck-boost converter is used to charge and discharge the BESS. The proposed system is validated through hardware prototype for both steady-state and transient conditions.

A Multi-Functional Integrated Onboard Charger for Dual-Motor Driving EVs

In this paper, to achieve versatile, cost-effective charging for dual-motor EVs, a multi-functional integrated onboard charger is constructed using a dual-motor driving system. In the driving mode, a five-phase flux-switching permanent-magnet (FSPM) motor powers the front, while a three-phase FSPM motor drives the rear. While in the charging mode, different topologies are adopted for different application scenarios, such as the single-phase AC charging mode, the three-phase AC charging mode, and the DC charging mode. The five-phase FSPM motor and its inverters serve as a boost-based AC/DC converter in both single-phase and three-phase AC charging modes, transforming grid power to DC. In the DC charging mode, they are reconfigured to function as a buck converter. During the three-phase AC charging mode, the three-phase FSPM motor and its inverters take on the role of a rear-stage buck converter. They function to regulate the rectified DC voltage, ensuring it meets battery charging needs. The performance of the integrated charger is validated through simulation and experiment results.

Research on Status Assessment and Operation and Maintenance of Electric Vehicle DC Charging Stations Based on XGboost

With the rapid development of electric vehicles, the infrastructure for charging stations is also expanding quickly, and the failure rate of charging piles is increasing. To address the effective operation and maintenance of charging stations, a method based on the XGBoost algorithm for electric vehicle DC charging stations is proposed. An operation and maintenance system is constructed based on state analysis, considering the operational status of the charging stations and users’ charging habits. Factors such as driving and charging habits, road traffic, and charging station equipment are taken into account. The training sample data are established using historical data, online monitoring data, and external environmental data, and the charging station status evaluation model is trained using the XGBoost algorithm. Based on the condition assessment results, a risk assessment model is established in combination with fault parameters. Risk tracking of the charging stations is conducted using the energy not charged (ENC), evaluating the risk level of each station and determining the operation and maintenance order. The optimal operation and maintenance model for DC charging stations, aimed at achieving both economic and reliability goals, is constructed to determine the operation and maintenance schedule for each station. The results of the case study demonstrate that the state evaluation and operation and maintenance strategy can significantly improve the reliability of the system and the overall benefits of operation and maintenance while meeting the required standards.

An Optimal DC Microgrid for Hybrid Consumer Loads and Electric Vehicle Integration

Increasing use of electrical energy at domestic consumer level due to increased usage of electrical appliances, compounded with increased electric vehicle usage will cause severe stress on existing distribution networks necessitating expensive infrastructural changes. An alternative would be to increase consumer level energy production through renewable sources so that dependence on the grid is eliminated altogether, or minimized. This would also help reduce overall carbon footprint. This paper discusses a viable implementation of a DC micro-grid with battery storage that is compatible with the majority of existing loads and also suggests modifications in certain loads to make them compatible. The micro-grid also allows for DC charging of electric vehicles at different voltage levels. The compatibility with the proposed Microgrid, of loads that can function without modifications and those that require minor changes is analyzed and verified experimentally.

Two-Stage Multiple-Vector Model Predictive Control for Multiple-Phase Electric-Drive-Reconstructed Power Management for Solar-Powered Vehicles

Electric-drive-reconstructed onboard chargers (EDROCs), also known as electric-drive-reconstructed power management systems, are a promising alternative to conventional onboard chargers due to their characteristics of low cost and high power density. The model predictive control offers a fast dynamic response, simple implementation, and the ability to control multiple targets simultaneously. In this paper, a two-stage multi-vector model predictive current control (MPCC) of a six-phase EDROC for solar-powered electric vehicles (EVs) is proposed. Firstly, the topology for the EDROC incorporating a six-phase symmetrical permanent magnet synchronous machine (PMSM) is introduced, and the operation principles of the DC charge mode, the drive mode, and, especially, the in-motion charge mode are analyzed in detail. After that, a two-stage multi-vector MPCC method is proposed by using the multi-vector MPC technique and designing a two-stage MPC structure to eliminate the regulation of the weighting factor of the MPC. Finally, the effectiveness of the proposed method is verified on a self-designed 2 kW EDROC platform.

A Novel Electric Vehicle Thermal Management System Based on Charging Station Heat Pump System During Fast Charging

Abstract A battery thermal management system based on a charging station heat pump system is proposed to improve battery charging efficiency during high-power DC charging. The system provides coolant of appropriate temperature through the charging station heat pump system. It enables the battery to be charged at the optimal temperature for charging, which improves the charging efficiency and reduces the charging time. The two system models are modeled and analyzed using numerical simulation software, and the temperature characteristics and charging time of the proposed system and the original battery thermal management system based on the electric vehicle heat pump system are analyzed under five different temperature conditions. The results show that the proposed system has fast response, high efficiency, and can maintain the maximum temperature below 50°C. Compared with the original system, the proposed system reduces the charging time of the power battery by 10.6%, 17.9%, and 24.6% at 0°C, −10°C, and −20°C operating conditions, respectively. It also saves 1.4% and 6.0% of the charging time at 20°C and 40°C operating conditions, respectively. Comparing the charging time for the power battery at each stage, the proposed system mainly reduces the charging time in the range of 0-20% of the battery state of charge compared to the original system.

Non-Isolated Bidirectional DC-DC Converter Design And Low Power Application for EV Charging Station

Today, the negative impact of charging on the grid is becoming a major concern as the number of electric vehicles increases. The charging topologies such as V2G, V2H and V2V are being studied to solve this problem. The most critical issue in this context is the design and use of appropriate infrastructure and equipment. In this study, firstly a low-cost and high-efficiency non-isolated bidirectional DC-DC converter suitable for DC charging stations is designed. The designed converter was analysed both by analytical methods and by operating at low powers. Secondly, a real-world implementation of V2V and V2H topologies has been performed using these designed converters. In the application study, a DC charging station model was created by using 4 of these converters as charging units. The 90-minute operation of the designed charging station was realised according to a rule-based algorithm. Accordingly, it has been shown that the efficiency of the non-isolated bidirectional DC-DC converter designed is 95%. It is also proved that 54.16% of the EVs load can be shifted to off-peak time period using V2V topology in real world application. According to the results, it is understood that the isolated and high-power version of the designed converter is suitable for charging stations.

Estimation Procedure for the Degradation of a Lithium-Ion Battery Pack

This paper proposes a test procedure for evaluating the degradation of cells in a battery pack. The test can be performed using only the charger’s converters and the battery management system (BMS) without requiring sophisticated instrumentation. The method circumvents the difficulties related to the evaluation of derivative quantities for estimating the state of health (SOH) using integral quantities in the evaluation. The method introduces a 'degradation function' that is calculated with respect to the reference performance of pristine cells. The procedure was applied to the JuiceRoll Race Edition system, an innovative electric vehicle (EV) DC charger with internal storage, made in ENEL X and used during the MotoE championship races. Using this procedure, the degradation of performance in individual groups of cells composing the battery pack was quantified in comparison to the reference group. The procedure helps identify modules that have aged too early or show reliability issues. The method is mature for field operational applications.

Data analysis and estimation of the conversion efficiency of bidirectional EV chargers using home energy management systems data

This study elucidates the authentic utilization of Vehicle-to-Home (V2H) system, a bi-directional DC charger for residential use and appraises power conversion losses incurred during V2H charging and discharging, utilizing data from commercial Home Energy Management Systems (HEMS). This approach offers the advantage of ascertaining operational efficiency within practical scenarios at a reduced cost relative to empirical data acquisition.The empirical examination of results revealed that V2H households exhibited more frequent connections to the charger and engaged in more substantial charging activities compared to Charging-only households.When estimating the power conversion efficiency in the context of V2H charging and discharging, a partial load efficiency curve was constructed for the input power of the V2H charger, thereby confirming that the peak efficiency closely approximated the nominal rated efficiency. These identified characteristics hold value for V2H system simulations. Furthermore, it was confirmed that a substantial standby power, ranging from 92 to 142 kWh per year, was generated when the V2H charger remained inactive in the sampled households. Additionally, the lack of reverse power flow to the external grid from the V2H system led to an observed increase in V2H partial load operation, resulting in a situation characterized by diminished conversion efficiency.

Assessment of the Effectiveness of Energy Transfer for Shore-to-Ship Fast Charging Systems

Charging systems from shore to ship are typically designed based on a range of operational and design parameters, encompassing onboard power and propulsion needs, available charging durations, and the capacity of local power networks. In areas with weak grid infrastructure, onshore energy storage is often employed to facilitate high-power charging for vessels requiring short charging intervals. Nevertheless, incorporating on-shore energy storage adds complexity to the system, and the selection of system configuration can profoundly affect the efficiency of energy transfer from the grid to the vessel. This study presents a comparative analysis of energy efficiency among AC, DC, and Inductive shore-to-ship charging solutions for short-distance ferries utilizing both AC and DC-based propulsion systems. Findings illustrate that an increased reliance on onshore battery power correlates with decreased overall energy efficiency during the charging process. Thus, optimizing energy efficiency necessitates careful consideration when distributing the load between the grid and onshore battery. Results indicate that DC charging offers advantages over other solutions for AC-based propulsion systems in terms of energy efficiency. However, for DC-based propulsion systems, the most efficient solution may be either DC or AC charging, contingent upon the distribution of load between the grid and onshore battery. Furthermore, it is inferred that despite adding additional conversion stages and complexity to the system, the energy efficiency of inductive charging is comparable to wired schemes. Considering the added benefits of contactless charging, such as reliability, safety, and robustness, these findings advocate for the adoption of inductive charging as a promising solution.

Terahertz photon to dc current conversion via magnetic excitations of multiferroics

Direct conversion from terahertz photon to charge current is a key phenomenon for terahertz photonics. Quantum geometrical description of optical processes in crystalline solids predicts existence of field-unbiased dc photocurrent arising from terahertz-light generation of magnetic excitations in multiferroics, potentially leading to fast and energy-efficient terahertz devices. Here, we demonstrate the dc charge current generation from terahertz magnetic excitations in multiferroic perovskite manganites with spin-driven ferroelectricity, while keeping an insulating state with no free carrier. It is also revealed that electromagnon, which ranges sub-terahertz to 2 THz, as well as antiferromagnetic resonance shows the giant conversion efficiency. Polar asymmetry induced by the cycloidal spin order gives rise to this terahertz-photon-induced dc photocurrent, and no external magnetic and electric bias field are required for this conversion process. The observed phenomena are beyond the conventional photovoltaics in semi-classical regime and demonstrate the essential role of quantum geometrical aspect in low-energy optical processes. Our finding establishes a paradigm of terahertz photovoltaic phenomena, paving a way for terahertz photonic devices and energy harvesting.

Feasibility Study of Solar-Powered Electric Vehicle Charging Infrastructure at Selected Petrol Stations in Malaysia

The transition from the conventional internal combustion engine (ICE) to electric vehicles (EV) are expected to result in higher total electricity demand in the country. With the introduction of more EVs into the market, the need for charging stations will grow, subsequently increasing power consumption. This research study aims to assess the potential of solar energy production at petrol stations in central region of Peninsular Malaysia and assess the feasibility of solar-powered petrol stations in meeting the energy demands of electric vehicles. 10 samples of existing petrol stations are selected to install a solar-powered DC charging station as a case study. To study their energy consumption, 90kW DC charger was evaluated. The design of the PV systems for the petrol stations was done by using the PVsyst simulation software. As a result, it is found that 90% of the designed PV systems are able to generate enough energy to meet the estimated annual energy consumption of the 90kW DC charging system. The results also showed that the cost to install the solar-powered charging system for both power ratings can be recouped in less than 2 years. Overall, this research study offers valuable insights for addressing the rising energy consumption resulting from the increased penetration of electric vehicles in the future. Additionally, the implementation of solar-powered charging infrastructure aligns with the country’s renewable energy objectives and efforts to reduce greenhouse gas emissions. However, the assessment of EV penetration and the adoption of charging infrastructure was conducted based on government targets rather than relying on current data regarding the actual numbers and trends of EVs and chargers in Malaysia. The availability of accurate and up-to-date data on the number of EVs, their battery characteristics, chargers, and user charging behaviors in Malaysia would contribute to further enhancing this research work.

Design and Construction of a 3-Phase Axial Type BLDC Generator for PLTB

The need for electrical energy in remote areas to improve community welfare must be a concern for universities. The government's ability to build new electricity sources is very minimal because it requires large infrastructure and costs, but the government continues to strive to develop new power plants. Therefore, it is necessary to strive for innovation to build power plants from renewable energy sources. There is a need to use renewable energy as an alternative to replace electrical energy which is increasingly in crisis. One alternative energy that is easy to make is energy that uses magnetic force as a model for generating electricity. Brushless Direct Current (BLDC) motors are an alternative to current DC motors. This three-phase permanent magnet axial flux generator is specially designed for vertical-type wind turbines. This generator consists of two stators and one rotor. where each stator consists of 9 coils and the magnet used is a neodymium permanent magnet. Based on test results, this generator can produce a voltage of 12.57 VDC with a wind speed of 6.84 m/s. So, it can turn on DC lights and charge DC batteries. This three-phase axial BLDC generator was tested in 3 stages, namely without load, using battery load, and DC-light load with wind conditions depending on natural conditions.

Bill It Right: Evaluating Public Charging Station Usage Behavior under the Presence of Different Pricing Policies

This study investigates for the first time how public charging infrastructure usage differs under the presence of diverse pricing models. About 3 million charging events from different European countries were classified according to five different pricing models (cost-free, flat-rate, time-based, energy-based, and mixed) and evaluated using various performance indicators such as connection duration; transferred energy volumes; average power; achievable revenue; and the share of charging and idle time for AC, DC, and HPC charging infrastructure. The study results show that the performance indicators differed for the classified pricing models. In addition to the quantitative comparison of the performance indicators, a Kruskal–Wallis one-way analysis of variance and a pairwise comparison using the Mann–Whitney-U test were used to show that the data distributions of the defined pricing models were statistically significantly different. The results are discussed from various perspectives on the efficient design of public charging infrastructure. The results show that time-based pricing models can improve the availability of public charging infrastructure, as the connection duration per charging event can be roughly halved compared to other pricing models. Flat-rate pricing models and AC charging infrastructure can support the temporal shift of charging events, such as shifting demand peaks, as charging events usually have several hours of idle time per charging process. By quantifying various performance indicators for different charging technologies and pricing models, the study is relevant for stakeholders involved in the development and operation of public charging infrastructure.

Hybrid Charging Station

Abstract: In an attempt to decarbonize the transportation sector, among many countries, is option for e-mobility as an optimal solution, to create a greener, cleaner, and more affordable future for everyone. However, it is missing a crucial prerequisite, which is a strong EV charging infrastructure. The various EVCS types, technologies, techniques, and equipment. It also includes the design of a charging station for small EVs for on campus use, with a solar energy system input. Next, a mechanical 3D design for the final product. As well as a proof-of- concept implementation. Lastly, some conclusions, limitations, and recommendations for further research. A solar charging station is meant so that vehicles is fully charged and is environmentally safe. this technique transforms solar power to electricity and stores it in an battery bank. If electric vehicles must be truly imperishable, it's essential to charge them from sustainable sources of electricity, like solar or wind energy. In this paper, the solar charging station that gives the electricity to charge the battery. The charging station has integrated battery storage that allows for off-grid operation. The DC charging uses the DC power from the photovoltaic panels directly for charging the vehicles battery without the utilization of an AC charging adapter.

Power consumption prediction for electric vehicle charging stations and forecasting income

Electric vehicles (EVs) are the future of the automobile industry, as they produce zero emissions and address environmental and health concerns caused by traditional fuel-poared vehicles. As more people shift towards EVs, the demand for power consumption forecasting is increasing to manage the charging stations effectively. Predicting power consumption can help optimize operations, prevent grid overloading, and power outages, and assist companies in estimating the number of charging stations required to meet demand. The paper uses three time series models to predict the electricity demand for charging stations, and the SARIMA (Seasonal Auto Regressive Integrated Moving Average) model outperforms the ARMA (Auto Regressive Moving Average) and ARIMA (Auto Regressive Integrated Moving Average) models, with the least RMSE (Root Mean Squared Error), MAE (Mean Absolute Error) and MAPE (Mean Absolute Percentage Error) scores in forecasting power demand and revenue. The data used for validation consists of charging activities over a four-year period from public charging outlets in Colorado, six months of charging data from ChargeMOD's public charging terminals in Kerala, India. Power usage is also forecasted based on wheels of vehicles, and finally, a plan subscription data from the same source is utilized to anticipate income, that helps companies develop pricing strategies to maximize profits while remaining competitive. Utility firms and charging networks may use accurate power consumption forecasts for a variety of purposes, such as power scheduling and determining the expected energy requirements for charging stations. Ultimately, precise power consumption forecasting can assist in the effective planning and design of EV charging infrastructure. The main aim of this study is to create a good time series model which can estimate the electric vehicle charging stations usage of power and verify if the firm has a good income along with some accuracy measures. The results show that SARIMA model plays a vital role in providing us with accurate information. According to the data and study here, four wheelers use more power than two and three wheelers. Also, DC charging facility uses more electricity than AC charging stations. These results can be used to determine the cost to operate the EVs and its subscriptions.

Research on Adaptive Droop Control Strategy for a Solar-Storage DC Microgrid

When the solar-storage DC microgrid operates in islanded mode, the battery needs to stabilize the bus voltage and keep the state of charge (SOC) balanced in order to extend the service life of the battery and the islanded operation time. When there are multiple energy storage units in the DC microgrid, it is necessary to solve the problem of unbalanced circulation and the state of charge between batteries using a reasonable droop control method. In this paper, firstly, the DC–DC charging and discharging circuit of the battery is designed, and the unbalanced SOC of the battery caused by the different impedances of the line is analyzed. Secondly, an adaptive droop control method is proposed to solve the problems of SOC imbalance and current circulation between the batteries. Thirdly, based on MATLAB/SIMULINK R2021b simulation software, the proposed control method is modeled and simulated. Compared with the traditional droop control, the effectiveness of the proposed method is validated.

Electric Vehicle Charging from Tramway Infrastructure: A New Concept and the Turin Case Study

The electrification of transport is expected to progressively replace significant shares of light duty mobility, especially in large cities. The European Alternative Fuel Infrastructure Regulation (AFIR) aims to drive the adoption of electric mobility by establishing specific targets for charging point deployment. Innovative charging concepts may complement and accelerate the uptake of this fundamental part of the urban mobility transition. In this paper, one such innovative concept is described and its potential impact is assessed. The core idea involves integrating charging points into existing city tramway infrastructures. Turin’s tramway network is taken as a representative case study. The proposed technical solution encompasses a charging hub powered by four isolated DC/DC converters of 50 kW, directly connected to the DC tramway distribution line. Three of these constitute the heart of a 150 kW charger, while the fourth acts as voltage regulator. This native DC installation greatly simplifies the architecture of the DC chargers. Using a conservative approach, it was estimated that a single recharging station could charge more than 60 vehicles daily. This highly scalable and replicable solution, with the potential for over 100 conversion substations across Italy, would enable the installation of numerous high-power chargers in urban settings. Furthermore, additional benefits could be realized through enhanced recovery of kinetic energy from trams, which is currently dissipated on-board.

A real-time energy flow management of a grid-connected renewable energy sources-based EV charging station

ABSTRACT As the sales of electric vehicles (EVs) increase in India, there will be an increase in the number of charging stations in the future. Meanwhile, the demand for extra power from the grid and intermittent power from renewable energy presents significant challenges for charging infrastructure. This paper presents a real-time energy flow management strategy (EFMS) designed for an EV charging station (EVCS) that utilises power from renewable energy sources (RES), an energy storage battery unit (ESBU), and the grid. The primary objective is to increase the utilisation of renewable energy and minimise the quantity of electricity bought during the peak period of the grid by implementing direct electric vehicle load control. EVCS has been designed to charge up to 80 EVs using five DC chargers. The EFMS aims to enhance the scheduling of EV charging by considering grid time-of-use (ToU) pricing and efficient usage of ESBU in terms of battery degradation effect and maximising the use of RES. A multi-objective optimisation algorithm has been developed for EV scheduling. The baseline uncoordinated charge method is contrasted with the proposed approach. The EFMS effectiveness is tested in MATLAB, and the subsequent analysis and results are drawn and discussed.