Off-board Charger Research Articles

Bidirectional Electric Vehicle Based on off-board Charger Design

Bidirectional Electric Vehicle Based on off-board Charger Design

Physical Model-Based VDCM Control to Enhance the Inertia of DC Bus for PV-BESS Supported Off-Board Charging Station

Physical Model-Based VDCM Control to Enhance the Inertia of DC Bus for PV-BESS Supported Off-Board Charging Station

Advancing V2G Technology: Design of an Adaptive Bi-directional Three Phase AFE Converter for High-Power Applications

The grid-connected active front end (AFE) converter is an essential component of the Vehicle-to-Grid (V2G) system. In the current scenario, only a battery charger with unidirectional power capability for various power levels is being developed, which improves the grid’s power quality in compliance with the standard. A bi-directional battery charger with a high-power rating for V2G applications is a challenging task that is the focus of the current research. This paper presents a three-phase bi-directional grid-connected AFE converter for a 15 kW charging system. The novelty of this paper is to design and implement an adaptive synchronous reference frame (SRF) model-based controller for bi-directional power flow between the electric vehicle (EV) and grid. It uses an adaptive constant current/constant voltage (CC/CV) mode while integrating a bi-directional DC/DC converter to the proposed AFE system. The significant advantages of the proposed AFE system are high power quality at the grid side, along with suitable total harmonics distortion (THD) and ripple-free DC output voltage. Moreover, the bi-directional offboard charger responds to inductive and capacitive reactive power requests in less than three grid cycles, demonstrating a rapid reaction to grid commands. This paper achieves a fast transient response with a less peak overshoot to improve the steady-state performance. The performance of AFE is further analyzed using simulations, and it has finally been verified using a 15 kVA AFE converter on the laboratory set-up.

Finite Set-Model Predictive Control for Modified quasi Switched Z Source Level 3 Off-board Charger for Active Power Oscillations Damping in Weak Grids

Finite Set-Model Predictive Control for Modified quasi Switched Z Source Level 3 Off-board Charger for Active Power Oscillations Damping in Weak Grids

A Comprehensive Investigation into Bidirectional DC-DC Converters with Soft Switching for Electric Vehicles

Electric vehicles (EVs) are one of the the promising solutions for the environmental issues such as carbon emission and global warming. The high voltage traction battery in EVs is charged from utility grid by an EV charger. The Society of Automotive Engineers (SAE) standardize EV charges into two categories on-board chargers and off-board chargers. Usually, the on-board chargers are located inside the vehicle whereas, off-board chargers are not mounted on the vehicle. For onboard chargers, size and power density of charger become a prior matter of concern. The only way to reduce the size of a converter and thereby increase the power density is to operate power electronic conversion system (PECS) at very high switching frequency (HSF) resulting in reduced size of magnetic component in the charger configuration. However, HSF operation may lead to a high electromagnetic interference (EMI), loss in switch and switch duty. The work in this paper is focused on the development of high frequency bi-directional DC-DC converter (BD2C) stage priory used in on-board chargers due to distributed sources of energy as well as to manage the power distribution in the configuration. The power electronic BDCs are derived from boost and buck unit. The boost derived converter are current fed converters and offers advantages in terms of inherent voltage gain, short circuit protection and lower input current ripple. The voltage spikes across switches, high rated device selection, hard switching, snubber and auxiliary circuit requirements are some of the undesirable factors. This occurrence happened due to unbalance power transfer by the power electronics converter. Similarly, voltage fed converter offers good voltage control during power transfer.

Operating modes of grid integrated PV-solar based electric vehicle charging system- a comprehensive review

The impact of air pollution on the world has been highlighted by the World Health Organization (WHO), which has contributed to the growth of emission-free and ecologically friendly transportation options such as electric vehicles (EVs). Between 2019 and 2020, EV sales climbed by 43%, and by 2025, 14 million EVs are expected to be sold worldwide. On the other hand, EVs have drawbacks such as expensive batteries, short lifespans, lack of EV dependability, limited driving range, and long charging periods. Integrating renewable energy sources (RESs) such as biomass, solar, and wind power into EV charging infrastructures is gaining popularity. PV solar-powered EV charging has benefits like cheaper fuel costs, easier installation, less demand on the grid for power, and cost savings. Hybrid and on-board charging systems offer benefits such as reduced weight, faster charging, and improved communication protocols. On-board chargers have higher energy transfer but are more expensive and difficult to integrate with charging stations. Off-board charging systems include public, rapid, induction, and home charging stations. Advanced charging management systems can optimize charging to preserve battery life. It is recommended that future research concentrate on the development of sophisticated control algorithms, integration of wireless charging, extension of fast-charging infrastructure, innovation in materials, compatibility with many vehicles, and optimization of grid interface to enhance efficiency and user experience. The charging of electric vehicles in standalone and grid-connected photovoltaic systems is covered in this paper, along with an explanation of the various modes of operation for these systems. There is also a quick explanation of the various kinds of EV chargers, their power capacities, and their specifications. The research and comparisons in this paper are expected to be useful resources for scholars who are interested in learning more about EV charging facilities.

Quasi-Resonant Converter for Electric Vehicle Charging Applications: Analysis, Design, and Markov Model Use for Reliability Estimation

This article presents a quasi-resonant converter (QRC) with multiple sources. A QRC has many benefits, such as high gain, constant current, and nominal voltage stress on MOSFET, with an up to 49% duty cycle with fewer switches. These features of the converter make it suitable for electrical vehicle (EV) off-board charging, which requires significant voltage gain. As the switch operates under soft switching condition, the converter has reduced power loss, improved efficiency, and increased reliability. To reduce grid dependency, the suggested QRC is housed with a grid and PV at the input ports. The proposed converter is modeled using mathematical equations and examined using the MATLAB platform under different operating conditions. In this work, analysis of the steady state, along with components design, estimation of the voltage and current stresses, are addressed. Further, the reliability of the QRC based on the probability of components failure is carried out using the Markov model. The hardware results are observed to validate the design, operation, efficiency, and suitability of the proposed QRC for EV off-board charging applications. A 400-watt test rig is designed to assess the performance of QRC.

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

A Comprehensive Analysis of Power Converter Topologies and Control Methods for Extremely Fast Charging of Electric Vehicles

Power electronic converters must be researched and developed to offer high-power, low-cost, and reliable contributions to solving the electric vehicle battery problem in light of the widespread usage and expected rise of EVs. An adequate charging infrastructure is required to accommodate the growing number of electric cars (EVs). Off-board chargers for electric vehicles (EVs) are talked about here, along with their alternating current (AC) and direct current (DC) power stages. Concerns that may arise during the design process of an XFC station are addressed, as are the common topologies for power electronics converters that are efficient for XFC. Electric cars can be charged inside or outside the car, but for fast charging, the shorter, lighter outlets outside the car are the best choice. Focusing on technical specifics, ongoing research, and difficulties, we analyze the most up-to-date topologies and control strategies for AC-DC and dc-DC power stages in off-board chargers. And most of the newest multi-port charging stations that combine photovoltaics (PV), energy storage, electric vehicles (EVs), and the power grid are shown as well. By contrasting the AC-DC rectifier, dc-dc converter, and multiport converter in respect of their architecture, voltage and power ranges, efficiency, and the ways in which they impact workability, future research on EV charging solutions may be guided.

A Comprehensive Examination of the Protocols, Technologies, and Safety Requirements for Electric Vehicle Charging Infrastructure

Electric vehicles (EVs) have various advantages over traditional internal combustion engines (ICEs), including reduced carbon emissions, greater energy efficiency, and a lessened reliance on petroleum supplies. The use of EV charging infrastructure and power levels are reviewed in this article. Battery performance is affected by the design of the battery as well as the charger parameters and infrastructure. In this paper, the off-board and on-board charging methods with bidirectional and unidirectional power flow are compared. Hardware restrictions and connectivity concerns are eased with a unidirectional charger. The bidirectional charger enables both battery energy injection back into the grid and the vehicle. Power is constrained by the onboard charger due to its size, weight, and price. Both conductive and inductive onboard chargers are viable. For high current rates, which are not supported by EVs, it is feasible to develop an off-board charger. The time required for charging, amount of power, cost, equipment, location, infrastructure configurations, and other parameters are provided, compared, and reviewed for different power level chargers, such as level-1 (slow), level-2 (semi-fast), and level-3 (fast).

Electric vehicles charging station configuration with closed loop control

<p><span lang="EN-US">Recently, the demand for electric vehicles (EV) has been on the rise in global markets due to the orientation of national policies to reduce emissions and global warming through the electrification of the transportation sector and the use of clean energy sources. Electric vehicles function on batteries, which must be recharged, either by slow charging at home or by fast charging with a direct current. In the fast-charging process, the batteries can be charged in less than 15 minutes. In this paper, an off-board charger with a three-phase, six-pulse voltage rectifier was designed using the MATLAB/Simulink program. The closed control circuit was simulated, where the simulation results were influenced by changes to the input voltage. When the input voltage was increased or decreased by 5%, this control maintained the value of the current and voltage at the output to be equal to the reference values required to achieve fast charging. The simulation results showed that in the first case where no filter was used, the output voltage and current had a high amount of ripple that exceeded the permissible value. Therefore, a low-pass filter was designed to reduce the ripple factor to a value that was within the permissible limit.</span></p>

A comparative techno-economic assessment of bidirectional heavy duty and light duty plug-in electric vehicles operation: A case study

The proliferation of electric vehicles (EVs) all around the world offers both challenges and opportunities to build a sustainable city and transportation system. Bidirectional charging capabilities at workplace charging facilities (e.g., as part of a microgrid) have made the overall economic optimization more attractive on one hand, but also more complex on the other hand. This paper investigates the cost optimization problem for bidirectional charging at a workplace microgrid connected to two different buildings to determine the optimal framework for a combination of both heavy-duty and light-duty electric vehicles (HDEV and LDEV). A deep learning-based model has been developed to forecast the 15-minute solar generation and building power consumption. Real-time travel profile data has been used to represent the temporal uncertainty of electric vehicle charging. The cost optimization problem is formulated as a Mixed Integer Programming (MIP) model which also addresses battery life degradation. Furthermore, a comprehensive economic analysis has been carried out to analyze the payback period, peak reduction, and cost savings for two different buildings at the same workplace with both on-board and off-board charger configurations. It has been found that HDEV is a better cost-effective solution in comparison to LDEV in terms of energy cost reduction and payback periods. Net metering capability leads to higher energy savings and peak reductions in most cases.

A Unified Control of Grid-Interactive Off-Board EV Battery Charger With Improved Power Quality

This article presents a self-tuning filter (STF) and sliding mode control (SMC)-based control algorithm for a grid-interactive off-board electric vehicle (EV) battery charger to power the EV batteries and simultaneously improve the grid power quality. In grid-connected operation (GCO), the charger uses the STF-based control strategy to estimate the fundamental load current and synchronize voltage templates to generate a pure sinusoidal reference current. Compared to the phase-locked loop (PLL) and the second-order generalized integrator (SOGI), the STF-based technique precisely estimates the synchronizing voltage templates during nonideal grid voltage conditions. Therefore, in GCO, the charger reference current ensures the unit power factor in the grid-to-vehicle/vehicle-to-grid (G2V/V2G) operation mode and the harmonic free grid current in the charger-for-grid (C4G) operation mode. Furthermore, the charger operates in the vehicle-to-load (V2L) operation mode during grid outages to maintain an uninterrupted supply to the residential load. The control algorithm also includes a grid synchronization technique to achieve a smooth transition between GCO and V2L. Furthermore, an SMC-based dc-link voltage controller (SMC-DLVC) is proposed to reduce dc-link voltage overshoot with finite-time convergence during external disturbances in all operation modes. The performance of the proposed control algorithm is validated in a 12.6-kVA off-board charger laboratory prototype under ideal/nonideal grid voltage conditions.

Recent Developments in DC-DC Converter Topologies for Light Electric Vehicle Charging: A Critical Review

Rising greenhouse gas emissions stemming from fossil fuel-driven vehicles are causing damage to the environment. To counteract this, one solution is the adoption of electric vehicles (EV) for transportation requirements. In this regard, one category of EVs that requires special attention is light electric vehicle (LEV), mainly because of their wide potential in public transportation—especially in developing countries. To realise widespread adoption of LEVs for this purpose, it is imperative to make their charging systems more robust. Consequently, the subject of LEV charging has gained considerable traction, and numerous research works have been reported on this subject in recent years. Hence, this paper aims to chronicle recent research developments on LEV charging techniques, by placing special attention on DC-DC converter topologies used in both on-board and off-board chargers. This review explores recent LEV charger DC-DC converters in literature by segregating them into isolated and non-isolated topologies. Lastly, this work explores challenges and emerging trends in LEV charging, which can potentially be explored by researchers in the future.

Review of Electric Vehicle Charging Technologies, Standards, Architectures, and Converter Configurations

Electric Vehicles (EVs) are projected to be one of the major contributors to energy transition in global transportation due to their rapid expansion. High-level of EVs integration into the electricity grid will introduce many challenges for the power grid planning, operation, stability, standards, and safety. Therefore, the wide-scale adoption of EVs imposes research and development of charging systems and EV supply equipment (EVSE) to achieve expected charging solutions for EV batteries as well as to improve ancillary services. Analysis of the status of EV charging technologies is important to accelerate EV adoption with advanced control strategies to discover a remedial solution for negative impacts and to enhance desired charging efficiency and grid support. This paper presents a comprehensive review of EV charging technologies, international standards, the architecture of EV charging stations, and the power converter configurations of EV charging systems. The charging systems require a dedicated converter topology, a control strategy, compatibility with standards, and grid codes for charging and discharging to ensure optimum operation and enhance grid support. An overview of different charging systems in terms of onboard and off-board chargers, AC-DC and DC-DC converter configuration, and AC and DC-based charging station architectures are evaluated. In addition, recent charging systems which are integrated with renewable energy sources are presented to identify the power train of modern charging stations. Finally, future trends and challenges in EV charging and grid integration issues are summarized as the future direction of the research.

Review on Unidirectional Non-Isolated High Gain DC–DC Converters for EV Sustainable DC Fast Charging Applications

Modern electrical transportation systems require eco-friendly refueling stations worldwide. This has attracted the interest of researchers toward a feasible optimal solution for electric vehicle (EV) charging stations. EV charging can be simply classified as Slow charging (domestic use), Fast charging and Ultrafast charging (commercial use). This study highlights recent advancements in commercial DC charging. The battery voltage varies widely from 36V to 900V according to the EVs. This study focuses on non-isolated unidirectional converters for off-board charging. Various standards and references for fast off-board charging have been proposed. Complete transportation is changed to EVs, which are charged by the grid supply obtained by burning natural fuels, contributing to environmental concerns. Sustainable charging from sustainable energy sources will make future EV completely eco-friendly transportation. The research gap in complete eco-friendly transit is located in interfacing sustainable energy sources and fast DC EV charging. The first step towards clean, eco-friendly transportation is identifying a suitable converter for bridging the research gap in this locality. A simple approach has been made to identify the suitable DC-DC converter for DC fast-charging EVs. This article carefully selected suitable topologies derived from Boost, SEPIC, Cuk, Luo, and Zeta converters for clean EV charging applications. A detailed study on the components count, voltage stress on the controlled and uncontrolled switches, voltage gain obtained, output voltage, power rating of the converters, switching frequency, efficiency obtained, and issues associated with the selected topologies are presented. The outcome of this study is presented as the research challenges or expectations of future converter topologies for charging.

Reliability Assessment of SiC-Based Depot Charging Infrastructure with Smart and Bidirectional (V2X) Charging Strategies for Electric Buses

Nowadays, the implementation of smart charging concepts and management strategies with vehicle-to-everything (V2X) functionalities, is required to address the increasing number of battery electric buses (BEBs) in cities. However, the introduction of these new functionalities to the charging systems might affect the lifetime of the charging infrastructure. This has not been investigated yet, although it is an important aspect for the BEB operators. Therefore, this paper performs a detailed reliability assessment to study the impact of smart and bidirectional (V2X) charging on the lifetime of SiC-based high-power off-board charging infrastructure used for BEBs in a depot for overnight charging. In this paper, four different charging current profiles, generated by a smart charging algorithm, are considered. In addition, an electro-thermal model of the charging system is developed to accurately estimate the junction temperature of the switching devices when subjected to the applied charging current profiles. The thermal stress is converted into a number of cycles to failures and accumulated damage by means of a rainflow cycle counting algorithm, a lifetime model and Miner’s damage rule. Finally, a Monte Carlo analysis and a Weibull probability function fit are applied to obtain the system reliability. The results have demonstrated that smart charging strategies can improve the lifetime of the charging system by at least a factor of three compared to conventional uncoordinated charging. Moreover, an uncoordinated charging strategy fails to fulfill the lifetime requirements in the parts per million range, while bidirectional charging could even further enhance the lifetime with a factor of one and a half.

Integration of EV in the Grid Management: The Grid Behavior in Case of Simultaneous EV Charging-Discharging with the PV Solar Energy Injection

The actual research in terms of energy focuses drastically on the use of green energy resources. Hydropower systems have been the most known green sources for years. However, the hydropower systems, which are seasonal and most exploited, do not cover the speed of increasing daily demand. The injection of solar power could be a supporting alternative, but it is only in daylight, weather dependent and intermittent. Therefore, a storage system is required. The batteries are the quick recourse. Not only the energy sector, but also the transport systems are not left behind; they are striving to turn green. Therefore, they are turning to electric vehicles (EVs) and electric moto-bicycles (EMBs). On the other hand, this option tends to be a sharply increasing demand that can be a burden to the grid, i.e., the increase in the EVs and EMBs implies increases in power demand, grid components and pressure on the grid. Fortunately, the EVs use batteries to store energy for their use. Therefore, the EVs are the power storage system, they become part of the power management system and they can save the power surplus. With the injection of PV solar power, there is no need for an extra storage system, as the EVs are charged from the grid and store the solar energy that can be used later after sunset. The bi-directional off-board charger is a solution as it allows the grid to charge the vehicle (G2V) and the vehicle to send power back to grid (V2G). The inclusion of EVs in power management introduces the concept of vehicle-to-vehicle (V2V) when one EV can charge another, and the vehicle-to-load (V2X) where the EV can supply power to EMBs or any load. The V2G, G2V, V2X, the inclusion on solar energy to the grid and the behavior of the grid in that scenario will be illustrated in this paper.

A review on unidirectional converters for on-board chargers in electric vehicle

Transport is a vital sector for achieving sustainable development. The evolution of the electric vehicle is subject to the charging time, accessibility, and facility. On-board chargers are broadly used in the battery-electric and plug-in-electric fleets due to their easy installation and low cost. Also, it must be powerful and extremely efficient because of the constrained interior area and quick charging times. The minimization of hardware requirements and ease of interconnection problems are benefits of unidirectional charging. This review article presents an overview of charging levels, standards of chargers, and various topologies. On-board chargers pose a higher-power rating that reduces the anxiety of charging time and improves the charging facility on level-1 and level-2 grid supply. Unidirectional chargers reduce the charger size while other two-stage chargers pose a higher charging rate with various topologies. Finally, emerging charging trends in off-board charging, inductive charging, technology about vehicle-to-grid, wide-bandgap devices, and application of renewable energy uses are addressed.

Power Quality Improvement for Vehicle-to-Grid and Grid-to-Vehicle Technology in a Microgrid

The demand for electric vehicles continues to grow, as evidenced by global sales of electric vehicles reaching 2.2 million in 2019 and more than doubling to 6.6 million in 2021. The rapid growth of renewable energies and electric vehicles (EVs) necessitates the use of microgrids, which are a promising solution to the problem of integrating large-scale renewables and EVs into the electric power system. Besides, the essential policy support provided by the government is an increase in the availability of public charging infrastructure for EVs. This research employs a fast-charging configuration of an off-board charger with DC energy transfer. Implementation of DC energy transfer for vehicle-to-grid and grid-to-vehicle technology in a microgrid due to DC charging’s unrestricted charger-rated power and rapid power transfer. However, the integration of EVs in the Microgrid system creates some operational challenges, which in this research are power quality issues such as harmonics in power systems that affect both utilities and consumers. The design models using the PI controller and the fuzzy controller based on MATLAB software are simulated to determine the control system’s effectiveness. These simulations assess the control system’s performance, and both approaches help improve the system’s performance power quality by minimizing the system’s total harmonic distortion (THD). According to the results, the fuzzy logic controller exceeded the traditional PI controller as demonstrated by minimizing the THD and also in terms of improving the waveform quality which achieved high accuracy with good performance. This research also utilized the fuzzy logic controller to control the power transfer between EVs and the microgrid, which differs from other research work, to achieve high system efficiency for the benefit of consumers.