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 efciency


Introduction
With their high price, limited battery capacity, and lack of recharging infrastructure, electric vehicles (EVs) fall short of consumers' expectations to a greater extent. A change in consumer behavior is crucial because consumers will choose only EVs if they are similar to the current vehicles on the road. Tey ought to progressively become more aware of the advantages of using greener and cleaner technology. Despite the fact that many consumers dislike the current electric vehicles, there are plenty of alternatives designed to meet consumer demands. Te marketing of such items is a crucial step towards a greener environment. increased costs, battery life cycles, a lack of charging infrastructure, and charger-related problems. Another signifcant drawback of EV chargers is the generation of harmful harmonics, which afect the characteristics of the distribution system. An active rectifer can lessen this efect on chargers [1,2,4,5].
Level 1 chargers are intended for use in household environments. Level 2 chargers need a 240 V outlet and are intended for both home and public charging. For levels 1 and 2, single-phase solutions are often used. Tree-phase solutions are utilized for Level 3 chargers, which are intended for public and commercial use. Level 2 and 3 chargers that are already present in shopping centers, parking lots, movie theatres, restaurants, hotels, etc., are stations for public use and are probably to be utilized [1,2,4,5]. In accordance with several international standards, Table 1 summarizes the various charging power levels. Figure 1 presents the charging infrastructure for electric vehicles.
Of-board and on-board EV battery chargers may be divided into those with bidirectional and unidirectional power fow. Less hardware is needed for unidirectional charging, which also simplifes connectivity problems and slows down the deterioration of batteries. A bidirectional charging system maintains power stabilization with proper power conversion, battery energy injection back into the grid (V2G), and charging from the grid.
In the past decade, electric vehicles (EVs) have seen a huge surge in popularity, with annual sales almost tripling globally thanks to heavy government support. However, their true competitiveness with internal combustion engine (ICE) cars will likely only be achieved by 2035, and although they are still lagging behind conventional cars in various utility features, such as base purchase cost, long charging times, and reduced battery life in cold conditions, the spread of EVs is projected to cause an additional global electricity consumption increase of 11-20% by 2040 [6]. As such, governments and auto manufacturers must double down on energy storage technologies if they wish to continue developing EV transport in an environmentally friendly manner.
By 2040, the number of electric vehicles is expected to increase by a factor of up to 70 compared to 2016, depending on the assumptions of rapid improvement of electric car technology, battery costs, and government incentives. Tis would give EVs an 11-28% share of the global road transport feet, signifcantly higher than 2016 fgures [6]. To further the development of electric transport, researchers must focus on improving vehicle charging. Tis is especially important given the limited range of EVs, as it would make them more accessible for daily use and reduce the need for frequent charging. Research should focus on creating reliable and efcient charging infrastructure as well as technologies that could reduce charging times, either through improved battery technology or by introducing faster charging options. Additionally, research should also be conducted on other forms of EV transportation such as electric vehicles in outer space and in the maritime sector.
Considerable points to improve the EV in the transportation sector are as follows: baseline scenario, which is a business-as-usual scenario with modest rates of technological development for both ICE and electric vehicles and limited EV support; favorable scenario, which assumes more rapid improvement of electric car technology (mainly battery costs and mileage) and more government incentives.
According to the modelling results, by 2040, the number of electric vehicles will increase by a factor of 60-70 compared to 2016 and reach from 12 to 28% of the global feet, depending on the scenario. Te key sensitive parameters are the rate of battery cost reduction and the amount of government subsidies, which determine ownership costs, as has been noted in the previous section.
Because of their weight, limited space, and expensive price, conventional onboard chargers have substantial power limitations. To avoid these types of issues, they can be combined with the electric drive.
Systems for on-board battery charging can be either inductive or conductive. Direct contact is made between the connection and the charge inlet in conductive charging methods. A wireless power transmission occurs using an inductive charger. An inductive charger has been developed for Levels 1, 2. It could be moveable or stationary. With an of-board battery charging system, size and weight restrictions are less of an issue [1,2,[4][5][6][7][8]. Te study by [7] provides an overview of electric vehicle charging infrastructure, including development incentives, charging station designs, power converters, standards, industrial applications, and future directions. In addition, we have selected cutting-edge technologies after extensive research and development; these include both theoretical and practical EV charging solutions.
Tis paper examines the current status of EV battery chargers, the infrastructure for charging, and power output. An overview of battery charging systems is given frst. Ten, according to various international standards, charging power levels and assessments of battery infrastructure for EVs follow. Based on the cost, component ratings, equipment, amount of power required, duration of charging, and location, among other considerations, infrastructure confgurations and several charging power levels are given, evaluated, and compared.

Electric Vehicle Battery Chargers
Te development of electric vehicles is largely dependent on battery chargers. Te duration of charging and battery life can be used to relate battery charger parameters. A battery charger needs to be reliable and efcient, inexpensive, compact and lightweight, and have a high power density [9]. Its operation mostly depends on the charger's parts, how they are controlled, and switching techniques. An EV charger should draw utility current with minimal distortion and maximize the real power availability from a utility outlet to a high power factor to make sure that the power quality will be reduced. Harmonics and DC injection are kept to a minimum according to many standards, such as IEEE 1000-3-2, SAE J2894, and the U.S. National Electric Code  [1,4]. A boost converter for active power factor correction (PFC) is present in modern EV battery chargers [1,4]. Te converter increases electromagnetic interference (EMI) while resolving the issue with heat management in the input diode rectifer bridge seen in the standard boost PFC. To reduce inductor size and battery charging current ripple, an interleaving topology has been proposed [4,5].
Te use of multilevel converters is the best option for EVs charging at power level 3 since they can reduce size, switching frequency, and stress on their components. Tese converters may use less expensive flters, but they also increase complexity, components, and control of the necessary circuitry. Recently, a 1-phase on-board charger has been favored to charge plug-in EV batteries. A 1phase unidirectional multilevel charger is the most widely used design for low power charging levels (1 and 2). Preferably, 3-phase multilevel bidirectional converters can be used to implement Level 3 fast charging systems [1,[6][7][8].
Te main advantages of using these types of converters are: (1) High power factor (2) High power quality (3) Higher boost (4) A decrease in total harmonic distortion (THD) (5) A decrease in EMI noise (6) Regulated dc output voltage is not sensitive to changes in the load or the supply (7) Ripple free [1].

Charger Topologies
Even though EV battery charger systems may employ a number of converter topologies with various capacities, they frequently imagine the battery pack as a single large battery stack [10]. In spite of this, EVs face major obstacles in the form of charging time, charging methods, and range anxiety. Electric car battery charging technologies are crucial to overcoming these obstacles. Numerous charging topologies for EVs have been explored in the literature and put into practice. Review of the current state-of-the-art critique of high-tech converter topologies and charging strategies for EVs. Tis manuscript has covered the criticism of the newly suggested EV charging technologies in terms of charging methods, control strategies, and power levels, in addition to the conventional topologies. Furthermore, the various onboard chargers' power factor correction designs, benefts, and disadvantages [6]. Figure 2 illustrates the beneft of parallel-connected semiconductors in an interleaved boost converter. Additionally, it reduces stress on the output capacitors due to ripple elimination at the output. However, similar to the boost, this design is constrained to power levels of approximately 3.5 kW since it must ofer heat control for the input bridge rectifer.
Te single-phase multilevel unidirectional charger, which is a typical multilevel charger topology, is suitable for low-power charging levels 1 and 2 as shown in Figure 3.
Te three-phase diode-clamped bidirectional charger for charging station applications is shown in Figure 4. Tese converters use smaller energy-storage components like capacitors and inductors and are distinguished by low switch voltage stress.   Figure 5 illustrates the half-bridge topology, which has fewer parts and is less expensive, yet has signifcant component stresses.
Figures 6-8 illustrate how full-bridge systems have more parts, cost more, and have lower component stresses. Multiple PWM inputs are required by this layout, increasing the complexity and expense of the control circuitry. Bidirectional power (V2G and G2V), a power factor of one, the ability to execute power management, a minimal impact on PQ, construction and topology simplicity, and compatibility with standard 16A single-phase plugs are shown in Figure 9. Tis charger does not support fast charging. Figure 9 shows the designed bi-directional converter for a 3-module battery system with an integrated CEC topology. However, the suggested CEC topology might be created for any quantity of battery modules to directly give the appropriate ratings. Two power conversion stages make up the bidirectional converter. A large DC link comes after an AC-DC H-bridge converter in the frst stage. A bidirectional DC-DC buck/boost converter acts as the 2nd stage of power conversion [12].
Te two-stage on-board charger is shown in Figure 10 and consists of a bidirectional DC-DC converter for the second stage, which regulates the battery current, and S2 C Figure 2: Topology for interleaved unidirectional chargers, as in [4,5]. Figure 3: Circuit for a single-phase, unidirectional, multilayer charger, as in [4,5].

Vb
Bidirectional DC/DC Converter S1 S2 S3 S4 S5 S6 C Figure 7: Tree-phase full-bridge bidirectional charger, as in [4,5].   a bidirectional AC-DC PFC converter for the frst stage. A precise DC level must be delivered by the front-end AC-DC converter with less harmonic distortion (THD) and good power factor correction (PFC). Te most common topologies are shown in Figure 11 bidirectional full-bridge AC-DC converters for three-phase and single-phase chargers. With fewer components, the halfbridge converter system is less complicated than the fullbridge converter system, but it has greater component stresses.
In spite of being more difcult to control, the three-level AC-DC converter in Figure 12 is rated for high power levels, has a smaller flter, and has less component stress because of greater PFC.
When the battery is discharged, the converter acts as a boost converter. In this case, the converter transfers energy from the battery to the grid when the battery is being charged, the DC-DC converter acts as a buck converter Figure 13. In this case, the converter transfers energy from the grid to the battery. However, it is only appropriate for level 1 applications due to its large current ripple output. Figure 14 consists of two parallel 180°out-of-phase buckboost converters. Tis topology can produce more power and has less output current ripple. Figure 15 depicts a DC-DC dual active-bridge bidirectional converter. It is made up of a transformer connecting two active bridges. Although this design ofers excellent power density, the many switches make it more difcult to regulate and costlier. Figure 16 Single-stage AC-DC bidirectional integrated onboard chargers have been proposed as a way to limit the weight, size, and price of two-stage onboard chargers. A customized AC-DC bidirectional converter and a DC-DC bidirectional converter are combined during integration. With this integrated design, charging and discharging from the high-voltage bus are both possible. Figure 17 depicts a DC-DC high-frequency isolated converter with IPT. A single-phase pulse width modulation (PWM) converter operates as the 1st stage of the two-stage contactless converter system. Figure 18 illustrates a suggested bidirectional converter based on a matrix converter and an IPT. In this converter topology, single-stage power conversion is carried out. Figure 19 depicts the suggested bi-directional EV charger's circuit design. A single-phase nonregulating halfbridge SRC with an LC flter and a full-bridge inverter with an LCL flter comprise the two power conversion stages of this charger. Figure 20 depicts a conventional two-stage isolated battery charger with a full-bridge LLC converter and a boost PFC converter. Figure 21 depicts the proposed two-stage isolated battery charger with a resonant LLC converter and a SEPIC PFC converter.
Due to its capacity to operate in four quadrants in the PQ plane, the active boost-rectifer topology illustrated in  Figure 23 illustrates how an of-board electric vehicle battery fast charger can be used to reduce power quality issues brought on by the same electrical installation's poor power factor (caused by reactive power). In this mode, the charger's AC-DC stage alone is employed (without using the energy stored in the batteries).

Journal of Advanced Transportation
Te grid-connected EV system's suggested topology, shown in Figure 24, assesses the impact on the power grid with several EV fast chargers. Te AC-DC converters with passive flters at the front end were connected to the various back-end DC-DC converters of the EV charger by a dedicated DC-link capacitor and the EV batteries at the rear end. Figure 15: DC-DC dual active-bridge bidirectional converter, as in [13].
Co S High Voltage Bus Figure 16: AC-DC single-stage bidirectional converter integrated with dc-dc converter, as in [13].

S5 S6
Lpi S7 S8 S9 S10 S11 S12 Cpt S1 S2  Journal of Advanced Transportation 3.1. Charging Infrastructure. Te deployment of electric vehicle supply equipment (EVSE) and charging infrastructure is important due to several difculties that must be addressed: (1) Charging time, With the availability of charging infrastructure, the requirements and cost for onboard batteries will be minimized. Te following are the primary components of an EVSE: (a) Vehicle charging codes, (b) Public or residential charging stations, (c) Vehicle connectors, (d) Power outlets, (e) Various plugs for connection, (f ) Protective gear [1,2,4,5].
A specialized cable set and a wall-mounted or pedestalmounted box are the two common variations. Te precise confgurations difer from one country to another and from one location to another depending on voltage, frequency, transmission standards, and electrical grid connection. According to the Electric Power Research Institute (EPRI), various EV customers will charge their vehicles overnight at home [2,4,5]. Terefore, the use of power levels 1 and 2 equipment will be the frst choice [ Figure 19: Proposed Bi-directional EV charger, as in [15]. of conductive and inductive charging systems is presented followed by an overview of the charging standards and a discussion on the topologies presented in the literature for fast charging stations. Te economic aspects of fast charging infrastructure along with an overview of prospective areas for future research in this feld are also presented [7]. Te advancements in technology that enable longer ranges in electric cars and motorized two-wheelers include developments in charging technology, battery technology, and motorized systems. Charging technology has improved greatly, allowing for faster charging of EVs, an important factor for those who need to drive long distances. Battery technology has also advanced, with car batteries now able to last much longer than they used to and the option of larger batteries available for heavier vehicles. Motorised systems have also been improved, allowing for more powerful yet efcient performance when driving at higher speeds. With all of these factors combined, it is possible for EVs and twowheelers to have much longer ranges and to be more reliable for long-distance travels [20].
Charging technology has also become more advanced, with the introduction of new charging topologies such as DC fast charging and AC Level 3 charging. Tis allows for greater convenience when charging EVs, since they can be charged quickly in a matter of minutes or hours. Furthermore, the infrastructure for charging stations is rapidly expanding, making it easier to fnd suitable locations to charge up an EV. Safety issues are also being addressed with improved standards and protocols, making the charging process safe and secure. All of these advancements in technology have allowed electric cars and motorized twowheelers to have much longer driving ranges than they previously had [21].
Currently, there are a variety of advancements in technology that enable longer ranges in electric cars and motorized two-wheelers. Tis includes improvements in charging technology, battery technology, and motorized systems. Charging technology has improved greatly, allowing for faster charging of EVs, and battery technology has advanced, with car batteries now able to last much longer than they used to and with the option of larger batteries available for heavier vehicles. Motorised systems have also been improved, allowing for more powerful yet efcient performance when driving at higher speeds. In the future, advances in materials such as lithium-ion batteries, hydrogen fuel cells, and regenerative braking will further help to extend electric car and motorized two-wheeler ranges [22].
Te electric truck industry has been growing rapidly due to the increased focus on emissions reduction and sustainability. One of the most important aspects of electric truck technology is a recharge philosophy that supports efcient refueling and charging for trucks. For commercial feets, this often means creating infrastructure that supports multiple charging and refueling points, along with the necessary power sources. Additionally, new technologies S9 S11 S10 S8 L4 L5 L6 S12 AC-DC Converter DC-DC Converter S13 S14 S15 S16 L7 L8 Co C2 C1 Figure 23: Proposed architecture for the three-phase EV fast battery charger, as in [18].  Figure 24: Proposed framework if the grid-connected EV system, as in [19]. and practices are being developed to support more efcient and faster charging and refueling. One example of such technology is battery swapping, which allows drivers to replace empty batteries with fully charged ones instead of waiting for charging. Tis can reduce both charging downtime and total turnaround time, allowing for more efcient operation. Governments and other organizations around the world are also investing heavily in promoting research and development in this area. In addition to charging and refueling technologies, feets should also consider other ways to optimize their charging processes. Tis includes optimizing routes to minimize the need for frequent stops, as well as considering charging options available in locations where the truck will be stopping. For example, some locations may allow for information power charging through renewable energy sources like solar and wind. Overall, the electric truck industry is making great strides in lowering emissions while improving efciency and cost savings. Optimizing charging and refueling infrastructure and considering alternative solutions like battery swapping and renewable sources of power all contribute to greater sustainability and environmental beneft.
Te current logistics and transportation (L&T) systems are a mixture of conventional internal combustion engine vehicles and newer "green" technologies such as plug-in hybrid electric vehicles and electric vehicles (EVs). However, the introduction of EVs raises additional challenges, such as investment decisions regarding the number, location, and capacity of recharging stations. Additionally, due to the limited driving range of EVs, there are extra constraints to consider when designing efcient distribution routes. [25] Tis paper reviews the environmental and strategic/planning/operational issues associated with standard and hydrogen-based EVs and how they generate new variants of the Vehicle Routing Problem. Te paper also examines potential research areas yet to be explored in relation to the Green VRP. A particular focus is given to a VRP with pickup and delivery using a mixed feet of EVs and conventional ICEVs. Table 2 shows the comparisons of various topologies.

Charging Power Levels
With a charging power level of 1, the EV can be charged at the slowest possible rate. A 1-phase grounded outlet (120 V/15 A), such as a NEMA5-15R, is used for Level 1 in the United States [4,26]. Due to the prevalence of 120 Vac outlets, the ability to charge up to 2 kW is essential [26]. Te standard SAE J1772 connector may be utilized as an EV AC port. Sites for homes and businesses do not need any extra infrastructure [4,27]. At night, of-peak rates (minimum) are available. Although it is anticipated that this level would be built into the vehicle, the installation cost of a domestic Level 1 charging system is estimated to be between $500 and $880 [1,2,4,5].

Level 2.
Te most common pricing technique is level 2 charging for specialized private and public services. To reduce the need for redundant power electronics, this charging infrastructure can also be included in the vehicle. Existing Level 2 equipment can charge at up to 80 amps, or 19.2 kW, from 208 or 240 volts [1,2,4,5,26]. Although vehicles like the Tesla have on-board power electronics and simply require an outlet, public or residential units may need the required tools and connection installation.
A common EV battery may be charged overnight using Level 2 equipment in the majority of American homes with 240 V electricity. As a result of the standardised vehicle-tocharger connection and its fast charging, owners are likely to favor Level 2 technology. Te norm is a separate metre for billing.
According to reports, installing a Level 2 charger may cost between $1000 and $3000, with a residential unit costing $2150. Te Tesla Roadster charging system will cost an additional $3000. Te new standard has a two-pin DC connector below and an SAE J1772 AC charge connector on top, allowing AC or DC rapid charging via a single connection [1,2,4,5]. Te SAE J1772 connection is used for both level 1 and level 2 ac or dc charging, as in [4,5]. Figure 25 shows the charging socket.

Level 3.
Te fastest charging time is ofered by level 3, which is used economically and takes less than an hour [4]. In order to charge EVs in less than 30 minutes, FCS needs high power from the grid [28]. It may be deployed at rest areas along highways and at urban refueling stations and is identical to fuel stations. Around 480 V, or a higher 3-phase circuit, is the operating range for level 3 charging. Te requirement for an of-board charger is the availability of regulated AC-DC conversion. For residential areas, charging power level 3 is not advised [1,2,4,5]. With a level 3 charger, an electric car should be able to charge to 50% in 10 to 15 minutes at 60 to 150 kW. Commercial DC fast chargers with a capacity of 250 kW and a voltage range of 50-700 VDC [26].
Direct DC connections to the vehicle are possible. Infrastructure needs and standards for AC, DC ports are being established. Te "CHAdeMO" protocol, developed in Japan, is becoming more widely known. Installation costs might be a problem. According to reports, level 3 charging infrastructure might cost anywhere from $30000 to $160000. Te upkeep of the charging stations is another expensive consideration.
According to the SAE J1772 standard, Level 1 and 2 EVSE must be installed on the vehicle, whereas Level 3 EVSE must be installed outside. General public stations are designed to employ Levels 2 or 3 to ofer fast charging in public areas. Lower charging power levels can help utilities mitigate the efects of on-peak usage. During times of peak demand, high-power fast charging has the tendency to quickly overload local distribution networks [29].
Following are the efects of charging power levels 2 and 3 on distribution networks: (i) System reliability (ii) Voltage fuctuations (iii) Transformer losses/power losses  Due to the shorter transformer life, this might have a substantial infuence on the dependability, security, economics, and efciency of developing smart grids. Using a regulated smart charging method helps reduce the deterioration of standard distribution equipment. Te efective integration of multiple EVs necessitates a dependable communication network as well as public charging management [1,2,4,5]. Figure 26 provides details on the infrastructure requirements and charging characteristics for a few vehicles.
Onboard vehicles typically have level 1 chargers, but level 2 designs that may be installed inside, in garages, or in public places have been shown to work [26].
A coordinated regulated charging strategy can be employed to reduce the efects of higher power charging levels [29]. Proper charging control and communication are required to accommodate more EVs. Figure 27 depicts the deployment of the charging system with various charging levels as well as of-board and on-board confgurations for EVSE. Table 3 shows the power level charging rating.

Off-Board and On-Board Chargers
Due to an internal charger in the vehicle, EV owners may charge their vehicles from any suitable power supply. Typical onboard chargers can only provide Level 1 power due to weight, space, and price restrictions. Recurring power electronics are needed for of-board charging, which adds to the overall cost. Defacement danger and extra messiness in an urban setting are two further drawbacks [4].
Of-board fast-charging stations are quickly catching up, despite the fact that onboard chargers are now the most popular on the market. Even though DC charging stations are more expensive, they do ofer some promising benefts, including lighter electric vehicle (EV) weight, high power charging, faster charging, improved battery management systems (e.g., thermal issues), and proper communication among owners of commercial charging sites and utility companies to improve negotiated opportunities [1,5,14]. Table 4 presents the comparison between on-board and ofboard chargers.

Uni-and Bidirectional Chargers and Comparisons of Power Flows.
Tere are two diferent power fows that can be possible between the power grid and EVs. It can function as a load in case 1 and as a distributed storage device to feed the grid in case 2. Figure 28 presents the uni-and bidirectional power fow.

Unidirectional
Charger. EVs can be charged but cannot inject back into the grid when necessary while utilizing a unidirectional charger. Due to the widespread use of EVs, unidirectional chargers are used, which makes it simple to manage heavily loaded feeders. Te main objective of unidirectional charging research is to identify the best charging strategies that maximize advantages and consider how they could afect the distribution system. Due to the signifcant penetration of EVs and efective control of charging current, unidirectional chargers may accomplish the majority of utility objectives while avoiding the performance, cost, and safety difculties linked with bidirectional chargers.

Bidirectional Charger.
Bidirectional charging allows the possibility of power transfer in both directions between EVs and the grid. EVs have the capacity to both draw power from and provide energy to the grid. Considering that they serve as backup generators at the distribution network level, EVs may be viewed as both a source of generation for utilities and a load.
Bidirectional power fow improves the power network's capacity to react to controlling the energy stored in electric vehicle batteries with the use of V2G technology, maintaining the network's sustainability, efciency, and reliability. Bidirectional V2G technology has several benefts, including support for reactive and active power, maintenance of peak-load mitigation, power factor management, and support for better integrating diferent renewable energy sources [30].
Although most research has concentrated on bidirectional power fow, approval faces signifcant obstacles. Bidirectional power fow is required to handle metering issues, battery degradation brought on by repeated cycling, the greater cost of a charger with bidirectional power fow capabilities, and necessary distribution system improvements.
To ensure that the vehicle's SOC is high when it is time to travel, customers may demand an energy guarantee. Signifcant safety precautions must be taken to properly deploy bidirectional power fow.
Chargers at levels 1, 2, and 3 may be unidirectional. Because level 1 power constraints and cost objectives are low and it is essential to optimize fexibility, bidirectional chargers are only expected for level 2. Reverse power fow contradicts the fundamental goal and concept of level 3 fast charging, which is to supply signifcant energy as quickly as feasible [1,4,5] and minimize connection time.

Conductive Charging.
In the case of conductively connected charging systems, a direct connection will be made between a connector and the charge inlet [35]. Conductive chargers typically consist of an AC-DC power factor correction (PFC) converter followed by a DC-DC converter and have a hard-wired connection between the power electronic interface (PEI) and the power supply for charging [32].
Systems for conductive charging are easier to use and are more efective. Conductive charging can be used for both of-board chargers for fast charging and on-board chargers for slow charging inside electric vehicles (EVs) [2,5]. Te cable can be supplied for a level 1 or level 2 conventional electrical outlet or for a level 2 or level 3 charging station. Tere are currently a number of charging points available. Te Chevrolet Volt and Tesla Roadster, among other vehicles, employ level 1 and level 2 chargers with minimal infrastructure (convenience outlets). Te Mitsubishi i-MiEV Table 4: Comparison between on-board and of-board chargers (as in [5]).

Chargers
Advantages and challenges On-board  and Nissan Leaf both use conductive charging, and they do so, using either ofboard chargers or basic infrastructure [4][5][6][7][8]. A comparison of conductive and inductive charging systems is presented followed by an overview of the charging standards and a discussion on the topologies presented in the literature for fast charging stations. Te economic aspects of fast charging infrastructure along with an overview of prospective areas for future research in this feld are also presented [7].
Te power level of conductive PEV chargers may be used to categorize them. Te power levels that are currently supported are level 1 (AC, L1, maximum 1.92 kW), level 2 (AC, L2, maximum 19.2 kW), and level 3 (DC, L3, higher than 19.2 kW) [32]. Te driver must plug in the cable, which is the main drawback of this arrangement. Tis is a typical issue [4]. In high-power battery chargers, conductive charging is a well-established technique [10].
Te user-friendliness of contactless charging is unquestionably a beneft. Manufacturing complexity, size, and cost are constraints, as are comparatively low efciency and power density [2,4,10,36]. Te additional power loss is a signifcant factor to take into account because energy savings are a major driver for EVs. Although most models of inductive power transfer (IPT) have weak magnetic coupling and signifcant leakage fux, the fundamental concepts of IPT are comparable to those of transformers. Te secondary side (roadbed charging) might be either stationary or moving [1,4,33]. Table 5 shows the diferent conductive charging standards and codes. Table 6 shows the diferent inductive charging standards and codes.

Battery Swapping
System. Tis type of technique allows EV users to replace partially or totally drained batteries with fully charged batteries. BSS (battery swapping stations) are designated locations where the battery swapping operation takes place [2,5,34,36]. Te gracious acceptance of battery swapping stations might substantially minimize the longer charging time needed by EV batteries. By enabling customers to swap out discharged batteries for fully charged batteries while travelling, the BSS should make sure they have enough range [34].
When the management and collection of batteries are done at centralised areas, the BSS can provide a number of advantages, such as longer battery life, reduced time consumption, and comparatively cheaper management expenses. TESLA, the industry leader in the transportation sector, can now replace an EV's battery in under 90 seconds. Battery switching ofers a way to lessen or avoid load demand spikes brought on by EVs, which can result in signifcant cost savings [2,5].
Te main benefts of this system include in less than one minute, 100% of the battery's capacity is recovered with the BSS. In the event of a sufciently wide network of charging stations, the driving range is limitless, and the driver does not need to get out of the vehicle. Additionally, the battery's conservation (failures, service life, etc.) is not the user's responsibility, and batteries maintained at the stations might participate in the vehicle-to-grid (V2G) initiative.
Te drawbacks include the fact that electric vehicle battery models are not standardised, necessitating the specialisation of these stations into a specifc type. Furthermore, the price of the battery's monthly rent may be more expensive than the price of fuelling a conventional ICE vehicle [36].

EV Accessories, Charging Codes, and
Requirements and Their Safety 6.1. Cables. Cables are required to charge the EVs. Te charging current and discharging current will vary depending on the battery's operating region. Te battery has to be charged at a greater charging current in order to accomplish rapid charging. As a result, the cables vary depending on the charging power level.

DC Cable Limitations.
Te types of cables that may be used in an EV are constrained to a certain DC current, which could be less than or greater than the needed rating.
To keep power losses low, thermal control should also be necessary [38]. Higher battery voltages will lower the current needed to supply the same amount of power, but it must be guaranteed that they do not cause further electromagnetic compatibility (EMC) issues.
Te charging interface and battery terminal connections may be damaged by the large currents needed for rapid charging. Tis is crucial if the battery swapping concept is thought to be practical. Inductively coupled power transmission may also prove to be a viable solution to all of these cabling and connector-related problems. Te placement of the inductive coils must be done properly since increasing the distance between them reduces the efciency of power transfer.

AC Cable Limitations.
Te maximum line-to-line voltage is signifcantly infuenced by the AC cable. Electricity providers typically set limits on the current and voltage. Assume that a three-phase supply can be used for a Level 3 (fast charging) station. Te charging station is assumed in this section to only be linked to an AC grid, ignoring the DC grid of the electric bus.

Connectors.
Te connector is used to link the EV charger and the power supply. Based on the charging power level connectors are also diferent. Te comparisons of diferent connectors are given in Table 7.

Electric Vehicles International Standards and Charging
Protocols. Te development of new charging protocols, international standards, sufcient infrastructure, and userfriendly associated instruments and software at private and public sites are all essential for the efective operation of EVs in the next few years. It is possible to evaluate a wide range of technical issues with EVs using the safety rules and internationally accepted standards. Te price of charging infrastructure and the hardware requirements for electric vehicles are correlated. It is possible that some standards and charging regulations for EVs may make the infrastructure for charging more expensive and complicated than the current electrical infrastructure.
According to Article 625-18, cables and connections for charging levels 2 and 3 must be de-energized before being inserted into a vehicle. Tis will result in higher EVSE costs. Many international organizations, including the following ones, are currently developing standards and charging rules for EVs: Diferent charging codes and their details are given in Table 8.

EV Charger's Isolation and Safety
Requirements. All EV components, including the DC-DC converter, high-voltage battery, charger module linked to the grid, and inverter (for driving the electric motor), require isolation. Te transformer is therefore a crucial part of the interaction between the EVSE and the current electrical system. When being charged, whether on-board or of-board chargers are used, the EV body must be connected to the earth. Isolation monitoring is necessary when there is no electrical separation between the battery and the charger [2].
Te scope of this standard (personnel protection system) covers the requirements for systems or devices designed to decrease the danger of electric shock to the user in isolated or grounded circuits for charging EVs [4].
Diferent international standards and technical codes for safety and isolation and their details are given in Table 9.
An international standard is a document that is developed through the consensus of experts from many countries and is approved and published by a globally    Journal of Advanced Transportation recognized body. It comprises rules, guidelines, processes, or characteristics that allow users to achieve the same outcome time and time again. International standards to meet the needs in the EV industry are being established. International standards are well developed to resolve safety, reliability, and interoperability issues in the EV industry.  Safety of EV plugs, outlets, and couplers UL 2231 EV supply circuit safety solutions for worker protection Te following is a list of current standards (as of early 2022) concerning the various aspects of EV charging, both connected and wireless. Table 10 shows the various standards and types of electric vehicle supply equipment.

Protocol for Communication between Charging Units and Electrical Vehicles
To make it possible for a signifcant number of EVs to be successfully integrated, management and a dependable communication network for public charging are required.
To maintain grid stability, communication between the grid and aggregative vehicles and the two-way energy fow will be managed. Te capacity of EVs to function as intended for metering, communication, and V2G-bidirectional power fow will determine how well they are adopted over the coming ten years [4]. Unidirectional charging shields the battery from deterioration and needs less hardware and simpler communication techniques than bidirectional charging [17].

Communication between V2G.
Te success of the V2G concept is determined not only by technological feasibility but also by PEV user behavior and expectations [31]. A twoway communications protocol is created to achieve customer allocation, and it coordinates EV assignments and, if necessary, reroutes [40]. A PHEV with V2G technology connects to the grid for the fow of electrical energy as well as for logical or control connections required for communication with the metering and for on-board controls and the grid operator. Vehicles with V2G capabilities may move electricity between the power grid and themselves as needed. Te foundation of V2G technology is this efcient, bidirectional fow [41]. In order to provide bidirectional power transfer, EVs and aggregators also require a safe and secure two-way communication network. Te application of V2G technology is further limited by security concerns about communication infrastructure [5]. Te successful functioning of V2G depends on intelligent grid connectivity, smart communications between EVs and grid operators, and intelligent metering. To verify the state of the battery and receive various instructions, communication must be two-way.
If the smart grid system is properly constructed, it has several benefts. From the utility's perspective, the smart grid's responsibility and power quality increase signifcantly when utilizing modern power electronic devices and communication technologies, and these developments make it easier to achieve the objective of continuous system monitoring.
Te smart grid's capacity to interact with renewable energy sources is one of its greatest environmental achievements. Tis may alter the market for renewable energy and provide extra support. By using intelligent control and communication systems, smart meters, and charging/discharging may be directly coordinated. We will do real-time nonlinear power valuation for charging and discharging in order to enhance returns for grid operators [35].
With the widespread use of sensors and communications, enhanced urban dispatch methods that rely on the IoT will create new opportunities for efective urban administration. It is possible to acquire trafc data and energy usage via smart meters, personal GPS, and public surveillance systems in order to more precisely predict UFCS demand and dispatch trafc and the power grid in an integrated and interactive manner [42].
Te coordination and communication between each PHEV, the transmission system operator (TSO), and the distribution system operator (DSO) must be managed via a smart metering system. To interact with the TSO and DSO, a manager might also organize and represent the vehicles. Te utilization of the vehicle-to-grid concept, PHEVs in combination with renewable energy sources, and making PHEVs a controlled load are all made possible by smart metering. Although this technology is available for use, the utility sector will need to make capital investments. Other incentives, such as the incorporation of renewable energy and real-time pricing, are crucial for the introduction of smart meters [43]. Figure 29 presents the V2G communication.
We are researching the IoT era as more physical connectivity devices become available thanks to technological breakthroughs. IoT enables further, direct physical world integration with cyber systems, enabling a wide range of new services and applications, including smart grids and vehicular communication. Te study by [44] examines a smart EV charging application that is based on smart grid and vehicle communication technology.

A Charge Strategy Based on Tokens (T-Charge).
Assume that a charging socket in this scenario has a maximum charging power of S * cs, but it also has a nonelectrical option. In other words, it is conceivable for an EV to be plugged into a charging port and not receive a charge for a while. Tis pricing model is based on scheduling plans with tokens that have been put out for communications networks. Let us suppose that Smax � l. S * cs, meaning that l or more charging plugs can be charged at once. Tactive, which is related to the token holding time in a token-based scheduler, therefore indicates the maximum duration a charging socket may be active. During a Tactive time period, after which an active socket turns inactive, the token is then sent to the subsequent inactive socket with an unserved connected EV [45].

Communication between Utility and EV.
To incorporate more EVs, appropriate communication and charging control are necessary [1,2]. Despite their increased cost, DC charging stations provide a lot of benefts, including charging at high power levels, the ability to charge more quickly, reducing the weight of electric vehicles (EVs), improved battery management systems that address issues like heating, and efective communication between owners of commercial charging stations and utility companies to improve contractual opportunities [1].
A key component of information interchange, particularly when it comes to energy estimates, pricing, and EV characteristics (driving) between companies, is real-time Te application of ZigBee technology is straightforward and requires less bandwidth. To make ZigBee technology dependable and efcient for V2G applications, however, problems including communication delays, limited memory, and interference from other devices using the same transmission line must be resolved. Te charging time at a fast charging port can be cut by up to 30 minutes. Fast charging stations for EVs and PHEVs have researched and implemented a cosine fring scheme-based voltage regulator and electronic tap changer to accommodate fuctuations in input supply and contribute to sustainable development and energy availability [8].
On the other hand, the communication network between EVs and utilities or the power market has to have high levels of cybersecurity to guard against cyberattacks on the smart grid like malicious software that alters prices or scams the system. Tese are crucial challenges since the grid network's vulnerability to installed EVs makes it vulnerable to cyberattacks. Additionally, it is important to ofer protected EV services to the visiting networks. Te cost of the home charging case appears to grow due to the SMs and communication infrastructure, favouring the PV-based workplace charging station [46].

Communication between EV and Charging Station.
Te infrastructure infuences the degree of communication between the charging station and vehicle, which afects the charging modes. An electrical outlet or connection, charging station safeguards, and a connecting cable are all parts of the EVCS, a system designed to supply an EV to recharge. It is utilized for charging in mode 3 and allows communication between the stationary installation and the EV.
Te management system's modules connect it to the various components and enable communication between them. (

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Journal of Advanced Transportation (4) Interacting with the Help Desk. Te help desk receives information about the charging system's condition from it. (5) By delivering information on customers who are utilizing the network of another charging management system (CMS) with which they are not enrolled, it maintains the accessibility of the whole network of charging stations, even if they belong to diferent CMS [36]. Figure 30 presents the communication protocols between EV-EVSE-CMS-Mobile App. Each electric vehicle (EV) must be connected to a certain interface device, such as the VC (vehicle controller), to enable bidirectional communication. Te cluster of vehicle controllers (CVC), on the other hand, is intended to supervise the charging of substantial parking lots [34].
Electric vehicles and charging stations communicate via the ISO/IEC 15118 protocol stack. Te open system for interconnection (OSI) reference model states that a protocol stack is typically the conceptual framework of a group of communication protocols.
Within a protocol, communication is carried out using predefned messages and parameters. Te defnitions of syntax, semantics, and scheduling limits are all included in each protocol. Charger power, voltage, current, tarif tables, and the desired start or end of the charging process are a few examples of crucial parameters. Charging may not even begin or may be stopped before it is fnished if one or both parties' communication is not done to the required standard. Using a protocol test system, the communication between electric vehicles and charging stations is evaluated to demonstrate compatibility [47].
Without the requirement for communication between the grid distribution infrastructure and the EV, a number of local parameters, such as the EV departure time and the voltage magnitude, may be employed to regulate the EV charging process.
Te EV user may communicate with the EV charger via on-board data communication to let them know when the next departure is. Te EV charging power rating can then be reduced based on the required amount of time and the charging energy until the subsequent departure.
A particular plug or socket establishes a connection between the charging infrastructure and the electric vehicle (EV) and communicates the maximum charge current permitted.
Te of-board charging infrastructure also houses circuit braking, fault current, and over-current protection [48].

To Communicate with Chargers (Also Known as EVSE)
(1) For the EVSE to be able to charge at the optimum rate for preserving the SOH of the batteries, it must be able to communicate with the battery pack's BMS. (2) Information and communication between the central management system (CMS) at the power utility company and the EVSE, to (a) Allow for maximum c-rate regulation based on grid supply rates. (b) Tis will also allow diferent rate metering. Tis is vital because the grid has to be ready to deliver current whenever vehicles demand large amounts of it. (c) Additionally, this could change how customers reserve chargers.
Te communication protocol utilized for all public of-board chargers will be OCPP. Tis will be broadcast over wired or wireless (Wi-Fi, GPRS, or 3 G/4G wireless) media through the web.

Future of Battery Packs and Charging Infrastructure
Te future of battery packs and charging infrastructure could involve a number of advancements in technology, such as improved battery cells, faster charging times, better thermal management systems, and improved energy storage. Tese improvements could result in more efcient charging infrastructure, with charging stations ofering more power and quicker charging for vehicles. Battery packs could also become more compact and integrated into vehicles' designs, making them easier to remove and replace. Charging stations could be equipped with solar panels to generate electricity on-site, reducing the need for large, external energy sources. In addition, the development of wireless charging systems could make charging more convenient and reduce the need for cords and cables. Tese advances could lead to a more widespread adoption of electric vehicles as well as increased competition among manufacturers of batteries and charging infrastructure [24]. Te improvements in battery packs and charging infrastructure could also lead to a greater variety of electric vehicles, as more powerful batteries could result in increased performance. Batteries with higher capacity could allow for longer-range vehicles, while faster charging systems could help reduce the inconvenience of waiting for a vehicle to charge. Additionally, improved thermal management systems could allow for electric vehicles to be designed with more powerful motors and bigger batteries, resulting in better performance. Tis could lead to the development of electric vehicles suitable for a wider variety of uses, such as sport and luxury vehicles. Finally, improved energy storage solutions could allow for bigger and better batteries, which could lead to longer-range electric vehicles, making them even more competitive with traditional gas-powered vehicles [25].

Conclusion
Te deployment of battery chargers, charging power levels, charger topologies, charging types, accessories, standards, communication protocols, and infrastructure for electric vehicle charging were all reviewed. Te charging infrastructure and the characteristics of the charger are also important factors that afect battery performance. Level 1, level 2, and level 3 are the three levels of charging power. Ofboard and on-board charger systems are distinguished by unidirectional and bidirectional power fow. A unidirectional charger limits hardware restrictions, makes connection problems easier to resolve, and tends to slow down battery deterioration. Te bidirectional charger enables gridto-battery energy injection. Power is constrained by the onboard charger due to its size, weight, and price. Both conductive and inductive on-board chargers are possible. It is possible to create an of-board charger for high current rates not provided by EVs. Active roadbed technologies might eventually be supported by inductive charging. On the basis of the time, amount of power, and location for charging, the appropriateness, the cost, the equipment required, and other variables, several charger power levels and infrastructure designs were presented and compared. Te development of new international standards and charging regulations; infrastructure considerations; efcient and intelligent chargers; advancements in battery technology; and user-friendly charging infrastructure at public and private sites are all necessary for EVs to succeed.

Data Availability
Te data used in this study are available upon reasonable request. For the data related queries, kindly contact to: Baseem Khan baseem_khan04@redifmail.com