Vehicle to Grid: Technology, Charging Station, Power Transmission, Communication Standards, Techno-Economic Analysis, Challenges, and Recommendations

Abstract

Electric vehicles (EVs) must be used as the primary mode of transportation as part of the gradual transition to more environmentally friendly clean energy technology and cleaner power sources. Vehicle-to-grid (V2G) technology has the potential to improve electricity demand, control load variability, and improve the sustainability of smart grids. The operation and principles of V2G and its varieties, the present classifications and types of EVs sold on the market, applicable policies for V2G and business strategy, implementation challenges, and current problem-solving techniques have not been thoroughly examined. This paper exposes the research gap in the V2G area and more accurately portrays the present difficulties and future potential in V2G deployment globally. The investigation starts by discussing the advantages of the V2G system and the necessary regulations and commercial representations implemented in the last decade, followed by a description of the V2G technology, charging communication standards, issues related to V2G and EV batteries, and potential solutions. A few major issues were brought to light by this investigation, including the lack of a transparent business model for V2G, the absence of stakeholder involvement and government subsidies, the excessive strain that V2G places on EV batteries, the lack of adequate bidirectional charging and standards, the introduction of harmonic voltage and current into the grid, and the potential for unethical and unscheduled V2G practices. The results of recent studies and publications from international organizations were altered to offer potential answers to these research constraints and, in some cases, to highlight the need for further investigation. V2G holds enormous potential, but the plan first needs a lot of financing, teamwork, and technological development.

1. Introduction

Globally, carbon taxes have been considerably more strictly enforced in the last ten years to slow the rate of global warming and climate change. The Paris Agreement began enforcing this restriction to prevent a rise in global temperature below 2 C in 2016. The international renewable energy agency (IRENA) reported that the amount of renewable energy (RE) coming from environmentally friendly sources, particularly photovoltaic (PV) and wind power plants, is increasing. According to IRENA’s worldwide plan, clean power consumption will rise from 20% to 40% by 2050; two-thirds of energy output will come from RE sources [1,2]. Furthermore, by 2050, wind and solar energy will contribute three times as much, from 20% to 60%. On a different front, measures have been implemented to effectively halt fossil-fueled vehicles’ rapid expansion.

Over the last two decades, the usage of EVs in place of internal combustion engines (ICEs) has shown promise in reducing global emission levels of greenhouse gas (GHG) in the automobile sector. Conventional vehicles must be electrified to support EVs with extended distances and more excellent propulsion. This requires sufficient charging stations (CSs) and powerful batteries with a high charge capacity [3,4,5]. The government and business organizations have recently introduced creative regulatory regulations and incentives to support essential investigations and tests to reduce the cost of an EV unit and increase user convenience concerning battery charging and servicing [6,7]. Tesla asserted that a freshly developed lithium-ion battery met its target of a 300 mile driving range per a single charging. A battery for an EV made by Samsung has a 375 mile range and requires 20 min to charge fully. To enhance user experience, the US Department of Energy (DOE) took the lead and provided incentives for building charging infrastructure near EV parking facilities.

Compared to conventional ICEs, using EVs might be more cost-effective and leave a lower carbon impact. The fuel conversion rate for ICEs typically falls below 30%, resulting in less than 60% overall efficiency. Electricity-to-mechanical power conversion effectiveness for EVs can be as high as 77%, contributing to an overall vehicle efficiency of 85–90% [8]. Plug-in EVs (PEVs) and hybrid PEVs (HPEVs) increase fuel efficiency, lower fuel costs, and produce fewer greenhouse gases than conventional internal combustion engines (ICEs). Compared to ICE vehicles, EVs have a 40% smaller GHG footprint.

Up until 2040, it is predicted that the overall emissions from ICEs will decrease annually by 1.9%. But by 2040, the widespread adoption of EVs might play a more important role in developing the marketplace for EVs and the industry. By 2030, it is predicted that there will be 130 million EVs worldwide. This number has already reached the 1.2 million mark [9]. The traditionally established power networks that were never intended to handle the significant periodic demands resulting from the irregular charging of EVs would be severely burdened by this sharp increase in EV adoption.

Additionally, while a significant electricity demand in EVs is quickly added to or removed from the power grid, electrical components like power generation and transformer systems would become highly vulnerable to this shift in system frequency. Thus, to support rapid EV expansion, the power grid must mature. Numerous government incentives are necessary to cover the high cost of enhancing or replacing the current electrical infrastructure. By spreading and positioning generating units next to the extensive EV charging network, and with correct EV scheduling, it may be possible to meet the high demand for EVs. To extract the power from the onboard charger of the EVs, the battery pack and power electronics converter (PEC) are taken explicitly into account. To execute the vehicle-to-grid (V2G) strategy, the DC power will be inverted and sent to the electrical grid during a higher demand than the enabled generation [10,11]. Directed V2G establishment might lower peak load demand, free up space for integrating RE sources, and lower charging prices.

At the charging stations, EVs can be used as electrical loads, and distributed battery energy storage (BES) systems can be employed to balance peak load demand. The grid can profit from the addition of storage components by selling electricity during peak hours, improving rotational capacity and frequency regulation. The previous ten years have seen a substantial improvement in the battery’s discharge cycle, increasing the viability of the V2G technology for commercialization. By creating control and communication links between each entity, it is possible to achieve complete synchronization and loss minimization in bidirectional power flow between loads, EVs, and power grids.

Controlling electrical power and monitoring energy metering infrastructure (EMI), two crucial components for the construction of V2G systems, are primarily managed by centralized or decentralized control. V2G technology should be used to its fullest potential in a marketing strategy that benefits both the grids and the EVs. By increasing or reducing the embedded EV fleets, the grid advantages and profit are viewed as the primary operational knowledge in the centralized approach. Increasing the power grids’ operational effectiveness is crucial for EV mobility. In a decentralized control system, specific steps are taken to keep the grid operating correctly and to regulate the charging and discharging cycle that applies to EVs [12,13]. Power generation costs, loss, and variable loads must be reduced to successfully establish and match ideal relationships between EV customers and grid companies. At the same time, the diversity of the electrical system is increased.

V2G communication networks diverge in comparison to current communication technologies in several aspects, including the mobility of the vehicle, its location, how it charges and discharges, how it drives, and its short communication range. For the V2G systems to accommodate the significant number of EVs anticipated to engage in dynamic charging/discharging, authentication in terms of security must be quick and effective. To facilitate V2G transportation, a dedicated short-range communication (DSRC) protocol comprising IEEE 802.11p and IEEE 1609 Wireless Access in Vehicular Environments (WAVE) has been developed specifically for communications-based successful defense applications, including vehicle to infrastructure (V2I) and vehicle to vehicle (V2V). DSRC provides communication between automobiles and electric power networks. To ensure highly reliable communications, V2G systems require a closely managed spectrum. Since it can take several seconds to identify adjacent stations and establish a link, WiFi is not a promoted protocol for V2G systems.

Motivation and research gaps: Researchers currently concentrate on mathematical modeling, optimization methods, and algorithms to effectively integrate EV technologies with the power grid [14,15]. Another current topic is the use of dispersed renewable energy sources (RESs) to charge EV batteries, such as solar and wind energy. Additionally considered is the examination of BES systems and analyses of their life cycle, the environmental effects of EVs, and load scheduling. The impact of EVs on cutting-edge grids, like micro/smart grids, is still unclear [16,17]. In addition, no single research publication, except a sizable book chapter, has even briefly described the present V2G trends, difficulties with battery and grid characteristics, practical business models, different types of running EVs, and research gaps throughout these areas of study, as are presented in

Table 1. Summary of a recent review of EV-to-SG cyber-physical systems.

Ref	Years	Contributions	Research Gaps
[18]	2020	V2G distribution networks	V2G generation, transmission, and cyber-security
[19]	2020	Charging/discharging control for G2V	Cyber-security and communication standards and protocols
[20]	2021	V2G concept, technology, obstacles, and barriers	Transmission distribution and cyber-physical security
[21]	2021	V2G energy management, communication standards, and protocols	Transmission distribution and cyber-physical security
[22]	2021	EV and V2G reliability, cost, and emissions.	Cyber-security, communication standards, and protocols
[23]	2022	Cost and environment-wise benefits	V2G communication standards and protocols, and cyber-security
[1]	2022	V2G connection and benefits	Cyber-security, communication standards, and protocols
[24]	2022	V2G network security issues	V2G cyber-physical transmission and distribution
[25]	2022	V2G virtual power plants	Cyber-security and charging station communication standards and protocols
[26]	2022	G2Vcharging station standards	Cyber-security issues
[27]	2023	V2G and G2V power transfer bidirectional converter	EV charging station standards, transmission, distribution, and cyber-security issues
[2]	2023	V2G power transfer operations and control	CPS communication standards and protocols and cyber-security
[28]	2024	V2G power electronic interface	CPS communication standards and protocols and cyber-security
[29]	2024	V2G hybrid backup system and techno-economic analysis	V2G cyber-physical transmission and distribution, and charging station communication standards and protocols

.

Contribution: Investigations on the effects of EVs and V2G systems on battery cycle, power quality, and many other areas are required because V2G technology may become more pervasive in the upcoming years. The problems of implementing V2G techniques, potential solutions, present V2G practices in business and academia, commercial designs, and research gaps are examined in a well-organized manner in this article. Contributing to these concepts in this article are the following points:

• A complete remake of the types and architecture of the V2G system.
• An in-depth analysis of the V2G industry perspective and operations, both present and future.
• The potential of V2G for distributed generation and a smart grid in the future.
• The communication networks for the application of a V2G distribution system.
• A discussion around charging station communication standards for the V2G distribution system.
• Problems regarding V2G application affecting the grid and the vehicles.
• Techno-economic analysis and initiatives for V2G application.
• A showcase of current research initiatives and legislative initiatives to address V2G problems.
• A definition of the research gaps connected with every issue and the available literature’s existing answers.
• An analysis of the harmonics profile and power quality of the V2G technology.

This manuscript is organized as follows. The advancements in and charging system of EV technology are presented in Section 2. The V2G system, its impact on the power system, its present scenario and growth, industrial outlooks, and electric mobility-driven socio-environmental vulnerabilities are described in Section 3. Section 4 presents the current V2G challenges. The proposed effective V2G solution is presented in Section 5. Finally, Section 5 offers the conclusion and future recommendations.

2. EV Technology

2.1. Advancement in Electric Vehicle Technologies

Electrical energy and motors are used in EVs to drive the wheels. The onboard charger (OBC), the energy storage system (ESS), mainly the battery and supercapacitor, the electric motors, and the electric power control unit and drivetrain are the essential EV parts, as seen in Figure 1. The OBC converts the electrical energy from an AC outlet to charge the ESS. As the electric motor accelerates, an inverter converts the battery energy storage (BES) voltage from DC to AC. The controller conserves the desired wheel speed while adjusting the desired voltage and frequency of the DC-AC converter.

Regenerative braking (RB) allows the reversed motor to run, functioning as an alternator to charge the battery and improve fuel efficiency. This happens while the vehicle is braking or moving downhill. Over the steering wheel, paddle shifters allow one to manually control the level of RB [30,31].

Inverter units are not utilized in DC motor-based EVs; instead, a low-voltage DC-DC converter reduces the high-BES voltage to a low voltage (12 V), required to power the electronic components. In a neutral power supply, control, motor control, gear drive, load management, electronic systems, and RB are all managed by a vehicle control unit. The BES is essential because increasing the energy per battery unit can result in longer driving distances with better fuel efficiency and economics. A 64 kWh Li-ion battery (LIB) from HYUNDAI was estimated to have a 386 km driving range. The charging and discharging patterns of the EV, however, change the battery’s life cycle [32,33]. EVs frequently experience delayed acceleration due to a decline in battery density, necessitating replacement and requiring an extra battery.

The charging power also decreases when the outside temperature exceeds the battery’s normal range. To lessen the issue, a battery heating technique is typically supplemented. The battery management system (BMS) keeps track of the battery cells’ charge or discharge. The BMS uses a relay device to alter a battery charge state by disconnecting or connecting additional devices when a battery charging or discharging level deviates from the string [34,35,36,37]. The acceptable speed achieved by the wheel is greatly outweighed by the motor’s speed for an EV. This results in a mismatch when the available motor revolutions per minute (RPM) is transferred to the automobile wheel. A reduction device operates to limit the motor’s RPM, allowing the transmission mechanism to turn the wheel at a speed that is appropriately slower and with more torque. According to the drivetrain architecture, EVs can be divided into different classes, as seen in Figure 2, and internal drivetrains, shown in Figure 3.

A BEV is derived from BES, electric motors, and a drivetrain rather than an ICE. A charging point is used to recharge the battery. The pedal acceleration controller signal, which is supplied through the steering wheel via a mechanical cog arrangement, controls the frequency of the output DC voltage of the battery. Additionally, the battery is recharged when the BEV uses RB. Ford Focus Electric, BMW i3, Tesla X, and Model 3 all have an all-electric system architecture. Approximately two-thirds of the more than 10 million EVs stocked and the 3 million newly registered in 2020 are BEVs. In France, the UK, Norway, the USA, China, and the Netherlands, the newly registered BEVs are almost 60%, 62%, 73%, 78%, 80%, and 82% of all registered EVs [38]. A BEV unit costs around USD 40,000 and has a 55 kWh battery.

The HEV uses a gasoline tank and BES advantages to power ICEs and electric motors. The petrol engine and electric motor provide torque, which is used to rotate the wheel in real time. The HEV system’s inability to be charged by the power grid due to its lack of an electrical charging connector is one of its key distinguishing characteristics. Only the use of the ICE, RB, or a combination of both can recharge batteries [39,40,41]. Like a conventional ICE, the fuel tank is refilled at a petrol station. Leading manufacturers of HEVs include Honda (Civic Hybrid) and Toyota (Prius Hybrid).

The PHEV considerably enhances the effectiveness and performance of the EEV. Unlike the HEV, the EV battery could be charged via charging stations (CSs). This series of hybrid operations offers the chance to examine the use of non-renewable (gasoline) and renewable (biodiesel) fuels to power the vehicle. The car runs on an EV system. When the BES runs out of power, or the vehicle reaches highway cruising speed (about 70 mph), the ICE takes control, and the EV behaves like a typical car. At this point, RB charges the ESS, thus lowering the cost of running the vehicle [36,42]. As a result, the onboard BES capacity needed for PHEVs (14 kWh) is less than half of what it is for BEVs. A PHEV costs USD 50,000 and typically has an electric range of 40 to 60 km. Considering an 8% selling price decrease in 2020, the quantity of newly issued PHEVs tripled. Less than 10% of the 435,000 light commercial vehicle (LCV) units produced worldwide in 2020 were PHEVs [38]. Several large automakers produce PHEVs. The mass audience is familiar with the BMW: X5 xdrive40e, i8, and 330e; Ford: Fusion Energi and C-Max Energi; Mercedes: GLE550e, S550e, and C350e; and Porsche: S E-Hybrid and Cayenne S E-Hybrid.

The FCEV takes advantage of recent advancements in FC technology. Its H2 fuel tank is topped off at an H2 charging station, and this H2 is then supplied to the FC, where chemical energy is transformed directly into electrical energy. Between 40% and 80% of FCs are efficient. The FC energy output powers the motor or refuels the BES systems. Despite being hyped up when it entered the automotive market in 2014, the FCEV’s registration is still approximately three orders lower than EVs due to a shortage of household charging facilities and hydrogen refueling stations [38,43,44,45]. Approximately 35,000 FCEV units are used by over 540 HRSs around the world. The global hydrogen refueling station count climbed by 15% in 2020, contributing to roughly 40% growth in FCEV stock. Nearly 30%, 27%, 24%, and 12% of the world’s FCEV units and 9%, 12%, 16%, 25%, and 17% of the world’s hydrogen refueling stations, respectively, are located in Korea, the USA, China, Japan, and Germany. Korea presently leads the FCEV market with the largest quantity of FCEV supplies, nearly 10,000 FCEV units based on the IEA projection for 2021 [38,44]. The FCEV operates differently from other kinds of EVs since it emits zero emissions. Among other FCEVs, the Toyota Mirai and Hyundai Tucson have drawn the general public’s attention.

The solar EV’s photovoltaic (PV) panel on top of the vehicle charges its batteries, which power the vehicle’s motor and steering and controlling mechanisms. Recent times have seen a lot of interest in PHEVs with solar power. The vehicle, parking lots, and CSs are all highly suitable [46,47,48].

Table 2. Overview of commonly used EVs.

EV Technology	Power Rating (kW)		Charging Time		Features	Drawback
	AC	DC	First (min)	Slow (hour)
BEV	40–221	4–22	18–90	3–13	Zero carbon emissions Low driving cost Regenerative braking	Driving distance limitation Off-road driving Vulnerable to cyber-attack
HEV	-	21–185	<20	2–22	Improved fuel efficiency Off-road driving	Higher cost Power transmission loss Challenging for EMS
PHEV	50–350	1–19	-	1.5–20	Zero carbon emission Low operating cost Regenerative braking	High initial cost Heavyweight Unable to first charge Power transmission loss
Solar EV	50–300	2–22	20	4–7	No emission No external power source Regenerative braking	Limited driving range Higher cost Depends on weather
FCEV	100		Refueling time		Fuel efficiency No emissions Regenerative braking	Refueling station is not available Lesser durability

overviews the relative benefits and drawbacks of readily accessible EVs. The EVs are also divided into groups based on how much electricity they use. A high-capacity battery pack powers the extended-range EV propulsion. A small engine generator charges the battery, which could offer an increased driving range of over 100 km per two liters of fuel. More studies on EV-applicable batteries and energy storage systems, battery management systems, and new communication protocols are present in [2,49,50,51].

2.2. Advance EV Batteries

Advanced batteries are essential for the enhancement of range, charging speed, safety, and sustainability as EVs continue to develop. The constraints of traditional LIBs are addressed by several innovative battery chemistries and architectures.

Solid-state battery (SSB): Compared to standard LIBs, SSBs offer improved security, faster charging, and a higher energy density, making them a revolutionary development in EV-ESS. Solid electrolytes are used in SSBs instead of liquid electrolytes, which reduces the possibility of leaking and thermal runaway and improves battery stability in general. The capacity of SSBs to greatly extend the EV range is one of their main advantages. They can outperform existing LIBs by 50–100% in terms of range, with energy densities surpassing 400 Wh/kg. Lithium-metal anodes, which boost performance while lowering battery weight, are also made possible by solid electrolytes. Additionally, SSBs offer quicker charging speeds; some prototypes have shown an 80% charge in less than 15 min. Additionally, they have longer lifespans; they may last up to 1000 charging cycles with limited or no deterioration. Nevertheless, large-scale production challenges, material stability, and high manufacturing costs are still problems. Prominent firms like Solid Power, QuantumScape, and Toyota are currently working on commercial applications, and major production is anticipated by 2027–2030. SSBs have the potential to completely transform EV technology after they are developed, increasing the affordability, efficiency, and environmental sustainability of EVs [52,53,54,55].

Lithium–sulfur (Li-S) battery: Since Li-S batteries have up to five times the energy density of traditional lithium-ion batteries, they are quickly becoming a revolutionary technology for EVs. Li-S cells use sulfur, a readily available and eco-friendly substance, in place of expensive nickel- and cobalt-based cathodes, in contrast to conventional batteries. Li-S batteries, which have theoretical energy densities of more than 500 Wh/kg, might significantly lessen concerns about range by allowing EVs to go more than 1000 km between charges. Furthermore, sulfur is far more plentiful and less expensive than elements like cobalt, which makes Li-S batteries an affordable and environmentally friendly substitute. Major issues still exist, though, such as the “shuttle effect,” which occurs when Li–polysulfides dissolve throughout the electrolyte and cause a quick loss of capacity and a decrease in battery lifespan. To increase stability and cycle life, researchers are creating solid-state electrolytes, sophisticated cathode coatings, and nanostructured materials. Significant companies and academic organizations are driving Li-S technology breakthroughs, including NASA, Oxis Energy, and Monash University. Li-S batteries, which offer an ultra-lightweight, high-performance ESS that transforms EVs and sustainable mobility, could become economically viable by 2030 with advancements in material design and electrolyte stability [56,57,58,59].

Li-Air Batteries: An ultra-high energy density concept called the Li-Air battery has the potential to completely transform EVs. Li-Air batteries offer an unparalleled lightweight and high-range ESS, which could enable EVs to drive over 1500 km between charges. Their prospective energy density exceeds 1000 Wh/kg, which is roughly ten times that of traditional LIBs. Li-Air cells, compared to conventional batteries, employ atmospheric oxygen as a reactant, doing away with the need for a bulky cathode and drastically lowering battery weight. Commercialization is hampered by issues like sluggish charge rates, a limited cycle life, and energy efficiency losses. To improve durability and performance, researchers are investigating solid-state electrolytes, sophisticated catalysts, and nanostructured electrodes. Prominent establishments such as Toyota, Cambridge University, and Argonne National Laboratory are advancing Li-Air technology. Li-Air batteries have the potential to revolutionize EV technology and enable ultra-long-range EVs by 2035 if they are successfully brought to market [60,61,62,63].

Sodium-ion (Na-ion) batteries: For EVs, Na-ion batteries show promise as a low-cost, environmentally friendly, and safer substitute to lithium-ion batteries. Sodium is readily accessible and abundant, unlike lithium, which lessens reliance on rare elements like nickel, cobalt, and lithium. Because of this, Na-ion batteries are a cost-effective and sustainable choice for widespread EV adoption. Na-ion batteries approach li-ion performance, with energy densities of 160–200 Wh/kg. They also offer improved cold-weather performance, faster charging, and increased safety because of their non-flammable electrolyte. They are perfect for entry-level EV, two-wheeler, and ESS applications, despite having a lower energy density than cutting-edge lithium-based technology at the moment. The commercialization of Na-ion batteries is being accelerated by prominent firms such as BYD, CATL, and Faradion; mass production is anticipated by 2025–2030. To make it competitive with LIBs, research concentrates on enhancing anode materials, boosting energy density, and extending cycle life. Na-ion technology possesses the ability to democratize EV adoption globally by providing a low-cost, environmentally friendly, and worldwide secure battery solution, lowering costs and opening up electric mobility to millions of additional individuals [64,65,66,67].

2.3. EV Charging Stations

EVCSs are a crucial part of the infrastructure for the effective use of EV technology. To increase EV usage and lower carbon footprint, nations including China, Japan, US, UK, and other European countries have sent out guidelines and processes to install small- to large-scale EVCSs [68,69,70,71]. For instance, the US government projected that 600,000 charger plugs would operate by 2021 to power an anticipated 18 million EVs. An EVCS may quickly and easily charge a vehicle by plugging the EV connector’s plug into an electrical outlet. One end of the connector is put into the charger to charge the EV. The EV supply equipment (EVSE) units typically cost USD 300 to USD 1500 for Level 1, USD 400 to USD 6500 for Level 3, and USD 10,000 to USD 40,000 for DC rapid charging, respectively. The excess charger cost, which ranges from USD 3000 (Level 1) to USD 51,000 (DC rapid charging), directly affects the installation cost of the EVSE. The following categories are frequently used to group EVCSs:

• The residential CS, in which the end-user takes power. The wall-mounted interior outlet is used to charge the vehicles whenever out of use, especially at night;
• The public CS and commercial CS, which are used to charge stationary automobiles in parking lots;
• Fast CSs (>40 kW), which are ideally suited for high-performance EVs as they can deliver 60 miles of backup power in just 10 to 30 min of charge;
• The zero-emission vehicle (ZEV) CS can provide 15 min of charging to travel approximately 200 miles. This kind is used by the California Air Resources Board (CARB) to grant credits to drivers of non-emissive vehicles.

Several standards are established globally depending on the power rating and charging level for EV charging. The level and power of electricity flow while charging are considered by the Chinese GB/T 20,234 [72] and North American SAE-J2293 [73] standards. IEC-62196 standards are utilized in some regions of China and Europe, and they evaluate the nominal power used besides the charging period. Additionally, precise guidelines are followed when producing the EV’s parts. The CHAdeMO standard is considered by the Japanese government and Tesla manufacturing facility when building EV charging infrastructure and choosing componentry. In addition, the design of the inlets, outlets, interfaces, and plugs for EVCSs follows the IEC 61851-1 and IEC 62192-2 standards [72]. Reference [21] thoroughly summarizes the EV charging connectors and ports in China, Japan, the USA, and the EU.

Various EV charging modes offer various charging facilities and serve multiple purposes. The charging modes are as follows:

• Slow charging (mode 1)
• Semi-fast charging (mode 2)
• Fast charging (mode 3)
• Ultra-fast charging (mode 4)

A summary of the different charging standards is presented in

Table 3. Charging standard summary.

Standards	Source	Phase	Level/Mode	Current (A)	Voltage (V)	Advantages	Disadvantages
SAE-J1772	DC	DC	Level 1	16	120	Frequently used in North America, integrated safety features, ensure various EVs and CSs are compatible, weather-resistant	No DC fast charging, slower charging speeds, bulky connector, inadequate futureproofing
			Level 2	32–80	240
	AC	Single	Level 1	80	200–450
			Level 2	200
IEC-62196	DC		Mode 4	400	600	Adoption in Europe, AC and DC charging support, future-proof design, higher charging power, durable and more secure	AC charging limitations, bulkier design, high infrastructure costs
	AC	Single	Mode 1	16	120
			Mode 2	32	240
			Mode 3	32–250	250
IEC-61851-1	DC	DC	Mode 4	200	400	Covers AC and DC charging and multiple power levels, global recognition, interoperability, scalability, and safety features	Complex implementation, connectors not defined, limited control features, Modes 1 and 2 deliver comparatively insufficient power
	AC	Single	Mode 3 (dedicated) and Mode 2 (non-dedicated)	32	250
		Three		32	480
		Single	Mode 1 (non-dedicated)	16	250
		Three		16	480
Tesla-NACS	DC/AC	DC, Single, Three	all	Manufacture recurred	500–1000	High power capability, AC and DC unified connector, supercharger network, industry adaption, lightweight, simplified, and efficient design	Compatibility issues, supercharger pricing inconsistency, other EV manufacturers are required to update vehicles or supply adapters

.

Wireless EV charging stations (WEVCSs) have recently gained popularity because they offer greater security and convenience than traditional EVCSs. This produces an effective electromagnetic field causing a voltage to be induced across the EV charging device’s onboard receiver portion [74,75,76]. The induced power subsequently charges the ESS. Maximum power is conveyed at the resonance frequency of the receiver, and the transmitter side is always kept close to that limit by incorporating compensation systems on each side. The schematic for EV wireless and wired charging is shown in Figure 4. The car is kept still while charging in static WEVCSs. The wireless transmitter is installed beneath the surface in parking garages or lots, and the EV’s reception device is affixed to the lower side of the car. On a different note, wireless charging is possible even as the vehicle is moving using active WEVCSs. As a result, the battery’s capacity and dimension could be decreased since it is being charged during the journey. The WEVCSs are divided into four categories [77] based on how they operates: capacitive wireless CS (CWCS), resonant wireless inductive CS (RIWCS), permanent magnet-gear wireless CS (PMWCS), and inductive wireless CS (IWCS). A comparison is present in

Table 4. Comparison of EV wireless charging stations.

Charger Category	Power Transfer	Operation Range	Auxiliary Units	Features
CWCS	7.7 kVA	100–600 kHz	Filter Rectifier Magnetic gear	Capacitive coupling No transmitter–receiver sets Electrostatic induction principle
RIWCS	22 kVA	10–150 Hz	Filter Rectifier Series–parallel compensating	High-quality resonant factor Transmitter–receiver coil match
PMWCS	11 KVA	<150 Hz for 1 kW	Filter Rectifier	Permanent magnet and armature winding Coupled motor generator
IWCS	3.7 kVA	19–50 kHz	H-bridge circuit Filter Power factor corrections Rectifier	Operation range Electromagnetic induction

. WEVCSs are currently not widely available for purchase. Because of the considerable conditions of technological developments and the realization that the majority of the current systems still act as testbeds, one of the main factors concerns the state of standardization. Another problem is that from a technological perspective, many of the arrangements that have been evaluated and put into use have not achieved sustainable levels of energy transmission. In any case, the substantial investigations are very encouraging; therefore, the issue of commercialization may be settled sooner rather than later. The potential of dynamic charging was a major factor in the initial interest in wireless power transfer systems for EVs. The WEVCS standards are G106-9 by Japan; C95.1 and P2100.1 by IEEE; J2836/6, J1773, J2847/6, and J2954 by SAE; 61980-1 and 62827-2 Ed.1.0 by IEC; and 19363 by ISO [78].

3. V2G Prospective

3.1. V2G System

The dominant artificial intelligence technologies, communication, control, and electrification may be impacted by EV technology in the future. The recent introduction of SG concepts has given rise to several sophisticated ways to implement V2G technology, which simplifies the transfer of electricity between EVs and the grid through a sustained communication system and management and control protocols. The three new grid-connected EV arrangements are vehicle to vehicle (V2V), vehicle to home (V2H), and V2G [1,2,79]. The V2G system framework is shown in Figure 5.

Electricity through the power grid may be used as a load and, when necessary, as a source for the grid thanks to the V2G technology, which exploits EVs as a power supply and grid stabilizer. The transfer of any extra power the EV generates into the electrical grid with enough coordination may allow it to be utilized as an RE source, enhancing electricity stability, dependability, and efficiency. The variety of fuels (coal, petrol, and others) generated in emerging nations is expensive and harmful to the environment. In these nations, where power is expensive but in great demand, an EV might be a more environmentally friendly option. Additional features like frequency and voltage spinning and control reserves can be made more accessible by V2G technology [2,80,81,82]. A V2G-enabled vehicle requires three features: an energy source, a communication network for the electrical grid to access the vehicle’s electricity, and a high-precision measuring technology to monitor the electric power supply.

The V2G approach continuously monitors and regulates the power transmission across the grid and EV to ensure adequate performance, maximize profit, and lower GHG emissions. Unidirectional and bidirectional models comprise most of the V2G’s power flow classifications. The V2G system may considerably impact the internationally distributed infrastructure of existing electricity grids. Through household or commercial CSs, when equally slow and fast charging can be used, EVs are typically connected across various geographic areas. Domestic locations frequently use slow charging (Levels 1 and 2), but commercial EV refueling uses rapid charging (Level 3) and DC charging [27,83,84,85]. The V2G technology’s functioning schematics are shown in Figure 6. Understanding the charging/discharging characteristics and lifespan of the BES inside EVs is essential.

3.2. Impact on Grid System

3.2.1. Improved Power Quality and Demand Management

The use of V2G technologies is efficient for enhancing power quality, particularly when considering a contemporary SG or microgrid with dispersed RESs. However, the DERs inject voltage and harmonic surges because of their sporadic nature. Along with varying voltage imbalances, reactive power flow also happens. Onboard charge control devices, i.e., active power filters and synchronous compensators, may be enabled by creating suitable integrated control techniques for the EV. Most DER-related issues may be resolved by adequately driving the electrical system [86,87,88,89]. A bidirectional battery charging system is also used for an active filter in local-home EV grid connectivity to keep the electrical grid’s power quality within stable bounds.

The adaptability of an EV to arrange for charging and discharging is the main benefit of leaning into V2G technology in recent years. Since the generation is more than enough to meet the demand throughout off-peak hours, the EV might be hooked in, and the additional power might be utilized to charge the vehicle. According to this, the EV may supply electricity directly to the grid using the proper converter levels and controller algorithms to satisfy peak electrical demand, thus avoiding the need for pricy peak power plants. Improved load demand results from scheduling EV charging during off-peak times, which lowers electricity expenses. The V2G process may be successful in the electrical network because it can handle loads in various ways, including load shifting, load building, power conservation, peak clipping, valley filling, and flexible loads [17,90,91,92,93]. The integration of several EV fleets, held on backup for similar eventualities, may meet the requirement for additional electricity when electricity demand surges at a specific time. This can significantly enhance the ability to control the flow of power. Additionally, EVs can be integrated into a microgrid network utilizing a bidirectional DC/DC and AC/DC converter with a conventional DC link; a coordination control technique is frequently employed using an individual EV fleet, such as a car park layout.

The capacity to react fast to shifting frequencies and voltages is one of the main benefits of connecting EV vehicles to the grid. V2G can offset grid voltage and frequency variation over the established limits by v-f regulation. Additionally, EVs could increase the grid’s voltage by adding voltage through onboard BES, controlling the reactive power flow in both directions. Additionally, it acts as an oscillating backup of isolated power systems and aids in absorbing ramp power [94,95,96].

3.2.2. Support for RESs

The EV’s eco-friendly onboard ESS might accommodate RESs. When the conditions are not ideal for producing significant electric power, utilizing the electrical power from the BES of the EV could fulfill its excess load requirement. The EV could function as a reserve for intermittent RESs [97,98,99]. To obtain the voltage needed for the DC connection from the EV battery, a boosted DC/DC converter is typically utilized in conjunction with an appropriate motor drive. The operational H-bridge inverter stage receives this voltage. The control algorithms then control the output frequency and voltage in reference to the ratio-and-resonant controllers. Additionally, a second buck converter may offer a DC link with a 5 V direct voltage to power the onboard peripheral devices of the EV. In a microgrid, a power injection point between different remote RESs might be connected to residential or commercial EV parking lots wherever bidirectional power transfer is allowed [12,80]. With V2G, the microgrid operation’s general reliability and load dispatch may be more easily implemented.

3.3. V2G Present Scenario and Growth

The three largest EV markets in 2018 were in the Nordic countries (Sweden, Norway, Iceland, Finland, and Denmark), the US, and China. Nearly 11% of EVs were distributed per person in the Nordic region, accounting for about 40% of new EV sales. The EV30@30 campaign was launched by the clean energy ministerial (CEM) in 2020 to increase the worldwide EV share to 30% of the automotive market [100]. A staggering number of EVs are predicted to be on highways by 2030 (about 245 million), roughly 30 times the current projection. EV sales may reach approximately 1.5 billion by 2040 [101]. Increased technological advancements across all supply lines, including BES, advanced PECs, adaptive control strategies, and the data science perspective, makes the V2G culture more and more alluring as time goes on. A thorough survey analysis concluded that automobile users’ budget is the main variable influencing EV ownership and sparks the general public’s curiosity about using sophisticated EV features like V2G technology. It is becoming more common for EVs to plan to use V2G services. Over 50 million new users might join the V2G program between 2016 and 2030, according to an estimate made in 2016.

The estimated expansion of EV automobile sales from 2022 to 2030 is shown in Figure 7 [102]. The estimate states that until 2030, the total amount of PHEVs and BEVs could increase almost every five years. The chart shows the overall amount of power generation needed to meet the estimated load demand and splits it down to possible contributions from distributed variable RESs, V2G potential, and other generation capacities.

3.4. V2G Industrial Outlook for Investors and Policymakers

Over the past ten years, the EV marketplace has experienced rapid growth. The market shares of EVs have increased globally between 2010 and 2020 by 0.9%. The increase in worldwide EV supply from 2015 to 2021 is shown in Figure 8 [103]. The most significant challenge is the inability to deliver and arrange the V2G approach effectively due to the absence of technological maturity. The only widely adopted V2G standard is the Japanese CHAdeMO standard, which supports bidirectional power transfer [104]. But until 2019, only a small portion of the Japanese, Chinese, North American, and Nordic markets had adopted the CHAdeMO standard. Nissan, Mitsubishi, and Renault are the industry leaders in V2G, supplying almost 50% of all field V2G installations. More EV standards must be updated to facilitate effective bidirectional energy transfer across the V2G.

The absence of organized regulatory frameworks to standardize V2G practices throughout frontiers is another significant barrier to a successful V2G business strategy [105]. Numerous academics and the automotive industry’s R&D division have offered their opinions and views. Figure 9 illustrates how the business model calls for a framework of V2G architecture for the complete supply chain, which typically consists of three main parties: a power grid operator, a car manufacturer, and EV buyers. The grid utility model arranges finances, establishes the program timetable, and presents client offers. After receiving these facts from the utility, the manufacturing company accepts a fixed-fee tariff rate. After that, necessary charging control techniques and IT systems for V2G electrical power are started, emphasizing the provision of the best client experience. The end user then accepts the incentive compensation schedules the electrical grid provider established and chooses to participate in the electrical power transfer via smart charging. Adopting the standards currently used in Japan might subsidize the demand for standardized V2G deployment worldwide [106]. However, this necessitates a considerable overhaul of the global standards that are now applied to the design of EV chargers and the distribution of battery backs. For V2G to develop into a planned and successful business model, it will undoubtedly take more time, money, and support from stakeholders and customers, as well as significant government incentives.

3.5. Electric Mobility-Driven Socio-Environmental Vulnerabilities

Although the possibility of widespread EV adoption and the use of V2G communication technology appears to offer an acceptable way to regulate grid load demand and open up additional revenue opportunities for consumers, several underlying socioeconomic and environmental challenges must be considered. V2G practices are most feasible for wealthy and upper-class individuals who can purchase an EV unit. The risks of externalities include hacking, cyber-attacks, and privacy violations against those who benefit from V2G by those who live on the margins and cannot purchase EVs. When individuals receive various social standards and advantages due to owning an EV and participating in the V2G program, the differentiation could spread nationally, guaranteeing unequal access and exclusivity, perhaps contributing to increased inequalities within the EV ecosystem [107,108].

Although non-renewable energy sources may have a significant carbon footprint, EVs do not directly warrant emissions. Environmental risks also emerge from mining, processing, manufacturing, and constructing onboard batteries. Emissions from commercial vehicles often manifest as airborne pollutants and GHGs. A practical evaluation of these pollutants frequently derives from initial and well-to-wheel (W2W) analysis. Initial emissions from ICEs are to blame, but virtually little is produced directly by EVs. The W2W emission considers all emissions produced at various phases of automobile design, manufacturing, and use. The extraction of oil and gas reserves, the production and distribution of liquid fuel, and the burning of fuel for ICE transportation are the main contributors to the W2W for ICEs. Since electricity is needed to power EVs, consideration should be given to the emissions related to traditional power plants and the mining of fossil fuels for power plant operation. HEVs have a larger carbon footprint than BEVs and others since they consider both the ICE and battery units. According to predictions, HEVs might lower CO₂ emissions to about 250 g/mi by 2030, as opposed to about 350 g/mi for ICEs [109,110,111]. Establishing an environmentally friendly power grid is understood to be necessary for HEVs to reduce their carbon impact. The CO₂ impact of a single HEV configuration traveling between borders could fluctuate dramatically since the cost of operating a power plant differs from nation to nation. EV powertrains are essential for cutting CO₂ emissions and utilizing fuel [112,113]. Depending on the details concerning the hybrid systems and their chosen arrangement, implementing mild-hybrid technology may offer an economically feasible fuel economy approach [114,115]. Major forest areas are being destroyed primarily to mine raw minerals, which results in increased carbon emissions and severe disruptions to the local environment and humanity’s way of life. Additionally, the soil, water, and air around these places are harmed by the disposal of dangerous substances like trash and output.

Retail EV outlets are insufficient and unable to handle most EV-related problems due to inadequate technical knowledge. Transiting personnel from ICEs to EV schemes is challenging and time-consuming, requiring the specialized instruction and dissemination of regulations, standards, and protocols. A company with sufficient financial support may be able to tolerate poor returns in the early stages, but this keeps younger firms from maturing until they become obsolete. Furthermore, autonomous and regionally focused EV manufacturing units encounter a distinct challenge in expanding their business due to a lack of revenue or the challenge of surviving in an expanding marketplace with developing technological advancements.

3.6. V2G Real-World Use Cases

A better awareness of the real-world implementation of V2G technology’s commercial approaches can be achieved through its practical scenarios and use cases.

V2G projects about technology are executed globally at an increasing rate. As of December 2023, over 6800 bidirectional charging stations were operating worldwide across 27 nations and 131 projects [116]. Europe has more V2G developments than any other continent in the globe, with the UK dominating the way with more than half of all projects. Although Australia and Africa remain in the beginning stages of V2G development, the USA and Asia possess a significant number of advanced V2G projects.

China has become prominent in the deployment of V2G tech projects in recent years. State Grid effectively completed settlements and integrated V2G into the North China peak-cutting and additional service market on 15 April 2020. In Wuhan, Hubei Province, the Supercharging Station was formally opened on 21 February 2023, for a zero-carbon emission V2G system by Dongfeng Motor. It has five V2G CPs and an ES technology that allows for almost carbon-free operation. The largest V2G technology public display installation in Zhejiang Province, which includes 14 V2G charging stations, was put into service in Taizhou in April 2023. With 50 V2G charging stations and battery switching capabilities, Wuxi saw the construction of Jiangsu Province’s biggest V2G project on 23 August 2023 [116].

Even though most V2G projects globally are currently in the discovery phase, they are extremely important for the innovation’s future advancement. These tests allow for the practical verification of the viability of V2G technology’s commercial plans and the discovery of further technological, economic, and social challenges. Furthermore, it is possible to progressively raise public awareness and comprehension of V2G technology.

4. Techno-Economic Analysis

Considering that the massive batteries featured inside EVs may be utilized to stabilize the system during times of peak demand and periods of lower demand, this is an exceptionally significant alternative to electrical grids. When electrical costs are low and the grid has an abundance of electricity, EVs with V2G abilities may charge and discharge economically. When electricity prices rise and the grid faces stress, they can discharge. Grid operators can quickly maintain steady voltages and frequencies using the V2G interface, guaranteeing a dependable energy supply. Gomes and Rui Costa Neto [117] expected to have 77% of energy coming from renewable sources by 2050 in Portugal; thus, this might constitute an excellent solution for its citizens. Similarly, within a market establishment, EV owners can generate financial revenue by offering similar operations to the grid, as seen in Figure 10. Nevertheless, EVs experience additional battery degradation as a result of V2G operation throughout this process. Therefore, it is also crucial to look at the situation’s financial sustainability, figuring out when this type of assistance may be beneficial for various EV users while accounting for the extra wear and tear that could be placed on the vehicle batteries. The technology behind V2G remains to be used on a reasonably significant and affordable commercial scale, despite its potential [118,119].

The ideal EV charging/discharging approach was investigated from the viewpoint of the distribution system operator (DSO) by Lei et al. [120]. Additionally, they created the best day-ahead trading plan available to the DSO within the spot market. Their paper presents two contract models for V2G interactions depending on the Guangdong provincial power market and considers the variable charging requests of various EV consumers. Their findings show that the DSO can boost marginal revenue by effectively scheduling EV charging and discharging in addition to using the best day-ahead tendering approach. Additionally, by taking advantage of times when electricity prices are low, EV users can lower their charging expenses. They can also make additional money by transferring power into the grid during times when prices are high.

Zheng et al. [121] investigated the viability of EVs for V2G applications based on two perspectives: time availability and financial viability. They assessed the suitability of three charging situations for V2G services: at home, at work, and at fast charging stations (FCSs).

In a cost–benefit investigation, their results showed that EVs have plenty of idle time in both home-based and workplace-based charging scenarios, which makes them profitable to provide V2G services in the power market. However, as V2G operations would lengthen the EV-to-grid-connection time, it is unlikely that users will set aside more time for EVs that use FCS-based charging.

According to a study by Mehdizadeh et al. [122], a combination of economic advantages and an acceptable assured price is needed to increase V2G technology adoption among Norwegians. Their results indicate that older people, people who think the V2G system is useful, people who have driven an EV before, and individuals who have a high degree of faith in the V2G system are likely to adopt V2G technology. Additionally, their survey shows that consumers anticipate a standard monthly electricity price decrease of USD 144, or 72% of the average monthly bill, as payment for their V2G investment. Additionally, it was discovered that if their EV battery remained at an optimal power level of 71%, they were potentially open to using V2G.

Guangdong Province’s carbon reduction and economic potential of V2G technology was observed by Li et al. [123]. They employed an extensive power estimate that was based on the availability of EVs in the area. Using transportation patterns, their analysis estimated EV electrical consumption, economic gains, and carbon reduction across four carbon reduction scenarios. According to their results, implementing V2G could mitigate peak–valley load discrepancies by 7.6% and cut carbon emissions by 1471 to 2873 million metric tonnes of CO₂. Their study highlights that extensive V2G integration offers financial benefits to several different stakeholders by improving grid efficiency and promoting green energy.

Nagel et al. [124] examined the possible advantages of EV bidirectional charging as well as the effects it may have on the energy industry. Norway and Denmark were the two market regions that were the subject of the investigation. Their important conclusions showed that widespread V2G implementation can have a big effect on costs in the areas under study. V2G technology mitigated the attenuation of RE, lowered the peak and trough costs of electricity, lowered price swings, and lowered the overall operating costs of energy systems. Furthermore, it was claimed that areas with little intrinsic power system flexibility and small-scale adoption had the widest price disparity across charging and discharging.

A method that uses metaheuristic algorithms to coordinate EV charging and discharging while parked was proposed by Shaheen et al. [125]. Utilizing V2G technology, this approach aimed to address the issues associated with energy demand scheduling in smart grids while also lowering the daily costs for EV customers. The outcomes of this suggested approach demonstrate its feasibility in planning EV charging and discharging operations, which lowers expenses for EV consumers by integrating V2G.

Geng et al. [126] developed a model to evaluate the expenses and earnings of V2G through the viewpoint of the vehicle. According to the findings, the estimated future value of V2G is anticipated to approach USD 7000 as battery technologies advance. This demonstrates how V2G could be more affordable than traditional stationary ESSs. Furthermore, V2G may play a substantial and profitable role in the future electrical system, provided the appropriate technological developments and utilization scenarios.

V2G technology represents a revolutionary development that has the power to completely change how we communicate with electrical power. This technology enables EV owners, by enabling consumers, to actively engage in the electricity market, in addition to providing a workable method for controlling energy demand and incorporating RE into the grid. We demonstrate how V2G can offer some EV owners a financially attractive possibility under a variety of factors by considering operating and investment costs as well as related benefits. According to the model’s results, V2G can greatly increase the individual financial viability of several participants while also enhancing several grid factors, including frequency, voltage, and the penetration and storage of RE. It is imperative to recognize that the effective implementation of V2G entails a distinct set of obstacles. It is essential to carefully consider and research regulatory concerns, vehicle and technology compatibility, and the need for infrastructure investment. To overcome these obstacles, cooperation amongst all parties involved, including governments, automakers, energy traders, and consumers, is essential.

Real-world use case: Hoseinzadeh, Siamak, et al. [127] conducted an analysis using a techno-socioeconomic-environmental case study in Spain. EVs were limited to smart charging and V2G was not permitted. They showed a greater technological ability to allocate resources than in other circumstances according to the techno-socioeconomic assessment. As a result, the 50% participation possibility was thought to be more valuable. This hypothetical scenario could reduce energy expenses by up to 10%, reduce the need for fossil fuels to produce electricity, limit greenhouse gas emissions, create jobs locally, and lead the local community in the direction of an energy-self-sufficient and sustainable city.

Gomes, Diogo Melo, and Rui Costa Neto [117] presented a V2G techno-economic analysis in Portugal. Battery deterioration, distance traveled, V2G charge/discharge cycles, charging frequency, electricity acquisition, and selling rates were some of the elements that the system considered while making its estimates. EV customers with unique traits were observed, alongside the goal of figuring out the situations in which offering this ESS would become most advantageous from the viewpoint of the EV user. According to the study outcomes, users with minimal EV usage may benefit greatly from V2G assistance once electricity costs are high (0.50 EUR/kWh), with a revenue of EUR 624 per month. However, this is not the case when costs for trading electricity regarding the grid decrease to 0.30 or 0.20 EUR/kWh.

Socioeconomic Impacts: By impacting socioeconomic integrity, urban planning, and transportation sequences, the widespread implementation of EVs has the potential to revolutionize society. EVs provide cleaner and quieter modes of transportation, improving urban populations’ quality of life and lowering noise pollution. Additionally, by offering accessible and reasonably priced transportation options, especially for marginalized groups, EV adoption fosters social inclusion. Significant economic consequences arise out of shifting to EVs, impacting marketplaces, industries, and job prospects. Innovations in electric drivetrains, battery storage technologies, and charging stations are all encouraged by the EV market [128,129,130]. These promote economic expansion, the development of jobs, and opportunities for investment in the automobile and RE industries. The adoption of EVs also improves energy security and lessens dependency on imported oil, which result in decreased expenses and increased economic resilience.

• Economic development and job creation: In areas where EV manufacture, investigation, and infrastructure development are taking place, the expanding EV industry helps to create jobs and boost the local economy. Investments in EV manufacturing and associated supply chains can boost regional economies, generate new job possibilities, and contribute to the expansion of high-tech sectors. Additionally, the shift to EVs encourages entrepreneurship and innovation in fields like smart mobility solutions, charging infrastructure, and battery technology, which boosts competitiveness and economic growth.
• Community service and collaboration: Through programs like EV clubs, advocacy organizations, and public awareness advertisements, EV adoption frequently promotes social engagement and collaboration. These community-based efforts are essential for raising consumer knowledge of EVs, resolving their issues, and advancing laws and policies that will benefit them. Additionally, cooperative projects involving local governments, corporations, and nonprofit groups as well as community-based EV charging systems aid in the foundational development of EV infrastructure, including the promotion of sustainable mobility solutions.
• Carbon trading: To create a control mechanism for lowering carbon emissions (CEs), carbon trading turns CEs into commodities for trade by creating legal CE certificates that are capable of being purchased and sold. The investigation incorporates the operational expenses of every aspect and the carbon trading process, considering V2G connectivity, encouragement for EVs, and battery degradation. To create a low-carbon economic optimization model, the goal function seeks to minimize the system’s overall operating costs. According to [131], by implementing carbon trading, CEs are further reduced by 0.4%, overall costs are reduced by CNY 276.33, system balance is improved by 4%, EV battery deterioration from V2G operations is reduced by 22.62%, and the requirement for V2G incentive is reduced by 28.5%.

5. Challenges

5.1. Battery Lifetime Degradation

While many of the novel aspects of V2G’s ancillary services, such as supporting DERs, spinning reserves, peak shaving, and frequency regulation, are fascinating, the V2G operation largely depends on the strength and longevity of the EVs’ BES. The linked load to the grid, the fundamental system parameter in V2G technology, is time-variant. As a result, the V2G discharging or charging period may alter and fluctuate quickly [132,133]. Quick charging and discharging may reduce battery life; as a result, utilizing batteries for extended periods of energy becomes less economically viable. It costs money to manage and recycle old, low-capacity batteries [134]. The onboard battery is essential for regulating and changing gears. The battery must therefore be monitored appropriately. The battery charger requires the most complex controller processes to ensure economical functioning, which can be hard with haphazard EV combinations into the grid. Moreover, it is difficult to examine the percentage of energy consumed by air conditioning, ventilation, and heating systems to the researchers’ understanding of the effectiveness of the primary parameters associated with these vehicles. As a result, this investigation looks at the air conditioning, ventilation, and heating systems of two vehicle types, EVs and FCVs, under various approaches while considering suitable driving cycles. First, Simcenter AMESim 2021.2 version software is used to simulate a precise representation of an FCV and an EV. Additionally, a thermal representation of the vehicle’s interior is constructed. Lastly, driving range and energy consumption can be evaluated in two different driving cycle types after the air conditioning, ventilation, and heating components are connected to the interior simulation and long-term dynamic model.

5.2. System Harmonics

While it is possible to regulate and sustain energy system stability by efficiently managing and coordinating the scheduling of EVs to the electrical grid, doing so intermittently has the opposite effect. Most EVs are wired into the electrical grid, and most distribution points use a single phase [135]. If the V2G is deployed and its high demand expressly loads any one of the three phases of the system, it might lead to an imbalanced three-phase process with significant voltage sags, which would change the current and voltage flow [87]. Furthermore, the grid frequency can be disturbed by injecting the harmonics connected to the PEC units into the grid. Additionally, it has been noted that the EV battery charging system produces the most significant total harmonic distortion during the summer, namely of 0.37%. The abrupt charging and discharging of a sizable EV while utilizing V2G technology may result in voltage drops and surges that may affect stability. The extra power injection into the grid during V2G operation must also be appropriately regulated; otherwise, power overflowing could damage the transformers, grid components, and protective devices [135]. Dual-function control will be used in the future to integrate EVs into the grid and lessen the harmonic pollution that associated CSs and other EVs send into the grid.

5.3. Utility Grid Liability

The fundamental idea behind using V2G technology is the introduction of the EV onto the grid. A time-of-day pricing structure enables the deployment of V2G during peak times and G2V throughout off-peak times by highlighting the early morning and late afternoon peak hours and the off-peak hours [136]. But if the procedure is not properly timed, the electrical grid can be put under stress. The electrical properties, i.e., current and voltage drops, system harmonics, and line losses, are changed by unplanned power input from the EV. EVs can tolerate power management capacity; during charging/discharging cycles, the time of use and discharge pattern both play a significant role in the burden’s size. Inserting the EV fleet only when necessary and to the necessary level is essential when electricity is transferred through the V2G distribution system. A spike in the voltage level may burden the grid’s protective switchgear and connected loads. Additionally, as the current grid system can rarely meet demands ranging from 20 to 30% of EV loading, utilizing EV battery powers throughout off-peak hours may seriously impair the operation of the power distribution system. The generated voltage differs between EVs due to varying charging/discharging systems to handle load requirements. Unbalanced generated voltages could cause voltage instability, grid imbalances, changed reserve margins, and reliability difficulties since EVs significantly impact the power grid profile more than typical loads [137]. Discharging must therefore be carried out under control. EVs are unique in that they may deliver V2G solutions, discharging when demand exceeds RE supply and charging when RE generation is abundant. This makes it possible for EVs to serve as storage devices, offer the grid additional services, help with peak shaving, boost grid dependability, and regulate frequency and voltage. V2G may conserve the collective distribution network improvements and alleviate some of the strains caused by the sustainable energy revolution with these services.

5.4. Communication System Challenge

The real-time requirement on vehicle charging/discharging procedures, position, maneuver, and speed, as well as the constrained real-time communication range throughout the network, set V2G’s communication technique apart from typical communication systems. The receiver and transmitter entity authentication process should be safe, quick, and effective when establishing a communication channel [49]. Additionally, the communication system must be economical and scalable to handle the increasing quantity of EVs and their penetration into the UG, simultaneously coordinating dynamic charging/discharging operations. A centralized or decentralized connection between EVs and the UG is possible.

A tightly controlled and guarded communication bandwidth is needed to provide reliable communications. Information concerning car kinds, owner license numbers, charging and discharging schedules, CS details, and locations must be kept as private as possible during the communication setup. Furthermore, V2G must establish a communication link when the nearest and nearby EVs and charging facilities are identified (within milliseconds). As a result of its high latency, security risks, and spectrum limitations, WiFi is now an outdated technology. As V2G moves into the data-sharing phase, privacy becomes more pressing. IEC 15118-2 [138] recommends using individual server-side authentication and transport layer security (TLS) to safeguard data flow between the EVs and organizations linked with the user identity, local aggregators, control protocols, billing transactions, and server information. However, due to the lack of trust in all end LAGs and servers, unilateral authentication (UA) frequently falls victim to impersonation and redirection attacks. As a result, mutual authorization has been added as a function to check for UA’s shortcomings on both the server and vehicle sides.

5.5. Cyber Vulnerability

Next-generation electrical systems, wearable technology, communication devices, and sensors supplant the controllers and embedded systems that have been in use in the past. Consequently, more recent cyber-physical systems (CPSs) have been considered. The CPS will serve as the foundation for the charging network, the timetable for EV operations, and the platform for communication between the charging network and EV users. Three fundamental concepts make up the implementation of CPSs in EVs. The first is a distributed and transparent cryptocurrency feature for EV services with more privacy protection built on the blockchain. In addition, enhanced EV scheduling and operating cycle handling were made possible by artificial intelligence (AI) for system decision management. The third option is the IoT for precise measurement, sensing, and continuous communication among IoT devices, charging scheduling, and internal decision-making [139,140]. Each model uses quick data transfers and works with private user information and live events. Therefore, utilizing the IoV and V2G operation requires solving a crucial and critical challenge: using secure and advanced data transfer with zero tolerance for cyber vulnerabilities [141,142].

Another major worry with the V2G system is cyber-security. Malware and cyber intrusion are risks to the connected grid and automotive infrastructure. The vehicle supply equipment is physically tempered, malicious scripts are inserted, the continuously interconnected load profile is changed, and the bidirectional power flow controls malfunction, endangering the robustness of the V2G architecture [143]. The vulnerabilities quickly grow due to being connected as V2G, which comprises all-pervasive connections. EVs connected to supply equipment infected by malware run the risk of spreading it to related EVs and other supply equipment connected to it. Critical grid infrastructure, including smart metering infrastructure, phasor management units, monitoring units, protective devices, system analysis, and operation, may be easily infiltrated. Destruction may progress due to cyber-attacks and penetration. Data-based secure privacy solutions, which primarily encrypt data, making it impossible for attackers to obtain, have been highlighted in [144,145,146] to solve the privacy protection challenges of charging/discharging data in V2G systems. However, these techniques are not appropriate for resource-constrained V2G communication situations due to their significant processing cost and complicated procedures. In [147,148,149], identity-based techniques were put forward, which primarily shield users’ privacy by obscuring EV users’ genuine identities. To secure the EV charging process, fog computing and blockchain technologies were merged [150].

Consequently, research is required to determine how vulnerable traffic management systems’ EV-sharing services are to network attacks. To consider authentic charging demand–supply relationships that are taken from the data, a data-driven simulation framework will be developed that will indicate that across the many interruption categories, cyber-security risks generate particular difficulties for EV systems.

6. Effective V2G Proposed Solution

6.1. EV Energy Storage

The charge/discharge procedure for the EV needs to be maintained sufficiently throughout bidirectional power flow across the V2G to prevent a decline in the battery’s capacity and lifetime. The powertrain is under stress when V2G is used for an extended period with an increased battery capacity [151]. Multi-object optimization methods are frequently considered in the V2G methodology to correctly manage the EV fleet, prevent battery deterioration, and increase system efficiency. The most commonly found materials for EV batteries include graphite, cobalt, copper, nickel, and lithium. In [152], battery capacity is examined to deliver the required torque to drive EV wheels and to supply sufficient energy to be restored to the distribution grid over the V2G approach to analyze the battery life cycle of an EV. The battery state of health (SOH) must reach over 75% in second-generation EVs introduced in 2016 and feature 60 kWh of LIB energy storage to power the vehicle adequately. These batteries may support a 350–500 km driving range for around 14–20 years. Furthermore, if intermediate storage could only maintain 25% of the total storage limit during V2G, it could meet the power grid load demand [153]. As a result, second-generation EV batteries would rarely need to be replaced and would be well matched to the EV drivetrain and V2G applications for their entire lifetime.

The battery’s internal resistance changes during the charging cycle, accelerating capacity fading. The contained battery pack has a predetermined maximum charging level and a discharge current limit that must be checked during every operation to avoid unfavorable consequences. The G2V (V2G) power flow reduces the battery lifetime by injecting (extracting) large peak currents into EV batteries. According to [11], the battery lasts longer for a routine EV run when the charging control is minimized compared to other common charging techniques. During the motor run, both low-frequency and high-frequency currents must be supplied. A high-frequency current peak causes the battery to degrade quickly. A hybrid ESS (HESS) made up of LIBs and supercapacitors (SCs) is suggested in [154]. The energy flow between the SCs and batteries is monitored using the authors’ field-programmable gate array (FPGA)-based controllable alternating bidirectional buck-boost converter. This FPGA also gives the converter stages the gate signal to reduce battery current overshoots. In such a composition, the battery provides the low-frequency current, and SCs provide the high-frequency current.

6.2. Grid Harmonic Preservation

The harmonic distortion produced by the charger’s power converter stages and onboard diver circuitry is another important barrier to implementing EV or V2G technology. Whenever the electrical grid distributes a current at excessive demand (between 18 and 24 kWh), the decrease in power quality caused by harmonic pollution is more prominent. To quantify harmonics, metrics like total demand distortion (TDD) and total harmonic distortion (THD) are typically demonstrated by measuring the magnitude and phase angle of the harmonic currents and voltages. According to reports, the charger circuit’s inductance directly affects the third harmonic’s size and contribution to the current’s harmonics, accounting for about 50% of the total [68,104]. Both the TDD and THD characteristics must be kept within the IEC 61,000 (5% and 3%) and IEEE 519 (5% and 5%) standards when V2G is being planned. TDD considers the line’s fundamental current to determine the total harmonic level, whereas THD considers the line’s highest current. TDD evaluates the harmonic profile more accurately than THD claims [155,156]. To successfully regulate the voltage and current levels on the power grid together to the battery adjacent during V2G admission, a nine-phase converter with three isolated neutral-based nine-phase EVs along with an onboard battery charger (OBC) was integrated with a fuzzy logic-based voltage-oriented control (VOC) algorithm in [157]. Both the ripple pressures on the battery pack and the THD from the power grid characteristics are significantly reduced by these combinations.

The infamous fifth harmonics for permanent magnet synchronous machines (PMSMs) can be eliminated by employing six-phase windings stacked in two three-phase slots [158,159,160]. Researchers now remove or reduce the third, fifth, other odd-space harmonics, and all higher-order harmonics by waiving specific winding configurations, pole numbers, slots, and fractional slot/phase arrangements. EVs with PMSMs, synchronous wound field machines (SWFMs), and synchronous reluctance machines (SRMs) may adopt this fractional slot-per-phase technique.

6.3. V2G Load Dispatch

The power factor, reactive power, real power, and harmonic components are all impacted by the arbitrary and unplanned addition of V2G. Therefore, optimizing integrated EVs and power distribution in the V2G network is required, and [12,104] revealed that using a fast-charging EV infrastructure decreases the power grid’s steady-state voltage stability. For V2G to configure the EV fleet and acquire data on the distribution grid’s excess load demand, effective real-time communication and smart energy metering are necessary.

Accurately forecasting the EVs’ schedulable capacity to improve economics is crucial. The peak load is reduced by over 30% thanks to a revolutionary rolling prediction-decision framework proposed in [161] that uses deep long short-term memory (LSTM) techniques. The tolerance for the grid power level was raised by more than 35% in a random charging situation, enabling the V2G system to be more flexible and commercially viable. Additionally, a coordination model may be sent out during the V2G/G2V implementation to resourcefully regulate the onboard BESS to support load leveling throughout the charging/discharging time.

The centralized or decentralized control is measured with either passive or active management in a V2G operation. In a centralized control strategy, an aggregator operator (AO) becomes responsible for gathering information from the network-connected EVs and sending out the necessary control signals to control the bidirectional power flow between the UG and EV. The AO arranges all linked EVs by load generation and demand. It optimizes energy loading and unloading by the EVs’ battery capacities and charge/discharge schedule [162,163]. Decentralized control also incorporates external information on the power distribution, energy cost, and cooperation of control with nearby EV units. Two of the most popular decentralized control systems include the droop control system and the optimized control system.

The EV network may be planned to use V2G power transfer during peak hours, depending on the connected and anticipated loads. Overvoltage and fluctuating voltage over the electricity transmission line are caused by the enormous electrical power supply to the grid. To deliver stabilized grid voltage and current phase sequence and frequency, an effective power-controlling device and stabilizing voltage system may be integrated. When the grid is harmed by under-voltage, short circuits, lightning discharge, or extremely low- or high-power factors, the EV must be adequately protected through protective devices. The charging stations’ energy management unit (EMU), which comprises multiport power conversion units, may communicate the appropriate energy transfer times within the EV and grid to stabilize the electrical grid’s parameters [2,104].

6.4. Communication Systems

It is necessary to convey information between the charging infrastructure, EV supply equipment, power grid, and end users to reap economic benefits from dynamic charging and discharging in a vehicle-to-grid environment. Unlike other systems, the V2G network’s information transmission directly affects the control scheme and scheduling of the physical equipment that makes up the power grid. As a result, any break anywhere in the layer could harm the infrastructure for supplying power and add to the system’s losses. The key protocols for quick and secure communication in changing vehicle contexts are IEEE 1609 and IEEE 802.11p [164]. For V2G, V2V, and V2I systems, a dedicated short-range communication (DSRC) protocol may be used. At high vehicle speeds (>500 km/h), even with non-line-of-sight communication, DSRC in V2G could maintain quick network acquisition, signal authentication, and successful data transfer across the V2G entity [165,166,167]. Additionally, DSRC is a very dependable protocol for V2G realization due to its resistance to interoperability with low latency and in adverse weather conditions.

6.5. Cyber Vulnerabilities

The V2G system must be protected against cyber-attacks and IoT, AI, and blockchain connectivity dangers. To secure the privacy of user data, charging and discharging procedures, data on linked and in-use services, and other things, a relationship between EVs and EVCSs must be maintained. One of the most common ways to address cyber-security issues, particularly network impersonation and redirection threats, is to deploy a mutual, reciprocal authentication approach. Before beginning the charging/discharging maneuver, the EVs connected to the aggregator must be authenticated and their validity verified. Secure user key-exchange authentication (SUKA) methods could be integrated using physical unclonable functions (PUFs) [168,169,170]. Using this framework, the location of users and information about their vehicles is coded to mask their identities and prevent identity theft. Unique secret identity keys blocking potential malicious data flow throughout the network could be incorporated into the EVs’ and aggregators’ design. In addition to reducing communication overhead and enhancing effective energy management, the present development of IoT, AI, blockchain, and cryptography procedures may also be lightweight. Using mixed-integer linear programming protocols correctly could prevent the occurrence of cyber worms and viruses [171,172]. Worms could infect one EV unit and spread to other EVCSs. The spread of the worm over the network may be counted using a danger level model, and the detection of hostile variables could follow using a defense mechanism.

7. Conclusions

This assessment describes grid (V2G) technology’s present situation and the potential future for vehicles [173,174]. Studying the literature’s studies, papers, and theoretical presentations, the technical issues were presented, organized, and described with possible answers. A quick introduction to the current EV culture, the V2G trend, and different strategies and steps for an effective V2G installation for stakeholders and investors open the work. The fundamental facts about EVs and the related infrastructure are then updated. An introduction of the V2G technique is next made, and then the effects of V2G infrastructures are discussed. The difficulties of V2G application and their potential remedies are outlined. The analysis revealed that even while the V2G industry is still expanding, it shows excellent potential for grid modernization, including integrating distributed RESs in the future. Furthermore, V2G may assist both owners and power vendors through effective net energy metering policies. It was also discovered that the development of a proper V2G model is lacking in the current literature. While the battery density needs to be further improved, the cost of EVs per unit must first be decreased. To increase the system’s economics while protecting the EV battery’s lifespan, the authors conclude that the next investigation should concentrate on an effective V2G commercial model and good EMS among the batteries and grid. The following things were noticed during the investigation of the application of the V2G system, which should be addressed in future work:

• The current explosive growth of EVs presents a huge opportunity to rationalize V2G technology.
• The battery life lifecycle is one of the most significant implementation issues for V2G. Increased battery charging/discharging cycles can potentially cause early battery deterioration and lower the range of an EV.
• Power loss in the early stages of power electronics and accompanying harmonics could affect the grid’s stability and require correct control.
• The promise of V2G includes auxiliary services such as frequency fluctuation reduction, reactive power flow regulation, load shaving, and system voltage.
• To ensure that the existing electrical grid, related electrical equipment, and control strategies can endure significant EV penetration, they must be changed.
• V2G is currently too new to be marketed. Additionally, the V2G scheme lacks an appropriate business model for commercialization.
• To benefit from bidirectional power flow, countries have already started modifying the standards for EV chargers. In addition, primary EV production facilities have merged beyond the border to launch appropriate business strategies and technological advancement for V2G installation.