A Review on Electric Vehicles

This article is discussing possibilities and challenges with electric vehicle from an electric power engineering perspective.

The report is written by Hafeez Abolade Omosanya, research assistant with UiT, summer 2019.

Abstract

Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more prominent in the transport sector worldwide. If this trend continuous, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent and noticeable in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities and challenges with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept that we so much envisaged.

There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major hindrances for EVs to overcome before totally replacing ICE vehicles. Hence, this article is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this regard as well as present and likely challenges in it usage.

Introduction

Increment in carbon dioxide emissions [1] and their effects are pushing the use of more environmentally friendly energy sources [2]. Electric Vehicles (EVs) could play a significant role in reaching the targeted goals of reducing dependence on conventional sources of energy, however the penetration of EVs in the market has multiple concerns of fulfillment of their charging needs in various traveling scenarios. Many factors are responsible for the postponing of the sudden increase in number of EVs on the road, for instance, the limited range of EVs [3], long charging durations, less frequent availability of charging facilities, high initial investment cost etc. Yet as predicted [4], if the penetration of EVs in the near future is suddenly increased, it would pose some issues related to the load flows and power quality in the power distribution networks.

Considering the effects of EV charging systems in distribution networks beforehand, would help avoid any issues for future distribution systems. Charging requirements for EVs vary with the nature of the EV trips, for instance, short trips would require less energy from the EV’s battery and hence it would not lead the EV battery to discharge at a critical level. This small portion of consumed energy from the EV battery could be recharged while it is parked at shopping malls, offices, or at all possible parking locations and at home over the night. As for short trips only a small percentage of the stored energy in the battery is consumed so it is feasible to even postpone the charging to some other time and charge it at low charging power.

However, in case of long trips more battery energy is being consumed so the quick charging of EVs is needed to complete the trip in a reasonable period of time. The fast charging of EVs demands high power to be drawn from the network for relatively shorter periods of time which gives rise to network capacity issues because of the simultaneous fast charging events. Many research articles [5-6] have focused on the rescheduling of EV charging at home for the cost-effective charging solution for EVs for daily charging.

Analysis of reactive power in distribution system due charging stations is studied in [7]. Short circuit and protection aspects of fast charging stations are discussed in [8]. In [9], an estimate of required number of fast charging sockets in a particular highway case is done based on different situations of waiting times of EVs at the charging stations. Ref. [10] studies the utilization of the charging infrastructure developed in [9] from charging stations owner’s perception.

Charging needs of EVs on highways and on sea are more critical both in terms of network capacity and charging interval. Fast charging of EVs on highways is inevitable due to limited range and battery capacities. It is essential to develop the fast charging infrastructure for EVs on highways with the proportional penetration of EVs to avert long queuing at the charging stations along the sea. Therefore, the objective of this article is to study the peak power issues due to fast charging of EVs in distribution network considering different penetration levels of EVs and various scenarios of allowable waiting times. This paper studies the peak charging load demand on the power distribution network for the charging infrastructure model developed in [9] with the several scenarios of queuing times and penetration levels of EVs.

Electric vehicles

EVs can be considered as a combination of different subsystems that are coordinated to achieve self-sufficient operation. Each of these systems interact with each other to make the EV work, and there are multiple technologies that can be employed to operate the subsystems. In Figure 1, key parts of these subsystems and their contribution to the total system is demonstrated. Some of these parts have to work extensively with some of the others, whereas some have to interact very less. Whatever the case may be, it is the combined work of all these systems that make an EV operate. There are quite a few configurations and options to build an EV with. EVs can be exclusively driven with stored electrical power, some can generate this energy from an ICE, and there are also some vehicles that employ both the ICE and the electrical motors together.

Figure 1 – Major EV system and interactions [10]

EV configurations

An electric vehicle, unlike its ICE counterparts, is quite flexible [10]. This is because of the absence of intricate mechanical arrangements that are required to run a conventional vehicle. In an EV, there is only one moving part, the motor. It can be controlled by different control arrangements and techniques. The motor needs a power supply to run which can be from an array of sources. These two components can be placed at different locations on the vehicle and as long as they are connected through electrical wires, the vehicle will work. Then again, an EV can run solely on electricity, but an ICE and electric motor can also work in conjunction to turn the wheels. Because of such flexibility, different configurations emerged which are adopted according to the type of vehicle. An EV can be regarded as a system incorporating three different subsystems [10]: energy source, propulsion and auxiliary. The energy source subsystem includes the source, its refueling system and energy management system. The propulsion subsystem has the electric motor, power converter, controller, transmission and the driving wheels as its components. The auxiliary subsystem is comprised of auxiliary power supply, temperature control system and the power steering unit. These subsystems are shown in Figure 2.

Figure 2 – EV configurations [10]

The arrows in Figure 2 indicates the flow of the entities in question. A backward flow of power can be created by regenerative actions like regenerative braking. The energy source has to be receptive to store the energy sent back by regenerative actions. Most of the EV batteries along with capacitors/flywheels (CFs) are compatible with such energy regeneration techniques [10].

Effect of EV’s on the power grid

Vehicles may serve the purpose of transportation, but they affect a lot of other areas. Therefore, the shift in the vehicle world created by EVs impacts the environment, the economy, and being electric, the electrical systems to a great extent. EVs are gaining popularity because of the benefits they provide in all these areas, but with them, there come some difficulties as well. Figure 3 illustrates the impacts of EVs on the power grid, environment and economy.

Figure 3 – Impact from EV’s on power grid, environment and economy

Negative impacts

EVs are considered to be high power loads [11] and they affect the power distribution system directly. The distribution transformers, cables and fuses are affected the most [12,13]. Nissan Leaf with a 24kWh battery pack can consume power similar to a single European household. A 3.3 kW charger in a 220V, 15A system can raise the current demand by 17% to 25% [14]. The situation gets quite distressing if charging is done during peak hours, leading to overload on the system, damage of the system equipment, tripping of protection relays, and consequently, an increase in the infrastructure cost [14]. Charging without any concern to the time when drawing power from the grid is denoted as uncoordinated charging, uncontrolled charging or dumb charging [14,15]. This can lead to the addition of EV load in peak hours which can cause load unbalance, shortage of energy, instability, and decrease in reliability and degradation of power quality [13,16]. In case of the modified IEEE 23kV distribution system, penetration of EVs can deviate voltage below the 0.9p.u. level up to 0.83p.u, with increased power losses and generation cost [15]. Level 1 charging from 110V outlet does not affect the power system much, but problems arise as the charging voltage increases. Adding an EV for fast charging can be equivalent to adding numerous households to the grid. The grid is likely to be capable of withstanding it, but distribution networks are designed with specific numbers of households kept into mind, sudden addition of such huge loads can often lead to problems. Reducing the charging time to distinguish their vehicles in the EV market has become the current norm among the manufacturers, and it requires higher voltages than ever. Therefore, mitigating the adverse effects is not likely by employing low charging voltages.

To avoid these effects, and to provide efficient charging with the available infrastructure, coordinated charging (also called controlled or smart charging) has to be adopted. In this scheme, the EVs are charged during the time periods when the demand is low, for example, after midnight. Such schemes are beneficial in a lot of ways. It not only prevents addition of extra load during peak hours, but also increases the load in valley areas of the load curve, facilitating proper use of the power plants with better efficiency. In [13], Richardson et al., showed that a controlled charging rate can make high EV penetration possible in the current residential power network with only a few upgrades in the infrastructure. Geng et al., proposed a charging strategy in [17] comprising of two stages aimed at providing satisfactory charging for all connected EVs while shifting the loads on the transformers. On the consumer side, it can reduce the electricity bill as the electricity is consumed by the EVs during off peak hours, which generally have a cheaper unit rate than peak hours. According to [18], smart charging systems can reduce the increase investment cost in distribution system by 60–70%. The major problems that are faced in the power systems because of EVs can be charted as described in the following sections.

Voltage instability

Power systems are normally operated close to their stability limit. Voltage instabilities in such systems can occur because of load characteristics, and that instability can lead to blackouts. EV loads have nonlinear characteristics, which are different than the general industrial or domestic loads, and it draw large quantities power in a short time period [23,19]. Reference [20] gives support to the fact that EVs cause serious voltage imbalance in power systems. If the EVs have constant impedance load characteristics, then it is possible for the grid to support a lot of vehicles without facing any instability [23]. However, the EV loads cannot be assumed beforehand and thus their power consumptions remain erratic; addition of lots of EVs at a time can lead to violation of distribution constraints. To anticipate these loads properly, appropriate modeling methods are required. Reference [21] suggested tackling the instabilities by damping the oscillations caused by charging and discharging of EV batteries using a wide area control method. The situation can also be handled by changing the tap settings of transformers [22], by a properly planned charging system, and by using control systems like fuzzy logic controllers to calculate voltages and SOCs of batteries [23].

Voltage Sag

A decrease in the RMS value of voltage for half a cycle or 1 min is referred to as voltage sag. It is caused by overloading or inrush currents during start of electric machines. Simulation modeled with an EV charger and a power converter in [24] stated 20% EV penetration can exceed the voltage sag limit. Reference [25] stated that 60% EV penetration is possible without any negative impact if controlled charging is employed. The amount, however, falls to 10% in case of uncontrolled charging. Leemput et al., conducted a test employing voltage droop charging and peak shaving by EV charging [26]. This study revealed considerable reduction in voltage sag with application of voltage droop charging. Application of smart grid can help in great extents in mitigating the sag [27].

Overloading of Transformers

EV charging directly affects the distribution transformers [23]. The extra heat dissipated by EV loads can lead to increased aging rate of the transformers, but it also depends on the ambient temperature. In places with generally cold weather like Vermont, the aging due to temperature is insignificant [23]. Estimation of the lifetime of a transformer is done in [29], where factors taken into consideration are the rate of EV penetration, starting time of charging and the ambient temperature. It is stated that transformers can withstand 10% EV penetration without getting any decrease in lifetime. The effect of level 1 charging has insignificant effect on this lifetime, but significant increase in level 2 charging can lead to the failure of transformers [30]. Elnozahy et al., stated that overloading of transformer can happen with 20% PHEV penetration for level 1 charging, whereas level 2 does it with 10% penetration [31]. According to [32], charging that takes place right after an EV being plugged in can be damaging to the transformers.

Power Quality Degradation

The increased amount of harmonics and imbalance in voltage will reduce the power quality in case of massive scale EV penetration to the grid.

Positive Impacts

On the plus side, EVs can prove to be quite useful to the power systems in a number of ways

Smart Grid

In the smart grid system, intelligent communication and decision making is merged with the grid architecture. Smart grid is highly regarded as the future of power grids and offers a vast array of advantages to offer dependable power supply and advanced control. In such a system, the previous discussed coordinated charging is easily achievable, including the interaction with the end users. The interaction of EVs and smart grid can facilitate and ease opportunities like V2G and better integration of renewable energy. In fact, EV is one the eight priorities listed to create an efficient smart grid [28]

V2G

V2G or vehicle to grid is a method where the EV can provide power to the grid. In this system, the vehicles act as loads when they are drawing energy, and then can become dynamic energy storage by feeding energy back to the grid. In coordinated charging, the EV loads are applied in the valley points of the load curve. In V2G, EVs can act as power sources to provide during peak hours. V2G is attainable with the smart grid system. By making use of the functionalities of smart grid, EVs can be used as dynamic loads or dynamic storage systems. The power flow in this system can be unidirectional or bidirectional. The unidirectional system is synonymous to the coordinated charging scheme, the vehicles are charged when the load is low, but the time to charge the vehicles is automatically decided by the system. Vehicles using this scheme can simply be plugged in anytime and put there; the system will choose an appropriate time and charge it. Smart meters are required for enabling this system. With a driver variable charging scheme, the peak power demand can be reduced by 56% [33]. Sortomme et al., found this system particularly attractive as it required little up gradation of the existing infrastructure; creating a communication system in-between the grid and the EVs is all that is required [34]. The bidirectional system allows vehicles to provide power back to the grid. In this scenario, vehicles using this scheme will supply energy to the grid from their storage when it is needed. This method has several interesting aspects. With ever increasing integration of renewable energy sources (RES) to the grid, energy storages are becoming indispensable to overcome their intermittency, but the storages have a very high price. EVs have energy storages, and in many cases, they are not used for a long period. Example for this point can be the cars in the parking lots of an office block, where they stay unused till the office hour is over, or vehicles that are used in a specific period of the year, like a beach buggy. Studies also revealed that; vehicles stay parked 95% of the time [28]. These potential storages can be used when there is excess generation or low demand and when the energy is needed, it is taken back to the grid. The vehicle owners can also get economically beneficial by selling this energy to the grid. In [35], Clement-Nyns et al., resolved that a combination of PHEVs can prove beneficial to distributed generation sources by providing storage for the excess generation, and releasing that to the grid later. Bidirectional charging, however, needs chargers capable of providing power flow in both directions. It also needs smart meters to keep track of the units consumed and sold, and advanced metering architecture (AMI) to learn about the unit charges in real time to get actual cost associated with the charging or discharging at the exact time of the day. The AMI system can shift 54% of the demand to off-peak periods and can reduce peak consumption by 36% [33]. The bidirectional system, in fact, can provide 12.3% more annual revenue than the unidirectional one. But taking the metering and protections systems required in the bidirectional method, this revenue is annulled and indicates the unidirectional system is more practical. Frequent charging and discharging caused by bidirectional charging can also reduce battery life and increase energy losses from the conversion processes [81,28]. In a V2G scenario, operators with a vehicle fleet are likely to reduce their cost of operation by 26.5% [28]. Another concept is produced using the smart grid and the EVs, called virtual power plant (VPP), where a cluster of vehicles is considered as a power plant and dealt like one in the system. VPP architecture and control is shown in Figure 4.

Figure 4 – Virtual power plant architecture and control [25]

Integration of renewable energy sources

Renewable energy usage becomes more promising with EVs integrated into the picture. EV owners can use RES to generate power locally to charge their EVs. Parking lot roofs have high potential for the placement of PV panels which can charge the vehicles parked underneath as well as supplying the grid in case of excess generation [36,37], thus serving the increase of commercial RES deployment. The V2G structure is further helpful to integrate RES for charging of EVs, and to the grid as well, as it enables the selling of energy to the grid when there is surplus, for example, when vehicles are parked and the system knows the user will not need the vehicle before a certain time. V2G can also enable increased penetration of wind energy (41%–59%) in the grid in an isolated system [29]. References [38,39] worked with different architectures to observe the integration scenario of wind energy with EV assistance. Figure 5 demonstrates integration of wind and solar farm with conventional coal and nuclear power grid with EV charging station employing bidirectional V2G. Table 27 shows the types of assistance EVs can provide for integrating renewable energy sources to the grid.

Figure 5 – Wind and solar integration into the grid

Impact on the environment

One of the main factors that drives the increase of development and use of EVs’, is their contribution to reduce the greenhouse gas (GHG) emissions. Conventional internal combustion engine (ICE) vehicles burn fuels directly and thus produce harmful gases, including carbon dioxide and carbon monoxide. Though HEVs and PHEVs have IC engines, their emissions are less than the conventional vehicles. But there are also theories that the electrical energy consumed by the EVs can give rise to GHG emission from the power plants which have to produce more because of the extra load added in form of EVs. This theory can be justified by the fact that the peak load power plants are likely to be ICE type or can use gas or coal for power generation. If EVs add excess load during peak hours, it will lead to the operation of such plants and will give rise to CO2 emission [40]. Reference [41] also stated that power generation from coal and natural gas will produce more CO2 from EV penetration than ICEs. However, all the power is not generated from such resources. There are many other power generating technologies that produce less GHG. With those considered, the GHG production from power plants because of EV penetration is less than the amount produced by equivalent power generation from ICE vehicles. The power plants also produce energy in bulk, thus minimizing the per unit emission. With renewable sources integrated properly, which the EVs can support strongly, the emission from both power generation and transportation sector can be reduced [23]. Over time, EVs cause less emission than conventional vehicles. This parameter can be denoted as well-to-wheel emission and it has a lower value for EVs [42]. In [43], well-to-wheel and production phases are taken into account to calculate the impact of EVs on the environment. This approach stated the EVs to be the least carbon intensive among the vehicles. Denmark managed to reduce 85% CO2 emission from transportation by combining EVs and electric power. EVs also produce far less noise, which can highly reduce sound pollution, mostly in urban areas. The recycling of the batteries raises serious concerns though, as there are few organizations capable of recycling the lithium-ion batteries fully. However, like the previous nickel-metal and lead-acid ones, lithium-ion cells are not made of caustic chemicals, and their reuse can reduce ‘peak lithium’ or ‘peak oil’ demands [44].

Barriers to EV adoption

Although electric vehicles offer a lot of promises, they are still not widely adopted, and the reasons behind that are quite serious as well. Temperature adaptability and long service life

Technological Problems

The main obstacles that have frustrated EVs’ domination are the drawbacks of the related technology. Batteries are the main area of concern as their contribution to the weight of the boat is significant. Range and charging period also depend on the battery. These factors, along with a few others, are demonstrated below:

Limited Range

EVs are held back by the capacity of their batteries [45]. They have a certain amount of energy stored there, and can travel a distance that the stored energy allows. The range also depends on the speed of the vehicle, driving style, cargo the vehicle is carrying, the terrain it is being driven on, and the energy consuming services running in the boat, for example air conditioning. This causes ‘range anxiety’ among the users [44], which indicates the concern about finding a charging station before the battery drains out.

Long Charging Period

Another major disadvantage of EVs is the long time they need to get charged. Depending on the type of charger and battery pack, charging can take from a few minutes to hours. This truly makes EVs incompetent against the ICE vehicles and boats which only take a few minutes to get refueled. Hidrue et al., found out that to have an hour decreased from the charging time, people are willing to pay $425–$3250 [46]. A way to make the charging time faster is to increase the voltage level and employment of better chargers. Some fast charging facilities are available at present, and more are being studied. There are also the fuel cell vehicles that do not require charging like other EVs. Filling up the hydrogen tank is all that has to be done in case of these vehicles, which is as convenient as filling up a fuel tank, but FCVs need sufficient hydrogen refueling stations and a feasible way to produce the hydrogen in order to thrive.

Social Problems

Social Acceptance

The acceptance of a new and immature technology, along with its consequences, takes some time in the society as it means change of certain habits [47]. Using an EV instead of a conventional vehicle means change of driving patters, refueling habits, preparedness to use an alternative transport in case of low battery, and these are not easy to adopt.

Insufficient Charging Stations

Though public charging stations have increased a lot in number, still they are not enough. Coupled with the lengthy charging time, this acts as a major deterrent against EV penetration. Not all the public charging stations are compatible with every car as well; therefore, it also becomes a challenge to find a proper charging point when it is required to replete the battery. There is also the risk of getting a fully occupied charging station with no room for another car. But, the manufacturers are working on to mitigate this problem. Tesla and Nissan have been expanding their own charging networks, as it, in turn means they can sell more of their EVs. Hydrogen refueling stations are not abundant yet as well. It is necessary as well to increase the adoption of FCVs. In [48], a placement strategy for hydrogen refueling stations in California is discussed. It stated that a total of sixty-eight such stations will be sufficient to provide service to FCVs in the area. To get the better out of the remaining stations, there are different trip planning applications, both web-based and manufacturer provided, which helps to obtain a route so that there are enough charging facilities to reach the destination.

Economic Problems

High Price

The price of the EVs is quite high compared to their ICE counterparts. This is because of the high cost of batteries [44] and fuel cells. To make people overlook this factor, governments in different countries including Norway, UK and Germany, have provided incentives and tax breaks which provide the buyers of EVs with subsidies. Mass production and technological advancements will lead to a decrease in the prices of batteries as well as fuel cells. Affordable EVs with a long range like the Chevrolet Bolt has already appeared in the market, while another vehicle with the same promises (the Tesla Model 3) is anticipated to arrive soon. Figure 6 shows the limitations of EVs in the three sectors. Table 1 suggests some solutions for the existing limitations in key factors, while Table 2 demonstrates the drawbacks in key components.

Figure 6 – Social, technological and economic problems faced by EVs.

Table 1 – EV limitations and possible solutions

LimitationProbable solution
Limited rangeImproved energy source and energy
management technology
Long charging periodImproved charging technology
Safety problemsAdvanced manufacturing
scheme and build quality
Insufficient charging stationsPlacement of sufficient stations capable of providing services to all kinds of vehicles
High priceMass production, advanced technology, government incentives

Table 2 – Drawback of key elements

FactorHurdles
RechargingWeight of charger, durability, cost, recycling, size, charging time
Hybrid EVBattery, durability, weight, cost
Hydrogen fuel cellCost, hydrogen production, infrastructure, storage, durability, reliability
Auxiliary power unitSize, cost, weight, durability, safety, reliability, cooling, efficiency

Optimization techniques

To make the best out of the available energy, EVs apply various aerodynamics and mass reduction techniques, lightweight materials are used to decrease the body weight as well. Regenerative braking is used to restore energy lost in braking. The restored energy can be stored in different ways. It can be stored directly in the ESS, or it can be stored by compressing air by means of hydraulic motor, springs can also be employed to store this energy in form of gravitational energy [49].

Conclusion

EVs have great potential of becoming the future of transport, while saving this planet from imminent calamities caused by global warming. They are a viable alternative to conventional vehicles that depend directly on the diminishing fossil fuel reserves. The EV types, configurations, energy sources, motors, power conversion and charging technologies for EVs have been discussed in detail in this paper. The key technologies of each section have been reviewed and their characteristics have been presented. The impacts EVs cause in different sectors have been discussed as well, along with the huge possibilities they hold to promote a better and greener energy system by collaborating with smart grid and facilitating the integration of renewable sources. Limitations of current EVs have been listed along with probable solutions to overcome these shortcomings. The current optimization techniques and control algorithms have also been included. A brief overview of the current EV market has been presented. Finally, trends and ways of future developments have been assessed followed by the outcomes of this paper to summarize the whole text, providing a clear picture of this sector and the areas in need of further research.

References

  1. Shea, “Emission reduction,” IEEE Power Energy Mag., vol. 6, no.1, pp. 96–98, Jan.–Feb. 2008.
  2. S. Department of Energy, Plug-in Electric Vehicle Handbook for Public Charging Station Host, Apr. 2012.
  3. J. Perez-Pinal, N. Al-Mutawaly, and J. C. Nunez-Perez, “Impact of Plug-in Hybrid Electric Vehicle in distributed generation and smart grid: A brief review,” (2013) International Review on Modelling and Simulations (IREMOS), 6 (3), pp. 795–805.
  4. S. Department of Energy, One Million Electric Vehicles by 2015, Feb. 2012.
  5. H. Malik, M. Ali, and M. Lehtonen, “Collaborative demand response optimization of electric vehicles and storage space heating for residential peak shaving,” International Review of Electrical Engineering (IREE), vol. 9, no. 6, 2014.
  6. H. Malik, M. Ali, and M. Lehtonen, “Intelligent agent-based architecture for demand side management considering space heating and electric vehicle load,” Engineering, 2014, 6, pp. 670–679.
  7. Cuifen, G. Wensheng, L. Jing, and L. Hua, “Analyzing the impact of electric vehicles on distribution networks,” in Proc. IEEE PES Innovative Smart Grid Tech. (ISGT), 2012, pp. 1–8.
  8. Etezadi-Amoli, K. Choma, and J. Stefani, “Rapid-charge electric vehicle stations,” IEEE Trans. Power Del., vol. 25, no. 3, pp. 1883– 1887, Jul. 2010.
  9. H. Malik, M. Lehtonen, E. Saarijärvi, and A. Safdarian, “A feasibility study of fast charging infrastructure for EVs on highways,” International Review of Electrical Engineering (IREE), vol. 9, no. 2, 2014.
  10. Chan, C.C. The state of the art of electric and hybrid vehicles. IEEE 2002, 90, 247–275. [CrossRef]
  11. Yao, L.; Lim, W.H.; Tsai, T.S. A Real-Time Charging Scheme for Demand Response in Electric Vehicle Parking Station. IEEE Trans. Smart Grid 2017, 8, 52–62. [CrossRef]
  12. Kütt, L.; Saarijärvi, E.; Lehtonen, M.; Mõlder, H.; Niitsoo, J. A review of the harmonic and unbalance effects in electrical distribution networks due to EV charging. In Proceedings of the 2013 12th International Conference on Environment and Electrical Engineering (EEEIC), Wroclaw, Poland, 5–8 May 2013.
  13. Richardson, P.; Flynn, D.; Keane, A. Optimal charging of electric vehicles in low-voltage distribution systems. IEEE Trans. Power Syst. 2012, 27, 268–279. [CrossRef]
  14. Mwasilu, F.; Justo, J.J.; Kim, E.K.; Do, T.D.; Jung, J.W. Electric vehicles and smart grid interaction: A review on vehicle to grid and renewable energy sources integration. Sustain. Energy Rev. 2014, 34, 501–516. [CrossRef]
  15. Green, R.C.; Wang, L.; Alam, M. The impact of plug-in hybrid electric vehicles on distribution networks: A review and outlook. Sustain. Energy Rev. 2011, 15, 544–553. [CrossRef]
  16. Qian, K.; Zhou, C.; Allan, M.; Yuan, Y. Modeling of load demand due to EV battery charging in distribution systems. IEEE Trans. Power Syst. 2011, 26, 802–810. [CrossRef]
  17. Yao, L.; Lim, W.H.; Tsai, T.S. A Real-Time Charging Scheme for Demand Response in Electric Vehicle Parking Station. IEEE Trans. Smart Grid 2017, 8, 52–62. [CrossRef]
  18. Kütt, L.; Saarijärvi, E.; Lehtonen, M.; Mõlder, H.; Niitsoo, J. A review of the harmonic and unbalance effects in electrical distribution networks due to EV charging. In Proceedings of the 2013 12th International Conference on Environment and Electrical Engineering (EEEIC), Wroclaw, Poland, 5–8 May 2013.
  19. Richardson, P.; Flynn, D.; Keane, A. Optimal charging of electric vehicles in low-voltage distribution systems. IEEE Trans. Power Syst. 2012, 27, 268–279. [CrossRef]
  20. Mwasilu, F.; Justo, J.J.; Kim, E.K.; Do, T.D.; Jung, J.W. Electric vehicles and smart grid interaction: A review on vehicle to grid and renewable energy sources integration. Sustain. Energy Rev. 2014, 34, 501–516. [CrossRef]
  21. Green, R.C.; Wang, L.; Alam, M. The impact of plug-in hybrid electric vehicles on distribution networks: A review and outlook. Sustain. Energy Rev. 2011, 15, 544–553. [CrossRef]
  22. Qian, K.; Zhou, C.; Allan, M.; Yuan, Y. Modeling of load demand due to EV battery charging in distribution systems. IEEE Trans. Power Syst. 2011, 26, 802–810. [CrossRef]
  23. Shareef, H.; Islam, M.M.; Mohamed, A. A review of the stage-of-the-art charging technologies, placement methodologies, and impacts of electric vehicles. Sustain. Energy Rev. 2016, 64, 403–420. [CrossRef]
  24. Lee, S.J.; Kim, J.H.; Kim, D.U.; Go, H.S.; Kim, C.H.; Kim, E.S.; Kim, S.K. Evaluation of voltage sag and unbalance due to the system connection of electric vehicles on distribution system. Electr. Eng. Technol. 2014, 9, 452–460. [CrossRef]
  25. Tie, C.H.; Gan, C.K.; Ibrahim, K.A. The impact of electric vehicle charging on a residential low voltage distribution network in Malaysia. In Proceedings of the 2014 IEEE Innovative Smart Grid Technologies—Asia (ISGT Asia), Kuala Lumpur, Malaysia, 20–23 May 2014; pp. 272–277.
  26. Leemput, N.; Geth, F.; Van Roy, J.; Delnooz, A.; Buscher, J.; Driesen, J. Impact of electric vehicle on board single-phase charging strategies on a Flemish residential grid. IEEE Trans. Smart Grid 2014, 5, 1815–1822. [CrossRef]
  27. Masoum, M.A.S.; Moses, P.S.; Deilami, S. Load management in smart grids considering harmonic distortion and transformer derating. In Proceedings of the IEEE Innovative Smart Grid Technologies Europe (ISGT Europe), Gaithersburg, MD, USA, 19–21 January 2010; pp. 1–7.
  28. Mwasilu, F.; Justo, J.J.; Kim, E.K.; Do, T.D.; Jung, J.W. Electric vehicles and smart grid interaction: A review on vehicle to grid and renewable energy sources integration. Sustain. Energy Rev. 2014, 34, 501–516. [CrossRef]
  29. Qian, K.; Zhou, C.; Yuan, Y. Impacts of high penetration level of fully electric vehicles charging loads on the thermal ageing of power transformers. J. Electr. Power Energy Syst. 2015, 65, 102–112. [CrossRef]
  30. Razeghi, G.; Zhang, L.; Brown, T.; Samuelsen, S. Impacts of plug-in hybrid electric vehicles on a residential transformer using stochastic and empirical analysis. Power Sources 2014, 252, 277–285. [CrossRef]
  31. Elnozahy, M.S.; Salama, M.M. A comprehensive study of the impacts of PHEVs on residential distribution networks. IEEE Trans. Sustain. Energy 2014, 5, 332–342. [CrossRef]
  32. Gómez, J.C.; Morcos, M.M. Impact of EV battery chargers on the power quality of distribution systems. IEEE Trans. Power Deliv. 2003, 18, 975–981. [CrossRef]
  33. Richardson, P.; Flynn, D.; Keane, A. Optimal charging of electric vehicles in low-voltage distribution systems. IEEE Trans. Power Syst. 2012, 27, 268–279. [CrossRef]
  34. Sortomme, E.; El-Sharkawi, M.A. Optimal charging strategies for unidirectional vehicle-to-grid. IEEE Trans. Smart Grid 2011, 2, 131–138. [CrossRef]
  35. Clement-Nyns, K.; Haesen, E.; Driesen, J. The impact of vehicle-to-grid on the distribution grid. Power Syst. Res. 2011, 81, 185–192. [CrossRef]
  36. Tulpule, P.; Marano, V.; Yurkovich, S.; Rizzoni, G. Economic and environmental impacts of a PV powered workplace parking garage charging station. Energy 2013, 108, 323–332. [CrossRef]
  37. Derakhshandeh, S.Y.; Masoum, A.S.; Deilami, S.; Masoum, M.A.; Golshan, M.H. Coordination of generation scheduling with PEVs charging in industrial microgrids. IEEE Trans. Power Syst. 2013, 28, 3451–3461. [CrossRef]
  38. Pillai, R.J.; Heussen, K.; Østergaard, P.A. Comparative analysis of hourly and dynamic power balancing models for validating future energy scenarios. Energy 2011, 36, 3233–3243. [CrossRef]
  39. Liu, C.; Wang, J.; Botterud, A.; Zhou, Y.; Vyas, A. Assessment of impacts of PHEV charging patterns on wind-thermal scheduling by stochastic unit commitment. IEEE Trans. Smart Grid 2012, 3, 675–683. [CrossRef]
  40. Ma, H.; Balthser, F.; Tait, N.; Riera-Palou, X.; Harrison, A. A new comparison between the life cycle greenhouse gas emissions of battery electric vehicles and internal combustion vehicles. Energy Policy 2012, 44, 160–173. [CrossRef]
  41. Sioshansi, R.; Miller, J. Plug-in hybrid electric vehicles can be clean and economical in dirty power systems. Energy Policy 2011, 39, 6151–6161. [CrossRef]
  42. Donateo, T.; Ingrosso, F.; Licci, F.; Laforgia, D. A method to estimate the environmental impact of an electric city car during six months of testing in an Italian city. Power Sources 2014, 270, 487–498. [CrossRef]
  43. Onat, N.C.; Kucukvar, M.; Tatari, O. Conventional, hybrid, plug-in hybrid or electric vehicles? State-based comparative carbon and energy footprint analysis in the United States. Energy 2015, 150, 36–49. [CrossRef]
  44. Shareef, H.; Islam, M.M.; Mohamed, A. A review of the stage-of-the-art charging technologies, placement methodologies, and impacts of electric vehicles. Sustain. Energy Rev. 2016, 64, 403–420. [CrossRef]
  45. Chan, C.C. The state of the art of electric and hybrid vehicles. IEEE 2002, 90, 247–275. [CrossRef]
  46. Hidrue, M.K.; Parsons, G.R.; Kempton, W.; Gardner, M.P. Willingness to pay for electric vehicles and their attributes. Energy Econ. 2011, 33, 686–705. [CrossRef]
  47. Wolsink, M. The research agenda on social acceptance of distributed generation in smart grids: Renewable as common pool resources. Sustain. Energy Rev. 2012, 16, 822–835. [CrossRef]
  48. Kang, J.E.; Brown, T.; Recker, W.W.; Samuelsen, G.S. Refueling hydrogen fuel cell vehicles with 68 proposed refueling stations in California: Measuring deviations from daily travel patterns. J. Hydrogen Energy 2014, 39, 3444–3449. [CrossRef]
  49. Tie, S.F.; Tan, C.W. A review of energy sources and energy management system in electric vehicles. Sustain. Energy Rev. 2013, 20, 82–102. [CrossRef]

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