Electric Vehicle(EVs)Technology-A Sustainable Future

---

Electric vehicles (EVs)  firstly introduced in late 1800’s. But the benefits offered by internal  combustion engines over electric propulsion made the previous a popular  choice. Increasing price of fossil fuels coupled with environmental  concerns has increased the interest in the research and growth of  electric vehicle propulsion technologies.

India  today is one of the top ten automotive markets in the world and given  its burgeoning middle-class population with buying potential and the  steady economic growth, acerating automotive sales is expected to  continue. In the last couple of years, there has been a lot discussion  around the prices of fuel-apart from the deregulation of petrol prices.  Moreover, the treat of disruption of supplies from the Middle-East has  heightened the debate on energy security and brought the focus on  alternate drive train technologies.

                 The EVs offer several advantages compared to IC engine  vehicle Such as Zero exhaust emission, reduced noise pollution &  independence on fossil fuels which will help to reduce green gas effect  and help to maintain environment temperature that’s why Electric  vehicle (EVs) promising technology for achieving sustainable transport  sector in future.

                 This paper is intended to overview of Electrical Vehicle (EVs)  technology different types of electric-drive vehicles, energy storage  system, charging mechanisms and also shown how the Electric Vehicle is  sustainable transport technology in future.

   An electric vehicle (EV) is that uses one or more electric motors for propulsion and  operates on an electric motor, instead of an internal-combustion engine  which is operates on fossil fuel (Petrol/Diesel/CNG). The electric  Vehicle (EVs) used battery as an energy source and can charged by grid  or internal combustion engine with help of AC-DC power converter and  used this energy to running of Motors to propulsion of vehicle.

Therefore,  such as vehicle is seen as a possible replacement for  current-generation automobile, in order to address the issue of rising  pollution, global warming, depleting, greenhouse effect, reduction in  source of fossil fuels etc. Though the concept of electric vehicles has  been around for a long time, it has drawn a considerable amount of  interest in the past decade amid a rising carbon footprint and other  environmental impacts of fuel-based vehicles.Though the concept of electric vehicles has been around  for a long time (1900s), it has drawn a considerable amount of interest  in the past decade amid a rising carbon footprint and other  environmental impacts of fuel-based vehicles. 

The global market for electric  vehicles (EVs) is growing continuously at a compounded annualized growth  rate (CAGR) of 21.7 per cent. It is expected to grow from 8.1 million  units to 39.21 million units by 2030. This exponential growth is being  driven by various factors, including concerns for air & noise  pollution. Governments all over the world  are encouraging the EV industry through subsidies and regulations, and  the consumers are demanding low-emission commuting instead of the fossil  fuel-driven vehicles, which are endangering our planet. When  the first EVs were manufactured/introduced, very high initial cost, low  battery range, low speed, and much lower environmental concerns  resulted in the industry not taking off. The last 10 years though have  seen universal interest among original equipment manufacturers (OEMs),  customers, and governments, resulting in huge investments being made in  EV manufacturing and battery technology, resulting in millions of  vehicles getting sold in various countries.

               There are many reasons why people are moving to Electric  Vehicles (EV) to get them to the places they need to be. These include:

• EVs are fun to drive because they are fast and smooth.
• Reduces emissions of harmful greenhouse gases.
• EVs are innovative and cool.
• EVs are a smart and convenient choice.
• Lower Operating Cost.
• Improved noise-vibration-harshness characteristics within the vehicle.
• Convenience of home refueling.
• Reduced maintenance & improved Performance.

There are mainly 4 types of electric  vehicle: Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV),  Plugin Hybrid Electric Vehicle (PHEV) and Fuel Cell Electric Vehicle  (FCEV) and each are described in more detail below.

The  Vehicle configuration of a typical battery vehicle is elaborated here.  So, we can see that the Battery bank in BEV is normally charged direct  from grid using battery charger and the electrical energy stored in  Battery is transferred to the wheels using an electric drive consisting  of power converter and electrical machine via transmission gear and  differential. This power converter has to be designed to carry  bidirectional power flow since it can also be used to regenerative the  power coming from wheels during the braking. You can also see that the  clutch is normally not required in a battery electric vehicle as in  conventional IC engine-based vehicle.

The  Battery Electric Vehicle (BEV) uses high-capacity batteries and  electric motor for propulsion. It derives all the power from its  batteries pack and has no internal combustion engine, neither fuel cell,  nor fuel tank. The only watt to recharge its batteries is by plugging in  the vehicle to a charging point.

HEVs  are also known as series hybrid or parallel hybrid. HEVs have both  engine and electric motor. The engine gets energy from fuel, and the  motor gets electricity from batteries. The transmission is rotated  simultaneously by both engine and electric motor. This then drives the  wheels. 

                    The second type is the Hybrid Electric Vehicle (HEV)  that uses mechanically a combination of Electric Motor (EM) in low  speeds dedicated for in-city traffic and a conventional Internal  Combustion Engine (ICE) to be used outside urban areas (Fig2.b). When  ICE mode is activated, the EM stops and batteries start charging using  an alternator driven by the same equipped ICE. The HEV get an upgrade to  the Plug-in Hybrid Electric Vehicle (PHEV), it includes actually a new  battery charging system that can be fed externally. The combustion  engine works as a backup when the batteries are depleted and the driver  cannot have a break for charging. Porsche announced the new Panamera  Plug-in S E-Hybrid that replaces the old Panamera Hybrid offering more  during responsiveness and vehicle performance.

This  is configuration of a typical fuel cell electric vehicle. So, it uses  fuel cell as a source of energy which is connected to Hydrogen tank,  fuel cells used in FCEVs use hydrogen fuel stored onboard and oxygen  from the air to produce electricity. A boost converter is required to  step up the voltage of the fuel cell to charge the battery and store the  energy. An Electric drive and the mechanical propulsion system is  similar to battery electric vehicle. Battery bank enables two purposes.  First, it allows fuel cell to operate at optimum efficiency. Secondly,  it can support the transient mechanical energy requirements at the  wheel. It can also help to store regenerative energy coming during  braking since fuel cell is incapable of the storing regenerative energy.         

                 As  long as a fuel is supplied FCs continue to generate electricity,  similar to conventional ICEs. However, fuel cells are much cleaner; they  convert fuels directly into electricity via an electro-chemical process  that does not need combustion. The generated power from a fuel cell  stack depends on the number and size of the individual fuel cells. A  fuel cell vehicle that is fueled with hydrogen emits only water and  heat. By providing clean, high-efficiency, reliable green transportation  facilities, FCs have become important technology in development of  electric vehicles. In addition, fuel cells are being developed for  buses, boats, motorcycles, and many other kinds of vehicles.

Control strategies for  hybrid-electric vehicles generally target several simultaneous  objectives. The primary one is the minimization of the vehicle fuel  consumption, while also attempting to minimize emissions and to maintain  or enhance drivability. To date, the power management (PM) system in  EVs is basically formed by two layers; High level software-based  supervision and low-level hardware-based control which can be divided  into two control layers low level component and low-level control. Both  hardware and software control layers work together to optimize PM system  in EVs. Major challenge of energy management system (EMS) in an  electric vehicle is to assure optimal use and regeneration of the total  energy in the vehicle. Regardless of number of sources, the powertrain  configuration, at any time and for any vehicle speed, the control  strategy has to determine the power distribution between different  energies. When two storage systems or two fuel converters are available  additional power distribution between the RESSs and between the fuel  converters has to be determined. These decisions are constrained by two  factors. First of all, the motive power requested by the driver must  always be satisfied up to a maximum power demand already known. Then, charge status must be maintained within, allowing the vehicle to be  charge continuously.

Power  management control design starts with the hardware level, more  precisely with vehicle power train which is a must in every EVs.  Presented in different approaches and combinations, the only purpose in  power train design is to obtain optimal power management results,  increase vehicle performance and robustness, and reduce energy loss in  transmission. Generally, there are 6 transfer architectures in BEV;

5.1.1 Conventional Drivetrain

conventional  drivetrain with clutch. The vehicle is equipped and Energy Storage  System (ESS) that delivers electrical energy to the main EM through a  power converter. The mechanical energy provided reaches the front wheels  through a quite long way; a clutch, a gearbox and a differential.

5.1.2 Single-gear transmission architecture

The  clutch is deleted and the gearbox is replaced with a fixed gear  transmission unit while the entire architecture remains the same. This  little enhancement simplifies the driveline configuration and reduces  the size and weight of transmission system. By following the same logic.

5.1.3 Integrated single-gear and differential architecture

It  groups the electric motor, the single-gear box and the differential in  same level with wheels. The BEV is lighter and mechanical transmission  losses become minimal.

5.1.4 Separated EM and fixed gearing architecture

The  need to enhance the cornering performance in BEVs, each wheel gets its  own fixed gearing and own electric motor. Thus, it is possible to  operating different speeds.

5.1.5 Fixed EM and gearing architecture

The  wheels were exploited. In-wheel application reduces even more weight  and complexity. Here, vehicle operates in direct drive without a drive  shaft; wheels are equipped with the fixed gearbox and driven directly by  Ems.

5.1.6 In-wheel drive architecture

The  same architecture is kept in final configuration but with more use of  in-wheel application. The EM is built right in the wheel and the drive  train is reduced to zero. Each EM receives power from a dedicated power  converter feed by the Energy Storage System.

The Full Hybrid HEVs have mainly 4 architectures (types) are available and aiming different vehicle purposes;

5.1.7 Series drive Train Configuration (Convectional Series HEV)

This  is configuration of typical series hybrid vehicle where an IC engine is  connected to a typical electric drive using a electric generator and  battery charger, only the Electric Motor is coupled the transmission  shaft. This configuration allows high efficiency of IC engine.

5.1.8 Parallel Drive Train configuration (Convectional Parallel HEV)

This  is the configuration of a conventional parallel HEV where both the IC  Engine and battery based electric drive is coupled to the transmission  system using a clutch known as dual clutch transmission (DCT). So the  System offers three modes, an IC engine mode alone, an electric engine  mode alone or a combined IC engine & Electric motor mode. So the  electric motor can not only be used to operate the vehicle, it can also  be used to recharge the battery during regenerative braking. This motor  can also used as a generator to recharge the battery when power required  at the wheel is less than the available power from the IC engine.

5.1.9 Series-Parallel Configuration (Convectional Series-Parallel HEV)

This  is the configuration of typical Seirs-Parallel HEV by combines previous  both features of a Series & Parallel HEV. Such a configuration is  possible only because of a special mechanical gearing system which  allows all the modes of Series & Parallel confutation, however it  keeps providing electric power through linked generator.

5.1.10 Complex Configuration (Complex HEV)

In  this configuration, by replacing the generator in previous  configuration and adding a second converter to store electrical energy  in car battery, HEV become more controllable and efficient. Both HEV and  BEV architectures use DC/AC converters to control electric motors  feeding and DC/DC converters to manage two-way energy for battery  charging or use.

In  high supervisory Power Management Layer (PML), many algorithms have  been developed. Depending on powertrain architecture, mainly five  techniques proved reliability and delivered intended results Offline  Power Management Control (PMC) Algorithms, Online PMC Algorithms,  Rule-Based PMC Algorithms and Learning PMS Algorithms and GPS-Enhanced  PMC Algorithms.

5.2.1 Offline Power Management Control Algorithms

Optimization  Criteria: Stochastic optimal control of complex dynamic systems is a  present fact in engineering. The problem is formulated as sequential  decision making under uncertainty, where a controller is faced with the  task of selecting actions in several time steps to efficiently achieve  the system’s long-term goals. DP: Dynamic programming (DP) has been  generalized as the main method to analyze sequential decision-making  problems, such as deterministic and stochastic optimization and control  problems, mini-max problems, and other varied problems. While the nature  of these problems may vary widely, their underlying structure is  similar to each other and has two principal features: an underlying  discrete time dynamic system whose state evolves according to given  transition probabilities that depend on the decision taken at each time  and a cost function that is additive over time. Although DP can yield a  global optimal solution in closed form, for many problems, a complete  solution by DP is impossible.

5.2.2 Online Power Management Control Algorithms

MPC:  Model predictive control (MPC) relies on prediction models to obtain a  control action by solving an online optimization problem over a finite  horizon. It is often used in constrained regulatory related control  problems of large-scale multivariable systems, where the objective is to  operate the system in a certain desired way. Pontryagin’s Minimum  Principle and ECMS: One of the principal procedures in solving  optimization problems is to derive a set of necessary conditions that  must be satisfied by any optimal solution. These conditions become  sufficient under certain convexity conditions on the objective and  constraint functions. Optimal control problems may be regarded as  optimization problems in infinite-dimensional spaces, and thus, they are  substantially difficult to solve.

5.2.3 Rule-Based Power Management Control Algorithms

Rules  Based (RB) method relays on expert experience base to determine fine  adjustments to be applied in PMC algorithm. The PMC strategy can be  based on fuzzy logic, decentralized adaptive logic, or even new set of  rule-based PMC algorithms.

5.2.4 Smart / Learning Power Management Control Algorithms

To  optimize EV efficiency, PMC algorithms include a learning mechanism  that allows improving performance over time, every single reaction of  the driver is considered including driving style, sprint, breaking  style, and distances driven. All these collected information’s build a  database specific to the user driving style and there are PM adjustments  communicated to driving parameters. This has a major impact on fuel  economy and system responsiveness.

5.2.5 GPS enhanced Power Management Control Algorithms

These  algorithms are to enhance PMC algorithms using information received  from a Global Positioning System (GPS). The algorithm uses data and  loads corresponding topography of the road and operates according to  preconfigured driving style to minimize fuel consumption. These  enhancement algorithms are using driving pattern recognition to  automatically select a control algorithm from a bank of six optimized  representative driving modes using artificial neural networks (ANNs)

BMS is an electronic system that  manages a rechargeable battery to ensure it operates safely and efficiently. BMS is designed to monitor the parameters associated with  the battery pack and its induvial cells, apply the collected data to  eliminate safety risks and optimize the battery performance

The  energy management is a critical factor for EVs. Hence, the battery  management system (BMS) is a key system that is designed to manage and  control the battery unit in this kind of vehicle. More specifically, BMS  is responsible for managing the energy that is provided by the  batteries with the aim of guaranteeing their safety and reliability.  Current BMSs comprise of multiple blocks, such as power delivery unity,  sensors, and communication channels, integrated together. The prime task  of BMSs is to manage the power delivery trying to reduce the battery  stress due to charges and discharges. BMS is the central controller  preventing sudden abruption in current, and thus avoiding high discharge  rates. Cell balancing is also critical for EVs’ high-powered battery  packs, because a long series of individual cells is only as reliable as  the weakest cell. According to this, the BMS maintains cell balancing by  compensating the load of the weaker cell. In particular, it equalizes  the charge on all cells in the chain to extend the overall life of the  battery pack. In this way, BMS prevents individual cells from becoming  overstressed. Another important task of BMSs is measuring the state of  charge and computing the driving range. Auxiliary devices, such as  headlamps, the dashboard, and the cooling/heating unit, also draw power  from the battery pack. However, these devices are not smart, nor do they  communicate with BMS. A smarter managing of these energy demands would  result in a better power delivery without reducing the power train  efficiency.

There are four key standards related to  safety, installation and connection of the Electric Vehicle Supply  Equipment (EVSE) to the EV; UL 2594, UL 2231, SAE J1772, and NEC Article  6252. EVs typically charge from conventional power outlets or dedicated  charging stations, a process that typically takes hours, but can be  done overnight and often gives a charge that is sufficient for normal  everyday usage. To date, mainly three charging techniques are available.

7.1    Conductive charging,

This  is a direct electrical connection (typically through an insulated  wire/cord set) between the source and the charging circuitry. The  circuitry and its controls may be housed within the vehicle or external  to it. All new EVs are compatible with this approved standard. There are  three modes of EV charging;

7.1.1 Standard Mode (Level 1): - (AC 120V single phase power at up to 12 Amps)

Level  1 electric vehicle charging is rated at 120 volts. The hardware  required for this, which is a cord with an attached control-box, is  supplied as standard with every electric vehicle. One has to simply  plug-in to a three-prin (grounded) wall socket. Using this charging  technique usually takes 16 to 20 hours to fully charge the vehicle’s  batteries depending upon its capacity. The advantage of using this  charging type is that it does not require the installation of additional  hardware. One simply needs to the park near a three-pin wall socket and  plug-in the charging cable. 

7.1.2 Semi-Quick mode (Level 2): -( AC 3 phases 240V, 32A current)

Level  2 charging for electric vehicles is rated at 240 volts. Additional  hardware is required for this type of charging. On the purchase of an  electric vehicles, some manufacturers will install an AC wall-box  charger at the customer’s home and in some cases the place of work as  well, either free of cost or otherwise, in order to enable level 2  charging. With the use of this, an electric vehicle can be fully charged  in as early as 6 hours or a little over, depending upon the battery  capacity. Level 2 charging is considerably faster in comparison to Level  1 charging. Not only this, but it is said to be more energy-efficient  as well. However, this charging technique is expensive because of the  use of more sophisticated hardware

7.1.3 Quick mode: - (DC 480 Volt, 80-200A current)

The  level 3 charging for electric vehicles is what one will find at public  charging stations. Called as DC fast charging, it converts the AC  current, into DC current for direct storage in electric vehicle  batteries. It is usually rated at 480 volts. With the use of a DC fast  charger, an electric vehicle can be charged to 80 per cent in less than  an hour. The hardware required for the same is quite expensive  and is usually found at public charging stations. In order to use them,  one needs to pay a certain amount to the service provider.

7.2 Inductive charging:

  No wiring is required; instead, the energy is transferred between  the charger and the "Paddle" inside the vehicle's inlet via a magnetic  field generated by a high AC current. Inductive charging is still  expensive and complicated to set up for end user.

7.3 Batteries swapping:

Instead  of recharging EVs from electrical socket, batteries could be  mechanically replaced in a couple of minutes in some special stations.  Here battery size and geometry should be standardized in order to relay  on Battery swapping technique.

Electric cars are critically  important to the future of the automobile industry and to the  environment, as we came to following facts that number of expected  vehicles doubling on the road in the near future the need for this  alternative energy is very evident and has promising returns.

                    Consumption of decreasing oil supplies, concerns over  air and noise pollution, and pollution caused by abandoned cars and the  complications of recycling gasoline-powered cars all are driving forces  that seem to be pushing towards the success of the electric cars. It’s  hard to imagine a modern car without embedded software. It’s even  harder to imagine an electric vehicle without it. From maintaining and  monitoring the battery to the user interface software is one of the most  vital components of EV. EVs already have software embedded in every  part, and this trend will be only greater in future EVs. This prevalence  of software and digital all over the electric vehicle opens up a wide  variety of opportunities for the IT, software companies and digital  solutions providers. The other automotive trends such as connected,  shared and autonomous vehicles add even further diversity to these  opportunities.

              With increasing pressure on improving the quality & safety  of Electric Vehicles, the requirement for development of different  applications used for safety, quality & stability of electric  vehicle not possible for a single company.

                    Third-party component providers can help in reducing  time to market, so various Service Delivery Platform providers should be  considered.Next-generation  EVSE must adjust to become smarter and more capable in future. It must  support smart-grid functionality, which holds great potential to lower  the system cost of providing energy to PHEVs and EVs. With smart-grid  interactions, not only the distribution grid will be better optimized  for lower energy costs but also the users can use the PHEVs and EVs at  lower electricity costs, and charge faster with higher efficiency.