Distributed charging systems divide electric vehicle batteries and charge them separately using multiple charging lines. This document discusses various electric vehicle charging technologies including onboard and offboard chargers. It describes different charging levels from Level 1 using standard outlets to Level 3 fast chargers that can charge an electric vehicle to 80% in under an hour. The document also covers topics like single stage and two stage chargers, bidirectional converters, and the impact of fast charging stations on electric grids.
The transportation industry continues to adopt more supercapacitors into their designs each year. Advantages in power density, cold temperature performance, and lifetime make them suitable for accompanying or replacing a battery bank.
This presentation introduces what a supercapacitor is (it isn't just a big capacitor!), some characteristics to consider, and two applications of ELDCs.
This paper was presented by KEMET at the 2015 Applied Power Electronic Conference in Charlotte, NC.
The transportation industry continues to adopt more supercapacitors into their designs each year. Advantages in power density, cold temperature performance, and lifetime make them suitable for accompanying or replacing a battery bank.
This presentation introduces what a supercapacitor is (it isn't just a big capacitor!), some characteristics to consider, and two applications of ELDCs.
This paper was presented by KEMET at the 2015 Applied Power Electronic Conference in Charlotte, NC.
Supercapacitors (Ultracapacitor) : Energy Problem Solver,Amit Soni
Capacitor, Basic design and terminology, Supercapacitor, History of Supercapacitor
Classification of Supercapacitors, Electrical Double layer capacitors,Pseudocapacitor
Hybrid Capacitor, Basic Design, Construction, Working , Technology used, Why these substances used ?, Features, Comparison, Applications , Advantages & Disadvantages
state of art materials, comparison with batteries, fuel cells, applications
SUPERCAPACITORS AND BATTERY POWER MANAGEMENT FOR HYBRID VEHICLE APPLICATIONS ...Pradeep Avanigadda
This project presents super capacitors and battery association methodology for ECCE Hybrid vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ESLaboratory in collaboration with the Research Centre in Electrical Engineering and Electronics in Belfort (CREEBEL) and other French partners. This test bench has currently lead-acid batteries with a rated voltage of 540 V, two motors each one coupled with one alternator. The alternators are feeding a DC-bus by rectifiers.
The main objective of this paper is to study the management of the energy provides by two super capacitor packs. Each super capacitors module is made of 108 cells with a maximum voltage of 270V. This experimental test bench is carried out for studies and innovating tests for the Hybrid Vehicle applications.
This paper presents a battery-less power supply using supercapacitor as energy storage powered by solar. In this study the supercapacitor as energy storage, as opposed to batteries, has widely researched in recent years. Supercapacitors act like other capacitors, but their advantage is having enormous power storage capabilities. Maximum charging voltage and capacitance are two variables of storage in the supercapacitor. The supercapacitor is used as energy storage to charge a low power device wirelessly and act as a power supply. The solar energy is used as a backup power supply if there is no electricity in the remote or isolated area to charge the supercapacitor. The time taken to charge the supercapacitor depend on the amount of current rating of the solar panel. The higher the current, the shorter the time taken to charges the supercapacitor. Power supply using supercapacitor can store up to 30 Vdc using a DC-DC boost converter.
Supercapacitors and Battery power management for Hybrid Vehicle Applications ...Pradeep Avanigadda
This paper presents supercapacitors and battery association methodology for ECCE Hybrid
vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ES Laboratory in collaboration with
the Research Center in Electrical Engineering and Electronics in Belfort (CREEBEL) and other French
partners. This test bench has currently lead-acid batteries with a rated voltage of 540 V, two motors
each one coupled with one alternator. The alternators are feeding a DC-bus by rectifers. The main
objective of this paper is to study the management of the energy provides by two supercapacitor
packs. Each supercapacitors module is made of 108 cells with a maximum voltage of 270V. This
experimental test bench is carried out for studies and innovating tests for the Hybrid Vehicle
applications. The multi boost and multi full bridge converter topologies are studied to define the best
topology for the embarked power management. The authors propose a good power management
strategy by using the multi boost and the multi full bridge converter topologies. The experimental and
simulation results of the two converter topologies are presented.
Supercapacitors (Ultracapacitor) : Energy Problem Solver,Amit Soni
Capacitor, Basic design and terminology, Supercapacitor, History of Supercapacitor
Classification of Supercapacitors, Electrical Double layer capacitors,Pseudocapacitor
Hybrid Capacitor, Basic Design, Construction, Working , Technology used, Why these substances used ?, Features, Comparison, Applications , Advantages & Disadvantages
state of art materials, comparison with batteries, fuel cells, applications
SUPERCAPACITORS AND BATTERY POWER MANAGEMENT FOR HYBRID VEHICLE APPLICATIONS ...Pradeep Avanigadda
This project presents super capacitors and battery association methodology for ECCE Hybrid vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ESLaboratory in collaboration with the Research Centre in Electrical Engineering and Electronics in Belfort (CREEBEL) and other French partners. This test bench has currently lead-acid batteries with a rated voltage of 540 V, two motors each one coupled with one alternator. The alternators are feeding a DC-bus by rectifiers.
The main objective of this paper is to study the management of the energy provides by two super capacitor packs. Each super capacitors module is made of 108 cells with a maximum voltage of 270V. This experimental test bench is carried out for studies and innovating tests for the Hybrid Vehicle applications.
This paper presents a battery-less power supply using supercapacitor as energy storage powered by solar. In this study the supercapacitor as energy storage, as opposed to batteries, has widely researched in recent years. Supercapacitors act like other capacitors, but their advantage is having enormous power storage capabilities. Maximum charging voltage and capacitance are two variables of storage in the supercapacitor. The supercapacitor is used as energy storage to charge a low power device wirelessly and act as a power supply. The solar energy is used as a backup power supply if there is no electricity in the remote or isolated area to charge the supercapacitor. The time taken to charge the supercapacitor depend on the amount of current rating of the solar panel. The higher the current, the shorter the time taken to charges the supercapacitor. Power supply using supercapacitor can store up to 30 Vdc using a DC-DC boost converter.
Supercapacitors and Battery power management for Hybrid Vehicle Applications ...Pradeep Avanigadda
This paper presents supercapacitors and battery association methodology for ECCE Hybrid
vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ES Laboratory in collaboration with
the Research Center in Electrical Engineering and Electronics in Belfort (CREEBEL) and other French
partners. This test bench has currently lead-acid batteries with a rated voltage of 540 V, two motors
each one coupled with one alternator. The alternators are feeding a DC-bus by rectifers. The main
objective of this paper is to study the management of the energy provides by two supercapacitor
packs. Each supercapacitors module is made of 108 cells with a maximum voltage of 270V. This
experimental test bench is carried out for studies and innovating tests for the Hybrid Vehicle
applications. The multi boost and multi full bridge converter topologies are studied to define the best
topology for the embarked power management. The authors propose a good power management
strategy by using the multi boost and the multi full bridge converter topologies. The experimental and
simulation results of the two converter topologies are presented.
Welcome all to travel green and carbon free road use electric vehicles on roadMahesh Chandra Manav
We all has to take responsibility to maintain Green Clean Environment by use of Electric Vehicle and Charging Infra Domestic ,Office and Public Place .
plz go through presentation and contact us
This presentation cover the basics about the present electric vehicle charging Infrastructure. It also highlight the challenged faced by EV Industry for unique charging standard. Solution is also suggested.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Online aptitude test management system project report.pdfKamal Acharya
The purpose of on-line aptitude test system is to take online test in an efficient manner and no time wasting for checking the paper. The main objective of on-line aptitude test system is to efficiently evaluate the candidate thoroughly through a fully automated system that not only saves lot of time but also gives fast results. For students they give papers according to their convenience and time and there is no need of using extra thing like paper, pen etc. This can be used in educational institutions as well as in corporate world. Can be used anywhere any time as it is a web based application (user Location doesn’t matter). No restriction that examiner has to be present when the candidate takes the test.
Every time when lecturers/professors need to conduct examinations they have to sit down think about the questions and then create a whole new set of questions for each and every exam. In some cases the professor may want to give an open book online exam that is the student can take the exam any time anywhere, but the student might have to answer the questions in a limited time period. The professor may want to change the sequence of questions for every student. The problem that a student has is whenever a date for the exam is declared the student has to take it and there is no way he can take it at some other time. This project will create an interface for the examiner to create and store questions in a repository. It will also create an interface for the student to take examinations at his convenience and the questions and/or exams may be timed. Thereby creating an application which can be used by examiners and examinee’s simultaneously.
Examination System is very useful for Teachers/Professors. As in the teaching profession, you are responsible for writing question papers. In the conventional method, you write the question paper on paper, keep question papers separate from answers and all this information you have to keep in a locker to avoid unauthorized access. Using the Examination System you can create a question paper and everything will be written to a single exam file in encrypted format. You can set the General and Administrator password to avoid unauthorized access to your question paper. Every time you start the examination, the program shuffles all the questions and selects them randomly from the database, which reduces the chances of memorizing the questions.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
1. 1
ABSTRACT
Distributed charging system is a system that divide the battery pack and
charging them separately. Many different types of electric vehicle (EV) charging
technologies are described in literature and implemented in practical
applications. This paper presents an overview of the existing and proposed EV
charging technologies in terms of converter topologies, power levels, power few
directions and charging control strategies. An overview of the main charging
methods is presented as well, particularly the goal is to highlight an effective
and fast charging technique for lithium ions batteries.
Concerning prolonging cell cycle life and retaining high
charging efficiency. Once presented the main important aspects of charging
technologies and strategies, in the last part of this paper, through the use of
genetic algorithm, the optimal size of the charging systems is estimated and, on
the base of a sensitive analysis, the possible future trends in this Feld are finally
valued Existing Chargers provide a DC charging voltage from an AC source
whether from a common socket outlet or more recently from a purpose-built
DC charging station. Most important are the methods of controlling the charge
and protecting the battery from over-voltage, over-current and over-
temperature. These charger functions are integrated with and unique to the
battery.
Chargers for passenger cars are normally mounted inside the car.
This is because the vehicle may be used a long way from home, further than the
range possible from a single battery charge. For this reason, they have to carry
the charger with them on board the vehicle. Charging can be carried out at home
from a standard domestic electricity socket outlet but the available power is
very low and charging takes a long time, possibly ten hours or more depending
on the size of the battery. Since charging is usually carried out overnight this is
not necessarily a problem, but it could be if the car is away from its home base.
Such low power charging is normally used in an emergency and most cars are
fitted with a higher power charging option which can be used in commercial
locations or with a higher power domestic installation. In many countries this
higher power facility is implemented by means of a three-phase electricity
supply.
2. 2
CONTENTS
1. Abstract 01
2. Introduction 03
3. Different charging system of EV 04
• AC level 1 04
• AC level 2 05
• Dc level 3 / DC fast charge 06
4. Distributed Charging system 07
5. Onboard Charger 08
6. Two Stage 08
7. Single Stage 09
8. Multifunctional 10
9. Off‑Board Charger 10
10. Unidirectional AC/DC Converter 11
11. Bidirectional AC/DC Converter 11
12. Unidirectional DC/DC Converter 12
13. Fast Charging Stations 12
14. Architecture 13
15. Power Control Strategies 15
16. Charging Methods 15
17. Constant Current‑Constant Voltage (CC–CV) 16
18. Charging Strategies Based on Battery Physical‑Based Models 17
19. Conclusion 19
20. References 20
3. 3
Introduction
Since the appearance of the internal combustion engine towards the end of the
19th century and specifically its installation and use in wheeled automobiles,
motorcars have been creating pollution as a result of their emissions to the
environment. The degree of this pollution has been increasing over time with
more and more automobiles appearing on the roads through the years. It was
only in the early 1950's when air pollution and automobiles were first linked by
a California researcher who determined that vehicle traffic was the cause for the
smoggy skies over the city of Los Angeles. In relatively recent years, there have
been several attempts to regulate these emissions, such as the first auto
emissions law which was passed in California in 1964 and the establishment of
the United States Environmental Protection Agency in 1970 under the
presidency of Richard Nixon. Despite the several emissions regulations, the
internal combustion engine, powered by fossil fuels, will inevitably continue to
emit and cause environmental pollution. This fact, coupled with the rapid
technological developments through the late 20th century until today, has
stimulated corporations worldwide to pursue and develop alternative means to
vehicle power, in an overall effort of both reducing environmental harm and
abiding to stringent emission laws passed by national governments around the
globe.
Distributed charging system will be gained significant
popularity over the past few years as they are generally believed to be a
‘greener' solution compared to their gasoline peers. It is well known that vehicle
emissions are responsible for large amounts of greenhouse gas production and
are leading contributors toward smog and general air pollution. Consumers as a
whole are starting to be more environmentally aware of these problems. With
gas prices skyrocketing over the past few decade’s consumers have yet another
reason to start paying more attention to the benefits of using alternative, low-
emission vehicles. At the same time, car manufacturers around the world have
been developing new technologies to promote the usage of hybrid and electric
vehicles. “The market for electric cars is sputtering, but the price of the
technology is falling”, says Michael Law.
4. 4
Different charging system of EV:
• AC level 1
• AC level 2
• Dc level 3 / DC fast charge
AC level 1 charger:
Level 1 equipment provides charging through a 120 volt (V), alternating-current
(AC) plug and requires a dedicated circuit. Generally speaking, Level 1 charging
refers to the use of a standard household outlet. Level 1 charging equipment is
standard on vehicles and therefore is portable and does not require the
installation of charging equipment. On one end of the provided cord is a
standard, three-prong household plug. On the other end is a connector, which
plugs into the vehicle.
Depending on the battery technology used in the vehicle, Level 1 charging
generally takes 8 to 12 hours to completely charge a fully depleted battery. The
most common place for Level 1 charging is at the vehicle owner's home and is
typically conducted overnight.
The type 1 plug is a single-phase plug which allows for charging power levels of
up to 7.4 kW (230 V, 32 A). The standard is mainly used in car models from the
Asian region, and is rare in Europe, which is why there are not many public type
1 charging stations.
5. 5
AC Level 2 charger:
Level 2 equipment offers charging through a 240V, AC plug and requires
installation of home charging or public charging equipment. These units require
a dedicated 40-amp circuit. Level 2 charging equipment is compatible with all
electric vehicles and plug-in electric hybrid vehicles. Level 2 chargers have a cord
that plugs directly into the vehicle in the same connector location used for Level
1 equipment. Depending on the battery technology used in the vehicle, Level 2
charging generally takes 4 to 6 hours to completely charge a fully depleted
battery. Charging time can increase in cold temperatures. Level 2 chargers are
commonly found in residential settings, public parking areas, places of
employment and commercial settings.
The triple-phase plug is mainly used in Europe. In private
areas, charging power levels of up to 22 kW are common, while charging power
levels of up to 43 kW (400 V, 63 A, AC) can be used only at public EV Charging
stations. Most public charging stations are equipped with a type 2 socket. All
mode 3 charging cables can be used with this, and electric cars can be charged
with both type 1 and type 2 plugs. All mode 3 cables on the sides of charging
stations have so-called Menaces plugs (type 2). Now a days some car
manufacturers are setup the level 2 charger in the home with the car.
6. 6
Level 3 / DC fast charger:
AC charging is the simplest kind of charging to find – outlets are everywhere
and almost all EV chargers you encounter at homes, shopping plazas, and
workplaces are Level 2 AC chargers. An AC charger provides power to the on-
board charger of the vehicle, converting that AC power to DC in order to enter
the battery. The acceptance rate of the on-board charger varies by brand but is
limited for reasons of cost, space and weight. This means that depending on
your vehicle it can take anywhere from four or five hours to over twelve hours
to fully charge at Level 2.
DC Fast Charging bypasses all of the limitations of the on-board charger and
required conversion, instead providing DC power directly to the battery,
charging speed has the potential to be greatly increased. Charging times are
dependent on the battery size and the output of the dispenser, and other
factors, but many vehicles are capable of getting an 80% charge in about or
under an hour using most currently available DC fast chargers.
DC fast charging is essential for high mileage/long distance driving and large
fleets. The quick turnaround enables drivers to recharge during their day or on
a small break as opposed to being plugged in overnight, or for many hours, for
a full charge.
Older vehicles had limitations that only allowed them to charge at 50kW on DC
units (if they were able to at all) but newer vehicles are now coming out that
can accept up to 270kW. Because battery size has increased significantly since
the first EVs hit the market, DC chargers have been getting progressively higher
outputs to match – with some now being capable of up to 350kW.
Currently, in North America there are three types of DC fast charging:
CHAdeMO, Combined Charging System (CCS) and Tesla Supercharger.
All major DC charger manufacturers offer multi-standard units that offer the
ability to charge via CCS or CHAdeMO from the same unit. The Tesla
Supercharger can only service Tesla vehicles, however Tesla vehicles are
capable of using other chargers, specifically CHAdeMO for DC fast charging, via
an adapter.
7. 7
DC Fast charging
DISTRIBUTED CHARGING SYSTEM:
Distributed charging system is a system that divide the battery pack and
charging them separately. Many different types of electric vehicle (EV)
charging technologies are described in literature and implemented in practical
applications
In distributing charging system, we use five bidirectional Dc output which was
named DC 1, DC 2, DC 3, DC 4 & DC 5 respectively. Also, the charging station
has a negative and an earth contact for drain the over current voltage in
casualty. They are connected to DCS charging connector.
In the electric vehicle the manufacturers are used lithium-ion battery pack. The
Batteries are laying on the bas of the vehicle. In distributed charging system the
8. 8
charging contacts has five inputs Line 1, Line 2, Line 3, Line 4 and line 5
respectively. Also, it has Negative contact like the Charging station connector.
Onboard Charger:
Battery chargers can be implemented inside (on-board) or outside (off-board)
the vehicle. Onboard battery chargers (OBC) are limited by size, weight and
volume for this reason they are usually compatible with level 1 and level 2
chargers. They usually have unidirectional power transfer capability;
nevertheless, in some case the configuration, a bidirectional power transfer can
be achieved. Figure 1 shows the typical architecture of an electric vehicle
charging system, in such figure both the on-board charger and the offboard one
is represented
Two Stage:
Onboard chargers are typically composed by two stages: a front-end AC–DC
stage and a back-end DC-DC stage. Very different topologies are proposed in
literature for both the converters. The front-end rectifier usually contains a
boost power factor correction (PFC) converter to achieve high power factor and
low harmonic distortion. The rectifier stage can be performed by a half-bridge,
9. 9
full-bridge or multilevel diode bridge. Half-bridge rectifier is less expensive since
it.
converter while the charge control is performed by the buck converter. On the
other and by adding an additional stage to the dc–dc converter, the complexity
and the cost of the converter increases. Finally, a dc–dc non-isolated buck
converter is employed. This latter topology is easy to implement but it works
only if the dc-link voltage is higher than the battery pack voltage.
Single Stage:
If the ac–dc rectifier is combined with the dc-dc converter, a single stage battery
charger is obtained. This topology of battery charger is used if lower cost and
size are required, in fact single stage battery charger allows the elimination of
some bulky and expensive components such as inductors and dc-link capacitors
which instead are required in two-stage charger. However, the drawback is that
single stage battery chargers with non-isolated converter suffer from a limited
conversion ratio, which limits their application for the wide range of output
voltage. If instead a high frequency isolation is present, as in the OCB
configuration
proposed in, the low frequency component generated by the rectification stage
pass through the high frequency transformer leading to large magnetizing
10. 10
current. Moreover, to achieve power factor correction, a large number of diodes
and active switches could be necessary, increasing in this way the complexity of
the configuration and hence decreasing the reliability of the overall charger.
Multifunctional:
The last type of proposed OBC is the so called multifunctional OBCs. In this type
of battery charger some components are shared to accomplish different aims.
In this way higher fuel efficiency can be reached by smaller and lighter design.
In, the proposed multifunctional battery charger can charge the auxiliary battery
via the propulsion battery when the vehicle is in a driving state, acting in this
way as an OBC and as low-voltage dc-to-dc converter (LDC) jointly. In, a similar
configuration, shown in Figure, with the same duties is presented.
Off‑Board Charger:
Level 3 charger, because of their rating powers, are usually installed outside the
vehicle (off-board). Also, for level 3 off-board charger a large number of
different solutions is studied in literature [43–62]. Since it is mandatory to
guarantee galvanic isolation between the AC supply circuit and the DC output
circuit according to the IEC EN 61,851–23 standard, in this paragraph only
isolated off-board charger have been presented. The off-board charging system
is most commonly composed of two stages: a grid-facing AC/DC converter
followed by a DC/DC converter providing an interface to EV battery. Based on
the converter topology, both these stages can allow unidirectional or
bidirectional power flow.
11. 11
Unidirectional AC/DC Converter:
The most common unidirectional AC/DC converter used in off-board charging
system is the Vienna rectifier. It has advantages such as low voltage stress on
each switch and high efficiency. However, the main limitations are the restricted
reactive power control and the need of a dc-link capacitor voltage balancing. In
the authors propose a 25 kW off-board charger prototype composed by a single
switch Vienna rectifier, as depicted in Figure, and four three level dc/dc modules
parallel connected.
Bidirectional AC/DC Converter:
One of the most widely used bidirectional AC/DC converters the three-phase
LCL active rectifier, whose scheme is reported. The advantages of this type of
converter are low harmonic input currents, bidirectional power flow and
power factor (PF) regulation. In and the front-end ac–dc conversion is
performed by a neutral-point-clamped (NPC) three-phase three level
converter. This converter has been used to increase the power density and to
achieve low current harmonics distortion. Another advantage is that it allows
the creation of a bipolar dc bus which can be used for the implementation of
partial-power converters. However, the NPC causes imbalance of power and,
as a result, voltage balancing problem across the DC bus capacitors
12. 12
Unidirectional DC/DC Converter:
If unidirectional power flow is required, a LLC resonant converter is chosen, in
most cases, as power interface between the dc bus of the AC/DC converter and
the EV battery because of to its advantages over other resonant topologies, such
as: the ability to operate at zero-voltage switching (ZVS) or zero-current
switching (ZCS), it allows a wide output voltage regulation, the output filter
consists only of a capacitor and not of an inductor and capacitor (LC) filter.
Another unidirectional DC/DC converter used in case of unidirectional off-board
charger is the phase shifted full bridge converter, whose scheme is reported in
Figure. This type of converter has different advantages such as high-power
density, low magnetic interference and high efficiency which makes it well
suitable for the implementation in battery chargers.
Fast Charging Stations:
stronger increase of the penetration of EVs worldwide there is the need of a
charging system which is able to replace the current existing oil station. A fast-
charging station (FCS) can allow the charging of an EV at 80% within a half of
hour from its depletion, but to reduce the charging time from7–8 h to 30 min,
FCS requires high power from the grid and for this reason, they are usually
connected to the MV network, even if some FCS connected to the LV grid is
proposed too. The connection of such charging stations requires a huge capital
investment and it could easily overload the distribution network. Another
13. 13
critical aspect to be considered consists in the voltage drop that the connection
of FCS can cause along the lines of the distribution networks, which according
to the standard EN50160 has to remain lower than 10%. According to the impact
of fast charging stations on distribution MV grid can be mitigated with the use
of energy storage systems (ESSs) which can shave peak power demand and
provide additional network services. Moreover, ESS can also increase the
voltage level in case of too high voltage drop along the lines, this service requires
the implementation of a voltage control. In order to further minimize the impact
of the FCS on the grid, renewable energy resources can integrate within the FCS
too. In fact, in normal operation, during daytime, the EV batteries can be
charged from the solar PV by reducing in this way the possibility of overloading
the MV network. In night-time, instead, when solar energy is not available the
EV batteries can be charged from the grid. EVs also can support to the grid at
the peak load demand if needed. By this way, the grid will never become
unstable with a high pulse power of charging from EVs.
Architecture:
The configuration chosen in for the ultra-fast charging station is shown in Figure.
The isolation between the AC side and the DC side is performed by the line-
frequency transformer. The ac–dc stage is common to all the EV; in fact, the
output of the Cascade H Bridge (CHB) multilevel converter creates a unipolar
common DC voltage bus at which all dc–dc converters are connected. The power
interfaces between the dc bus and the integrated storage or the EV battery is
14. 14
performed by an LLC resonant converter. In a bipolar dc bus architecture is
proposed. The charging station here adopted is shown in Fig. 11. The bipolar dc
bus is necessary to feed the three-level dc–dc converter. On one side, this
architecture increases the capability of the FC station and reduce the THD; on
the other hand, this system requires a DC power balance management
mechanism.
Fast charging station with unipolar dc voltage
Fast charging station with bipolar dc voltage bus
15. 15
Power Control Strategies:
A number of studies have been carried out also on the control strategy of EV
charging station. The first difference among them concerns the choice of
uncoordinated charging or coordinated charging. In uncoordinated charging
scheme the EV battery starts charging immediately when it is plugged in or after
a fixed start delay chosen by the user. If the EVs are charged according to this
scheme, their impact on the grid will result in very high peak demand and hence
in huge grid issues such as: feeders and transformers overloading, high losses,
high voltage drops, and more cost. For all the aforementioned reasons, the
research has focused on EV coordinated charging strategies, in particular.
Authors in propose a coordinated control strategy for an FCS with an ESS, their
principal aim is that of reducing the electricity purchase cost and flatten the peak
load. In the FCS contains both ESSs and RESs, the coordinated energy
management proposed here is obtained by using a Fuzzy Logic based control
defined by three inputs and two outputs. Other control strategies based on very
different and numerous algorithms have been proposed in literature. Authors in
investigate and compare three different control strategies for a charging station.
The charging strategies coordinate in different ways the energy flow of the ESS
and PV panels. The results prove that the control strategy which uses the energy
of the ESS with in response to the number of EVs plugged in and takes into
account also the amount of generated renewable energy has the best
performance. Furthermore, according to this control method, the SoC of the ESS
is restored during night and during excess of solar energy.
Charging Methods:
The advantages of a lithium-ion battery over other types of energy storage
devices such as high energy and power density, low memory effect and resulting
capacity loss, make this type of battery the best candidate for the field of electric
vehicles. However, li-ion battery charging must be carried out very carefully,
since the charging method greatly affects how actively electrochemical side
reactions occur inside the battery, and hence the cycle life of the battery itself.
For this reason, finding the optimal technique to charge a battery in the shortest
period of time with high efficiency and without damaging the cells, has become
a new challenge for many researchers. In this paragraph the main charging
methods for Li-ion batteries are discussed.
16. 16
Constant Current‑Constant Voltage (CC–CV):
In this method, represented in Fig. 12, both an initial constant current and a final
constant voltage are used. The charging process start with a constant current
until a certain voltage value, known as cut-off voltage, is reached. For Li-ion with
the traditional cathode materials of cobalt, nickel, manganese and aluminum
typically the cut-off voltage value is around 4.20 V/cell. The tolerance is ± 50
mV/ cell. Battery charging continues with a constant voltage just equal to the
cut-off value. Full charge is reached when the current decreases to between 3
and 5% of the rated current. Trickle or float charge at full charge is not suitable
for a Lion battery; since it would cause plating of metallic lithium and
compromise safety. Instead of trickle charge, a topping charge can be applied
when the voltage drops below a set value, a little bit different variant is
proposed, in fact the first stage consists now in a trickle charge. This stage is
activated only if the battery is deeply discharged, i.e., the cell voltage is below
3.0 V and after it the CC–CV method keeps place with the aforementioned way.
17. 17
Charging Strategies Based on Battery Physical‑Based Models:
In all the charging methods reported so far, only current and voltage limits are
considered. Anyway, these limits do not take into consideration the aging
process and the side reactions occurring inside the battery; and hence they
might result too conservative for new batteries and possibly dangerous for aged
batteries due to the altered behavior and characteristics. This, hence, motivates
the development and the research of innovative charging algorithms which
tackle the issue of the charging impact on battery state-of-health (SoH) and
aging. In fact, recently, many researches are focusing on develop new charging
methods which minimize the charging time and extend the battery life at the
same time. This new category of charging strategies employs the
electrochemical lithium-ion battery models to calculate quantitatively and
almost precisely the amount of battery aging and to directly minimize the aging
in a given charge time. The electrochemical battery model estimates the internal
states of a battery in a more accurate way since it is built starting from the
internal microstructure of the lithium-ion battery. However, it is very arduous to
precisely estimate the parameters because the electrochemical model is
composed of complicated coupled partial differential equations (PDEs), and
involving a large number of parameters and boundary conditions it requires a
large computation burden. Therefore, the complexity of these models often
leads to the necessity for more memory and computational effort and thus, they
may not be practically implemented in the fast and real-time computations of
EV BMS. In recent years, many works focus on identifying simplified internal
electrochemical models of the battery for efficiently determining the battery
operation and hence finding the optimal charging profile. For example, Klein et
al. aim at achieving a fast-charging rate while not excessively aging the cell, using
nonlinear model predictive control (NMPC) techniques founded on a single
particle model (SPM) of the lithium-ion battery. In the single particle model
(SPM) the electrodes are represented by two single spherical porous particles in
which intercalation and de-intercalation phenomena take place. However, the
variations in the electrolyte con-centration and in the potential are ignored. This
electrochemical model is exhaustively explained. a method to optimize the
charging current for Lithium-ion batteries using a soft actor-critic (SAC)
reinforcement learning algorithm is proposed. As battery aging model Kim et al.
use the single particle model augmented by electrolyte and thermal dynamics
18. 18
(SPMeT). Anyway, even if this model is more exhaustive than the SPM one, it is
subject to a complicated mathematical structure including PDEs, ordinary
differential equations and algebraic equations. Therefore, the corresponding
model-based algorithms can be computationally too arduous to be
implemented in typical battery management systems (BMSs). In light of this, Zou
et al. propose and validate a simplified ODE-based SPMeT model to achieve fast
charging control. Once validated the reduced model, the authors present a
charging strategy based on model predictive control (MPC) techniques which
aims to charge the battery in the fastest possible manner, without excessively
degrading the battery’s SOH. Another widely employed electrochemical battery
model is the pseudo two-dimensional model (P2D). This model is constructed
based on the assumption that electrodes are seen as an aggregation of spherical
particles (2D representation) in which the Li + ions are inserted. The first spatial
dimension of this model, represented by variable x, is the horizontal axis. The
second spatial dimension is the particle radius r. The cell is comprised of three
regions that imply four distinct boundaries. The full description of this model can
be found in. Finally, in the authors present
19. 19
Conclusion:
The first part of this paper reviews the current conditions of EV battery charging
technologies. The most common topologies which are suitable candidates for
each level of an EV charger have been presented. Level 1 and level 2 charger
topologies are usually mounted inside the vehicle forming in this way the so-
called onboard charger. On the other side level 3 chargers are installed off board
the vehicles, in this way their collection leads to the creation of the so called
FCSs which are promising candidates for future EV high penetration. The most
common technologies used in an FCS are multilevel converters which have a
high-power density and a lower current harmonic distortion. To reduce the
impact on the grid, almost all the FCSs are integrated with RESs and ESSs. Li-ion
batteries can be recharged according many different charging techniques which
can more or less complicate the charger architecture and control. In particular
the standard charging strategy are simplest since they don’t require model
information to charge the battery. Furthermore, they can be realized with very
basic circuits, keeping the costs of the charger to a minimum. On the other hand,
the charging strategies based on electrochemical models, taking into account
the internal dynamics of the battery, consider also the aging of the battery and
other constraints, hence resulting in greater accuracy and. All this is at the
expense of cost and computational difficulty. A long-term forecasting of future
trends in the field of EV charging systems is a very tough task for different many
reasons including the lack of standards and the continuous improvements. In
the last section of this paper a possible forecasting and estimation based on GA
is described. According to the results, with the actual costs, the capacity of the
battery of an electric vehicle should be around 60 kWh, the power rating of the
onboard charger around 14 kW and that of the off-board fast charger around
170 kW. Finally, the silicon switching devices are expected to be replaced by
wide bandgap silicon carbide (SiC) devices in order to allow a remarkable
reduction in charger’s weight and volume.
20. 20
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