impact of v2g/g2v technologies on distributed generation ......hev energy storage system impact of...

Impact of V2G/G2V Technologies on Distributed

Generation Systems

G. Fabbri, G. Tarquini, L. Pasquali, L. Anniballi, S. Odoardi, S. Teodori, E. Santini

June 3 2014, Istanbul, TURKEY

Department DIAE

http://www.google.it/url?sa=i&rct=j&q=sapienza&source=images&cd=&cad=rja&docid=yT1RUjQcW_H2gM&tbnid=q2VqIsFDagRrAM:&ved=0CAUQjRw&url=http://www.controcampus.it/2012/02/dichiarazione-isee-controlli-alla-sapienza/&ei=dAdvUcGUN8H-rAeVqYGoBg&psig=AFQjCNHcYcrv14IJf2ct8deQjPuteg9Jug&ust=1366317291591827

1. INTRODUCTION

2. OVERVIEWS OF V2G SYSTEMS REQUIREMENTS

3. EXAMPLE OF V2G TECHNOLOGY DEVELOPMENT

4. CONCLUSIONS

SUMMARY

Impact of V2G/G2V Technologies on

Distributed Generation Systems

Worldwide challenges for Electricity Energy Systems:

• Integration of new sources of Energy supply

• Controlling the variability of some sources of renewable-based supply

• Changes resulting from the increased use of Hybrid and Electric Vehicles

(HEVs).

INTRODUCTION



HEV (Hybryd and Electric Vehicle) can combine:

• Electric propulsion system

• A conventional internal combustion engine

HEVs behave either as loads or as a distributed energy

and power resource in a concept known as Vehicle-

to-Grid (V2G) connection.

Vehicle-to-grid (V2G) describes a system in which plug-in

electric vehicles, communicate with the power grid to sell

demand response services by either delivering electricity

into the grid or by throttling their charging rate.

Hybryd and Electric Vehicles



Vehicle-to-Grid (V2G)

In the future the integration of HEVs in the vehicle fleet will contribute to:

• deep modifications to the current grid model of dispatching generation

• a reduction of greenhouse gases emissions

• enable a cleaner, more renewable and lower carbon grid

• cut carbon emissions

• reduce peak loads

In order to achieve this objectives this integration should:

• provide accessible recharging infrastructure

• improve the load management using Smart Metering and Communication

Systems

• Deploy Smart Grids

Hybryd Electric Vehicle





A smart grid is a modern electrical grid that uses analog or digital information and

communications technology to gather and act on information, such as information about the

behaviors of suppliers and consumers, in an automated fashion to improve the efficiency,

reliability, economics, and sustainability of the production and distribution of electricity

HEVs recharging infrastructure will form an important part of the future smart

grid.

This includes:

• physical charging facilities (connectors and meters)

• billing scheduling

• smart features for charging HEVs batteries during off-peak periods



The performance of the electricity grid can be improved in areas such as:

• Efficiency

• Stability

• Reliability

Providing thus services such as:

• Reactive power support

• Active power regulation,

• Tracking of variable renewable energy sources,

• Load balancing

• Current harmonic filtering.

Stressing these technologies can enable ancillary services, such as:

• Voltage and frequency control

• Spinning reserve



Ancillary Services

Six kinds of ancillary services for the electric power grid can been identified:

1. Scheduling and dispatch.

2. Reactive power and voltage control.

3. Loss compensation.

4. Load following.

5. System protection.

6. Energy umbalance.



Issues to be addressed for the integration of the HEVs within the Smart Grid include:

• Battery degradation

• Intensive communication between the vehicles and the grid

• Effects on grid distribution equipment

• Infrastructure changes

• Social, political, cultural and technical obstacles.



Projection for annual light-duty vehicle sales by technology type.

Plug-in Hybrid Electric Vehicles will contribute to reduce light-duty vehicle CO2

emissions in approximately 30% by 2050 in comparison with 2005 levels.

It is expected that HEVs integration will gradually increase and by 2050 HEVs will represent

more than 50% of the vehicle sales. Actual projections point that by 2020, 2.5 million EVs and 5

million PHEVs will be sold.

Hybryd Electric Vehicle

HEV Energy storage system



One of the larger obstacles to the earlier expansion of HEVs is the unavailability of an

adequate storage system to supply the power and energy demands required by drivetrain

electrification.

The most important characteristics of a battery for automotive application are:

• Battery life

• Specific power

• Specific energy

• Costs

• Safety

Key parameters of several HEVs battery types

Monitoring system



In the design, developing and test process of Recharging HEVs Monitoring Systems three

main elements should be taken into account:

1. Power connection to the grid.

2. Control and communication between vehicles and the grid operator.

3. On-board/off-board smart metering

Moreover, success of the V2G concept depends:

• Standardization of requirements

• Infrastructure decisions

• Battery technology

• Efficient and smart scheduling of limited fast-charge infrastructure.

1. INTRODUCTION


3. EXAMPLE OF V2G TECHNOLOGY DEVELOPMENT

4. CONCLUSIONS

SUMMARY



OVERVIEW OF V2G SYSTEMS REQUIREMENTS



V2G concept needs a methodological approach that takes into account:

• Unidirectional and bidirectional power flows

• Evaluation of charging and recharging frequency

• Strategies to interface to the grid:

• privately owned HEVs

• commercial HEVs fleets

• DG components

HEVs can be seen as an Aggregation of sources of stored energy, allowing, together

with other energy generation components, to achieve various benefits for grid operators

and vehicle owners



OVERVIEW OF V2G SYSTEMS REQUIREMENTS

HEVs with V2G interfaces can charge or inject energy into the grid when parked and

connected. The concept to be implemented requires an efficient power transaction and

substantial information exchange.

Three main elements can be identified:

1. A power connection to the grid.

2. A communication connection with the grid operator.

3. Suitable metering

V2G systems might be a trigger for a sustainable development of a cleaner and more

efficient transportation and energy system.

V2G technologies could support the development of a new generation of vehicle

technologies and promote the installation of intermittent renewable energies sources.



The proposed architecture consists of six major subsystems:

.

.

1. Energy

resources

and an

electric utility.

2. An Independent System Operator

(ISO) and vehicles aggregator.

3. Charging infrastructure

and locations between

each HEV and ISO or

aggregator

4. Two-way

electrical energy

flow and

communication

5. On-board and off-

board intelligent

metering and

control.

6. The HEV itself with its battery charger and Battery

Management System BMS.



HEVs, V2G and Renewable Energies

Intelligent metering and information control that is aware of battery capacity and state of

charge will allow HEVs to be considered as controllable loads and be to combined with

renewable energy trough on-board and off-board smart meters able to support V2G

methods.

Critical equipments to monitor and exchange information with the Remote Contro Center:

• GPS locators

• on-board meters

• sensors and smart meters on charging stations

Communication will be possible through a field area network allowing dynamic

adjustments that track intermittent resources and alter charge rates to track:

• power prices

• frequency or power regulation

• spinning reserves.

A variety of communication protocols have been already proposed and employed for this

purpose, including: ZigBee, Bluetooth, Z-Wave, and HomePlug



Smart Charging System

A coordinated smart charging and discharging system can:

• optimize power demand and charging time

• reduce daily electricity costs

• voltage deviations

• line currents

• transformer load surges.

• flatten the voltage profile of a distribution node and Network congestion

• prevent the waste of renewable energy

Smart charging can allow attaining the highest HEVs penetration level without violating

the network technical limits and avoiding up to 60%–70% of the required incremental

investment.



Economical and Financial Incentives

The use of HEVs may offer a variety of economical and financial incentives for

both the owners and the utilities companies.

It creates new business opportunities as HEVs fleets might be established in order to profit

by the high revenue forecast for the use of the vehicles energy storage capability, in order

to provide those ancillary services fundamentals to maintain a high quality of the energy

grid systems.

Despite there might be little financial incentive for the use of HEVs only for peak shaving,

there is a high potential financial return if the energy storage capability is used for services

such as spinning reserves and regulation.

1. INTRODUCTION


3. EXAMPLES AND PROTOTYPES OF V2G TECHNOLOGY DEVELOPMENT

4. CONCLUSIONS

SUMMARY



1. Analysis of the behavior of commercial lithium-

ion batteries

Research Activities



2. Implementation of a high power fast

recharge station.

Two research activities will be presented as examples of V2G technologies development.



Behavior of commercial lithium-ion batteries.

The first example aims at studying the behavior of commercial lithium-ion batteries

performing experimental tests run on batteries stressed:

• by a high number of cycles

• by a bad management control system.

The tests conducted aim to recover the initial capacity of the batteries.

Manufacturers of commercial batteries provide

technical specification for their correct usage:

nominal capacity:

• Operation voltage (charge and discharge)

• Max charge current

• Max discharge current

• Cycle life,

• Operating temperature

• Self discharge rate

• Weight



Behavior of commercial lithium-ion batteries.

Lithium-ion batteries offer good:

• durability

• reliability

• safety.

The use of this type of batteries in vehicles often requires the assembling of specific

battery packs based on the power requirements of the electric engine.

To ease the inspection and the installation inside the vehicle the battery pack can be split

into modules, each made by joining single batteries connected in series.

The durability and preservation of the nominal capacity are strictly related to how the

batteries are used. An optimal range of use for the process of charging and discharging it

is usually defined by manufacturer

The use of the batteries outside this charging and discharging range can stress them and

cause malfunctions that could lead to the failure of a single component inside the battery

pack, compromising the performance of the entire module.



Laboratory Equipments

The survey system might be useful for further research by providing more information

about the actual battery capacity.

The batteries tested present:

• an open circuit voltage of 3.3V

• a nominal capacity of 40Ah.

The equipment used for the experiment includes:

• a voltage generator for the charging

• the use of power resistors suitable for the absorption of large amounts of electric

energy for the discharging.

Data have been collected and managed using a Virtual Instruments (VI) programmed

using LabVIEW (a system-design platform and development environment for a visual

programming language from National Instruments).

The method allows monitoring a module made of

seven batteries, during several charging and

discharging cycles.



Parameters, Initial Conditions, Controls

The C rate of a battery is defined as the amount of current delivered in a complete

discharge cycle of one hour.

The charge and discharge tests were carried out at C/2 (20A)

We begun from an initial point where some batteries had no load voltage.

The battery charging status and the capacity behavior were monitored



Results Despite the success of charging, in terms of nominal voltage, the ill treatment in the

battery operation caused:

• a significant worsening of the nominal capacity compromising

• the re-use in the vehicle

The battery V5 rather than providing a constant voltage for two hours, discharging at C/2 rate, it is

almost completely discharged in less than 10 minutes, showing a capacity of C/12 than the

nominal

Discharging graph.



Results A partial recovery of the battery capacity was recorded after several charging and

discharging cycles.

The battery could not be used again in the vehicle since the gap between the actual

capacity and the characteristics declared by the manufacturer were still substantial.

Further experiments are needed to verify that the characteristics of the batteries have

changed as a result of aging and misuse.

The survey system used will be useful for further research by providing more information

about the actual battery capacity, thanks to several charging and discharging cycles run at

different C rates.

In future development a similar battery packs control system will be installed on vehicles to

carry out regular checks to verify the proper battery operation.



Implementation of a high power fast recharges station.

The main characteristics of the developed station:

• Power 50 kW.

• Voltage max 400 V.

• Current max 125 A

Implemented fast recharge station



Characteristics of the fast recharging station.

The recharging dock is made of two main components.

1. A power unit, capable to manage:

a) charge ramps

b) temperature limitations

c) power limitations

d) internal faults or warnings.

2. A Control Unit used to manage Yazaki/CHAdeMO signals to establish the

communication between the vehicle and the station uses the signals read from the

BMS of the vehicle to drive the power unit by means of a PWM signal used to control

the level of the recharge current.



Dock Control GUI A GUI has been developed to monitor the status of the recharging procedure.

The GUI allows the user to monitor all the signals exchanged during the recharging

process such as:

• the level of current flowing in the battery pack

• the level of the achieved charge of the vehicle instant by instant.

The station is capable to record the acquired information.

Close-up of the fast recharge station display



Control Unit Subcomponents

The control unit is made up of two main subcomponents:

• An Arduino board performing CAN to RS232 conversion

• A Windows based PC platform.

The firmware for the Arduino board is written in C,

The monitoring software running on PC is written in Visual Basic.



The Recharging System

The Arduino board collects data from

the CHAdeMO CAN network,

listening the communication between

charger and vehicle.

Then, it forwards data to the PC in a

convenient form, through a serial

link.

The PC outputs data on the screen

for user visualization, and logs it to

files stored on the hard drive for later

analysis and processing



The developed recharge system implements the exchange of signals between the dock

and the vehicle as prescribed by the CHAdeMO protocol.

The developed infrastructure has been tested by using a Citroen C Zero.

A typical sequence of samples acquired by the dock during a recharge session is shown in

the graph where both current and voltage profiles are reported.



the current level during the nine minutes interval has been almost constant except for a few oscillations.

During the same slot of time the corresponding voltage increases of about 10 V being subject to some

ripple and showing some saturation.

Different assumptions need to be made regarding the charging infrastructure, rates and duration, battery

status, energy capacity, size and technology, HEVs type and mathematical approaches.

Results

Current Voltage

1. INTRODUCTION


3. EXAMPLES AND PROTOTYPES OF V2G TECHNOLOGY DEVELOPMENT

4. CONCLUSIONS

SUMMARY





Smart Charging System Optimization

The use of Optimization methods to find an optimized charging pattern can lead to

technical and financial results

According to preliminary calculations the

optimized patterns should be able to:

• reduce charging cost by about 51% for a

single isolated HEV,

• almost 40% for multiple coordinated vehicles

when penetration is higher.



A new Transportation System

The economical and financial incentives, given the actual HEVs market conditions,

could be a key driver to widespread the use of these technologies for a greener, integrated

and sustainable mobility.



Steps to promote a New Transportation System

Three steps can be identified to replace the not integrated heat-engine transportation

system and the actual power generation system:

1. The use, in the short term, of HEVs and EVs to promote high-value, time critical-

services regulation and spinning reserves.

2. The use of V2G technologies to support the penetration of intermittent renewable

energies sources using the battery storage capability of the vehicles.

3. It can be imagined a scenario where the V2G systems acts as distributed energy

provider connected to the smart grid.

These three phases require also the intervention of the regulatory authority to promote the

use of an efficient price schedule to incentivize the owners to respond according to

prevailing power system conditions.

Impact of V2G/G2V Technologies on Distributed

Generation Systems

G. Fabbri, G. Tarquini, L. Pasquali, L. Anniballi, S. Odoardi, S. Teodori, E. Santini

June 3 2014, Istanbul, TURKEY

END OF PRESENTATION

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