E. F. Piene, "Grid Connected Vehicles Capabilities and Characteristics," in Electric Vehicle...

transcript

Egil Falch PieneTHINK Global AS

Norway

Grid connected vehicles

Capabilities and characteristics

EES-UETP Course title

Course date 22 September 2010

Course place DTU Lyngby, Copenhagen

History

• Founded 19 years ago in Norway

• The first prototype predecessor to today’s modern

THINK City was developed in 1991

• The first generation THINK City was produced

from 1999-2003

• Ford Motor Company owned and invested heavily

in THINK between 1999-2003

• In 2006 Norwegian investors bought THINK and

have invested over $120 million to further develop

the latest generation THINK City

• Production moved to THINK’s strategic partner

and shareholder, Valmet Automotive of Finland,

in late 2009

EV design requirements

1. Optimize for energy efficiency and range

2. Optimize for cost and driving performance

3. Optimize for basic and sneaky design

4. Optimize for grid conditions and battery life

Think is doing "practical innovation"

Scope of this presentation

• Description of system in an electric car

conductively connected to the grid, with

AC transferred to an on-board charger

• Highlight some specifics for systems

integration, with focus on the modules

involved in the charging process

• Briefly discuss regulation services from a

user and vehicle perspective

Questions in mind

• What will be needed to prepare for the

charging infrastructure, so the grids can

supply many simultaneously connected

• Are the vehicles being designed well

enough, so when many connected they do

not aggravate conditions in the grids?

Block diagram of modules

COML1L2L3N

ChargingStation

Vehicle CANCOM

On-boardCharger

TractionBattery

VehicleController

DCACAC

Grid side Vehicle side

AC-charging from a 1-phase or 3-phase source

• Typical for plug-ins today, is that they

charge with the power available, without

taking care of other loads or even any

other grid condition

• The vehicle charger system and the user

takes for granted that there are energy

and grid capacity available

Plug-in vehicles today

Courtesy of BRUSA www.brusa.biz

Gain of 80% State of Charge

Battery size: 25 kWh

Total efficiency: 80%

Charging time versus interface

km/charge-hourSource Transfer EV * PIHV Th!nk City

• 230V 1ph 16A 3.6kW 18 7 17 (3,2kW)

• 400V 3ph+N 16A 11kW 55 - 51 (9,6kW)

• 400V 3ph+N 32A 22kW 110 - -

• 400V 3ph+N 63A 44kW 220 - -

• 690/400VAC ** DC 50kW 250 - TBD

* Example: General EV with ca 200 Wh/km consumption, "Plug-to-Wheel"

** CHAdeMO

Power x time = km

>400 Wh/km 190 Wh/km

On-boardCharger

Block diagram of modules

COML1L2L3N

Off-board

ChargingStation

Vehicle CANCOM

Power relaycontrol unit

TractionBattery

VehicleController

Grid side Vehicle side

DC-connected from an off-board charger, bypasses the AC on-board charger

Front - end

• Charging station

– Provide energy

– Electrical safety

– Forward available

maximum current

– Link communication

– Metering energy

– Payment

– IEC/EN 61851-1

with sub standards

• Today's Li-ION

traction batteries

– 90 - 130 Wh/kg

– 150 - 200 Wh/l

– 450 - 600 $kWh

• Battery pack size for

an usable EV

– 15 - 40 kWh

– 150 - 400 kg

EV battery monitoring system

• BMS is a highly integrated module with

specific software

• Protection for overload, overcurrents,

overheat, overcharge

• Doing measurements and calculations

• Taking care of cell balancing

• HV isolation monitoring towards chassis

• Diagnostics and communication

On-board Charger

• The input voltage range shall without any

configuration, cover the voltages available

in all domestic power systems

Input voltage range

• Japan = 100 V to UK = 240 V ±10%

• which give 90 - 264 V + margin

• which give ≈ 85 - 275 V

• @ 50 - 60 Hz

Output voltage range

• The output voltage range need to match

the on board traction battery system

• Li-ION cells may have voltages varying

from 2.5 to 4.2V - depending its state of

charge (SOC)

• A modern EV will typically have (ca) 100

cells in series, which gives an operating

voltage range of 250 to 420V

- further properties

• Efficiency as high as possible

• Power output as linear as possible

• Conducted noise as low as possible

• Galvanic isolation (grid to traction battery)

• Power factor correcting

• Must respond to a control signal

• Light weight

• Automotive requirements *

HE rectifier circuits

Primary side

DSPSecondary side DSP

SPICAN

Transistor

drive signals

DC out

Transistor

drive signals

Courtesy of ELTEK VALERE www.eltekvalere.com

HE rectifier efficiency

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

HE rectifier

Standardrectifier

Energy consumption and loss

• Assumptions– 25 kWh battery with 5% internal system loss

– 3 kW on-board charger

– Average daily depth of discharge 60%

– 240 commute days pr year

• Energy delivered to battery– Per day: 25 kWh x 0.6 x 1.05 = 15.75 kWh

– Per year: 15.75 kWh x 240 = 5 749 kWh

• On-board charger conversion losses– 90% efficiency: 420 kWh per year

– 95% efficiency: 199 kWh per year

• Energy saved pr year: = 221 kWh

Power factor correction & noise

• Power supplies sold and used in Europe must be compliant to the below standard, which sets the limits for grid current harmonics (up to 2 kHz)

• For power supplies larger than ca 250 W, active power factor correction is necessary to reduce feedback of harmonic currents

EN 61000-3-2

Grid current harmonics

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39

Harmonic number

pere Measured harmonics

EN61000-3-2 limits

1. Harmonic (50 Hz)

Measurements from a 3 kW unit @ 230 V

Automotive requirements

• Vibration resistive

and mechanical

stability

• Wide temperature

• Efficient cooling

• Sealed enclosures

and connectors

• High voltage

isolation

Single loop charging regulation

• In a traditional battery charger circuit, the

regulation is based on the battery's need

COML1L2L3N

ChargingStation

Vehicle CANCOM

On-boardCharger

TractionBattery

VehicleController

Effects of negative impedance

• If the grid voltage drops, a connected

charger with single loop regulation would

increase the input current to maintain a

constant current or power output

• The increased input current will represent

a heavier load that may even drop the

voltage further down

• The max current allowed from the charging

station, must be registered by vehicle

AC current regulation loop

• An EV prepared for Smart Charging would

need one additional regulation loop

COML1L2L3N

ChargingStation

Vehicle CANCOM

On-boardCharger

TractionBattery

VehicleController

Coincidence factor

• If standardization for protection against

charger’s negative impedance is not

solved in the vehicle systems, a smart grid

signal could make control of distributed

• When dimensioning charging facilities for

fleets or many vehicles, the coincidence

factor would need to be carefully assessed

Balancing 3-phase

• Phase individual loads can by achieved

by the use of three single charger units

• Separate voltage measurement and

control

• Power 10 kW

• Redundancy

• Single phase

configurable

Statement

Ph.D. Lars Henrik Hansen

Questions in mind 2

• How can plug-in

vehicles develop from

only being a load and

become a medium for

regulation services?

• What alternatives are

here now?

Regulation capable or not

• Dumb chargingPlugging in whenever

and wherever

• Timer chargingPlug in, but no charge

until assumed valley

• V2GIn control from the

grid operator

• Smart ChargingIn control from the

grid operator or other

source

The sceptics response to V2G

• Uncertainty regarding the market for regulation

• New regulation technologies are emerging

• Which user incentives, "cash-back" only and

how will it be influenced by the volume of cars?

• User applicability, hence adaption, how combine

grid regulation with the need for driving range?

Smart charging scheduler

• Smart phone apps,

plan for the next drive

• Not only as the

control instrument for

the user,

• but as well a way of

spreading the

information towards

modern times for

greater concerns

about energy

consumption

Automakers V2G response

• Culture of designing machines for

transportation, not for storing electricity

• New technology, few standards

• Long time for development and validation

• Which battery life impact?

• Warranty aspects with battery system

• Safety for electrical hazards, liability issues

• Extra cost on the vehicle

• Different and new business models

Capacity retention

General impacts on Li-ION life

• High temperatures (> ≈ 55 C)

• Too heavy charge or discharge at low temp

• Too heavy charge or discharge at low SOC

• Too heavy charge or discharges

• Full or deep discharge cycles

• Storage empty (self discharge)

• Time

Charging efficiency, vehicle

Full V2G, not yet...

• Imperative that the owner of vehicle doesn’t

suffer an economic loss due to accelerated

retention of the battery

• Economic incentive must cover battery

system wear and degradation

• Warranty and legal aspects must be

transparent

• Comprehensive ‘Cash Back’ model is

needed for EVs and PHEVs

For realisation now is V2G light

• Providing regulation

up and down

according to a

scheduled middle

charge rate

• Vehicle should be in

daily use, as

regulation service

would be possible only

while charging up

• The battery will not be

worn more than in a

regular operation

• Less losses in both

LV-grid and vehicle

• Setup will probably

require more vehicles

in the pool, to provide

the same grade of

regulation compared

to real V2G

Control through infrastructure

• Control signal from

grid operator through

a fixed line

• Wireless not regarded

suitable for faster

response demands

• Local fleet servers for

power or time share

depending the local

capacity and number

of vehicles connected

and counting energy

metering data

• Aggregation server to

collect load data and

provide control signal

• Standardized protocol

- more "V2G light"

• Target for charge rate

response time

less than 3 sec

• Aggregator to control

charging rate within

predefined limits

• Not only for fleets, the

system can possible

be general available

• The vehicles would

need a small extra

communication unit

• The charging station

would need to be

connected "on-line"

• The user would need

a scheduler via web

or in a phone-app

Added autonomous regulation

• In case the communication is lost,

– the vehicle charger system could enter an

autonomous mode, by providing regulation

with a fraction of the scheduled charge rate

with response to the line frequency

– a preset charge rate according to the

average daily/hourly load profile could work

as a back up and make the control

– The user would be notified via the phone-app

scheduler and still have the option to override

Local storage, regulation, solar, wind,

and fast EV-charging

Main battery10 x Na-NiCl, Z36

U-nominal = 370V DC

P-nominal = 250 - 500kWh

P-peak = 500 - 1000kW

Grid inverter4 x,150kWpeak, bidirctional

Frequency 50Hz

Switching frequency 24kHz

with external prefilters

LV Grid

3 x 400 VAC+N

350 V DCDirect connection to the vehicle

2 to 3 charging spots

250A capability (87W)

DCDC-converterBidirectional, no isolation

Switching frequency 48kHz

Photovoltaic panelMPP-Voltage up to 300V

20kWpeak

Courtesy of BRUSA www.brusa.biz

2nd life EV batteries

E. F. Piene, "Grid Connected Vehicles Capabilities and Characteristics," in Electric Vehicle...

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