1-4 Training Electrical Engineers For Renewable … Electrical Engineers for Renewable Energy Challenges ... CoPEC ECEN 2060 Objectives and ... PV panels, battery, and inverter in

CoPEC

Training Electrical Engineers for Renewable Energy Challenges

Dragan MaksimovicECE DepartmentUniversity of Colorado at [email protected]

2IEEE PELS 2008 Symposium

CoPEC Background• Growing interest in Energy Engineering

Environmental and climate change concernsEnergy independence goalsA new frontier in Engineering: challenging problems, opportunities for innovation, entrepreneurship, and rewarding careers


CoPEC Background• Growing interest in Energy Engineering

Environmental and climate change concernsEnergy independence goalsA new frontier in Engineering: challenging problems, opportunities for innovation, entrepreneurship, and rewarding careers

9,212 solar panels, 1,600 kW solar power system at the Google campus, Mountain View, CA

http://www.google.com/corporate/solarpanels/home


CoPEC A New Frontier in Engineering• New Priorities: “for some job seekers, oil companies are out. Alternative-energy start-

ups are the place to be …” The Wall Street Journal, Oct. 29, 2007, p. R8 • “Greentech could be the largest economic opportunity of the 21st century,” KPCB

Venture Capital, http://www.kpcb.com/initiatives/greentech/index.html


CoPEC Training of Electrical Energy Engineers

• Electrical Engineering started as electric power engineering; up to 1970’s EE curricula were dominated by traditional electric power topics

• Over the last 30-40 years, the traditional electric power theme has diminished in EE/ECE programs

Mature technologyFewer research funding opportunitiesFewer attractive engineering career optionsRapid emergence of many other EE and ECE areas

• Electrical Engineering is now at the core of many existing and emerging green energy technologies

How should we (re)organize EE programs to address the growing interests, as well as current and anticipated needs?


CoPEC What is Electrical Energy Engineering?

• In the late 19th century Electrical Engineering started the revolution in generation, transmission and distribution of Electric Power

• In the 20th century, Electrical Engineering revolutionized Communication and Computing

Polyphase ac power distribution, and motors/generators based on rotating magnetic field

William Shockley, John Bardeen, Walter Brattain Transistor, Bell Labs, Dec 1947

2007 quad-core processor, more than 500 million transistors

Nikola Tesla

• 21st century Electrical Energy Engineering is all of the above, and more


CoPECElectrical Energy Engineering program

at CU Boulderhttp://ece.colorado.edu/~ecen2060/energyprogram.html

ECEN2060Renewable Sources

and Efficient Electrical Energy

Systems

ECEN3170Energy

Conversion

ECEN4797/5797Intro to Power

Electronics

ECEN4517/5517Power Electronics and

PV Systems Lab

ECEN4167Energy Conversion 2

ECEN5807Model. and Control of

Power Electronics

ECEN5817Resonant and Soft

Switch Tech. in Power Electronics

ECEN5017Conventional

and Renewable Energy Issues

Sophomore Junior Senior Graduate

+EE/ECE fundamentals:Circuits and microelectronics, semiconductor devices, IC design, EM fields, programming, digital logic, embedded computing, communications/DSP, control systems

Faculty:Frank Barnes, Robert Erickson, Ewald Fuchs, Dragan Maksimovic, Regan Zane



at CU Boulder

• New introductory sophomore-level course, first offered in Spring 2008• Spring 2008 enrollment: 31 students, 2 non-credit continuing education• Minimal prerequisites, strong technical contents• Instructors:

Dragan Maksimovic, Robert Erickson, and Regan Zane

http://ece.colorado.edu/~ecen2060/energyprogram.html



Systems

ECEN3170Energy

Conversion


Electronics


PV Systems Lab



Power Electronics







CoPEC ECEN 2060 Objectives and OutlineIntroduction to Electrical Energy Engineering

Improve generation Reduce consumption

Transmission, Distribution, Conversion

and Storage

Energy EfficiencyRenewable Energy Sources

• Photovoltaic power systems

• Wind power systems

• Energy efficient lighting

• Drives in hybrid and electric vehicles

• Understanding of electrical engineering fundamentals in renewable sources and energy efficient systems

• Practical knowledge of engineering design issues in system examples• Background and motivation for follow-up studies


CoPEC

• Introduction to electric power system

• Photovoltaic (PV) power systems

• Energy efficient lighting

• Wind power systems

• Hybrid and electric vehicles

ECEN 2060 Syllabushttp://ece.colorado.edu/~ecen2060

+

VDC

–

ia(t)

ib(t)

ic(t)

Q1

Q4Q2

Q3

Q6

øa

øb

øc

3øacQ5

Permanent-magnet

synchronousmachine

IDC

vab(t)+

–vA0(t)

vB0(t) vC0(t)

0

A

C

n T

+–

B


CoPEC ECEN 2060 Syllabus, Spring 2008• Electric Power System (4 lectures)

Electric utility industry, generation and consumption statistics, cost of electricity Overview of electricity generation: power plants and polyphase generators Transmission and distribution of electricity, the US electric power grids

• Photovoltaic Power Systems (16 lectures)The solar resource PV cell physics and efficiency limits, PV technologies, and PV cell electrical modelGrid-connected PV systems Power electronicsStand-alone PV systems and lead-acid batteries

• Energy Efficient Lighting (5 lectures)Lighting technologies, luminous efficiency and cost of lightingElectronic ballasts for discharge lampsSolid-state lighting and LED drives

• Wind Power Systems (10 lectures)The wind resource and efficiency limits, overview of wind turbinesWind turbine electrical systems: constant-speed and variable-speed architecturesAC machines3-phase power electronicsGuest lecture on wind turbine electrical systems and controls by Lee Jay Fingersh (NREL)

• Hybrid and Electric Vehicles (6 lectures)HEV power train architectures: series, parallel and series/parallelBatteries for HEV, PHEV and EVVariable-speed AC drivesOperation and sizing of system components


CoPEC ECEN2060 topic example: PV systems

ACutilitygrid

iac

+

−

vac

+

−

VPV

IPV

PVarray

Single-phaseDC-ACinverter

+

−

VDCC

Inverter controller

DTs Ts

LiL

MPPT controller

Cpv

idc

vgate

it

vt

+

−

+ −vL

Grid-tie PV power system example

• What is it and how does it work?• Basic physics• Operation and engineering of system components• System engineering and economics


CoPEC (1) Fundamentals of PV technology

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0 500 1000 1500 2000 2500

Wavelength [nm]

Pow

er d

ensi

ty p

(lam

bda)

[W/m

^2/n

m]

AM1.5Ideal photovoltaic output

∫ ∫∞

===0 300

2max

W/m490)()(λ

λλλλnm

pvpvPV dpdpI

Photoelectric output power (ideal):

%49max ==S

PV

II

η

PV cell

+

_

Rs

RpVD

IDISCVPV

IPV

• Basic semiconductor and PV cell physics; limits of efficiency

• Overview of PV technologies, crystalline Si, thin film, etc

• PV cell circuit model and characteristics

Full sun: 1,000 W/m2


CoPEC (2) PV modules and arrays

ACutilitygrid

iac

+

−

vac

+

−

VPV

IPV

PVarray


+

−

VDCC

Inverter controller

DTs Ts

LiL

MPPT controller

Cpv

idc

vgate

it

vt

+

−

+ −vL

0 50 100 150 200 2500

1

2

3

4

5

6

7

8

9

10

Vpv [V]

Ipv

[A]

1

2

3

0 50 100 150 200 2500

200

400

600

800

1000

1200

1400

1600

Vpv [V]

Ppv

[W]

• Module and array characteristics

• Maximum power point (MPP)

• Effects of shading

Ipv [A]

Vpv [V]

Ppv [W]

1,000 W/m2

(uniform)

900 W/m2

(partial shading)

200 W/m2

(uniform)

Characteristics of an array of twenty 75 Wp modules (36-cell each) in series

Vpv [V]


CoPEC

0 50 100 150 200 2500

1

2

3

4

5

6

7

8

9

10

Vpv [V]

Ipv

[A]

1

2

3

(3) PV power electronics

ACutilitygrid

iac

+

−

vac

+

−

VPV

IPV

PVarray


+

−

VDCC

Inverter controller

DTs Ts

LiL

MPPT controller

Cpv

idc

vgate

it

vt

+

−

+ −vL

• Basic operation of DC-DC converters and DC-AC inverters

• Overview of power semiconductor switches

• Basic averaged models and efficiency analysis

+

−

VPV

+

−

VDC

1−D : 1IPV IoutRL

Isw

Ipv [A]

Vpv [V]

Boost DC-DC converter averaged model

Boost DC-DC waveforms

Boost DC-DC efficiency analysis in

the PV system

Grid-tie PV system using Boost DC-DC MPP tracker

%96=boostη

%92=boostη

%92=boostη


CoPEC (4) PV system controls

• Perturb and observe maximum power point tracking algorithm

• DC-AC inverter controls• DC bus voltage control• AC grid current shaping;

unity power factor

Initialize Iref, ΔIref, Pold

Measure Ppv

Ppv > Pold ?

Iref = Iref +ΔIref

ΔIref = −ΔIref

Pold = Ppv

Continue in the same direction

Change direction

YES NO

0 1 2 3 4 5 60

50

100

150

200

250

300

350

400

450

500

Ipv = Iref

MPP

Ppv


CoPEC (5) PV system design and economics

ACutilitygrid

iac

+

−

vac

+

−

VPV

IPV

PVarray


+

−

VDCC

Inverter controller

DTs Ts

LiL

MPPT controller

Cpv

idc

vgate

it

vt

+

−

+ −vL

• Solar resource• System sizing and

basic economics• Example: a grid-tie

system in Boulder• Average of 5.5

hours or full sun • 1 Wp (Watts peak)

installed produces about 1.5 kWh per year

• Cost: about $8/Wp (excluding incentives)

kWhm2 day

US “hours of full sun” map

Insolation data: http://rredc.nrel.gov/solar/codes_algs/PVWATTS/


CoPEC ECEN2060 observations

• Energy systems rich in EE contents (e.g. PV, Wind, Hybrid and Electric Vehicles) are great motivators for students in an introductory class

• This is not just a survey class: it is possible to introduce electrical energy engineering topics in significant technical depths even in an introductory class

Basic physics, materials and componentsPower electronics and electric machinesSystem controls, system design and economics

• Curriculum revisions are under way to open space for attractive introductory courses such as ECEN2060 at the sophomore level



at CU Boulder

• Major course revision in Spring 2008• Spring 2008 enrollment: 33 undergraduates, 11 graduate students• Objectives: hands-on design and project experience• Instructors:

Robert Erickson, Regan Zane and Dragan Maksimovic

http://ece.colorado.edu/~ecen2060/energyprogram.html



Systems

ECEN3170Energy

Conversion


Electronics


PV Systems Lab



Power Electronics







CoPEC

The course begins with basic experiments on:

• Photovoltaic power systems

• Power conversion electronics

The course then culminates in a design project involving photovoltaics and power electronics

A basic standalone PV power system in the ECEN 4517 laboratory

PV panels, battery, and inverter in the ECEN 4517 laboratory

PVPanel

85 W

Battery

Deep-dischargelead-acid

12 V, 56 A-hr

Inverter

120 V 60 Hz300 W

true sinewave

Charge control

DC-DC converterfor maximum powerpoint tracking and

battery charge profile

ACloads

DC loads

Digital control

ECEN4517/5517Power Electronics and PV Systems Lab

http://ece.colorado.edu/~ecen4517


CoPEC ECEN4517/5517 Syllabus

1. Basic PV system elements (1 week)2. Basic converter control circuitry and pulse-width modulator

(1 week)PV

+

–

+

vbatt

–

Buck converter

Pulse-widthmodulator

High sidegate driver

ibatt+

vpv

–

Microcontroller

Sensors

Bootstrappower supply

Peak powertracking and

batterychargecontrol

C1

L1

C2

Batterycurrent and

voltageExperiment 3

3. Battery charge controller and PV peak power tracker using a DC-DC buck converter (3 weeks)

4. Inverter system (3 weeks)5. Project (6 weeks)

ECE Expo

12 VDC HVDC: 120 - 200 VDC

AC load120 Vrms60 Hz

Battery

DC-ACinverter

H-bridge

DC-DCconverter

Isolatedflyback

+–

d(t)

Feedbackcontroller

Vref Digitalcontroller

d(t)

+

vac(t)

–

Experiment 4


CoPEC Portable PV carts• 85 W PV panel that can be

wheeled outside• Deep discharge lead-acid

battery and 300 W inverter to power test equipment

• Auxiliary DC power supplies for control circuitry

• One cart per bench, 10 total

PV panel85 Wpk

17.2 V at 4.95 AShell SQ-85P

Con

nect

ors

+

–

PVpanel

+

–

Battery

+

–

Isolateddc-dc

converters

+– 12V, 1A

+– 12V, 1A

+– 5V, 2A

Inverter60 Hz 300 W

120 Vrms

6 outletac power strip

AlarmBattery low voltage

VoltmeterBattery voltage

Batterycharger

Battery12 V

deep-discharge56 A-hr

Off cart:on stationary workbench

Ds

Cart schematic

PVPanel

85 W

Battery

Deep-dischargelead-acid

12 V, 56 A-hr

Inverter

120 V 60 Hz300 W

true sinewave

Charge control

DC-DC converterfor maximum powerpoint tracking and

battery charge profile

ACloads

DC loads

Digital control


CoPEC Experiment 1, Jan. 22-24, 2008


CoPEC ECE Expo, May 1, 2008

MPP tracker based on digitally controlled Cuk

DC-DC converter(April 26 College of Engineering Expo)

Electronic ballast for fluorescent lamps

Cascaded boost DC-DC

converter (battery to high-

voltage DC conversion)

20 projectsin power electronics

for PV or energy efficiency


CoPECResearch Program

Colorado Power Electronics Center (CoPEC)

Energy Efficiency Power Electronics for

Renewable Energy

Energy Harvesting

Smart Power Electronics Technology

• Analog, mixed-signal and digital control techniques• Mixed-signal integrated circuits for power control• Converter modeling and design

Switched-mode power supplies

Lighting Power for RF systems

• PFC• Isolated DC-DC• POL DC-DC• Multi-phase• Low-power

Medical systems

• Ballasts• LED

drives

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Ipv, Vpv

ConverterPV

ControllerIpv, Vpv

Inverter 60 Hz ACUtility

13 sponsoring companies, 25 graduate students, Faculty: R.Erickson, D.Maksimovic, Z.Popovic, R.Zane


CoPEC Conclusions• Electrical Energy Engineering at CU Boulder

EE/ECE fundamentals + materials/devices + systems + economicsMore interdisciplinary than other EE areasEmphasis on technical and engineering fundamentals, even in introductory courses with minimum prerequisitesMotivated students

• Department strengths and new initiativesEnergy is a major area of emphasis in the ECE DepartmentCoPEC research program: very strong industrial supportRelated strengths in control systems, remote sensing, materials and devices, RF/microwave electronicsCU/CSU/CSM/NREL CREW: Colorado Renewable Energy Collaboratory Center for Research and Education in WindCampus-wide energy initiative

Documents

1-4 Training Electrical Engineers For Renewable … Electrical Engineers for Renewable Energy Challenges ... CoPEC ECEN 2060 Objectives and ... PV panels, battery, and inverter in