Mutlu BOZTEPEAfyon_sunum2015

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Assoc. Prof. Dr. Mutlu BOZTEPE

Ege University, Department of Electrical and

Electronics Engineering

Impact of Power Electronics

on Renewable Energy

Systems

4rd Renewable Energy Systems Winter School

15-18 January 2015

http://www.reswinterschool.com



Outline

Introduction to renewable energy sources

Need for power processing

Power electronics

Impact of power electronics

in wind energy systems

in photovoltaic systems

in utility power grid

Wide bandgap materials Conclusion

4rd Renewable Energy Systems Winter School, 15-18 Jan. 2014 2



Introduction to Energy Sources


(Past) (present) (future)

Solids Liquids Gases



Energy per capita vs. income per capita


G D P : G r o s s N a t i o n a l I n c a m e

P e r c a p i t a i n c o m

e



World primary energy productions


1980 2009 2010 2040

Liquid fuels %46.2 %34.6 %34 %28

Coal %24.7 %27.6 %28 %27

Natural gas %19 %23.4 %22 %23

Nuclear %2.7 %5.7 %5 %7

Renewable energy %7.4 %8.6 (%16 rise) %11 (%27 rise) %15

Oil is still the mainenergy source. Renewable energyfraction increases yearby year. Most importantly;

Energy consumptioncontinue to increasesteadily.



Fossil fuels and environmental issues

Global warming,

Environmental pollution,

Acid rains,

Air pollution




General Trends

Energy consumption increases

More people (born, longer lifetime etc.)

More equipment

Higher living standard

More production But global sources are limited

Climate change a global issue

Therefore we need, new power sources (Renewable!)

efficient usage of existing sources

Energy efficient devices




Source of energy

There are five ultimate primary sources of useful energy:

The Sun

The motion and gravitational potential of the Sun,

Moon and Earth

Geothermal energy from cooling, chemical reactions

and radioactive decay in the Earth

Human-induced nuclear reactions

Chemical reactions from mineral sources (Oil, coal,natural gas, etc.)


Renewable vs. non-renewable



Renewable vs. non-renewable


Renewable Energy:unlimited rezerveNot be depleted

Non-renewable Energy:Limited rezerveCan be depleted.



Natural energy currents on earth


Units terawatts (1012 W)



Mostly known renewable sources

Solar energy

Wind power

Tidel power

Wave energy

Hydroelectric sources.

Biomass

Jeotermal energy

…




Electric power theory


Direct Current (DC)

Alternating Current (AC)



Apparent, Active and Reactive Power




RMS value = Effective value

RMS=Root Mean Square




Electricity Generation and consumption

DC power

Photovoltaic generator

Fuel cell generator

Thermoelectric generator

Dynamo

AC power Synchronous generator

Permanent magnet synchrounous

generator

Induction (Asynchrounous) generator

Squirel cage induction generator


We need to process power!Solution is Power Electronics

Loads

12V, 24V, 48V… DC loads

120Vac, 230Vac AC loads

Resistive, reactive loads

Variable loads

50Hz, 60Hz AC power

…



What is power electronics?

Power electronics is a branch of engineering that combines the

generation, transformation and distribution of electric energy throughelectronic means. (Kevin Bai)

Power electronics is the application of solid-state electronics for the

control and conversion of electric power. (Wikipedia)

In broad terms, the task of power electronics is to process and control

the flow of electric energy by supplying voltages and currents in the

form that is optimally suited for user loads. (Mohan et.al.)

Power electronics combine power, electronics and control. (M.Rashid)

Power electronics is the application of static converters to process and

control the electric energy. (Hacı Bodur) Power electronics circuits convert electric power from one form to

another using electronic devices. Conversion is done using electronic

switches, capacitors, magnetics, and control systems (Daniel Hart)




Interdiciplinary nature of Power Electronics




Relation with other disciplines


PowerElectronics

Circuittheory Solid-state

physics

Simulationand

computing

Electricmachines

Powersystems

Electromagnetics

Electronics

Signalprocessings

Controltheory

Power electronics is currently the most active discipline in electric powerengineering



Scope of power electronics

Applications of power electronics range from high-power conversion

equipment such as dc power transmission to everyday appliances, such ascordless screwdrivers, power supplies for computers, cell phone chargers,

and hybrid automobiles.


Power Level Example System

0.1-10 W Battery operated equipment

10-100 W Satellite power systems, Offline flyback power supply

100-1 kW Computer power supply, Blender

1-10 kW Electronic welding machine

10-100 kW Electric car, Eddy current braking

100kW-1 MW Micro-SMES (Superconducting Magnetic Energy Storage)

10MW-100 MW Magnetic aircraft lunch, Big locomotives, Power distribution

100MW-1 GW Power plant

>1 GW High Voltage DC Transmission (HVDC)

mi l i W a t t

G i g a W a t t



PC ATX power supply




Induction heating




Microprocessor voltage regulator




Maglev Train




Electric car




Renewable energy




Smart grid

Electricity grid involves more and more power electronics.

Penetration rate of non-stable renewable power sources into future grid

can be increased only with smart control strategies by using suitable

power electronics equipments.




Conversion clasification

According to power conversion type:

– AC input - AC output (rectifier)

• Full wave rectifier

– DC input - AC output (inverter)

• 220VAC/50Hz inverter with battery input

– DC input - DC output (converter)

• Voltage regulator

– AC input - AC output (converter, cycloconverter)• Dimmer, speed control of induction machine

According to the power flow direction

– Unidirectional

– Bidirectional




Photovoltaic MPPT controller


DC/DC converter input impedance can be altered by using

the “control” input


VPV

ISC

IPV

VOC

R1

R2

R3



How bypass diode affects the P-V curve?


Shaded unshaded.

Without bypass diode



Distributed MPPT concept


DC/DCconverter

DMPPT is proposed as a solution topartial shading problem



Grid Connected Photovoltaic System


•DC/AC inverter

•MPPT tracking eff.>%99

•Power eff. >95%

•Islanding

•Low THD



Stand-alone PV system


DC/DCconverter

DC/ACinverter



Wind power systems





Blade types vs. rotor eff.

00

1

u

Rw

u

v

For maximumrotor efficiencytip-speed ratioshould be keptcontstant atmaximum rotoreff.

tip-speed ratio



Fixed speed wind turbines


Blade rpm is proportional

to the syncronousgenerator (SG) shaft rpm

via gear box.

SG shaft rpm is

proportional to gridfrequency via number of

pole of SM.

So, even if wind speed changes, the turbin rpm is constant thatreduces turbin rotor efficiency.

Not an efficient system



Fixed speed wind turbines


Squirrel cage induction generator is connected to the

grid via soft-starter in order to reduce inrush current.

Less efficient. Fixed speed operation reduces rotor

efficiency (Cp factor).

Cheap and robust



Variable speed wind turbines


Doubly Fed Induction Generator (DFIG) has wound rotor

DFIG can operate at variable speed (30% slip variation) .

Pitch control enables to keep the tip-speed ratio at

optimum value.

AC/DC/AC converter supply exitation current

Use slip rings which requires maintanence



Variable speed wind turbine


3 types of generator can be employed.

Syncronous generator

Permanent magnet generator

Squirrel cage induction motor

With/without gear box

AC/DC/AC converter process all power generated.



Power system voltage levels

Traditional power systems uses transformers to change voltage level.

Disadvantages:

No voltage regulation

No reactive power compensation

No power control flowing on through

Heavy, Large

Expensive




Future power grid

Use DC and AC

Distributed power

generation

Bidirectional

power flow Low loss

High flexibility

Adaptive Islanding mode on

failures


Smart grid!



Solid State Transformer (SST)

Solid state transformer has

been gained remarkableattention due to;

Regulates voltage,

Compensates reactive power

Control of active power Smart control features

Bi-directional power flow

Light, and less volume

Limitations

Expensive

Sightly low efficiency

Reliability need to be tested


SST includes high frequency transformerand power electronic circuits



Cascade connection




SST topologies




Power semiconductors




History of power electronics


Mercury arc rectifier

Vacuum-tube rectifier

Thyratron

Invention of

Power MOSFET andPower BJT

Invention ofThyristor

1900 1957 mid 1970s late 1980s

Pre-history 1st phase 2nd phase 3rd phase

Power diodeTyristor

GTO

Power MOSFET

Power BJTThyristor

(microprocessor)

Invention of

IGBT

IGBT

Power MOSFET

Thyristor

(DSP)



Wide bandgap devices

Silicon Carbide (SiC)

Aluminum Nitride (AIN)

Ultraviolet leds

Gallium Nitride (GaN)

LEDs and Lasers

Silicon devices are able to

reach 10 kV

WB devices operate much

higher voltage, frequency

and temperature than

conventional Si.




Advantages of SiC over conventional Si

Compared to Si, SiC has;

Ten times the breakdown voltage Three times the bandgap which means can operate at higher temperature

Guaranteed operation temp 150°-170° depending on the package. If it is properly

packaged temp can be higher than 200°

Three times the thermal conductivity

Very low resistance

Sic Mosfet has very fast switching speed




SiC Mosfet vs. Si Mosfet

Existing Si super junction MOSFETs are only available for

breakdown voltages up to around 900V. SiC-MOSFETs have breakdown voltages up to 1,700V or higher

with low on-resistance




SiC IGBT vs. Si IGBT

Total Power Loss Comparison of 1.2kV / 10A SiC

DMOSFET vs. Si IGBT (IRG4PH40KD)

Si IGBT Is Impractical at High Frequencies




Dramatic

Increase inEfficiency of 3-

Phase Solar

Inverter Using

1200V SiC

DMOSFET


d d h i i



Vd-Id characteristics

Since SiC-MOSFETs have no threshold voltage (knee) as IGBTs, they have a low

conduction loss over wide current range.

Si-MOSFETs’ on-resistance at 150°C is more than twice that at room temperature,

whereas SiC-MOSFETs’ on-resistance increases only at a relatively low rate.

This facilitates thermal design for SiC-MOSFETs and provides low on-resistance at high

temperatures


SiC di d i i li ibl



SiC diode reverse recovery time is negligible


10 kV 100 A SiC MOSFET M d l



10 kV, 100 A SiC MOSFET Modules

9% Weight and 12% Volume vs IGBT module




Incresed switching frequency reduces size of

transformer


T d t h l i Si IGBT



Today technology using Si IGBT.

60 Hz Transformer is required for Interconnection to 13.6 kV

Distribution Grid


Mutlu BOZTEPEAfyon_sunum2015

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