Trends in-power-electronics

Trends in Power ElectronicsLecture delivered at ATME College of Engineering, Mysuru

R S Ananda Murthy

Associate ProfessorDept. of Electrical & Electronics Engineering,

Sri Jayachamarajendra College of Engineering,Mysuru 570 006

10 March 2017

R S Ananda Murthy Trends in Power Electronics

Specific Learning Outcomes

At the end of this lecture, the student should be able toState the goal of power electronics.Describe some important applications of power electronics.List major professional bodies and conferences related tothe field of power electronics.List important journals related to the field of powerelectronics.List important companies related to the field of powerelectronics.Mention some of the recent trends in the field of powerelectronics.


Fuel Shares of Primary Energy Supply

Oil 32.8 %

Coal27.2 %

*Other 0.8 %

10.2 %Biofuels

2.3 %Hydro

5.8 %Nuclear

Natural Gas20.8 %

Hydro 1.4 %Nuclear 0.7 %

Natural Gas7.2 %

Oil 23.6 %

Biofuels 24.5 %*Other 0.3 %

Coal42.3 %

Source: International Energy Agency (IEA)


Graph of Depletion Function of Fuels

1900 1950 2000 2050 2100 2150 2200 2250 2300

Coal

OilNatural Gas

Uranium0

Ene

rgy

Pro

duct

ion

in J

oule

s1.2

1.0

0.8

0.6

0.4

0.2

x 1018

Years

Depletion Function:

, , are constantsfor a particular type of fuel.


Hazards Caused by Burning of Fossil Fuels

Ozone layerdepletion

Global warmingCombustionof fossil fuels

Acid rain Photochemicaloxidants (Visibility)

Fine InorganicParticles

Health effects

Volatile OrganicCompounds

We need to reduce consumption of fossil fuels because itcauses environmental pollution and health hazards.Therefore we have to harness energy needed fordevelopment from other sustainable sources like solar andwind.


Higher Energy Efficiency Saves Fuels

G

TurbineSteam

PowerLoss

%

PowerLeft%

65 35

100 %

2.5 34.1

1.2 33.7

Step-upVoltage to

TransmissionLevel

Step-downVoltage to

Sub-transmissionLevel

1.6 33.2

2.5 32.4

Step-downVoltage toDistribution

Level

IM

2.0 31.7Switchgear

Induction Motor

Pump

12.0 27.9

40.0 16.7

Generator

Efficiency

Overall efficiency:

This shows that every kWof output power savedresults in a saving of 6 kWof fuel power at thegenerating site.


What is Power Electronics?

Power electronics is the technology associated withefficient conversion and control of electric power by usingpower semiconductor devices.Power electronics encompasses the use of electroniccomponents, the application of circuit theory and designtechniques, and the development of analytical tools towardefficient electronic conversion, control, and conditioning ofelectric power. — Definition given by IEEE PowerElectronics Society.


Goal of Power Electronics

Efficient conversion, conditioning, or processing andcontrol of electric power using solid-state semiconductordevices in order to supply high quality power to the loadcausing minimum pollution of environment and the utilitysupply circuit.


Block Diagram of a Power Processor

Converter

Control Circuitor

Triggering Circuit

ControlSignals

Reference

Feedforward

Feedback

RawElectrical

Power

OutputElectrical

Powerin the FormRequired by

Load

Converter has power switching semiconductor devices andenergy storing elements like inductors and capacitors.Resistive elements are avoided in converters because theycause power loss and reduce efficiency.Controller switches on/off the switching devices present inthe converter.


Example of a Power Processor

Converter 1

Controller Controller

Converter 2

A.C. supply

fixed voltage

at 50 Hz

or 60 Hz

A.C. supply

variable voltage

and frequency

A.C.

motor

−

+

Power processor

CD.C.

A.C. A.C.

A power processor may have more than one stage ofpower conversion.


Types of Converters

Symbol

Rectifier

Input Output

A.C. atconstant voltageand frequency

D.C. atvariable voltage

InverterD.C. at

constant voltage

A.C. atdesired voltageand frequency

ChopperD.C. at

constant voltageD.C. at

desired voltage

CycloconverterA.C. at

constant voltageand frequency

A.C. atdesired voltageand frequency

A.C. VoltageController

A.C. atconstant voltageand frequency

A.C. atdesired voltage

and input frequency

Converter Type

ACVC


Power Electronics Vs Signal Processing

In Power Electronics —The focus is on power conversion at the highest possibleefficiency using very small control signals.Semiconductor devices work as switches.Power handled may range from a few watts to severalmega-watts.

In Signal Processing —Semiconductor devices generally work as controlledsources in the linear region of their characteristics.The focus is on information processing with minimum lossof information.Power handled will be of the order of few milli-watts or fewwatts.


Multidisciplinary Nature of Power Electronics

PowerElectronics

ElectricalMachines

PowerSystems

CircuitTheory

Solid StatePhysics Signal

Processing

Systems andControl Theory

AnalogElectronics

DigitalElectronics

Simulation andComputing

Electromagnetics

Microcontrollers


IEEE Power Electronics Society

IEEE Power Electronics Society is a very important society ofprofessionals in the field of Power Electronics.


Power Sources Manufacturers Association

PSMA publishes The Power Technology Roadmap Reportwhich is an indicator of state-of-art in power electronics

industry.


Applied Power Electronics Conference (APEC)

Very major Power Electronics Conference which hasparticipants coming from all over the world.


Publications related to Power Electronics

IEEE Transactions on Power ElectronicsIEEE Power Electronics LettersIEEE Power Electronics MagazineIEEE Journal of Emerging and Selected Topics in PowerElectronicsIEEE Transactions on Transportation ElectrificationIEEE Electrification Magazine

Refer to the above mentioned publications to keep in touch withthe latest developments in the field of Power Electronics.


Major Areas of Application of Power Electronics

Motor Drives and ActuatorsIllumination EngineeringEnergy Efficient Power SuppliesSustainable Energy SystemsVehicle and Transportation SystemsPower and Control Core Technologies


Affinity Laws of Hydraulics

Affinity Laws are applicable to pumps and fans. Accordingto this law, at a given diameter of the impeller,

Q1

Q2=

N1

N2;

H1

H2=

(N1

N2

)2 P1

P2=

(N1

N2

)3

;

where Q is the flow, H is head, P refers to the power and Nis the speed of the pump or fan.Keeping the speed constant, the flow can be controlled byusing a valve or a damper. Then, as per equation givenabove, the power remains constant even at reduced flow.This is not an efficient method of reducing the flow.


Variable Speed Drive Saves Power

Suppose, to reduce the flow by 50 %, if we decrease thespeed by 50%, then,

Q1

Q2=

N1

N2=

12

; andP1

P2=

(12

)3

=18

which shows that the power is reduced by a factor of 8 ifthe speed is decreased by a factor of 2.This is more energy efficient than using a valve or adamper.But this requires a variable speed drive.


Why A.C. Drive?

Most of the industrial pumps and fans are driven bythree-phase induction motors.The rotor speed of three-phase induction motor is given by

N2 =120f1

P1(1−s)

where f1 is the stator supply frequency, P1 is the number ofpoles in the stator rotating magnetic field, and s is the slip.This shows that the speed can be controlled smoothly bychanging the frequency of the supply given to the stator.


Block Diagram of A.C. Drive

Diode BridgeRectifier

3-phSupply

PWMInverter

Control CircuitSpeed

Reference

Output Voltageand FrequencyControl Signals

IM

Variable speed induction motor drives are now used todrive compressors and fans in industries and in domesticappliances like refrigerators, airconditioners, and washingmachines to improve energy efficiency.


Other Advantages of A.C. Drive

Limits inrush current at the time of starting preventing utilitysupply voltage dips and thereby prevents maloperation ofother equipment connected to the same power supply.Soft start reduces stress on the insulation of the motorwinding and the power cable and prolong their life.In an induction motor we have Φm ∝ |V1|/f1 where Φm isthe airgap flux, |V1| is the supply voltage per phase, and f1is the supply frequency.Using an A.C. drive we can adjust the motor voltage andfrequency to ensure that iron loss is equal to the copperloss at all loads so that the motor runs at the highestefficiency at any load.


Static Kramer Drive for Slip Ring Induction Motor

BridgeRectifier

BridgeInverter

Wound RotorInduction

Motor

Three-phasePower Supply

SlipPower

TransformerStarting

Rheostats

InputPower Feedback

Power

This method of speed control is also known as slip-powerrecovery scheme.


D.C. Motor Drive

ControlledRectifier

3-phSupply

ControlCircuit

SpeedReference

Output VoltageControl Signals

MField Coil

DiodeRectifier

+

-

+ -

3-phSupply

D.C. motors are now being replaced by squirrel-cageinduction motors driven by A.C. drives because they aremore rugged and need lesser maintenance.


Domestic Fan Speed Regulators

Power electronic fan regulators, shown above right arevery compact and more energy efficient than inefficientresistive old fan speed regulators shown above left.


Brushless D.C. Motor Drive

Brushless D.C. motors (BLDC) are special type of D.C.motors which are now being increasingly used inapplications where speed variation is needed as in thecase of electric vehicles.


Brushless D.C. Motor Drive

BridgeInverter

Microcontrolleror DSP BasedControl CircuitSpeed

Reference

BLDCMotor

+-

ControlSignals

D.C.Source

Feedbackfrom sensors

A BLDC motor cannot run without power electronic drive circuit.


Compact Flourescent Lamp Controllers

EMIFilter

Rectifierwith CFilter

1-Ph Power50 or 60 Hz

HalfBridgeInverter

ControlCircuit

L-C TankCircuit

CFLTube

BrightnessControlSignals

UserBrightnessSet Point

CurrentSensor

BrightnessFeedback

Compared to incandescent lamps, though CFLs arecostlier, they give the same amount of visible light, use 20-30% lesser electric power, and last 8-15 times longer.A CFL can save about five times its purchase price inelectricity costs during the lamp’s lifetime.


LED Lamp Driver

EMIFilter

1-Ph Power50 or 60 Hz

BridgeRectifier

CurrentRegulator

Power FactorCorrection

Circuit

The power factor correction circuit – which is a powerelectronic circuit – maintains high power factor on thesupply side.The current regulator – which is another power electroniccircuit – maintains constant current through the seriesconnection of several LEDs.Some of the modern LED driving circuits also providedimming facility.


Power Electronics in D.C. Power Supplies

Power electronics helps in realizing switched mode powersupplies (SMPS), shown on the right side above, which arecompact and more energy efficient than conventionalregulated power supplies shown on the left side.


Problems in Present Day Power Systems

Growing consumer’s demand for power.Increasing system complexity due to inter-connectionsbetween different grids.Constraints on installation of new generators andtransmission lines due to economic and environmentalissues.Loss of system stability due to unregulated active andreactive power flow in transmission lines.Higher transmission power losses.Loop power flow in large integrated power systems.Voltage instability.Inability to utilize power transmission capability of thetransmission line up to its thermal limit.


Inflexible Power Flow in Transmission Lines

S RT

The power flow in a transmission line is entirely governedby the voltage across the line and the line impedance.If the impedances of lines are not similar then, atransmission line operating in parallel with others may notbe loaded up to its thermal capacity.


FACTS Controller Controls Power Flow in Lines

S RT

FACTSController

Using FACTS controllers – which are power electroniccontrollers – we can utilize the full capacity of thetransmission lines.Using FACTS controllers we can also route power flow inthe desired path of transmission lines in a complex powersystem network.


Steady-state Stability Limit of a Line

S R

Theoretical steady-state stability limit of a line isPm = |VS| · |VR|/X corresponding to δ = 90◦.But in practice, δ is kept in the range 30◦-40◦ as otherwisethe synchronous machines will become unstable and losesynchronism, especially when there is a fault on thetransmission line.


STATCOM Increases Steady-state Stability Limit

STATCOM

WithCompensation

WithoutCompensation

With STATCOM – which is a power electronic controllerthat supplies only reactive power – at the middle of the line,more power can be transmitted over existing line for agiven δ without instability problems.


Reactive Power Compensation using Capacitor

InductiveLoad

Inductive load, which is very common, causes drop in VR.To improve VR, traditionally, a capacitor – which suppliesreactive power – is connected in parallel with the load.But if the inductive load increases further, then, VR dropsagain causing a decrease in the reactive power Q.Then, we need to change C in order to increase Q toimprove VR. But C can be varied only in steps and notsmoothly.


SVC Delivers Q Independent of VR

InductiveLoad

SVC

Static VAR Compensator (SVC) is a power electroniccompensator.When VR drops, SVC can be made to deliver reactivepower to improve VR.Under very light load conditions, when VR tends to riseabove rated value, SVC can be made to absorb reactivepower to bring down VR to the rated value.With SVC, smooth variation of Q is possible.


Problems of Long Transmission Lines

Typically very long transmission lines carry power fromremote generating stations to the urban areas where userloads are concentrated.But very long lines have high inductive reactance due towhich the maximum power transmission capacity of theline decreases which may lead to instability.High impedance of long lines also causes low voltage atthe receiving end due to higher voltage drop in the line.


HVDC Transmission

Converter 1

A B

50 Hz 60 Hz

Load

Load

Load

Load

Converter 2

Requires only two conductors.No voltage drop due to inductance of line due to D.C.flowing through the lines.Bidirectional power flow is possible. For example, to makepower flow from A to B, we should make Converter 1 workas rectifier and Converter 2 as an inverter.No instability problem as in the case of a long A.C.transmission line.


Typical Stand-alone PV System

PVModule

ChargeController

Inverter LoadsBatteries

Charge controller is a power electronic interface whichfeeds energy captured from PV module into the batteries.Inverter is a power electronic interface which converts D.C.power stored in battery to A.C. power required by the load.


Typical Grid Connected PV System

PVModule

D.C-to-D.C.Converter

Inverter

A.C. Grid

D.C.-to-D.C. converter is used to boost the PV arrayvoltage and extract maximum solar power from the PVmodule.The inverter takes D.C. power from D.C.-to-D.C. converterand converts it to A.C. power that is fed to the utility grid.


Power Electronics in Wind Energy Systems

Rectifier

GearBox

Inverter

Rectifier

Transformer

SynchronousGenerator

Grid

WindTurbine

Frequency and magnitude of voltage generated bysynchronous generator varies due to changes in windspeed.The grid supply is rectified to supply D.C. to the field coilson the rotor of the alternator.The inverter produces A.C. from D.C. link voltage andfeeds to the grid through a step-up transformer.


Power Electronics in Fuel Cell Energy Systems

D.C-to-D.C.Converter

A.C. Grid

Stack ofFuel Cells

Inverter Filter

In a fuel cell energy is produced when hydrogen reactswith oxygen to form water.Typically a stack of hydrogen fuel cells produces D.C.power at low voltage.D.C.-to-D.C. converter boosts up the D.C. voltage to thelevel required by the inverter.The inverter converts D.C. power to A.C. and feeds it to thegrid at the voltage and frequency required by the grid.Filter is an L-C circuit which removes unwanted harmonicsfrom the inverter output.


Power Electronics Tries to Achieve These

In power electronics we always strive to achieve these —High energy efficiency.Compactness and light weight of hardware.High reliability.Economy.


Power Electronics is Enabling Technology

“In the highly automated industrial environment strugglingfor high quality products with low cost, it appears that twotechnologies will be most dominating: computers andpower electronics ...” – Bimal K. Bose, “Energy,Environment and Advances in Power Electronics”, IEEETransactions on Power Electronics, Vol. 15, No. 4, July2000, p. 680.“Modern computers, communication and electronicsystems get life blood from power electronics. Modernindustrial processes, transportation and energy systemsbenefit tremendously in productivity and qualityenhancement with the help of power electronics.”, ibid,p. 693.


PSIM – Simulation Software for Power Electronics

Design of complex power electronic systems is now being doneusing softwares like PSIM.


PLECS – Another Simulation Software

Another prominant software for simulation of power electronicsystems is PLECS.


Processor-In-Loop (PIL) for Rapid Prototyping

MCU

ADCModel

PWMModel

PowerConverter

Software Environment

The power circuit of the converter, PWM signal generator,and ADC are implemented virtually on a software likePSIM or PLECS.The sampled signal from ADC model is transferred to thecontroller which is running on an external MCU or DSPwhich then controls the PWM model output.Automatic code generation is employed for rapidprogramming of the controller MCU/DSP.


Hardware-In-Loop (HIL) for Prototyping

HIL systems are computers with associated software foremulation of both power circuit and controller.


RT-Box HIL System from PLEXIM

This HIL system can emulate the power stage of a powerelectronic converter.The controller can be connected to this box for testing.


Wide Band Gap Devices Maturing

Silicon carbide (SiC) and Gallium nitride (GaN) devices arereaching different levels of maturity.For a given rating, GaN devices will be smaller and faster.GaN devices have lesser on-state resistance and yeildhigher efficiency.GaN devices are increasingly being used in wireless powertransfer systems, autonomous vehicles, high-speedcommunication systems, low-cost satellites, and miniaturemedical care systems.


EPC – Company Leading in GaN Technologies


Top Companies related to Power Electronics

https://www.infineon.com/

https://www.semikron.com/

http://www.rohm.com/web/global/

http://www.vishay.com/

https://www.fairchildsemi.com/

http://www.st.com/content/st_com/en.html

http://www.ti.com/

http://www.linear.com/

http://www.onsemi.com/

http://epc-co.com/epc

http://www.toshiba.com/tai/

https://www.maximintegrated.com/en.html

http://www.ixys.com/


https://www.infineon.com/

https://www.semikron.com/

http://www.rohm.com/web/global/

http://www.vishay.com/

https://www.fairchildsemi.com/

http://www.st.com/content/st_com/en.html

http://www.ti.com/

http://www.linear.com/

http://www.onsemi.com/

http://epc-co.com/epc

http://www.toshiba.com/tai/

https://www.maximintegrated.com/en.html

http://www.ixys.com/

Introduction to Resonant Converters

Present day fast converters operate at much higherswitching frequencies to reduce weight and size of the filtercomponents.As switching frequency increases, switching losses tend toincrease, causing the junction temperatures to rise withinthe device.Higher frequency of switching also tends to increase EMI.Resonant converters make use of resonant L-C networksin association with switching devices to implement softswitching to reduce switching power loss and EMI.


What are Power Modules?

A power module or power electronic module containsseveral power semiconductor devices connected indifferent configurations required to build the power circuitsof converters.Modern converters are built using power modules.


Losses in Power Modules

Losses in controlled devices like SCRs, MOSFETS, IGBTsConduction lossesSwitching losses during turn-on and turn-off

Losses in power diodesConduction lossesSwitching losses during turn-on and turn-off

Power loss during off-state is very small and therefore it isneglected.


Meaning of ZVS and ZCS

Turning on or off a semiconductor device when the voltageacross it is zero is known as Zero Voltage Switching.Turning on or off a semiconductor device when the currentthrough it is zero is known as Zero Current Switching.ZVS and ZCS are together known as soft switchingtechniques.There are various circuit configurations to achieve ZVSand ZCS.Soft switching techniques reduce switching power loss andEMI.


Concluding

Power electronics is a highly evolving multi-disciplinary field. Tokeep in pace with the latest developments in this field be in

touch with various agencies, companies and literaturementioned earlier.

Thank you for patient listening.


Trends in-power-electronics

Engineering

Transcript of Trends in-power-electronics