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.
R S Ananda Murthy Trends in Power Electronics
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)
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
Multidisciplinary Nature of Power Electronics
PowerElectronics
ElectricalMachines
PowerSystems
CircuitTheory
Solid StatePhysics Signal
Processing
Systems andControl Theory
AnalogElectronics
DigitalElectronics
Simulation andComputing
Electromagnetics
Microcontrollers
R S Ananda Murthy Trends in Power Electronics
IEEE Power Electronics Society
IEEE Power Electronics Society is a very important society ofprofessionals in the field of Power Electronics.
R S Ananda Murthy Trends in Power Electronics
Power Sources Manufacturers Association
PSMA publishes The Power Technology Roadmap Reportwhich is an indicator of state-of-art in power electronics
industry.
R S Ananda Murthy Trends in Power Electronics
Applied Power Electronics Conference (APEC)
Very major Power Electronics Conference which hasparticipants coming from all over the world.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in 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
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
PSIM – Simulation Software for Power Electronics
Design of complex power electronic systems is now being doneusing softwares like PSIM.
R S Ananda Murthy Trends in Power Electronics
PLECS – Another Simulation Software
Another prominant software for simulation of power electronicsystems is PLECS.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
Hardware-In-Loop (HIL) for Prototyping
HIL systems are computers with associated software foremulation of both power circuit and controller.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
EPC – Company Leading in GaN Technologies
R S Ananda Murthy Trends in Power Electronics
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/
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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.
R S Ananda Murthy Trends in Power Electronics
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