Trends in-power-electronics

Trends in Power Electronics
Lecture delivered at ATME College of Engineering, Mysuru
R S Ananda Murthy
Associate Professor
Dept. 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 to
State the goal of power electronics.
Describe some important applications of power electronics.
List major professional bodies and conferences related to
the field of power electronics.
List important journals related to the field of power
electronics.
List important companies related to the field of power
electronics.
Mention some of the recent trends in the field of power
electronics.

Fuel Shares of Primary Energy Supply
Oil 32.8 %
Coal
27.2 %
*Other 0.8 %
10.2 %
Biofuels
2.3 %
Hydro
5.8 %
Nuclear
Natural Gas
20.8 %
Hydro 1.4 %
Nuclear 0.7 %
Natural Gas
7.2 %
Oil 23.6 %
Biofuels 24.5 %
*Other 0.3 %
Coal
42.3 %
Source: International Energy Agency (IEA)

Graph of Depletion Function of Fuels
1900 1950 2000 2050 2100 2150 2200 2250 2300
Coal
Oil
Natural Gas
Uranium
0
EnergyProductioninJoules
1.2
1.0
0.8
0.6
0.4
0.2
x 10
18
Years
Depletion Function:
, , are constants
for a particular type of fuel.

Hazards Caused by Burning of Fossil Fuels
Ozone layer
depletion
Global warming
Combustion
of fossil fuels
Acid rain Photochemical
oxidants (Visibility)
Fine Inorganic
Particles
Health effects
Volatile Organic
Compounds
We need to reduce consumption of fossil fuels because it
causes environmental pollution and health hazards.
Therefore we have to harness energy needed for
development from other sustainable sources like solar and
wind.

Higher Energy Efﬁciency Saves Fuels
G
TurbineSteam
Power
Loss
%
Power
Left
%
65 35
100 %
2.5 34.1
1.2 33.7
Step-up
Voltage to
Transmission
Level
Step-down
Voltage to
Sub-transmission
Level
1.6 33.2
2.5 32.4
Step-down
Voltage to
Distribution
Level
IM
2.0 31.7
Switchgear
Induction Motor
Pump
12.0 27.9
40.0 16.7
Generator
Efficiency
Overall efficiency:
This shows that every kW
of output power saved
results in a saving of 6 kW
of fuel power at the
generating site.

What is Power Electronics?
Power electronics is the technology associated with
efficient conversion and control of electric power by using
power semiconductor devices.
Power electronics encompasses the use of electronic
components, the application of circuit theory and design
techniques, and the development of analytical tools toward
efficient electronic conversion, control, and conditioning of
electric power. — Definition given by IEEE Power
Electronics Society.

Goal of Power Electronics
Efﬁcient conversion, conditioning, or processing and
control of electric power using solid-state semiconductor
devices in order to supply high quality power to the load
causing minimum pollution of environment and the utility
supply circuit.

Block Diagram of a Power Processor
Converter
Control Circuit
or
Triggering Circuit
Control
Signals
Reference
Feedforward
Feedback
Raw
Electrical
Power
Output
Electrical
Power
in the Form
Required by
Load
Converter has power switching semiconductor devices and
energy storing elements like inductors and capacitors.
Resistive elements are avoided in converters because they
cause power loss and reduce efﬁciency.
Controller switches on/off the switching devices present in
the 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 of
power conversion.

Types of Converters
Symbol
Rectifier
Input Output
A.C. at
constant voltage
and frequency
D.C. at
variable voltage
Inverter
D.C. at
constant voltage
A.C. at
desired voltage
and frequency
Chopper
D.C. at
constant voltage
D.C. at
desired voltage
Cycloconverter
A.C. at
constant voltage
and frequency
A.C. at
desired voltage
and frequency
A.C. Voltage
Controller
A.C. at
constant voltage
and frequency
A.C. at
desired voltage
and input frequency
Converter Type
ACVC

Power Electronics Vs Signal Processing
In Power Electronics —
The focus is on power conversion at the highest possible
efﬁciency using very small control signals.
Semiconductor devices work as switches.
Power handled may range from a few watts to several
mega-watts.
In Signal Processing —
Semiconductor devices generally work as controlled
sources in the linear region of their characteristics.
The focus is on information processing with minimum loss
of information.
Power handled will be of the order of few milli-watts or few
watts.

Multidisciplinary Nature of Power Electronics
Power
Electronics
Electrical
Machines
Power
Systems
Circuit
Theory
Solid State
Physics Signal
Processing
Systems and
Control Theory
Analog
Electronics
Digital
Electronics
Simulation and
Computing
Electromagnetics
Microcontrollers

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

Power Sources Manufacturers Association
PSMA publishes The Power Technology Roadmap Report
which is an indicator of state-of-art in power electronics
industry.

Applied Power Electronics Conference (APEC)
Very major Power Electronics Conference which has
participants coming from all over the world.

Publications related to Power Electronics
IEEE Transactions on Power Electronics
IEEE Power Electronics Letters
IEEE Power Electronics Magazine
IEEE Journal of Emerging and Selected Topics in Power
Electronics
IEEE Transactions on Transportation Electrification
IEEE Electrification Magazine
Refer to the above mentioned publications to keep in touch with
the latest developments in the field of Power Electronics.

Major Areas of Application of Power Electronics
Motor Drives and Actuators
Illumination Engineering
Energy Efﬁcient Power Supplies
Sustainable Energy Systems
Vehicle and Transportation Systems
Power and Control Core Technologies

Affinity Laws of Hydraulics
Affinity Laws are applicable to pumps and fans. According
to 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 N
is the speed of the pump or fan.
Keeping the speed constant, the flow can be controlled by
using a valve or a damper. Then, as per equation given
above, 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 the
speed by 50%, then,
Q1
Q2
=
N1
N2
=
1
2
; and
P1
P2
=
1
2
3
=
1
8
which shows that the power is reduced by a factor of 8 if
the speed is decreased by a factor of 2.
This is more energy efﬁcient than using a valve or a
damper.
But this requires a variable speed drive.

Why A.C. Drive?
Most of the industrial pumps and fans are driven by
three-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 of
poles in the stator rotating magnetic ﬁeld, and s is the slip.
This shows that the speed can be controlled smoothly by
changing the frequency of the supply given to the stator.

Block Diagram of A.C. Drive
Diode Bridge
Rectifier
3-ph
Supply
PWM
Inverter
Control Circuit
Speed
Reference
Output Voltage
and Frequency
Control Signals
IM
Variable speed induction motor drives are now used to
drive compressors and fans in industries and in domestic
appliances like refrigerators, airconditioners, and washing
machines to improve energy efﬁciency.

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

Static Kramer Drive for Slip Ring Induction Motor
Bridge
Rectifier
Bridge
Inverter
Wound Rotor
Induction
Motor
Three-phase
Power Supply
Slip
Power
Transformer
Starting
Rheostats
Input
Power Feedback
Power
This method of speed control is also known as slip-power
recovery scheme.

D.C. Motor Drive
Controlled
Rectifier
3-ph
Supply
Control
Circuit
Speed
Reference
Output Voltage
Control Signals
M
Field Coil
Diode
Rectifier
+
-
+ -
3-ph
Supply
D.C. motors are now being replaced by squirrel-cage
induction motors driven by A.C. drives because they are
more rugged and need lesser maintenance.

Domestic Fan Speed Regulators
Power electronic fan regulators, shown above right are
very compact and more energy efﬁcient than inefﬁcient
resistive 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 in
applications where speed variation is needed as in the
case of electric vehicles.

Brushless D.C. Motor Drive
Bridge
Inverter
Microcontroller
or DSP Based
Control CircuitSpeed
Reference
BLDC
Motor
+
-
Control
Signals
D.C.
Source
Feedback
from sensors
A BLDC motor cannot run without power electronic drive circuit.

Compact Flourescent Lamp Controllers
EMI
Filter
Rectifier
with C
Filter
1-Ph Power
50 or 60 Hz
Half
Bridge
Inverter
Control
Circuit
L-C Tank
Circuit
CFL
Tube
Brightness
Control
Signals
User
Brightness
Set Point
Current
Sensor
Brightness
Feedback
Compared to incandescent lamps, though CFLs are
costlier, 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 in
electricity costs during the lamp’s lifetime.

LED Lamp Driver
EMI
Filter
1-Ph Power
50 or 60 Hz
Bridge
Rectifier
Current
Regulator
Power Factor
Correction
Circuit
The power factor correction circuit – which is a power
electronic circuit – maintains high power factor on the
supply side.
The current regulator – which is another power electronic
circuit – maintains constant current through the series
connection of several LEDs.
Some of the modern LED driving circuits also provide
dimming facility.

Power Electronics in D.C. Power Supplies
Power electronics helps in realizing switched mode power
supplies (SMPS), shown on the right side above, which are
compact and more energy efﬁcient than conventional
regulated 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-connections
between different grids.
Constraints on installation of new generators and
transmission lines due to economic and environmental
issues.
Loss of system stability due to unregulated active and
reactive 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 the
transmission line up to its thermal limit.

Inﬂexible Power Flow in Transmission Lines
S RT
The power ﬂow in a transmission line is entirely governed
by the voltage across the line and the line impedance.
If the impedances of lines are not similar then, a
transmission line operating in parallel with others may not
be loaded up to its thermal capacity.

FACTS Controller Controls Power Flow in Lines
S RT
FACTS
Controller
Using FACTS controllers – which are power electronic
controllers – we can utilize the full capacity of the
transmission lines.
Using FACTS controllers we can also route power ﬂow in
the desired path of transmission lines in a complex power
system network.

Steady-state Stability Limit of a Line
S R
Theoretical steady-state stability limit of a line is
Pm = |VS|·|VR|/X corresponding to δ = 90◦.
But in practice, δ is kept in the range 30◦-40◦ as otherwise
the synchronous machines will become unstable and lose
synchronism, especially when there is a fault on the
transmission line.

STATCOM Increases Steady-state Stability Limit
STATCOM
With
Compensation
Without
Compensation
With STATCOM – which is a power electronic controller
that supplies only reactive power – at the middle of the line,
more power can be transmitted over existing line for a
given δ without instability problems.

Reactive Power Compensation using Capacitor
Inductive
Load
Inductive load, which is very common, causes drop in VR.
To improve VR, traditionally, a capacitor – which supplies
reactive power – is connected in parallel with the load.
But if the inductive load increases further, then, VR drops
again causing a decrease in the reactive power Q.
Then, we need to change C in order to increase Q to
improve VR. But C can be varied only in steps and not
smoothly.

SVC Delivers Q Independent of VR
Inductive
Load
SVC
Static VAR Compensator (SVC) is a power electronic
compensator.
When VR drops, SVC can be made to deliver reactive
power to improve VR.
Under very light load conditions, when VR tends to rise
above rated value, SVC can be made to absorb reactive
power 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 from
remote generating stations to the urban areas where user
loads are concentrated.
But very long lines have high inductive reactance due to
which the maximum power transmission capacity of the
line decreases which may lead to instability.
High impedance of long lines also causes low voltage at
the 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 make
power flow from A to B, we should make Converter 1 work
as 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
PV
Module
Charge
Controller
Inverter LoadsBatteries
Charge controller is a power electronic interface which
feeds 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
PV
Module
D.C-to-D.C.
Converter
Inverter
A.C. Grid
D.C.-to-D.C. converter is used to boost the PV array
voltage and extract maximum solar power from the PV
module.
The inverter takes D.C. power from D.C.-to-D.C. converter
and converts it to A.C. power that is fed to the utility grid.

Power Electronics in Wind Energy Systems
Rectifier
Gear
Box
Inverter
Rectifier
Transformer
Synchronous
Generator
Grid
Wind
Turbine
Frequency and magnitude of voltage generated by
synchronous generator varies due to changes in wind
speed.
The grid supply is rectiﬁed to supply D.C. to the ﬁeld coils
on the rotor of the alternator.
The inverter produces A.C. from D.C. link voltage and
feeds 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 of
Fuel Cells
Inverter Filter
In a fuel cell energy is produced when hydrogen reacts
with 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 the
level required by the inverter.
The inverter converts D.C. power to A.C. and feeds it to the
grid at the voltage and frequency required by the grid.
Filter is an L-C circuit which removes unwanted harmonics
from 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 struggling
for high quality products with low cost, it appears that two
technologies will be most dominating: computers and
power electronics ...” – Bimal K. Bose, “Energy,
Environment and Advances in Power Electronics”, IEEE
Transactions on Power Electronics, Vol. 15, No. 4, July
2000, p. 680.
“Modern computers, communication and electronic
systems get life blood from power electronics. Modern
industrial processes, transportation and energy systems
beneﬁt tremendously in productivity and quality
enhancement with the help of power electronics.”, ibid,
p. 693.

PSIM – Simulation Software for Power Electronics
Design of complex power electronic systems is now being done
using softwares like PSIM.

PLECS – Another Simulation Software
Another prominant software for simulation of power electronic
systems is PLECS.

Processor-In-Loop (PIL) for Rapid Prototyping
MCU
ADC
Model
PWM
Model
Power
Converter
Software Environment
The power circuit of the converter, PWM signal generator,
and ADC are implemented virtually on a software like
PSIM or PLECS.
The sampled signal from ADC model is transferred to the
controller which is running on an external MCU or DSP
which then controls the PWM model output.
Automatic code generation is employed for rapid
programming of the controller MCU/DSP.

Hardware-In-Loop (HIL) for Prototyping
HIL systems are computers with associated software for
emulation of both power circuit and controller.

RT-Box HIL System from PLEXIM
This HIL system can emulate the power stage of a power
electronic converter.
The controller can be connected to this box for testing.

Wide Band Gap Devices Maturing
Silicon carbide (SiC) and Gallium nitride (GaN) devices are
reaching different levels of maturity.
For a given rating, GaN devices will be smaller and faster.
GaN devices have lesser on-state resistance and yeild
higher efﬁciency.
GaN devices are increasingly being used in wireless power
transfer systems, autonomous vehicles, high-speed
communication systems, low-cost satellites, and miniature
medical 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/

Introduction to Resonant Converters
Present day fast converters operate at much higher
switching frequencies to reduce weight and size of the ﬁlter
components.
As switching frequency increases, switching losses tend to
increase, causing the junction temperatures to rise within
the device.
Higher frequency of switching also tends to increase EMI.
Resonant converters make use of resonant L-C networks
in association with switching devices to implement soft
switching to reduce switching power loss and EMI.

What are Power Modules?
A power module or power electronic module contains
several power semiconductor devices connected in
different conﬁgurations required to build the power circuits
of converters.
Modern converters are built using power modules.

Losses in Power Modules
Losses in controlled devices like SCRs, MOSFETS, IGBTs
Conduction losses
Switching losses during turn-on and turn-off
Losses in power diodes
Conduction losses
Switching losses during turn-on and turn-off
Power loss during off-state is very small and therefore it is
neglected.

Meaning of ZVS and ZCS
Turning on or off a semiconductor device when the voltage
across it is zero is known as Zero Voltage Switching.
Turning on or off a semiconductor device when the current
through it is zero is known as Zero Current Switching.
ZVS and ZCS are together known as soft switching
techniques.
There are various circuit conﬁgurations to achieve ZVS
and ZCS.
Soft switching techniques reduce switching power loss and
EMI.

Concluding
Power electronics is a highly evolving multi-disciplinary ﬁeld. To
keep in pace with the latest developments in this ﬁeld be in
touch with various agencies, companies and literature
mentioned earlier.
Thank you for patient listening.

Trends in-power-electronics

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