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Power Electronics
College of Automation and Electronic Engineering
Qingdao University of Science and Technology
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I. What is power electronics?
1) Definition
Power Electronics:is the electronics applied to conversion and control
of electric power.
Range of power scale :
milliwatts(mW) megawatts(MW) gigawatts(GW)
A more exact explanation:
The primary task of power electronics is to process and control theflow of electric energy by supplying voltages and currents in a form
that is optimally suited for user loads.
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Conversion of electric power
Other names for electric
power converter:
-Power converter
-Converter
-Switching converter
-Power electronic circuit
-Power electronic converter
Electric
Power
Converter
Power
output
Power
input
Control
input
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Power electronic systemGeneric structure of a power electronic system
Control is invariably required.Power converter along with its controller
including the corresponding measurement and interface circuits, is also
called power electronic system.
Power
Converter
Control inputController
Reference
Power
input
Power
output
Feedback
(measurements
of output signals )Feedforward
( measurements
of input signals )
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A typical power electronic system
The task of power electronics has been recently extended to also ensuring
the currents and power consumed by power converters and loads to
meet the requirement of electric energy sources.
Power
Converter
MeasurementsController
Reference
Power input Power output
Electric Motor
light
heating
other electric equipment
power converter
Electric utility
batteryother electric energy source
power converter
Source Loadio VoiiVi
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2) Relation with information electronicsA Classification of electronics by processing object
Other classifications of electronics
Electronics
Information electronics: to process information
Power electronics: to process electric power
Electronics
Vacuum electronics: using vacuum devices,
e.g, vacuum tubes devices
Solid (Solid state) electronics: using solid state devices,
e.g, semiconductor devices
Electronics
Physical electronics: physics,material,fabrication,
and manufacturing of electronic devicesApplied electronics: application of electronic
devices to various areas
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3) The interdisciplinary natureWilliam E. Newells description
Power electronics is the interface between electronics and power.
PowerElectronics
Electronics Power
ControlContinuous,
discrete
Static & rotating
power equipment
Devices,circuits
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Relation with multiple disciplines
Power electronics is currently the most active discipline in electric power
engineering.
Power
electronics
Electric
machines
Circuit Ct
theory
Systems&
Control theorySignal
processing
Simulation &
computing
electronics
Solid state
physics
Electromagnetics
Power
systems
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4) Position and significance in the human society
Electric power is used in almost every part and everywhere of modern
human society.
Electric power is the major form of energy source used in modern humansociety.
The objective of power electronics is right on how to use electric power,
and how to use it effectively and efficiently, and how to improve the
quality and utilization of electric power.
Power electronics and information electronics make two poles of modern
technology and human society: information electronics is the brain,
and power electronics is the muscle.
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II. The history
Mercury arc rectifier
Vacuum- tube rectifier
Thyratron
Invention of
Thyristor
Applicat ion of
fast- switching
fully- controlled
semiconductor
devices
Power diode
Thyristor
GTOGTR
Power MOSFET
Thyristor
(microprocessor)
IGBT
Power MOSFET
Thyristor
(DSP)
Pre-history 1st phase 2nd phase 3rd phase
19571900 late 1980smid 1970s
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III. Applications
Industrial applications
Motor drives
Electrolysis
ElectroplatingInduction heating
Welding
Arc furnaces and ovens
Lighting
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Transportation applications
Trains & locomotives
Subways
Trolley buses
Magnetic levitation
Electric vehicles
Automotive electronics
Ship power systems
Aircraft power systems
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Utilitystems applications
High- voltage dc transmission(HVDC)
Flexible ac transmission(FACTS)
Static var compensation & harmonics
suppression: TCR, TSC, SVG, APF
Custom power & power quality control
Supplemental energy sources :
wind, photovoltaic, fuel cells
Energy storage systems
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Power supplies for electronic equipment
Telecommunications
Computers
Office equipment
Electronic instruments
Portable or mobile
electronics
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Residential and home appliances
Lighting
Heating
Air conditioning
Refrigeration & freezers
Cooking
Cleaning
Entertaining
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Applications in space technology
Spaceship power systems
Satellite power systems
Space vehicle power systems
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Other aplications
Nuclear reactor control
Power systems for particle accelerators
Environmental engineering
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Trends
It is estimated that in developed countries now 60% of the electricenergy goes through some kind of power electronics converters beforeit is finally used.
Power electronics has been making major contributions to:--better performance of power supplies and better control of electric
equipment
--energy saving
--environment protection
reduction of energy consumption leads to less pollutionreduction of pollution produced by power converters
direct applications to environment protection technology
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IV. A simple exampleA simple dc-dc converter example
Input source:100VOutput load:50V, 10A, 500W
How can this converter be realized?
Dc-dc
converter+-
+
-
V50V
R5
I10A
Vg
100V
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Dissipative realizationResistive voltage divider
+-
+
-
V50V
R5
I10A
Vg
100V
Pout=500WPin=1000W
+ -50V
Ploss=500W
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Series pass regulator:
transistor operates in active region
+
-
+
-
V
50V
R
5
I10A
Vg
100V
Pout=500WPin1000W
+ -50V
Ploss500W
l inear amplif ier
And b ase driver
-+
Vref
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Use of a SPDT switch
+-
+
-
V(t)
50VR
I10A
Vg
100V
+
-
Vs(t)
Vs(t)
Vg
switch
position:
Vs=DVg
DTs (1-D)Ts
0
1 12
t
12
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The switch changes the dc voltage level
Vs(t)
Vg
switch
position:
Vs=DVg
DTs (1-D)Ts
0
1 12
t
D=switch duty cycle
0
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Addition of low pass filter
Addition of (ideally lossless) L- C low- pass filter, for removal of
switching harmonics:
Choose filter cutoff frequency f0 much smaller than switching frequencyfs.
This circuit is known as the buck converter.
+-
+
-
V(t)
50V
R
I10A
Vg
100V
+
-
Vs(t)
1
2 L
C
Pin500WPlosssmall Pout=500W
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Addition of control system for regulation of output voltage
+-
+
-
V
iVg
H(s)
Pulse-widthmodulator
sensor
gain
Gc(s)-
+
transistor
gate driver
Power
input
LoadSwitching converter
error
signal
VeVc
VrefReferenceinput
compensator
(t)
tdTsTs
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Major issues in power electronics
How to meet the requirement of the load or gain better control of the load
How to improve the efficiency
-- for reliable operation of power semiconductor devices
-- for energy saving
How to realize power conversion with less volume, less weight, and lesscost.
How to reduce negative influence to other equipment in the electric powersystem and to the electromagnetic environment.
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V. About this course
Three parts of the content
Power electronic devices: Chapter 1
Power electronic circuits: Chapter 2, 3, 4, 5, 8
Control techniques: Chapter 6 and 7
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