Advanced Power Electronics

1. Chapter 0 – Introduction
1
Advanced Power Electronics (EE4007A/B/D )
Dr. Jerry Hu
03-09-2019

2. Introduce myself (Lecturer)
2
Chapter 0 – Introduction
Introduce the subject (Advanced Power Electronics)

3. About myself
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Chapter 0 – Introduction
• I obtained the PhD degree in Electrical Engineering in Australia.
• I have dedicated to teaching and research in the field of power electronics for
more than 7 years.
• Currently I am an assistant professor in PolyU.

4. Ground rules
5
Chapter 0 – Introduction
• Submit report/assignment on time. Late submission will lead to marks
deduction
 Fairness
 Respect
 Integrity
• Power off or turn on mute mode of mobile phones
• Do not shout out loud or make any noise to distract other students
• Raise your hand or ask questions straight away when something is not
clear or when you want me to explain again
• Do not copy others’ results in lab reports and assignment
• Do not cheat in exams and tests

5. General Information about This Course
6
Chapter 0 – Introduction

6. What is Power Electronics (PE) ?
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Chapter 0 – Introduction
 Power + Electronics
• Power electronics is the application of solid-state electronics (circuits
or devices built from materials like metal wires, metal plates, silicon,
etc.) to the control and conversion of electric power
• High switching frequency, usually several kHz or above
• Rapidly developed since 1980s
• Applications
 Industrial, commercial and residential purposes
 Consumer electronics, Electrical vehicles, aerospace and space
technologies
• Use something visible (Electronics) to control something invisible
(Power)
電力電子

7. 8
Chapter 0 – Introduction
https://www.youtube.com/watch?v=A9H3vef9IcY
https://www.youtube.com/watch?v=dVvS9OJEhig
The role of power electronics
Power Electronic Applications
What is Power Electronics (PE) ?

8. The essential of this subject is Power
Electronic Converters
9
Chapter 0 – Introduction
A quick question: how to convert the voltage from one level to another?

9. What is Smart City and what is the role of PE in
Smart City?
10
Chapter 0 – Introduction
Source: SMARTCITIES.IEEE.ORG
Functional Domains:
• Sensors and Intelligent Electronic Devices
• Communication Networks & Cyber Security
• Systems Integration
• Intelligence & Data Analytics
• Management & Control Platforms

10. Applications of Power Electronics
11
Chapter 0 – Introduction
 Switched Mode Power Supplies (SMPS)
 Steady and regulated output voltage / current
 Applications of SMPS
• Low voltage high current DC power supplies
• Battery chargers
• Welding machines with over 100A
• Aerospace power systems
• Several KV power supplies for radar systems
DC input
DC output

11. Applications of Power Electronics
12
Chapter 0 – Introduction
 Control of Switched Mode Power Supplies (SMPS)
 Closed loop control for regulating output
 Pulse-width-modulation (PWM),
frequency modulation or phase
modulation control
 Microprocessors (DSP, FPGA)
 Range of operation concerned

12. Applications of Power Electronics
13
Chapter 0 – Introduction
 AC current or AC voltage output
 DC/AC converters (Inverters)
 DC input
 Applications of Inverters
 AC power supplies
 AC drives (Trains)
 Induction heating (Heater)
 Electronic ballasts (Fluorescent lamps)
Electronic ballast
Fluorescent lamp
Traditional lamp
Filament

13. Applications of Power Electronics
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Chapter 0 – Introduction
 Waveform Shaping & EMI Control Systems
 Shaping input / output and voltage / current
 Power factor correction rectifiers
 Active filters

14. Applications of Power Electronics
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Chapter 0 – Introduction
 Uninterruptible Power Supplies (UPS)
 With DC/DC converter of charging and
discharging battery
 With Inverter for AC output commonly used in hospitals as
backup power sources

15. Applications of Power Electronics
16
Chapter 0 – Introduction
 Motor Drives
 Choppers for brush-type DC motors
 Variable speed drives (VSD) for induction motors
 Converters for brushless DC motors
 Converters for switched reluctance motors

16. Power Components in Power Electronics
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Chapter 0 – Introduction
 Energy Storage Components
• Inductors, capacitors, transformers
 Passive Switching Devices
• Diodes
 Active Switching Devices
• IGBT
• Thyristors (SCR),
• Gate turn-off thyristors (GTO)
• Bipolar Junction Transistors (BJT)
• MOSFET

17. Power Components
18
Chapter 0 – Introduction
 Capacitors
• Capacitance occurs when two conductors (plates) are separated by a
dielectric (insulator).
• Charge on the two conductors creates an electric field that stores
energy.
• The voltage difference between the two conductors is proportional
to the charge: q = C v
• The proportionality constant C is called capacitance.
• Units of Farads (F) - C/V 1F=106F, 1F=106PF
 v-i relationship
( )
( )
dv t
i t C
dt

Energy stored
2
1
( ) ( )
2
L
E t Cv t


18. Power Components
19
Chapter 0 – Introduction
 Inductors
 store energy in a magnetic field that is created by electric passing through it.
 v-i relationship
dt
t
di
L
t
v
)
(
)
( 
Energy stored:
2
1
( ) ( )
2
L
E t Li t


19. Why high frequency
20
Chapter 0 – Introduction
Small size and light weight
Inductors
Capacitors

20. Power Components
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Chapter 0 – Introduction
 Transformers
Primary Secondary

21. Power Components
22
Chapter 0 – Introduction
 Passive Switching Devices – Diodes
A p-n junction forms what is called a diode. Its circuit symbol is:
What is p-n junction?
The predominant semiconductor material is silicon
1 silicon atom = 1 nucleus + 4 electrons

22. Power Components
23
Chapter 0 – Introduction
 Passive Switching Devices – Diodes
If Si is doped with an element with only 3 valence electrons, a
hole is created at the position vacated by that valence electron.
A semiconductor doped with such Si configuration is rich in holes.
It shows positive charge and can accept additional electrons.
Therefore it is called p-type semiconductor.
If Si is doped with an element with 5 valence electrons, then four
of the valence electrons will take part in the covalent bonding with
the neighbouring Si atoms while the fifth one will be free to move
around.
A semiconductor doped with such Si configuration is rich in
electrons. It shows negative charge and can donate additional
electrons. Therefore it called n-type semiconductor.
p-type
n-type

23. Power Components
24
Chapter 0 – Introduction
The p-n Junction
What happens when P-type and N-type form a p-n Junction?
Imagine that we have a gas cylinder full of oxygen. We open the valve to
release the oxygen into the room. What happens? The oxygen and the air
in the room mix – a process known as diffusion. Nature wants things to
spread out in an even fashion. This is what happens with the free, gas-like
particles in the p-n junction.
Current direction of a diode

24. Power Components
25
Chapter 0 – Introduction
 Passive Switching Devices – Diodes

25. Power Components
26
Chapter 0 – Introduction
 An example of using diode – Half-wave rectifier
+
+
-
vi
vo
vo
-
+
R
D
When vi > Von , D on vo  vi；
vi < Von， D off  vo = 0。

26. Power Components
27
Chapter 0 – Introduction
 Active Switching Devices
• IGBT
• Thyristors (SCR),
• Gate turn-off thyristors (GTO)
• Bipolar Junction Transistors (BJT)
• MOSFET
Turn on and turn off the circuit actively

27. Characteristics of Active Switching Devices
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Chapter 0 – Introduction
 Symbol of Active Switching Devices

28. Characteristics of Active Switching Devices
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Chapter 0 – Introduction
 Thyristor / Silicon Controlled Rectifier(SCR)
• Developed in 1960s
• Switched on by a short injecting gate current pulse
(Firing or Triggering)
• Switched off when reverse biased
• Ratings up to 5kV and 4000A
• Very high power applications
• Around 2V on-state voltage
• Slow response
• fS< 1kHz

29. Characteristics of Active Switching Devices
30
Chapter 0 – Introduction
 Bipolar Junction Transistor (BJT)
• Controlled by base current
• On and off only
• Ratings up to 1kV and 4000A
• Very high power applications
• On-state voltage >1V
• Faster than thyristors
• fS< 5kHz
• Slower than MOSFET and IGBT
• Rarely used

30. Characteristics of Active Switching Devices
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Chapter 0 – Introduction
 Metal Oxide Silicon Field Effect Transistor (MOSFET)
• Developed in early 1980s
• Controlled by gate-to-source voltage (Vgs)
• Gate Signal, 10V to 18V, typically 15V
• Ratings up to 1000V and 2000A
• Bidirectional and resistive conduction characteristics
• High current low voltage applications
• Very fast response, fS< 1MHz, higher for
soft-switching

31. Characteristics of Active Switching Devices
32
Chapter 0 – Introduction
 Gate Turn-off Thyristor (GTO)
• Developed in mid 1980s
• Similar to thyristor
 Switched on by a injecting short gate current pulse
 Switched off by reverse biased
 Switched off by a high and short reverse current
pulse
• Ratings up to 4.5kV and 3000A
• High power applications
• On-state voltage 2V to 3V
• Response faster than thyristors
• fS< 2kHz

32. Characteristics of Active Switching Devices
33
Chapter 0 – Introduction
 Insulated Gate Bipolar Transistor (IGBT)
• Developed in late 1980s
• Combination of MOSFET and BJT
• Controlled by gate-to-emitter voltage (Vge)
Same as MOSFET
• Ratings up to 3500V and 2000A (Similar to BJT)
 Popular in Motor drives
• On-state voltage 1.7V to 3V
• Fast response
• Typically fS< 40kHz, faster for some models
 Medium to high power applications up to 200kW

33. Why are switching devices needed in PE?
34
Chapter 0 – Introduction
How to change the voltage level?
Taps
For AC voltage
Sliding resistor
Battery
Lamp
Vin
Vo
For DC voltage

34. Why switching device
35
Chapter 0 – Introduction
In order to change the voltage in a continuous and fast manner with high accuracy,
switched mode is introduced. It means the use of switching devices.
Switch device
Bipolar junction transistors (BJT); Field-effect transistors (FET);
Insulated gate bipolar transistor (IGBT)
Vo waveform
On and Off in high frequency from x kHz to x MHz
The output voltage Vo (average voltage) can be calculated as Duty ratio

35. Why switching device
36
Chapter 0 – Introduction
 Even though different output voltage can be achieved by changing the duty ratio, this
voltage is actually the square-wave voltage which is not suitable for most of the DC
electric appliances. If your mobile phone or the computer is supplied by this kind of
voltage, they probably can not work.
 In this case, in order to obtain a constant DC voltage, we can add a capacitor in
parallel to the output voltage.

36. Applications of Power Electronics
37
Chapter 0 – Introduction
 Control of Switched Mode Power Supplies (SMPS)
 Closed loop control for regulating output
 Pulse-width-modulation (PWM),
frequency modulation or phase
modulation control
 Microprocessors (DSP, FPGA)
 Range of operation concerned
 Converter is composed of
various switching devices
 These switching devices are
operating in high frequency

37. Conduction Characteristic and Conduction
Losses
38
Chapter 0 – Introduction
 Conduction losses due to forward voltage
• Diodes
• IGBTs
• BJTs
• Thyristors

38. Conduction Characteristic and Conduction
Losses
39
Chapter 0 – Introduction
 Conduction losses due to resistive feature
• Inductors
• Capacitors
• MOSFETs
• Resistors

39. 40
Conduction
loss
Input Power Output Power
Switched mode power converter
Off-leakage
loss
Switching
loss
Other
loss
High power losses mean:
• Low efficiency
• High temperature
• Large cooling systems
• Higher costs

40. Cooling Devices
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Chapter 0 – Introduction
Most power losses of devices are converted into heat
Every device has operating temperature with specific range. If the heat
cannot be dissipated, the temperature will rise. High temperature may
shorten the lifetime of the devices, or even damage the devices.
The physical surface area of the device is usually too small to allow
sufficient heat flow to surrounding medium
 Where do the power losses transfer ?
 How does the heat affect the devices ?
 Problem of dissipating the heat effectively ?

41. Cooling Devices
42
Chapter 0 – Introduction
 How to dissipate the heat effectively ?
• Increase the surface area by attaching the device to the heat sink
• Heat sink is usually made with finned aluminium (æljəˈmɪniəm)
• Forced-air by fans with heat sink is commonly used to increase
air flow
• Reduce the power level