First Course on
Power Electronics
Module 1: Introduction
By
Ned Mohan
Professor of ECE
University of Minnesota
Reference Textbook:
First Course on Power Electronics by Ned Mohan,
www.mnpere.com
© Copyright Ned Mohan 2008
1
Module 1: Introduction to Power
Electronics
Chapter 1
1-1
1-2
1-3
1-4
1-5
1-6
1-7
Power Electronics: An Enabling Technology
Introduction to Power Electronics
Applications and the Role of Power Electronics
Energy and the Environment
Need for High Efficiency and High Power Density
Structure of Power Electronics Interface
Voltage-Link Structure
Recent and Potential Advancements
References
Problems
© Copyright Ned Mohan 2008
2
Role of Power Electronics
Power Electronics
Interface
Converter
Source
Load
Controller
Figure 1-1 Power electronics interface between the source and the load.
The power electronics interface facilitates the transfer of power from the source to the
load by converting voltages and currents from one form to another, in which it is possible
for the source and load to reverse roles. The controller shown in Fig. 1-1 allows
management of the power transfer process in which the conversion of voltages and
currents should be achieved with as high energy-efficiency and high power density as
possible.
© Copyright Ned Mohan 2008
3
Powering the Information Technology
24 V (dc)
Vin
Power
Converter
Vo
5 V (dc)
Utility
3.3 V (dc)
Controller
(a)
0.5 V (dc)
Vo ,ref
(b)
Figure 1-2 Regulated low-voltage dc power supplies.
© Copyright Ned Mohan 2008
4
Boost Converter
Battery
Cell (1.5 V)
9 V (dc)
Figure 1-3 Boost dc-dc converter needed in cell operated equipment.
© Copyright Ned Mohan 2008
5
Adjustable Speed Drives
Electric
Drive
fixed
form
Power
Processing
Unit (PPU)
Motor
speed /
position
adjustable
form
Electric Source
(utility)
Load
Sensors
measured
speed/ position
Controller
Power
Signal
input command
(speed / position)
Figure 1-4 Block diagram of adjustable speed drives.
© Copyright Ned Mohan 2008
6
Induction Heating
Power
Electronics
Interface
High
Frequency
AC
Utility
Figure 1-5 Power electronics interface required for induction heating.
© Copyright Ned Mohan 2008
7
Electric Welding
Power
Electronics
Interface
DC
Utility
Figure 1-6 Power electronics interface required for electric welding.
© Copyright Ned Mohan 2008
8
Energy and the Environment: The Percentage
Energy Consumption
Lighting 19%
IT
14%
HVAC 16%
Motors 51%
Figure 1-7 Percentage use of electricity in various sectors in the U.S.
© Copyright Ned Mohan 2008
9
Role of adjustable speed drives in
pump-driven systems
Outlet
Adjustable
Speed Drive
(ASD)
Inlet
utility
Pump
Figure 1-8 Role of adjustable speed drives in pump-driven systems.
© Copyright Ned Mohan 2008
10
Compact Fluorescent Lamps
Power
Electronics
Interface
CFL
Utility
Figure 1-9 Power electronics interface required for CFL.
© Copyright Ned Mohan 2008
11
Transportation
Figure 1-10 Hybrid electric vehicles with much higher gas mileage.
• Hybrid electric vehicles with much higher gas mileage
• light rail, fly-by-wire planes
• all-electric ships
• drive-by-wire automobiles.
© Copyright Ned Mohan 2008
12
Renewable Energy
Photovoltaic Systems
DC Input
Power
Electronics
Interface
Utility
(b)
(a)
Figure 1-11 Photovoltaic Systems.
© Copyright Ned Mohan 2008
13
Wind-Electric Systems
Generator
and
Power Electronics
Utility
Figure 1-12 Wind-electric systems.
© Copyright Ned Mohan 2008
14
Uninterruptible Power Supplies
Uninterruptible
Power Supply
Utility
Critical
Load
Figure 1-13 Uninterruptible power supply (UPS) system.
© Copyright Ned Mohan 2008
15
Applications in Power
Systems
© Copyright Ned Mohan 2008
16
Strategic Space and Defense Applications
More Electric Aircraft
Electric Warship
Source: James Soeder, NASA and Terry Ericsen, ONR.
© Copyright Ned Mohan 2008
17
NEED FOR HIGH EFFICIENCY AND
HIGH POWER DENSITY
η=
Po
Po + Ploss
Po =
η
1 −η
Ploss
500
450
Pin
Power
Electronics
Equipment
Po
Po
Power Rating
400
350
300
250
Ploss = 20 W
200
150
Ploss
(a )
Ploss = 10 W
100
50
0
0.8
0.82
0.84
0.86
0.88
0.9
Efficiency
0.92
η
0.94
0.96
(b)
Figure 1-14 Power output capability as a function of efficiency.
© Copyright Ned Mohan 2008
18
Summarizing the Role of Power Electronics
Power
Electronics
Interface
utility
Output to Load
- Adjustable DC
- Sinusoidal AC
- High-frequency AC
Figure 1-15 Block diagram of power electronic interface.
© Copyright Ned Mohan 2008
19
STRUCTURE OF POWER ELECTRONICS INTERFACE
conv1
conv2
utility
Load
controller
Figure 1-16 Voltage-link structure of power electronics interface.
Voltage-link structure of power electronics interface
• Unipolar voltage handling transistors used
• Decoupling of two converters
• Immunity from momentary power interruptions
© Copyright Ned Mohan 2008
20
• Current-Link Systems
• Matrix Converters
© Copyright Ned Mohan 2008
21
Current-Link Systems
AC1
AC2
Figure 1-17 Current-link structure of power electronics interface.
© Copyright Ned Mohan 2008
22
Matrix Converters
ia
va
vc
daA
vb
dbA
dcA
daB
vA
dbB
dcB
daC
vB
vC
dbC
dcC
Figure 1-18 Matrix converter structure of power electronics interface [13].
© Copyright Ned Mohan 2008
23
Voltage-link System
conv1
conv2
utility
Load
controller
Figure 1-19 Load-side converter in a voltage-source structure.
© Copyright Ned Mohan 2008
24
SWITCH-MODE LOAD-SIDE CONVERTER
•
Group 1
Adjustable dc or a low-frequency sinusoidal ac output in
- dc and ac motor drives
- uninterruptible power supplies
- regulated dc power supplies without electrical isolation
•
Group 2
High-frequency ac in
- compact fluorescent lamps
- induction heating
- regulated dc power supplies where the dc output voltage needs to be
electrically isolated from the input, and the load-side converter
internally produces high-frequency ac, which is passed through a
high-frequency transformer and then rectified into dc.
© Copyright Ned Mohan 2008
25
Switch-Mode Conversion: Switching Power-Pole
as the Building Block
+
qA = 1
Vin
+
vA
-
-
vvA
A
Vin
00
t
qA
(a)
(b)
Figure 1-20 Switching power-pole as the building block in converters.
© Copyright Ned Mohan 2008
26
Pulse-Width Modulation (PWM) of the Switching Power-Pole
qA
idA
+
iA
t
Tup
Ts
vA
-
dA
0
d A Ts
+
Vin
1
vA
-
q A = 1or 0
Vin
vA
0
(a)
(b)
t
Figure 1-21 PWM of the switching power-pole.
d A ( = Tup / Ts )
vA =
© Copyright Ned Mohan 2008
Tup
Ts
Vin = d AVin
0 ≤ dA ≤ 1
27
Switching Power-Pole in a Buck DC-DC Converter:
An Example
qA
iin
0
+
iL
Vin
−
1
vA
+
+
vA
Vo
−
−
t
d ATs
Ts
Vin
vA
0
qA
t
iL
0
t
iin
(a)
0
t
(b)
Figure 1-22 Switching power-pole in a Buck converter.
Vo = v A = d AVin
© Copyright Ned Mohan 2008
0 ≤ Vo ≤ Vin
28
Example 1-2
In the converter of Fig. 1-22a, the input voltage Vin = 20V . The
output voltage Vo = 12V . Calculate the duty-ratio d A and the pulse
width Tup , if the switching frequency f s = 200 kHz .
Solution
v A = Vo = 12V .
Using Eq. 1-4, d A =
Vo 12
1
=
= 0.6 and Ts =
= 5μs .
Vin 20
fs
Therefore, as shown in Fig. 1-23, Tup = d ATs = 0.6 × 5μ s = 3μ s .
1
qA
0
t
3μ s
5μ s
Vin = 20V
Vo = 12V
vA
0
t
Figure 1-23 Waveforms in the converter of Example 1-2.
© Copyright Ned Mohan 2008
29
Simulations using
PSpice
SwitchingWaveform.Sch
© Copyright Ned Mohan 2008
30
Simulation Results
vA
8.0V
vo Vo
6.0V
4.0V
2.0V
0V
450us
V(vA)
460us
V(vo)
470us
480us
490us
500us
Time
© Copyright Ned Mohan 2008
31
Fourier Analysis
FOURIER COMPONENTS OF TRANSIENT RESPONSE V(vA)
DC COMPONENT = 6.080000E+00
HARMONIC FREQUENCY FOURIER NORMALIZED PHASE
NORMALIZED
NO
(HZ) COMPONENT COMPONENT (DEG)
PHASE (DEG)
1
2
3
4
5
6
7
8
9
10
1.000E+05
2.000E+05
3.000E+05
4.000E+05
5.000E+05
6.000E+05
7.000E+05
8.000E+05
9.000E+05
1.000E+06
© Copyright Ned Mohan 2008
3.487E+00
2.543E+00
1.310E+00
1.600E-01
6.012E-01
8.387E-01
6.193E-01
1.600E-01
2.763E-01
4.924E-01
1.000E+00 -4.860E+01
7.293E-01 -7.200E+00
3.757E-01 3.420E+01
4.589E-02 7.560E+01
1.724E-01 -6.300E+01
2.405E-01 -2.160E+01
1.776E-01 1.980E+01
4.589E-02 6.120E+01
7.923E-02 -7.740E+01
1.412E-01 -3.600E+01
0.000E+00
9.000E+01
1.800E+02
2.700E+02
1.800E+02
2.700E+02
3.600E+02
4.500E+02
3.600E+02
4.500E+02
32
FOURIER COMPONENTS OF TRANSIENT RESPONSE V(vo)
DC COMPONENT = 6.083044E+00
HARMONIC FREQUENCY FOURIER NORMALIZED PHASE
NORMALIZED
NO
(HZ) COMPONENT COMPONENT (DEG)
PHASE (DEG)
1
2
3
4
5
6
7
8
9
10
1.000E+05
2.000E+05
3.000E+05
4.000E+05
5.000E+05
6.000E+05
7.000E+05
8.000E+05
9.000E+05
1.000E+06
© Copyright Ned Mohan 2008
1.795E-02
3.400E-03
8.465E-04
1.226E-04
1.602E-04
1.718E-04
1.158E-04
5.644E-05
4.483E-05
5.570E-05
1.000E+00
1.894E-01
4.715E-02
6.826E-03
8.922E-03
9.570E-03
6.448E-03
3.143E-03
2.497E-03
3.102E-03
1.343E+02
1.746E+02
-1.489E+02
-1.492E+02
1.447E+02
1.707E+02
-1.626E+02
-1.560E+02
1.751E+02
1.789E+02
0.000E+00
-9.403E+01
-5.518E+02
-6.865E+02
-5.269E+02
-6.352E+02
-1.103E+03
-1.231E+03
-1.034E+03
-1.164E+03
33
Currents
16A
iL
iR
10A
iC
0A
-4A
450us
I(L)
455us
I(C) I(R)
460us
465us
470us
475us
480us
485us
490us
495us
500us
Time
© Copyright Ned Mohan 2008
34
Frequency Analysis
SwitchingWaveform_AC-Analysis.Sch
© Copyright Ned Mohan 2008
35
Simulation Results
50
0
(100.000K,-45.867)
-50
-100
100Hz
1.0KHz
DB(V(vo)/V(VA))
10KHz
100KHz
1.0MHz
Frequency
© Copyright Ned Mohan 2008
36
Transistor and diode forming a switching power-pole
in a Buck converter
+
iL
Vin
+
Vo
−
−
(a)
+
iL
Vin
−
qA = 1
(b)
+
+
Vo
−
iL
+
Vo
−
Vin
−
qA = 0
(c)
Figure 1-24 Transistor and diode forming a switching power-pole in a Buck converter.
© Copyright Ned Mohan 2008
37
Hardware Lab: very low-cost
Switching Power - Pole Board
Magnetics Plug - In Board
Feedback Control Plug - In Board
Experiments:
- Buck, Boost, Buck-Boost
- Feedback Control: VoltageMode, Peak-Current-Mode
- Flyback, Forward
© Copyright Ned Mohan 2008
USERS MANUAL
www.ece.umn.edu/groups/power
38
RECENT AND POTENTIAL ADVANCEMENTS
• Devices that can handle voltages in kVs and currents in kAs
• ASICs
• DSPs
• Micro-controllers
• FPGA
• Integrated and intelligent power modules
• Packaging
• SiC-based solid-state devices
• High energy density capacitors
© Copyright Ned Mohan 2008
39
CONCEPT OF PEBB
Power Electronics Building Block (PEBB) [15] is a broad concept that
incorporates the progressive integration of power devices, gate drives,
and other components into building blocks, with clearly defined
functionality that provides interface capabilities able to serve multiple
applications. This building block approach results in reduced cost,
losses, weight, size, and engineering effort for the application and
maintenance of power electronics systems. Based on the functional
specifications of PEBB and the performance requirements of the
intended applications, the PEBB designer addresses the details of
device stresses, stray inductances, switching speed, losses, thermal
management, protection, measurements of required variables, control
interfaces, and potential integration issues at all levels.
It has numerous benefits such as technology insertion and upgrade via
standard interfaces, reduced maintenance via plug and play modules,
reduced cost via increased product development efficiency, reduced time to
market, reduced commissioning cost, reduced design and development risk,
and increased competition in critical technologies [14].
© Copyright Ned Mohan 2008
40
Summary
„
„
„
„
„
„
© Copyright Ned Mohan 2008
Power Electronics an Enabling
Technology
Applications
Need for High Efficiency and High Power
Density
Structure of Power Electronic Converters
Switching Power-Pole as the Building
Block
Potential for Advancements
41