Power Electronics and Converters

wideeyedarmenianElectronics - Devices

Nov 24, 2013 (3 years and 8 months ago)

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Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
1
Power Electronics and Converters
Power Electronics and Static Converters

Static
≠ Electrical Machines

Power Semiconductor Devices

Switches and Control (Drivers)
Electric
Energy
Source
Electric
Load
Power
Converter
General Power Scheme (Efficiency)
losses
losses
control
P
IN
P
OUT
Q
CONV
Q
LOAD
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
2
Power Electronics Devices
Ideal Switches

(Electro-)Mechanical
i
v
off-state
on-state
i
v
off
on
i
v
off
on
Four quadrants
= fully bidirectional
off
K
ctrl
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
3
Ideal Switches (2)
Device Name
Device function
Quadrants
Associated
Real Devices
Ideal Diode
Forward-conducting Reverse-blocking
Bipolar or
Schottky
diodes
Reverse
blocking
controlled
switch
Forward-conducting and Reverse-
blocking controlled switch
Thyristor, GTO,
BJT, IGBT
Reverse
Conducting
Controlled
Switch
Bidirectional-conducting and Forward-
blocking controlled switch
MOSFET, JFET
Fully
bidirectional
controlled
Switch
Bidirectional-conducting and
Bidirectional-blocking controlled switch
Electro-
mechanical
switch
i
v
off
on
i
v
off
on
i
v
off
on
i
v
off
on
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
4
Power Electronics Principles
1-Switching
E
R
K
T
OFF
ON
t
ON
t
OFF
Duty ratio
α
=
t
ON
T
ON
+
t
OFF
=
t
ON
T
Switching Period
T
=
T
ON
+
t
OFF
2-Smoothing
With passive elements
3-Freewheeling
E
R
K
L
L
Spark & arc when K opens !
E
R
K
L
C
Freewheel diode
Buck Converter
For Chopping
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
5
Real Switches: common characteristics

Voltage rate: forward and reverse modes

Current rate (cooling)

Switching times: turn-on and turn-off

Lifetime: degradation, Nb Of Operations
On current
On drop voltage
On (dynamic)
Resistance
Short Circuit Current
Breakdown Voltage
BV
F
I
ON
MAX
First quadrant (IGBT)
i
v
saturation


BV
F
I
L
OFF
V
F
ON
I
F
ON
R
ON
I
F
ON
V
F
ON
(
I
F
ON
)
R
ON
(
I
F
ON
)
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
6
Real Switches: Technologies
Electromechanics: relays

Electromagnet

Moving part

Voltage rate: 10 V → 30 kV

Current rate: 1 A → 300 A

Switching times: 3 ms → 30 ms

Nb Of Operations: 10
4
→ 10
7

Leakage current: resistance > 1 G
Ω

Circuit Breakers (arc interruption)
Vacuum Tube Switches

Historically replaced by Solid State Switches (Semiconductor)

Except for very high voltage
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
7
Power Semiconductor Devices
Made on a semiconductor
crystalline substrate, a wafer.
Diodes:

PIN and Schottky Diodes
Insulated Gate Transistors:

(Power) MOSFET

Insulated-Gate Bipolar Transistor, IGBT
Other Transistors:

Bipolar Junction Transistor, BJT,

Thyristors and Gate Turn-Off Thyristor, GTO

MOS Controlled Thyristor,MCT,

Junction Field Effect Transistor, JFET

High electron mobility transistor, HEMT
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
8
Semiconductors for Power Devices
E
G

(eV)
Band gap
E
c
(MV/cm)
Critical
Field
µ
n
(cm²/V/s)
Electron
mobility
µ
p

(cm²/V/s)
Hole mobility
σ
T
(W/cm/K)
Thermal
conduction
Si
1.12
0.3
1400
450
1.3
SiC-4H
3.25
3.2
950
120
7.0
GaN
3.44
3.0
900
10
1.1
Diamond
5.5
5.7
2200
1800
~1000
Role
V
BI
BV, V
BR
R
ON
(MOS)
R
ON
(BJT)
Cooling
Interest for
PIN,
Thyristor,
GTO,
MCT,IGBT
all
MOSFET,
IGBT
BJT,
Thyristor,
GTO, MCT,
IGBT
all
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
9
Physics of Semiconductor Devices

Free (from the crystal) charges: carriers, electrons, n(x,t) and holes p(x,t),

Doping impurities: one fixed ion + one free carrier,

N-type doping creates fixed positive charges + electrons, N
D
(x)

P-type doping creates fixed negative charges + holes, N
A
(x)

Generation mechanisms: Energy → electron-hole pairs, n
i
(T)

Recombination mechanisms: electron-hole pairs → Energy,
τ
n
,
τ
p
,

Electric charges may generate electric fields (Space charge Region),

Drift-Diffusion mechanism rules the transport of carriers,

J
n
=
q

n
n

E

u
T

grad
n

J
p
=
q

p
p

E

u
T

grad
p

E
µ
n
and µ
p
are the electron and hole mobilities
u
T
=
k
B
T
q
Thermal potential, (~ 26 mV @ 300 K)
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
10
PN junction theory (Shockley)
anode
cathode
i
v
E
-E
M
-x
A
x
D
ξ
A
ξ
A

v
u
B
ψ
v
A
v
D
P
N
+
+
-
-
Desertion hypothesis
u
B
=
q
N
D
w
2
2

v
=
v
BI

u
B
Barrier height
u
B
0
=
v
BI
=
u
T
log
(
N
A
N
D
n
i
2
)
At equilibrium
v
BI
=
E
G
q
+
u
T
(
ln
(
N
A
N
D
n
i
300K
)

3
ln
(
u
T
u
T
300K
)
)

u
G
V
BI
, building potential
V
BI
~ 1 V (Si), 3 V (SiC)
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
11
Power
Bipolar
& Schottky Diodes
i
v

V
BR
I
L
OFF
V
F
ON
I
F
ON
µA
V
BI
Reverse scale
Forward
scale
V
BR
, breakdown voltage (E
C
)
i
v
off
on
Ideal Diode
I
L
OFF

I
F
ON
V
BI

V
BR
1
A
<
I
F
ON
<
3
kA
60
V
<
V
BR
<
200
V
(
Schottky
Si
)
V
F
ON

V
BI
Independent on V
BR
!
6.5
kV
(
Si
)
20 kV (SiC)
τ
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
12
Power Bipolar & Schottky Diodes (2)
(Schottky Diodes)
trr ~
τ, ambipolar lifetime
100
ns
<
τ
<
100
μ
s
Fast PIN diode: 100 ns,
BJT, Thyristor, GTO, MCT: 1 µs – 100 µs
Zener diode =avalanche diode
A bipolar device = very robust for current overload !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
13
Bipolar Junction Transistor, BJT
i
C
v
CE
BV
CE0
linear-mode
Breakdown
Hard
Sat.
quasi-saturation
BV
0
BV
RCE
i
v
off
on
base
collector
emitter
i
C
i
B
v
CE
v
BE
h
FE
=
β
=
i
C
i
B
=
2
τ
n
μ
n
u
T
W
B
2
Current Gain
BV
CE0
collector-emitter sustaining
Voltage,
Second breakdown ...
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
14
Bipolar Junction Transistor,
B
JT (2)

Problem of the parallel connection

Low switching speed,
τ

Current Driver (base)
Silicon BJT (old fashioned)
200 V – 2000 V
1 A – 100 A
SiC BJT (Fairchild 2011)
1200 V –
15 kV
10 A –
100 A
Issues
Interests

Very low on-losses

Good temperature dependence
emitter
base
collector
J
EB
J
BC
N
P
N
i
B
R
C
V
CC
i
C
v
CE
v
BE
NXP
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
15
Thyristor, SCR, GTO, MCT, TRIAC
anode
cathode
gate
v
AK
i
A
i
G
i
A
v
AK
BV
0
Breakdown
BV
0
BV
RCE
i
H
v
H
i
v
off
on
SCR = Silicon Control Rectifier = Thyristor
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
16
Thyristor, SCR, GTO, MCT, TRIAC (2)

Sensitive to dv/dt, avalanche

Low switching speed,
τ

Pulsed Current Driver (gate)
Silicon Thyristor
600 V – 6.5 kV
10 A – 5 kA
SiC Thyristor
10 kV – 20 kV
10 A – 100 kA
Issues
Interests

Very robust on current overload
Powerex/Misubishi
1.5 kA – 12 kV
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
17
Junction Field Effect Transistor, JFET
Only for SiC (2011) !
1200 V, 50-300 m
Ω
i
D
v
DS
V
BR
Breakdown
linear-mode
saturation
R
DS
ON
Body diode conduction
Normally-on devices
Alternative to IGBTs
High temperature
operation
Low losses !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
18
Power MOSFET
MOSFET: Metal Oxide Semiconductor Field Effect Transistor
i
D
=
K
P
(
v
GS

V
T

v
DS
2
)
v
DS
K
P
=
W
L
μ
n
ϵ
ox
d
ox
i
D
SAT
=
K
P
2
(
v
GS

V
T
)
2
i
D
v
DS
V
BR
Breakdown
linear-mode
saturation
R
DS
ON
Body diode conduction
G
D
S
i
D
i
G
v
DS
v
GS
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
19
Power MOSFET (2)
VISHAY

Weak robustness in short-circuit

No high voltage ~ 600 V (silicon)

The gate is sticky
Issues
Rating

Fast and simple switching

Standard Gate Driver
Interests
1 A – 200 A
60 V – 800 V
Trench-MOSFET, CoolMOS ...
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
20
Insulated Gate Bipolar Transistor, IBGT
Non Punch Through
Punch Through
Trench-IGBT
Collector
i
G
i
C
V
CE
V
GE
Gate
Emitter
Equivalent
Circuits

Best one !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
21
IBGT (2)
i
C
v
CE
BV
CES
Breakdown
saturation
BV
CES
V
BI

Weak robustness in short-circuit

The gate is sticky

Slower than MOSFET
Issues
Rating

Standard Gate Driver
Interests
10 A – 100 A
600 V – 6.5 kV
Trench-IGBT
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
22
Summary on Power Semiconductor Devices

Resistive-like
Devices

MOSFET,
JFET, BJT,
HEMT

Specific on-
resistance
Not convenient for
IGBTs !
Die parallelization
enables a reduction of
the on-losses.
600 V
Si MOSFET
1200 V
INFINEON JFET
CREE
MOSFET
COOLMOS
FAIRCHILD
BJT
SEMISOUTH
JFET
IR GaN HEMT
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
23
The battle of the technologies

Wide band gap versus silicon technologies

silicon : superjunction or trench IGBT

SiC :
low losses
, high temperature

GaN :
low losses
, low cost
600V
1200V
> 2000V
Si-Superunction
SiC
GaN
Si-IGBT
SiC
GaN
SiC
L. Lorentz, INFINEON, SiC & GaN Forum, Birmingham, 2011
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
24
Thermal Managment
Thermal Resistance
T
J

T
A
=
Δ
T
=
R
TH
Q
Q, heat flow (W)
T
J
, junction temperature (°C, K),
T
A
, ambient temperature (°C, K),
Δ
T, temperature difference,
R
TH
, thermal resistance (K/W)
Static Diffusion of heat in
Solids,
R
TH
=
h
λ
A
h, thickness of the layer (cm),
A, area of the considered layer (cm²),
λ
, thermal conductivity
material
λ
(Wcm
-1
K
-1
)
Aluminium oxide, Al2O3
0.3
Aluminum Nitride, AlN
2.8
Copper, Cu
4.0
material
λ
(Wcm
-1
K
-1
)
Silicon, Si
1.5
Silicon Carbide, SiC
4.0
AlSiC
~ 2
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
25
Packaging
Wire bond
Semiconductor die
joint
Conducting layers (Cu)
Ceramics
base-plate
heat-sink
Thermal Resistance, Thermal Capacitance
gel
Reliability issue
Temperature cycling (active, passive),
Difference in CTEs
(Coefficient of thermal expansion)
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
26
IGBT Modules
1.2 kA, 3.3 kV
Mitsubishi
Half-bridge modules,
Full-bridge modules,
40 A, 160 W
TO220
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
27
Rectifiers, AC-DC Converters
Single-Phase Half-wave Rectifier

V
L

=
2
π
V
M
=
2

2
π
V
RMS

0.900
V
RMS
Case of the inductive load !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
28
Rectifiers, AC-DC Converters (2)
3-phase Bridge rectifier

V
L

=
3

6
π
V
RMS

V
L


2.34
V
RMS
N
DC-bus filtering

V
L

=
3

6
2
π
V
RMS
With a double ripple !
3-phase Star rectifier
With a capacitor !
But power factor corrector,
PFC may be required
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
29
Rectifiers, AC-DC Converters (3)
Three Phase Full Bridge Rectifier,
Graetz's Bridge

V
D

=
3

2
π
cos
α
U
sec

1.35
cos
α
U
sec
U
sec
=
V
f

f
sec
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
30
Step-Down or Buck Converter
E
R
K
L
C
V
OUT
V
IN
At steady state,
T
OFF
ON
t
ON
t
OFF
V
OUT
=
α
V
IN
α
=
t
ON
T
0

α

1
Averaged Model
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
31
Step-Down or Buck Converter (2)
i
L
t
i
L
t
Continuous Conduction Mode
Discontinuous Conduction Mode
Condition for operation in DCM:
2
L
T
<
(
1

α
)
R
CCM
DCM
V
t
Δ
V
OUT
<V
OUT
>
Ripple in CCM at steady state
C
>
1

α
8

V
OUT

Δ
V
OUT
T
2
L
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
32
Forward & Flyback Converters
Forward Converter
=
A buck converter
With a transformer !
n
=
N
1
N
2
V
OUT
V
IN
=
2
α
n

D
3
, demagnetization diode
Magnetic Energy Flow in one way !
In the Fly-back converter, the
transformer is a temporary energy
storage element.
n
=
N
1
N
2
V
OUT
V
IN
=
α
n
(
1

α
)
High ratio
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
33
Boost & Buck-Boost Converters
Condition for operation in DCM:
2
L
T
<
(
1

α
)
2
α
R
Capacitor sizing
C
>
α

V
OUT

Δ
V
OUT
T
R
Boost Converter
V
OUT
=

α
1

α
V
IN
Buck-Boost Converter
Condition for operation in DCM:
2
L
T
<
(
1

α
)
2
R
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
34
Choppers ...
Synchronous Buck Converter
To reduce the on-losses due
to diode D.
Need an advanced control !
Cuk Converter
V
OUT
=

α
1

α
V
IN
Condition for operation in DCM:
2
L
1
T
<
(
1

α
)
2
α
R
2
L
2
T
<
(
1

α
)
2
R
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
35
Single phase Inverters
Single-Phase Voltage Source Inverter
PWM = Pulse Width Modulation
SPWM = Sinusoidal Carrier PWM
Role of dead times
Other modulation techniques:
Space Vector Modulation, SVM,
Direct Control Strategy...
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
36
3-Phase Voltage Source Inverters
Dead-time role
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
37
Soft, snubbered & Hard Switching
Hard Switching
:
May generate EMI
Losses ?
Snubber
:
Passive element to slow down
The switching.
RC snubbers, … diode
Soft-switching :
Switching transitions occur under favorable conditions – device
voltage or current is zero
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
38
Resonant Converters
Quasi resonant Buck Converter
ZVC-QRC
Zero Voltage Condition Quasi
Resonant Converters
ZCV-QRC
Zero Current Condition Quasi
Resonant Converters
Applications
High frequency converters
Reduction of the passive elements,
But more complex control !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
39
Converter losses
On-losses:
Off-losses:
Q
ON
=
V
ON
(
I
ON
)
I
ON
Q
OFF
=
V
OFF
I
OFF
(
V
OFF
)
Switching Losses: ?
First Law of Thermodynamics
dU
dt
=
i
v

Q
On one cycle,

0
T
i
v
dt
=

Q

T

Q

=
Q
ON
+
Q
OFF
+
E
OFF
turn
+
E
ON
turn
T
datasheets
Role of the frequency
f
=
1
T
Interaction with EMC
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
40
Applications
Uninterruptible Power Supply,
UPS
PV system connected to an

AC-grid
SiC Inverters !
Power Engineering – IMESI - 2012
Hervé Morel
http://hmorel.ampereforge.org – IMESI/2012
41
Applications
Renewable Energy and DC-bus
Most of the Office/home loads are
DC-loads !
Wind Power Variable Speed