Demonstrator #1:
Intelligent integration of wind and sun energy
(CAU, Danfoss, Beckhoff Automation, Fraunhofer ISIT)
17.03.2017
Giampaolo Buticchi, Ph.D., Young Jong Ko, Ms.C.
Chair of Power Electronics
Christian-Albrechts-Universität zu Kiel
Kaiserstraße 2
24143 Kiel
Abstract
 Smart transformer for optimal and balanced integration of renewable energy from wind
and sun into the electrical grid.
Main Grid
MVAC
Smart
Transformer
LVAC
Load DG1
DG2
ESS
Microgrid
Chair of Power Electronics
1
Abstract
 Smart transformer for optimal and balanced integration of renewable energy from wind
and sun into the electrical grid.
 In this project, the demonstrator comprising the PowerStack and the EtherCAT
constitutes a smart node.
Main Grid
Comm.
MVAC
AC
MVAC
Load DG1
DG2
LVAC
DC
AC
vA
DC
Smart
Transformer
LVAC
DC
AC
DC
AC
DC
AC
DC
AC
vB
DC
AC
ESS
DC
AC
DC
AC
AC
DC
vC
Microgrid
DC
Cascaded H-Bridge (CHB)
Chair of Power Electronics
AC
Dual Active Bridge (DAB)
DC
AC
Parallel Converter
(Power Stack)
2
Background & Deliverable results
 Background
–
–
Innocluster PowerStack as starting point
The demonstrator will join two technologies: the PowerStack and the EtherCAT Network
 Deliverable results:
–
–
–
PowerStack controlled by EtherCAT network
Centralized power management (reactive power circulation to reduce thermal cycling)
Improvement of semiconductors’ utilization by active thermal control
Chair of Power Electronics
3
PowerStack
 IGBT module
–
–
IGBT module of 1200 [V] / 600 [A]
Based on Danfoss 2L converter
 Specification
–
–
–
–
–
Rated power: 1 [MVA]
AC side voltage/current: 950 [V] / 600 [A]
DC-link voltage: 1500 [V]
Dimension: 1100*300*200 [mm]
Water cooler
 Main feature
–
–
High power density
Multilevel output
< Test bench: structure, waveform >
Chair of Power Electronics
4
EtherCAT
 Field bus system based on the Ethernet physical layer
–
Each node can read/write data on the telegram while it passes through the node
 Advantages for power converter application
–
–
–
–
Short cycle time: provides control ability at PWM level
Transmission length: up to 20km between devices by optical fiber
Synchronization in order to implement a centralized control: less than 1us
Communication mode: Master-slave, slave-slave
Configure,
Control
algorithm
TwinCAT software
Chair of Power Electronics
EtherCAT
protocol
Master:Industrial PC
Slave: FB1111
5
Demonstrator
NPC Power Stack Part
T-Type Power Stack Part
Vdc1
Vdc1
 Central Management
- through the EtherCAT
Communication
- reactive power circulation between
paralleled converters
Vdc2
Vdc2
Gate Driver
Gate Driver
ADC
PWM
Local algorithm
ADC
ia, ib, ic
vab,vbc,vca
ADC
PWM
Local algorithm
ADC
EtherCAT Slave
EtherCAT Slave
EtherCAT Master
EtherCAT
Communication
Centralized Management
< Configuration of demonstrator >
Chair of Power Electronics
6
Reliability of Power Converter
 The reliability of power semiconductor is closely associated to the themal stress.
 The number of cycles to failure is expressed with regard to the temperature variation
and the average temperature.
𝑁𝑓 = 𝑎1 · Δ𝑇𝑗
−𝑎2
𝑎3
· ⅇ 𝑇𝑗,𝑚𝑒𝑎𝑛
 Here, a1 and a2 are parameters determined by experimental data and a3 is a constatnt
calculated with the activation energy and the Boltzmann constant.
Chair of Power Electronics
7
Reactive Power Circulation
 Principle and its impact on the loss distribution
S1
D1
Pc
From
wind turbine
S2
-Qm
Under-excited by -Qm
D3
Pc1 D2
20.6%
22.3%
34%
Pc2
Over-excited by +Qm
+Qm
< Principle of reactive power circulation>
Chair of Power Electronics
22.3%
< Loss distribution with different reactive powers>
[1] Reactive power control to improve reliability of high wind power converters connected in parallel,
EWEA 2016
8
Reactive Power Circulation
10.55 m/s
Chair of Power Electronics
 Thermal cycling on S2
Δ21°C→ Δ15°C (under-excited)
Δ21°C→ Δ16°C (over-excited)
 Thermal cycling on D1
Δ16°C→ Δ21°C (under-excited)
Δ16°C→ Δ10°C (over-excited)
Over-excited
12 m/s
Under-excited
Wind profile
12 m/s
Without reactive power
 Simulation results – impact on the thermal cycling
[1] Reactive power control to improve reliability of high wind power converters connected in parallel,
EWEA 2016
9
Multi-frequency power routing
 Three-stage smart transformer architecture
 One of power paths can be experiencing a premature wear-out
Cascaded H-Bridge (CHB)
Parallel Converter (Power Stack)
Dual Active Bridge (DAB)
MVAC
LVAC
AC
DC
DC
AC
PA
vA
DC
DC
AC
Cell A
AC
DC
vB
AC
Power path1
DC
AC
PB
DC
DC
AC
Cell B
AC
DC
vC
AC
AC
Power path2
DC
PC
DC
Cell C
AC
DC
AC
Power path3
Power routing algorithm
Chair of Power Electronics
[2] Multi-frequency power routing for cascaded h-bridge inverters in smart transformer application,
ECCE 2016
10
Multi-frequency power routing
 Multi-frequency power routing
Unbalanced #1
Unbalanced #2
m
et
ho
d
Duty cycle
(cell A)
Balanced
en
cy
ol
ta
ge
am
en
ta
lv
m
ul
tif
fu
By
35%
nd
By
Vgrid / VDC
re
qu
Duty cycle
(cell B)
Duty cycle
(cell C)
Power (%)
30%
Completely
unloaded
Cell A,B,C
Cell A,B
Cell A,B
Cell C
Cell C
PC / PC,bal
Time (s)
Time (s)
Time (s)
< Principle of imbalance power routing by multi-frequency>
Chair of Power Electronics
< Cell unloading capability >
[2] Multi-frequency power routing for cascaded h-bridge inverters in smart transformer application,
ECCE 2016
11
Multi-frequency power routing
 Power flow among cells by power routing
PA=PA,bal
DC
Cell B
AC
Cell A
AC
PA<PA,bal
DC
Cell B
AC
PB>PB,bal
DC
Cell C
AC
PC=PC,bal
DC
< Balanced loading >
Chair of Power Electronics
Internal power
routing
PB=PB,bal
DC
Cell C
AC
MVAC
Cell A
AC
PA>PA,bal
DC
Cell B
AC
PB<PB,bal
Internal power
routing
MVAC
Power exchanged
with the grid
Cell A
AC
Power exchanged
with the grid
Power exchanged
with the grid
MVAC
DC
Cell C
AC
PC<PC,bal
PC>PC,bal
DC
< unloading cell A >
DC
< overloading cell A >
[2] Multi-frequency power routing for cascaded h-bridge inverters in smart transformer application,
ECCE 2016
12
Multi-frequency power routing
 Experimental results – duty cycles and output current
Duty cycle
Duty cycle
Cell A, B, C
max
Duty cycle
Cell A, B
max
Cell A, B
Cell C
Cell C
< Balanced loading >
Chair of Power Electronics
min
min
min
Output current
Output current
max
Output current
+10A
+10A
+10A
-10A
-10A
-10A
< Unbalanced loading
by fundamental >
< Unbalanced loading
by multi-frequency>
[2] Multi-frequency power routing for cascaded h-bridge inverters in smart transformer application,
ECCE 2016
13
Multi-frequency power routing
 Experimentla results - power of each cell
 Impact of power routing on the damage in the power semiconudctor
Without power routing
90
Mission profile
i gri d
100
↓98 %
PA+PB+PC
80
70
75
60
50
40
55
20
50
70
10
45
0
40
Time
vB
50
40
100
90
30
Cell C
Cell A
Cell B
Cell C
Cell A
Cell B
Cell C
Cell B
Cell A
10
0
Time
vC
PC
Power [%]
20
80
70
60
By fundamental
voltage
By multi-frequency
method
< Power measurement of each cell>
Chair of Power Electronics
Time
PB = PC
PA
50
40
30
20
Balanced
65
60
80
60
10
0
Time
1000
70
30
PB
Comparison of damage
85
80
Tj [ºC]
↓82 %
Power [%]
90
vA
PA
Junction temperature in DC/DC converter
90
Tj,cellA = Tj,cellB = Tj,cellC
Tj [ºC]
↑43 %
Balanced
Power [%]
Output Power [W]
↑40 %
System
PA+PB+PC
90
85
80
75
70
65
60
55
50
45
40
Tj,cellB
= Tj,cellC
Tj,cellA
Relative accumlated damage [%]
Power in cells
100
286 %
Cell B,C
100
10
Cell A,B,C
100 %
No power
routing
Cell A
21 %
Power routing
(unload cell A)
Time
With power routing (unload cell A)
< Effect of power routing on the normed damage
in the power semiconductor >
[2] Multi-frequency power routing for cascaded h-bridge inverters in smart transformer application,
ECCE 2016
14
Thank you for your attention
Chair of Power Electronics
15