2. 2Challenge the future
EPP
Electrical Power Processing
Content
• Introduction
• Renewable energies offshore
• Wave energy innovation
• Need for the DC grids
8. 8Challenge the future
EPP
Electrical Power Processing
• Higher average wind speeds at sea
• Space limitations on shore
• The turbines will on average have a larger
diameters and rated powers
• Less turbulence and lower wind shear
• Erection and maintenance will be more expensive
• Turbine noise will probably not be an important
issue
• Submarine electrical connection to shore
• The farm will be difficult to access during periods
with high winds
EPP
Electrical Power Processing
9. 9Challenge the future
EPP
Electrical Power Processing
9
gear-
ASG
box
f
a) direct grid connection
(normal plant for grid operation)
n= (1-s) f/p s~ 0...0.8 (output dependent)
inductive reactive power consumer
~
1) with thyristor converter 2) with pulse inverter
n~ 0.8 1.2 f/p (controllable)
1) inductive reactive power consumer
gear-
box
b) grid connection via direct-current intermediate circuit
ASG
~
f
2) controllable reactive power output
DC
c) grid connection via direct ac converter
inductive reactive power consumer
gear-
box
n~ 0.8 1.2 f/p (controllable)~
ASG
f
d) dynamic slip control
(output dependent, dynamic)
gear-
box
n= (1-s) f/p s~ 0... 0.1... (0.3)~
ASG
f
inductive reactive power consumer
e) oversynchronous static Kraemer system
inductive reactive power consumer
gear-
box
n~ 1...1.3 f/p (controllable)~
ASG
f
n
n
n
n
n
box
controllable reactive power output
n~ .8...1.2 f/p (controllable)~
f) double fed asynchronous generator
gear-
ASG
n f
controllable reactive power output
n= f/p
box
gear-
SG
n f
g) direct grid connection
h) coupling to direct current grid
SG
gear-
box
n~ 0.5...1.2 n
n uDC
~ N
~n~ 0.5...1.2 f/p (controllable)
i) grid connection via direct-current intermediate circuit
ngear-
box
SG
f
1) with thyristor converter 2) with pulse inverter
1) inductive reactive power consumer
2) controllable reactive power output
n~ 0.5...1.2 f/p (controllable)
1) with thyristor converter 2) with pulse inverter
j) grid connection via direct-current intermediate circuit
~
2) controllable reactive power output
1) inductive reactive power consumer
n
SG
f
DC
DC
k) grid connection via direct-current intermediate circuit
~
1) with thyristor converter 2) with pulse inverter
n~ 0.6...1.2 f/p (controllable)
1) inductive reactive power consumer
2) controllable reactive power output
n
DC
f
l) grid connection via direct ac converter
~n~ 0.8...1.2 f/p (controllable)
(partial) reactive power consumer
n f
conversion system with asynchronous generator (ASG) conversion system with synchronous generator (SG)
short-circuitrotormachinesslipringrotormachines
permanentlyexcitedmachinesmachineswithexcitationsystem
(normal plant for independent operation)
*
*
*
19. 19Challenge the future
EPP
Electrical Power Processing
Introduction
Wave Generators – EAPWEC
(1)
(2) (3)
“Snake” made of rolled DE material and filled
with water
20. 20Challenge the future
EPP
Electrical Power Processing
Introduction
Electro Active Polymer – Dielectric Elastomer (DE)
• Actuator - If a voltage is applied to the electrodes electrostatic forces will squeeze the
dielectric elastomer material and reduce in thickness and expand in area
• Sensor - Stretching the DE material will change area and thickness resulting in a change
in capacitance which can be measured
• Generator - If a stretched DE film is charged and then relaxed the voltage will increase
significantly; converting mechanical energy to electrical energy
DE STRETCHED
DE CONTRACTED
contraction
large capacitance
low voltage
low energy state
small capacitance
high voltage
high energy state
21. 21Challenge the future
EPP
Electrical Power Processing
Principle of operation
• Energy is generated as the
charged electroactive polymer
decreases in area and increases in
thickness as it contracts
Variable capacitor generator
Energy = ½ Qo
2 (1/Cr - 1/Cs)
C = εr εo x film area/film
thickness
+ + + + +
_ _ _ _ _
+Vin (lo)+Vout
(high)
EAP STRETCHED
+ + + + +
_ _ _ _ _
+Vin (low)+Vout
(high)
Dielectric Elastomer
Compliant Electrodes (2)
EAP CONTRACTED
22. 22Challenge the future
EPP
Electrical Power Processing
Introduction
• Constant voltage
• Constant charge
• Constant electric field
Methods for Energy Harvesting
T
Cs
Cc
0
10 kV
0
Id
Ic
tcharge tdischarge
∆tc
∆td
∆qc
∆qd
• Current shape optimization for
the optimum energy harvesting
cycle
23. 23Challenge the future
EPP
Electrical Power Processing
Introduction
Power Take Off System
• Low voltage DC bus of 800 V
• Maximum power output per segment 10 kW
• High power PEU required, 100 kW peak power rating
• Target efficiency of PEU >95%
• Bidirectional power flow capability of the PEU
24. 24Challenge the future
EPP
Electrical Power Processing
Medium-voltage dc-dc topologies
1) Two Quadrant Converter – Boost-Buck (2QC)
2) Flying Capacitor Multilevel Converter (FCMC)
3) Cascade Multilevel Converter (CMC)
4) Boost-Buck Multilevel Converter (B/BMC)
5) Multiphase Boost-Buck Converter (MPC)
• Final decision will be made based on a total ranking of the converter based
on multiple criteria
25. 25Challenge the future
EPP
Electrical Power Processing
Medium-voltage dc-dc topologies
• High efficiency at low switching
frequencies and low VDE
• Simple control
• Stacking of switches neccessary
• High current switches
• High current ripple through CDE
• Huge inductor size
1) Two Quadrant – Boost/Buck
26. 26Challenge the future
EPP
Electrical Power Processing
V2V1
Lk
S3
S1
S2 S4
S7S5
S6 S8
iLk
vT1 vT2
1:n
DAB1
DAB2
DABN
VBUS
VGEN
DAB module
I1 I2
V1 V2
• Input parallel output series converter with DABs
• Very wide output voltage range
• Variable frequency trapezoidal control method for DABs
27. 27Challenge the future
EPP
Electrical Power Processing
0 1000 2000 3000 4000 5000 6000
85
87
89
91
93
95
97
99
power [W]
effciency[%]
parallel
bypass
Comparison of parallel and bypass module
control method using efficiency curves
0 500 1000 1500 2000
85
87
89
91
93
95
97
99
power [W]
effciency[%]
Efficiency curve of the module and
combination of parallel and bypass methods
– hybrid method
DAB
module 2
DAB
module 1
Controller
DAB
module 3
bypass
VGEN
c o n t r o l s i g n a l s
28. 28Challenge the future
EPP
Electrical Power Processing
Medium-voltage dc-dc topologies
• DAB circuit for balancing of
intermediate capacitor
• Medium-voltage transformer
• ZCS and ZVS
• Low current switches
• Simple control
• Low current ripple through CDE
• Different control methods
• Transformer for every module
needed
• Low efficiency at low VDE
3) Cascade Multilevel
32. 32Challenge the future
EPP
Electrical Power Processing Electrical
Maximum allowable load current as
a function of cable length
Itot RI
R,maxI
l
maxI
IR,max = Imax - IC
= Imax – U/wC’ length
Power Processing
36. 36Challenge the future
EPP
Electrical Power Processing
• 1882
• 1882 The world’s first power transmission over a long distance was based on
DC. The first transmission was from Miesbach to Munich – by Oskar von Miller
and Marcel Deprez: 57 km, 1.4 kV
• 1945: World’s first DC transmission project by Siemens and AEG: 115 km
cable, mercury-arc based link from the power station Elbe/Elektrowerke AG to
Bewag/Berlin at 60 MW / ±200 kV, ready for commissioning, but then
transported to Russia …
History of DC power Transmission
• 1945
J.Dorn Siemens
37. 37Challenge the future
EPP
Electrical Power Processing J.Dorn Siemens
HVDC advantages
Long overhead lines with high transmission Capacity,
low transmission losses and reduced right-of-way
Cable transmissions with low losses and without limitation in length
Asynchronous grids can be interconnected
Increase of transmission capacity without increasing short circuit currents
Fast control of power flow, independent from AC conditions
Firewall against cascading disturbances, active power oscillation damping
39. 39Challenge the future
EPP
Electrical Power Processing
J.Dorn Siemens
• HVDC Classic
• Line comutated CSC
• Thyristors with turn on
Capability only
• VSC HVDC
• Self commutated VSC
• Semiconductor Switches with torn
on and turn off - IGBT
42. 42Challenge the future
EPP
Electrical Power Processing
• Long distance overhead
• DC submarine cable
• Back to Back
HVDC Applications
J.Dorn Siemens
47. 47Challenge the future
EPP
Electrical Power Processing
Control of HVDC Transmission System
• Inverter is operated at the minimum extinction
angle and the rectifier in the current-control mode
52. 52Challenge the future
EPP
Electrical Power Processing
Multilevel
reduced semiconductor voltage
- Lower harmonic distortion
- More levels possible (multi
level)
