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A comparison of low voltage and medium voltage wind turbine drive trains

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A comparison of low voltage and medium voltage wind turbine drive trains EWEC 2010, April 22, Warsaw by Anders Troedson, The Switch Introduction/drivers for medium ... – PowerPoint PPT presentation

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Title: A comparison of low voltage and medium voltage wind turbine drive trains


1
A comparison of low voltage and medium voltage
wind turbine drive trains
EWEC 2010, April 22, Warsaw by Anders Troedson,
The Switch
2
Presentation outline
  • Introduction/drivers for medium voltage (MV)
    drive trains
  • Performance
  • Technology issues
  • Topologies
  • Devices IGBT and IGCT packaging
  • Cooling
  • Cable cost comparison
  • Maintenance and service
  • Reliability
  • Pros and cons
  • Costs
  • Summary

3
General information
  • The presentation focuses on the preferred drive
    train technology using full-power converters
  • This material is particularly applicable for the
    preferred permanent magnet generator drive train
  • Both, the low voltage (LV) and MV converters
    discussed herein are liquid-cooled.
    Liquid-cooling preferred for multi MW converters
    due to more compact size and easiness to adapt to
    a severe environment, particularly off-shore
  • The MV power converter discussion focuses on
    so-called press pack power devices (either IGBT
    or IGCT), which are currently the prevalent MV
    device packaging

4
Drivers for medium voltage power converters
  • Potential to reduce converter size and weight
  • Potential for reduced cable cost unless power
    converters can be installed in the tower
  • Fewer electric components
  • Smaller filters using multi-level converter
    topologies
  • Benefits with medium voltage converters come at a
    cost
  • Higher cost for equipment
  • Often more complex cooling system using press
    pack devices
  • Current LV designs are more robust
  • Maintenance / service technician must be
    qualified for MV

5
Low voltage and medium voltage converters
Wind turbine power converters
Medium voltage (2 KV, 3.3 KV and higher)
Low voltage (400, 480, 500, 600 690 Volts)
Industrial drives
Medium voltage ( 2KV, 3.3 KV and higher)
Low voltage (400, 480, 500, 600 690 Volts)
kW
0
1500
3000
4500
6000
6
4 MW direct-driven PMG and low voltage (690 V)
full-power converter
7
6 MW drive train comparison LV and MV
6 MW LV (690 V) full-power converter system for
wind turbine
6 MW MV (3300 V) full-power converter for wind
turbine
8
Converter topologies for LV and MV
  • Low voltage (up to 690 Volts AC)
  • 2-level converter with LV IGBT modules
  • Medium voltage (gt1000 V AC)
  • NPC multi level converters (3 and 5-level
    topologies)
  • 3-level diode clamped NPC converter
  • 3-level capacitor clamped NPC converter
  • 3-level H-bridge NPC converter
  • Cascaded converters using multiple 3-phase
    modules
  • Different hybrid topologies

9
690 V full-power converter system
Permanent magnet DD generator and full-power
converter
10
Medium voltage full-power converter 3-level MV
full-power converter with IGCTs
3-level NPC full-power converter (3300 Volts)
Converter diagram courtesy ABB
11
Size comparison 6 MW converters
MV LV wind turbine converters
Medium voltage 4160 V 4.32 sq.m. (1.6 cubic
meter / MW)
Low voltage 690 V 6.38 sq.m. (2.3 cubic meter /
MW)
  • Winkelnkemper, Wildner Steimer, 6 MVA
    Five-Level Hybrid Converter for WindPower, IEEE
    2008
  • The Switch 690 V Power Converter for 6 MW
    Turbine

12
690 V and 3,300 V full-power converters
Full-power converter for 690 V from The Switch
Inverter section of 3.3 KV ABB full-power
converter
Picture courtesy ABB
13
Press pack versus IGBT modules
  • Press pack (MV) IGBT IGCT
  • More compact converter design (packaging)
  • More efficient heat transfer
  • Heat sink on voltage potential - hot heat sinks
  • Requires own separate internal cooling loop with
    higher complexity
  • IGBT module (LV MV)
  • Design with integral cold plate
  • Heat sink on ground potential
  • Enables simpler and more rugged cooling system

14
Components for low and medium voltage
MV press pack IGBT / IGCT
IGBT modules for LV MV

15
Cooling system comparison LV and MV

Flow diagram Liquid-cooling system for MV power
converter
Flow diagram Liquid-cooling system for LV power
converter
16
Cooling system considerations
Medium voltage w/ press pack
Low voltage
  • Cooling system is more forgiving/robust
  • Drinking water quality with glycol is typical
  • Heat sinks on ground potential
  • Aluminum or stainless steel cooling system
    preferred, but copper/ brass also possible
  • De-ionized water required with glycol
  • Must maintain low coolant conductivity needs
    special deionizer
  • Hot heat sinks potential for electrolysis
  • More stringent material requirements for cooling
    components

17
5 MW system - power cable comparison Tower to base

18
Reliability
Factor Low voltage Medium voltage
Component count
Corona effects
Effects of possible condensation -
Cooling system robustness

Reliability (MTBF) is more than fundamental
theoretical calculations it is also a matter
of design and consideration for ambient
conditions, installation and service and the
robustness of the technology
19
Pros and cons of LV versus MV
Low voltage Medium voltage
Cost
Physical size and weight
Cable cost incl. stress cones lugs
Control features performance
LVRT
Efficiency Typ. 97.5 Typ. 97.5
Partial redundancy
Cooling system design requirements -
Servicing, safety training requirements - -
Maintenance -

20
Other design considerations
  • Multi-level topologies, used primarily for MV,
    helps keeping filters smaller and reduces torque
    ripple
  • Switching frequencies are lower for MV (IGCT 500
    1000 Hz) while LV IGBT is switching at 3000
    5000 Hz
  • Higher switching frequency lowers filter
    (inductor) sizes
  • Corona effect increases with the voltage ex.
    properly made cable connections and use of stress
    cones required
  • MV is even more sensitive than LV to condensation
    and moisture
  • Effective anti condensation features becomes
    increasingly important with higher system voltages

21
Costs
  • MV converters up to 5 MW are still significantly
    more expensive than corresponding LV power
    converters
  • Premium costs for 5 MW medium voltage power
    converter is at least 25
  • Costs are therefore NOT a major driver towards
    medium voltage power converters size and weight
    are

22
Summary
  • Full-power converters with permanent magnet
    generators is the preferred drive train solution
    for new turbine designs
  • Full-power converters have superior fault
    ride-through performance (LVRT) and with
    permanent magnet generators offer maximum energy
    yield
  • Performance for LV and MV are essentially the
    same
  • Medium voltage power converters increased
    popularity above 5 MW
  • Installed cost for MV exceeds that of LV
    converters
  • LV power converters are available up to at least
    6 MW
  • LV converters offer partial redundancy
  • MV power converters more costly, but reduced
    size and weight
  • Low voltage converters are more service proven.
    LV technology offers a more robust design

23
Questions are welcome
  • Äyritie 8 C
  • FI-01510 Vantaa
  • Finland
  • Tel 358 20 783 8200
  • www.theswitch.com
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