Capacity building 2010 day 2 yehia shankir sweg

RCREEE Wind Energy Building Capacity Program – Stage 2 Rabat, Tangier 29
March – 2nd April 2010
p

Review of Wind Turbines’ Drive Systems and why
Gearless Direct Drive
Gearless Direct Drive
DR Yehia Shankir

www.elsewedyelectric.com 1

Contents

1. EL Sewedy Electric & SWEG
1 EL Sewedy Electric & SWEG
2. Wind Turbines’ components and generator types
3. Wind Turbines’ drive systems advantages and
3 Wi d T bi ’ d i d d
disadvantages
4. Comparisons of Wind Turbines’ drive systems
5. Conclusions
6. Appendix
7. References

Elsewedy Electric


EL Sewedy Electric Wind
EL Sewedy Electric Wind
Sector


I‐ TOWERS

SIAG Company Overview

• The leading tubular steel tower supplier in
Germany and Europe
• Market share more than 30%
• Leading technology in steel industry
• Nearly 1000 employees
• Proven track‐record
of growth in Europe
f th i E


II‐ TURBINES
M‐Torres Company Overview
One of the most Innovative
Engineering companies in Spain
Started in the paper industries &
now one of the leaders in
supplying machines for the
aerospace industry
A total of 500 high skilled
employees

M‐Torres Wind Division
MT Wi d Di i i
2001 the first innovative
1.5 MW prototype
MTOI engineering,
MTOI engineering
manufacturing,
development, O&M


III  BLADES

Wind Rotor Blades Factory in Egypt
State of the art  production
State of the art production
technology transfer from a
leading German manufacturer.
State of the art  Blades Design
licensed by leading Dutch and
licensed by leading Dutch and
German Designers
The factory will be equipped
with the most advanced
Fiberglass moulds and
Fib l ld d
equipment to produce 200 sets
of blades in stage 1 expandable
to 500 sets
Nearly 500 employees and
technicians will be employed in
the first stage

9 www.elsewedyelectric.com 9

SWEG
EL Sewedy for Wind Energy Generation
EL S d f Wi d E G ti
the Wind Sector Arm


Wind Turbines’ components and
g
generator types
yp


Wind Turbine System Main
Wind Turbine System Main
Components
Mechanical P
M h i l Power Electrical P
El t i l Power
Wind Power Gearbox Power Converter Transformer Grid
Rotor (Optional) Generator (Optional)

Gearless Systems
Gearless Systems Geared Systems
Geared Systems
Electrical Excited Squirrel Cage
Synchronous Induction Generator
Generator (EESG)
Generator (EESG)
Types of (
(SCIG)
)
Generators
Permanent Magnet (AC Machines) Double Feed
Synchronous Induction Generator
Generator (PMSG)
Generator (PMSG) (DFIG)


Wound Rotor IM
Squirrel Cage IM
Induction Machine

+ve
T

Grid
Motor Generator
Generator
Sub Synch (+ve slip) Super synch (‐ve slip)

‐ve T
‐ve T
Motor

Operating Torque T

Synch
Speed =
120 f/ p
/p


Synchronous Generator
Synchronous Generator

Wound Rotor Permanent Magnet
Generator

Freq = P x n
/
/120

Vdc


Wind Turbines’ Drive Systems,
advantages and disadvantages
g g


The Typical Types of Drive Systems for Large
The Typical Types of Drive Systems for Large
Wind Turbines
Fixed Speed
Squirrel C
S i l Cage
Induction Generator
(SCIG)

Variable Speed
Double Feed Induction
Generator (DFIG)

Variable Speed
Electrical Excited
Synch Generator
(EESG)

Variable Speed
Permanent Magnet
Synch Generator
(PMSG)


Squirrel C
S i l Cage Induction G
I d ti Generatort
Geared, (SCIG)

Directly connected to grid ‐ve
A gearbox is required in the drive train Torque
Almost a Fixed speed. Operates in narrow
Al Fi d d O i
P=4 P=2
range of speed
The only speed control is through pole
changing which leads two rotation speeds. % of Synch Speed


Advantages of Geared SCIG

Cost
(SCIG) is a very popular machine, it has Low
specific mass (kg/kW) and smaller outer
diameter (low number of poles)hence lower
di t (l b f l )h l
cost.
Mechanical, Maintenance & Reliability
h i l i & li bili
Mechanical simplicity, robust structure


Disadvantages of Geared SCIG
Mechanical, Reliability & Maintenance Control
A gearbox in the drive train is required: No possibility of speed control, only a pole‐
Electrical & Power Quality changeable can be used ,which leads two
Directly connected to the grid
Directly connected to the grid rotation speeds.
p
SCIG would disconnect from the grid The turbine speed cannot be adjusted to the
even during quite small disturbances. wind speed to optimize the aerodynamic
They did not have any fault ride‐
Th did t h f lt id efficiency.
efficiency.`
through capability, Wind speed fluctuations are directly
The machine always requires reactive translated into electromechanical torque
power, and its value cannot be variations (no damping control), This causes
variations (no damping control) This causes
controlled. This makes it impossible to high mechanical and fatigue stresses on the
support grid voltage control therefore system (P = T . W)
no grid support,
Need different gearboxes for different
grid frequencies 50Hz / 60 Hz


Double Fed Induction Generator,
Geared, (DFIG)

Power flow in
Power flow in O
Operating
i
+ve Speed
T
Power flow out

N3 N1 N2
Directly connected to grid
Motor
‐ve Generator
Rotor Connected to grid via power T
converter Operating
Torque T
A gearbox is required in the drive train
Variable speed, Speed can be controlled
Variable speed, Speed can be controlled
within a +/‐ 30% around synchronous
speed (The converter is Feeding or
Absorbing power from/to the grid)
Absorbing power from/to the grid)


Advantages of Geared DFIG
Cost
Low specific mass (kg/kW) and smaller outer diameter (low number of
Low specific mass (kg/kW) and smaller outer diameter (low number of
poles) hence lower cost.
The converter for a DFIG is small (30% of rated power). Therefore it is
cheaper than for a direct‐drive generator.
h th f di t d i t
More complex structure than SCIG
Electrical & Power Quality
The reactive power can be controlled by controlling the rotor currents with
the converter, this allows the supply of voltage support towards the grid.
However reactive power is limited by the converter 30% rating.
However reactive power is limited by the converter 30% rating.
Control
DFIG supports a wide speed range operation, depending on the size of the
frequency converter. Typically Variable speed range is +30% around the
f t T i ll V i bl d i +30% d th
synchronous speed
In DFIG, wind gusts lead to variations in the speed without large torque
variations.

Disadvantages of Geared DFIG
Mechanical, Reliability & Maintenance
A gearbox in the drive train is required which show a reliability
negative record.
DFIG have brushes, which need regular inspection and replacement.
DFIG have brushes which need regular inspection and replacement
They are a potential cause of machine failure and losses.
Stator directly connected to grid
d l d d
According to grid connection requirements for wind turbines, in case
of grid disturbances, a ride‐through capability of DFIG is required, so
that the corresponding control strategies may be complicated.
Under grid fault conditions, on the one hand, large stator currents
result in large rotor currents, so that the power electronic converter
g , p
needs to be protected
Need different gearboxes for different grid frequencies 50Hz /60 Hz


Electrical Excited Synchronous
Generator, Gearless (EESG)

No Gearbox is required
No direct connection to the grid,
Connected through a power converter
The amplitude and frequency of the
supplied voltage can be fully controlled
The flux is fully controlled to minimize
losses in different operating ranges
Operate in a wide range of speed even
to a very low speed
to a very low speed


Advantages of Gearless EESG
Mechanical, Maintenance & Reliability The full power converter totally
The full power converter totally
No Gearbox so high reliability, less noise, decouples the generator from the
less cost, grid. Hence, grid disturbances have
DFIG have brushes, which need regular
DFIG have brushes which need regular no direct effect on the generator
no direct effect on the generator
inspection and replacement. They are a Control
potential cause of machine failure and The converter offers a wide range of
losses.
losses d l l
speed control even at very low speed d
Electrical & Power Quality therefore a higher energy yield
The converter permits flexible full control The amplitude and frequency of the
of active and reactive power in case of voltage can be fully controlled by the
normal and disturbed grid conditions. this converter
allows the supply of voltage support EESG has the opportunities of
pp
towards the grid. controlling the flux for a minimized
The same generator suitable for different loss in different power ranges
grid frequencies 50Hz / 60 Hz


Disadvantages of Gearless EESG
Cost
High specific mass (kg/kW) and Large outer diameter (high number
of poles) hence Higher cost and more weight. This weight is
partially balanced by the elimination of the gearbox.
partially balanced by the elimination of the gearbox
The converter is 100% of rated power. it is more expensive than for
a DFIG. This extra cost is balanced by the elimination of the gearbox
More complex structure than SCIG

EESG have brushes, which need regular inspection and
replacement. They are a cause of machine failure and losses.


Permanent Magnet Synchronous
Generator, Gearless (PMSG)

No direct connection to the grid,
Connected through a power converter
The amplitude and frequency of the
supplied voltage can be fully controlled
No flux control and no slip rings
because of permanent magnets
Operate in a wide range of speed even
to a very low speed
to a very low speed


Advantages of Gearless PMSG
Mechanical, Maintenance & Reliability
No Gearbox and brushes so higher The converter permits very flexible full
reliability, less noise, less cost, control of the active and reactive power in
improvement in the thermal
p case of normal and disturbed grid
characteristics of the PM machine due conditions. this allows the supply of voltage
to the absence of the field losses, support towards the grid.
Electrical & Power Quality Control
The full power converter totally The converter offers a wide range of speed
decouples the generator from the grid. control even at very low speed therefore a
Hence, grid disturbances have no direct
Hence grid disturbances have no direct higher energy yield
higher energy yield
effect on the generator The amplitude and frequency of the voltage
The same generator suitable for can be fully controlled by the converter
different grid frequencies 50Hz / 60 Hz
/ PMSG has the opportunities of controlling
PMSG h th t iti f t lli
No additional power supply for the the flux for a minimized loss in different
magnet field excitation, power ranges


Disadvantages of Gearless PMSG
Cost
High cost of PM material and Large outer diameter (high number of
poles), however this is balanced through a lower specific mass
(kg/kW) and the elimination of the gearbox.
(kg/kW) and the elimination of the gearbox
The converter is 100% of rated power. it is more expensive than for
a DFIG. This extra cost is balanced by the elimination of the gearbox
Demagnetization of PM at high temp due to sever loading or short
circuit.
Difficulties to handle in manufacture and in transportation,


Comparisons of Wind
Turbines’ Drive Systems
Turbines’ Drive Systems


Summary Comparison
Summary Comparison

Comparison base SCIG DFIG EESG PMSG If in the middle
Investment Cost, size and weight (++) (+) (-) (-)
of a desert with
Mechanical and structure Simplicity (++) (+) (-) (-)
hot sandy, and
Reliability d
R li bilit and maintenance t l
i t to lower
dusty weather
maintenance cost and increase (-) (--) (+) (++) or if offshore
availability(Gearbox and brushes)

Grid support and LVRT (-) (+) (++) (++)

Suitability for 50HZ & 60 HZ (-) (-) (+) (+)
If the point of
Speed control to damp mechanical common
(-) (+) (++) (++)
stresses connection in
Speed control to optimize
p p
aerodynamic efficiency to maximize (-) (+) (++) (++) the middle of a
energy yield complex grid
Sourcing of material and handling in
(+) (+) (-) (--)
manufacturing and transportation

Annual Energy Yield due to control ,
reliability and less down time (-) (+) (++) (++)

Cost of Kwh (Levelized Energy Cost) (-) (+) (++) (++)


Wind turbine Top Ten manufacturers and their
Wind turbine Top Ten manufacturers and their
generator types
Current
manufacturers of
Direct Drives
Turbines

3.6 MW
3.5
3 5 MW

Companies who
p
recognized the
DD concept and
now Joiningg


Conclusions
The multiple stage geared drive DFIG systems is still
The multiple‐stage geared drive DFIG systems is still
dominating the current market,
The market shows interest in the direct‐drive systems with a
full‐scale power converter. New companies recognized their
advantages and already started,
Weight, size and initial cost are higher in direct drive systems.
Weight size and initial cost are higher in direct drive systems
Overall efficiency, reliability and availability are higher in
direct drive systems because of omitting the gearbox,
Maintenance cost is higher in geared drive systems specially in
ruler area, desert, and offshore also in hot and dusty weather,
The cost of KWh is less in direct drive systems,
The cost of KWh is less in direct drive systems
In terms of grid support direct drive wind turbines with a full‐
scale power converter may be more effective and less
complicated to deal with grid‐related problems,

Nacelle Front


Nacelle Rear


Thank
Th k you for your attention
f tt ti


Appendix


Gearboxes and Reliability
• Gearboxes are one of the most expensive components of the wind turbine system,

• The higher ‐ than‐expected failure rates are adding to the cost of wind energy.

• The future uncertainty of gearbox life expectancy is contributing to wind turbine
price escalation.

• Turbine manufacturers add large contingencies to the sales price to cover the
warranty risk due to the possibility of premature gearbox failures.

• Owners and operators build contingency funds into the project financing and
income expectations for problems that may show up after the warranty expires.
Improving Wind Turbine Gearbox Reliability , Conference Paper NREL/CP‐500‐41548, May 2007

• For example, replacing a gearbox in a 1.5‐MW turbine can cost a company more
than $500,000 when you add in the price of a new gearbox, labor, crane rental, and
lost  revenue from turbine downtime.
lost revenue from turbine downtime.
http://www.windpowerengineering.com/maintenance/how-to-keep-them-worki... 3/17/2010



• The ideal voltage source provides a
g p
perfectly balanced voltage in the three
phases, a pure sine wave with a constant
frequency and magnitude.
q y g
• When these conditions are not met, it is
said that the ‘power quality’ of the grid is
deteriorated.
deteriorated
• The requirements set by the Transmission
System Operators (TSOs), are being
constantly reviewed and expanded:
constantly reviewed and expanded:
•Power quality (Constant voltage,
harmonics, flickers)
•reactive power control (power factor)
•fault ride‐through (voltage dips and
voltage swells)
g )


DFIG Control System
y


EESG & PMSG Control System
y


TWT 1.65 Poles


References
H. Polinder,,  Sjoerd W.H. de Haan, M. R. Dubois, Johannes G. Slootweg, “Basic Operation Principles and
Electrical Conversion Systems of Wind Turbines“,
J. Soens, J. Driesen, R. Belmans, “Interaction between Electrical Grid Phenomena  and the Wind Turbine's
Behaviour”, PROCEEDINGS OF ISMA 2004,
H.Li*Z.Chen, “Overview of different wind generator systems and their comparisons” Published in IET
Renewable Power Generation Received on 24th January 2007 Revisedon 23rd August 2007 doi:10 1049/iet
Renewable Power Generation Received on 24 January 2007 Revisedon August 2007 doi:10.1049/iet‐
rpg:20070044,
G Newman, S Perera, V Gosbell and V Smith,  “VOLTAGE SAG RIDE THROUGH IMPROVEMENT , OF MODERN
AC DRIVES: REVIEW OF METHODS AND A CASE STUDY”, Integral Energy Power Quality Centre,
C. Rahmann, H. J. Haubrich, L. Vargas and M. B. C. Salles, Investigation of DFIG with Fault Ride Through
C. Rahmann, H.‐J. Haubrich, L. Vargas and M. B. C. Salles, “Investigation of DFIG with Fault Ride‐Through
Capability in Weak Power Systems”, International Conference on Power Systems Transients (IPST2009) in
Kyoto, Japan June 3‐6, 2009,
, K.S.Sandhu, D.K.Jain , “LVRT of Grid Interfaced Variable Speed Driven PMSG for WECS during Fault
Rajveer Mittal”, International Journal of Computer and Electrical Engineering, Vol. 1, No. 4, October, 2009
1793‐8163,
Anca D. Hansen*, Nicolaos A. Cutululis*, Poul Sørensen*,  Florin Iov+, Torben J. Larsen, *Simulation of a
flexible wind turbine response to a grid fault”, Risø National Laboratory in cooperation with Aalborg
University,
Marta Molinas, Bjarne N
M t M li Bj Naess, William Gullvik, Tore “Cage Induction Generators for Wind Turbines with
Willi G ll ik T “C I d ti G t f Wi d T bi ith
Power Electronics Converters in the Light of the New Grid Codes”, Undeland NORWEGIAN UNIVERSITY OF
SCIENCE AND TECHNOLOGY,


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