[Presentation] Shankir - Review of Wind Turbines’ Drive Systems and why Gearless Direct Drive

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

Review of Wind Turbines’ Drive Systems and why Gearless Direct Drive

p

Gearless Direct Drive

DR Yehia Shankir

www.elsewedyelectric.com 1

Contents

1 EL Sewedy Electric & SWEG1. EL Sewedy Electric & SWEG

2. Wind Turbines’ components and generator types

3 Wi d T bi ’ d i d d3. Wind Turbines’ drive systems advantages and

disadvantages

4. Comparisons of Wind Turbines’ drive systems

5. Conclusions

6. Appendix

7. References


7. References

Elsewedy Electric


EL Sewedy Electric WindEL 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

f th i Eof growth in Europe


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 T Wi d Di i iM‐Torres Wind Division2001 the first innovative1.5 MW prototype

MTOI engineeringMTOI engineering, manufacturing, development, O&M


III BLADES

Wind Rotor Blades Factory in Egypt

State of the art productionState of the art production technology transfer from a leading German manufacturer.

State of the art Blades Design licensed by leading Dutch andlicensed by leading Dutch and German Designers

The factory will be equipped with the most advanced Fib l ld dFiberglass moulds and 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


SWEGEL S d f Wi d E G tiEL Sewedy for Wind Energy Generation

the Wind Sector Arm


Wind Turbines’ components and generator typesg yp


Wind Turbine System MainWind Turbine System Main Components

M h i l P El t i l PMechanical Power Electrical PowerWind Power Rotor

Gearbox(Optional) Generator

Power Converter (Optional)

Transformer Grid

Geared SystemsGearless Systems

Types of Electrical Excited Synchronous Generator (EESG)

Squirrel Cage Induction Generator (SCIG)

Geared SystemsGearless Systems

Generators(AC Machines)

Generator (EESG)

Permanent Magnet Synchronous Generator (PMSG)

( )

Double Feed Induction Generator (DFIG)


Generator (PMSG) (DFIG)

Wound Rotor IM

Squirrel Cage IM

Induction Machine

+ve T

Generator

T

Motor

Grid

GeneratorGenerator

‐ve T

Super synch (‐ve slip)Sub Synch (+ve slip)

Motor‐ve T

Operating TorqueT

Synch Speed = 120 f/ p


/ p

Synchronous GeneratorSynchronous Generator

Generator

Permanent MagnetWound Rotor

Generator

Freq = P x n /120/

Vdc


Wind Turbines’ Drive Systems, advantages and disadvantagesg g


The Typical Types of Drive Systems for LargeThe Typical Types of Drive Systems for Large Wind Turbines

Fixed SpeedS i l CSquirrel Cage

Induction Generator (SCIG)

Variable SpeedDouble Feed Induction

Generator (DFIG)Generator (DFIG)

Variable Speed Electrical ExcitedElectrical Excited Synch Generator

(EESG)

Variable Speed Permanent Magnet Synch Generator

(PMSG)


(PMSG)

S i l C I d ti G tSquirrel Cage Induction Generator Geared, (SCIG)

‐ve Torque

Directly connected to grid

A gearbox is required in the drive train

Al Fi d d O iP=4

Almost a Fixed speed. Operates in narrow range of speed

The only speed control is through pole

P=2

% of Synch Speedchanging which leads two rotation speeds.


Advantages of Geared SCIG

Cost

(SCIG) is a very popular machine, it has Low specific mass (kg/kW) and smaller outer di t (l b f l )h ldiameter (low number of poles)hence lower cost.

h i l i & li biliMechanical, Maintenance & Reliability

Mechanical simplicity, robust structure


Disadvantages of Geared SCIGMechanical, Reliability & Maintenance Control

A gearbox in the drive train is required:

Electrical & Power Quality

Directly connected to the grid

No possibility of speed control, only a pole‐changeable can be used ,which leads two rotation speeds. Directly connected to the grid

SCIG would disconnect from the grid even during quite small disturbances. Th did t h f lt id

p

The turbine speed cannot be adjusted to the wind speed to optimize the aerodynamic efficiency.`They did not have any fault ride‐

through capability,

The machine always requires reactive

efficiency.

Wind speed fluctuations are directly translated into electromechanical torque variations (no damping control) This causespower, and its value cannot be

controlled. This makes it impossible to support grid voltage control therefore

variations (no damping control), This causes high mechanical and fatigue stresses on the system (P = T . W)

no grid support,

Need different gearboxes for different grid frequencies 50Hz / 60 Hz


Double Fed Induction Generator, Geared, (DFIG)

O iPower flow in

Power flow out

+ve T

Operating Speed

Power flow in

Directly connected to grid

Rotor Connected to grid via power

N2

Motor‐ve T

N1

Generator

N3

converter

A gearbox is required in the drive train

Variable speed, Speed can be controlled

Operating Torque T

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 DFIGCost

Low specific mass (kg/kW) and smaller outer diameter (low number ofLow 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 h th f di t d i tcheaper than for a direct‐drive generator.

More complex structure than SCIG


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 f t T i ll V i bl d i +30% d thfrequency converter. Typically Variable speed range is +30% around the synchronous speed

In DFIG, wind gusts lead to variations in the speed without large torque


variations.

Disadvantages of Geared DFIGMechanical, Reliability & Maintenance

A gearbox in the drive train is required which show a reliability negative record.

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


d l d dStator directly connected to grid

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 , pneeds to be protected

Need different gearboxes for different grid frequencies 50Hz /60 Hz


Electrical Excited SynchronousElectrical Excited Synchronous Generator, Gearless (EESG)

No Gearbox is requiredNo 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 EESGMechanical, Maintenance & Reliability The full power converter totally

No Gearbox so high reliability, less noise, less cost,

DFIG have brushes which need regular

The full power converter totally decouples the generator from the grid. Hence, grid disturbances have no direct effect on the generatorDFIG have brushes, which need regular

inspection and replacement. They are a potential cause of machine failure and losses

no direct effect on the generator

Control

The converter offers a wide range of d l l dlosses.


The converter permits flexible full control

speed control even at very low speed therefore a higher energy yield

The amplitude and frequency of the of active and reactive power in case of normal and disturbed grid conditions. this allows the supply of voltage support

voltage can be fully controlled by the converter

EESG has the opportunities of towards the grid.

The same generator suitable for different grid frequencies 50Hz / 60 Hz

ppcontrolling the flux for a minimized loss in different power ranges


Disadvantages of Gearless EESG

CostCost

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 gearboxpartially 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

Mechanical, Reliability & MaintenanceMechanical, Reliability & Maintenance

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


Permanent Magnet SynchronousPermanent Magnet Synchronous Generator, Gearless (PMSG)

No Gearbox is requiredNo 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

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 PMSGMechanical, Maintenance & Reliability

No Gearbox and brushes so higher reliability, less noise, less cost,

improvement in the thermal

The converter permits very flexible full control of the active and reactive power in case of normal and disturbed grid p

characteristics of the PM machine due to the absence of the field losses,


conditions. this allows the supply of voltage support towards the grid.

ControlElectrical & Power Quality

The full power converter totally decouples the generator from the grid. Hence grid disturbances have no direct

The converter offers a wide range of speed control even at very low speed therefore a higher energy yieldHence, grid disturbances have no direct

effect on the generator

The same generator suitable for /

higher energy yield

The amplitude and frequency of the voltage can be fully controlled by the converter

PMSG h th t iti f t llidifferent grid frequencies 50Hz / 60 Hz

No additional power supply for the magnet field excitation,

PMSG has the opportunities of controlling the flux for a minimized loss in different power ranges


Disadvantages of Gearless PMSG

CostCost

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

Mechanical, Reliability & Maintenance

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 SystemsTurbines’ Drive Systems


Summary ComparisonSummary Comparison

Comparison base SCIG DFIG EESG PMSG If in the middleComparison base SCIG DFIG EESG PMSG

Investment Cost, size and weight (++) (+) (-) (-)

Mechanical and structure Simplicity (++) (+) (-) (-)

R li bilit d i t t l

If in the middleof a desert with hot sandy, and dusty weatherReliability and maintenance to lower

maintenance cost and increase availability(Gearbox and brushes)

(-) (--) (+) (++)

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

dusty weather or if offshore

If the point ofSuitability for 50HZ & 60 HZ (-) (-) (+) (+)

Speed control to damp mechanical stresses (-) (+) (++) (++)

Speed control to optimize

If the point of common

connection in the middle of ap p

aerodynamic efficiency to maximize energy yield

(-) (+) (++) (++)

Sourcing of material and handling in manufacturing and transportation (+) (+) (-) (--)

the middle of a complex grid

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


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

Wind turbine Top Ten manufacturers and theirWind turbine Top Ten manufacturers and their generator types

CurrentCurrent manufacturers of

Direct Drives Turbines

3 5 MW

Turbines

3.6 MW3.5 MW

Companies who precognized the

DD concept and now Joiningg


Conclusions

The multiple‐stage geared drive DFIG systems is stillThe 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 systemsWeight, 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 systemsThe 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 FrontNacelle Front


Nacelle Rear Nacelle Rear


Th k f tt tiThank you for your attention


Appendix


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

Gearboxes and Reliability

• 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 pperfectly 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 deteriorateddeteriorated.

• 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 Systemy


EESG & PMSG Control Systemy


TWT 1.65 Poles


ReferencesH. 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/ietRenewable Power Generation Received on 24th January 2007 Revisedon 23rd 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‐ThroughC. 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,M t M li Bj N Willi G ll ik T “C I d ti G t f Wi d T bi ithMarta Molinas, Bjarne Naess, William Gullvik, Tore “Cage Induction Generators for Wind Turbines with Power Electronics Converters in the Light of the New Grid Codes”, Undeland NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY,


[Presentation] Shankir - Review of Wind Turbines’ Drive Systems and why Gearless Direct Drive

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