Advanced Wind Turbine Program Next Generation Turbine ... - NREL

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The advantage of this system is that from 70%–80% of the power is produced by the stator, which is connected directly to the electrical grid without need of power conversion. Only the 20%–30% of the power derived from the rotor requires power conversion. This arrangement allows for variable speed operation of the wind turbine rotor, thereby maximizing energy capture, while allowing the use of a power converter sized for only 20%–30% of the wind turbine rated power. Partial power conversion improves the system efficiency (i.e., energy production) while significantly reducing the cost of the power electronics. Furthermore, 4- and 6-pole induction generators and motors are widely manufactured and relatively inexpensive. In moving away from the baseline drive train configuration, the designer can work with five key parameters: • Generator synchronous speed and the corresponding required gearing • Type of generator • Number of generators • Speed regulation (variable speed or fixed speed) • Power conversion options. Table 1 summarizes the configuration options associated with each parameter and the anticipated cost and performance trade-offs that have motivated the studies of these options. A total of 216 permutations of the configurations shown in Table 1 exist. However, many of the permutations obviously can be eliminated. For example: • The direct-drive option only works with one generator. The use of multiple generators requires multiple output shafts from a gearbox. • Only the wound rotor induction generator can utilize partial power conversion. • Fixed speed operation requires no power conversion. Table 2 summarizes the 36-drive train configurations examined in the present study. Every configuration in Table 2 does not need to be examined separately, because several of the design parameters can be changed independently. For example: • Changing from variable speed to fixed speed operation will impact the aerodynamic energy capture similarly regardless of the drive train configuration. • Changing from variable speed to fixed speed operation will eliminate the power converter regardless of whether the generator is direct-drive, medium speed, or conventional speed. • Use of multiple generators should not significantly impact the cost of the power converter, as the cost of the latter is mostly a function of the total power rating. • Use of multiple generators should not significantly impact the energy capture. As a result of these assumptions, the field of candidate configurations for study have been narrowed to 11 categories, as defined in Table 2. These 11 categories of drive train configurations are each discussed in the following subsections 2.1.1 through 2.1.3. A summary of the COE impacts on proposed design changes is summarized in Section 2.1.4. 5
Table 1. Summary of the Key Drive Train Design Parameters and Configurations Options Parameter Configuration Options Trade-offs Performance Cost Generator Synchro • Low-Speed (Direct-Drive • gearboxes represent a • multi-stage gearboxes repnous Speed Generator) significant source of resent a significant fraction • Medium-Speed (Single mechanical loss of the cost of a wind tur Stage Gearbox) • gearboxes represent a bine • Conventional (1200 or significant source of • unconventional generators 1800 for 60 Hz, 1000 or maintenance require can be expected to be more 1500 for 50 Hz) ments expensive. Type of Generator • Wound rotor induction • Squirrel cage machines • Squirrel cage and wound generator and synchronous ma- rotor synchronous ma • Squirrel cage induction chines either require full chines are widely manufac generator power conversion or tured and easily manufac • Wound rotor synchronous must be operated fixed tured, making them very generator speed. Both options low-cost options. • Permanent magnet syn will reduce energy cap • Permanent magnet machronous gen. ture.chines can be very compact and hence relatively low cost Speed Regulation • Variable Speed • Fixed speed operation • Fixed speed operation • Fixed Speed generally results in a eliminates the need for ex loss of several percent of energy capture pensive power converters Number of Genera • Single Generator • Multiple generators • Use of more and smaller tors • Multiple Generators might allow a better generators might provide a coupling of the aerody small manufacturing cost namic (rotor) power – savings due to economies vs– wind speed curve and the generator power –vs– shaft speed curve, improving efficiency of scale Power Conversion • Full Power Conversion • Rectifying and inverting • The more power for which • Partial Power Conversion more power will result the converter is sized, the • No Power Conversion in greater power losses more expensive it will be. 6
Page 1 and 2: National Renewable Energy Laborator
Page 3 and 4: NOTICE This report was prepared as
Page 5 and 6: Abstract This document reports the
Page 7 and 8: In addition to innovations resultin
Page 9 and 10: 3.2.3 Mechanical Loads Testing of t
Page 11 and 12: List of Symbols and Abbreviations A
Page 13 and 14: The SOW also stipulates that GE see
Page 15: 2.1 Electromechanical Systems Conce
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Page 21 and 22: other than the wound rotor inductio
Page 23 and 24: offer compelling advantages to COE.
Page 25 and 26: cluded that the same would likely b
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Page 29 and 30: Figure 5. Fatigue Damage Equivalent
Page 31 and 32: 2.3 Rotor and Structural Design Con
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Page 35 and 36: Percent Change in Load Percent Chan
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Page 49 and 50: 2.3.5 Boundary Layer Control GE com
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Page 53 and 54: Table 3. Proof of Concepts Turbine
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least 20 years of equivalent loadin
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3.2.1 Power Performance Testing of
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Maxi mum Ti p Speed (m/s) Sound Pow
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Table 6. Engineering & Manufacturin
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GE briefly considered the costs and
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Figure 38. EMD 37-m (GE37a) Blade 6
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Development of the concept required
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Bench tests verified PLC control mo
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4.3.2 Mechanical Loads Testing of t
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5 Commercialization of GE NGT Techn
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F1146-E(12/2004) REPORT DOCUMENTATI
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Advanced Wind Turbine Program Next Generation Turbine ... - NREL

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