Wind energy I. Lesson 5. Wind turbines general

Windenergy 2010/11

Windenergy 2010/11

Windenergy 2010/11

Windenergy 2010/11

cp(lambda)

Windenergy 2010/11

basic scheme of a wind turbine

• wind - rotor - gear box - generator - grid integration

there are different concepts around:

different generators, multiple poles, synchronous or asynchronous

Windenergy 2010/11

aerodynamics

rotor

cp(!)

Wind

power class

FT , T

P,!R

Ug

fg

!g

Tg

drive - train powergenerator

.FT thrustT torqueTg torque of generatorP power!R rotation speed of rotor!g rotation speed of generatorUg grid voltagefg grid frequency

support structureFT

Center for Wind Energy Research

Turbine

hub main shaft

nacelle

gearbox

high speed shaft

generator

electrical / control system


Turbine

hub main shaft

nacelle

gearbox

high speed shaft

generator

electrical / control system

Windenergy 2010/11

design of wind turbine - resolved design

Windenergy 2010/11

design of wind turbine - resolved design

high speed shaftdisplaced - not in a line with main

shaft - why?

Windenergy 2010/11

• gear box

Windenergy 2010/11

compact - gearless design

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redundant design

Windenergy 2010/11

from Twele

Windenergy 2010/11

aerodynamics

rotor

cp(!)

Wind

power class

FT , T

P,!R

Ug

fg

!g

Tg



support structureFT

extreme events ... foundation


installation of a windturbinefoundation concepts


installation of a windturbinefoundation

research: load measurements

Windenergy 2010/11


5MW WEC - electr. energy for about 10.000 to 20.000 persons

area = 12469 m2


installation of a windturbinefoundation

transport - logistics


construction



testung centers for foundation and blades


testung centers for foundation and blades

Windenergy 2010/11


investigation of the ground


floating WECs


floating WECs


floating WECs


floating WECs

Windenergy 2010/11

power generator

aerodynamics

rotor

cp(!)

Wind

power class

FT , T

P,!R

Ug

fg

!g

Tg



support structureFT

Windenergy 2010/11

generator

• electric generator‣ transforms mechanical motion (power) into electric power P=UI‣ Faraday‘s law of induction

- changing magnetic field- generates voltage (emf)

‣ rotating magnet causes oscillating voltage out put

‣ demonstration

Uind = !d!dt

Windenergy 2010/11

synchronous / asynchronous generator

• synchronous‣ the frequency of the generator out is entirely fixed by the turbine

rotational frequency (wind) through the gearbox. Thus the output voltage frequency is synchronous with the high speed shaft frequency

‣ Wind turbines which use synchronous generators normally use electromagnets in the rotor which are fed by direct current from the electrical grid. Since the grid supplies alternating current, they first have to convert alternating current to direct current before sending it into the coil windings around the electromagnets in the rotor. The rotor electromagnets are connected to the current by using brushes and slip rings on the axle (shaft) of the generator.

Windenergy 2010/11

synchronous / asynchronous generator

• asynchroneous or cage or indiction generator‣ the frequency of the generator output is controlled by the

excitation from the main supply. Consequently the turbine rotation speed can vary slightly and is not exact synchoneous through the generator with the grid. The normal generator for this is an induction genertaor with magnetic excitation drawn from the grid

‣ the asynch. generator was designed as a motor but works also as generator. Its advantage is that is it very simple

further details see http://www.windpower.org/en/tour/wtrb/electric.htm

http://www.windpower.org/en/tour/wtrb/electric.htm

http://www.windpower.org/en/tour/wtrb/electric.htm

Windenergy 2010/11

reactive power

• due to complex resistance u and I get out of phase leading to reactive power - not useable

• additional impedence (inductivity for capacitance) can neutralize this - this can be achieved by synchronous generators


next decade : offshore

technical challenges / steps

wind potential - ground - selection of WEC - foundation - construction - grid connection - operation and maintenance



cables - grid connection



platform alpha ventus



platform alpha ventus


new cables GIL (gas isolated conductors)


new cables GIL (gas isolated conductors)

Windenergy 2010/11

aerodynamics

rotor

cp(!)

Wind

power class

FT , T

P,!R

Ug

fg

!g

Tg



control system

pitch support structureFT

Windenergy 2010/11

• loads:‣ aerodynamic‣ gravitational ‣ - 600 kW machine will rotate some 2 108 times during a 20 year life

Windenergy 2010/11

• loads:‣ aerodynamic‣ gravitational‣ inertia - gyroscope, precession,

Windenergy 2010/11

• loads:‣ aerodynamic‣ gravitational‣ inertia - gyroscope, precession,

troque !" = !r ! !Fg

d!L

dt= !"

‣ Rotor must be well balanced - support in the center of mass

Windenergy 2010/11

• loads:‣ aerodynamic‣ gravitational‣ inertia - gyroscope, precession, centrifugal‣ operating loads - generator, brakes, yaw and pitch control‣ extreme loads - 50 year gust

- 3 or 5 sec gust = factor (1.4) * 50 year 10 min speed value‣ loss of load due to disconnection from grid + 1 year gust

- speed up until break sets in‣ tower shadow

Windenergy 2010/11

• classification of wind turbines IEC 61400‣ class I to IV

‣ class A - higher - B lower degree of turblence

• GL - includes load • danish standard DS 472

Windenergy 2010/11

• dynamic load and eigenmodes => resonances

• --- back board

Windenergy 2010/11

Windenergy 2010/11


Windenergy 2010/11

• spectral analysis of signals• rotational frequency• eigen modes at .4 Hz

Windenergy 2010/11

• spectral analysis of signals• rotational frequency• eigen modes at .4 Hz

closer to resonance

Windenergy 2010/11


Windenergy 2010/11

• dynamic load and eigenmodes => ressonances

Windenergy 2010/11

end

Windenergy 2010/11

10th lecture 14th of Jan

• control system purpose‣ to guarantee steady power production‣ to prevent damage in high wind speed‣ to keep mechanical loads minimal‣ to stay below max power given by the design of the

generator

• basic aspects‣ control of power production‣ emergency -

- high wind speed periods- interruption of grid connection (no load by generator)- emergency brake

Windenergy 2010/11

• simple control systems

Windenergy 2010/11

Windenergy 2010/11

t [sec]

u [m

/s]

0 1000 2000 3000 4000 5000 6000 7000

35

79

t [sec]

P [k

W]

0 1000 2000 3000 4000 5000 6000 7000

100

400

t [sec]

u [m

/s]

0 1000 2000 3000 4000 5000 6000 7000

1020

t [sec]P

[kW

]0 1000 2000 3000 4000 5000 6000 7000

1300

1700

t [sec]

u [m

/s]

0 1000 2000 3000 4000 5000 6000 7000

612

18

t [sec]

P [k

W]

0 1000 2000 3000 4000 5000 6000 7000

600

1400

●● ● ● ●

●●

●●

●

●

●

●

●

●

●

●●

●

●

2 4 6 8 10 12 14 16

0.0

0.2

0.4

0.6

0.8

1.0

● ● ● ● ●●

●●

●

●

●

●

●

●

●

●

●●

●● ●

●● ● ● ●

● ● ● ● ● ●●

●●

●

●

●

●

●

●

●

●

●●

●●

●● ● ● ●

un [m/s]

PP r

●

●

LIDAR, IECLIDAR, Dynamic

Windenergy 2010/11

control system

• regular (non emergency control)‣ control quantities

- angle of attack- rotation speed (tip speed ratio)

‣ pitch control, passive pitch‣ stall control, active stall‣ rotor orientation‣ tip speed ratio

- Black borad details and tranparencies

Windenergy 2010/11

• control cases‣ fixed speed - fixed pitch‣ fixed speed - variable pitch‣ variable pitch - fixed pitch‣ variable speed - variable pitch

- explained by P(u); cp(lambda), cp(u) doagrams- - details on blackboard

Wind energy I. Lesson 5. Wind turbines general

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