Wind Power Generation Schemes

WIND POWER
GENERATION SCHEMES
S.VIGNESH, BTG-12-037
Dr.S.Pugalendhi, Professor & Head (BIO ENERGY)
ERG 354 - Wind Energy Conversion Technology & Energy Storage (2+1) 1

IN PRESENTATION
1/6/2015 - MONDAY
1. Wind Energy Conversion – Introduction
2. Deciding Factors – Electrical Generator
3. Schemes for electric generation
4. Conclusion
5. Reference

INTRODUCTION
ERG 354 - Wind Energy Conversion Technology & Energy Storage (2+1)
3
 Aero turbines convert Wind energy into rotary Mechanical energy.
 The Controller senses the Wind direction, speed, power output of the
generator and necessary performance quantities of the system and
initiates appropriate control signals to take suitable corrections.
Wind
WT GC EG
Controller
To load utility grid
Speed
Pitch
Control

3 FACTORS
 The Choice of an generator and control method to be employed can be
decided by consideration of the following three factors ;
I. The basis of operation i.e., either constant tip speed or
constant tip speed ratio.
II. The wind-power rating of the turbine,
III. The type of load demand., e.g. Battery connection
 The electrical control strategy employed for any particular SCHEME can
be designed to effect control of the generator, the power transmission
link.

SCHEMES FOR ELECTRIC GENERATION
I. Constant speed - Constant frequency systems (CSCF)
II. Variable speed - Constant frequency systems (VSCF)
III. Variable speed - Variable frequency systems (VSVF)
1.Constant speed constant frequency system (CSCF)
It has been used for large generators connected directly to the grid
where constant frequency operation is essential.
1. a.Synchronous Generator
2. b.Induction Generator

1.a.Synchronous Generator - For such machines the requirement of
constant speed is very rigid and only minor fluctuations about 1% for
short durations could be allowed.
2.a.Induction Generator – If the stator of an induction machine is
connected to the power grid and if the rotor is driven above
synchronous speed Ns the machine becomes a generator and delivers
constant line frequency power to the grid. (f=line frequency & p=No of
poles for which the stator winding is made). The per unit slip is 0 and
0.05, the output power of wind driven induction generator is uniquely
determined by the operating speed.

2.VARIABLE SPEED CONSTANT FREQUENCY SCHEME
 It is typical for most small wind generators used in
autonomous applications, generally producing variable
frequency and variable voltage output.
 The variable speed operation of wind electric system
yield higher outputs for both low and high wind speeds.
This results in higher annual energy yields per rated
installed KW capacity.

Double output
induction generator
AC-DC-AC
Link
AC
Commutation
generator

2.a. AC-DC-AC Link - With the advent of high powered thyristors and
high voltage d.c transmission systems, a.c output of the 3 phases
alternator is rectified using a bridge rectifier and then converted back to
a.c using line commutated inverters. They utilize an a.c source which
periodically reverses polarity and causes the commutation to occur
naturally.
wind
Wind turbine
gearing &
coupling
Alternator
Rectifier
Inverter
3
P
h
a
s
e
g
r
i
d

 2.b. Double Output induction generator – In this system a slip-
ring induction motor is used. Rotor power at slip frequency is
converted to line frequency power by rectification and inversion
output power is obtained both from stator and rotor and hence
this device is called double output induction generator.

2.c. A.C. Commutation generator – This system is also
known as Scherbius system employs two polyphase
windings in the stator and a commutator winding on the
rotor. Basic problems in employing this device for wind
energy conversion are the cost and additional
maintenance and care required by the commutator and
the brush gear.

3.Variable Speed variable frequency (VSVF)
 Since resistive heating loads are essentially frequency
insensitive, the a.c generator can be effected at a variable
frequency corresponding to the changing derive speed. For this
purpose capacitor excited squirrel caze induction machines can
be conveniently used.

 These systems are gaining importance for stand alone wind
power applications. The magnitude and frequency of the EMF
depends on the value of the load impedance, prime mover
speed and excitation capacitance.
 The varying output voltage can be converted to constant d.c
using choppers or controlled rectifiers on constant a.c using
force commutated inverters.

CONCLUSION
 The electrical control strategy employed for any particular
SCHEME can be designed to effect control of the generator,
the power transmission link or the load.

REFERENCES
 www.energyschemes.in
 www.engineeringblogspot.com
 Non-Conventional Energy Sources – G.D.Rai
 Wind Energy Explained - Wiley

Wind Power Generation Schemes

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