For variable-speed systems with limited variable-speed range, e.g. ±30% of synchronous speed, the doubly-fed induction generator(DFIG) can be an interesting solution. This is mainly due to the fact that the power electronic converter only has to handle a fraction (20-30%) of the total power as the converters are connected to the rotor and not to the stator. Therefore, the losses in the power electronic converter can be reduced, compared to a system where the converter has to handle the total power. The overall structure of wind power generation through DFIG as shown in the figure below.
=Market Research=
==Major Players==
Vestas Wind Systems, General Electric and Gamesa Innovation & Technology are the top players in terms of installed power capacity in the year 2007.
{|border="2" cellspacing="0" cellpadding="4" width="100%"
|align = "center" bgcolor = "#4F81BD" width="38"|<font color="#FFFFFF">'''S.No.'''</font>
|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Company'''</font>
|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Installed Capacity'''(MW)</font>
|-
|align = "center" bgcolor = "#DCE6F1"|1
|bgcolor = "#DCE6F1"|Vestas (Denmark)
|align = "right" bgcolor = "#DCE6F1"|4,500
|-
|align = "center"|2
|GE Energy (United States)
|align = "right"|3,300
|-
|align = "center" bgcolor = "#DCE6F1"|3
|bgcolor = "#DCE6F1"|Gamesa (Spain)
|align = "right" bgcolor = "#DCE6F1"|3,050
|-
|align = "center"|4
|Enercon (Germany)
|align = "right"|2,700
|-
|align = "center" bgcolor = "#DCE6F1"|5
|bgcolor = "#DCE6F1"|Suzlon (India)
|align = "right" bgcolor = "#DCE6F1"|2,000
|-
|align = "center"|6
|Siemens (Denmark/Germany)
|align = "right"|1,400
|-
|align = "center" bgcolor = "#DCE6F1"|7
|bgcolor = "#DCE6F1"|Acciona (Spain)
|align = "right" bgcolor = "#DCE6F1"|870
|-
|align = "center"|8
|Goldwind (China - PRC)
|align = "right"|830
|-
|align = "center" bgcolor = "#DCE6F1"|9
|bgcolor = "#DCE6F1"|Nordex (Germany)
|align = "right" bgcolor = "#DCE6F1"|670
|-
|align = "center"|10
|Sinovel (China - PRC)
|align = "right"|670
|-
|}
Source:[http://www.mywindpowersystem.com/2009/04/the-10-major-wind-power-companies-in-the-world/ Wind power companies]
==Market Overview==
* The world's wind industry defied the economic downturn in 2008 and by he end of the year 2009, the sector saw its annual market grow by 41.5% over 2008, and total global wind power capacity increased by 31.7% to 158GW in 2009.
* US, China and Germany together hold more than 50% of the global wind power capacity.
* Asia and North America have seen tremendous growth in the installed wind power capacity over the last 6 years.
* Asia was the world's largest regional market for wind energy with capacity additions amounting to 15.4GW. China was the world's largest market in 2009, more than doubling its capacity from 12.1GW in 2008 to 25.8GW, adding a staggering 13.8GW of capacity.
* China and the US account for more than 60% of the new installed capacity of 38.3GW in 2009. India's total installed capacity increased to 10.9GW with 1.3GW of new installed capacity in 2009.
* The 2009 market for turbine installations was worth about 45 bn € or 63 bn US$ and about half a million people are now employed by the wind industry around the world.
{|border="0" cellspacing="0" cellpadding="4" width="100%"
|[[Image:wind energy Installed capacity1 2009.png|center|450px|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Top 10 Cumulative Installed Capacity 2009]''']]
|[[Image:wind energy New capacity1.png|center|450px|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Top 10 New Installed Capacity 2009]''']]
|-
|}
[[Image:Region Capacities1.png|800px|center|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Annual Installed Capacity by Region 2003-2009]''']]
==Market Forecast==
* Global wind power capacity could reach 2,300 GW by 2030, providing up to 22% of the world's electricity needs, from the existing 2.2% in 2010.
* Global wind capacity will stand at 409GW up from 158GW at the end of 2008. During 2014, 62.5 GW of new capacity will be added to the global total, compared to 38.3 GW in 2009
* The annual growth rates during this period will average 20.9% in terms of total installed capacity, and 10.3% for annual market growth
* Three regions will continue to drive the expansion of wind energy capacity: Asia, North America and Europe
* Asia will remain the fastest growing market in the world, driven primarily by China, which is set to continue the rapid upscaling of its wind capacity and hold its position as the world’s largest annual market. Annual additions are expected to be well over 20 GW in China by 2014
* Sustained growth is also expected in India, which will increase its capacity steadily by 2 GW every year, and be complemented by growth in other Asian markets, including Japan, Taiwan, South Korea and the Philippines, and potentially some others
* By 2014, the annual market will reach 14.5 GW, and a total of 60 GW will be installed in Europe over this five year period
[[Image:Market forecast.png|800px|center|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Annual market forecast by region 2009-2013]''']]
<br>
Source:[http://www.gwec.net/index.php?id=167 GWEC's Global Wind Report 2009]
==Company Profiles==
# '''[[Vestas Wind Systems A/S]]'''
#[[Suzlon Energy]]
#'''[[GE Energy]]'''
= Doubly-fed Induction Generator: Search Strategy =
|}
=Market Research=
==Major Players==
Vestas Wind Systems, General Electric and Gamesa Innovation & Technology are the top players in terms of installed power capacity in the year 2007.
{|border="2" cellspacing="0" cellpadding="4" width="100%"
|align = "center" bgcolor = "#4F81BD" width="38"|<font color="#FFFFFF">'''S.No.'''</font>
|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Company'''</font>
|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Installed Capacity'''(MW)</font>
|-
|align = "center" bgcolor = "#DCE6F1"|1
|bgcolor = "#DCE6F1"|Vestas (Denmark)
|align = "right" bgcolor = "#DCE6F1"|4,500
|-
|align = "center"|2
|GE Energy (United States)
|align = "right"|3,300
|-
|align = "center" bgcolor = "#DCE6F1"|3
|bgcolor = "#DCE6F1"|Gamesa (Spain)
|align = "right" bgcolor = "#DCE6F1"|3,050
|-
|align = "center"|4
|Enercon (Germany)
|align = "right"|2,700
|-
|align = "center" bgcolor = "#DCE6F1"|5
|bgcolor = "#DCE6F1"|Suzlon (India)
|align = "right" bgcolor = "#DCE6F1"|2,000
|-
|align = "center"|6
|Siemens (Denmark/Germany)
|align = "right"|1,400
|-
|align = "center" bgcolor = "#DCE6F1"|7
|bgcolor = "#DCE6F1"|Acciona (Spain)
|align = "right" bgcolor = "#DCE6F1"|870
|-
|align = "center"|8
|Goldwind (China - PRC)
|align = "right"|830
|-
|align = "center" bgcolor = "#DCE6F1"|9
|bgcolor = "#DCE6F1"|Nordex (Germany)
|align = "right" bgcolor = "#DCE6F1"|670
|-
|align = "center"|10
|Sinovel (China - PRC)
|align = "right"|670
|-
|}
Source:[http://www.mywindpowersystem.com/2009/04/the-10-major-wind-power-companies-in-the-world/ Wind power companies]
==Market Overview==
* The world's wind industry defied the economic downturn in 2008 and by he end of the year 2009, the sector saw its annual market grow by 41.5% over 2008, and total global wind power capacity increased by 31.7% to 158GW in 2009.
* US, China and Germany together hold more than 50% of the global wind power capacity.
* Asia and North America have seen tremendous growth in the installed wind power capacity over the last 6 years.
* Asia was the world's largest regional market for wind energy with capacity additions amounting to 15.4GW. China was the world's largest market in 2009, more than doubling its capacity from 12.1GW in 2008 to 25.8GW, adding a staggering 13.8GW of capacity.
* China and the US account for more than 60% of the new installed capacity of 38.3GW in 2009. India's total installed capacity increased to 10.9GW with 1.3GW of new installed capacity in 2009.
* The 2009 market for turbine installations was worth about 45 bn € or 63 bn US$ and about half a million people are now employed by the wind industry around the world.
{|border="0" cellspacing="0" cellpadding="4" width="100%"
|[[Image:wind energy Installed capacity1 2009.png|center|450px|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Top 10 Cumulative Installed Capacity 2009]''']]
|[[Image:wind energy New capacity1.png|center|450px|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Top 10 New Installed Capacity 2009]''']]
|-
|}
[[Image:Region Capacities1.png|800px|center|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Annual Installed Capacity by Region 2003-2009]''']]
==Market Forecast==
* Global wind power capacity could reach 2,300 GW by 2030, providing up to 22% of the world's electricity needs, from the existing 2.2% in 2010.
* Global wind capacity will stand at 409GW up from 158GW at the end of 2008. During 2014, 62.5 GW of new capacity will be added to the global total, compared to 38.3 GW in 2009
* The annual growth rates during this period will average 20.9% in terms of total installed capacity, and 10.3% for annual market growth
* Three regions will continue to drive the expansion of wind energy capacity: Asia, North America and Europe
* Asia will remain the fastest growing market in the world, driven primarily by China, which is set to continue the rapid upscaling of its wind capacity and hold its position as the world’s largest annual market. Annual additions are expected to be well over 20 GW in China by 2014
* Sustained growth is also expected in India, which will increase its capacity steadily by 2 GW every year, and be complemented by growth in other Asian markets, including Japan, Taiwan, South Korea and the Philippines, and potentially some others
* By 2014, the annual market will reach 14.5 GW, and a total of 60 GW will be installed in Europe over this five year period
[[Image:Market forecast.png|800px|center|thumb| Fig '''[http://www.gwec.net/index.php?id=167 Annual market forecast by region 2009-2013]''']]
<br>
Source:[http://www.gwec.net/index.php?id=167 GWEC's Global Wind Report 2009]
==Company Profiles==
# '''[[Vestas Wind Systems A/S]]'''
#[[Suzlon Energy]]
#'''[[GE Energy]]'''
=Key Findings=