In picture 1 we can see the circuit of the system using a synchronues generator, a diode rectifier, a dc-link step-up-chopper and an IGBT converter.
在圖1中，我們可以看到該系統的電路：同步發電機，二極管整流橋，連接在直流母線上的升壓器，一個IGBT變流器。

In picture 2 we can see an asynchronues generator with slip rings, an IGBT rectifier, a dc-link, and an IGBT converter. This system is used by some other companies.
在圖2中，我們可以看到：一個帶滑環的異步發電機，IGBT整流橋，直流母線，IGBT變流器。有一些公司使用該系統。

In Germany the first big wind turbine with variable speed had been developed in 1980 (3mW, 100m rotor diameter), but the project was to big an was not successful because of mechanical problems. At this time the cost for power semiconductors was very high, so the turbine used a double feed asynchronues generator with a small slip to save converter cost.
在德國，第一臺大型的變速風力發電（3兆瓦，轉子直徑達10米）設備誕生于1980年，但是由于機械問題，該項目并不是很成功。那時候，電力器件的成本相當的高，因此，風力發電設備就經常采用帶小滑差的雙饋異步發電機來節省變流器的成本。
Commercial wind turbines with variable speed with 750kW and more had been developed in Denmark and Germany since 1995.
真正用于商業運行的750kw變速甚至更大的風力發電設備在1995年誕生于丹麥和德國。
The Danish manufacturers had been starting with constant speed turbines. This is mainly because the wind in Denmark is more constant compared to Germany. But for turbines above 1 MW they also started to take variable speed because of problems they had with the gearboxes. But first the Danish manufacturers also used a small slip and therefore a double feed system seemed more economical.
丹尼斯設備廠開始時設計恒速風電設備。這主要是由于跟德國相比，丹麥的風速比較穩定。但是對于1兆瓦以上的風電設備，由于齒輪箱設計的問題，他們也開始采用變速方案。但是剛開始時，丹尼斯設備廠仍采用小滑差，所以雙饋系統也就比較經濟。
In 1988 the first 50kW turbine using a synchronues generator and an 6 pulse thyristor converter. Later used 12pulse converters, but this technique could not be used further on because of harmonic distortion.
1988年，第一臺50千瓦的風力發電設備是采用同步發電機和六脈沖可控硅變流器。后來，采用12脈沖變流器，但是由于諧波失真的緣故，后來這種技術就沒有再持續。

Started in 1993 with a 750kW double feed system. Many problems with the slip rings. The generator which was produced by a big Austrian company had to be changed 5 times and still did not run more than two months. After one year they gave up the double feed system and changed it to an synchronues generator. We found that the cost of the converter was not more than the double feed system because the construction is more simple.
開始于1993年的750千瓦雙饋異步系統，其中的滑差環一直存在問題，由澳大利亞一家大公司生產的發電機也修改了5次，但是運行時間仍舊不到兩個月。一年以后，他們放棄了雙饋異步系統，并把異步發電機換成同步發電機。我們發現，由于同步系統的結構變得更加簡單，因此同步系統變流器的成本并沒有比雙饋異步系統的高。