EPE Association: EPE 2005 - Topic 14-ETGb: Wind converter technologies 2

EPE 2005 - Topic 14-ETGb: Wind converter technologies 2
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2005 - Conference > EPE 2005 - Topic 14: POWER ELECTRONICS IN ELECTRICAL ENERGY GENERATING SYSTEMS > EPE 2005 - Topic 14-ETGb: Wind converter technologies 2

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   Bearing Currents in Doubly-Fed Induction Generators
By STUPIN Peter; ZITZELSBERGER Johann; HOFMANN Wilfried [View]
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Abstract: An increasing demand on the quality of wind power systems affects also more and more the fields of lifetime and reliability. But, problems like bearing damages because of bearing currents counteract these desired demands. Especially doubly fed induction generators, which are wide spread in use for wind turbines up to the MW-class can be limited in reliability because of the mentioned problem. Hereby,the rotor-side feeding by IGBT voltage source inverters causes an uprise of bearing currents. Unfortunately, this parasitic effect, well known from stator-side inverter-fed machines, is different and maybe even worse since the capacitive voltage divider, responsible for the transfer of the common mode voltage to the bearings, differs to a great extend. The analysis of bearing current circuits given in this paper will help to explain these differences. Moreover, some fundamental modelcharacteristics of doubly-fed induction generators will be mentioned in order to give hints for measures against bearing currents. Measured effects gained from a 1.5 MW generator support these investigations and evaluate the efficiency or the problems of measures for decreasing bearing currents.

   Grid Connection of Active Stall Wind Farms using a VSC based DC Transmission System
By SORENSEN Poul; BLAABJERG Frede; HANSEN Anca Daniela; IOV Florin [View]
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Abstract: Currently, there is an increasing trend to connect large MW wind farms to the transmission system. Requirements that focus on the influence of the farms on the grid stability and power quality, and on the control capabilities of wind farms have already been established. The main trends of modern wind turbines/farms are clearly the variable speed operation and a grid connection through a power electronic interface, especially using doubly fed induction generators. Using power electronics the control capabilities of these wind turbines/farms are extended and thus the grid requirements are fulfilled. However, the traditional squirrel-cage generators based wind turbines/wind farms directly connected to the grid have less control capabilities. These wind turbines/farms cannot regulate their production and contribute to power system stability. A DC transmission system for connection of the active stall wind farms to the grid can provide these features and also maximize the produced power especially at low wind speeds by using variable voltage/frequency for the wind farm. The focus in this paper is in studying the operation for the active stall wind farms using a voltage source converter based DC transmission system as well as the power quality issues of the generated power.

   Medium Voltage Converter for Permanent Magnet Wind Power Generators up to 5 MW
By FAULSTICH Alexander; STEINKE JueRgen K; WITTWER Fritz [View]
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Abstract: Wind turbines equipped with a permanent magnet excited synchronous generator have to be connected to the utility grid via a full-scale converter. Medium voltage technology tends to be more suitable for high power systems. The flexibility of full-scale converter-based systems allows easy adaptation to different grid requirements. In recent years the continuously increasing number of wind energy plants brought into operation forced the transmission system operators (TSO) to tighten their grid connection rules in order to limit the effects on network quality. These new rules demand that wind energy plants and farms support the electricity network throughout their operation.

EPE 2005 - Topic 14-ETGb: Wind converter technologies 2
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2005 - Conference > EPE 2005 - Topic 14: POWER ELECTRONICS IN ELECTRICAL ENERGY GENERATING SYSTEMS > EPE 2005 - Topic 14-ETGb: Wind converter technologies 2
	[return to parent folder]

	Bearing Currents in Doubly-Fed Induction Generators By STUPIN Peter; ZITZELSBERGER Johann; HOFMANN Wilfried	[View] [Download]
Abstract: An increasing demand on the quality of wind power systems affects also more and more the fields of lifetime and reliability. But, problems like bearing damages because of bearing currents counteract these desired demands. Especially doubly fed induction generators, which are wide spread in use for wind turbines up to the MW-class can be limited in reliability because of the mentioned problem. Hereby,the rotor-side feeding by IGBT voltage source inverters causes an uprise of bearing currents. Unfortunately, this parasitic effect, well known from stator-side inverter-fed machines, is different and maybe even worse since the capacitive voltage divider, responsible for the transfer of the common mode voltage to the bearings, differs to a great extend. The analysis of bearing current circuits given in this paper will help to explain these differences. Moreover, some fundamental modelcharacteristics of doubly-fed induction generators will be mentioned in order to give hints for measures against bearing currents. Measured effects gained from a 1.5 MW generator support these investigations and evaluate the efficiency or the problems of measures for decreasing bearing currents.

	Grid Connection of Active Stall Wind Farms using a VSC based DC Transmission System By SORENSEN Poul; BLAABJERG Frede; HANSEN Anca Daniela; IOV Florin	[View] [Download]
Abstract: Currently, there is an increasing trend to connect large MW wind farms to the transmission system. Requirements that focus on the influence of the farms on the grid stability and power quality, and on the control capabilities of wind farms have already been established. The main trends of modern wind turbines/farms are clearly the variable speed operation and a grid connection through a power electronic interface, especially using doubly fed induction generators. Using power electronics the control capabilities of these wind turbines/farms are extended and thus the grid requirements are fulfilled. However, the traditional squirrel-cage generators based wind turbines/wind farms directly connected to the grid have less control capabilities. These wind turbines/farms cannot regulate their production and contribute to power system stability. A DC transmission system for connection of the active stall wind farms to the grid can provide these features and also maximize the produced power especially at low wind speeds by using variable voltage/frequency for the wind farm. The focus in this paper is in studying the operation for the active stall wind farms using a voltage source converter based DC transmission system as well as the power quality issues of the generated power.

	Medium Voltage Converter for Permanent Magnet Wind Power Generators up to 5 MW By FAULSTICH Alexander; STEINKE JueRgen K; WITTWER Fritz	[View] [Download]
Abstract: Wind turbines equipped with a permanent magnet excited synchronous generator have to be connected to the utility grid via a full-scale converter. Medium voltage technology tends to be more suitable for high power systems. The flexibility of full-scale converter-based systems allows easy adaptation to different grid requirements. In recent years the continuously increasing number of wind energy plants brought into operation forced the transmission system operators (TSO) to tighten their grid connection rules in order to limit the effects on network quality. These new rules demand that wind energy plants and farms support the electricity network throughout their operation.