Protecting Wind Generators During Voltage Dips
Wind turbines experience problem due to sudden drop in voltage in a portion of the electric grid. Industrial engineer and member of INGEPER Research Team at the Public University of Navarre, Jesús López Taberna is trying to tackle this problem. His team has come out with a rotor model which predicts how the wind power units will behave under these circumstances. Mr López has already patented two techniques and one of which is already with a manufacturer who will utilize it internationally. They have designed generator turbines in such a way that when voltage dips occur, generators continue to function uninterrupted.
In his PhD, Jesús López Taberna presented two protection techniques so that wind generators continue to be operative despite breaks in electricity supply. The title of the PhD is: “The Behaviour Of Wind-Powered Generators With Double-Fed Asynchronous Motor During Voltage Dips”.
Over the past few years wind energy converters were not performing optimally. The most important difficulty is how wind generators will behave during voltage dips. A voltage drip is an unexpected cutback in the potential in the electric grid followed by a rapid return to its normal value. Voltage drips can be caused by lightening, falling of trees on power cables or any commercial unit consuming a huge power chunk suddenly. This voltage drop lasts for a few milliseconds. But these few milliseconds are very crucial for a machine. In fact, an interruption of half a second in a productive process can cause the whole process to block and it may have to be reinitiated.
Voltage drops can destroy the electronic part of the unit or it can get burnt, hence the need for a protection system. Currently wind generators have a “Crowbar” protection system which can protect the machine but its biggest disadvantage is that the machine comes to a halt. If a large commercial unit suddenly devours a lot of power the voltage dips and wind power units get disconnected and stop producing electricity. This situation makes it difficult for the voltage to reach its normal level. If problem persists for a day or two then one can imagine the seriousness of the problem. The research team is working to make the air generator behave as a conventional power station. A conventional station doesn’t disconnect during power failure but helps in getting grid voltage back up.
The research team is trying to find out solutions that enhance the behavior of the machine without any need to change anything except the control. Analogy can be drawn from a digitally generated text document. A new software version is introduced but you don’t have to change your PC to avail the benefits of the new version.
Jesús López Taberna has specifically proposed two systems of protection in his PhD thesis, and both have been patented. The first, only requiring changing the control of the machine converter, has been transferred to a manufacturer for introduction into wind parks worldwide; the other requires changing elements inside the machine and continues to be developed for applications in new creation wind generators.