After 10 years GE goes back to DFIGs

UK: GE Energy is to return to doubly fed induction generators (DFIG's) 10 years after ditching the technology for permanent magnet generators (PMGs).

GE will introduce the DFIG generator into its 2.5MW turbine

GE executive product manager Vincent Schellings explained why, ten years ago, GE chose for permanent magnet generators (PMG’s) for the new 2.X-series.

This decision was based upon the expectation that DFIG’s used in the 1.5MW series would be unable to meet future grid (connection) codes.

Another consideration was that PMGs have a reduced mass, while the design enables one generator model for 50Hz and 60Hz wind markets.

However, Schellings said: "This assumption proved wrong. First, DFIG-technology is more cost-effective compared to PMG due to the fact that it only requires a partial converter with 20-35% rated capacity.

"Second, substantial progress has been made with DFIG-technology during the past decade and has continuously proven capable in meeting the latest grid codes. A third benefit is that DFIG electrical conversion losses proved substantially less compared to PMG.

"For our 2.75MW model this loss saving amounts to about 70kW offering a better power curve and enabling a slight generator power increment to 2.85MW."

Schellings added that the new generator type operates at medium-voltage level and will be applied in 2.5-2.85MW model versions.

He concluded that medium-voltage power transport down the tower to the converter and medium-voltage transformer will reduce electrical losses even further, a key overall benefit with increasing tower height.