We present results on quantitative infrared spectroscopy of the brightest HeI emission line stars in the Galactic center. The observed HeI and H broad emission lines are caused by extremely strong stellar winds (Mdot ~ 5 to 80 * 10^-5 M_sun/yr) with relatively small outflow velocities (v_inf ~ 300 to 1000 km/sec ). The effective temperatures of the objects range from 17,000 K to 30,000 K with corresponding stellar luminosities of 1 to 30 * 10^5 L_sun. Strongly enhanced helium abundances (NHe/NH>.5) are found. These results indicate that the HeI emission line stars are evolved blue supergiants close to the evolutionary stage of Wolf-Rayet stars. They power the central parsec and belong to a young stellar cluster of massive stars which formed a few million years ago.)