The invention relates to a wind energy system having a rotor that can be driven by the wind, preferably having one or more rotor blades that can be adjusted in angle, a generator directly or indirectly connected with the rotor, to generate electric energy, which is configured as an asynchronous generator having a super-synchronous converter cascade in the rotor circuit, for slip-variable generator operation, so that power output of the generator is possible at variable speeds of rotation of the rotor, and an operation guide system that is configured to regulate the speed of rotation of the rotor, within a predetermined wind speed range. To improve the energy yield, it is provided that the super-synchronous rectifier cascade is configured in the rotor circuit for feeding the slip power into the network. For this purpose, the super-synchronous converter cascade has a DC voltage intermediate circuit having a high-set element. These are configured to switch, as IGBT switches, with a 180 degree phase shift relative to the rotor voltage.Furthermore, the invention relates to a method for regulating the power output of the wind energy system, in that the slip is regulated, whereby the slip power is fed into the network.