DC side current and torque ripples reduction in multi-modular PMSG for wind applications

High power Permanent Magnet Synchronous Generators for wind applications may be made of modular subsystems, connected to the same shaft. The paper mathematically analyses the DC-side current and the torque ripples of a particular configuration: the stator phase axes of the several modules are axially aligned while the rotors are reciprocally shifted by a suited angle. Moreover each module is connected to a two-level AC-DC converter; such converters are paralleled on the DC-side. For now, just square wave rectifier operation has been considered: the necessary phase shift of the voltages among the converters is found out in order to reduce the ripple of the resultant DC-side current and of the total torque. Such a phase shift coincides with that among the rotors. Some calculations are checked through a simulation, proving the effectiveness of the proposal.