Control of MVDC Bus in Electric Ships Using Multiphase Hybrid Generator

This paper proposes a control strategy for maintaining medium voltage direct current (MVDC) bus voltage in electric ships using a multiphase dual rotor hybrid generator system. The generator, a 9-phase dual rotor machine with permanent magnet (PM) and wound field (WF) rotors, outputs power that is rectified through an uncontrolled passive rectification stage and then connected to an MVDC bus. This bus supplies power to the ship's propulsion system, pulsed loads, and service loads. The dual rotor design facilitates control over voltage variations during load fluctuations as the ship accelerates or decelerates. The controller adjusts the DC field current injected into the WF winding of the hybrid generator based on the load power requirements. This, in turn, regulates the machine's total back-EMF, thereby controlling the rectified DC voltage at the output of the rectifier connected to the MVDC bus. The effectiveness of this generator system and control strategy is confirmed through simulation studies.