Design of Wound Rotor Synchronous Machines for DC Power Generation

There is growing interest in the use of DC microgrids to power ships, aircraft, and data centers. Among possible generation system topologies, the wound rotor synchronous machine (WRSM) coupled to a passive rectifier with DC-side filtering is attractive due to its robustness and simplicity. A challenge faced in the design of such systems is that the coupled behavior is dependent on the machine’s subtransient inductances, which are governed by the placement and interconnection of damper conductors in the rotor. Therefore, in order to design and analyze this topology, it is necessary to establish a coupled system-level model that accounts for the damper network design and permits calculation of the system’s subtransient performance. In this research, a system-level model has been derived and structured to enable multiobjective optimization of DC systems of arbitrary power levels. Evaluations of several optimizations have shown that in the integrated design of DC microgrids, the optimized machines often forgo active damper networks. These results point to a conclusion that WRSMs tailored to DC microgrids are distinct from their AC counterparts. It is noted that the computational requirements of the system-level model are significant, which impacts its utility for automated design. To reduce the calculation burden, simplified machine models have been considered for performance characterization. In doing so, it has been observed that traditional qd-models often fail to provide reasonable accuracy, due in part to their inability to capture commutation intervals and in part due to non-idealities in the machines. A procedure is thus set forth to improve the qd-model agreement during the design process. In addition, the tradeoff in restricting the design space to the subset of machines with qd-model agreement is examined. Finally, mechanisms for including transient performance specifications into the optimization procedures are detailed and their effects on the resulting system design are considered