Integrated Multiport Conversion with Rotating Transformer
Single-phase energy systems are becoming increasingly common due to the rise of resi-dential scale (∼3kW) renewable energy in the US. Integrating storage, sources, and loads poses many challenges associated with power balancing and being resilient to power supply variations or interruptions. A multi-port hub for integrating a single-phase utility connection, DC battery storage, DC photovoltaic (PV) generation, and critical customer loads is presented in this dissertation. At the core of the system is an electric machine that functions as a multiport rotating transformer, providing voltage conversion, galvanic isolation, 120 Hz ripple energy balancing for single-phase ports, and hold-up energy by use of intrinsic stored kinetic energy in rotation. The energy stored in rotation of the machine is orders of magnitude greater than that available in the capacitor bank often used in static systems and has no associated power versus energy trade-off. A transverse flux topology was chosen for the rotating transformer due to the topology’s true torque scaling with respect to pole pairs and its simple winding configuration. The transverse flux machine was chosen to be have a U-core topology for its relative ease of manufacturing. A convex optimization design method was used to determine the machine physical dimensions and operating speed. The number of stator poles and magnets was specifically chosen to minimize cogging. A prototype system has been constructed that demonstrates all the functionalities of the rotating transformer. The prototype system validates the multiport system with rotating transformer as an effective and cost efficient method for the integration of typical residential PV components. This dissertation covers the design and implementation of the rotating transformer, its mechanical suspension, the system control, and the system power electronic converters.