Propulsion and Battery Charging Systems of an All-Electric Boat Fully Constructed with Interleaved Converters Employing Interphase Transformers and Gallium Nitride (GaN) Power FET Semiconductors Thiago B. Soeiro ABB Switzerland Ltd Corporate Research Power Electronics Group CH 5405, Baden-Daettwil, Switzerland E-mail: thiago-batista.soeiro@ch.abb.com Tiago K. Jappe, Walbermark M. dos Santos, Denizar C. Martins, and Marcelo L. Heldwein Federal University of Santa Catarina (UFSC) Electronics and Electrical Engineering Department Florian´ opolis, SC, Brazil E-mail: {tiagokj, walbermark, heldwein}@inep.ufsc.br Abstract—This work presents a Power Electronics solution for an all-electric passenger boat. The proposed system is constructed with building blocks comprising interleaved half-bridge convert- ers employing interphase transformer and Gallium Nitride FET semiconductors. The system employs two multi-level drives and an integrated harbor and onboard PV system. The PV battery charger has two stages. One converter per PV panel and a second based on cascaded buck-boost converters that control the battery current and adapts the voltage levels. The operation, control and design expressions are presented. Finally, experimental results verify the feasibility of the proposed system. I. I NTRODUCTION Among the various environmental problems faced today, water pollution caused by navigation in sheltered waters such as lakes and lagoons are a concern, not only in tourist areas where the traffic increases every year, but also in environmentally protected areas. Initiatives to use electric propulsion systems in transportation represent alternatives to reduce the environment pollution and improve overall life quality standards, among other benefits [1], [2]. This work presents a complete Power Electronics solution for small all- electric boats using low voltage battery packs (96 V for the system at hand). The proposal is to develop a zero emission boat for public transportation in sheltered waters, which it will be deployed in well-defined routes and low speeds, typically under 10 knots. Fig. 1 presents the sketch and the schematic diagram of the proposed all-electric boat, which is driven by two 3- kW permanent magnet synchronous motors (PMSM) powered from lithium-ion batteries. The battery bank composes 30 cells of Lithium Iron Phosphate (LiFePO 4 ) providing enough energy for approximately 4 hours at the maximum power of 6kW. In order to increase the system cruise range 14 m 2 of photovoltaic (PV) panels providing up to 32% of the rated power is installed on the roof of the boat. The batteries are also recharged through a dedicated charging station located on the harbor or docks while the boat is moored. This is grid- connected, and can also be connected to a local PV array. For the power converters of the propulsion and battery charging systems, wide bandgap semiconductors, such as gal- a) b) Fig. 1. a) Sketch and b) schematic diagram of the all-electric passenger boat.