A Review on the Research of Marine Electric Propulsion Systems

Marine electric propulsion system is a core technology at the intersection of shipping low-carbonization, ship intellectualization and comprehensive electrification. Compared with traditional mechanical propulsion, electric propulsion is not a simple replacement of diesel engines with electric motors. Instead, it takes generator sets, energy storage devices, fuel cells, shore power interfaces, ship power grids, power electronic converters, propulsion motors, propellers/podded thrusters and energy management systems as the core, forming a ship integrated energy system with multi-energy sources, multi-loads and multiple constraints. Its main advantages include flexible layout, improved efficiency under low load, enhanced redundancy and maneuverability, and easy access to new energy sources such as batteries and fuel cells. Meanwhile, it still faces challenges including low battery energy density, thermal runaway risks, poor reliability of power electronic devices, electromagnetic compatibility issues, insufficient port energy supply infrastructure and difficulties in full-life-cycle carbon emission accounting. This paper reviews the research background, significance, system architecture, key equipment, energy management strategies, typical applications, safety specifications, technical bottlenecks and development trends of marine electric propulsion systems, and conducts comparative analysis on various circuit topologies and application scenarios based on published literature. The review indicates that in the coming period, pure electric and battery hybrid propulsion will be preferentially applied to coastal short-distance vessels, inland waterway ships, harbor tugs, ferries and engineering working ships. In contrast, ocean-going merchant ships will mostly adopt a progressive electrification route combining low/zero-carbon fuel main engines, shaft power generation, energy storage peak shaving, shore power connection and digital energy management.