DC Grids for Ship Propulsion: Benefits and Challenges

While the application of lithium-ion batteries to propulsion has dominated the marine industry’s attention, another equally important shift is occurring. The standard alternating-current (AC) backbone of a diesel-electric is being replaced with direct current (DC). AC generators and motors remain but are connected through converters. This architecture is often referred to as a DC grid. They offer advantages such as reducing volume, weight and electrical harmonics while making it easier to interconnect DC sources like batteries, supercapacitors and fuel cells. Their biggest disadvantage is developing higher fault currents in a shorter amount of time than a comparable AC network. This has required unique protection schemes and led to a challenge for existing regulatory norms.