Comparison of Diode Rectifier and Active-Front-End for Synchronous Generators Suppling DC Loads for Maritime Applications

DC propulsion systems are a trend for Offshore Mobile Platforms (OMPs), such as offshore supply vessels, drilling rigs, and floating production storage and offloading units due to their merits of low emission, high efficiency, and high reliability. Rectifier are used to convert AC voltages from synchronous generators to DC voltage for the DC propulsion systems. The paper presents two rectifier solutions: diode rectifier and Active-Front-End (AFE). In maritime applications, both the two rectifiers are used in different configurations in variety of the OMPs due to their merits: diode rectifier has simple construction and AFE is easy to integration with rest of the power system. Comparison of the two rectifiers is done for their topologies, implementation details, short-circuit issues, harmonics to the generators, and stabilities issues, etc. Simulation results from a 1.8 MVA rectifier are presented. From the comparison, the paper concludes that the diode rectifier is suitable for the synchronous generators that were designed for supplying diode rectifier load; the AFE has faster dynamic response in voltage control and protection of short circuit current and is suitable most types synchronous generators of the OMPs. This paper provides a technical base for electrical engineers for developing electric propulsion systems for vessels.