Performance Analysis of Variable-Speed Diesel Generators in Naval Hybrid DC Power Supply Architectures

Abstract

This thesis explores the potential of Variable Speed Generators (VSGs) within hybrid DC power systems for next-generation Anti-Submarine Warfare (ASW) frigates. As naval operations increasingly prioritise efficiency, emissions reduction, and adaptability to transient load variations, VSGs present a compelling alternative to conventional fixed-speed AC generators. While VSGs offer notable improvements in fuel efficiency, their transient performance under dynamic operating conditions remains a critical area of investigation. To assess these dynamics, a mean value simulation model was used and validated against Factory Acceptance Test (FAT) data and naval standards. The findings reveal a fundamental trade-off: although VSGs enhance fuel efficiency in steady-state operations, their transient response presents challenges, particularly in thermal management and stability. Slow turbocharger dynamics lead to prolonged inadequate air excess ratios during load transitions, resulting in incomplete combustion, excessive soot formation, and increased thermal stress. Additionally, VSGs exhibit difficulties in managing speed and voltage fluctuations during abrupt load changes. Despite these challenges, the study identifies several potential solutions, including electrically assisted turbochargers, advanced energy storage systems, and hybrid control strategies. These innovations can mitigate transient inefficiencies, enhancing both stability and responsiveness. In conclusion, while VSGs represent a significant advancement in naval power systems by combining fuel efficiency with operational flexibility, their successful integration requires targeted improvements in dynamic performance and system-level optimization. By addressing these limitations, VSGs can evolve into a more resilient and robust power solution for next-generation naval vessels.