Abstract
This paper presents a mechanistic approach to stability analysis in onboard hybrid power systems with high penetration of power electronic converters (PECs). Motivated by operational experience from state-of-the-art hybrid vessels, the study investigates how inverter penetration level (IPL), converter control tuning, and the relative sizing of synchronous generators influence system dynamics. Using a combination of detailed modeling and field measurements, the analysis demonstrates how increased IPL reduces system robustness and heightens sensitivity to alternating-current controller (ACC) and phaselocked loop (PLL) tuning, particularly in weak-grid conditions associated with smaller generators. The results indicate that increasing ACC gains can improve stability, but practical limits arise from hardware constraints and the risk of controlinduced resonances. Furthermore, it is shown that generator design parameters-particularly field winding inductance and d-axis transient reactance-significantly shape stability margins and, when designed appropriately, can mitigate adverse interactions in high-IPL configurations. However, this introduces trade-offs, including altered excitation dynamics and potential impacts on fault response. The findings highlight the importance of coordinated design between converter control settings and generator electrical characteristics to ensure reliable operation across diverse marine power system configurations. The work provides practical guidance for engineers and designers seeking to optimize the performance, reliability, and resilience of nextgeneration marine hybrid power systems.