Power Management Strategies Based on Propellers Speed Control in Waves for Mitigating Power Fluctuations of Ships

This article proposes two novel power management strategies (PMSs) to enhance the electrical power quality in twin-screw all-electric ships (AESs) during vessel-wave encountering. Soothing PMS (SPMS) focuses on mitigating power fluctuations of the propulsion system since it has significant impacts on the power system in extreme conditions. For this purpose, the PMS modifies propellers’ speed based on the in-and-out-of-water effect loss factor (LF) in wave collisions. This method does not require typical equipment, such as energy storage systems (ESSs), to moderate the variations. Hence, it decreases the ESS demand capacity and maintenance costs at the design and operation levels. An integrated ship model is introduced to determine this LF in waves thoroughly. Furthermore, due to the propeller dynamics in speed altering, an adaptive delay is embedded in SPMS to improve its efficiency, and an advanced SPMS (ASPMS) is developed. To determine this varying adaptive delay during an operation, a straightforward algorithm is proposed, which does not impose the PMS to compute complex differential equations. Simulations reveal that both PMSs soothe the propulsion system power fluctuations and remarkably reduce the power system frequency and voltage variations. Meanwhile, the ASPMS surpasses the SPMS in terms of improving the power quality.