An Open-Water Efficiency based Speed Change Strategy with Propeller Lifespan Enhancement in All-Electric Ships

In recent years, utilizing the electrical propulsion system in the marine industry has become widely popular. Control of the propeller has been a high-priority design challenge in this industry. One of the essential issues in propeller control is the speed control of the ships. A suitable control strategy for the propeller should be economically-efficient while ensuring stability, reliability, and power quality of the ship's power system. This article proposes an improved propeller control strategy for increasing/decreasing the ship's speed. This scheme consists of two strategies: a maximum acceleration strategy and an efficient operation strategy. The maximum acceleration strategy aims to quickly reach the final speed setpoint. On the other hand, the efficient operation strategy is deemed to increase the reliability and power quality of the ship power system, as well as having a slightly more acceleration than the conventional method. Moreover, a mechanical index is employed for comparing the performance of the various speed change strategies. By utilizing this index, which is known as loss of life (LoL), the effects of a speed change maneuver on the propeller shaft fatigue are analyzed and the advantage of the proposed method in enhancing the propeller lifespan is discussed. Simulations show that utilizing the proposed speed change scheme decreases the propeller mechanical wear and tear to about 1.8 percent of the conventional methods and consequently will increase its lifespan.