Modeling In-and-Out-of-Water Impact on All-Electric Ship Power System Considering Propeller Submergence in Waves

Abstract

Despite the advantages of employing an electric propulsion system in All-Electric Ships (AES), additional power fluctuation sources have emerged in the ship power system as a result. Since the propellers are the primary power consumers in the AES, these fluctuations may significantly affect its power system power quality. Thus, for optimal performance of the ship power system, these fluctuations need to be rigorously investigated at the design level of vessels. Waves collision is one of the critical conditions where propellers inject power fluctuations into the ship power system. Therefore, a comprehensive model is essential to analyze the propellers in-and-out-of-water effect on the ship power system thoroughly at the design level. This paper proposes a model-based approach for determining propeller immersion depth variations in collisions with different wave classes. According to this approach, the propellers thrust loss factor caused by the in-and-out-of-water effect can be identified. The proposed method is then applied in an integrated AES model. This model interconnects the ship motion and power system dynamics. The in-and-out-of-water impact on the ship power system can be explored precisely in the model-based design of the vessels by utilizing the proposed model. In the end, the proposed method and the interconnected model have been used to simulate a notional ship in a wave collision condition. Simulations demonstrate that the proposed approach can accurately map the substantial impacts of the vessel-wave encountering conditions on the frequency, voltage, and generally on the power quality of the AES power system.