Electric Ship Research Research Articles

Energy management strategy of marine lithium batteries based on cyclic life

In recent years, pure electric ship research has become a hot spot in the field of ship research, and lithium battery packs are a major difficulty in the research of pure power ships. Especially the life and safety problems of lithium battery packs seriously affect the future practical application of ships. Therefore, the energy storage system is designed as two sets of lithium battery packs. While increasing the energy of the energy storage system, the power supply of the battery pack is ensured, which not only ensures the safety of the pure electric ship, but also reduces the aging reaction rate of the lithium battery pack. Through the multi-energy ship modeling, specifically related to the control and safe operation of lithium battery packs, a lithium battery pack energy management strategy is provided. The specific scheme is: the model of ship sailing mileage and SOC is established by the theory of energy conservation, the lithium battery aging model is obtained by the lithium battery data of the actual pure electric ship navigation, and the lithium battery pack energy switching based on the mileage aging battery model is proposed. The strategy uses a logic threshold optimization algorithm to reduce the aging rate of the lithium battery pack. Finally, the experimental results show that the lithium battery pack with energy management strategy can perform 400 more navigations when the capacity loss reaches 15% in the same environment. It shows that this strategy is beneficial to improve the cycle life of lithium battery packs.

The experimental validation of a transient power electronic building block (PEBB) mathematical model

This work adjusts and validates experimentally a previously developed volume element model based thermal management tool (vemESRDC) through the comparison of temperature measurements of a power electronic building block (PEBB) to numerical simulation results, featuring relevant electronic components of an all-electric ship. Primary components of interest in this simulation are: inductors, capacitors, AC and DC fuses, and a tiristors/fins set. The vemESRDC is a thermal simulation tool developed as part of the Electric Ship Research and Development Consortium (ESRDC) funded by the Office of Naval Research (ONR) that is capable of providing quick responses during early stages of ship design. The model adjustment was conducted by solving the inverse problem of parameter estimation for appropriate equipment properties using a total power dissipation of 4.8 kW in the PEBB. Next, the adjusted model was experimentally validated using the same PEBB with a power dissipation of 11.12 kW. The transient and steady state numerical results are shown to be in good quantitative and qualitative agreement with the experimental measurements within the experimental error margin. Transient simulations demonstrate that the components temperature vary significantly from one heating mode to another, whereas internal air average temperature varies only slightly for all heating modes, therefore not only average internal air temperature should be monitored for preserving equipment functionality. As a result, it is expected that vemESRDC could be used as a reliable tool for transient and steady state thermal management of heat generating packages (e.g., PEBB, future all-electric ship).