As a special energy system, the optimization of maritime grids can be considered as three levels similar to conventional land-based energy systems [1][2][3].(1) Synthesis optimization. Synthesis is defined as the components used in the maritime grids and their connections. Via synthesis optimization, the optimal configuration of the maritime grids can be determined. For example, the ship hull design, electrical layout, and whether to integrate a component or not. Since the synthesis optimization answers the "Yes-or-No" questions and therefore involves certain binary decision variables.(2) Design optimization or planning optimization. Design optimization is to determine the technical characteristics of components which are determined in synthesis optimization, such as the capacity and rated power. The difference between synthesis optimization and design optimization can be given by the well-known "siting and sizing" problems. The "siting problem" determines which type of components can be used and where to install them, which belongs to the synthesis optimization. Then the "sizing problem" determines the capacities of the installed components, which belongs to the design optimization.In power system research, design optimization is often named as planning optimization.(3) Operation optimization. After the synthesis optimization and design optimization, the operation optimization determines the optimal operating states of each component under specified conditions. Taken the navigation speed as an example. The synthesis optimization determines the type of main engine and the design optimization determines the capacity of the main engine, then operation optimization determines the optimal loading levels to address different navigation scenarios, such as different wave and wind scenarios.