Long-span structure is one of the typical structure features of ships. Low rigidity of the long-span structure causes large structure displacement and vibration amplitude, imposing difficulties in the vibration reduction design. The vibration of the long-span grillage structure is analyzed for a ship under bow thruster excitation in the current study. Topology optimization base structure is then established for the arrangement of the pillar under the long-span grillage structure. With the objective function of lightest structure weight based on SIMP method, the dynamic topology optimization design is carried out by using the stand pillar arrangement topology optimization model considering the vibration velocities of specified nodes as the constrain. The results show that a pillar arrangement plan with good vibration control performance is obtained by using the long-span pillar topology optimization method in the current study. This method can reduce the complexity of the design and the workload of the dynamic calculation, with a better vibration damping effect.

The frequent operation of the high-power pulse load equipment will affect the voltage and frequency of the power grid for the ships equipped with the high-power pulse load equipment. Based on the power station configuration of the power system of the full-scale ship, it analyzes the power supply programme according to the operation conditions of the high-power pulse load equipment, and proposes the corresponding load characteristic programme for the high-power pulse load. It also summarizes the relevant technical data of the generator sets, high-power pulse load equipment and electric propulsion equipment. The theoretical analysis and simulation of the key indicators, such as voltage, frequency and harmonic content of the power grid with the application of high-power pulse load, are carried out according to the actual operation conditions. Corresponding solutions are then proposed to ensure the normal operation of all the electrical equipment in the power grid.

The development of new energy has attracted the attention of all countries in the world. The grid-tied inverters connect the new energy resources and the power grid. LCL filter is used to suppress PWM harmonics caused by the inverter pulse width modulation. The zero impedance characteristics of LCL filter at the resonant frequency will cause the system resonance which endangers the stability of the system. Firstly, the paper analyzes the variation of the equivalent impedance of the ship multi-inverter parallel system, which drifts the LCL filter resonant frequency. Secondly, a harmonic suppression strategy for the shipboard grid-connected inverters is proposed, which can ensure the stability and effectiveness of the harmonic suppression of the single-phase LCL-filter-based grid-tied inverters system. At last, simulations based on PSIM 9.0 have been presented to verify the effectiveness of the proposed method.