This study aims at proposing a simulation method for an offshore converter station platform (OCS) under dynamic loading. A user-defined in-house FORTRAN code was developed based on the Vector Form Intrinsic Finite Element (VFIFE) method, and the numerical model was validated by test data. After model validation, the dynamic behavior of the OCS was carefully studied and the effect of different loading conditions, including seismic, hydrodynamic and wind load, on the dynamic behavior of OCS was investigated. The time history of the structural response was obtained, and the relationship between the structural peak response and the peak value of the seismic load was also shown. It indicated that water damping accelerates energy consumption, while the effect of hydrodynamic and wind load has little influence on the cases studied in this work. Generally, the peak response increases almost linearly with the increase in the peak acceleration of the ground, and the seismic propagating direction has a great impact. In addition, both a whipping effect and stretching-squeezing effect were observed, and the vertical acceleration response of the valve hall deck is much higher than other structures, which is caused by the relatively lower local rigidity of the large-span structure and the inertia force caused by the valve tower.

Converter valves are the core equipment of offshore wind power structures. However, they are highly vulnerable to vibration under strong earthquakes, which will affect normal operation of the offshore wind farm. Converter station is an axisymmetric structure with obvious asymmetry in its internal configuration of the superstructure. This study aimed to analyze the dynamic response of a supported converter valve in an offshore converter station under seismic excitation. The coupling model of the supported valve tower group and the converter station were established, and the distribution law of the valve tower dynamic response and foundation settlement were investigated. The dynamic response effect of the modal truncation, valve tower stiffness, and basic size on different areas and foundations of the valve towers were studied. The findings were as follows: (i) the effect of local vibration of the valve tower should not be simplified by using equivalent mass and node condensation; (ii) the structure–equipment coupling analysis method should be used to review the structural design scheme of the offshore converter station in the intensity VII region; (iii) the vertical higher-order modes should be considered during the vibration response calculation and its participation ratio in mass should not be lower than 90%; (iv) the frequency range that minimizes the vibration response is the characteristic frequency range of horizontal vibration, while the best vibration suppression effect cannot be obtained in both the horizontal and vertical directions; and (v) the stiffness of the valve tower itself should be adjusted and different stiffness designs of the valve tower in different positions should be adopted to realize effective vibration response control.

As offshore wind power moves into deeper waters, large-scale electrical platforms are key to efficient power transmission. However, their heavy topside modules create major installation challenges. As traditional lifting methods are inadequate, the float-over method has become a viable solution for installing topside modules, but it is essential to study the structural responses to collisions during the process to ensure construction and equipment safety. This study establishes a physical model of the offshore converter station at a 1:65 scale based on the elastic force-gravity similarity principle. Assuming the barge carrying the topside module descends at a constant speed, the study investigates the dynamic response of the platform during the float-over mating process. Float-over collision tests are conducted to obtain the platform’s acceleration, strain, and displacement responses and to analyze the effects of collision speed, offset position, and Leg Mating Unit (LMU) stiffness on the dynamic structural response characteristics. The results show that as collision speed increases from 10 mm/s to 50 mm/s, the topside acceleration response increases up to 5.7 times. Beam strain remains mostly unchanged, and displacement increases first, then decreases. Under fixed descent velocity, x-offset increases jacket strain and converter valve acceleration, while y-offset raises platform acceleration and reduces valve acceleration by approximately 20 percent. At 50 mm/s, higher LMU stiffness causes the acceleration response to first drop, then rise. These findings support safe float-over installation.

The foundation structure of offshore substation platforms is complex and has numerous degrees of freedom. The computational efficiency of dynamic response analysis using traditional time-domain methods is often relatively low. To facilitate the dynamic response analysis of offshore substation platform foundation structures with large degrees of freedom (DOFs), this paper proposes a method for dynamic response analysis based on modal truncation, which involves conducting a modal analysis and decoupling the vibration system matrix based on the modal shapes. Additionally, it analyzes the external load spectrum and determines the modal-truncation range through the transfer relationship between the external load frequency and the modal response. This approach reduces the size of the dynamic response analysis matrix, thereby significantly improving the computational efficiency of the dynamic response analysis of large-DOF offshore substation platform foundations. A six-DOF mass-damping-spring system and a finite element model of an offshore substation platform foundation were used to test the proposed method. The proposed method reduces the number of decoupled equations used to analyze the offshore substation platform foundation from 312 to 9. It was compared with the Newmark-β method, and the results show that the proposed method aligns well with the Newmark-β method in terms of calculation results, with computational efficiency improved by approximately 100 times.

With the development of offshore wind power towards deep-sea areas, the offshore valve tower, as a key facility of offshore wind farms, plays a vital role in ensuring the stable operation of the system. To investigate its dynamic response characteristics under seismic loading, a 1:25 physical test model of the valve tower was constructed based on the gravity–elasticity similarity principle. Acceleration responses at the first deck of a 1:65 scale offshore converter platform model were obtained through shaking-table tests and applied as base excitation to the valve tower model. The experimental results reveal that the frequency domain response of the valve tower transitions from high-frequency dominance at the base to low-frequency dominance at the top, with the structural weak link located at the mid-connection between the front and rear sub-towers. The fundamental frequency of the valve tower is 3.92 Hz, and the average damping ratio is 3.21%. The shake table test of the converter valve tower was verified using the gravity–elasticity similarity law, effectively reproducing the seismic response characteristics of the prototype. This provides crucial data for seismic response spectrum analysis, identifies structural weaknesses, and offers guidance for the design of more earthquake-resistant offshore valve towers, thus enhancing the safety of deep-sea wind farms.