During single-blade offshore wind turbine (OWT) installation, wind disturbance results in blade root motion. The sensitivity to this wind disturbance is more significant for larger blades, reducing the allowable installation weather limit. A potential solution is a Hook Mounted Compensator (HMC) between the crane and the load that can provide high-precision compensation across multiple degree of freedom (DOF), and compensate for the influence of wind on the OWT blade. Several Actuation Method (AM)s have been identified that can be used in a HMC. However, these AMs have not been modelled dynamically and their effectiveness for the desired application is unknown. The aim of this study is to analyse and assess the compensation effectiveness of these AMs in a HMC. For this purpose, the AMs are simulated and analysed in various levels of complexity and DOFs. Initially, the system is considered in a 1DOF. A linear representation is formulated, based on which a Proportional-Integral-Derivative (PID) controller for each AM is formulated. This enables simulation of the Single-Blade Installation System (SBIS) in the time domain. Assessment criteria are used to quantify the compensation effectiveness and actuation input of the AMs. To simulate the SBIS for each AM, 3DOF numerical models are developed that describe the operation of the AMs in their respective operational planes. Six actuation methods are included in the assessment. Based on the assessment results, three AMs are combined in a HMC concept. A XY table is used to control blade root position in the x- and y-directions, gyroscopes for the z-direction, and COG shifting with counterweight to prevent gyroscope saturation. The PID controllers based on the linear 1DOF representation are used, operating in parallel, to control the blade root position in all DOF. The blade root motion is reduced by 96% along the blade axis and 86% radially. The blade root motion is sensitive to the mean wind speed, turbulence intensity, and angle of the incoming wind. The HMC shows robustness to variations in tugger line angle and pretension. The static blade pitch angle affects the magnitude and distribution of the wind-induced moment on the blade. For a pitch angle of -180, the moment around the z-axis is minimal, providing optimal HMC performance. The HMC concept can not directly actuate the blade around the z-axis. Instead, the XY table translates the blade at the COG, resulting in increased cylinder stroke and high power consumption for other pitch angles. Two AMs were assessed to actuate the blade around the z-axis, both showing poor performance. Further exploration of AMS that can directly control the blade rotation around the z-axis could lead to improvement of the HMC concept. Additional improvement can be made in optimization of counterweight and gyroscopes sizes, potentially reducing weight and improving system performance. Further suggestions for future work include; exploring the compensating for the now neglected hub motion using the HMC, examining the stability of the HMC once the blade is mated to the hub, and the impact of sensor noise and delay on the HMC’s performance.

Huisman has introduced the Windfarm Installation Vessel as a complete solution to assemble and install offshore wind turbines at sea. Installing a floating wind turbine at sea brings two main challenges, the relative motions between the floating structures and the load transfer of the wind turbine. The proposed installation procedure considers a connection between the installation vessel and a semi-submersible floating support structure to reduce the relative motions and facilitate the load transfer. This research investigates how the connection's structural configuration affects the system's relative motions and loads during five defined installation stages. The different installation stages cover varying amounts of ballast transfer, as well as the mating phase of the wind turbine. A two-dimensional multi-body model has been formulated considering a rigid link between the installation vessel and the floating support structure. The hydrodynamics of the floating structures and the regular wave loads on the structures are calculated using Ansys AQWA. A system analysis is performed to investigate the effect of adding stiffness in one or combined directions of motion of the connection. The change in dynamic effects during the installation stages are minimal, the ballast transfer mainly changes the static load on the connection. Overall, it can be concluded that a combination of stiffness in the different connection directions will provide the most favourable results. To limit the relative heave motions, coupled surge or pitch and heave stiffness is required. A different stiffness on both sides of the connection is also shown to improve the system’s behaviour. Fixing the rotation of the connection on one side improves the relative pitch motions between the wind turbine and the support structure. More research is required to investigate favourable combinations of limiting motions on each side of the connection. The presented model could be used for a future optimization study to find optimal stiffness values for the connection.