# Parametric Analysis of Control Techniques for 15 MW Semi-Submersible Floating Wind Turbine
## 6 Conclusions  
In this study, the composite control algorithm based on the classical control methods was proposed to achieve all control objectives for the target FOWT, including the power production, and the loads and motion reductions. The control performance was verified following the approach outlined below:  
1. To meet these control objectives, the feedforward, IPC, peak shaving, and nacelle feedback control algorithms were incorporated into the detuned baseline controller. 2. The parametric simulations using the wind turbine simulation tool OpenFAST were conducted to analyze the performance changes with control parameters and determine the optimal parameters. The parametric simulations were performed under the NTM and NSS conditions, using four levels of control parameter cases for each control technique. Control performance indicators, including the mean power, the standard deviation of the rotor speed, platform motion, and the tower and the blade loads, were compared. The results showed that, while increasing the control parameters improved control performance, excessively high values led to degradation in aspects unrelated to the primary control objectives. Consequently, the control parameters for each control technique were selected to avoid adversely affecting other performance indicators. 3. To verify the performance of the overall control algorithm with the selected control parameters from the parametric study, simulations under DLC 1.2 and DLC 1.6 were carried out. The results demonstrated that the proposed control algorithm achieved significant load and motion reductions compared with the ROSCO controller. Specifically, while the mean power was decreased by 5%, the rotor speed deviation  
Figure 16: The power curtailment simulation results of the target FOWT: (**a**) under steady-state conditions; (**b**) under turbulence conditions. The black solid line represents the wind speed and wave elevation inputs used in the simulation. was reduced by 49%, platform pitch motion by 20%, tower loads by 15%, blade loads by 17%, RNA acceleration by 22%, and the mooring line tension by 38%. 4. In addition to the power production and the load and motion reductions, the DPPT control algorithm was implemented to consider the additional control objective. The simulation results under power curtailment showed that the difference between the demanded power command and the produced power was within 1%. In this study, the control performance of the proposed control algorithm was verified solely through dynamic simulations. Therefore, future research will focus on experimentally validating the performance of the proposed control algorithm. The proposed control algorithm is based on C source code, which allows the proposed algorithm to be uploaded to commercial PLCs in source code form, enabling its direct application in PLC-based experiments. The PLC, with the proposed control algorithm uploaded, can be connected to the scaled model of the FOWT and used for wind tunnel tests or water tank experiments [34,35]. Alternatively, a hardware-in-the-loop simulator (HILS) study, integrating the commercial PLC with the numerical model in the simulation, could also be considered [28]. Although experimental validation was not conducted in this study, it is expected to contribute to the industry as a foundational study for the future experimental validation of the proposed control algorithm. Conceptualization, T.J.; methodology, T.J.; software, T.J. and J.K.; supervision, I.P. ; project administration, C.-H.L. and B.-S.K. ; validation, T.J.; resources, C.-H.L. and B.-S.K. ; writing--original draft preparation, T.J.; writing--review and editing, I.P. All authors have read and agreed to the published version of the manuscript. This research was supported by the Korea Research Institute of Ships and Ocean Engineering, a grant from the Endowment Project \"Development of Core Technology for Offshore Green Hydrogen to Realize a Carbon-Neutral Society\" funded by the Ministry of Oceans and Fisheries (PES5171). Not applicable.