## 5 Conclusions  
This paper uses a 5 MW-OC4 semi-submersible floating wind turbine as the research object to compare and analyze the optimization results of the overall response of the floating wind turbine when the accessories are used alone and in combination, and draws a link between the mooring accessories and the overall response of the floating wind turbine, which provides a reference and reference for the design of mooring systems in small water depth in the Bohai Sea in the future. From the above analysis and discussion, several important conclusions can be drawn, as follows. 1. At small water depths, when the span between catenary and tensioned moorings is the same, the catenary mooring is better than the tensioned mooring in terms of droop and longitudinal rocking motion response and tension. In the aspect of surge, the positioning ability of the tensioned mooring is better than that of the catenary type, and the motion control ability is worse than that of the catenary type. Considering the advantages and disadvantages of both and the safe operation ability of floating wind turbines in complex marine environments, catenary mooring is a more suitable mooring mode. 2. After the buoy and clump weight are added to the floating wind turbine mooring system, the surge and pitch motion responses can be obviously optimized, and the maximum of the mooring tension can be reduced, but the heave motion response is slightly increased due to the characteristics of the clump weight and buoy. 3. When mooring accessories are used alone, increasing the volume of the buoy will increase the maximum value and average value of surge, heave and pitch, and the maximum value of tension will also increase; When the installation position of the buoy moves down within a certain range, the maximum and mean values of the pitch and pitch will increase, but the maximum and mean values of the heave will decrease, and the mooring line tension will also increase. The increase in the mass of the clump weight will reduce the maximum value and the mean value of the heave and pitch, the maximum value of the heave will increase but the average value will decrease, while the maximum value of the mooring line tension will decrease, and the amplitude of the oscillation will also decrease. If the installation position of the clump weight is moved backward within a certain range, the maximum value and average value of surge and pitch will increase, the maximum value of heave will decrease but the average value will increase, and the maximum value of tension and the amplitude of oscillation will increase. 4. The combination of the use of accessories to change the parameters of the overall response of the floating wind turbine the same law as the use of accessories alone when changing the same parameters. However, the rate of improvement of the mooring system optimization by changing the mooring parameters when used in combination is higher than the result of changing the same parameters when the accessories are used alone; The optimization difference of the maximum heave motion response can reach 24.6%, and the optimization difference of the mean value can reach 30.1%. The surge, pitch and tension difference are basically within 10%. 5. When changing the mass parameters of the clump weight, the maximum difference of the heave, pitch and tension response of the fan is 1.837% and the minimum is only 0.006% under the condition of the single and combined use of the accessories, which is much smaller than the optimization difference caused by changing other parameters. This shows that when changing the mass parameters of the clump weight, whether it is used in combination with the buoy has little effect on the overall response. So it is not difficult to see that the clump weight mass parameters have a greater impact on the mooring system than other parameters.