Control-oriented semi-submersible floating fan dynamic modeling method

Abstract

A control-oriented semi-submersible floating fan dynamic modeling method comprises the following steps: S1, describing components of a floating fan structure, and defining feature parameters of the components; s2, establishing a coordinate system for describing the dynamics of the floating fan; s3, dynamic description of the components of the floating fan is given; s4, calculating the total energy of the floating fan system; s5, calculating an external load borne by the floating fan system; and S6, based on a Lagrange energy method, providing a kinetic model of the semi-submersible floating fan system. The scheme is used for solving the problems that an existing offshore wind turbine model is complex in structure, cannot achieve balance between model conciseness and accuracy and is not suitable for control system design.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind energy, and particularly to a control-oriented dynamic modeling method for a semi-submersible floating wind turbine. Background Art

[0002] Due to the growing global demand for clean energy supply, wind energy plays an important role in the global energy structure. Currently, offshore wind energy has attracted increasing attention due to its significant advantages over onshore wind energy. The survey results show that the potential of global offshore wind energy can meet the current world's electricity consumption. As the water depth increases, the construction cost of bottom-mounted wind turbines will increase significantly. In view of this, floating wind turbines (FWTs) are considered to be the best solution for developing deep-sea wind energy at present.

[0003] An offshore floating wind turbine is a complex coupled dynamic system that is subjected to the combined action of aerodynamic loads, hydrostatic loads, and mooring loads. This poses great challenges to the dynamic response analysis, safety and fatigue assessment, and vibration control of floating wind turbines. Currently, constructing a control-oriented simplified dynamic model of a floating wind turbine and achieving a balance between the simplicity and accuracy of the model is of great significance for the design of a floating wind turbine controller. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a control-oriented dynamic modeling method for a semi-submersible floating wind turbine, which solves the problems that the existing offshore wind turbine model has a complex structure, cannot achieve a balance between model simplicity and accuracy, and is not suitable for the design of a control system.

[0005] The above technical object of the present invention is achieved through the following technical solutions:

[0006] A control-oriented dynamic modeling method for a semi-submersible floating wind turbine includes the following steps: S1, describing the components of the floating wind turbine structure and defining the characteristic parameters of the components; S2, establishing a coordinate system for describing the dynamics of the floating wind turbine; S3, giving the dynamic description of the components of the floating wind turbine; S4, calculating the total energy of the floating wind turbine system; S5, calculating the external loads received by the floating wind turbine system; S6, based on the Lagrangian energy method, giving the dynamic model of the semi-submersible floating wind turbine system.

[0007] Further, in step S1, the components of the floating wind turbine include a floating platform, a nacelle, a tower, and a wind rotor; define D r as the vertical distance from the center of gravity of the floating platform to the center of gravity of the wind rotor, and define d r as the horizontal distance from the center of gravity of the wind rotor to the tip center of the tower, and define d ncDefine it as the horizontal distance from the center of gravity of the nacelle to the tip center of the tower, and denote it as D t Define it as the vertical distance from the center of gravity of the floating platform to the center of gravity of the tower; Define m r as the mass of the wind turbine rotor, define m t as the mass of the tower, define m nc as the mass of the nacelle, define m p as the mass of the floating platform, define I nc as the inertia tensor of the nacelle, define I p as the inertia tensor of the floating platform, define I r as the inertia tensor of the wind turbine rotor, define I t as the inertia tensor of the tower.

[0008] Furthermore, in step S2, define two coordinate systems, which are respectively:

[0009] Inertial reference coordinate system O(XYZ), the X-axis is along the wind direction, the Z-axis is vertically upward along the axis of the tower of the floating wind turbine, the origin O is the intersection of the Z-axis and the mean sea level, and the direction of the Y-axis is determined by the right-hand rule;

[0010] Platform body-fixed coordinate system o(xyz), which coincides with O(XYZ) at the undisturbed position. The origin position of the platform body-fixed coordinate system changes with the movement of the platform, and the direction changes with the rotation of the platform.

[0011] Furthermore, in step S3, use r p =[r x ,r t ,r z T ,θ p =[θ x ,θ y ,θ z T to represent the basic displacement of the floating wind turbine in six degrees of freedom in the inertial reference coordinate system. r i | i＝x,y,z are the displacement of surge, sway, and heave respectively, and θ i | i＝x,y,z are the angular displacements of roll, pitch, and yaw respectively. Use to represent the translational velocity and angular velocity of the floating wind turbine in the inertial reference coordinate system;

[0012] The translational velocity [v of the floating platform in the platform body-fixed coordinate system p can be expressed as: p

[0013] ​​​

[0014] where \(v\) i |\) i＝x,y,z are the translational velocities corresponding to the surge, sway, and heave directions in the platform body-fixed coordinate system respectively, \(R\) is the rotation matrix for transforming a vector from to , and \(R^{\mathrm{T}}\) T represents the transpose matrix of matrix \(R\); correspondingly, the motion equations for the Euler angle sequence are:

[0015]

[0016] where \([\omega\) p \) p =\([\omega_x\omega_y\omega_z]\) is the angular velocity of the floating platform in x \(\omega_x\) y \(\omega_y\) z \(\omega_z\) , and \(\omega_x\) i |\) i＝x,y,z are the angular velocities corresponding to the roll, pitch, and yaw of the floating platform in the platform body-fixed coordinate system respectively;

[0017] The velocity vectors of the center of mass \(G_t\) of the tower t , the center of mass \(G_n\) of the nacelle nc , and the center of mass \(G_r\) of the rotor r are respectively:

[0018] \(v_{G_t}\) t = \(v\) p +\(\omega\) p \(\times r_{G_t}\) t

[0019]

[0020] \(v_{G_n}\) r = \(v\) p +\(\omega\) p \(\times r_{G_n}\) r

[0021] where \(r_{G_t}\) t , \(r_{G_n}\) r respectively represent the centroid coordinate vectors of the tower, nacelle, and wind turbine rotor. The tower angular velocity \(\omega_t\) t and the nacelle angular velocity \(\omega_n\) nc both rotate with the same angular velocity as the platform angular velocity \(\omega\) p , i.e., \(\omega_t\) t =\(\omega_n\) nc =\(\omega\) p , and the rotor angular velocity \(\omega_r\) r =\(\omega\) p +\(\Omega\) r , where \(\Omega\) r =\([\Omega_00]\)T , Ω represents the rotor spin speed.

[0022] Furthermore, in step S4, the kinetic energy of the floating platform and potential energy the kinetic energy of the tower and potential energy the kinetic energy of the nacelle and potential energy the kinetic energy of the wind turbine rotor and potential energy are obtained by the following formula:

[0023]

[0024] where g is the acceleration due to gravity, the vector [r to p , [r ncO p and [r rO p represent the displacements of the center of mass of the tower, nacelle, and rotor relative to the origin, The total kinetic energy and total potential energy of the floating wind turbine are:

[0025]

[0026] Furthermore, in step S5, assume that the floating platform consists of 7 homogeneous cylinders, where one central cylinder i = 1 and three upper cylinders i = 2, 3, 4 are floating in water, while three bottom cylinders i = 5, 6, 7 are completely submerged in water. According to Archimedes' principle, the buoyancy force F B and the corresponding moment T B of the i-th cylinder are as follows:

[0027]

[0028] where ρ w and g are the water density; V d represents the total instantaneous submerged volume of the floating platform; the symbol × represents the vector cross product; [r B p is the position vector of the buoyancy center of the platform in ;

[0029] For the cylinders subjected to lateral water flow, the wave force is calculated by the Morison equation. The hydrodynamic force on the i-th underwater cylinder can be calculated as follows:

[0030]

[0031] where L i ​​​​is the submerged length of the i-th cylinder; and A i are the drag coefficient, added mass coefficient, and cross-sectional area of the i-th cylinder, respectively, and v ref,i is the relative velocity between the water particles and the submerged cylinder. Considering a volume element of length dz on the submerged cylinder, the position, velocity, and acceleration vectors of the center point of the volume element (denoted by point a i ) in are denoted by v a,i and , respectively; and denote the velocity and acceleration of the water particles at the corresponding point a i height of the i-th cylinder, respectively; the amplitude of (·) is denoted by ∥(·)∥; the symbol (·) ⊥ denotes the component of the vector (·) perpendicular to the central axis of the cylinder;

[0032] The three bottom columns of the platform (i = 5, 6, 7) are also affected by additional forces (including drag and inertial forces), and their calculation formula is

[0033]

[0034] where Δ P = A i p bi -(A i -A i-3 )p ti , and are the drag coefficient and added mass coefficient in the heave direction of the i-th cylinder, respectively, denotes the unit vector in the coordinate system satisfying p bi and p ti denote the dynamic pressures at the bottom and top of the heave plate of the i-th (i = 5, 6, 7) cylinder, respectively; and denote the position, velocity, and acceleration of the centroid of the i-th bottom column, respectively; the symbol denotes the projection component of parallel to the central axis of the submerged cylinder;

[0035] The total wave force F D and the corresponding moment T D acting on the platform are:

[0036]

[0037] The aerodynamic force F acting on the wind turbine A and the corresponding torque T A can be provided by the following formula:

[0038]

[0039] where F a and τ a are the wind thrust and the aerodynamic torque respectively, and can be expressed as:

[0040]

[0041] where R r is the rotor radius of the wind turbine, ρ a represents the air density, u w is the relative velocity between the wind and the rotor, expressed as u w = v w - v r where v w is the wind speed vector; ∥(u w ) ∥ ∥ is the magnitude of the relative wind speed parallel to the axis of the wind turbine, C t (λ,β) and C p (λ,β) represent the thrust and power coefficients of the wind turbine respectively; λ is the tip speed ratio, and β is the pitch angle of the blade;

[0042] For a semi-submersible floating wind turbine, the mooring system consists of 3 tensioned catenaries, and the corresponding anchors on the seabed are evenly distributed in a circle with an angle of 120°, and the mooring forces and the corresponding torques are determined by the quasi-static method, denoted by F M and T M respectively;

[0043] The total external force F and the corresponding torque T acting on the floating wind turbine system can be calculated by the following formula:

[0044] F = F B + F D + F A + F M

[0045] T = T B + T D + T A + T M .

[0046] Furthermore, in step S6, according to the Lagrangian energy modeling method, the model motion equation of the semi-submersible floating wind turbine is derived as:

[0047]

[0048] where q = [v p ω p Ω] T , M(q) is the system mass matrix, and the matrix dimension is 7*7; is the column matrix of the forces acting on the system, and the matrix dimension is 7*1.

[0049] This solution provides a control-oriented dynamic modeling method for a semi-submersible floating wind turbine, constructs a simplified dynamic model guided by the control of the floating wind turbine, and achieves a balance between the simplicity and accuracy of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic diagram of the semi-submersible floating wind turbine system according to an embodiment of the present invention;

[0051] Figure 2 is a schematic diagram of the method flow according to an embodiment of the present invention;

[0052] Figure 3 is a schematic diagram of the motion response of the wind turbine system without considering the wind and wave excitation in an embodiment of the present invention;

[0053] Figure 4 is a schematic diagram of the motion response of the wind turbine system considering the wind and wave excitation in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The technical solutions in the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0055] This embodiment provides a control-oriented dynamic modeling method for a semi-submersible floating wind turbine, as Figure 2 shown, including the following steps:

[0056] Step 1: Describe the components of the floating wind turbine structure and define the characteristic parameters of the components;

[0057] Step 2: Establish a coordinate system for describing the dynamics of the floating wind turbine;

[0058] Step 3: Give the dynamic descriptions of the components of the floating wind turbine;

[0059] Step 4: Calculate the total energy of the floating wind turbine system;

[0060] Step 5: Calculate the external loads acting on the floating wind turbine system;

[0061] Step 6: Based on the Lagrangian energy method, give the dynamic model of the semi-submersible floating wind turbine system.

[0062] Among them, Step 1 includes:

[0063] The schematic diagram of the semi-submersible floating wind turbine is as Figure 1As shown. This structure includes four main mechanical components, namely the floating platform, the nacelle, the tower, and the wind turbine rotor, which play an important role in the dynamic performance of the system. From Figure 1 It can be seen that D r represents the vertical distance from the center of gravity of the floating platform to the center of gravity of the wind turbine rotor, and d r represents the horizontal distance from the center of gravity of the wind turbine rotor to the center of the tower tip, while d nc is the horizontal distance from the center of gravity of the nacelle to the center of the tower tip. At the same time, D t is defined as the vertical distance from the center of gravity of the platform to the center of gravity of the tower.

[0064] In the floating wind power generation system, in order to describe the geometric characteristics and dynamic parameters of each key component, this embodiment introduces the symbols in Table 1 below. As can be seen from Table 1, the dynamic characteristics of the system are characterized by the mass parameters and inertia tensors of each component, where m r represents the mass of the rotor, m t represents the mass of the tower, m nc represents the mass of the nacelle, while m p is the mass of the floating platform; I nc is the inertia tensor of the nacelle, I p is the inertia tensor of the floating platform, I r is the inertia tensor of the rotor, I t is the inertia tensor of the tower.

[0065] Fan parameters used in the proposed model in Table 1

[0066]

[0067] Step 2 includes:

[0068] Define two coordinate systems, namely:

[0069] 1) Inertial reference coordinate system The X-axis is along the wind direction, the Z-axis is vertically upward along the axis of the floating wind turbine tower, the origin O is the intersection of the Z-axis and the mean sea level, and the direction of the Y-axis is determined by the right-hand rule;

[0070] 2) Platform body-fixed coordinate system Coincides with O(XYZ) at the undisturbed position. The origin position of the platform body-fixed coordinate system changes with the movement of the platform, and the direction changes with the rotation of the platform;

[0071] To simplify the description of the system kinematics, the present invention adopts a unified vector notation. The vector subscript is used to represent the reference frame where the vector is located. The abbreviations of the two reference frames are I and p respectively. For example, for any vector a, [a] I indicates that the vector a is in the inertial reference coordinate system Denoted as follows; for any vector b, [b] p Indicates that the vector b is represented in the body-fixed coordinate system of the platform If no subscript is used, it represents any reference frame.

[0072] Step 3 includes:

[0073] Step 3.1, in the inertial reference coordinate system, r p =[r x , r y , r z T , θ p =[θ x , θ y , θ z T Represents the basic displacement of the floating wind turbine in six degrees of freedom in the inertial reference coordinate system. r i | i＝x,y,z Are the displacement amounts of surge, sway, and heave respectively; θ i | i＝x,y,z Are the angular displacement amounts of roll, pitch, and yaw respectively; At the same time, use To represent the translational velocity and angular velocity of the floating wind turbine in the inertial reference coordinate system.

[0074] The translational velocity [v of the floating platform in the body-fixed coordinate system of the platform p p Can be expressed as:

[0075]

[0076] Where v i | i＝x,y,z Are the translational velocities corresponding to the surge, sway, and heave directions in the body-fixed coordinate system of the platform respectively. R is the rotation matrix for transforming the vector from to . R T Represents the transpose matrix of the matrix R; Correspondingly, the motion equation for the Euler angle sequence is:

[0077]

[0078] Where, [ω p p =[ω x ω y ω z is the rotational angular velocity of the floating platform in . ω i | i＝x,y,z Are the translational velocities corresponding to the roll, pitch, and yaw directions in the body-fixed coordinate system of the platform ​​​​The angular velocities corresponding to the roll, pitch, and yaw of the lower floating platform.

[0079] Step 3.2, the velocity vectors of the center of mass of the tower (G t ), the center of mass of the nacelle (G nc ), and the center of mass of the rotor (G r ) are expressed as:

[0080]

[0081] where r t , r r respectively represent the center-of-mass coordinate vectors of the tower, nacelle, and rotor. Additionally, the tower angular velocity ω t and the nacelle angular velocity ω nc both rotate at the same angular velocity as the platform angular velocity ω p , i.e., ω t = ω nc = ω p , and the rotor angular velocity ω r = ω p + Ω r , where Ω r = [Ω 0 0] T , and Ω represents the rotor spin speed.

[0082] Step 4 includes:

[0083] The main components of the floating wind turbine include a floating platform, a tower, a nacelle, and a rotor. Their corresponding kinetic energies, namely the kinetic energy of the floating platform and potential energy the kinetic energy of the tower and potential energy the kinetic energy of the nacelle and potential energy the kinetic energy of the rotor and potential energy can be obtained from the following equations:

[0084]

[0085] In the equations, g is the acceleration due to gravity, and the vectors [r to p , [r ncO p and [r rO p respectively represent the displacements of the centers of mass of the tower, nacelle, and rotor relative to the origin; Therefore, the total kinetic energy and total potential energy of the floating wind turbine are

[0086] ​​​

[0087] Step 5 includes:

[0088] Step 5.1, assume that the floating platform consists of 7 homogeneous and uniform cylinders, where one central cylinder (i = 1) and three upper cylinders (i = 2, 3, 4) are floating in water, while the three bottom cylinders (i = 5, 6, 7) are completely submerged in water. According to Archimedes' principle, the buoyancy force F B and the corresponding moment T B of the i-th cylinder can be given by the formula:

[0089]

[0090] where ρ w and g are the water density and gravitational acceleration respectively; V d represents the total instantaneous submerged volume of the floating platform; the symbol × represents the vector cross product; [r B p is the position vector of the center of buoyancy of the platform in .

[0091] Step 5.2, for the cylinders under the action of lateral water flow, the Morison equation can be used to calculate the wave force. Specifically, the hydrodynamic force on the i-th submerged cylinder can be calculated as follows:

[0092]

[0093] where L i is the submerged length of the i-th cylinder; and A i are the drag coefficient, added mass coefficient and cross-sectional area of the i-th cylinder respectively. v ref,i is the relative velocity between the water particle and the submerged cylinder. Considering a volume element of length dz on the submerged cylinder, the position, velocity and acceleration vectors of the center point of the volume element (denoted by point a i ) in are represented by [r ai p , v a,i and respectively; and represent the velocity and acceleration of the water particle at the corresponding point a i height of the i-th cylinder respectively; the amplitude of (·) is denoted by ||(·)||; the symbol (·) ⊥ represents the component of the vector (·) perpendicular to the center line of the cylinder.

[0094] In addition, the three bottom cylinders (i = 5, 6, 7) of the platform are also affected by additional forces (including drag and inertial forces), and their calculation formula is:​​

[0095]

[0096] wherein, Δ P = A i p bi - (A i - A i-3 )p ti ,

[0097] Here and are the drag coefficient and added mass coefficient in the heave direction of the i-th cylinder, respectively. represents the unit vector in the coordinate system and satisfies p bi and p ti represent the dynamic pressures at the bottom and top of the i-th (i = 5, 6, 7) heave plate, respectively; and represent the position, velocity and acceleration of the centroid of the i-th bottom column, respectively; the symbol represents the projection component of in the direction parallel to the center line of the submerged cylinder.

[0098] The total wave force F D and the corresponding moment T D acting on the platform are:

[0099]

[0100] Step 5.3, the aerodynamic force F A and the corresponding moment T A acting on the wind turbine can be provided by the following formula:

[0101]

[0102] where F a and τ a are the wind thrust and aerodynamic torque, respectively, and can be expressed as:

[0103]

[0104] where, R r is the rotor radius of the wind turbine, ρ a represents the air density. u w is the relative velocity between the wind and the rotor, expressed as u w = v w - v r , where v w is the wind speed vector; ∥(uw ) ∥ ∥ is the magnitude of the relative wind speed parallel to the wind turbine axis. C t (λ,β) and C p (λ,β) represent the thrust and power coefficients of the wind turbine respectively; λ is the tip speed ratio and β is the pitch angle of the blade.

[0105] Step 5.4, for a semi-submersible floating wind turbine, the mooring system consists of 3 tension catenary lines, and the corresponding anchors on the seabed are evenly distributed in a circle with an angle of 120°. The mooring force and the corresponding moment can be determined by the quasi-static method, denoted by F M and T M respectively. This method ignores the cable inertia effect and the hydrodynamic load applied to the mooring line.

[0106] Step 5.5, therefore, the total external force F and the corresponding moment T acting on the floating wind turbine system can be calculated by the following formulas:

[0107] F = F B + F D + F A + F M (15)

[0108] T = T B + T D + T A + T M (16)

[0109] Step 6 includes that according to the Lagrangian energy modeling method, the model motion equation of the semi-submersible floating wind turbine can be derived in the following form:

[0110]

[0111] where q = [v p ω p Ω] T . M(q) and are the system mass matrix (matrix dimension is 7*7) and the column matrix of the forces acting on the system (matrix dimension is 7*1) respectively.

[0112] To verify the effectiveness of the proposed model, the simulation responses generated by this model were compared with those of the FAST model. Two environmental load (LC) conditions were tested, as shown in Table 2.

[0113] Table 2 Environmental conditions applied to the motion simulation of the floating wind turbine

[0114]

[0115] In the environmental excitation LC-1 (calm wind and calm waves), the initial conditions are set as the horizontal displacement of the platform being 5 m, the rotation angle being 9°, and the simulation duration being 1000 s under the condition of the rotor idling. The platform motion responses obtained from the developed FWT model are compared with the motion responses generated by the widely used FAST model, as Figure 3 shown. It can be clearly seen from the time-domain response that there are significant similarities between the two methods.

[0116] A combined wind and wave load test (LC-2) was conducted on the model. Specifically, the average velocity of the turbulent wind is 18 m / s, and the turbulence intensity is 10%. At the same time, a regular wave condition with a peak period T p = 10 s and an effective wave height H s = 3 m is considered. Here, the blade pitch angle is set to β = 12°. The platform motion time response and the rotor speed response of the system are compared as Figure 4 shown. These results clearly show that the proposed floating wind turbine model effectively predicts the main motions observed in the high-fidelity FAST model, verifying the effectiveness of the proposed model.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A control-oriented dynamic modeling method for a semi-submersible floating wind turbine, characterized in that: Including the following steps: S1. Describe the components of the floating wind turbine structure and define the characteristic parameters of the components; S2. Establish a coordinate system for describing the dynamics of the floating wind turbine; S3. Give the dynamic descriptions of the components of the floating wind turbine; S4. Calculate the total energy of the floating wind turbine system; S5. Calculate the external loads on the floating wind turbine system; S6. Based on the Lagrangian energy method, give the dynamic model of the semi-submersible floating wind turbine system.

2. A dynamics modeling method for a control-oriented semi-submersible floating wind turbine according to claim 1, characterized in that: In step S1, the components of the floating wind turbine include a floating platform, a nacelle, a tower, and a wind rotor; let D r be defined as the vertical distance from the center of gravity of the floating platform to the center of gravity of the wind rotor, and let d r be defined as the horizontal distance from the center of gravity of the wind rotor to the tip center of the tower, and let d nc be defined as the horizontal distance from the center of gravity of the nacelle to the tip center of the tower, and let D t be defined as the vertical distance from the center of gravity of the floating platform to the center of gravity of the tower; let m r be the mass of the wind rotor, let m t be the mass of the tower, let m nc be the mass of the nacelle, let m p be the mass of the floating platform, let I nc be the inertia tensor of the nacelle, let I p be the inertia tensor of the floating platform, let I r be the inertia tensor of the wind rotor, and let I t be the inertia tensor of the tower.

3. A dynamics modeling method for a control-oriented semi-submersible floating wind turbine according to claim 2, characterized in that: In step S2, two coordinate systems are defined, namely: Inertial reference coordinate system The X-axis is along the wind direction, the Z-axis is vertically upward along the tower axis of the floating wind turbine, the origin O is the intersection of the Z-axis and the mean sea level, and the direction of the Y-axis is determined by the right-hand rule; Platform body-fixed coordinate system It coincides with O(XYZ) at the undisturbed position. The origin position of the platform body-fixed coordinate system changes with the movement of the platform, and the direction changes with the rotation of the platform.

4. A control-oriented dynamic modeling method for a semi-submersible floating wind turbine according to claim 3, characterized in that: In step S3, use r p =[r x , r y , r z T , θ p =[θ x , θ y , θ z T to represent the basic displacement of the floating wind turbine in six degrees of freedom in the inertial reference coordinate system. r i | i＝x，y，z are the displacement of surge, sway, and heave respectively. θ i | i＝x，y，z are the angular displacements of roll, pitch, and yaw respectively. Use to represent the translational velocity and angular velocity of the floating wind turbine in the inertial reference coordinate system;​​ The floating platform in the platform body-fixed coordinate system and the translational velocity [v p p can be expressed as:​ where v i | i＝x，y，z are the translational velocities corresponding to the surge, sway, and heave directions in the platform's body-fixed coordinate system, R is the rotation matrix for transforming a vector from to and R is the rotation matrix from T denotes the transpose of matrix R; correspondingly, the motion equations for the Euler angle sequence are as follows: Among them, [ω p p = [ω x ω y ω z is the rotational angular velocity of the floating platform in , and ω i | i＝x，y，z are respectively the angular velocities corresponding to the roll, pitch, and yaw of the floating platform in the body-fixed coordinate system of the platform ;​ The centroid G of the tower t , the centroid G of the nacelle nc and the centroid G of the rotor r have velocity vectors respectively as follows: v t = v p + ω p × r t v r = v p + ω p × r r where r t , r r represent the centroid coordinate vectors of the tower, nacelle and wind turbine rotor respectively, the tower rotational angular velocity ω t and the nacelle rotational angular velocity ω nc both rotate at the same rotational angular velocity as the platform angular velocity ω p , that is, ω t = ω nc = ω p , the rotor angular velocity ω r = ω p + Ω r , where Ω r = [Ω 0 0] T , and Ω represents the rotor spin speed.

5. A dynamics modeling method for a control-oriented semi-submersible floating wind turbine according to claim 4, characterized in that: In step S4, the kinetic energy of the floating platform and potential energy the kinetic energy of the tower and potential energy the kinetic energy of the nacelle and potential energy the kinetic energy of the wind turbine rotor and potential energy are obtained by the following formula: where \(g\) is the acceleration due to gravity, and the vectors \([r to p \), \([r ncO p \) and \([r rO p represent the displacements of the centers of mass of the tower, nacelle, and rotor relative to the origin respectively. The total kinetic energy and total potential energy of the floating wind turbine are: ​​​​ 6. A control-oriented dynamic modeling method for a semi-submersible floating wind turbine according to claim 5, characterized in that: In step S5, it is assumed that the floating platform includes seven homogeneous cylinders, where one central cylinder i = 1 and three upper cylinders i = 2, 3, 4 are all floating in water, while three bottom cylinders i = 5, 6, 7 are completely submerged in water. According to Archimedes' principle, the buoyancy F of the i-th cylinder B and the corresponding moment T B are as follows: [T B p =[r B p ×[F B p ​​​ where ρ w and g are the water density; V d represents the total instantaneous submerged volume of the floating platform; the symbol × represents the vector cross product; [r B p is the position vector of the buoyancy center of the platform in the​ For a cylinder subjected to a lateral water flow, the wave force is calculated by the Morison equation, and the hydrodynamic force on the i-th submerged cylinder can be calculated as follows: where L i is the submergence length of the i-th cylinder; and A i are the drag coefficient, added mass coefficient and cross-sectional area of the i-th cylinder respectively, and v ref，i is the relative velocity between the water particle and the submerged cylinder. Considering a volume element of length dz on the submerged cylinder, the position, velocity and acceleration vectors of the center point of the volume element (denoted by point a i ) in are denoted by v a，i and respectively; and represent the velocity and acceleration of the water particle at the corresponding point a i height of the i-th cylinder respectively; the amplitude of (·) is denoted by ||(·)||; the symbol (·) ⊥ represents the component of the vector (·) in the direction perpendicular to the center line of the cylinder; The three bottom columns (i = 5, 6, 7) of the platform will also be affected by additional forces (including resistance and inertia forces), and its calculation formula is where, Δ P = A i p bi - (A i - A i-3 ) p ti , and are the drag coefficient and added mass coefficient in the heave direction of the i-th cylinder respectively, represents the unit vector of the coordinate system satisfying p bi and p ti represent the dynamic pressures at the bottom and top of the i-th (i = 5, 6, 7) heave plate respectively; and represent the position, velocity and acceleration of the centroid of the i-th bottom column respectively; the symbol represents the projection component of in the direction parallel to the center line of the submerged cylinder; The total wave force F D and the corresponding moment T D are as follows: The aerodynamic force F acting on the wind turbine A and the corresponding torque T A can be provided by the following formula: Among them F a and τ a are the wind thrust and the aerodynamic torque respectively, and can be expressed as: where, R r is the radius of the wind turbine rotor, ρ a represents the air density, u w is the relative velocity between the wind and the rotor, expressed as u w = v w - v r , where v w is the wind speed vector; ||(u w ) || || is the magnitude of the relative wind speed parallel to the axis of the wind turbine, C t (λ, β) and C p (λ, β) represent the thrust and power coefficients of the wind turbine respectively; λ is the tip speed ratio, and β is the pitch angle of the blade; For a semi-submersible floating wind turbine, the mooring system consists of three tension catenaries, and the corresponding anchors on the seabed are evenly distributed in a circle with an angle of 120°. The mooring forces and the corresponding moments are determined by the quasi-static method, denoted by F M and T M respectively; The total external force F and the corresponding torque T acting on the floating wind turbine system can be calculated by the following formula: F = F B +F D +F A +F M T = T B + T D + T A + T M .

7. A control-oriented dynamic modeling method for a semi-submersible floating wind turbine according to claim 6, characterized in that: In step S6, according to the Lagrangian energy modeling method, the model motion equation of the semi-submersible floating wind turbine is derived as: where q = [v p ω p Ω] T , M(q) is the system mass matrix with a matrix dimension of 7*7; is the column matrix of the forces acting on the system with a matrix dimension of 7*1.

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