Method for forecasting heaving motion of offshore wind power operation and maintenance ship

Abstract

The invention discloses an offshore wind power operation and maintenance ship heaving motion forecasting method, and relates to a new operation and maintenance ship heaving motion short-time forecasting method based on acceleration response Porny decomposition. S1, construction of heaving motion response of the operation and maintenance ship; s2, carrying out Prony decomposition on the acceleration of the heaving motion; s3, forecasting the response of the heaving motion, calculating the extreme value and the residue of the acceleration response by performing Prony decomposition on the actually measured acceleration response data, and establishing the relationship between the amplitude, the frequency, the damping and the phase of the response of the heaving motion and the extreme value and the residue of the acceleration response through the data relationship between the acceleration and the displacement of the operation and maintenance ship; and according to the response amplitude, the frequency, the damping and the phase of the heaving motion of the operation and maintenance ship, carrying out short-time forecasting on the heaving motion, and laying a research foundation of a wave compensation device of an embarkation system.

Description

Technical Field

[0001] The present invention relates to the field of marine engineering, and in particular to a method for predicting the heave and sink motion of an offshore wind power operation and maintenance vessel. Background Art

[0002] After an offshore wind turbine has been in operation for a certain period of time, it is necessary to rely on an operation and maintenance ship to send operation and maintenance personnel to the offshore wind power facilities for maintenance operations. However, the operation and maintenance ship is limited by hydrological and meteorological factors when it is out in the sea. The heave and sinking movement of the operation and maintenance ship caused by wave disturbance seriously affects the normal operation and maintenance of offshore wind power. For example, large-scale heave and sinking movements make it very difficult for operators to board the wind turbine foundation. Operation and maintenance operations can only be carried out under relatively calm sea conditions, and the operation time window is very limited. Therefore, it is necessary to develop an algorithm for predicting the heave and sinking movement of offshore wind power operation and maintenance ships, and then develop a wave compensation device for the boarding system to expand the operation and maintenance time window and achieve cost reduction and efficiency improvement in wind power operation and maintenance.

[0003] The operating environment of offshore wind power operation and maintenance vessels lacks a fixed reference coordinate system, making it difficult to directly record the displacement response of the ship's motion, and its acceleration response is usually measured. Summary of the invention

[0004] In order to solve the above problems, the present technical solution provides a method for predicting the heave and sink motion of an offshore wind power operation and maintenance vessel.

[0005] To achieve the above purpose, the technical solution is as follows:

[0006] A method for predicting the heave motion of an offshore wind power operation and maintenance ship, a new method for short-term prediction of the heave motion of an offshore wind power operation and maintenance ship based on acceleration response Porny decomposition, comprising the following steps;

[0007] S1, construction of the heave motion response of the maintenance ship;

[0008] S2, Prony decomposition of heave motion acceleration;

[0009] S3, heave motion response forecast.

[0010] In some embodiments, the step S1 further includes the following steps:

[0011] S101, when the offshore wind power operation and maintenance ship is operating, it generates motion response under the action of waves. After reaching a stable state, the motion frequency of the operation and maintenance ship is consistent with the wave frequency, and its heave RAO is:

[0012]

[0013] where η a is the wave height of the component with frequency ω in the wave, z a is the amplitude of the ship's heave freedom when the wave frequency is ω;

[0014] S102, when calculating the heave response according to the ship RAO, we get:

[0015]

[0016] Among them, μ m is the mth direction of the wave, a m,n is the amplitude of the nth wave component in the mth direction, ε m,n is the phase of the nth wave component in the mth direction, ε zη (ω n ,μ n ) is the phase difference;

[0017] S103, combining step S102 to obtain the ship heave response formula:

[0018]

[0019] Among them, A n is the response amplitude caused by the nth wave component, φ n The phase of the response caused by the nth wave component.

[0020] In some embodiments, step S2 further includes the following steps:

[0021] S201, using the measured acceleration response to determine the coordinate system, according to step S103, the measured acceleration response data is expressed in exponential form to obtain:

[0022]

[0023] Among them, p is the decomposition order; γ n is the residue, and there is λ n is the extreme value λ n =-α n +iω n ; B n is the amplitude, θ n is the phase angle, α n is the attenuation coefficient, ω n is the frequency;

[0024] S202, the acceleration data measured by the maintenance ship is a discrete value, let For the discrete acceleration response value y k =y(kΔt), whose Prony decomposition is:

[0025]

[0026] in, Δt is the sampling time interval;

[0027] S203, using a first-order difference equation to replace the formula in step S202, and solving the eigenvalue of the equation, and finally constructing a Hankel matrix to obtain:

[0028]

[0029] Where μ and ν are the number of rows and columns of the Hankel matrix respectively;

[0030] S204, respectively substitute k=0 and k=1 into the formula of step S203, and perform SVD on H(0), so as to use the SVD decomposition of H(0) to represent H(1), and obtain:

[0031]

[0032] Among them, U 1 and V 1 is an orthogonal matrix, Σ 1 is the diagonal matrix composed of the singular values ​​of H(0), and A is the system matrix;

[0033] S205, multiply the formula in step S204 by the left and right multiplication The system matrix is ​​obtained as:

[0034]

[0035] S205, perform eigenvalue analysis on the system matrix A, and its eigenvalue is z in step S202 n , so that the extreme value of the Prony decomposition in step S202 is:

[0036]

[0037] S206, substituting the formula of step S205 into step S202 to obtain the extreme value of the heave acceleration response of the maintenance vessel.

[0038] In some embodiments, step S3 further includes the following steps:

[0039] S301, the acceleration response extreme value and residue obtained by Prony decomposition are substituted into the formula of step S201, and the heave acceleration response of the operation and maintenance ship is expressed as a trigonometric function form by Euler formula, and the result is:

[0040]

[0041] S302, the acceleration response of the maintenance ship is a real number, and the corresponding extreme value and residue are conjugate complex numbers, so the imaginary parts in the formula of step S301 will cancel each other out. Compared with the formula in step S103, there is the following relationship p=2N, and then the trigonometric function expression of the acceleration of the maintenance ship heave response is obtained as follows:

[0042]

[0043] S303, according to Euler's formula, the formula of step S302 is written as follows:

[0044]

[0045] S304, integrating the formula in step S303, and obtaining the speed of the ship's heave motion as:

[0046]

[0047] in, C 1 is the integration constant;

[0048] S305, integrating the formula in step S304, and obtaining the displacement response of the ship heave motion as:

[0049]

[0050] in

[0051] S306, perform Prony decomposition on the acceleration response data of the heave motion of the maintenance ship in the previous period to obtain the corresponding extreme values ​​and residues, and predict the heave motion response of the maintenance ship in the next period through the extreme values ​​and the amplitude, frequency and phase of the residue calculation formula in step S305. The integral constant in the formula of step S305 is a trend term, which can be directly removed when predicting the heave motion response of the maintenance ship.

[0052] The beneficial effects of this application are:

[0053] For step S1, the present invention uses RAO to construct a mathematical model of the heave motion of an offshore wind power operation and maintenance ship, laying the foundation for predicting the displacement response based on acceleration;

[0054] For step S2, the present invention uses the Prony method to decompose the measured heave acceleration response, obtain the extreme value and residue of the acceleration, and characterize the acceleration response by the extreme value and residue;

[0055] For step S3, the present invention constructs a mathematical relationship between the extreme value and the residue and the trigonometric function parameters, and obtains the heave displacement response from the heave acceleration data by an integral method. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0057] Figure 1 is a delay function diagram of an embodiment of the present invention;

[0058] Figure 2 is a wave load diagram of an embodiment of the present invention;

[0059] Figure 3 is a comparison diagram of the Prony decomposition and reconstruction data of the heave acceleration response and the original value of the embodiment of the present invention;

[0060] Figure 4 It is a comparison diagram between the predicted value of the heave response and the theoretical value according to the embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0062] Please refer to Figure 1-4 As shown, in order to solve the above problems, a method for predicting the heave motion of an offshore wind power operation and maintenance ship is provided in the present invention. The method performs Prony decomposition on the measured acceleration response data, calculates the extreme value and residue of the acceleration response, and establishes the relationship between the heave motion response amplitude, frequency, damping and phase and the acceleration response extreme value and residue through the data relationship between the acceleration and displacement of the operation and maintenance ship. Then, according to the heave motion response amplitude, frequency, damping and phase of the operation and maintenance ship, a short-term prediction of the heave motion is performed, laying the foundation for the development of the wave compensation device of the boarding system.

[0063] The following is a step-by-step analysis of this solution:

[0064] Maintenance ship heave response construction:

[0065] When the offshore wind power operation and maintenance ship is operating, it generates motion response under the action of waves. After reaching a stable state, the motion frequency of the operation and maintenance ship is consistent with the wave frequency, and its heave RAO can be expressed as:

[0066]

[0067] Where η a is the wave height of the component with frequency ω in the wave, z a is the amplitude of the ship's heave and sink degrees of freedom motion when the wave frequency is ω.

[0068] When calculating the heave response based on the ship RAO, the expression is as follows:

[0069]

[0070] In the formula, μ m is the mth direction of the wave, a m,n is the amplitude of the nth wave component in the mth direction, ε m,n is the phase of the nth wave component in the mth direction, ε zη (ω n ,μ n ) is the phase difference.

[0071] By combining equation (2), the ship heave response can be expressed as follows:

[0072]

[0073] In the formula, A n is the response amplitude caused by the nth wave component, φ n The phase of the response caused by the nth wave component.

[0074] Prony decomposition of heave acceleration:

[0075] When an offshore wind power maintenance ship is operating, it is difficult to find a stationary reference coordinate system, so its acceleration response is often measured. From formula (3), it can be seen that the heave motion of the maintenance ship is in the form of cosine superposition, and its acceleration response is also in this form. The measured acceleration response data is expressed in exponential form, and we get:

[0076]

[0077] Where p is the decomposition order; γ n is the residue, and there is λ n is the extreme value λ n =-α n +iω n ; B n is the amplitude, θ n is the phase angle, α n is the attenuation coefficient, ω n is the frequency.

[0078] The acceleration data measured by the maintenance ship is usually discrete values. For the convenience of expression, let For the discrete acceleration response value y k =y(kΔt), whose Prony decomposition is:

[0079]

[0080] In the formula, Δt is the sampling time interval.

[0081] Formula (5) is the general solution of the p-order difference equation. The first-order difference equation is used instead of the higher-order difference equation to solve the eigenvalue in formula (5), thereby avoiding high condition numbers and ill-conditioned problems. In order to solve the extreme value (eigenvalue) and residue of the Prony decomposition of the heave acceleration of the maintenance ship, the following Hankel matrix is ​​constructed:

[0082]

[0083] Where μ and ν are the number of rows and columns of the Hankel matrix, respectively.

[0084] Substitute k=0 and k=1 into equation (6) respectively, and perform SVD on H(0), so as to use the SVD decomposition of H(0) to represent H(1), and we get:

[0085]

[0086] Where U 1 and V 1 is an orthogonal matrix, Σ 1 is the diagonal matrix consisting of the singular values ​​of H(0), and A is the system matrix.

[0087] Multiply both sides of equation (7) by and right multiplication The system matrix is ​​obtained as:

[0088]

[0089] Perform eigenvalue analysis on the system matrix A, and its eigenvalue is z in formula (5) n , so the extreme value of Prony decomposition in formula (5) is:

[0090]

[0091] Then, by substituting equation (9) into equation (5), we can further obtain the extreme value of the heave acceleration response of the operation and maintenance ship.

[0092] Heave Response Forecast

[0093] Substitute the acceleration response extreme value and residue obtained by Prony decomposition into equation (4), and express the heave acceleration response of the operation and maintenance ship in the form of trigonometric function through the Euler formula:

[0094]

[0095] The acceleration response of the maintenance ship is a real number, and the corresponding extreme value and residue are conjugate complex numbers, so the imaginary parts in equation (10) will cancel each other out. Compared with equation (3), there is the following relationship p = 2N, and then the trigonometric function expression of the acceleration of the maintenance ship heave response is obtained as:

[0096]

[0097] According to Euler's formula, equation (11) can be written as follows:

[0098]

[0099] Integrating equation (12), we get the velocity of the ship's heave motion as:

[0100]

[0101] In the formula, C 1 is the integration constant.

[0102] Similarly, by further integrating equation (13), the displacement response of the ship heave motion is obtained as follows:

[0103]

[0104] In the formula,

[0105] The acceleration response data of the heave motion of the maintenance ship in the previous period is Prony decomposed to obtain the corresponding extreme values ​​and residues. The amplitude, frequency and phase of formula (14) are calculated by the extreme values ​​and residues, so as to predict the heave motion response of the maintenance ship in the next period. The integral constant in formula (14) is a trend term, which can be directly removed when predicting the heave motion response of the maintenance ship.

[0106] With the goal of predicting the heave motion of offshore wind power operation and maintenance ships, the heave motion response of the next period of time is predicted through the measured heave acceleration response data of the operation and maintenance ship in the previous period. The Prony method is used to decompose the measured heave acceleration response, obtain the extreme value and residue of the heave acceleration response, and combine the mathematical relationship between acceleration and displacement to construct the mathematical relationship between the parameters represented by the trigonometric function of the heave motion of the operation and maintenance ship and the extreme value and residue, so as to realize the short-term prediction of the heave motion response of the offshore wind power operation and maintenance ship.

[0107] When implementing, please refer to the table. The hydrodynamic calculation of the maintenance ship generally requires a numerical method. In order not to introduce additional errors, the embodiment adopts a mathematical model with a theoretical solution. The maintenance ship often has geometric symmetry, and its heave degree of freedom is not coupled with other degrees of freedom. Therefore, a single-degree-of-freedom mathematical system is used to analogize the heave degree of freedom motion of the maintenance ship. The motion control equation of this mathematical model is consistent with that of the maintenance ship, and is described by the Cummins equation;

[0108]

[0109] In the formula, M is the mass, M a is the additional mass, K(t) is the delay function, x(t), and are the displacement, velocity and acceleration responses respectively, and f(t) is the external load acting on the system.

[0110] The delay function and additional mass in the Cummins equation represent the radiation effect of the floating body in the water. The delay function characterizes the radiation damping, and it and the speed of the floating body represent the memory efficiency of the ship moving in the water. The delay function of the single-degree-of-freedom system is simulated using the following formula:

[0111] K(t)=3e -0.2t [cos(2t)-0.1sin(2t)] (16)

[0112] The delay function changes with time as shown in the attached figure. Figure 1 As shown in the figure, it can be seen that the delay function is a decay function. As time goes by, the delay function of the system tends to zero.

[0113] The external load acting on the system is simulated using the following formula:

[0114]

[0115] In the formula, C n 、f n and φ n The amplitude, frequency and phase angle of the external load components are listed in the table. The corresponding wave load time history is shown in the attached figure. Figure 2 shown.

[0116] The mass of the system is M = 1, M a =0.5, C=5.5, and the Laplace domain method is used to obtain the displacement and acceleration response of the system. The Prony decomposition of the present invention is used for the acceleration response information of the first 60s to obtain the extreme value and residue of the acceleration response, and then the acceleration response is reconstructed according to the extreme value and residue, and compared with the original value as shown in the figure below. Figure 3 As shown in the figure, the two are consistent, indicating that the obtained extreme value and residue can replace the original acceleration to predict the displacement response. According to the extreme value and residue of the acceleration in the first 60s, the amplitude, frequency, attenuation coefficient and phase angle of each component of the displacement response are estimated by the present invention, and then the displacement response of 60 to 80s is estimated. The obtained results are compared with the theoretical values ​​as shown in the attached figure. Figure 4 As shown in the figure, it can be seen that the two are in good agreement, proving the correctness of the calculation results of the method of the present invention.

[0117] n <![CDATA[f n ]]> <![CDATA[C n ]]> <![CDATA[φ n ]]> 1 1.24 0.52 -π / 12 2 0.76 0.36 π / 3 3 0.24 0.19 π / 6 4 1.46 0.28 -π / 2 5 0.52 0.43 π / 5

[0118] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other principles and basic structures that are the same or similar to those of the present application are within the protection scope of the present application.

Claims

1. A method for predicting the heave motion of an offshore wind power operation and maintenance vessel, characterized in that: A new short-term prediction method for the heave motion of an operation and maintenance ship based on the Porny decomposition of acceleration response includes the following steps: S1, construction of the heave motion response of the maintenance ship; S2, Prony decomposition of heave motion acceleration; S3, heave motion response forecast.

2. A method for predicting the heave motion of an offshore wind power operation and maintenance vessel according to claim 1, characterized in that: The step S1 also includes the following steps: S101, when the offshore wind power operation and maintenance ship is operating, it generates motion response under the action of waves. After reaching a stable state, the motion frequency of the operation and maintenance ship is consistent with the wave frequency, and its heave RAO is: where η a is the wave height of the component with frequency ω in the wave, z a is the amplitude of the ship's heave freedom when the wave frequency is ω; S102, when calculating the heave response according to the ship RAO, we get: Among them, μ m is the mth direction of the wave, a m,n is the amplitude of the nth wave component in the mth direction, ε m,n is the phase of the nth wave component in the mth direction, ε zη (ω n ,μ n ) is the phase difference; S103, combining step S102 to obtain the ship heave response formula: Among them, A n is the response amplitude caused by the nth wave component, φ n The phase of the response caused by the nth wave component.

3. A method for predicting the heave motion of an offshore wind power operation and maintenance vessel according to claim 2, characterized in that: The step S2 further comprises the following steps: S201, using the measured acceleration response to determine the coordinate system, according to step S103, the measured acceleration response data is expressed in exponential form to obtain: Where p is the decomposition order; γ n is the residue, and there is λ n is the extreme value λ n =-α n +iω n ; B n is the amplitude, θ n is the phase angle, α n is the attenuation coefficient, ω n is the frequency; S202, the acceleration data measured by the maintenance ship is a discrete value, let For the discrete acceleration response value y k =y(kΔt), whose Prony decomposition is: in, Δt is the sampling time interval; S203, using a first-order difference equation to replace the formula in step S202, and solving the eigenvalue of the equation, and finally constructing a Hankel matrix to obtain: Where μ and ν are the number of rows and columns of the Hankel matrix respectively; S204, respectively substitute k=0 and k=1 into the formula of step S203, and perform SVD on H(0), so as to use the SVD decomposition of H(0) to represent H(1), and obtain: Among them, U1 and V1 are orthogonal matrices, Σ1 is the diagonal matrix composed of the singular values ​​of H(0), and A is the system matrix; S205, multiply the formula in step S204 by the left and right multiplication The system matrix is ​​obtained as: S205, perform eigenvalue analysis on the system matrix A, and its eigenvalue is z in step S202 n , so that the extreme value of the Prony decomposition in step S202 is: S206, substituting the formula of step S205 into step S202 to obtain the extreme value of the heave acceleration response of the maintenance vessel.

4. A method for predicting the heave motion of an offshore wind power operation and maintenance vessel according to claim 3, characterized in that: The step S3 also includes the following steps: S301, the acceleration response extreme value and residue obtained by Prony decomposition are substituted into the formula of step S201, and the heave acceleration response of the operation and maintenance ship is expressed as a trigonometric function form by Euler formula, and the result is: S302, the acceleration response of the maintenance ship is a real number, and the corresponding extreme value and residue are conjugate complex numbers, so the imaginary parts in the formula of step S301 will cancel each other out. Compared with the formula in step S103, there is the following relationship p=2N, and then the trigonometric function expression of the acceleration of the maintenance ship heave response is obtained as follows: S303, according to Euler's formula, the formula of step S302 is written as follows: S304, integrating the formula in step S303, and obtaining the speed of the ship's heave motion as: in, C1 is the integration constant; S305, integrating the formula in step S304, and obtaining the displacement response of the ship heave motion as: in S306, perform Prony decomposition on the acceleration response data of the heave motion of the maintenance ship in the previous period to obtain the corresponding extreme values ​​and residues, and predict the heave motion response of the maintenance ship in the next period through the extreme values ​​and the amplitude, frequency and phase of the residue calculation formula in step S305. The integral constant in the formula of step S305 is a trend term, which can be directly removed when predicting the heave motion response of the maintenance ship.

Images