An Active Vibration Suppression Method for the Shafting Oscillation of Offshore Permanent Magnet Synchronous Wind Turbines

Abstract

The present invention discloses an active suppression method for shaft system oscillation of an offshore permanent magnet synchronous wind generator, comprising: S1, designing an unknown input observer to online observe the rotational speed of the wind generator and the torsional angle of the drive train under time-varying disturbances; S2, designing a sliding mode controller based on the observation results of the unknown input observer to obtain a compensation torque to control the stability of the torsional angle of the drive train; S3, feeding the compensation torque forward into the vector control of the permanent magnet synchronous wind generator to construct an active suppression system for shaft system oscillation of the permanent magnet synchronous wind generator. The method of the present invention overcomes the deficiencies of the existing methods, such as poor robustness, high complexity, and the need for additional installation of multiple sensors, and effectively suppresses shaft system oscillation under the condition that there are multiple sources of interference in the aerodynamic torque of the permanent magnet synchronous wind generator.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and particularly to an active oscillation suppression method for the shafting of an offshore permanent magnet synchronous wind generator. Background Art

[0002] The continuous increase in the single-unit capacity of offshore wind power and the harsh offshore environment will affect the working life of the transmission chain. Therefore, studying to reduce the adverse effects of vibration and noise on the transmission chain has high academic research and engineering value. At present, domestic and foreign scholars have summarized three types of vibration reduction technologies according to the process of vibration and noise from the generation source to the transmission, namely suppressing the vibration source, optimizing the vibration transmission path, and intervening in the control system.

[0003] The literature (Z. Xu, J. Wei, S. Zhang, Z. Liu, X. Chen, Q. Yan and J. Guo. A state-of-the-art review of the vibration and noise of wind turbine drivetrains[J]. Sustainable Energy Technologies and Assessments, 2021, 48: 1-22) adopted a tuned liquid damper based on liquid sloshing and friction. Experiments have proved that this method effectively enhances the structural damping. However, since the damper is tuned to a certain oscillation frequency, this will limit its application at wide excitation frequencies. The literature (C. Noyes, C. Qin, E. Loth. Pre-aligned downwind rotor for a 13.2MW wind turbine[J]. Renewable Energy, 2018, 116: 749-754) studied the three-point-mounted drivetrain layout, which suppresses the transmission of torque loads in the drivetrain. However, this method is sensitive to non-torque loads. In comparison, the intervention of the control system focuses on reducing vibration and noise through a "software" system rather than a "hardware" system that suppresses the source and optimizes the transmission path. The classical strategy uses a disturbance observer to estimate the target parameters (such as torque deviation and speed deviation). The inherent oscillation components are filtered out by a band-pass filter and used as feedback to generate additional torque (E. Taherian-Far, R. Sahebi, T. Niknam, A. Izadian, M. Shasadeghi. Wind turbine drivetrain technologies[J]. IEEE Transactions on Industry Applications, 2020, 56(2): 1729-1741). However, traditional methods are less robust under a variety of different working conditions, and the corresponding controller parameters must be readjusted to restore good damping performance.)

[0004] From the analysis of existing research results, it can be seen that for the vibration source suppression method based on additional dampers, there are still problems such as the need to add additional equipment and the difficulty in completely suppressing the vibration source; while the method of optimizing the vibration transmission path will make the system sensitive to non-torque loads, and this method usually requires generating applicable damping under strong excitation, which also limits its application in the offshore wind power scenario with irregular strong winds. Moreover, the robustness of the existing control strategies has not reached the best, and it is necessary to install additional sensors or use the torsional angle of the drive train that can only be obtained through multiple calculations as the source for response extraction, which also restricts its application in some low-cost and compact wind turbine scenarios. Therefore, how to design a control strategy with strong robustness, low cost, and excellent performance has become the key to suppressing the shafting oscillation of offshore permanent magnet synchronous wind turbines. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide an active suppression method for the shafting oscillation of offshore permanent magnet synchronous wind turbines, which overcomes the deficiencies of poor robustness, high complexity, and the need for additional installation of sensors in the existing methods, and effectively suppresses the shafting oscillation under the condition of multi-source interference in the aerodynamic torque of the permanent magnet synchronous wind turbine.

[0006] Technical Solution: The active suppression method for the shafting oscillation of the offshore permanent magnet synchronous wind turbine described in the present invention includes the following steps:

[0007] S1. Design an unknown input observer to online observe the rotational speed of the wind turbine and the torsional angle of the drive train under time-varying disturbances;

[0008] S2. Design a sliding mode controller based on the observation results of the unknown input observer to obtain the compensation torque to control the stability of the torsional angle of the drive train;

[0009] S3. Feed forward the compensation torque into the vector control of the permanent magnet synchronous wind turbine to construct an active suppression system for the shafting oscillation of the permanent magnet synchronous wind turbine; including: taking the difference between the given value and the actual value of the rotational speed of the wind turbine obtained according to the maximum wind energy capture principle, and after the error passes through the rotational speed proportional-integral controller, obtaining the given value of the q-axis current of the wind turbine, and superimposing it with the q-axis current compensation component output by the sliding mode controller, and after passing through the current proportional-integral controller, outputting a switching signal to drive the permanent magnet synchronous generator.

[0010] Further, the state space equation of the unknown input observer designed in step S1 is:

[0011]

[0012] Wherein, z is the auxiliary variable, u is the control input, y is the system output, is the time derivative of the auxiliary variable, is the observed value of the state variable, and N, G, L, and H are parameter matrices to be solved.

[0013] Furthermore, the solution methods for the parameter matrices N, G, L, and H of the unknown input observer are as follows:

[0014] The wind turbine drive train model is expressed in the following state equation form:

[0015]

[0016] where x is the state variable of the wind turbine drive train model, is the time derivative of the state variable of the wind turbine drive train model; d is the disturbance amount applied to the aerodynamic torque; A dt , B dt , C dt , D dt are the four parameter matrices in the state equation of the wind turbine drive train model;

[0017] The dynamic equation of the state variable observation error e is:

[0018]

[0019] where, is the time derivative of the state variable observation error, P = I + HC dt is the parameter matrix, and I is the identity matrix;

[0020] The observation error dynamics is independent of the wind turbine drive train system state, control input, and disturbance, and it is obtained that:

[0021]

[0022] G = PB dt

[0023]

[0024] K = L + NH

[0025] The matrices H and G are calculated from the above equations;

[0026] The matrix N needs to satisfy the Hurwitz stability condition. Construct the Lyapunov function V1 = e T Xe, where e T is the transpose of the observation error e, and the matrix X is a positive definite matrix; Differentiate the Lyapunov function V1 to obtain:

[0027]

[0028] where, is the time derivative of V1; T represents the matrix transpose; is the time derivative of eT; the parameter matrix

[0029] By solving the matrix X, the matrices N and L are obtained.

[0030] Furthermore, the wind turbine drive train model is:

[0031]

[0032] where W R , W G , and θ are the wind turbine speed, the wind generator speed, and the drive train twist angle respectively; B t , B g are the self-damping coefficients at the wind turbine end and the wind generator end respectively; J t , J g are the moments of inertia at the wind turbine end and the wind generator end respectively; K dt , B dt are the stiffness coefficient and the damping coefficient of the drive train respectively; η is the transmission efficiency of the drive train, N is the reduction ratio of the drive train; T classical is the aerodynamic torque provided at the wind turbine end, T e is the electromagnetic torque provided at the wind generator end, T disturbance is the disturbance applied to the aerodynamic torque.

[0033] Furthermore, the matrices X, are solved by the LMI toolbox in MATLAB.

[0034] Furthermore, step S2 is specifically as follows:

[0035] When considering the oscillating components, the state space equation of the original system is rewritten as:

[0036]

[0037] where θ is the drive train twist angle, w is the drive train rotational speed, are the oscillating components of θ and w respectively, is the oscillating component of the aerodynamic torque T aero , is the oscillating component of the wind generator electromagnetic torque T e , and J is the equivalent moment of inertia;

[0038] Express the term as the sum of the compensation torque T ecomp and the unmodeled disturbance function , where t is time, specifically:

[0039]

[0040] Design a feedback control law to suppress the rotational speed oscillation of the drive chain caused by unknown disturbances Construct a sliding mode surface where γ is the coefficient of the torsional angle oscillation component of the drive chain; construct a Lyapunov function Taking the derivative of it, we can get:

[0041]

[0042] where is the time derivative of the sliding mode surface s1, is the time derivative of the Lyapunov function V2;

[0043] Let v be an expression to be determined, and the error function is bounded, that is L1 is the upper bound of the absolute value of the error function. Substituting it into the above formula, we get:

[0044]

[0045] Select v = -ρsgn(s1), where ρ is the coefficient of the sign function. When ρ > L1, The compensation torque should be designed as

[0046] Furthermore, step S3 is specifically as follows:

[0047] Use the rotational speed sensor to obtain the rotational speed of the wind turbine, solve the coefficient matrix of the unknown input observer through the LMI toolbox, and observe the rotational speed of the wind generator and the torsional angle of the drive chain based on the unknown input observer;

[0048] Adopt a high-pass filter to extract the oscillation component of the torsional angle of the drive chain. The specific form of the transfer function of the filter is:

[0049]

[0050] where ω n is the cut-off frequency of the high-pass filter, and ζ is the damping coefficient;

[0051] Design the control input of the sliding mode controller as the oscillation component of the torsional angle of the drive chain The control output is the q-axis current compensation component i qcomp * of the wind generator. Superimpose it on the given value of the current control loop of the wind generator, and combine it with the vector control unit of the wind generator to jointly form an active suppression system for the shafting oscillation of the permanent magnet synchronous wind generator.

[0052] An active suppression system for shaft oscillation of an offshore permanent magnet synchronous wind turbine corresponding to the above method, comprising:

[0053] An on-line observation unit for designing an unknown input observer to on-line observe the rotational speed of the wind turbine and the torsional angle of the drive train under time-varying disturbances;

[0054] A compensation torque calculation unit for designing a sliding mode controller based on the observation results of the unknown input observer to calculate the compensation torque to control the stability of the torsional angle of the drive train;

[0055] A control unit for feeding the compensation torque forward into the vector control of the permanent magnet synchronous wind turbine to construct an active suppression system for shaft oscillation of the permanent magnet synchronous wind turbine; including: taking the difference between the given value and the actual value of the wind turbine rotational speed obtained according to the maximum wind energy capture principle, the error passes through a speed proportional-integral controller to obtain the given value of the q-axis current of the wind turbine, and is superimposed with the q-axis current compensation component output by the sliding mode controller, and after passing through a current proportional-integral controller, outputs a switching signal to drive the permanent magnet synchronous generator.

[0056] An electronic device for storing and executing the above method, the device comprising:

[0057] A memory storing executable program code;

[0058] A processor coupled to the memory;

[0059] The processor calls the executable program code stored in the memory to execute the steps of the above-mentioned active suppression method for shaft oscillation of an offshore permanent magnet synchronous wind turbine.

[0060] A computer-readable storage medium for storing and executing the above method, the computer-readable storage medium stores computer instructions, and when the computer instructions are called, they are used to execute the steps of the above-mentioned active suppression method for shaft oscillation of an offshore permanent magnet synchronous wind turbine.

[0061] Advantageous effects: Compared with the prior art, the remarkable technical effects of the present invention are: (1) The control scheme has good robustness. Under the condition of applying interference, the unknown input observer can still accurately observe the system state variables, and the sliding mode controller can effectively improve the transient performance and steady-state performance of the system and suppress shaft oscillation; (2) The control scheme has a simple control architecture, without complex calculation processes, and is more convenient to execute in the digital microprocessors commonly used in actual offshore permanent magnet synchronous wind turbine control systems; (3) The control scheme does not require an electromagnetic torque sensor, only needs to use a speed sensor to extract the real-time rotational speed of the wind turbine, and can realize the active suppression of shaft oscillation without increasing the system software and hardware costs. Description of the Drawings

[0062] Figure 1It is the flow chart of the method of the present invention;

[0063] Figure 2 It is the structural block diagram of the active oscillation suppression system of the shafting of the present invention;

[0064] Figure 3 It is the simulation experiment result of the system state estimation of the unknown input observer without external disturbance; among them, (a) is the simulation curve of the wind turbine speed, (b) is the simulation curve of the wind turbine generator speed, (c) is the simulation curve of the torsional angle of the drive train; (d) is the simulation curve of the observation error of the wind turbine speed; (e) is the simulation curve of the observation error of the wind turbine generator speed; (f) is the simulation curve of the observation error of the torsional angle of the drive train;

[0065] Figure 4 It is the simulation experiment result of the system state estimation of the unknown input observer under external disturbance; among them, (a) is the simulation curve of the wind turbine speed, (b) is the simulation curve of the wind turbine generator speed, (c) is the simulation curve of the torsional angle of the drive train; (d) is the simulation curve of the observation error of the wind turbine speed; (e) is the simulation curve of the observation error of the wind turbine generator speed; (f) is the simulation curve of the observation error of the torsional angle of the drive train;

[0066] Figure 5 It is the simulation experiment result of the control effect of the sliding mode controller; among them, (a) is the simulation curve of the wind turbine speed, (b) is the simulation curve of the wind turbine generator speed, (c) is the simulation curve of the torsional angle of the drive train. Specific implementation mode

[0067] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0068] As Figure 1 shown, an active oscillation suppression method for the shafting of an offshore permanent magnet synchronous wind turbine of the present invention includes the following steps:

[0069] S1. Design an unknown input observer (UIO) to online observe the wind turbine generator speed and the torsional angle of the drive train under time-varying disturbance when only the wind turbine speed is known; including:

[0070] Consider the following wind turbine drive train model:

[0071]

[0072] Among them, w R 、w G 、θ are the wind turbine speed, the wind turbine generator speed, and the torsional angle of the drive train respectively; are the time derivatives of the wind turbine speed, the time derivative of the wind turbine generator speed, and the time derivative of the torsional angle of the drive train respectively; B t 、Bg are the self-damping coefficients at the wind turbine end and the wind power generator end respectively; J t and J g are the moments of inertia at the wind turbine end and the wind power generator end respectively; K dt and B dt are the stiffness coefficient and the damping coefficient of the drive train respectively; η is the transmission efficiency of the drive train, N is the reduction ratio of the drive train; T classical is the aerodynamic torque provided at the wind turbine end, T e is the electromagnetic torque provided at the wind power generator end, T disturbance is the disturbance applied to the aerodynamic torque.

[0073] The wind power generator drive train model is expressed in the following state equation form:

[0074]

[0075] where x is the state variable of the wind power generator drive train model, is the time derivative of the state variable of the wind power generator drive train model; y is the system output, u is the control input; the four parameter matrices in the state equation of the wind power generator drive train model can be expressed as C dt = [1 0 0], d is the vector form of the disturbance applied to the aerodynamic torque.

[0076] The UIO state space equation is designed as follows:

[0077]

[0078] where z is the auxiliary variable, is the time derivative of the auxiliary variable, is the observed value of the state variable, N, G, L, H are the parameter matrices to be solved.

[0079] According to Equation (2) and Equation (3), the observation error e is obtained as:

[0080]

[0081] where I is the identity matrix, P = I + HC dt is the parameter matrix.

[0082] Differentiating Equation (4), the dynamic equation of the observation error is obtained as:

[0083]

[0084] where, is the time derivative of the observation error.

[0085] The observation error dynamics is independent of the state of the wind turbine drive train system, control inputs, and disturbances. Therefore, it can be concluded that:

[0086]

[0087] The matrix parameter matrices H and G are calculated from the above equation. It can be seen from formula (5) that the matrix N needs to satisfy the Hurwitz stability condition. To accurately calculate the matrices N and L, a Lyapunov function V1 is constructed as:

[0088] V1 = e T Xe (7)

[0089] where the matrix X is a positive definite matrix, and e T is the transpose of the observation error e. Taking the derivative of the Lyapunov function V1, we get:

[0090]

[0091] where is the time derivative of V1; T represents the matrix transpose; is the time derivative of e T ; the parameter matrix

[0092] By solving the following linear matrix inequality through the LMI toolbox in MATLAB, the matrix X can be obtained

[0093] where α is the upper limit of the values of the elements of the matrix to be designed. After solving the matrices X and , the matrices N and L can be solved through formula (6).

[0094] So far, all the matrices N, G, L, and H required for the UIO design have been solved.

[0095] S2. Design a sliding mode controller (SMC) based on the observation results of the unknown input observer to obtain the compensation torque to control the stability of the drive train twist angle; specifically:

[0096] When considering the shaft oscillation component, the state space equation of the wind turbine drive train system is rewritten as:

[0097]

[0098] where are the oscillation components of θ and w respectively, w is the time derivative of the drive train twist angle, that is, the drive train speed. is the aerodynamic torque T aeroThe oscillating component, is the electromagnetic torque T of the wind turbine e 's oscillating component; J is the equivalent moment of inertia.

[0099] Express the term as the sum of the compensation torque T ecomp and the unmodeled disturbance function , where t is time, specifically:

[0100]

[0101] Design a feedback control law to suppress the oscillating component of the drive train speed caused by unknown disturbances Construct the sliding surface s1 as

[0102]

[0103] where γ is the coefficient of the oscillating component of the drive train torsional angle; Differentiating the sliding surface s1 gives:

[0104]

[0105] where is the time derivative of the sliding surface. Construct the Lyapunov function V2

[0106]

[0107] Differentiating it gives:

[0108]

[0109] where is the time derivative of V2. Let v be the expression to be determined, and the error function is bounded, that is L1 is the upper limit of the absolute value of the error function. Substituting into the above equation gives:

[0110]

[0111] Select v = -ρsgn(s1), where ρ is the coefficient of the sign function. When ρ > L1, Therefore, the compensation torque should be designed as

[0112] S3. Feed the compensation torque forward into the vector control of the permanent magnet synchronous wind generator to construct an active suppression system for the shafting oscillation of the permanent magnet synchronous wind generator, including: taking the difference between the given value and the actual value of the wind turbine speed obtained according to the maximum wind energy capture principle, and after the error passes through the speed proportional-integral controller, obtaining the given value of the q-axis current of the wind generator, and superimposing it with the q-axis current compensation component output by the sliding mode controller. After passing through the current proportional-integral controller, output a switching signal to drive the permanent magnet synchronous generator.

[0113] The active suppression system for the shafting oscillation of the permanent magnet synchronous wind generator is as Figure 2 shown. According to the maximum power point tracking (MPPT) principle, this system obtains the optimal given value of the wind turbine speed at the current wind speed and obtains the actual value of the wind turbine speed through a speed sensor, thereby obtaining the deviation value from the target. Pass this value through a speed proportional-integral (PI) controller to obtain the given value i of the q-axis current of the wind generator q * , and control the q-axis current i of the wind generator through the current loop q , thereby controlling the electromagnetic torque T of the wind generator e , and further controlling the wind turbine speed w R . To suppress the shafting oscillation of the wind generator, this system uses an unknown input observer (UIO) to observe the torsional angle θ of the drive train, and uses a high-pass filter (HPF) to extract the oscillation component of the torsional angle of the drive train Design a suitable q-axis current compensation component i of the wind generator by using a sliding mode controller (SMC) qcomp * , thereby changing the electromagnetic torque of the wind generator and further suppressing the oscillation of the drive train system; specifically:

[0114] Obtain the wind turbine speed through a speed sensor, solve the coefficient matrix of the unknown input observer through the LMI toolbox, and observe the wind generator speed and the torsional angle of the drive train based on the unknown input observer.

[0115] Adopt a high-pass filter (HPF) to extract the oscillation component of the torsional angle θ of the drive train. The specific form of the transfer function of this filter is:

[0116]

[0117] where the cut-off frequency ω of the high-pass filter n is set to 3 Hz, and the damping coefficient ζ is set to 0.707 to filter out the main DC component of the torsional angle of the drive train.

[0118] The control input of the sliding mode controller is the oscillation component of the torsional angle of the drive train and the control output is the q-axis current compensation component i of the wind generator qcomp* , it is superimposed on the given value of the current control loop of the wind turbine, and combined with the vector control algorithm of the wind turbine to jointly form an active suppression system for the shafting oscillation of the permanent magnet synchronous wind turbine.

[0119] An active suppression system for the shafting oscillation of an offshore permanent magnet synchronous wind turbine corresponding to the above method of the present invention includes:

[0120] An on-line observation unit for designing an unknown input observer to on-line observe the rotational speed of the wind turbine and the torsional angle of the drive train under time-varying disturbances;

[0121] A compensation torque calculation unit for designing a sliding mode controller based on the observation results of the unknown input observer to calculate the compensation torque to control the stability of the torsional angle of the drive train;

[0122] A control unit for feeding the compensation torque forward to the vector control of the permanent magnet synchronous wind turbine to construct an active suppression system for the shafting oscillation of the permanent magnet synchronous wind turbine; including: taking the difference between the given value and the actual value of the wind turbine rotational speed obtained according to the maximum wind energy capture principle, and after the error passes through the rotational speed proportional integral controller, obtaining the given value of the q-axis current of the wind turbine, and superimposing it with the q-axis current compensation component output by the sliding mode controller, and after passing through the current proportional integral controller, outputting a switching signal to drive the permanent magnet synchronous generator.

[0123] An electronic device for storing and executing the above method, the device includes:

[0124] A memory storing executable program code;

[0125] A processor coupled to the memory;

[0126] The processor calls the executable program code stored in the memory and executes the steps of the active suppression method for the shafting oscillation of the offshore permanent magnet synchronous wind turbine.

[0127] A computer-readable storage medium for storing and executing the above method, the computer-readable storage medium stores computer instructions, and when the computer instructions are called, they are used to execute the steps of the active suppression method for the shafting oscillation of the offshore permanent magnet synchronous wind turbine.

[0128] Next, the effectiveness of an active suppression method for the shafting oscillation of an offshore permanent magnet synchronous wind turbine proposed by the present invention is verified through MATLAB / Simulink simulation experiments and the simulation experiment results are given;

[0129] To more clearly show the proposed control method, the parameters of the wind turbine, drive train and 300kW permanent magnet synchronous wind turbine selected in the simulation experiment are as follows:

[0130] ① Parameters of the wind turbine: impeller radius 14 m, air density 1.2 kg / m 3 ;

[0131] ② Parameters of the drive train: moment of inertia on the low-speed side 1800 kgm 2 , moment of inertia on the high-speed side 600 kgm 2 , stiffness coefficient of the drive train 100000 Nm / rad, damping coefficient of the drive train 0 Nms / rad, self-damping on the low-speed side 0 Nms / rad, self-damping on the high-speed side 0 Nms / rad, reduction ratio 1;

[0132] ③ Parameters of the generator: number of pole pairs 12, stator resistance 0.025 Ω, d-axis inductance 3.6 mH, q-axis inductance 3.6 mH, permanent magnet flux linkage 3.89 Wb, DC bus voltage 1.8 kV.

[0133] In the simulation experiment, the given wind speed is 12 m / s, and the specific form of the disturbance is to add a negative triangular spike with a maximum amplitude of -10000 Nm and a period of 0.03 s in T classical . The observation results of the unknown input observer without disturbance and with disturbance are shown in (a)–(f) in Figure 3 and (a)–(f) in Figure 4 respectively. The simulation experiment results confirm that the unknown input observer can achieve rapid convergence of the observed value, and its observation error is within 2×10 -4 rad, with excellent observation performance. The control effect of the sliding mode controller is shown in (a), (b), (c) in Figure 5 . It can be seen from the figure that although adding SMC will generate a small amplitude chattering in the steady-state speed of the motor, the oscillation amplitude of the drive train torsion angle is effectively attenuated compared with that without control. This proves that the proposed SMC realizes the improvement of the steady-state performance of the system. In addition, the adjustment time of the system without any control is about 3.5 s, while the adjustment time of the system after adding SMC control is about 2.6 s. This proves that the proposed SMC improves the transient performance of the system. In summary, the unknown input observer designed in the present invention can accurately observe the rotational speed and the drive train torsion angle, and the designed sliding mode controller can effectively improve the transient and steady-state performance of the wind power generation system and suppress the torsion vibration of the drive train of the permanent magnet synchronous wind turbine.

Claims

1. An active oscillation suppression method for the shafting of an offshore permanent magnet synchronous wind generator, characterized in that, It includes the following steps: S1. Design an unknown input observer to online observe the rotational speed of the wind turbine and the torsional angle of the drive train under time-varying disturbances. S2. Design a sliding mode controller based on the observation results of the unknown input observer to obtain the compensation torque to control the stability of the torsional angle of the drive train. Specifically: When considering the oscillation component, the state space equation of the original system is rewritten as: where θ is the torsional angle of the drive chain, w is the rotational speed of the drive chain, are the oscillating components of θ and w respectively, is the oscillating component of the pneumatic torque T aero and is the oscillating component of the electromagnetic torque T e of the wind turbine, and J is the equivalent moment of inertia; Express the term as the compensation torque T ecomp and the unmodeled disturbance function as the sum, where t is time, specifically as follows: Design a feedback control law to suppress the rotational speed oscillation of the transmission chain caused by unknown disturbances Construct a sliding mode surface where γ is the coefficient of the torsional angle oscillation component of the transmission chain; construct a Lyapunov function Taking the derivative of it, we can get: where, is the time derivative of the sliding surface s1, is the time derivative of the Lyapunov function V2; Let v be the expression to be determined, and the error function is bounded, that is Let L1 be the upper bound of the absolute value of the error function. Substituting it into the above equation, we get: Select \(v = -\rho\mathrm{sgn}(s_1)\), where \(\rho\) is the coefficient of the sign function. When \(\rho>L_1\), the compensating torque should be designed as S3. Feed forward the compensation torque into the vector control of the permanent magnet synchronous wind turbine to construct an active oscillation suppression system for the shafting of the permanent magnet synchronous wind turbine, including: taking the difference between the given value and the actual value of the wind turbine rotational speed obtained according to the maximum wind energy capture principle, the error passes through a speed proportional integral controller to obtain the given value of the q-axis current of the wind turbine, and is superimposed with the q-axis current compensation component output by the sliding mode controller, and after passing through a current proportional integral controller, outputs a switching signal to drive the permanent magnet synchronous generator.

2. The active oscillation suppression method for the shafting of an offshore permanent magnet synchronous wind turbine according to claim 1, wherein The state space equation of the unknown input observer designed in step S1 is: where z is an auxiliary variable, u is the control input, and y is the system output. is the time derivative of the auxiliary variable. is the observed value of the state variable, and N, G, L, and H are parameter matrices to be solved.

3. A method for actively suppressing the shaft oscillation of an offshore permanent magnet synchronous wind generator according to claim 2, characterized in that, The solution methods for the parameter matrices N, G, L, and H of the unknown input observer are: The wind turbine drive train model is expressed in the following state equation form: where x is the state variable of the wind turbine drivetrain model, is the time derivative of the state variable of the wind turbine drivetrain model; d is the disturbance amount applied to the aerodynamic torque; A dt 、B dt 、C dt 、D dt are four parameter matrices in the state equation of the wind turbine drivetrain model; The dynamic equation of the state variable observation error e is: wherein, is the time derivative of the state variable observation error, P = I + HC dt is the parameter matrix, and I is the identity matrix; The dynamic of the observation error has nothing to do with the state of the wind turbine drive train system, the control input, and the disturbance, and it is obtained that: G = PB dt K = L + NH Calculate the matrices H and G from the above formula; The matrix N needs to satisfy the Hurwitz stability condition, and construct the Lyapunov function V1 = e T Xe, where e T is the transpose of the observation error e, and the matrix X is a positive definite matrix; take the derivative of the Lyapunov function V1 to obtain: wherein, is the time derivative of V1; T represents matrix transpose; is the time derivative of e T ; the parameter matrix By solving matrix X, matrix N and L are obtained.

4. A method for actively suppressing shaft system oscillation of an offshore permanent magnet synchronous wind generator according to claim 3, characterized in that, The wind turbine drive train model is: where, w R , w G , θ are the wind turbine speed, the wind generator speed, and the drive train torsional angle respectively; B t , B g are the self-damping coefficients at the wind turbine end and the wind generator end respectively; J t , J g are the moments of inertia at the wind turbine end and the wind generator end respectively; K dt , B dt are the stiffness coefficient and the damping coefficient of the drive train respectively; η is the transmission efficiency of the drive train, N is the drive train reduction ratio; T classical is the aerodynamic torque provided at the wind turbine end, T e is the electromagnetic torque provided at the wind generator end, T disturbance is the disturbance applied to the aerodynamic torque.

5. A method for actively suppressing the shaft system oscillation of an offshore permanent magnet synchronous wind turbine according to claim 3, characterized in that Matrix X, is solved by the LMI toolbox in MATLAB.

6. The active oscillation suppression method for the shafting of an offshore permanent magnet synchronous wind turbine according to claim 1, wherein Step S3 is specifically: Use a rotational speed sensor to obtain the rotational speed of the wind turbine, solve the coefficient matrix of the unknown input observer through the LMI toolbox, and observe the rotational speed of the wind turbine and the torsional angle of the drive train based on the unknown input observer. Adopt a high-pass filter to extract the oscillation component of the torsional angle of the drive train, and the specific form of the transfer function of the filter is: where ω n is the cut-off frequency of the high-pass filter, and ζ is the damping coefficient; The control input of the designed sliding mode controller is the oscillation component of the torsional angle of the drive chain The control output is the q-axis current compensation component i of the wind turbine qcomp * , which is superimposed on the given value of the current control loop of the wind turbine. Combining with the vector control unit of the wind turbine, they jointly form an active oscillation suppression system for the shafting of the permanent magnet synchronous wind turbine.

7. An active oscillation suppression system for the shafting of an offshore permanent magnet synchronous wind turbine, characterized in that, It includes: An online observation unit for designing an unknown input observer to online observe the rotational speed of the wind turbine and the torsional angle of the drive train under time-varying disturbances. A compensation torque calculation unit for designing a sliding mode controller based on the observation results of the unknown input observer to obtain the compensation torque to control the stability of the torsional angle of the drive train. Specifically: When considering the oscillation component, the state space equation of the original system is rewritten as: where θ is the torsional angle of the drive chain, w is the rotational speed of the drive chain, are the oscillating components of θ and w respectively, is the oscillating component of the pneumatic torque T aero and is the oscillating component of the electromagnetic torque T e of the wind turbine, and J is the equivalent moment of inertia; Express the term as the compensation torque T ecomp and the unmodeled disturbance function as the sum, where t is time, specifically: Design a feedback control law to suppress the rotational speed oscillation of the transmission chain caused by unknown disturbances Construct a sliding mode surface where γ is the coefficient of the torsional angle oscillation component of the transmission chain; construct a Lyapunov function Taking the derivative of it, we can get: wherein, is the time derivative of the sliding mode surface s1, is the time derivative of the Lyapunov function V2; Let v be the expression to be determined, and the error function is bounded, that is Let L1 be the upper bound of the absolute value of the error function. Substituting it into the above equation, we get: Select \(v = -\rho\mathrm{sgn}(s_1)\), where \(\rho\) is the coefficient of the sign function. When \(\rho>L_1\), the compensating torque should be designed as A control unit for constructing an active oscillation suppression system for the shafting of the permanent magnet synchronous wind turbine and performing vector control on the permanent magnet synchronous wind turbine, including: taking the difference between the given value and the actual value of the wind turbine rotational speed obtained according to the maximum wind energy capture principle, the error passes through a speed proportional integral controller to obtain the given value of the q-axis current of the wind turbine, and is superimposed with the q-axis current compensation component output by the sliding mode controller, and after passing through a current proportional integral controller, outputs a switching signal to drive the permanent magnet synchronous generator.

8. An electronic device, characterized in that, The device includes: A memory storing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory and executes the steps of the active oscillation suppression method for the shafting of the offshore permanent magnet synchronous wind turbine according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions, which are used to execute the steps of the active oscillation suppression method for the shafting of the offshore permanent magnet synchronous wind turbine according to any one of claims 1-6 when called.

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