Wind power installation vessel lifting platform stability control method and system based on virtual main shaft

Abstract

The invention discloses a wind power installation vessel lifting platform stability control method and system based on a virtual main axis. The method comprises the steps that the total disturbance borne by four pile legs of a lifting platform is calculated; performing unbiased estimation on the total disturbance obtained by calculation to obtain disturbance estimation data; performing pre-compensation on the system by using disturbance estimation data; designing an anti-disturbance controller to adjust the response speed of the system; current distribution is conducted on the pile legs according to the disturbance values; calculating a rotating speed error corresponding to the pile leg based on the distributed pile leg current; for rotating speed errors, current feedback compensation is carried out through a designed current compensator to reduce the errors, and stable control over the lifting platform is achieved. The linear active-disturbance-rejection controller and the rotating speed / current distribution model are matched to complete platform control, and the system has good rapidity and anti-interference performance.

Description

Technical Field

[0001] The present invention belongs to the field of marine engineering and green energy technology, and relates to the control of a wind power installation vessel lifting platform, and specifically to a method and system for stabilizing the wind power installation vessel lifting platform based on a virtual main axis. Background Art

[0002] Compared with simply realizing electric propulsion of multiple motors, realizing motion compensation of multiple motors, that is, preset dynamic control such as attitude control of wind power installation ships, has higher stability requirements for the control system. For the working conditions of wind power ships, the traditional mechanical synchronization mode is difficult to achieve and has no practical value. The electric synchronization method does not require mechanical components, but only analyzes the characteristics of the controlled object and adopts the corresponding coupling control strategy to improve the synchronization of multiple motors.

[0003] There are many methods for implementing multi-motor coordinated control, such as:

[0004] (1) Cross-coupling structure. The cross-coupling control structure is a synchronous control strategy for dual motors. The basic idea is to compare the speed and position of two adjacent motors, input their difference into the controller, and track the feedback of the motor. Its feature is that it can respond to the load changes of any motor. This method is introduced to solve the problem of high precision and high dynamic response of the magnetic levitation system by studying the dynamic characteristics of the magnetic levitation system. However, due to the use of cross-coupling, the feedback of more than two motors is solved, so it is not suitable for the case of multiple motors.

[0005] (2) Deviation coupling structure: By weighting the synchronization errors of multiple motors and feeding them back to the controllers of each motor, the synchronization of multiple motors is achieved, and coordinated control and tracking decoupling of multiple motors are achieved. However, since the speed compensation of each motor requires the synchronization errors of other motors, there are problems such as complex calculations and large amount of calculations. In addition, deviation coupling can also cause saturation failure of the controller during startup. Summary of the invention

[0006] Purpose of the invention: In order to overcome the shortcomings of the prior art, a method and system for stabilizing the lifting platform of a wind power installation ship based on a virtual main axis is provided. The control system has multiple modules, which can be combined to complete the stabilization control of the entire wind power installation ship platform. At the same time, a linear anti-disturbance controller is designed to cope with underwater environmental interference, and cooperates with the control system to complete the control of the platform.

[0007] Technical solution: To achieve the above purpose, the present invention provides a method for stabilizing the lifting platform of a wind power installation vessel based on a virtual main axis, comprising the following steps:

[0008] S1: Calculate the total disturbance on the four legs of the lifting platform;

[0009] S2: Make an unbiased estimate of the calculated total disturbance to obtain disturbance estimation data;

[0010] S3: Use the disturbance estimation data to pre-compensate the system;

[0011] S4: Design an anti-disturbance controller to adjust the system response speed;

[0012] S5: Distribute current to the pile legs according to the disturbance value;

[0013] S6: Calculate the speed error corresponding to the pile leg based on the allocated pile leg current;

[0014] S7: For the speed error, the current feedback compensation is performed through the designed current compensator to reduce the error and achieve stable control of the lifting platform.

[0015] Furthermore, the calculation method of the total disturbance received by the four legs of the lifting platform in step S1 is:

[0016] The system equations with uncertain interference are obtained as follows:

[0017]

[0018] Where: f w is the external disturbance, where W1, W2, W3, and W4 are the disturbances caused by different soil properties when the four pile legs are inserted into the seabed, and T Li is the feedback torque from the motion axis, J is the main axis moment of inertia; f n is the internal disturbance, where N1, N2, N3, and N4 are the internal disturbances caused by the mismatch of the mathematical models of the four pile legs; Δu is the disturbance caused by parameter perturbation, and b1, b2, b3, and b4 are the actual parameters of the four pile legs;

[0019] The total disturbance of the system is defined as

[0020]

[0021] And the above disturbance is extended to the system space state equation, and we get:

[0022]

[0023] In the formula: x=[ω1f1ω2f2ω3f3ω4f4] T ;

[0024]

[0025] Furthermore, the method for unbiased estimation of the total disturbance in step S2 is:

[0026] Based on the system spatial state variables shown in formula (2), a linear extended observer LEO is constructed, which is expressed as

[0027]

[0028] In the formula is the state variable of LEO, where are the estimated values ​​of ω1, ω2, ω3, and ω4 respectively, are the estimated values ​​of f1, f2, f3, and f4 respectively; is the gain matrix of LEO.

[0029] Furthermore, in step S3, when the observer converges stably, f1→f2; therefore, Substituting f1 and f2 in the pile leg control system respectively, we have

[0030]

[0031] According to the linear active disturbance rejection control theory, the disturbance estimated by LEO is used to pre-compensate the system to eliminate the influence of the disturbance on the pile-leg control system.

[0032] Furthermore, the step S4 is specifically as follows:

[0033] The expression of the four-leg control rate is as follows:

[0034]

[0035] Where: K p is the proportionality coefficient; ω ref is the reference speed;

[0036] From equations (4) to (5), we can get the linear active disturbance rejection controller structure of the four-leg control system, which can stabilize the system and adjust the dynamic response speed of the system.

[0037] The subsequent current loop controller is based on i d = 0 control strategy, implemented using PI controller, in the form of

[0038]

[0039] Where: K pd , K pq is the proportionality coefficient; K id , K iq is the integral coefficient; its parameters can be adjusted by the internal model method.

[0040] Furthermore, the current distribution method in step S5 is:

[0041] The collaborative compensator adopts a virtual main axis structure to achieve the coordinated control of the four pile legs. When the pile leg 1 suddenly sinks, its expression is:

[0042]

[0043] Where: i qc1 、i qc2 、i qc3 、i qc4 is the q-axis given current after coupling coefficient compensation; K is the q-axis reference current output by the speed controller after limiting; c is the coupling coefficient; when leg 1 suddenly sinks, the system calculates the current given to leg 1 based on the pressure difference between leg 1 and the other legs. At the same time, the currents of the other legs are 0, causing them to stop rising and falling;

[0044] When the pile leg 1 is compacted, its expression is

[0045]

[0046] When pile legs 1 and 2 are compacted, the expression is:

[0047]

[0048] When the four pile legs are not disturbed, the speed of the four pile legs does not change, that is, ω1=ω2=ω ref ; From formula (8), we can know that K c (ω1-ω2)=0, at this time, the virtual spindle cooperative controller has no effect on the system; when one of the pile legs is disturbed, ω1≠ω2. It can be seen from formulas (8)-(10) that after the speed difference is coordinated and controlled, the respective feedforward compensation parts are superimposed on the q-axis currents of the four piles, thereby adjusting the output torque of the four piles to achieve the stability of the platform; the coupling coefficient is a coefficient that amplifies the two speed differences. If its value is too large, it will cause the system's speed oscillation or even instability.

[0049] Furthermore, the method for calculating the rotation speed error of the first leg in step S6 is:

[0050] The speed error compensation feedback module corresponding to the first pile leg is established, and the speed error calculation formula of the first pile leg is obtained as follows:

[0051] e1=K 12 (n1-n2)+K 13 (n1-n3)+K 14(n1-n4)+K2[(nK1-(n1+n2+n3+n4)](11)

[0052] Where n, n1, n2, n3, n4 represent the input speed and the feedback speed of motor 1, 2, 3, 4 respectively; K 12 , K 13 , K 14 They respectively represent the feedback gain of the synchronization error between leg 1 and the other legs; K1 represents the gain multiple of the input speed, which is determined by the number of motors; K2 represents the overall gain of the difference between the input speed after gain and the feedback speed of the four motors of the entire steering system; e1 represents the final error output of the first speed compensation feedback module.

[0053] Furthermore, the design and operation analysis method of the current compensator in step S7 is:

[0054] When the four pile legs operate normally without disturbance, ΔT r1 =ΔT r2 =ΔT r3 =ΔT r4 =0, n1=n2=n3=n4=n r ,i qf1 =i qf2 =i qf3 =i qf4 =0, the speed difference of the four legs is 0, and the current feedback compensator does not work at this time;

[0055] Taking one of the pile legs as an example, when the system is running stably, the speed signal maintains n1=n2=n3=n4=n r ; When t = t0, load disturbance ΔT r1 Start interfering, at time t0 there is T e1 -(T r1 +ΔT r1 ) <T e2 -T r2 , which results in the desired speed n1 * <n2 * ; At t = t1 (t1>t0), the error between the four legs Δn (Δn = |n1-n p |) reaches the maximum, indicating that the pressure difference between this leg and the other legs is the largest at this time. At this time, the coupling coefficient K is set. After experiencing the gain effect of this coefficient, Δn generates the corresponding current compensation signal i qf1, and feeds it back to the current loop of the motor. Finally, due to the current loop inside the motor, the output speed signal n1 of the motor shaft continuously approaches the given value. At the same time, the second, third and fourth legs also approach the set values ​​synchronously with the signal n1 through the corresponding adjustment mechanism, so that the speeds of the four legs gradually tend to be consistent during the adjustment process, thereby achieving recoverability to external interference.

[0056] Furthermore, the method for determining the value range of the coupling coefficient K in step S7 is:

[0057] The coupling coefficient K determines the control effect of current feedback compensation to a certain extent; if the value of K is too small, it will cause rapid adjustment of the system, and when the value of K is too small, it will cause rapid adjustment of the system, thereby causing speed oscillation. Therefore, the present invention proposes a range of K values ​​that can ensure the synchronization characteristics of the system. Assume that n p =an1,T r1 +ΔT r1 =bT e1 , then when leg 1 is subjected to load disturbance, we can get the input i qr1 The transfer function from n1(s) to the output n1(s) is

[0058]

[0059] Where p is the pole pair number; ψ f is the cross-linked magnetic flux; J is the moment of inertia; B is the friction coefficient;

[0060] If the control link needs to remain relatively stable, then the left half plane of the s plane must correspond to the characteristic root of the transfer function, so we get

[0061]

[0062] It can be seen from formula (13) that the internal parameters of the motor and the amplitude of the load disturbance to the motor affect K. From the perspective of engineering practicality, based on a real motor prototype, it can be known that as K increases, the synchronization of the system will gradually improve.

[0063] The present invention also provides a wind power installation ship lifting platform stability control system based on a virtual spindle, comprising a virtual spindle collaborative control module, a current feedback compensator module and a multi-motor system module;

[0064] The virtual spindle collaborative control module is used to calculate the total disturbance P of the four pile legs. di The different current values ​​assigned to each leg are determined to assign different angular velocities ω to each leg. m ;

[0065] The current feedback compensator module calculates the error between the rotation speed of each leg and the other three legs to obtain the ω ei Get more accurate speed distribution to multi-motor system modules through current feedback compensation;

[0066] The multi-motor system module controls the lifting platform through the motor according to the rotation speed after current feedback compensation.

[0067] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0068] ① From the comparison of the two current mainstream solutions, it can be seen that the virtual spindle control method of the present invention adopts virtual torque calculation to feedback load changes, which can improve efficiency and reduce costs. Moreover, because the virtual spindle was used in the early stage, its feedback structure is relatively mature, so when the number of motors is large, the amount of calculation during feedback can be reduced.

[0069] ② Similar to the Celluveyor transmission system, the lifting platform attitude stability control design based on the virtual spindle in the present invention is also a modular system, and the overall system is easy to quickly and easily maintain.

[0070] ③Compared with the traditional virtual spindle control method, the present invention adopts a design combining the virtual spindle with the deviation coupling control method. Due to the influence of various factors such as load, working conditions and communication, multiple motors will have synchronization problems to varying degrees. The present invention couples the speed of each motor and reduces the speed error between each motor through speed error compensation, thereby achieving mutual speed restriction of each motor. Therefore, this design can quickly complete dynamic speed compensation.

[0071] ④The linear anti-disturbance controller cooperates with the speed / current distribution model to complete the control of the platform, and the system has good rapidity and anti-interference performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 The platform structure and sensor layout diagram for the wind power installation vessel;

[0073] Figure 2 This is the platform posture diagram when the pile legs sink;

[0074] Figure 3 It is a schematic diagram of the principle of platform stability control strategy based on virtual spindle;

[0075] Figure 4 is the disturbance distribution diagram of the four pile legs;

[0076] Figure 5 This is the speed error compensation feedback module diagram of the first pile leg;

[0077] Figure 6This is the structural diagram of the current feedback compensator of motor 1. DETAILED DESCRIPTION

[0078] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0079] like Figure 1 As shown, the sensors are arranged on the lifting platform of the wind power installation ship. The lifting platform is supported by four pile legs. The height of the four pile legs is adjusted to make the platform horizontally stable. XYZ and X0Y0Z0 coordinate systems are established at the center point of the platform, where XYZ is the platform coordinate system, which is a fixed coordinate system, and X0Y0Z0 is the horizontal coordinate system, which is a dynamic coordinate system. An attitude sensor is placed at each of the four corners and the center of the platform, an inclination sensor is installed at each of the four corners of the bottom of the platform, a displacement sensor is installed at each of the four pile legs, and a pressure sensor is installed at the bottom of each of the four pile legs.

[0080] like Figure 2 As shown in the figure, when an offshore platform encounters a layered foundation with a hard upper layer and a soft lower layer, its bearing capacity mainly depends on the soft soil below it, and is related to its thickness and the relative strength of the upper and lower layers. If its bearing capacity is insufficient, the pile shoe will break through the hard layer and suddenly sink, causing it to tilt sharply, or even a dangerous accident in which the pile foot or lifting equipment is seriously damaged.

[0081] In view of the above problems, the present invention takes the wind power installation vessel as the research object, builds a platform stability control system and control strategy based on the virtual main axis, and the control system structure block diagram is shown in Figure 3 The wind power installation ship lifting platform stability control system includes a virtual main axis collaborative control module, a current feedback compensator module and a multi-motor system module; the virtual main axis collaborative control module user and the calculated total disturbance P of the four pile legs di The different current values ​​assigned to each leg are determined to assign different angular velocities ω to each leg. m The current feedback compensator module calculates the error between the rotation speed of each leg and the other three legs to obtain the ω ei A more accurate rotation speed is obtained through current feedback compensation and distributed to the multi-motor system module; the multi-motor system module controls the lifting platform through the motor according to the rotation speed after current feedback compensation.

[0082] Based on the above-mentioned wind power installation ship lifting platform stability control system based on virtual main axis, the present invention provides a wind power installation ship lifting platform stability control method based on virtual main axis, comprising the following steps:

[0083] S1: Calculate the total disturbance on the four legs of the lifting platform;

[0084] In the actual operation of the four-leg system, there are external disturbances caused by sudden sinking of the leg and the hard crust of the soil; internal disturbances will be generated due to the mismatch of the mathematical model of the motor system; and there will also be disturbances caused by parameter disturbances. Combining the above factors, the system equations with uncertain disturbances are obtained as follows:

[0085]

[0086] Where: f w is the external disturbance, where W1, W2, W3, and W4 are the disturbances caused by different soil properties when the four pile legs are inserted into the seabed, and T Li is the feedback torque from the motion axis, J is the main axis moment of inertia; f n is the internal disturbance, where N1, N2, N3, and N4 are the internal disturbances caused by the mismatch of the mathematical models of the four pile legs; Δu is the disturbance caused by parameter perturbation, and b1, b2, b3, and b4 are the actual parameters of the four pile legs;

[0087] The four-leg disturbance distribution diagram is as follows Figure 4 As shown, refer to Figure 4 , define the total disturbance of the system as

[0088]

[0089] And the above disturbance is extended to the system space state equation, and we get:

[0090]

[0091] In the formula: x=[ω1f1ω2f2ω3f3ω4f4] T ;

[0092]

[0093] S2: Make an unbiased estimate of the calculated total disturbance to obtain disturbance estimation data;

[0094] Based on the system spatial state variables shown in formula (2), a linear extended observer LEO is constructed, which is expressed as

[0095]

[0096] In the formula is the state variable of LEO, where are the estimated values ​​of ω1, ω2, ω3, and ω4 respectively, are the estimated values ​​of f1, f2, f3, and f4 respectively; is the gain matrix of LEO.

[0097] S3: Use the disturbance estimation data to pre-compensate the system;

[0098] When the observer converges stably, f1→f2; therefore, Substituting f1 and f2 in the pile leg control system respectively, we have

[0099]

[0100] According to the linear active disturbance rejection control theory, the disturbance estimated by LEO is used to pre-compensate the system to eliminate the influence of the disturbance on the pile-leg control system.

[0101] S4: Design an anti-disturbance controller to adjust the system response speed;

[0102] The expression of the four-leg control rate is as follows:

[0103]

[0104] Where: k p is the proportionality coefficient; ω ref is the reference speed;

[0105] From equations (4) to (5), we can get the linear active disturbance rejection controller structure of the four-leg control system, which can stabilize the system and adjust the dynamic response speed of the system.

[0106] The subsequent current loop controller is based on i d = 0 control strategy, implemented using PI controller, in the form of

[0107]

[0108] Where: K pd , K pq is the proportionality coefficient; K id , K iq is the integral coefficient; its parameters can be adjusted by the internal model method.

[0109] S5: Distribute current to the pile legs according to the disturbance value;

[0110] The collaborative compensator adopts a virtual main axis structure to achieve the coordinated control of the four pile legs. When the pile leg 1 suddenly sinks, its expression is:

[0111]

[0112] Where: i qc1 、i qc2 、i qc3 、i qc4 is the q-axis given current after coupling coefficient compensation; K is the q-axis reference current output by the speed controller after limiting; c is the coupling coefficient; when leg 1 suddenly sinks, the system calculates the current given to leg 1 based on the pressure difference between leg 1 and the other legs. At the same time, the currents of the other legs are 0, causing them to stop rising and falling;

[0113] When the pile leg 1 is compacted, its expression is

[0114]

[0115] When pile legs 1 and 2 are compacted, the expression is:

[0116]

[0117] When the four pile legs are not disturbed, the speed of the four pile legs does not change, that is, ω1=ω2=ω ref ; From formula (8), we can know that K c (ω1-ω2)=0, at this time, the virtual spindle cooperative controller has no effect on the system; when one of the pile legs is disturbed, ω1≠ω2. It can be seen from formulas (8)-(10) that after the speed difference is coordinated and controlled, the respective feedforward compensation parts are superimposed on the q-axis currents of the four piles, thereby adjusting the output torque of the four piles to achieve the stability of the platform; the coupling coefficient is a coefficient that amplifies the two speed differences. If its value is too large, it will cause the system's speed oscillation or even instability.

[0118] S6: Calculate the speed error corresponding to the pile leg based on the allocated pile leg current;

[0119] In this embodiment, the first pile leg is taken as an example for explanation, and the speed error calculation method of the first pile leg is:

[0120] like Figure 5 As shown, a speed error compensation feedback module corresponding to the first pile leg is established, thereby obtaining the speed error calculation formula of the first pile leg:

[0121] e1=K 12 (n1-n2)+K 13 (n1-n3)+K 14 (n1-n4)+K2[(nK1-(n1+n2+n3+n4)](11)

[0122] Where n, n1, n2, n3, n4 represent the input speed and the feedback speed of motor 1, 2, 3, 4 respectively; K 12 , K 13 , K 14They respectively represent the feedback gain of the synchronization error between leg 1 and the other legs; K1 represents the gain multiple of the input speed, which is determined by the number of motors; K2 represents the overall gain of the difference between the input speed after gain and the feedback speed of the four motors of the entire steering system; e1 represents the final error output of the first speed compensation feedback module.

[0123] S7: For the speed error, the current feedback compensation is performed through the designed current compensator to reduce the error and realize the stable control of the lifting platform;

[0124] In this embodiment, one of the motors is taken as an example. The designed current feedback compensator structure is as follows: Figure 6 As shown in the figure, ΔT r1 is the load disturbance acting on the motor, and K is the coupling coefficient.

[0125] Reference Figure 6 , the design and operation analysis method of the current compensator is:

[0126] When the four pile legs operate normally without disturbance, ΔT r1 =ΔT r2 =ΔT r3 =ΔT r4 =0, n1=n2=n3=n4=n r ,i qf1 =i qf2 =i qf3 =i qf4 =0, the speed difference of the four legs is 0, and the current feedback compensator does not work at this time;

[0127] Taking one of the pile legs as an example, when the system is running stably, the speed signal maintains n1=n2=n3=n4=n r ; When t = t0, load disturbance ΔT r1 Start interfering, at time t0 there is T e1 -(T r1 +ΔT r1 ) <T e2 -T r2 , which results in the desired speed n1 * <n2 * ; At t = t1 (t1>t0), the error between the four legs Δn (Δn = |n1-n p |) reaches the maximum, indicating that the pressure difference between this leg and the other legs is the largest at this time. At this time, the coupling coefficient K is set. After experiencing the gain effect of this coefficient, Δn generates the corresponding current compensation signal i qf1, and feeds it back to the current loop of the motor. Finally, due to the current loop inside the motor, the output speed signal n1 of the motor shaft continuously approaches the given value. At the same time, the second, third and fourth legs also approach the set values ​​synchronously with the signal n1 through the corresponding adjustment mechanism, so that the speeds of the four legs gradually tend to be consistent during the adjustment process, thereby achieving recoverability to external interference.

[0128] The coupling coefficient K determines the control effect of current feedback compensation to a certain extent; when the value of K is too small, it will cause rapid adjustment of the system, and when the value of K is too large, it will cause rapid adjustment of the system, thereby causing oscillation of the speed. Therefore, the present invention proposes a value range of K value that can ensure the synchronization characteristics of the system.

[0129] Reference Figure 6 , the method for determining the value range of the coupling coefficient K is:

[0130] Assume that n p =an1,T r1 +ΔT r1 =bT e1 , then when leg 1 is subjected to load disturbance, we can get the input i qr1 The transfer function from n1(s) to the output n1(s) is

[0131]

[0132] Where p is the pole pair number; ψ f is the cross-linked magnetic flux; J is the moment of inertia; B is the friction coefficient;

[0133] If the control link needs to remain relatively stable, then the left half plane of the s plane must correspond to the characteristic root of the transfer function, so we get

[0134]

[0135] It can be seen from formula (13) that the internal parameters of the motor and the amplitude of the load disturbance to the motor affect K. From the perspective of engineering practicality, based on a real motor prototype, it can be known that as K increases, the synchronization of the system will gradually improve.

Claims

1. A method for stabilizing the lifting platform of a wind power installation vessel based on a virtual main axis, characterized in that: The steps include: S1: Calculate the total disturbance on the four legs of the lifting platform; S2: Make an unbiased estimate of the calculated total disturbance to obtain disturbance estimation data; S3: Use the disturbance estimation data to pre-compensate the system; S4: Design an anti-disturbance controller to adjust the system response speed; S5: Distribute current to the pile legs according to the disturbance value; S6: Calculate the speed error corresponding to the pile leg based on the allocated pile leg current; S7: For the speed error, the current feedback compensation is performed through the designed current compensator to reduce the error and achieve stable control of the lifting platform.

2. The method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 1 is characterized in that: The calculation method of the total disturbance received by the four legs of the lifting platform in step S1 is: The system equations with uncertain interference are obtained as follows: Where: f w is the external disturbance, where W1, W2, W3, and W4 are the disturbances caused by different soil properties when the four pile legs are inserted into the seabed, and T Li is the feedback torque from the motion axis, J is the main axis moment of inertia; f n is the internal disturbance, where N1, N2, N3, and N4 are the internal disturbances caused by the mismatch of the mathematical models of the four pile legs; Δu is the disturbance caused by parameter perturbation, and b1, b2, b3, and b4 are the actual parameters of the four pile legs; The total disturbance of the system is defined as And the above disturbance is extended to the system space state equation, and we get: In the formula: x=[ω1f1ω2f2ω3f3ω4f4] T ; 3. The method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 2 is characterized in that: The method for unbiased estimation of the total disturbance in step S2 is: Based on the system spatial state variables shown in formula (2), a linear extended observer LEO is constructed, which is expressed as In the formula is the state variable of LEO, where are the estimated values ​​of ω1, ω2, ω3, and ω4 respectively, are the estimated values ​​of f1, f2, f3, and f4 respectively; is the gain matrix of LEO.

4. The method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 3 is characterized in that: In step S3, when the observer converges stably, f1→f2; therefore, Substituting f1 and f2 in the pile leg control system respectively, we have According to the linear active disturbance rejection control theory, the disturbance estimated by LEO is used to pre-compensate the system to eliminate the influence of the disturbance on the pile-leg control system.

5. A method for stabilizing the lifting platform of a wind power installation vessel based on a virtual main axis according to claim 4, characterized in that: The step S4 is specifically as follows: The expression of the four-leg control rate is as follows: Where: K p is the proportionality coefficient; ω ref is the reference speed; From equations (4) to (5), we can get the linear active disturbance rejection controller structure of the four-leg control system, which can stabilize the system and adjust the dynamic response speed of the system. The subsequent current loop controller is based on i d = 0 control strategy, implemented using PI controller, in the form of Where: K pd , K pq is the proportionality coefficient; K id , K iq is the integral coefficient; its parameters can be adjusted by the internal model method.

6. A method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 5, characterized in that: The current distribution method in step S5 is: The collaborative compensator adopts a virtual main axis structure to achieve the coordinated control of the four pile legs. When the pile leg 1 suddenly sinks, its expression is: Where: i qc1 、i qc2 、i qc3 、i qc4 is the q-axis given current after coupling coefficient compensation; K is the q-axis reference current output by the speed controller after limiting; c is the coupling coefficient; when leg 1 suddenly sinks, the system calculates the current given to leg 1 based on the pressure difference between leg 1 and the other legs. At the same time, the currents of the other legs are 0, causing them to stop rising and falling; When the pile leg 1 is compacted, its expression is When pile legs 1 and 2 are compacted, the expression is: When the four pile legs are not disturbed, the speed of the four pile legs does not change, that is, ω1=ω2=ω ref ; From formula (8), we can know that K c (ω1-ω2) = 0, at which point the virtual spindle cooperative controller has no effect on the system; when one of the legs is disturbed, ω1≠ω2. It can be seen from formulas (8)-(10) that after the speed difference is coordinated and controlled, the respective feedforward compensation parts are superimposed on the q-axis currents of the four legs, thereby adjusting the output torque of the four legs to achieve platform stability.

7. A method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 6, characterized in that: The speed error calculation method of the first leg in step S6 is: The speed error compensation feedback module corresponding to the first pile leg is established, and the speed error calculation formula of the first pile leg is obtained as follows: e1=K 12 (n1-n2)+K 13 (n1-n3)+K 14 (n1-n4)+K2[(nK1-(n1+n2+n3+n4)](11) Where n, n1, n2, n3, and n4 represent the input speed and the feedback speed of motors 1, 2, 3, and 4 respectively; K 12 , K 13 , K 14 They respectively represent the feedback gain of the synchronization error between leg 1 and the other legs; K1 represents the gain multiple of the input speed, which is determined by the number of motors; K2 represents the overall gain of the difference between the input speed after gain and the feedback speed of the four motors of the entire steering system; e1 represents the final error output of the first speed compensation feedback module.

8. The method for stabilizing the wind power installation vessel lifting platform based on a virtual main axis according to claim 6 is characterized in that: The design and operation analysis method of the current compensator in step S7 is: When the four pile legs operate normally without disturbance, ΔT r1 =ΔT r2 =ΔT r3 =ΔT r4 =0, n1=n2=n3=n4=n r ,i qf1 =i qf2 =i qf3 =i qf4 =0, the speed difference of the four legs is 0, and the current feedback compensator does not work at this time; Taking one of the pile legs as an example, when the system is running stably, the speed signal maintains n1=n2=n3=n4=n r ; When t = t0, load disturbance ΔT r1 Start interfering, at time t0 there is T e1 -(T r1 +ΔT r1 ) <T e2 -T r2 , which results in the desired speed n1 * <n2 * ; At t = t1 (t1>t0), the error between the four legs Δn (Δn = |n1-n p |) reaches the maximum, indicating that the pressure difference between this leg and the other legs is the largest at this time. At this time, the coupling coefficient K is set. After experiencing the gain effect of this coefficient, Δn generates the corresponding current compensation signal i qf1 , and feeds it back to the current loop of the motor. Finally, due to the current loop inside the motor, the output speed signal n1 of the motor shaft continuously approaches the given value. At the same time, the second, third and fourth legs also approach the set values ​​synchronously with the signal n1 through the corresponding adjustment mechanism, so that the speeds of the four legs gradually tend to be consistent during the adjustment process, thereby achieving recoverability to external interference.

9. A method for stabilizing the lifting platform of a wind power installation vessel based on a virtual main axis according to claim 8, characterized in that: The method for determining the value range of the coupling coefficient K in step S7 is: Assume that n p =an1,T r1 +ΔT r1 =bT e1 , then when leg 1 is subjected to load disturbance, we can get the input i qr1 The transfer function from n1(s) to the output n1(s) is Where p is the pole pair number; ψ f is the cross-linked magnetic flux; J is the moment of inertia; B is the friction coefficient; If the control link needs to remain relatively stable, then the left half plane of the s plane must correspond to the characteristic root of the transfer function, so we get It can be seen from formula (13) that the internal parameters of the motor and the amplitude of the load disturbance to the motor affect K. From the perspective of engineering practicality, based on a real motor prototype, it can be known that as K increases, the synchronization of the system will gradually improve.

10. A wind power installation ship lifting platform stability control system based on a virtual main axis, characterized in that: Including virtual spindle collaborative control module, current feedback compensator module and multi-motor system module; The virtual spindle collaborative control module is used to calculate the total disturbance P of the four pile legs. di The different current values ​​assigned to each leg are determined to assign different angular velocities ω to each leg. m ; The current feedback compensator module calculates the error between the rotation speed of each leg and the other three legs to obtain the ω ei Get more accurate speed distribution to multi-motor system modules through current feedback compensation; The multi-motor system module controls the lifting platform through the motor according to the rotation speed after current feedback compensation.

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