Six-degree-of-freedom aerodynamic load simulation system and control method for offshore floating wind turbines

Abstract

The present invention discloses a six-degree-of-freedom aerodynamic load simulation system and control method for an offshore floating wind turbine, and belongs to the field of offshore wind power generation technology and wind turbine test equipment. The simulation system includes a wave and flow simulation device installed at the front of a wave pool, a floating platform is fixed in the middle of the wave pool by a mooring anchor chain, a tower is installed on the floating platform, a cabin is installed on the top of the tower, a six-degree-of-freedom load sensor is installed between the cabin and the tower, a fixed bracket is installed in the front of the cabin, multiple groups of variable-speed fans are installed on the fixed bracket, and the multiple groups of variable-speed fans are connected to the controller through a brushless electronic speed regulator installed in the cabin; a trolley is installed on the upper part of the wave pool, a data acquisition box, a visual camera and a host computer are installed on the top of the trolley, the visual camera is connected to the data acquisition box through a synchronous trigger device, and the data acquisition box is connected to the host computer. The present invention can generate high-precision six-degree-of-freedom aerodynamic loads and accurately evaluate the dynamic performance of offshore floating wind turbines.

Description

Technical Field

[0001] The invention belongs to the field of offshore wind power generation technology and wind turbine test equipment, and in particular to a six-degree-of-freedom aerodynamic load simulation system and a control method for an offshore floating wind turbine. Background Art

[0002] When designing a real-time hybrid model test for an offshore floating wind turbine, the turbine part is mainly affected by aerodynamics, so the "Reynolds similarity" should be used to design the scaled model; while the floating platform part is mainly affected by fluid mechanics, so the "Froude similarity" should be used to design the scaled model. These two completely different similarity criteria will lead to a "scale conflict" phenomenon in the scaled model of the offshore floating wind turbine. This phenomenon can be summarized as follows: at the same scale ratio, the blade size of the scaled model of the offshore floating wind turbine is much larger than that of the floating platform, and this phenomenon will become more and more obvious as the capacity of the offshore wind turbine increases, which will make the design of the scaled model more difficult, and may even lead to problems such as parameter contradictions.

[0003] In order to overcome the "scale conflict" phenomenon, existing solutions can be roughly divided into two categories. The first type of solution retains the scaled rotor model of the offshore floating wind turbine and improves the blade design of the wind turbine through theoretical research on aerodynamics. However, this type of solution must be carried out in a wind tunnel environment in a wind farm, which has high requirements for laboratory equipment. In addition, the center of gravity of the designed scaled model of the offshore floating wind turbine is generally high, and its dynamic performance response is slow and the risk of resonance increases sharply. The number of related studies has declined significantly in recent years. The second solution adopts the idea of ​​combining numerical and physical methods. In the face of the parts in the real-time hybrid model test that cannot be similarly characterized due to the "scale conflict" phenomenon, different aerodynamic load simulation systems are designed to replace the scaled rotor, so as to ensure that the scaled model and the wind turbine prototype have similar aerodynamic characteristics. Up to now, the aerodynamic load simulation system has become the mainstream solution for solving the "scale conflict" phenomenon in the real-time hybrid model test of offshore floating wind turbines.

[0004] However, at present, there is still no standardized design method for aerodynamic load simulation system. Most of the existing technical solutions have certain limitations. Their defects can be summarized as follows: (1) It still needs to be used in conjunction with wind-generating equipment, resulting in low universality of real-time hybrid model tests of offshore floating wind turbines; (2) The aerodynamic loads generated by the aerodynamic load simulation system are not accurate enough and cannot fully cover the six degrees of freedom, resulting in low similarity between the aerodynamic characteristics of the scaled model and the wind turbine prototype; (3) Most physical actuators use braking devices such as electric cylinders and vibration tables, which have slow dynamic response speeds and cannot meet the simulation requirements of high-frequency loads of offshore floating wind turbines; (4) Most physical actuators use open-loop control methods. In the face of disturbances or uncertainties, it is difficult to maintain accurate output, resulting in reduced stability and reliability of the system. How to design a six-degree-of-freedom aerodynamic load simulation system that does not require wind-generating equipment, combined with a reasonable closed-loop feedback control method, and then realize the dynamic performance verification of offshore floating wind turbines is a key problem that needs to be solved in this field.

[0005] Chinese invention patent CN113740025A discloses a test device suitable for active real-time hybrid model test of floating wind turbines, which includes the following steps: installing a floating simulation device, which includes a base and a simulated floating platform, the base and the floating platform are connected by a number of length and angle adjustment devices, and the length of the driving end adjustment device is used to realize the freedom control of the floating platform movement; installing a wind turbine cabin above the simulated floating platform, which is provided with a variable speed gearbox in the cabin, and three wind turbine blades are connected to the output end; the screw member inside the hollow tower is connected to the wind turbine control module, which is used to accurately control the blade pitch angle and speed, and the wind turbine control module is used to adjust the pitch angle and speed of the wind turbine blades. However, this invention patent must be used in conjunction with wind farms, wind tunnels and other wind-generating equipment, which limits its independence and universality in carrying out real-time hybrid model tests, and also has high requirements on the wind-generating quality and repeatability of wind-generating equipment.

[0006] Chinese invention patent CN116011193A discloses a hybrid model test method for offshore wind turbines that can be used for a variety of foundation types, which includes the following steps: according to the Froude similarity principle, a scaled model including a wind turbine tower, a wind turbine foundation and a mooring line is made; an indoor wave pool is selected according to different wind turbine foundations, and wave conditions are calibrated by wave height meters and spectrum analysis; a gantry crane, a multi-degree-of-freedom loading brake, a six-dimensional force sensor and other test devices are hoisted into the wave pool; an optical measurement system is installed on both sides of the wave pool, and the blade element momentum model in aerodynamics is used for iterative calculation and overall test; the interaction of the blade element momentum model, the physical model and the actuator reflects the aerodynamic load on the wind turbine prototype. However, the actuator part of the invention patent uses brake devices such as electric cylinders and vibration tables, which have a slow dynamic response speed and cannot effectively meet the simulation requirements of high-frequency loads of floating wind turbines. Different gantry cranes need to be configured for different wind turbine prototypes, which increases the complexity of the layout of the real-time hybrid model test site.

[0007] Chinese invention patent CN117386568A discloses a real-time hybrid model test method for multi-fan drive of offshore floating wind turbine, which includes the following steps: according to the parameters of wind turbine prototype, establish a multi-fan drive system as the actuator of floating wind turbine motion; establish a wind turbine numerical substructure, modify OpenFAST software to enable it to read the six-degree-of-freedom motion of floating platform, and output the six-degree-of-freedom load of drive system; collect the position and speed of six degrees of freedom of platform in set period in real time through attitude sensor, acceleration sensor and laser distance sensor, and send the measurement results to the wind turbine numerical substructure; design platform experimental model and conduct water tank experiment, track the six-degree-of-freedom motion of measurement platform under wave excitation in real time, and load the aerodynamic load calculated by numerical model to the wind turbine platform through drive. However, the multi-fan drive system of the invention patent does not provide real-time closed-loop feedback on fan thrust or motor speed, and the open-loop control method adopted by it is difficult to face the dynamically changing marine environment, which may cause the output result of the system to deviate from the expectation, affecting the reliability of real-time hybrid model test; and the multi-fan drive system of the patent lacks negative force of Z axis, and there is the problem of inaccurate simulation of aerodynamic load MX. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a six-degree-of-freedom aerodynamic load simulation system and control method for an offshore floating wind turbine, which can generate high-precision six-degree-of-freedom aerodynamic loads to accurately evaluate the dynamic performance of the offshore floating wind turbine.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A six-degree-of-freedom pneumatic load simulation system for an offshore floating wind turbine comprises a wave and flow simulation device installed at the front of a wave pool, a floating platform fixed in the middle of the wave pool by a mooring anchor chain, a tower installed on the floating platform, a cabin installed on the top of the tower, a six-degree-of-freedom load sensor installed between the cabin and the tower, a fixed bracket installed at the front of the cabin, a plurality of groups of variable-speed fans installed on the fixed bracket, and the plurality of groups of variable-speed fans are connected to a controller via a brushless electronic speed regulator installed in the cabin; an aerial vehicle is installed on the upper part of the wave pool, a data acquisition box, a visual camera and a host computer are installed on the top of the aerial vehicle, the visual camera is connected to the data acquisition box via a synchronous trigger device, and the data acquisition box is connected to the host computer.

[0011] The variable speed fans are seven in number and are arranged in the form of inner and outer double concentric circles.

[0012] The seven sets of variable fans are arranged in a clockwise direction as follows:

[0013] The variable speed fan No. 1 is located at the nine o'clock position of the outer circle, and the thrust F1 it generates is vertically upward;

[0014] The second variable speed fan is located at one o'clock on the outer circle, and the thrust F2 it generates is horizontal to the right;

[0015] The variable speed fan No. 3 is located at the five o'clock position of the outer circle, and the thrust F3 it generates is horizontal to the left;

[0016] The variable speed fan No. 7 is located at the nine o'clock position of the outer circle, and the thrust F7 it generates is vertically downward;

[0017] Among them, the variable speed fan No. 1 and the variable speed fan No. 7 are coaxially arranged;

[0018] The variable speed fan No. 4 is located at the nine o'clock position of the inner circle, and the thrust F4 it generates is directed backwards, perpendicular to the thrust direction of the variable speed fans No. 1 and No. 7;

[0019] The No. 5 variable speed fan is located at one o'clock on the inner circle, and the thrust F5 it generates is directed backwards, perpendicular to the thrust direction of the No. 2 variable speed fan;

[0020] The variable speed fan No. 6 is located at the five o'clock position of the inner circle, and the thrust F6 it generates is directed toward the rear, perpendicular to the thrust direction of the variable speed fan No. 3.

[0021] The variable speed fan comprises a brushless motor and a propeller connected together, wherein the brushless motor is powered by three-phase AC power of A, B, and C, and the brushless motor drives the propeller to rotate to generate lift or thrust.

[0022] The brushless electronic speed regulator has seven groups, each group includes three AC phase lines A, B, C, and two signal lines SGN and GND, wherein the AC phase lines A, B, C are respectively connected to the three-phase lines A, B, and C of the brushless motor, and adopt the AA, BC, and CB phase-changing wiring method to realize the reversal of the brushless motor and generate the required thrust in all directions; the seven SGN lines are respectively connected to different PWM pins of the controller; the seven GND lines are connected in parallel and connected to the GND pin of the controller at the same time.

[0023] The fixed bracket includes three support arms and a support base. The three support arms are distributed in a "Y" shape, and the three angles are all 120 degrees. The support base is located at the center of the three support arms.

[0024] In clockwise direction, the No. 1 support arm is located at the nine o'clock position, and the No. 1 variable speed fan, the No. 7 variable speed fan and the No. 4 variable speed fan are installed on the No. 1 support arm;

[0025] The second support arm is located at one o'clock, and the second variable speed fan and the fifth variable speed fan are installed on the second support arm;

[0026] Support arm number three is located at the five o'clock position, and variable speed fan number three and variable speed fan number six are installed on support arm number three.

[0027] The controller has pins 2, 3, 4, 5, 6, 7 and 8 which are all PWM pins, which are respectively connected to seven SGN lines of seven groups of brushless electronic speed regulators; and the GND pin is simultaneously connected to seven GND lines.

[0028] The cabin is connected to the fixed bracket through a card slot in a parallel direction, and the internal space is used to place seven sets of brushless electronic speed regulators and controllers.

[0029] The tower is connected to the cabin via a vertical slot.

[0030] The floating platform is connected to the tower through a vertical slot.

[0031] The mooring anchor chain is connected to the floating platform via a metal buckle.

[0032] A control method for a six-degree-of-freedom aerodynamic load simulation system of an offshore floating wind turbine comprises the following steps:

[0033] Step 1: The visual camera of the motion capture device in the real-time measurement system immediately sends the six-degree-of-freedom displacement, velocity, acceleration and position of the floating platform to the aerodynamic load calculation module of the control system in the host computer at the beginning of this cycle; perform dynamic analysis and obtain the corresponding six-degree-of-freedom aerodynamic load of the floating offshore wind turbine as shown in equation (2):

[0034] (2),

[0035] In equation (2), FX, FY, FZ, MX, MY and MZ are the six-degree-of-freedom aerodynamic loads required by the scaled model of the offshore floating wind turbine; F1, F2, F3, F4, F5, F6 and F7 are the thrusts generated by the seven sets of variable-speed fans; a is the distance from variable-speed fan No. 1 to variable-speed fan No. 4; b is the distance from variable-speed fan No. 4 to the center of the supporting base;

[0036] Step 2: The aerodynamic load decoupling module in the control system of the host computer performs decoupling analysis and calculation. The speed / thrust of the variable speed fan presents a complex nonlinear relationship. During the actual operation, an n-order polynomial relationship is used for fitting to obtain equation (3):

[0037] (3)

[0038] In equation (3), F is the thrust generated by the variable speed fan; ω is the speed of the brushless motor; a is the polynomial coefficient; n is the polynomial order;

[0039] Step 3, when step 1 is implemented, the synchronous trigger device immediately sends a synchronous electrical signal to the six-degree-of-freedom load sensor, collects the analog electrical signal of the actual six-degree-of-freedom aerodynamic load in the previous cycle, and the data acquisition box converts it into a corresponding digital signal, and finally feeds the digital signal back to the aerodynamic load decoupling module in real time through the network port; after receiving the actual six-degree-of-freedom aerodynamic load of the previous cycle, the aerodynamic load decoupling module again calls equation (2) to calculate the thrust actually generated by the seven sets of variable speed fans in the previous cycle, and finally calls equation (3) to calculate the actual speed of the seven sets of brushless motors in the previous cycle;

[0040] (4)

[0041] (5),

[0042] In equations (4)-(5), D is the PWM pulse signal generated by the Ardunio MEGA2560 controller; KP is the proportional coefficient; KI is the integral coefficient; KD is the differential coefficient; k is the current cycle number; e(k) is the speed deviation signal of this cycle; e(k-1) is the speed deviation signal of the previous cycle; ω(k) is the speed of the brushless motor, ref represents the reference value, and rel represents the measured value;

[0043] Step 4: The aerodynamic load calculation module calculates the difference between the required speed of the seven brushless motors in this cycle and the actual speed of the seven brushless motors in the previous cycle, calls equation (4) to obtain the deviation value of the speed of the seven variable speed fans, and calls equation (5) to obtain the decimal PWM pulse signals of the seven required speeds in this cycle, and sends them to the controller placed in the cabin;

[0044] Step 5, after determining that the binary PWM pulse signal is received, the pneumatic load control module in the controller reads and converts it into seven groups of character strings, and then parses it into corresponding PWM variables and stores them in seven groups of arrays; finally, the seven groups of arrays are output, and the corresponding PWM pins are triggered in turn, and the speeds of the seven groups of brushless motors are controlled through the seven SGN lines of the brushless electronic speed regulator to generate the required thrust;

[0045] Step 6, continue to repeat steps 1 to 5 until the specified cycle time or the specified number of cycles is reached, and all data during the operation will be stored in the host computer.

[0046] The beneficial effects of the present invention are:

[0047] On the first aspect, the present invention can effectively solve the "scale conflict" problem of real-time hybrid model tests of offshore floating wind turbines in wave pools, and does not rely on wind tunnels and wind farm equipment. It can be widely used in all types of real-time hybrid model tests of offshore floating wind turbines, thereby improving the universality and practicality of the system.

[0048] Secondly, the present invention can completely generate six-degree-of-freedom aerodynamic loads, realize closed-loop real-time feedback control by using a position-based proportional-integral-differential control algorithm, and can accurately generate six-degree-of-freedom aerodynamic loads FX, FY, FZ, MX, MY and MZ of a scaled model of an offshore floating wind turbine, thereby improving the aerodynamic similarity between the scaled model and the wind turbine prototype.

[0049] Thirdly, the interference of human error factors is reduced. Through the synchronous triggering device of the real-time measurement system in the present invention, the data delay and desynchronization caused by the test personnel manually triggering each sensor collection device can be reduced, and the reliability of the real-time hybrid model test can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the overall layout of the six-degree-of-freedom pneumatic load simulation system;

[0051] Figure 2 This is a schematic diagram of the installation of seven sets of variable speed fans and fixed brackets from a front view;

[0052] Figure 3 This is a schematic diagram of the installation of seven sets of variable speed fans and fixed brackets from a side view;

[0053] Figure 4 The aerodynamic loading system generates performance diagrams for sudden thrust loads;

[0054] Figure 5 Pneumatic loading system generates performance graphs for reciprocating cyclic loading;

[0055] Figure 6 The Pneumatic Loading System generates performance graphs of the Pneumatic Loading FX;

[0056] Figure 7 The pneumatic load loading system generates a performance diagram of the pneumatic load FY;

[0057] Figure 8 The pneumatic load loading system generates a performance diagram of the pneumatic load FZ;

[0058] Fig. 9 The Pneumatic Loader system generates performance graphs of the Pneumatic Loader MX;

[0059] Fig.10 The pneumatic load loading system generates a performance diagram of the pneumatic load MY;

[0060] Fig.11 The pneumatic load loading system generates a performance diagram of the pneumatic load MZ.

[0061] Among them, 1. wave pool, 2. wave and current simulation equipment, 3. aerial vehicle, 4. fixed bracket, 5. cabin, 6. tower, 7. floating platform, 8. mooring chain, 9. six-degree-of-freedom load sensor, 10. data acquisition box, 11. visual camera, 12 host computer, 13. synchronous trigger device. DETAILED DESCRIPTION

[0062] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0063] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical contents.

[0064] Figure 1 It is a schematic diagram of the overall layout of the six-degree-of-freedom pneumatic load simulation system in the present invention, including a wave and flow simulation device 2, a vehicle 3, a fixed bracket 4, a cabin 5, a tower 6, a floating platform 7, a mooring anchor chain 8, a six-degree-of-freedom load sensor 9, a data acquisition box 10, a visual camera 11, a host computer 12, and a synchronous trigger device 13. The specific description is as follows:

[0065] The wave and current simulation equipment 2 is installed at the front of the wave pool 1, and is used to simulate regular waves and irregular waves of different frequencies, periods and wavelengths; the vehicle 3 is located above the wave pool 1, and is used to install the data acquisition box 10, the visual camera 11 and the host computer 12, where the test personnel perform test configuration and operation control; the synchronous trigger device 13 connects the visual data acquisition box 10 with the visual camera 11, and is used to realize the synchronous acquisition function between the visual camera 11 and the six-degree-of-freedom load sensor 9; the cabin 5, the tower 6, the floating platform 7 and the mooring anchor chain 8 are designed as scale models according to "geometric similarity" and "Froude similarity"; the fixed bracket 4 is installed in front of the cabin 5; the six-degree-of-freedom load sensor 9 is installed between the cabin 5 and the tower 6, and is used to measure the six-degree-of-freedom load at the top of the tower 6.

[0066] In this embodiment, a high-precision visual camera 11 and a host computer 12 together constitute a motion capture device, which is installed just above the physical execution system and can capture and record the six-degree-of-freedom displacement, velocity, acceleration and position of the floating platform 7 in real time.

[0067] The six-degree-of-freedom load sensor and the data acquisition box constitute a sensing acquisition device; the six-degree-of-freedom load sensor is located at the top of the tower and can measure the six-degree-of-freedom pneumatic load generated by the physical execution system in real time; the data acquisition box can record the analog electrical signal of the six-degree-of-freedom load sensor in real time, and convert it into a corresponding digital signal using the LabVIEW language function, and finally feed the digital signal back to the software control system in real time through the network port.

[0068] The synchronous trigger device is an existing product (synchronous trigger or synchronous trigger instrument), which connects the motion capture device with the sensor acquisition device, and uses synchronous electrical signals to realize the synchronous acquisition function between the visual camera and the six-degree-of-freedom load sensor, thereby minimizing the time delay and desynchronization between each measurement data, and improving the reliability of real-time hybrid model testing.

[0069] Figure 2 and Figure 3 The installation relationship between the seven sets of variable speed fans and the fixed brackets is shown in partial enlargement from the front view and the side view, respectively, as follows:

[0070] There are seven groups of variable speed fans, which are arranged in double concentric circles and installed on a fixed bracket 4; the RS-485 serial port transmission line of the Ardunio MEGA2560 controller receives the PWM pulse signal generated by the host computer 12, and the seven groups of PWM pins generate corresponding PWM pulse signals and send them to the seven groups of brushless electronic speed regulators through the SGN line, thereby controlling the speed of the brushless motor; the seven groups of brushless electronic speed regulators and the Ardunio MEGA2560 controller are all placed in the cabin 5.

[0071] Each set of variable speed fans is composed of a brushless motor and a propeller, wherein the brushless motor is powered by three-phase AC power of A, B, and C, has a fast speed and high efficiency, and the brushless motor drives the propeller to rotate to generate lift or thrust. There are seven sets of variable speed fans, which are arranged in the form of inner and outer double concentric circles. In the clockwise direction, variable speed fan No. 1 is located at the nine o'clock direction of the outer circle, and the thrust F1 it generates is vertically upward; variable speed fan No. 2 is located at the one o'clock direction of the outer circle, and the thrust F2 it generates is horizontal to the right; variable speed fan No. 3 is located at the five o'clock direction of the outer circle, and the thrust F3 it generates is horizontal to the left; variable speed fan No. 7 is located at the nine o'clock direction of the outer circle, and the thrust F7 it generates is vertically downward; wherein, Variable speed fan No. 1 is coaxially arranged with variable speed fan No. 7; variable speed fan No. 4 is located at the nine o'clock position of the inner circle, and the thrust F4 generated by it is toward the rear, which is perpendicular to the thrust directions of variable speed fan No. 1 and variable speed fan No. 7; variable speed fan No. 5 is located at the one o'clock position of the inner circle, and the thrust F5 generated by it is toward the rear, which is perpendicular to the thrust direction of variable speed fan No. 2; variable speed fan No. 6 is located at the five o'clock position of the inner circle, and the thrust F6 generated by it is toward the rear, which is perpendicular to the thrust direction of variable speed fan No. 3.

[0072] The brushless electronic speed regulator has seven groups, each group includes three AC phase lines (A, B, C) and two signal lines (SGN, GND). The AC phase lines (A, B, C) are respectively connected to the three-phase lines ABC of the brushless motor, and the AA, BC, CB phase-changing wiring method is adopted to achieve the reverse rotation of the brushless motor and generate the required thrust in all directions. The seven SGN lines are respectively connected to different PWM pins of the Ardunio MEGA2560 controller; the seven GND lines are connected in parallel and connected to the GND pin of the Ardunio MEGA2560 controller at the same time.

[0073] The fixed bracket includes three support arms and a support base. The length of the support arms is 85 cm. The three support arms are distributed in a "Y" shape. The three angles are 120 degrees. The support base is located at the center of the three support arms. In the clockwise direction, the No. 1 support arm is located at the nine o'clock direction. The No. 1 variable speed fan, the No. 7 variable speed fan and the No. 4 variable speed fan are installed on the No. 1 support arm. The distance from the No. 1 variable speed fan and the No. 7 variable speed fan to the center of the support base is 85 cm, and the distance from the No. 4 variable speed fan to the center of the support base is 4 0 cm; Support arm No. 2 is located at one o'clock direction, and the variable-speed fan No. 2 and the variable-speed fan No. 5 are installed on support arm No. 2, wherein the distance between variable-speed fan No. 2 and the center of the support base is 85 cm, and the distance between variable-speed fan No. 5 and the center of the support base is 40 cm; Support arm No. 3 is located at five o'clock direction, and the variable-speed fan No. 3 and the variable-speed fan No. 6 are installed on support arm No. 3, wherein the distance between variable-speed fan No. 3 and the center of the support base is 85 cm, and the distance between variable-speed fan No. 6 and the center of the support base is 40 cm.

[0074] The Ardunio MEGA2560 controller has pins 2, 3, 4, 5, 6, 7 and 8 which are all PWM pins, connected to seven SGN lines of seven brushless electronic speed regulators respectively; and the GND pin is connected to seven GND lines at the same time. The present invention selects the MODBUS communication protocol with wide compatibility in the field of industrial control. In order to improve the communication efficiency of the system, the modulation rate is set to the standard baud rate of 115200.

[0075] The nacelle is connected to the fixed bracket through the slots in the parallel direction, and the internal space is used to place seven sets of brushless electronic speed regulators and Ardunio MEGA2560 controllers. The tower is connected to the nacelle through the slots in the vertical direction. The floating platform is connected to the tower through the slots in the vertical direction. The mooring anchor chain is connected to the floating platform through metal ring buckles.

[0076] The software control system in this embodiment includes a pneumatic load calculation module, a pneumatic load decoupling module and a pneumatic load control module, wherein the pneumatic load calculation module and the pneumatic load decoupling module run in the same host computer, and the pneumatic load control module runs in the onboard memory of the Ardunio MEGA2560 controller.

[0077] The aerodynamic load calculation module is written in Fortran language. By modifying the structural power module Elaston and the drive module Fast of the OpenFAST software, it can read the six-degree-of-freedom displacement, velocity, acceleration and position of the scaled model of the offshore floating wind turbine in the previous cycle in real time, and calculate the theoretical required values ​​of the six-degree-of-freedom aerodynamic loads FX, FY, FZ, MX, MY and MZ of the scaled model in this cycle, and repeatedly generate new dynamic link library DLL executable applications.

[0078] The aerodynamic load decoupling module is written in Python and connected to the aerodynamic load calculation module through the dynamic link library DLL file. The calculated six-degree-of-freedom aerodynamic loads FX, FY, FZ, MX, MY and MZ can be converted into the required thrusts F1, F2, F3, F4, F5, F6 and F7 of seven sets of variable-speed fans using equation (2). The seven sets of required PWM pulse signals are obtained using equations (3)-(5), and then the PWM pulse signals of this round are sent to the ArdunioMEGA2560 controller through the RS-485 serial port transmission line.

[0079] The pneumatic load control module is written in C language. The Ardunio MEGA2560 controller uses the Serial.available() function in the main loop loop() to continuously monitor whether the PWM pulse signal of the RS-485 serial port transmission line is received. After receiving the current round of PWM pulse signal, the Serial.readString() function is used to read the string of the RS-485 serial port, and the strtok() function is used to parse the current round of PWM pulse signal with commas as separators. Finally, the writeMicroseconds() function is used to output the PWM pulse signal in sequence to control the speed of the seven brushless motors and generate the required thrusts F1, F2, F3, F4, F5, F6 and F7.

[0080] In the above process, the hardware physical execution system and the software control system interact and cooperate to decouple the coupled aerodynamic load equations FX, FY, FZ, MX, MY and MZ into seven independent thrust equations F1, F2, F3, F4, F5, F6 and F7. During operation, it is only necessary to control the Ardunio MEGA2560 controller to generate the PWM pulse signal corresponding to the required thrust in this cycle, so as to fully and accurately reproduce the six-degree-of-freedom aerodynamic load of the scaled model of the offshore floating wind turbine, which greatly reduces the control difficulty of the system, and realizes closed-loop control with real-time feedback through the position-based proportional-integral-differential control algorithm to achieve higher control accuracy.

[0081] The six-degree-of-freedom aerodynamic load simulation system and control method of an offshore floating wind turbine adopts a position proportional-integral-differential control algorithm, and the cycle process is as follows:

[0082] Step 1: The visual camera 11 of the motion capture device in the real-time measurement system immediately sends the six-degree-of-freedom displacement, velocity, acceleration and position of the floating platform 7 to the pneumatic load calculation module of the software control system in the host computer 12 at the beginning of this cycle; the pneumatic load calculation module reads the six-degree-of-freedom displacement, velocity, acceleration and position information of the floating platform 7 in real time, and uses the Fortran language to modify the structural power module Elaston and the drive module Fast of the OpenFAST software, and at the same time modify the ElastonDyn module to consider the impact of the movement of the floating platform 7 on the cabin 5 and the tower 6; finally, the theoretical demand value FX of the six-degree-of-freedom aerodynamic load on the top of the tower 6 in this cycle is calculated. ref 、FY ref , FZ ref MX ref MY ref With MZ ref , and then generate a new dynamic link library DLL executable application for use by the pneumatic load decoupling module in the software control system.

[0083] The dynamic analysis is performed and the corresponding six-degree-of-freedom aerodynamic load of the floating offshore wind turbine is obtained as shown in equation (1):

[0084] (1),

[0085] In equation (1), FX, FY, FZ, MX, MY and MZ are the six-degree-of-freedom aerodynamic loads required by the scaled model of the offshore floating wind turbine; F1, F2, F3, F4, F5, F6 and F7 are the thrusts generated by the seven sets of variable-speed fans; a is the distance from the variable-speed fan No. 1 to the variable-speed fan No. 4, i.e. 45 cm; b is the distance from the variable-speed fan No. 4 to the center of the supporting base, i.e. 40 cm.

[0086] Observing equation (1), it can be found that it is an underdetermined matrix with infinite solutions. To obtain a unique solution, it is only necessary to set the thrust generated by the variable speed fan No. 7 to a constant 3 N and perform a matrix inversion operation to obtain a unique positive solution, as shown in equation (2):

[0087] (2),

[0088] Step 2: The aerodynamic load decoupling module in the software control system in the host computer 12 compiles a new dynamic link library DLL file to obtain the six-degree-of-freedom aerodynamic load FX at the top of the tower 6 in this cycle. ref 、FYref , FZ ref MX ref MY ref With MZ ref The theoretical demand value is then used to calculate the thrust F1 required by the seven sets of variable speed fans in this cycle. ref 、F2 ref 、F3 ref 、F4 ref , F5 ref , F6 ref and F7 ref Finally, equation (3) is used to calculate the required speed ω1 of the seven brushless motors in this cycle. ref ω2 ref ,ω3 ref ,ω4 ref ,ω5 ref ,ω6 ref and ω7 ref .

[0089] The six-degree-of-freedom aerodynamic load simulation system converts the coupled aerodynamic load equations FX, FY, FZ, MX, MY and MZ into seven sets of independent variable-speed fan thrust equations F1, F2, F3, F4, F5, F6 and F7. During operation, it only needs to control the Ardunio MEGA2560 controller to generate the corresponding PWM pulse signal according to the corresponding relationship between the speed / thrust of the variable-speed fan, so as to fully and accurately reproduce the six-degree-of-freedom aerodynamic load of the scaled model of the offshore floating wind turbine.

[0090] The speed / thrust of a variable speed fan presents a complex nonlinear relationship. In actual operation, an n-order polynomial relationship can be used for fitting, as shown in equation (3):

[0091] (3),

[0092] In equation (3), F is the thrust generated by the variable speed fan; ω is the speed of the brushless motor; a is the polynomial coefficient; n is the polynomial order. If n is too small, the fitting effect will be poor, thereby affecting the accuracy of the real-time hybrid model test. If n is too large, the polynomial equation will be ill-conditioned and cannot be solved. The present invention recommends using a third-order polynomial for fitting, that is, n=3.

[0093] Step 3: When the visual camera 11 sends the six-degree-of-freedom displacement, velocity, acceleration and position information of the floating platform 7 to the pneumatic load calculation module, the synchronous trigger device 13 immediately sends a synchronous electrical signal to the sensor collection device, and then the six-degree-of-freedom load sensor 9 collects the actual six-degree-of-freedom pneumatic load FX in the previous cycle. rel 、FY rel , FZrel MX rel MY rel and MZ rel The data acquisition box 10 converts the analog electrical signal into a corresponding digital signal using the LabVIEW language function, and finally feeds the digital signal back to the pneumatic load decoupling module in real time through the network port; the pneumatic load decoupling module receives the actual six-degree-of-freedom pneumatic load FX rel 、FY rel , FZ rel MX rel MY rel and MZ rel Later, equation (2) is called again to calculate the thrust F1 actually generated by the seven sets of variable speed fans in the previous cycle: rel 、F2 rel 、F3 rel 、F4 rel , F5 rel , F6 rel and F7 rel Finally, equation (3) is used to calculate the actual speed ω1 of the seven brushless motors in the previous cycle. rel ω2 rel ,ω3 rel ,ω4 rel ,ω5 rel ,ω6 rel and ω7 rel .

[0094] The control method of the brushless motor PWM pulse signal selects the position proportional-integral-differential control algorithm which is the most widely used in the industrial control field, as shown in equations (4)-(5):

[0095] (4),

[0096] (5),

[0097] In equations (4)-(5), D is the PWM pulse signal generated by the Ardunio MEGA2560 controller; KP is the proportional coefficient; KI is the integral coefficient; KD is the differential coefficient; k is the current cycle number; e(k) is the speed deviation signal of this cycle; e(k-1) is the speed deviation signal of the previous cycle; ω(k) is the speed of the brushless motor, ref represents the reference value, and rel represents the measured value.

[0098] Step 4: The pneumatic load calculation module calculates the required speeds of the seven brushless motors in this cycle ω1 ref ω2 ref ,ω3 ref ,ω4 ref ,ω5ref ,ω6 ref and ω7 ref The actual speed of the seven brushless motors in the previous cycle is ω1 rel ω2 rel ,ω3 rel ,ω4 rel ,ω5 rel ,ω6 rel and ω7 rel By making a difference, equation (4) is called to obtain the deviation values ​​e1, e2, e3, e4, e5, e6 and e7 of the speed of the seven variable speed fans, and equation (5) is called to obtain the seven required decimal PWM pulse signals D1, D2, D3, D4, D5, D6 and D7 in this cycle, and then the seven required decimal PWM pulse signals D1, D2, D3, D4, D5, D6 and D7 are sent to the Ardunio MEGA2560 controller placed in cabin 5 through the RS-485 serial port transmission line.

[0099] Step 5, the pneumatic load control module in the Ardunio MEGA2560 controller will continue to call the Serial.available() function in the main loop loop() to detect whether the seven required decimal PWM pulse signals D1, D2, D3, D4, D5, D6 and D7 sent by the RS-485 serial port transmission line are received; after confirming that the data has been received, the Serial.readString() function is called to read the decimal PWM pulse signals D1, D2, D3, D4, D5, D6 and D7 sent by the RS-485 serial port transmission line, and convert them into seven groups of strings, which are then separated by commas and parsed into corresponding PWM variables using the strtok() function and stored in seven groups of pwmValues ​​arrays; finally, the seven groups of pwmValues ​​arrays are output by calling the writeMicroseconds function of the servo library, and the PWM pins 2, 3, 4, 5, 6, 7 and 8 are triggered in turn, and then the speeds of the seven groups of brushless motors are controlled through the seven SGN lines of the brushless electronic speed regulator to generate the required thrust.

[0100] Step 6, continue to repeat steps 1 to 5 until the specified cycle time or the specified number of cycles is reached, and all data during the operation will be stored in the host computer 12.

[0101] In order to illustrate the simulation effect of the six-degree-of-freedom pneumatic load simulation system of the present invention on aerodynamic characteristics, the actual measured values ​​of the system are compared with the results of the OpenFAST simulation calculation values ​​to verify the feasibility and correctness of the system. Three typical performance test settings are as follows:

[0102] In order to verify the performance of the six-degree-of-freedom aerodynamic load simulation system in generating sudden thrust loads, the most representative step signal was used for thrust testing. The comparison results are as follows: Figure 4 It can be found that the FX thrust load generated by the six-degree-of-freedom aerodynamic load simulation system is highly consistent with the demand curve, without obvious hysteresis, and can meet the performance requirements of simulating sudden thrust loads of offshore floating wind turbines.

[0103] In order to verify the performance of the six-degree-of-freedom pneumatic load simulation system in generating reciprocating cyclic loads, the most representative sinusoidal signal was used for thrust testing. The comparison results are as follows: Figure 5 It can be found that the six-degree-of-freedom aerodynamic load simulation system performs well in the sinusoidal thrust test, with a high degree of waveform consistency, and can meet the performance requirements of simulating reciprocating cycle thrust loads.

[0104] In order to verify the performance of the six-degree-of-freedom aerodynamic load simulation system in generating six-degree-of-freedom aerodynamic loads, the most representative Kaimal turbulent wind speed spectrum is used, and the wind speed is set to 11.4 m / s. The comparison results are as follows Figure 6-Figure 11 As shown. It can be found that the simulation effect of the six-degree-of-freedom pneumatic load simulation system on the pneumatic loads FX, MX, FZ, MY and MZ is good, but the simulation effect on the pneumatic load FY is not as good as that of the other five-degree-of-freedom pneumatic loads. This is because the fixed bracket 4 resonates in the Y-axis direction. In future improvements, it can be considered to install a vibration damper to solve this problem. Overall, the six-degree-of-freedom pneumatic load simulation system can meet the performance requirements of the real-time hybrid model test of offshore floating wind turbines.

[0105] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A control method for a six-degree-of-freedom aerodynamic load simulation system for an offshore floating wind turbine, characterized in that: The six-degree-of-freedom aerodynamic load simulation system of the offshore floating wind turbine comprises a wave and flow simulation device installed at the front of the wave pool, a floating platform is fixed in the middle of the wave pool by a mooring anchor chain, a tower is installed on the floating platform, a cabin is installed on the top of the tower, a six-degree-of-freedom load sensor is installed between the cabin and the tower, a fixed bracket is installed at the front of the cabin, a plurality of groups of variable-speed fans are installed on the fixed bracket, and the plurality of groups of variable-speed fans are connected to the controller through a brushless electronic speed regulator installed in the cabin; a trolley is installed on the upper part of the wave pool, a data acquisition box, a visual camera and a host computer are installed on the top of the trolley, the visual camera is connected to the data acquisition box through a synchronous trigger device, and the data acquisition box is connected to the host computer; the controller is an Ardunio MEGA2560 controller; The number of the variable speed fans is seven, which are arranged in the form of inner and outer double concentric circles. The seven variable speed fans are arranged in a clockwise direction as follows: The variable speed fan No. 1 is located at the nine o'clock position of the outer circle, and the thrust F1 it generates is vertically upward; The second variable speed fan is located at one o'clock on the outer circle, and the thrust F2 it generates is horizontal to the right; The variable speed fan No. 3 is located at the five o'clock position of the outer circle, and the thrust F3 it generates is horizontal to the left; The variable speed fan No. 7 is located at the 9 o'clock position of the outer circle, and the thrust F7 it generates is vertically downward. The thrust generated by the variable speed fan No. 7 is set to a constant 3N; Among them, the variable speed fan No. 1 and the variable speed fan No. 7 are coaxially arranged; The variable speed fan No. 4 is located at the nine o'clock position of the inner circle, and the thrust F4 it generates is directed backwards, perpendicular to the thrust direction of the variable speed fans No. 1 and No. 7; The No. 5 variable speed fan is located at one o'clock on the inner circle, and the thrust F5 it generates is directed backwards, perpendicular to the thrust direction of the No. 2 variable speed fan; The variable speed fan No. 6 is located at the 5 o'clock position of the inner circle, and the thrust F6 it generates is directed backwards, perpendicular to the thrust direction of the variable speed fan No. 3; The controller has pins 2, 3, 4, 5, 6, 7 and 8 which are all PWM pins, connected to seven SGN lines of seven groups of brushless electronic speed regulators respectively; The control method comprises the following steps: Step 1: The visual camera immediately sends the six-degree-of-freedom displacement, velocity, acceleration and position of the floating platform to the aerodynamic load calculation module of the control system in the host computer at the beginning of this cycle; a dynamic analysis is performed to obtain the corresponding six-degree-of-freedom aerodynamic load of the floating offshore wind turbine as shown in equation (2): （2） In equation (2), FX, FY, FZ, MX, MY and MZ are the six-degree-of-freedom aerodynamic loads required by the scaled model of the offshore floating wind turbine; F1, F2, F3, F4, F5, F6 and F7 are the thrusts generated by the seven sets of variable-speed fans; a is the distance from variable-speed fan No. 1 to variable-speed fan No. 4; b is the distance from variable-speed fan No. 4 to the center of the supporting base; Step 2: The aerodynamic load decoupling module in the control system of the host computer performs decoupling analysis and calculation. The speed / thrust of the variable speed fan presents a complex nonlinear relationship. During the actual operation, an n-order polynomial relationship is used for fitting to obtain equation (3): （3） In equation (3), F is the thrust generated by the variable speed fan; ω is the speed of the brushless motor; a is the polynomial coefficient; n is the polynomial order; Step 3, when step 1 is implemented, the synchronous trigger device immediately sends a synchronous electrical signal to the six-degree-of-freedom load sensor, collects the analog electrical signal of the actual six-degree-of-freedom aerodynamic load in the previous cycle, and the data acquisition box converts it into a corresponding digital signal, and finally feeds the digital signal back to the aerodynamic load decoupling module in real time through the network port; after receiving the actual six-degree-of-freedom aerodynamic load of the previous cycle, the aerodynamic load decoupling module again calls equation (2) to calculate the thrust actually generated by the seven sets of variable speed fans in the previous cycle, and finally calls equation (3) to calculate the actual speed of the seven sets of brushless motors in the previous cycle; Step 4: The aerodynamic load calculation module calculates the difference between the required speed of the seven brushless motors in this cycle and the actual speed of the seven brushless motors in the previous cycle, calls equation (4) to obtain the deviation value of the speed of the seven variable speed fans, and calls equation (5) to obtain the decimal PWM pulse signals of the seven required speeds in this cycle, and sends them to the controller placed in the cabin; （4） （5） In equations (4)-(5), D is the PWM pulse signal generated by the Ardunio MEGA2560 controller; K P is the proportionality coefficient; K I is the integral coefficient; K D is the differential coefficient; k is the current cycle number; e(k) is the speed deviation signal of this cycle; e(k-1) is the speed deviation signal of the previous cycle; ω(k) is the speed of the brushless motor, ref represents the reference value, and rel represents the measured value; Step 5, after determining that the decimal PWM pulse signal is received, the pneumatic load control module in the controller reads and converts it into seven sets of character strings, and then parses it into corresponding PWM variables and stores them in seven sets of arrays; finally, the seven sets of arrays are output, and the corresponding PWM pins are triggered in turn, and the speeds of the seven sets of brushless motors are controlled through the seven SGN lines of the brushless electronic speed regulator to generate the required thrust; Step 6, continue to repeat steps 1 to 5 until the specified cycle time or the specified number of cycles is reached, and all data during the operation will be stored in the host computer.

2. The control method of the six-degree-of-freedom aerodynamic load simulation system of the offshore floating wind turbine according to claim 1, characterized in that: The variable speed fans are all composed of a brushless motor and a propeller, wherein the brushless motor is powered by three-phase AC power of A, B, and C, and the brushless motor drives the propeller to rotate to generate lift or thrust.

3. The control method of the six-degree-of-freedom aerodynamic load simulation system of the offshore floating wind turbine according to claim 2, characterized in that: The brushless electronic speed regulator has seven groups, each group includes three AC phase lines A, B, C, and two signal lines SGN and GND, wherein the AC phase lines A, B, C are respectively connected to the three-phase lines A, B, and C of the brushless motor, and adopt the AA, BC, and CB phase-changing wiring method to realize the reversal of the brushless motor and generate the required thrust in all directions; the seven GND lines are connected in parallel and connected to the GND pin of the controller at the same time.

4. The control method of the six-degree-of-freedom aerodynamic load simulation system of an offshore floating wind turbine according to claim 3, characterized in that: The fixed bracket includes three support arms and a support base. The three support arms are distributed in a "Y" shape, and the three angles are all 120 degrees. The support base is located at the center of the three support arms.

5. The control method of the six-degree-of-freedom aerodynamic load simulation system of an offshore floating wind turbine according to claim 4, characterized in that: In clockwise direction, the No. 1 support arm is located at the nine o'clock position, and the No. 1 variable speed fan, the No. 7 variable speed fan and the No. 4 variable speed fan are installed on the No. 1 support arm; The second support arm is located at one o'clock, and the second variable speed fan and the fifth variable speed fan are installed on the second support arm; Support arm number three is located at the five o'clock position, and variable speed fan number three and variable speed fan number six are installed on support arm number three.

6. The control method of the six-degree-of-freedom aerodynamic load simulation system of an offshore floating wind turbine according to claim 1, characterized in that: The cabin is connected to the fixed bracket through a slot in a parallel direction, and the internal space is used to place seven sets of brushless electronic speed regulators and controllers; the tower is connected to the cabin through a slot in a vertical direction.

7. The control method of the six-degree-of-freedom aerodynamic load simulation system of an offshore floating wind turbine according to claim 1, characterized in that: The floating platform is connected to the tower through a vertical slot; the mooring anchor chain is connected to the floating platform through a metal ring buckle.

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