A wind turbine maximum power point tracking control method considering wind shear effect

Abstract

The application discloses a wind turbine maximum power point tracking control method considering wind shear effect. Considering that wind shear effect will affect the aerodynamic performance of different height blade elements, and further cause low wind energy capture efficiency of the wind turbine, the application improves the traditional optimal torque curve, traverses the optimal torque curve under different shear factors offline, and establishes a function relationship between the shear factor and the optimal torque curve; on this basis, the wind speed of the wind wheel disc is measured by using a laser radar anemometer online, the shear factor value is calculated, the shear factor value and the optimal torque curve function relationship established offline are used for dynamically optimizing the torque curve, and the optimal torque curve dynamic correction considering the wind shear effect in the maximum power point tracking stage is realized. The application overcomes the low wind energy capture efficiency phenomenon of the wind turbine caused by the wind shear, and can significantly improve the wind energy capture efficiency compared with the traditional OT method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wind turbine control, in particular to a wind turbine maximum power point tracking control method considering wind shear effect. BACKGROUND

[0002] The wind turbine is in maximum power point tracking operation mode most of the time below the rated wind speed, and the power generation capacity at this stage can account for more than half of the total power generation capacity of the wind turbine. In view of this, the maximum power point tracking of the wind turbine plays an important role in improving the power generation efficiency of the whole machine. Common maximum power point tracking control methods include optimal torque (OT), tip speed ratio and hill climbing method. Among them, the optimal torque method is the most widely used in commercial large wind turbines due to its simple operation and easy engineering deployment, and is also the improvement object.

[0003] However, with the development of large-scale wind turbines, wind shear effect will cause uneven force on the upper and lower disc surfaces of the wind wheel. At present, many scholars have realized that wind shear effect will cause wind turbine output power fluctuation, inaccurate wind speed model modeling, and increased wind turbine load. For the output power fluctuation problem, some scholars propose to use the inertia link of the wind wheel to smooth the power. For the problem of inaccurate wind speed model modeling, an equivalent wind speed model considering wind shear effect is proposed.

[0004] The existing research has not considered the maximum power point tracking control strategy of wind shear effect, and the maximum power point tracking control strategy design still replaces the wind speed on the entire disc surface with the wind speed at the hub. However, with the development of large-scale wind turbines, the wind speed acting on the disc surface of the wind wheel is quite different. From the process of calculating the aerodynamic response of the wind turbine by the blade element momentum theory, the wind energy coefficient C P is the comprehensive result of the aerodynamic performance of all blade elements on the wind turbine blade. When the local wind speed of the blade element changes, the wind energy capture ability of each blade element also changes, resulting in different C P curves under different shear coefficients. Therefore, the maximum power point tracking control strategy design ignoring wind shear effect will reduce the wind energy capture at the maximum power point tracking stage. SUMMARY

[0005] The present application aims to solve the problems existing in the prior art, and provides a wind turbine maximum power point tracking control method considering wind shear effect, which establishes the functional relationship between the shear factor and the optimal torque curve offline, calculates the shear factor value according to the wind speed information measured by the laser radar anemometer, and dynamically optimizes the optimal torque curve accordingly, to improve the adaptability of large wind turbines to high shear low turbulence wind conditions or high shear low turbulence wind conditions, thereby improving the wind energy capture efficiency. This method has good adaptability to turbulent wind conditions, simple logic and wide engineering application space.

[0006] The technical solution for achieving the object of the present application is that, on one hand, a wind turbine maximum power point tracking control method considering wind shear effect is provided, and the method comprises the following steps:

[0007] Step 1, offline establishing a function relationship between different shear factors α and optimal torque curves;

[0008] Step 2, initializing the shear factor α and setting an optimization period T s ;

[0009] Step 3, obtaining wind speed information of a wind wheel disc surface and calculating a current shear factor α value according to the wind speed information;

[0010] Step 4, based on the function relationship established in Step 1, online optimizing the optimal torque curve according to the current shear factor;

[0011] Step 5, recording a current wind wheel rotating speed, calculating an electromagnetic torque T e according to the function relationship established in Step 1;

[0012] Step 6, judging whether the current optimization period T s is ended, if yes, delivering the electromagnetic torque T e calculated in Step 5 to a maximum power point tracking controller, and returning to execute Step 2.

[0013] Further, the function relationship between different shear factors α and optimal torque curves established in Step 1 specifically comprises:

[0014] Step 1-1, obtaining wind turbine structure parameters and environment parameters, wherein the wind turbine parameters comprise a rotating inertia J, a blade radius R, a rated power P N , a rated rotating speed ω N , and the environment parameters comprise an air density ρ;

[0015] Step 1-2, establishing a wind turbine maximum power point tracking control model, fitting out C P curves under different shear factors, and recording corresponding rotating speeds ω g and electromagnetic torques T e ;

[0016] Step 1-3, further fitting out optimal torque curves under different shear factors according to Step 1-2, and establishing a function relationship between the shear factor α and the optimal torque curve T e as follows:

[0017]

[0018] In the formula, k1(α) is a torque gain coefficient, For the optimal torque gain coefficient, p is the air density, R is the wind wheel radius, For the maximum wind energy utilization coefficient, λ opt For the optimal tip speed ratio, ω g For the wind wheel speed, α is the shear factor.

[0019] Further, the shear factor α is initialized to 0.9 in step 2, and the optimization period T s is taken as 10 min.

[0020] Further, the calculation formula of the shear factor α in step 3 is:

[0021]

[0022] In the formula, V z is the wind speed at the highest point of the wind wheel disc, V H is the measured wind speed at the hub of the wind turbine, Z is the vertical height of the highest point of the wind wheel disc from the ground, and H is the vertical height of the hub of the wind turbine from the ground.

[0023] Further, in step 3, the wind speed information of the wind wheel disc is obtained by using a laser radar wind measuring instrument.

[0024] On the other hand, a wind turbine maximum power point tracking control system considering wind shear effect is provided, which comprises the following modules executed in sequence:

[0025] The first module is used to establish the functional relationship between different shear factors α and the optimal torque curve offline;

[0026] The second module is used to initialize the shear factor α and set the optimization period T s ;

[0027] The third module is used to obtain the wind speed information of the wind wheel disc and calculate the current shear factor α value according to the wind speed information;

[0028] The fourth module is used to optimize the optimal torque curve online according to the current shear factor based on the functional relationship established by the first module;

[0029] The fifth module is used to record the current wind wheel speed and calculate the electromagnetic torque T e according to the functional relationship established by the first module;

[0030] The sixth module is used to determine whether the current optimization period T s is ended, if yes, the electromagnetic torque command T e calculated by the fifth module is sent to the maximum power point tracking controller, and the second module is returned to be executed.

[0031] In another aspect, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the wind turbine maximum power point tracking control method considering wind shear effect when executing the computer program.

[0032] In another aspect, a computer readable storage medium is provided, having stored thereon a computer program, wherein the computer program is executable on a processor to implement the wind turbine maximum power point tracking control method considering wind shear effect.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] 1) The present application realizes the dynamic optimization of optimal torque curve considering the influence of shear coefficient, and improves the wind energy capture efficiency of large wind turbine at the maximum power point tracking stage.

[0035] 2) The design logic of the present application is simple and convenient for engineering application, only the control instructions need to be changed, without the need to increase hardware devices, and it shows good adaptability to high shear low turbulence and low shear high turbulence wind conditions.

[0036] The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The flow chart of the wind turbine maximum power point tracking control method considering wind shear effect of the present application.

[0038] Figure 2 The control block diagram of the wind turbine maximum power point tracking control method considering wind shear effect of the present application.

[0039] Figure 3 The rotational speed tracking trajectory comparison chart of the wind turbine maximum power point tracking control method considering wind shear effect of the present application and the conventional optimal torque method. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0041] It should be noted that if the present application examples involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between the components in a certain posture (as shown in the drawings), if the certain posture changes, the directional indications will also change accordingly.

[0042] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, also not within the protection scope required by the present application.

[0043] In combination Figure 1 , the present application provides a wind turbine maximum power point tracking control method considering wind shear effect, the method comprising the following steps:

[0044] Step 1, offline establishing the function relationship between different shear factors α and the optimal torque curve, specifically including:

[0045] Step 1-1, obtaining the wind turbine structural parameters and environmental parameters, the wind turbine parameters including moment of inertia J, blade radius R, rated power P N , rated speed ω N ; the environmental parameters include air density ρ;

[0046] Step 1-2, establishing a wind turbine maximum power point tracking control model, fitting out the C P curve under different shear factors, and recording the corresponding speed ω g , electromagnetic torque T e ;

[0047] Step 1-3, further fitting out the optimal torque curve under different shear factors according to step 1-2, and establishing the function relationship between shear factor α and optimal torque curve T e is:

[0048]

[0049] In the formula, k1(α) is the torque gain coefficient, is the optimal torque gain coefficient, ρ is the air density, R is the wind wheel radius, is the maximum wind energy utilization coefficient, λ opt is the optimal tip speed ratio, ω g is the wind wheel speed, and α is the shear factor.

[0050] Step 2, initializing the shear factor α, and setting the optimization period T s ; here, the shear factor α is preferably initialized to 0.9, and the optimization period T s is 10 min.

[0051] Step 3: Use a lidar anemometer to acquire wind speed information on the wind turbine disk, and calculate the current shear factor α based on the wind speed information. The calculation formula is as follows:

[0052]

[0053] In the formula, V z V is the wind speed at the highest point of the wind turbine disk. H Z represents the measured wind speed at the wind turbine hub, Z represents the vertical height of the highest point of the wind turbine disk from the ground, and H represents the vertical height of the wind turbine hub from the ground.

[0054] Step 4: Based on the functional relationship established in Step 1, optimize the optimal torque curve online according to the current shear factor;

[0055] Step 5: Record the current rotor speed and calculate the electromagnetic torque T based on the functional relationship established in Step 1. e ;

[0056] Step 6, determine the current optimization period T s Is the process complete? If so, then use the electromagnetic torque command T calculated in step 5. e Send the order to the maximum power point tracking controller and return to step 2.

[0057] This invention provides a maximum power point tracking control system for wind turbines that takes into account wind shearing effects, the system comprising the following sequentially executed functions:

[0058] The first module is used to establish the functional relationship between different shear factors α and the optimal torque curve offline;

[0059] The second module is used to initialize the shearing factor α and set the optimization period T. s ;

[0060] The third module is used to obtain wind speed information on the wind turbine disk and calculate the current shear factor α value based on the wind speed information;

[0061] The fourth module is used to optimize the optimal torque curve online based on the functional relationship established in the first module and the current shear factor.

[0062] The fifth module records the current rotor speed and calculates the electromagnetic torque T based on the functional relationship established in the first module. e ;

[0063] The sixth module is used to determine the current optimization period T. s Is it finished? If finished, then send the electromagnetic torque command T calculated by the fifth module. e The order is sent to the maximum power point tracking controller, and the process returns to execute the second module.

[0064] The specific limitation of the wind turbine maximum power point tracking control system considering wind shear effect can refer to the limitation of the wind turbine maximum power point tracking control method considering wind shear effect in the above, which will not be repeated here. Each module in the wind turbine maximum power point tracking control system considering wind shear effect can be realized by software, hardware and combination thereof in whole or in part. The above modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operation corresponding to each module.

[0065] The application provides a computer device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor realizes the following steps when executing the computer program:

[0066] Step 1, offline establishment of the function relationship between different shear factors α and the optimal torque curve;

[0067] Step 2, initialization of the shear factor α and setting of the optimization period T s ;

[0068] Step 3, acquisition of the wind speed information of the wind wheel disc surface and calculation of the current shear factor α value according to the wind speed information;

[0069] Step 4, online optimization of the optimal torque curve according to the current shear factor based on the function relationship established in step 1;

[0070] Step 5, recording of the current wind wheel rotating speed and calculation of the electromagnetic torque T e according to the function relationship established in step 1;

[0071] Step 6, judgment of whether the current optimization period T s is ended, if yes, the electromagnetic torque instruction T e calculated in step 4 is sent to the maximum power point tracking controller, and the step 2 is returned to be executed.

[0072] The specific limitation of each step can refer to the limitation of the wind turbine maximum power point tracking control method considering wind shear effect in the above, which will not be repeated here.

[0073] The application provides a computer readable storage medium, which stores a computer program, and the computer program realizes the following steps when being executed by a processor:

[0074] Step 1, offline establishment of the function relationship between different shear factors α and the optimal torque curve;

[0075] Step 2, initialization of the shear factor α and setting of the optimization period T s ;

[0076] Step 3, obtaining the wind speed information of the wind wheel surface, and calculating the current shear factor a value according to the wind speed information;

[0077] Step 4, based on the function relationship established in step 1, the optimal torque curve is optimized online according to the current shear factor;

[0078] Step 5, record the current wind wheel speed, and calculate the electromagnetic torque T e according to the function relationship established in step 1;

[0079] Step 6, judge whether the current optimization period T s is ended, if yes, the electromagnetic torque T e calculated in step 4 is sent to the maximum power point tracking controller, and step 2 is returned to execute.

[0080] The specific definition of each step can be referred to the definition of the wind turbine maximum power point tracking control method considering wind shear effect in the above, which will not be repeated here.

[0081] The present application will be further described in detail below in combination with embodiments.

[0082] Embodiment

[0083] The simulation model uses the open source professional wind turbine simulation software FAST (Fatigue, Aerodynamics, Structures, and Turbulence) provided by the U.S. Department of Energy Renewable Energy Laboratory (NREL). The wind turbine model corresponds to the 5MW Baseline model developed by NREL, and the related parameters are as follows.

[0084] Table 1 Main parameters of NREL 5MW Baseline wind turbine

[0085]

[0086] First, NREL TurSim is used to generate a three-dimensional disc surface wind speed sequence of 10 min time scale conforming to Kaimal power spectrum, and its turbulence characteristics are: shear factor fluctuates within 0-0.5, average wind speed fluctuates within 4-7 m / s (step length is 1 m / s), turbulence intensity level is at A-C level, integral scale fluctuates within 100-500 m (step length is 100 m). Different shear factors, average wind speeds, turbulence intensities and integral scales are arranged and combined to form 360 turbulence wind speed sequences.

[0087] Based on the professional wind turbine simulation software FAST, the wind turbine is modeled, and the above constructed turbulence wind speed sequence is used to fit C PThe curve is fitted with the optimal torque curve, and the function relationship between the shear factor a and the optimal torque curve is established offline for sample data;

[0088]

[0089] Due to the high shear effect, the equivalent wind speed on the disc surface of the wind wheel is greater than the average wind speed at the hub, so the optimal torque curve will be upwardly offset compared with the traditional optimal torque curve. Due to the low shear effect, the equivalent wind speed on the disc surface of the wind wheel is less than the average wind speed at the hub, so the optimal torque curve will be downwardly offset compared with the traditional optimal torque curve. Therefore, the function relationship between different shear factors and the optimal torque curve is as shown in Figure 2

[0090] The laser radar wind measuring instrument is used to obtain three-dimensional wind speed information, and the current shear factor value a is calculated to be 0.3 by using the wind speed information. According to the current shear factor value a, the torque gain coefficient adjustment k1(a) is adjusted to 1.1, the current optimal torque curve is optimized to the torque curve under the high shear factor, and the electromagnetic torque command is issued according to the current wind wheel speed.

[0091] A group of turbulent wind speed sequences are generated by NREL TurSim as simulation wind conditions. The traditional optimal torque curve and the maximum power point tracking control strategy considering wind shear effect are simulated in the professional simulation software FAST, and the wind energy capture efficiency of the large wind turbine is calculated to verify the effectiveness of the maximum power point tracking control strategy considering wind shear effect. The simulation results of the two maximum power point tracking control strategies are shown in Table 2.

[0092] Table 2 Comparison of different maximum power point tracking control methods

[0093]

[0094] As can be seen from the above table, compared with the traditional optimal torque method, the wind energy capture efficiency of the present method is higher, which is increased by 1.4%. Due to the high shear effect, the equivalent wind speed on the disc surface of the wind wheel is greater than the average wind speed at the hub, so the reference speed is also greater than the optimal speed under the traditional optimal torque. As shown in Figure 3 The actual speed tracking curve of the improved method of the present application will be floating above the traditional optimal torque method as a whole.

[0095] It should be noted that the above embodiments illustrate the present application rather than limit the present application, and alternative embodiments can be designed by those skilled in the art without departing from the scope of the appended claims. Any changes or substitutions within the scope of the technology disclosed by the present application can be easily conceived by those skilled in the art, and should be covered within the protection scope of the present application.​

Claims

1. A wind turbine maximum power point tracking control method considering wind shear, characterized by, The method comprises the following steps: Step 1, offline establishing the function relationship between different shear factors alpha and the optimal torque curve; Step 2, initialize shear factor a and set optimization period T s ; Step 3, obtaining the wind speed information of the wind wheel disc surface, and calculating the current shear factor alpha value according to the wind speed information; Step 4, based on the function relationship established in step 1, the optimal torque curve is optimized online according to the current shear factor; Step 5, record the current wind wheel rotating speed, according to the function relationship established in step 1, calculate the electromagnetic torque T e ; Step 6, judge whether the current optimization period T is finished, if finished, the electromagnetic torque instruction T calculated in step 5 is sent to the maximum power point tracking controller, and the step 2 is returned to execute. s Step 6, judge whether the current optimization period T is finished, if finished, the electromagnetic torque instruction T calculated in step 5 is sent to the maximum power point tracking controller, and the step 2 is returned to execute. e Step 6, judge whether the current optimization period T is finished, if finished, the electromagnetic torque instruction T calculated in step 5 is The function relationship between different shear factors alpha and the optimal torque curve established in step 1 specifically comprises: Step 1-1, obtaining fan structure parameters and environment parameters, wherein the fan structure parameters include moment of inertia J, blade radius R, rated power P N , rated rotating speed ω N ; the environment parameters include air density ρ; Step 1-2, establish the fan maximum power point tracking control model, fit out the C P curve under different shear factors, and record the corresponding rotating speed ω g , electromagnetic torque T e ; Step 1-3, according to step 1-2, the optimal torque curve under different shear factors is further fitted, and the function relationship between the shear factor a and the optimal torque curve T e is established as: where k1(a) is a torque gain coefficient, is the optimal torque gain coefficient, p is the air density, R is the rotor radius, is the maximum wind energy utilization coefficient, λ opt is the optimal tip speed ratio, ω g is the rotor speed, a is the shear factor.

2. The wind turbine maximum power point tracking control method considering wind shear effect according to claim 1, wherein, The shear factor alpha is initialized to 0.9 in step 2, the optimization period T s Take 10 min.

3. The wind turbine maximum power point tracking control method considering wind shear effect according to claim 2, characterized in that, The calculation formula of the shear factor alpha in step 3 is: wherein V z is the wind speed at the highest point of the rotor disc, V H is the measured wind speed at the hub of the wind turbine, Z is the vertical height of the highest point of the rotor disc above ground, and H is the vertical height of the hub of the wind turbine above ground.

4. The wind turbine maximum power point tracking control method considering wind shear effect according to claim 3, characterized in that, In step 3, the wind speed information of the wind wheel disc surface is obtained by using a laser radar wind measuring instrument.

5. A wind turbine maximum power point tracking control system taking into account wind shear effects based on the method of any of claims 1 to 4, characterized in that, The system comprises the following modules which are executed in sequence: The first module is used for offline establishing the function relationship between different shear factors alpha and the optimal torque curve; A second module is configured to initialize a shear factor a and set an optimization period T s ; The third module is used for obtaining the wind speed information of the wind wheel disc surface, and calculating the current shear factor alpha value according to the wind speed information; The fourth module is used for establishing the function relationship based on the first module, and optimizing the optimal torque curve online according to the current shear factor; A fifth module is configured to record the current wind wheel rotating speed, and calculate the electromagnetic torque T according to the function relationship established by the first module e ; A sixth module is configured to determine whether the current optimization period T is ended, and if the current optimization period T is ended, the electromagnetic torque instruction T calculated by the fifth module is sent to a maximum power point tracking controller, and the second module is returned to be executed. s A sixth module is configured to determine whether the current optimization period T is ended, and if the current optimization period T is ended, the electromagnetic torque instruction T calculated by the fifth module is sent to a maximum power point tracking controller, and the second module is returned to be executed. e A sixth module is configured to determine whether the current 6. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the method as claimed in any one of claims 1 to 4.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The computer program is executed by the processor to realize the method as claimed in any one of claims 1 to 4.

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