An effective wind speed estimation method based on the power feedback of a wind turbine

Abstract

The present invention relates to an effective wind speed estimation method based on the power feedback of a wind turbine. First, the unique wind turbine composite parameter related to the tip speed ratio and its calculation method are determined through theoretical derivation; second, a set of mapping data of the tip speed ratio and the wind turbine composite parameter is obtained through wind tunnel tests or simulation calculations, and polynomial fitting is performed as a prior formula for calculating the real-time tip speed ratio; then, the real-time wind turbine composite parameter value is calculated by combining the wind wheel surface radius, the measured generator speed, and the feedback generator output power, and the real-time tip speed ratio is calculated using the composite parameter value and the prior formula; finally, the real-time effective wind speed of the wind wheel surface is calculated using the tip speed ratio definition. The present invention can replace the wind speed sensors installed at the top or bottom of the wind turbine nacelle, and is not affected by the random spatial distribution of the wind speed, can effectively reduce the manufacturing and operation and maintenance costs of the wind power generation unit, and provides accurate environmental input for the control system.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbines, and in particular to an effective wind speed estimation method based on the power feedback of a wind turbine. Background Art

[0002] A wind turbine is a mechanical device that can effectively convert the wind energy in nature into electrical energy. Different control strategies need to be adopted under different operating conditions to achieve different control objectives. At present, when the ambient wind speed is higher than the cut-in wind speed and lower than the rated wind speed, the generator torque is usually adjusted to achieve the purpose of maximum wind energy capture. However, the adjustment of the control parameters of the wind turbine is related to the wind speed of its working environment. Therefore, a relatively accurate incoming wind speed needs to be provided as the input of the controller to improve its working efficiency. Usually, the wind speed of the wind farm is measured by an anemometer installed on the top or bottom of the nacelle. However, the ambient wind speed of the wind turbine has the characteristics of random distribution in time and space, and the wind speed measured by the anemometer will be affected by the wind turbine disturbance, resulting in the measured wind speed not being directly usable. With the development of wind turbine technology, the structural size of the wind turbine gradually increases, and the swept area of the wind turbine gradually increases, resulting in a further reduction in the usability of the wind speed measured by the anemometer. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an effective wind speed estimation method based on the power feedback of a wind turbine, which can accurately calculate the real-time effective wind speed of the wind turbine blade surface during the maximum power tracking stage and guide the behavior of the controller.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: An effective wind speed estimation method based on the power feedback of a wind turbine, comprising the following steps:

[0005] Step S1: Select the wind turbine model and installation location, and obtain the relevant parameters of the unit and the environmental parameter data;

[0006] Step S2: Determine the composite parameters of the wind turbine related to the tip speed ratio through theoretical derivation;

[0007] Step S3: Obtain a set of mapping data of the tip speed ratio and the wind turbine parameters;

[0008] Step S4: Convert the mapping data of the tip speed ratio and the wind turbine parameters obtained in Step S3 into the mapping data of the tip speed ratio and the composite parameters of the wind turbine determined in Step S2;

[0009] Step S5: Fit a polynomial to the mapping data of the tip speed ratio and the composite parameters of the wind turbine obtained in Step S4, and use the fitting result as the prior formula for calculating the real-time tip speed ratio;

[0010] Step S6: Real-time measurement of ambient temperature T and generator speed ω through sensors Gen and generator output power P Gen , calculate real-time wind turbine composite parameters;

[0011] Step S7: Substituting the real-time wind turbine composite parameters into the a priori formula of step S5 to calculate the real-time tip speed ratio;

[0012] Step S8: Calculate the effective wind speed on the wind wheel surface using the real-time rotor speed and the real-time tip speed ratio obtained in step S7.

[0013] In a preferred embodiment: the unit-related parameters obtained in step S1 include the wind wheel blade length L, hub radius r, blade cone angle γ, optimal blade tip speed ratio λ Opt , gearbox transmission ratio i, generator working efficiency η, generator inertia moment I Gen 、Impeller moment of inertia I Blades and the wheel hub moment of inertia I Hub ;

[0014] The environmental parameter data acquired in step S1 is a comparison table of air density ρ(T,h) and ambient temperature and wind turbine installation altitude.

[0015] In a preferred embodiment: the theoretical derivation in step S2 is as follows:

[0016] The tip speed ratio is defined as:

[0017]

[0018] Where λ is the tip speed ratio, ω Rot is the rotor speed of the wind turbine, R is the radius of the rotor swept surface, and v is the wind speed;

[0019] Combining equation (1) with equation have to:

[0020]

[0021] Where P Rot is the rotor power of the wind turbine, C P (λ,β) is the wind energy utilization coefficient;

[0022] The swept radius of the rotor is calculated by adding the hub radius to the projected length of the blade in the rotor rotation plane:

[0023] R=r+Lcosγ (3)

[0024] During the maximum power capture phase, the blade pitch angle needs to be maintained at the optimal pitch angle. At this time, the wind energy utilization coefficient is regarded as a function of the tip speed ratio. Equation (2) is rewritten as the following formula:

[0025]

[0026] Wherein, H is the integration of parameters directly affected by the tip speed ratio, that is, the only parameter related to the tip speed ratio, and can be specifically expressed as the following formula:

[0027]

[0028] It can be seen from the above formula that the order of magnitude of H(λ) is too small and is not suitable for fitting high-order polynomials. Therefore, the following method is used to correct the above formula:

[0029]

[0030] Wherein, k is a correction factor, and its value is determined by the following formula:

[0031]

[0032] It can be seen from Equation (4) that H is a composite parameter composed of the wind turbine swept area radius, rotor speed, and rotor power. After introducing the correction factor k, it is expressed as the following formula:

[0033]

[0034] In a preferred embodiment: in step S3, a set of mapping data of the tip speed ratio and the wind turbine parameters is obtained by means of a wind tunnel test or simulation calculation with a fixed wind speed and changing the rotor speed;

[0035] The wind turbine parameters in step S3 include: the wind turbine swept area radius, rotor speed, and rotor power.

[0036] In a preferred embodiment: the prior formula fitted in step S5 is expressed as follows:

[0037] λ(R,ω Rot ,P Rot )=a0+a1H+a2H 2 +···+a n H n (9)

[0038] Wherein, a0, a1, a2, …, a n are the coefficients of each term of the polynomial.

[0039] In a preferred embodiment: the implementation manner of step S6 is as follows:

[0040] The real-time rotor speed in equation (8) is calculated by dividing the generator speed by the gearbox ratio:

[0041]

[0042] The real-time rotor power in equation (8) is calculated using the generator output power and the change in mechanical kinetic energy of the wind turbine:

[0043]

[0044] Where ΔE is the change in mechanical kinetic energy of the wind turbine, and Δt is the time step of the controller;

[0045] The change in mechanical kinetic energy of the wind turbine is calculated as follows:

[0046] ΔE=ΔE Gen +ΔE Rot (12)

[0047] In the formula, ΔE Gen is the change in mechanical kinetic energy on the generator side, ΔE Rot is the change in mechanical kinetic energy on the rotor side; they are calculated as follows:

[0048]

[0049]

[0050] In the formula, the subscripts Cur and Last represent the parameters at the current moment and the parameters at the last time the controller was called, respectively;

[0051] The real-time air density is determined by comparing the air density ρ(T,h) obtained in step S1 with the ambient temperature and the wind turbine installation altitude.

[0052] Then, the real-time wind turbine composite parameter H is calculated in combination with equation (8).

[0053] In a preferred embodiment: the rotor speed in step S8 is calculated by equation (10), and the effective wind speed on the wind wheel surface is calculated as follows:

[0054]

[0055] In a preferred embodiment, the swept surface radius of the wind wheel ignores the flexible deformation of the blades and is uniformly calculated using equation (3).

[0056] In a preferred embodiment, considering the change of air density, the real-time rotor power in equation (8) is modified equivalently as follows:

[0057]

[0058] In the formula, ρ test is the air density in the wind tunnel experiment or simulation environment, and ρ(T, h) is the air density at the measured environmental temperature in step S6.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention provides an effective wind speed estimation method based on the power feedback of a wind turbine, which can accurately calculate the real-time effective wind speed of the wind turbine blade surface during the maximum power tracking stage and guide the behavior of the controller.

[0061] The effective wind speed estimation method based on the power feedback of a wind turbine provided by the present invention can effectively replace the anemometer installed on the top or bottom of the nacelle, reducing the manufacturing and operation and maintenance costs of the wind turbine.

[0062] The effective wind speed estimation method based on the power feedback of a wind turbine provided by the present invention is easy to implement and can calculate the effective wind speed of the wind turbine blade surface in real time relatively quickly.

[0063] The effective wind speed estimation method based on the power feedback of a wind turbine provided by the present invention takes into account the air density difference caused by environmental temperature changes, uses the equivalent rotor power to replace the real-time rotor power, eliminates the influence of air density on the rotor power, and the effective wind speed estimation result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a flowchart of the method implementation in the preferred embodiment of the present invention.

[0065] Figure 2 It is the relevant parameters of the target wind turbine in the preferred embodiment of the present invention.

[0066] Figure 3 It is the mapping data of the tip speed ratio and the wind turbine parameters in the preferred embodiment of the present invention.

[0067] Figure 4 It is the least squares fitting curve and the original mapping data in the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0068] The present invention will be further described below with reference to the drawings and embodiments.

[0069] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0070] Note that the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0071] The analysis object of the embodiment of the present invention is a certain type of 5 MW wind turbine.

[0072] As Figures 1-4 shown, the present embodiment provides an effective wind speed estimation method based on the power feedback of a wind turbine, which is used to calculate the effective wind speed of the wind turbine blade surface during the maximum power tracking stage, and further guide the behavior of the controller. The method includes the following steps:

[0073] Step S1: Select the wind turbine model and installation location, and obtain the relevant parameters of the unit and environmental parameter data;

[0074] Step S2: Determine the composite parameters of the wind turbine related to the tip speed ratio through theoretical derivation;

[0075] Step S3: Obtain a set of mapping data of the tip speed ratio and wind turbine parameters;

[0076] Step S4: Convert the mapping data of the tip speed ratio and wind turbine parameters obtained in Step S3 into mapping data of the tip speed ratio and the composite parameters of the wind turbine determined in Step S2;

[0077] Step S5: Fit a polynomial to the mapping data of the tip speed ratio and the composite parameters of the wind turbine obtained in Step S4, and use the fitting result as a prior formula for calculating the real-time tip speed ratio;

[0078] Step S6: Measure the ambient temperature T, the generator speed ωGen, and the generator output power PGen in real time through sensors, and calculate the real-time composite parameters of the wind turbine;

[0079] Step S7: Substitute the real-time composite parameters of the wind turbine into the prior formula in Step S5 to calculate the real-time tip speed ratio;

[0080] Step S8: Calculate the effective wind speed of the wind turbine blade surface using the real-time rotor speed and the real-time tip speed ratio obtained in Step S7.

[0081] In the embodiment of the present invention, the relevant parameters of the unit obtained in Step S1 are as Figure 2 shown.

[0082] Combined with Equation (3), the radius of the wind turbine swept area is calculated to be 62.766 m.

[0083] Combined with Equation (7), the correction factor k value is calculated to be 860.74. The calculation method of the composite parameter composed of the wind turbine swept area radius, rotor speed, and rotor power is as follows:

[0084]

[0085] In step S3, a set of mapping data of tip speed ratio and wind turbine parameters is obtained through simulation calculation. Among them, the wind speed is 10 m / s, the rotor speed ranges from 5 rpm to 25 rpm, and the step size is 0.5 rpm. The calculation results are as Figure 3 shown. During the simulation process, the air density is taken as a constant value of 1.225 kg / m3.

[0086] In step S5, the least squares method is used to fit a polynomial. The sixth-degree polynomial with a higher fitting accuracy is selected as the prior formula. The fitting curve and the data mapping in step S4 are as Figure 4 shown. The prior formula is as follows:

[0087] λ(R, ω Rot , P Rot ) = a0 + a1H + a2H 2 + ··· + a6H 6 (T2)

[0088] In the formula, a0 = 15.23, a1 = -22.52, a2 = 31.04, a3 = -25.17, a4 = 11.24, a5 = -2.562, a6 = 0.231.

[0089] In step S6, the real-time generator speed ωGen and the generator output power PGen are measured in real time. Combined with Equation (10) and Equation (11), the real-time rotor speed ωRot and the rotor power PRot are calculated. Then, combined with Equation (T1), the real-time wind turbine composite parameter H is calculated.

[0090] In step S7, the obtained real-time wind turbine composite parameter H is combined with the prior formula (T2) to calculate the real-time tip speed ratio.

[0091] Finally, substituting the wind turbine swept area radius, the real-time rotor speed ωRot, and the real-time tip speed ratio into Equation (15), the effective wind speed of the real-time wind turbine surface can be obtained.

[0092] The above is only a preferred embodiment of the present invention, and it is not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An effective wind speed estimation method based on the power feedback of a wind turbine, characterized in that: The following steps are involved: Step S1: Select the wind turbine model and installation location, and obtain relevant parameters and environmental parameter data of the unit; Step S2: determining the composite parameters of the wind turbine generator related to the tip speed ratio through theoretical derivation; Step S3: obtaining a set of mapping data of blade tip speed ratio and wind turbine generator parameters; Step S4: converting the mapping data of the tip speed ratio and the wind turbine generator parameter obtained in step S3 into mapping data of the tip speed ratio and the composite parameter of the wind turbine generator determined in step S2; Step S5: fitting a polynomial to the mapping data of the blade tip speed ratio and the composite parameter of the wind turbine generator obtained in step S4, and using the fitting result as a priori formula for calculating the real-time blade tip speed ratio; Step S6: Measure the ambient temperature T, the generator speed ω Gen and the generator output power P Gen in real time through sensors, and calculate the real-time composite parameters of the wind turbine; Step S7: Substituting the real-time wind turbine composite parameters into the a priori formula of step S5 to calculate the real-time tip speed ratio; Step S8: Calculate the effective wind speed on the wind wheel surface using the real-time rotor speed and the real-time blade tip speed ratio obtained in step S7; The theoretical derivation in step S2 is as follows: The tip speed ratio is defined as: where λ is the tip speed ratio, ω Rot is the rotational speed of the rotor of the wind turbine, R is the radius of the wind turbine swept area, and v is the wind speed; Combining Equation (1) and Equation we get: where P Rot is the rotor power of the wind turbine, and C P (λ,β) is the wind energy utilization coefficient; The swept radius of the rotor is calculated by adding the hub radius to the projected length of the blade in the rotor rotation plane: R=r+Lcosγ (3) In the maximum power capture stage, the blade pitch angle needs to be kept at the optimal pitch angle. At this time, the wind energy utilization coefficient is regarded as a function of the tip speed ratio. Equation (2) is rewritten as follows: Where H is the integration of parameters directly affected by the tip speed ratio, that is, the only parameter related to the tip speed ratio, which is specifically expressed as follows: According to the above formula, the order of magnitude of H(λ) is too small and is not suitable for fitting high-order polynomials. Therefore, the following method is used to correct the above formula: Where k is the correction factor, and its value is determined by the following formula: According to equation (4), H is a composite parameter composed of the swept surface radius of the wind rotor, the rotor speed and the rotor power. After introducing the correction factor k, it is expressed as follows:

2. The effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: The relevant parameters of the unit obtained in step S1 include the length L of the wind turbine blade, the hub radius r, the blade cone angle γ, and the optimal tip speed ratio λ Opt , the gearbox transmission ratio i, the generator operating efficiency η, and the generator moment of inertia I Gen , the impeller moment of inertia I Blades and the hub moment of inertia I Hub ; The environmental parameter data acquired in step S1 is a comparison table of air density ρ(T,h) and ambient temperature and wind turbine installation altitude.

3. An effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: The step S3 obtains a set of mapping data between the tip speed ratio and the wind turbine parameters by means of a wind tunnel test or simulation calculation, using a fixed wind speed and changing the rotor speed; The wind turbine generator parameters in step S3 include: rotor swept surface radius, rotor speed and rotor power.

4. An effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: The a priori formula of step S5 fitting is expressed as follows: λ(R, ω Rot , P Rot ) = a0 + a1H + a2H 2 + ··· + a n H n (9) where a0, a1, a2, …, a n are the coefficients of each term of the polynomial.

5. The effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: The implementation of step S6 is as follows: The real-time rotor speed in equation (8) is calculated by dividing the generator speed by the gearbox ratio: The real-time rotor power in equation (8) is calculated using the generator output power and the change in mechanical kinetic energy of the wind turbine: Where ΔE is the change in mechanical kinetic energy of the wind turbine, and Δt is the time step of the controller; The change in mechanical kinetic energy of the wind turbine is calculated as follows: ΔE = ΔE Gen + ΔE Rot (12) where, ΔE Gen is the change in mechanical kinetic energy on the generator side, and ΔE Rot is the change in mechanical kinetic energy on the rotor side; they are calculated respectively as follows: In the formula, the subscripts Cur and Last represent the parameters at the current moment and the parameters at the last time the controller was called, respectively; The real-time air density is determined by comparing the air density ρ(T,h) obtained in step S1 with the ambient temperature and the wind turbine installation altitude. Then, the real-time wind turbine composite parameter H is calculated in combination with equation (8).

6. The effective wind speed estimation method based on the power feedback of a wind turbine according to claim 5, characterized in that: The rotor speed in step S8 is obtained by calculation using Equation (10), and the effective wind speed on the wind turbine plane is calculated as follows:

7. An effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: The radius of the wind turbine swept area ignores the flexible deformation of the blades and is uniformly calculated by Equation (3).

8. The effective wind speed estimation method based on the power feedback of a wind turbine according to claim 1, characterized in that: Considering the change in air density, the real-time rotor power in Equation (8) is equivalently corrected as follows: where ρ test is the air density in the wind tunnel experiment or simulation environment, and ρ(T, h) is the air density at the measured environmental temperature in step S6.

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