Wind speed estimation method for wind turbine generators under limit control

Abstract

This invention discloses a wind speed estimation method for wind turbine generators under limit control. Addressing the difficulty in estimating wind speed under limit control, this method reveals the essential mapping relationship between pitch angle and wind speed. Based on a polynomial fitting function of this mapping relationship, it effectively estimates the real-time wind speed of wind turbine generators under limit control using the pitch angle value, improving the wind speed estimation capability under multiple operating conditions and ensuring the safe and stable operation of wind turbine generators. Compared with existing methods, this method has the following advantages: (1) simple structure, requiring no additional hardware modifications; (2) strong versatility, applicable to different types of variable-speed, variable-pitch wind turbine generators; (3) high accuracy and small error in wind speed estimation. This method has strong practical engineering value.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation technology, specifically relating to a method for estimating wind speed of wind turbine generator sets under limit control. Background Technology

[0002] As is well known, wind energy is a renewable energy resource with fluctuating and random characteristics, with wind speed and direction varying randomly. Real-time wind speed information is crucial for the control of wind turbine generators, and generally, wind turbine generators need to be equipped with wind speed measurement devices. However, due to the large swept area of ​​the wind turbine blades, the wind speed varies at different locations within the swept area. Therefore, directly measuring the effective wind speed of the wind turbine blades is almost impossible, making it necessary to indirectly estimate the effective wind speed of the wind turbine blades.

[0003] Limit control refers to the control method where the output power of a wind turbine generator does not exceed a certain upper limit. Limit control is one of the conventional control methods for wind turbine generators. When the wind speed rises above the rated wind speed, the wind turbine generator needs to limit its output power to not exceed the rated power. When the higher-level dispatching agency issues an active power command, the wind turbine generator needs to limit its output power to not exceed the commanded value. Under limit control, the wind turbine generator's speed is usually at the rated value, requiring pitch control to further limit its output power.

[0004] Existing wind speed estimation methods for wind turbine generators are mostly based on state observation, estimating wind speed by considering the motion equations of the rotating mass of the wind turbine generator, i.e., using rotational speed information to estimate wind speed. However, this method is not applicable to limit control conditions. Under limit control, the rotational speed of the wind turbine generator is usually at its rated value, and the rotational speed information cannot be used as an effective state variable for wind speed estimation. Therefore, it is necessary to conduct research on wind speed estimation methods for wind turbine generators under limit control to achieve wind speed estimation under multiple operating conditions, thereby ensuring the safe and stable operation of wind turbine generators. Summary of the Invention

[0005] The purpose of this invention is to provide a wind speed estimation method for wind turbine generators under limit control that is simple in structure and has good performance, overcoming the shortcomings of the existing technology that cannot effectively estimate the wind speed of wind turbine generators under limit control conditions.

[0006] To achieve the above-mentioned objectives, this method adopts the following technical solution:

[0007] A method for estimating wind speed of a wind turbine generator under limit control, characterized in that the system executing the method includes a pitch angle sampling module, a fitting coefficient query module, a wind speed estimation module, and a continuousization module;

[0008] The pitch angle sampling module samples the pitch angle value in variable pitch control, and outputs the sampling result to the wind speed estimation module.

[0009] The fitting coefficient query module uses the limit control reference value P issued by the wind farm control center or the superior dispatching agency. lim Query the fitting coefficients α of each order of the fitting polynomial used for wind speed estimation. i The query results are output to the wind speed estimation module;

[0010] The wind speed estimation module uses the pitch angle values ​​obtained from each sample to generate a fitting polynomial, which estimates the discrete value of the current effective wind speed of the wind turbine generator. The estimated discrete value is then output to the continuous transformation module. The specific calculation method is as follows:

[0011]

[0012] Among them, v dis For the discretized wind speed estimated by the wind speed estimation module, α i To fit the polynomial of each order of fitting coefficients, β is the pitch angle value sampled by the pitch angle value sampling module;

[0013] The continuous processing module performs continuous processing on the discretized wind speed results output by the wind speed estimation module through a sliding time window. The specific calculation method is as follows:

[0014]

[0015] Among them, v con The wind speed estimate is obtained after continuous processing via a sliding time window, where t0 is the current time and t... w Let t be the length of the sliding time window, and t be the integration variable.

[0016] In the above technical solution, the specific process of solving for the fitting coefficients of each order of the fitting polynomial used for wind speed estimation is as follows:

[0017] (a) Based on the wind turbine characteristic function, the relationship between wind speed and blade pitch angle under a certain limit control reference value is established, as shown in the following formula:

[0018]

[0019] Where ρ is air density, S is swept area, v is wind speed, and C is air density. p Let ω be the characteristic function of the wind turbine. max Where r is the rated rotational speed, r is the equivalent radius of the blade, and β is the pitch angle.

[0020] (b) Solve formula (3) by numerical calculation to obtain the mapping relationship between wind speed v and blade pitch angle β under a certain limit control reference value;

[0021] (c) Change the limit control reference value and repeat steps (a) and (b) to obtain the mapping relationship between wind speed v and blade pitch angle β under different limit control reference values;

[0022] (d) Perform function fitting on the mapping relationship between wind speed v and pitch angle β under different limit control reference values ​​obtained in step (c) to obtain the fitting coefficients of each order of the fitting polynomial used to describe the mapping relationship between wind speed v and pitch angle β under different limit control reference values.

[0023] A fourth-order polynomial is used for function fitting, based on the least squares curve fitting principle. The fitting result is the fitting coefficients α of each order of the fitting polynomial. i .

[0024] This invention reveals the essential mapping relationship between pitch angle and wind speed under limit control. Based on the polynomial fitting function of the mapping relationship, the real-time wind speed of the wind turbine under limit control is effectively estimated using the pitch angle, improving the wind speed estimation capability of the wind turbine under multiple operating conditions and ensuring the safe and stable operation of the wind turbine. Compared with existing methods, this method has the following advantages: (1) simple structure, requiring no additional hardware modification; (2) strong versatility, applicable to different types of variable speed and variable pitch wind turbines; (3) high accuracy and small error in wind speed estimation. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating a specific example of the wind speed estimation method for wind turbine generators under limit control according to the present invention.

[0026] Figure 2 A mapping diagram between pitch angle and wind speed under a certain limit control reference value (2MW).

[0027] Figure 3 This diagram shows the mapping relationship between pitch angle and wind speed under different limit control reference values.

[0028] Figure 4 This is a graph showing the fitting effect of the mapping relationship between pitch angle and wind speed under a certain limit control reference value (2MW). In the graph, the solid line represents the original mapping relationship data, the circles represent the sampled point data, and the dashed line represents the fitted polynomial data.

[0029] Figure 5 The simulation waveforms for wind speed estimation using the method described in this invention are shown below, from top to bottom: wind speed, rotational speed, propeller pitch angle, and output power. In the wind speed waveform, the solid line represents the actual wind speed, and the dashed line represents the estimated wind speed using the method of this invention.

[0030] Figure 6The simulation waveforms for wind speed estimation using the method described in this invention are shown below, from top to bottom: wind speed, rotational speed, propeller pitch angle, and output power. In the wind speed waveforms, solid lines represent the actual wind speed, and dashed lines represent the estimated wind speed using the method described in this invention. Detailed Implementation

[0031] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The system implementation of the wind speed estimation method for wind turbine generators under limit control in this invention is as follows: Figure 1 As shown, it includes a pitch angle sampling module, a fitting coefficient query module, a wind speed estimation module, and a continuous transformation module. The wind speed estimation method for wind turbine generators under limit control in this invention includes the following steps:

[0033] The pitch angle value in variable pitch control is sampled by the pitch angle value sampling module, and the sampling result is output to the wind speed estimation module.

[0034] In the fitting coefficient query module, the limit control reference value P issued by the wind farm control center or the superior dispatching agency is used. lim Query the fitting coefficients α of each order of the fitting polynomial used for wind speed estimation. i The query results are output to the wind speed estimation module.

[0035] The fitting coefficients α of each order of the fitting polynomial used for wind speed estimation i The solution process is as follows:

[0036] (a) Based on the wind turbine characteristic function, the relationship between wind speed and blade pitch angle under a certain limit control reference value is established, as shown in the following formula:

[0037]

[0038] Where ρ is air density, S is swept area, v is wind speed, and C is air density. p Let ω be the characteristic function of the wind turbine. max Where r is the rated rotational speed, r is the equivalent radius of the blade, and β is the pitch angle.

[0039] (b) By solving formula (1) numerically, the mapping relationship between wind speed v and blade pitch angle β under a certain limit control reference value is obtained, such as Figure 2 As shown, under a certain limit control reference value, there is a unique mapping relationship between wind speed v and pitch angle β, and the higher the wind speed, the larger the pitch angle value.

[0040] (c) By changing the limit control reference value and repeating steps (a) and (b), the mapping relationship between wind speed v and pitch angle β under different limit control reference values ​​can be obtained, such as... Figure 3 As shown;

[0041] (d) For the mapping relationship between wind speed v and pitch angle β under different limit control reference values ​​established in step (c), a fourth-order polynomial is used for function fitting. The mathematical basis of the fitting is the least squares curve fitting principle. The fitting results are the fitting coefficients α of each order of the fitting polynomial. i ; Figure 4 The diagram shows the fitting effect of the mapping relationship between pitch angle and wind speed under a specific limit control reference value (2MW). The solid line represents the original mapping relationship data, the circles represent the sampling point data, and the dashed line represents the fitted polynomial data. It can be seen that the fitted data basically overlaps with the original data, and the fitting effect is good.

[0042] Through the above steps, the fitting coefficients of each order of the fitting polynomial used to describe the mapping relationship between wind speed v and pitch angle β under different limit control reference values ​​can be obtained for reference, as shown in the table below.

[0043]

[0044]

[0045]

[0046] In the wind speed estimation module, the pitch angle values ​​obtained from each sample are used to generate a fitting polynomial using fitting coefficients of various orders. This polynomial is then used to estimate the discrete values ​​of the current effective wind speed of the wind turbine generator. The estimated discrete values ​​are output to the continuous processing module. The specific calculation method is as follows:

[0047]

[0048] Among them, v dis For the discretized wind speed estimated by the wind speed estimation module, α i The coefficients for each order of the fitting polynomial are β, where β is the pitch angle value sampled by the pitch angle sampling module.

[0049] In the continuous processing module, the discretized wind speed results output by the wind speed estimation module are processed continuously using a sliding time window (in this embodiment, the sliding window is 100ms, and the specific length of the window period can be adjusted as needed). The specific calculation method is as follows:

[0050]

[0051] Among them, v conThe wind speed estimate is obtained after continuous processing via a sliding time window, where t0 is the current time and t is the integral variable.

[0052] See Figure 5 and Figure 6 The wind speed estimation method for wind turbine generators under limit control in this invention can smoothly and quickly track the actual wind speed under both step and random wind speed conditions, with only a small amount of error in the transient process. This verifies that the proposed method can effectively estimate the real-time wind speed of wind turbine generators under limit control, and effectively ensure the safe and stable operation of wind turbine generators.

[0053] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for estimating wind speed of a wind turbine generator under limit control, characterized in that... The system for executing the method includes a pitch angle sampling module, a fitting coefficient query module, a wind speed estimation module, and a continuous conversion module; The pitch angle sampling module samples the pitch angle value in variable pitch control, and outputs the sampling result to the wind speed estimation module. The fitting coefficient query module uses the limit control reference value P issued by the wind farm control center or the superior dispatching agency. lim Query the fitting coefficients α of each order of the fitting polynomial used for wind speed estimation. i The query results are output to the wind speed estimation module; The specific process for solving the fitting coefficients of each order of the fitting polynomial used for wind speed estimation is as follows: (a) Based on the wind turbine characteristic function, the relationship between wind speed and blade pitch angle under a certain limit control reference value is established, as shown in the following formula: (3) Where ρ is air density, S is swept area, v is wind speed, and C is air density. p Let ω be the characteristic function of the wind turbine. max Where r is the rated rotational speed, r is the equivalent radius of the blade, and β is the pitch angle. (b) Solve formula (3) by numerical calculation to obtain the mapping relationship between wind speed v and blade pitch angle β under a certain limit control reference value; (c) Change the limit control reference value and repeat steps (a) and (b) to obtain the mapping relationship between wind speed v and pitch angle β under different limit control reference values; (d) Perform function fitting on the mapping relationship between wind speed v and pitch angle β under different limit control reference values ​​obtained in step (c), and obtain the fitting coefficients α of each order of the fitting polynomial used to describe the mapping relationship between wind speed v and pitch angle β under different limit control reference values. i ; The wind speed estimation module uses the sampled pitch angle values ​​and various order fitting coefficients to generate a fitting polynomial to estimate the discrete values ​​of the current effective wind speed of the wind turbine generator. The estimated discrete values ​​are then output to the continuous transformation module. The specific calculation method is as follows: (1) Among them, v dis For the discretized wind speed estimated by the wind speed estimation module, α i To fit the polynomial of each order of fitting coefficients, β is the pitch angle value sampled by the pitch angle value sampling module; The continuous processing module performs continuous processing on the discretized wind speed results output by the wind speed estimation module through a sliding time window. The specific calculation method is as follows: (2) Among them, v con The wind speed estimate is obtained after continuous processing via a sliding time window, where t0 is the current time and t... w Let t be the length of the sliding time window, and t be the integration variable.

2. The wind speed estimation method for wind turbine generator sets under limit control according to claim 1, characterized in that: A fourth-order polynomial was used to fit the mapping relationship between wind speed v and blade pitch angle β. The mathematical basis of the fitting was the least squares curve fitting principle. The fitting results are the fitting coefficients α of each order of the fitting polynomial. i .

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