Wind generating set clearance control method based on blade aerodynamic principle

Abstract

The invention relates to the technical field of wind turbine generator set clearance control, in particular to a wind turbine generator set clearance control method based on the blade aerodynamic principle, and the method comprises the steps: building a clearance control model according to the blade aerodynamic principle; installing clearance measuring equipment on the wind turbine generator to measure a clearance value; the clearance value is fed back to a clearance control module, and when the clearance value is smaller than a clearance threshold value, the clearance control module adjusts fan parameters according to a clearance control model and controls the clearance value to reach a target clearance value; according to the method, the blade is simplified into a rod model with a fixed rod head according to the pneumatic principle of the blade, the relation between blade tip deformation and pneumatic thrust is obtained, a clearance control model is established, the rotating speed and the variable pitch angle value of an impeller are controlled at the same time through a parallel double-closed-loop control PID control system, the response speed is high, effective control over clearance can be rapidly achieved, and the service life of the blade is prolonged. The clearance control has higher real-time performance and accuracy, the tower sweeping risk is reduced, and the loss of wind energy capture efficiency is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wind turbine clearance control, and in particular to a wind turbine clearance control method based on blade aerodynamic principle. Background Art

[0002] In pursuit of low electricity costs, large-scale wind turbines have become the mainstream trend in the current wind power industry. The increase in wind turbine capacity, larger models, and longer blades have also brought more challenges to the safe and stable operation of the units, such as the risk of wind turbine sweeping the tower. According to the aerodynamic principle of wind turbine blades, wind turbines with lift-type blades rely on the lift of the wind on the blades to drive the blades to rotate around the axis, and the lift source of the blades mainly depends on the aerodynamic characteristics of the blade airfoil. The airfoil design on the outside of the lift-type blade is composed of blade elements with a specific twist angle stacked and covered, such as Figure 1 The stress conditions of each leaf element in the leaf are shown in Figure 2 As shown, the natural wind and the relative wind of the blade element motion synthesize the synthetic wind received by the blade element. The angle between the synthetic wind and the direction of the blade element chord is the angle of attack α, and the angle between the direction of the blade element chord and the direction of impeller rotation is the pitch angle β. The synthetic wind and the blade element generate a lift dF perpendicular to the synthetic wind direction. L and the drag force parallel to the resultant wind direction dF D , dF L and dF D Synthetic gas powered dF R , dF R Decomposed into the driving force dF parallel to the impeller rotation direction Q and the aerodynamic thrust dF perpendicular to the impeller rotation direction T , where the driving force dF Q The blades are driven to rotate, converting wind energy into mechanical energy, and the aerodynamic thrust dF T This will cause the blades to deform, and finally gather all the thrust at the blade root and transmit it to the hub, nacelle and tower, so the aerodynamic thrust dF T Directly affects the headroom value of wind turbines.

[0003] The conventional concept of the relationship between wind speed and headroom is as follows Figure 3As shown in , in the no-wind condition, due to the inclination angle of the nacelle, the lower plane of the impeller is far away from the tower; in the low-wind condition, the aerodynamic thrust generated by each blade element on the blade will cause the blade to deform to a certain extent, and act on the tower at the same time, but the total aerodynamic thrust is small, which is not enough to cause a large deformation of the tower, and the clearance value decreases with the increase of wind speed; in the low-wind condition of negative shear wind, since the wind speed on the plane below the impeller is large and the wind speed on the plane above is small, the aerodynamic thrust below is large, the blade deformation is large, and it is easy to produce a small clearance situation, or even a tower sweeping accident; and in the high-wind condition, During the working condition, although the aerodynamic thrust of the lower plane of the impeller is large and the blades have a large deformation, the deformation is not obvious because the deformation of the blades has reached a certain limit. However, due to the large aerodynamic thrust generated by the impeller, the tower is deformed to a certain extent. The angle between the cabin and the impeller and the horizontal direction increases due to the deformation of the tower, which may increase the headroom. At the same time, as the altitude increases, it is easy to form a positive shear wind condition under normal strong wind conditions, which will cause the aerodynamic thrust on the upper plane of the impeller to be greater than that on the lower plane, thereby increasing the angle between the cabin and the horizontal plane and increasing the headroom. Therefore, due to various reasons such as the aerodynamic characteristics of the fan blades, the aerodynamic characteristics of the tower, and the material characteristics of the blades, it is difficult to establish a more realistic physical model to design the fan so that the fan can completely avoid the risk of tower sweeping. However, the headroom value can be measured by the headroom measurement equipment, and a control strategy can be added according to the physical characteristics of the fan to reduce the probability of tower sweeping safety accidents.

[0004] At present, the common unit clearance control strategy is to reduce the wind energy capture efficiency of the unit by increasing the pitch angle, reduce the unit blade load, thereby reducing blade deformation, and then increase the unit clearance and reduce the risk of tower sweeping. For example, Chinese patent CN117869221A discloses a wind turbine safety control method, system and equipment based on blade tip clearance, and specifically discloses a safety control strategy for achieving clearance by retracting the blades and reducing the generator torque. However, the patent does not establish a physical model of the pitch angle and the impeller speed and the clearance value, so the control accuracy is low and the wind energy capture efficiency is greatly lost. Summary of the invention

[0005] The present invention provides a wind turbine clearance control method based on the blade aerodynamic principle. The method simplifies the blade into a rod model with a fixed rod head according to the blade aerodynamic principle, obtains the relationship between the tip deformation and the aerodynamic thrust, establishes a clearance control model, and simultaneously controls the impeller speed and the pitch angle value through a parallel double closed-loop control PID control system. The response speed is fast, and effective control of the clearance can be quickly achieved. The clearance control has higher real-time and accuracy, reduces the risk of tower sweeping, and reduces the loss of wind energy capture efficiency.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A wind turbine generator clearance control method based on blade aerodynamic principle comprises the following steps:

[0008] S1. Establish a clearance control model based on the blade aerodynamic principle;

[0009] S2. Install clearance measuring equipment on the wind turbine to measure the clearance value;

[0010] S3. Feedback the headroom value to the headroom control module. When the headroom value is less than the headroom threshold, the headroom control module adjusts the fan parameters according to the headroom control model to control the headroom value to reach the target headroom value.

[0011] The specific calculation steps of the clearance control model in S1 are:

[0012] S1.1. According to the aerodynamic principle of blades, the aerodynamic thrust dF on the blades is obtained. T The relationship between the impeller speed ω and the pitch angle p is dF T =f T (ω, p, r), where r is the radius of the blade element;

[0013] S1.2. According to the aerodynamic principle of blades, the aerodynamic thrust moment M on the blades is obtained. T for:

[0014] M T =∫0 R f T (ω, p, r)r;

[0015] S1.3. If the blade is simplified into a rod model with a fixed rod head, the maximum deflection of the rod is the equivalent deformation of the blade tip. According to engineering mechanics, the maximum deflection of the rod is calculated as:

[0016]

[0017] Among them, f max is the maximum deflection of the rod, F is the load of the rod on the rod head, R is the length of the rod, then the moment of force acting on the rod head is F*R, E is the elastic modulus of the rod, and I is the section inertia moment of the rod;

[0018] S1.4, Aerodynamic thrust moment M on the blade T The equivalent moment of the rod acting on the rod head is obtained, and the equivalent deformation of the blade tip and the aerodynamic thrust moment M on the blade are obtained. T The relationship between them is:

[0019]

[0020] Thus, a clearance control model is established.

[0021] The wind turbine parameters in S3 are the pitch angle and the impeller speed. The clearance control module calculates the optimal pitch angle and the impeller speed according to the clearance control model and adjusts them.

[0022] The clearance control module in S3 adjusts the impeller speed and pitch angle value through a parallel dual closed-loop PID control system to control the clearance value.

[0023] The clearance control module controls the impeller speed through the converter.

[0024] The clearance control module controls the pitch angle value through the pitch motor servo.

[0025] The clearance measuring device in S2 is a video clearance measuring device or a millimeter wave radar clearance measuring device.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) According to the aerodynamic principle of blades, the present invention derives the control variables that can control the aerodynamic thrust of the lower plane of the impeller, and then simplifies the blade into a rod model with a fixed rod head, obtains the relationship between the tip deformation and the aerodynamic thrust, and establishes a clearance control model; the clearance control module calculates the optimal pitch angle and impeller speed according to the clearance control model, and simultaneously controls the impeller speed and the pitch angle value through a parallel dual closed-loop control PID control system, with a fast response speed, and can quickly achieve effective control of the clearance, and the clearance control has higher real-time and accuracy, reduces the risk of tower sweeping, and reduces the loss of wind energy capture efficiency.

[0027] (2) In the present invention, the blade is simplified into a rod model with a fixed rod head, and the calculation method of the blade tip deformation is simplified through engineering mechanics calculation, thereby reducing the complexity of the calculation of the blade tip deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of the airfoil of a lift-type blade in the prior art;

[0029] Figure 2 It is a schematic diagram of the force condition of the blade element in the lift-type blade in the prior art;

[0030] Figure 3 It is a relationship diagram between wind speed and headroom value in the prior art;

[0031] Figure 4 It is a curve diagram of the change of lift\drag coefficient water attack angle in the prior art;

[0032] Figure 5 It is a schematic diagram of a blade simplified into a rod model with a fixed rod head in the present invention;

[0033] Figure 6 This is a flow chart of clearance control in the present invention;

[0034] 1-blade, 2-nacelle, 3-impeller, 4-tower. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] The present invention provides a wind turbine generator clearance control method based on blade aerodynamic principle, comprising the following steps:

[0037] S1. Establish a clearance control model based on the blade aerodynamic principle. The specific calculation steps of the clearance control model in this embodiment are as follows:

[0038] S1.1. According to the aerodynamic principle of blades, the aerodynamic thrust dF on the blades is obtained. T Relationship with impeller speed ω and pitch angle p;

[0039] Depend on Figure 1 and Figure 2 It can be seen that the aerodynamic thrust dF on the blade element T and driving force dF Q The calculation formula is as follows:

[0040]

[0041] Where ρ is the air density, t is the blade chord length, δ r is the thickness of the leaf element;

[0042] W is the wind speed of the synthetic wind received by the blade element. The wind speed W of the synthetic wind received by the blade element can be decomposed into the wind speed U of the natural wind and the wind speed V of the relative wind of the blade element movement, that is, W 2 =U 2 +V 2 , The calculation formula of the wind speed V of the blade element relative to the wind is: V = ωr, where ω is the impeller rotation speed and r is the radius of the blade element;

[0043] C L is the lift coefficient of the blade element airfoil, C D is the drag coefficient of the blade-element airfoil. The aerodynamic characteristics of the blade-element airfoil are usually described by the changes of the lift coefficient and drag coefficient of the blade-element airfoil with the angle of attack, such as Figure 4 As shown, it can be expressed by the formula: C L =f cl (α), C D =f cd (α); where f cl is the table-based relationship between the lift coefficient and the angle of attack of the blade element in the laboratory environment test; f cd This is the relationship between the drag coefficient and the angle of attack in the laboratory environment test of the blade element;

[0044] φ is the inflow angle, that is, the angle between the actual airflow velocity (the synthetic wind received by the blade element) and the rotation plane, which is given by Figure 2 It can be seen that the inflow angle φ is the sum of the angle of attack α and the pitch angle β, that is, φ = α + β; the pitch angle β of the blade element is the torsion angle β of the blade element when the blade is designed r (See Figure 1 ) and the sum of the pitch angle p that controls the rotation of the blades, that is, β = β r +p;

[0045] From the above formula, we can get:

[0046]

[0047] Given that the air density ρ and the natural wind speed U are uncontrollable, the blade element twist angle β r , blade chord length t, blade thickness δ r They are all blade characteristic quantities related to the radius r of the blade element and are fixed, so the formula can be simplified as:

[0048] dF T =f T (ω, p, r);

[0049] dF Q =f Q (ω, p, r).

[0050] Thus, the aerodynamic thrust dF on the blade element is obtained T and driving force dF Q Relationship with impeller speed ω and pitch angle p.

[0051] S1.2. According to the aerodynamic principle of blades, the aerodynamic thrust moment M on the blades is obtained. T ;

[0052] According to the aerodynamic principle of blades, the aerodynamic characteristics of the wind acting on the impeller are mainly divided into the aerodynamic thrust perpendicular to the direction of rotation of the impeller and the driving force for driving the impeller to rotate parallel to the direction of rotation of the impeller. The force acting on the impeller can be decomposed into the superposition of the forces acting on the blades, and the superposition of the forces acting on the blades can be obtained by integrating the forces acting on each blade element on the blade.

[0053] Therefore, the aerodynamic thrust moment M on the blade is T for:

[0054] M T =∫0 R dF T r = ∫0 R f T (ω, p, r)r.

[0055] S1.3, simplify the blade into a rod model with a fixed rod head, such as Figure 5As shown in the figure, the maximum deflection of the rod is the equivalent deformation of the blade tip. According to engineering mechanics, the maximum deflection of the rod is calculated as:

[0056]

[0057] Among them, f max is the maximum deflection of the rod, F is the load of the rod on the rod head, R is the length of the rod, then the moment of force acting on the rod head is F*R, E is the elastic modulus of the rod, and I is the section inertia moment of the rod;

[0058] S1.4, Aerodynamic thrust moment M on the blade T The equivalent moment of the rod acting on the rod head is obtained, and the equivalent deformation of the blade tip and the aerodynamic thrust moment M on the blade are obtained. T The relationship between them is:

[0059]

[0060] Thus, a clearance control model is established. From the above formula, it can be seen that the tip deformation is controlled by controlling the impeller speed ω and the pitch angle p, thereby controlling the clearance value.

[0061] Controlling the clearance value of the unit can be achieved by controlling the aerodynamic thrust generated by the wind on the lower plane of the impeller. As long as the aerodynamic thrust of the lower plane of the impeller is controlled, the clearance can be controlled. Therefore, it is only necessary to establish a physical model of the aerodynamic thrust of the lower plane of the impeller and the clearance change, find the control variable that can control the aerodynamic thrust of the lower plane of the impeller and the gain relationship with the clearance, and adjust the clearance value by adjusting the aerodynamic thrust, thereby achieving clearance control. From the above steps, it can be obtained that the control variables of the aerodynamic thrust of the lower plane of the impeller include the impeller speed ω and the pitch angle p, but it is more complicated to construct the relationship between the aerodynamic thrust and the clearance value. Therefore, in this embodiment, the blade is simplified to a rod model with a fixed rod head, and the relationship between the blade tip deformation and the aerodynamic thrust is obtained. The clearance value of the blade can be controlled by controlling the control variable of the aerodynamic thrust.

[0062] S2. Install a clearance measurement device on the wind turbine to measure the clearance value; specifically, the clearance measurement device is a video clearance measurement device or a millimeter wave radar clearance measurement device;

[0063] S3, feeding back the clearance value to the clearance control module. When the clearance value is less than the clearance threshold, the clearance control module adjusts the wind turbine parameters according to the clearance control model to control the clearance value to reach the target clearance value to avoid the wind turbine tower sweeping accident;

[0064] Specifically, the wind turbine parameters are the pitch angle and the impeller speed. The clearance control module calculates the optimal pitch angle and impeller speed according to the clearance control model. The clearance control module adjusts the impeller speed and pitch angle value through the PID control system of parallel double closed-loop control, thereby controlling the clearance value, such as Figure 6 As shown. According to the clearance value measured by the clearance measurement device in the wind turbine, when the clearance value is less than the clearance threshold, the blade tip deformation and aerodynamic thrust curve model are queried to obtain the impeller speed target value and pitch angle target value that reduce the blade tip deformation to increase the clearance, obtain the impeller speed measurement value and pitch angle measurement value, and use the double closed-loop PID impeller speed and pitch angle control logic to control the impeller speed and pitch angle. Furthermore, the clearance control module controls the impeller speed through the converter, and the clearance control module controls the pitch angle value through the pitch motor servo, so that the clearance meets the safety requirements.

Claims

1. A wind turbine clearance control method based on blade aerodynamic principle, characterized in that The following steps are involved: S1. Establish a clearance control model based on the blade aerodynamic principle; S2. Install clearance measuring equipment on the wind turbine to measure the clearance value; S3. Feedback the headroom value to the headroom control module. When the headroom value is less than the headroom threshold, the headroom control module adjusts the fan parameters according to the headroom control model to control the headroom value to reach the target headroom value.

2. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 1 is characterized in that: The specific calculation steps of the clearance control model in S1 are: S1.

1. According to the aerodynamic principle of blades, the aerodynamic thrust dF on the blades is obtained. T The relationship between the impeller speed ω and the pitch angle p is dF = fr(,p,r), where r is the radius of the blade element; S1.

2. According to the aerodynamic principle of blades, the aerodynamic thrust moment M on the blades is obtained. T for: S1.

3. If the blade is simplified into a rod model with a fixed rod head, the maximum deflection of the rod is the equivalent deformation of the blade tip. According to engineering mechanics, the maximum deflection of the rod is calculated as: Among them, fma x is the maximum deflection of the rod, F is the load of the rod on the rod head, R is the length of the rod, then the moment of force acting on the rod head is F*R, E is the elastic modulus of the rod, and I is the section inertia moment of the rod; S1.4, Aerodynamic thrust moment M on the blade T The equivalent moment of the rod acting on the rod head is obtained, and the equivalent deformation of the blade tip and the aerodynamic thrust moment M on the blade are obtained. T The relationship between them is: Thus, a clearance control model is established.

3. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 1, characterized in that: The wind turbine parameters in S3 are the pitch angle and the impeller speed. The clearance control module calculates the optimal pitch angle and the impeller speed according to the clearance control model.

4. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 3 is characterized in that: The clearance control module in S3 adjusts the impeller speed and pitch angle value through a parallel dual closed-loop PID control system to control the clearance value.

5. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 3 is characterized in that: The clearance control module controls the impeller speed through the converter.

6. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 3 is characterized by: The clearance control module controls the pitch angle value through the pitch motor servo.

7. The wind turbine generator clearance control method based on blade aerodynamic principle according to claim 1, characterized in that: The clearance measuring device in S2 is a video clearance measuring device or a millimeter wave radar clearance measuring device.

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