An integrated control method for a passive yaw type wind turbine

Abstract

An integrated control method for a passive yaw type wind turbine. The present invention avoids the initial yaw stage of passive yaw and combines its large-angle yaw with electromagnetic stall. Compared with the prior art, the present invention has the following advantages: The present invention combines active electromagnetic stall control and passive yaw protection to prevent the active control speed from entering the uncontrollable area and causing the wind turbine to overspeed; The present invention provides a basis or calculation method for entering the yaw + stall control operation stage from low speed, and also provides a basis or calculation method for returning from the yaw + stall control to the low-speed operation stage. In engineering applications, a basic model can be established according to the conditions for entering each operation stage disclosed in the present invention, or the wind speed can be used as a reference as the judgment condition for entering each stage.

Description

Technical Field

[0001] The present invention relates to a control method for a wind turbine, and particularly to a control method for a passive yaw type wind turbine. Background Art

[0002] Both passive yaw and electromagnetic stall are common protection methods for small wind turbines. Passive yaw is a mechanical protection method for changing the windward angle of the blade, and electromagnetic stall is a protection method for applying a reverse torque to the generator.

[0003] Generally, when the blade is at a low tip speed ratio, the blade thrust coefficient Ct value is relatively low. Therefore, passive yaw starts to provide protection only at high wind speeds and high rotational speeds. And the electromagnetic stall control is restricted by the torque of the motor. The wind turbine torque will be less than the motor torque only when the blade is in a yaw state at a low rotational speed or a high wind speed. Therefore, the electromagnetic stall control is also limited by various operating conditions.

[0004] Since the wind energy absorbed by the wind turbine is proportional to the effective area of the wind wheel, the area S = πR 2 ×cosθ, where R represents the radius of the wind wheel and θ represents the yaw angle. In the initial yaw stage of the yaw type wind turbine, that is, when the yaw angle is relatively small, the slope of the decrease of cosθ is small. In addition, due to the mechanical hysteresis, the coordination between the electromagnetic stall control and the passive yaw of the current yaw type wind turbine generator set is prone to be out of sync. Often at high wind speeds, the rotational speed of the fan fluctuates violently and seriously exceeds the speed, imposing a large impact load on the mechanical structural components, and serious accidents such as the fracture of components such as the tower or blade are likely to occur. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that in the initial yaw stage of the yaw type wind turbine, the coordination between the electromagnetic stall control and the passive yaw is prone to be out of sync.

[0006] To solve the above technical problem, the technical solution of the present invention is to provide a comprehensive control method for a passive yaw type fan, which is characterized in that the Cq, Ct-λ curve graph of the blade is divided into 4 intervals, which are respectively defined as operating region I, operating region II, operating region III, and operating region IV. Among them, operating region I corresponds to the maximum power tracking stage, operating region II corresponds to the high constant speed operation stage, operating region III corresponds to the low constant speed operation stage, and operating region IV corresponds to the yaw plus stall control operation stage. Cq represents the blade moment coefficient, Ct represents the blade thrust coefficient, and λ represents the tip speed ratio. Then the comprehensive control method includes the following steps:

[0007] Step 1: When the current wind speed is less than the rated wind speed, the passive yaw type wind turbine enters the maximum power tracking stage and enters operating region I. To ensure that when the passive yaw type wind turbine operates in operating region I, it will not enter the passive yaw protection state, and the controller of the passive yaw type wind turbine will not perform active electromagnetic stall control, and the rotational speed of the wind turbine is maintained at an optimal tip speed ratio λ state. Among them, when the passive yaw type wind turbine outputs power at the best efficiency at a certain wind speed, the power is equal to the rated power, then the current wind speed is defined as the rated wind speed;

[0008] In the maximum power tracking stage, if the current wind speed exceeds the rated wind speed, and if the current wind speed is slightly higher than the rated wind speed, then control the passive yaw type wind turbine to operate at the rated power, and at the same time control the passive yaw type wind turbine to operate below the maximum rotational speed point, that is, enter operating region II, and enter Step 2;

[0009] Step 2: The passive yaw type wind turbine enters the high constant speed operation stage and operates in operating region II:

[0010] In the high constant speed operation stage, when the wind speed further increases, then adjust the rotational speed of the wind turbine or keep the rotational speed of the wind turbine constant, so that the tip speed ratio λ moves in the decreasing direction from the optimal value. The Ct value decreases but the curve is relatively gentle, and the passive yaw is in the starting yaw or non-yaw state. The Cq value increases and the curve is relatively steep, and the torque of the passive yaw type wind turbine increases rapidly;

[0011] When the wind speed further increases again: If the wind turbine torque is close to the set torque, then immediately greatly reduce the target rotational speed and increase the generator torque, so that the passive yaw type wind turbine quickly crosses the region below region II to operating region III, and enter Step 3;

[0012] In the high constant speed operation stage, when the wind turbine torque is less than the set torque, then return to Step 2;

[0013] Step 3: The passive yaw type wind turbine enters the low constant speed operation stage and operates in operating region III. At this time, increase the rotational speed of the passive yaw type wind turbine. According to the current air density ρ, wind speed V, wind turbine area S = πR 2 ×cosθ and the set minimum thrust torque Fin, according to the wind turbine thrust torque calculation formula calculate the minimum Ct value. According to this minimum Ct value, reverse look up the λ curve chart to know λ. λ is the tip speed ratio, so as to determine the minimum target rotational speed of the generator that needs to be increased, that is, the rotational speed of the large angle yaw of the wind turbine, and increase the rotational speed of the wind turbine to this rotational speed; while increasing the rotational speed of the wind turbine, increase the thrust torque of the wind turbine, so that the wind turbine yaws at a large angle, that is, enter operating region IV, and enter Step 4;

[0014] In the low constant speed operation stage: when the wind turbine torque is less than the set torque, return to step 2; when the wind turbine torque is equal to the set torque, the passive side deflection type wind turbine remains in the low constant speed operation stage;

[0015] Step 4, the passive side deflection type wind turbine enters the side deflection plus stall control operation stage and operates in operation area IV:

[0016] The wind turbine thrust moment at the maximum side deflection angle is still greater than the return moment of the tail rudder; in operation area IV, after the wind speed increases, the tip speed ratio decreases, which in turn causes the Ct value to decrease, but the decreasing proportion of the Ct value is not as large as that of V 2 The decreasing proportion is large. When the wind speed increases, the total wind turbine thrust increases and remains at the maximum side deflection angle;

[0017] In operation area IV, when the wind speed decreases, the tip speed ratio becomes larger, which in turn causes the Ct value to become larger. The increasing proportion of the Ct value is smaller than that of V 2 The increasing proportion is small. When the wind speed decreases to a certain limit value, the side deflection angle θ begins to decrease; when the side deflection angle θ drops to the set value, due to the mechanical hysteresis of the side deflection, the rotational speed will quickly run to the target rotational speed before the side deflection returns, and return to operation area III, entering step 3.

[0018] Preferably, the wind turbine torque is calculated by any one of the following two methods:

[0019] Method 1) According to the Cq, Ct-λ curve graph, the Cq value can be known. Then, based on the air density ρ, the wind turbine radius R, the wind turbine area S, the wind speed V, and the Cq value, according to the wind turbine moment calculation formula Twind = 0.5×ρ×S×V 2 ×R×Cq, the wind turbine torque is calculated;

[0020] Method 2) The wind turbine torque is directly calculated through the generator power and the wind turbine rotational speed.

[0021] The present invention avoids the initial side deflection stage of passive side deflection and combines its large angle side deflection with electromagnetic stall. Compared with the prior art, the present invention has the following advantages:

[0022] 1) The present invention combines active electromagnetic stall control and passive side deflection protection to avoid the active control rotational speed from entering the uncontrollable area and causing the wind turbine to overspeed.

[0023] 2) The present invention provides a basis or calculation method for entering the side deflection + stall control operation stage from low rotational speed, and also provides a basis or calculation method for returning from the side deflection + stall control to the low rotational speed operation stage. In engineering applications, a basic model can be established according to the conditions for entering each operation stage disclosed in the present invention, or the wind speed can be used as a reference as the judgment condition for entering each stage. Description of the Drawings

[0024] Figure 1 is the flow chart of the present invention;

[0025] Figure 2 Schematically shows the Cq, Ct-λ curve diagram of the blade and the corresponding relationship diagram of the control stage. Specific embodiments

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0027] In the present invention, when the passive side-offset type wind turbine outputs at the best efficiency at a certain wind speed, the power is equal to the rated power, then the current wind speed is defined as the rated wind speed.

[0028] As Figure 2 shown, for the convenience of description, the Cq, Ct-λ curve diagram of the blade is divided into 4 intervals, which are respectively defined as operating region I, operating region II, operating region III, and operating region IV. Among them, operating region I corresponds to the maximum power tracking stage, operating region II corresponds to the high constant speed operation stage, operating region III corresponds to the low constant speed operation stage, and operating region IV corresponds to the side-offset plus stall control operation stage. Cq represents the blade moment coefficient, Ct represents the blade thrust coefficient, and λ represents the tip speed ratio.

[0029] As Figure 1 shown, a comprehensive control method for a passive side-offset type wind turbine provided by the present invention includes the following steps:

[0030] Step 1: When the current wind speed is less than the rated wind speed, the passive side-offset type wind turbine enters the maximum power tracking stage, and the optimal value of the tip speed ratio λ is between 6 and 9, that is, it enters operating region I, and operating region I is as shown in Figure 2 the corresponding interval. According to the basic requirements of the power generation of the wind turbine, the blade and generator parameters of the passive side-offset type wind turbine are designed to ensure that when the passive side-offset type wind turbine operates in operating region I, the passive side-offset type wind turbine will not enter the passive side-offset protection state, and the controller of the passive side-offset type wind turbine will not perform active electromagnetic stall control, and the wind turbine speed is maintained at an optimal tip speed ratio state.

[0031] In the maximum power tracking stage, if the current wind speed exceeds the rated wind speed, if the current wind speed is slightly higher than the rated wind speed, then control the passive side-offset type wind turbine to operate at the rated power, and at the same time control the passive side-offset type wind turbine to operate below the maximum speed point, that is, enter operating region II as shown in Figure 2Enter step 2 for the corresponding interval.

[0032] Step 2: The passive yaw type wind turbine enters the high constant speed operation stage and operates in operation area II:

[0033] In the high constant speed operation stage, if the wind speed further increases, the rotational speed of the wind turbine is adjusted appropriately or kept constant, and the tip speed ratio λ moves in the decreasing direction from the optimal value. The Ct value decreases but the curve is relatively gentle, and the passive yaw is in the initial yaw or non-yaw state. The Cq value increases and the curve is relatively steep, and the torque of the passive yaw type wind turbine increases rapidly.

[0034] When the wind speed further increases again: If the wind turbine torque is close to the set torque (the set torque is a value less than the generator torque), the target rotational speed is immediately reduced significantly and the generator torque is increased, so that the passive yaw type wind turbine quickly crosses the area below area II to operation area III as shown in Figure 2 the corresponding interval, and enter step 3. The Ct value in operation area III is very low, and yaw protection basically does not occur. At the same time, the Cq value in operation area III is also very low and relatively flat, but the wind turbine moment has a square relationship with the wind speed.

[0035] Among them, the wind turbine torque is calculated by any one of the following two methods:

[0036] Method 1) According to the Cq, Ct-λ curve graph, the Cq value is known. Then, based on the air density ρ, the wind turbine radius R, the wind turbine area S, the wind speed V, and the Cq value, according to the wind turbine moment calculation formula Twind = 0.5×ρ×S×V 2 ×R×Cq to calculate the wind turbine torque;

[0037] Method 2) The wind turbine torque is directly calculated through the generator power and the wind turbine rotational speed.

[0038] In the high constant speed operation stage, when the wind turbine torque is less than the set torque, return to step 2.

[0039] The high constant speed operation stage mainly uses electromagnetic stall control as the main control means.

[0040] Step 3: The passive yaw type wind turbine enters the low constant speed operation stage and operates in operation area III. At this time, to increase the rotational speed of the passive yaw type wind turbine, it is necessary to rely on the current air density ρ, the wind speed V, the wind turbine area S = πR 2 ×cosθ (for example, the set yaw angle θ≥85°) and the set minimum thrust moment Fin (the wind turbine yaw moment greater than the return moment), according to the wind turbine thrust moment calculation formula The minimum Ct value is calculated. Based on this minimum Ct value, λ can be obtained by looking up the Cq, Ct-λ curve chart in reverse, thereby determining the minimum target speed of the generator that needs to be increased, that is, the speed at which the fan deflects to the large-angle side, and increasing the fan speed to this speed. While increasing the fan speed, the thrust torque of the wind turbine is increased, causing the wind turbine to deflect to the large-angle side, that is, entering the operating region IV as shown in Figure 2 the corresponding interval, and entering step 4.

[0041] In the low constant-speed operation stage: when the wind turbine torque is less than the set torque, return to step 2; when the wind turbine torque is equal to the set torque, the passive deflection type fan remains in the low constant-speed operation stage.

[0042] Step 4: The passive deflection type fan enters the deflection plus stall control operation stage and operates in the operating region IV:

[0043] Since the wind turbine deflects to the large-angle side at this time, the Cq curve will no longer be of reference significance. The thrust torque of the wind turbine at the maximum deflection angle (θ≥85°) is still greater than the return torque of the tail rudder. In the operating region IV, after the wind speed increases, the tip speed ratio decreases, which in turn causes the Ct value to decrease, but the proportion of the decrease in Ct is not as large as the proportion of the increase in V 2 As known from the wind turbine thrust calculation formula it can be seen that when the wind speed increases, the total wind turbine thrust will increase and maintain at the maximum deflection angle. Therefore, based on the above analysis, in the high wind speed stage, the fan operating in the operating region IV can avoid the violent swing of the tail rudder and maintain at a relatively large deflection angle.

[0044] In the operating region IV, when the wind speed decreases, the tip speed ratio becomes larger, which in turn causes the Ct value to increase. However, the proportion of the increase in the Ct value is smaller than the proportion of the decrease in V 2 When the wind speed decreases to a certain limit value, the deflection angle will start to decrease. When the deflection angle θ inferred from the wind turbine thrust torque calculation formula or directly measured drops to the set value (for example, θ≤60°), that is, the set target is a lower speed. Due to the mechanical hysteresis of the deflection, the speed will quickly run to the target speed before the deflection returns, and return to the low constant-speed operation region III, entering step 3.

Claims

1. An integrated control method for a passive yaw type wind turbine, characterized in that, the Cq - Ct - λ curve of the blade is divided into 4 intervals, which are respectively defined as operating region I, operating region II, operating region III, and operating region IV. Among them, operating region I corresponds to the maximum power tracking stage, operating region II corresponds to the high constant speed operation stage, operating region III corresponds to the low constant speed operation stage, and operating region IV corresponds to the yaw plus stall control operation stage. Cq represents the blade moment coefficient, Ct represents the blade thrust coefficient, and λ represents the tip speed ratio. Then the integrated control method includes the following steps: Step 1: When the current wind speed is less than the rated wind speed, the passive yaw type wind turbine enters the maximum power tracking stage and enters operating region I to ensure that when the passive yaw type wind turbine operates in operating region I, the passive yaw type wind turbine will not enter the passive yaw protection state, and the controller of the passive yaw type wind turbine will not perform active electromagnetic stall control, and keep the wind turbine speed in an optimal tip speed ratio λ state. Among them, when the passive yaw type wind turbine outputs at the best efficiency at a certain wind speed, the power is equal to the rated power, then the current wind speed is defined as the rated wind speed; In the maximum power tracking stage, if the current wind speed exceeds the rated wind speed, and if the current wind speed is slightly higher than the rated wind speed, then control the passive yaw type wind turbine to operate at the rated power, and at the same time control the passive yaw type wind turbine to operate below the maximum speed point, that is, enter operating region II and enter Step 2; Step 2: The passive yaw type wind turbine enters the high constant speed operation stage and operates in operating region II: In the high constant speed operation stage, if the wind speed further increases, then adjust the wind turbine speed or keep the wind turbine speed constant, so that the tip speed ratio λ moves in the decreasing direction from the optimal value; the Ct value decreases but the curve is relatively gentle, and the passive yaw is in the starting yaw or non - yaw state, the Cq value increases and the curve is relatively steep, and the torque of the passive yaw type wind turbine increases rapidly; When the wind speed further increases again: if the wind turbine torque is close to the set torque, then immediately greatly reduce the target speed and increase the generator torque, so that the passive yaw type wind turbine quickly crosses the region below region II to operating region III and enters Step 3; In the high constant speed operation stage, when the wind turbine torque is less than the set torque, then return to Step 2; Step 3: The passive yaw type fan enters the low constant speed operation stage and operates in operation area III. At this time, increase the speed of the passive yaw type fan. According to the current air density ρ, wind speed V, wind wheel area S = πR 2 ×cosθ and the set minimum thrust torque Fin, according to the wind wheel thrust torque calculation formula calculate the minimum Ct value. According to this minimum Ct value, reverse look up λ from the Cq, Ct-λ curve chart, so as to determine the minimum target speed of the generator that needs to be increased, that is, the speed of the large angle yaw of the fan, and increase the fan speed to this speed; while increasing the fan speed, the thrust torque of the wind wheel is increased, causing the large angle yaw of the wind wheel, that is, entering operation area IV, and entering Step 4; In the low constant speed operation stage: when the wind turbine torque is less than the set torque, then return to Step 2; when the wind turbine torque is equal to the set torque, then the passive yaw type wind turbine remains in the low constant speed operation stage; Step 4: The passive yaw type wind turbine enters the yaw plus stall control operation stage and operates in operating region IV: The rotor thrust moment at the maximum sideslip angle is still greater than the restoring moment of the rudder; in operating region IV, as the wind speed increases, the tip speed ratio decreases, which in turn causes the Ct value to decrease, but the proportion of the decrease in the Ct value is not as large as the proportion of the increase in V 2 When the wind speed increases, the total rotor thrust increases and remains at the maximum sideslip angle; In the operating region IV, when the wind speed decreases, the tip speed ratio λ increases, which in turn causes the Ct value to increase. The proportion of the increase in the Ct value is smaller than the proportion of the decrease in V 2 When the wind speed decreases to a certain limit value, the side deflection angle θ begins to decrease; when the side deflection angle θ drops to the set value, due to the mechanical hysteresis of the side deflection, the rotational speed will quickly run to the target rotational speed before the side deflection returns, and return to the operating region III, entering step 3.

2. An integrated control method for a passive yaw type wind turbine as described in claim 1, characterized in that, the wind turbine torque is calculated by any one of the following two methods: Method 1) According to the Cq, Ct-λ curve graph, the Cq value can be obtained. Then, based on the air density ρ, the wind turbine radius R, the wind turbine area S, the wind speed V, and the Cq value, the wind turbine torque is calculated according to the wind turbine torque calculation formula Twind = 0.5×ρ×S×V 2 ×R×Cq; Method 2) Directly calculate the wind turbine torque through the generator power and the wind turbine speed.

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