WO2014176862A1

WO2014176862A1 - Method for tracking and controlling optimal blade tip speed ratio of wind power generation unit

Info

Publication number: WO2014176862A1
Application number: PCT/CN2013/083656
Authority: WO
Inventors: 邬昌明; 邵宜祥; 王长宝; 王文卓; 胡丽萍; 曾雨竹; 蔡国洋
Original assignee: 国电南瑞科技股份有限公司
Priority date: 2013-05-02
Filing date: 2013-09-17
Publication date: 2014-11-06
Also published as: CN103244350B; CN103244350A

Abstract

Disclosed is a method capable of conducting adjustment at a low wind speed so that a fan operates under the condition of an optimal blade tip speed ratio, and simultaneously conducting periodic automatic correction on the value of the optimal blade tip speed ratio. The method comprises the following steps: calculating the exact power value of a generator via a feedback torque and a rotation speed, and calculating a wind speed via a power factor corresponding to the power and the optimal blade tip speed ratio; adjusting the rotation speed to make the fan operate at the optimal blade tip speed ratio under the condition where the rotation speed can be adjusted, and adjusting a pitch angle to make the fan operate at the optimal blade tip speed ratio under the condition where the rotation speed cannot be adjusted; and adopting a statistical average hill climbing method to correct the value of the optimal blade tip speed ratio corresponding to the minimum variable pitch angle.

Description

Optimal blade tip speed ratio tracking control method for wind turbine generators

The invention relates to the field of wind power generation, in particular to an optimal blade tip speed ratio tracking control method for a wind power generator set.

Background technique

The maximum power tracking of the wind turbine means that the wind turbine speed is adjusted to change with the wind speed below the rated wind speed, so that the wind turbine maintains the optimum tip speed ratio state and keeps the wind energy utilization coefficient at the maximum. Value, the method to get the maximum power output.

Maximum wind energy tracking (MPPT) is a core issue in wind power generation, but the characteristics of wind energy tracking are determined by wind turbines. Therefore, no matter what kind of wind turbine, the idea of wind energy tracking is the same. At present, the maximum wind energy tracking control commonly used is the optimal tip speed ratio method, power signal feedback method, optimal torque method and mountain climbing method.

The optimum tip speed ratio is calculated from the measured wind speed to the corresponding optimal speed, and the fan is maintained at the optimal speed by adjusting the torque. The main problem with this method is that it is not possible to accurately measure the actual wind speed.

The optimal torque method is a method of giving a given power and torque through a measured speed through a given speed and torque, power curve. The main problem of the method is that the optimal speed and torque and power curves are difficult to obtain. Another problem is that as the running time of the fan becomes longer, the blade deformation and the like cause the fan characteristics to change, so that the originally given speed and torque and power curves are no longer the optimal curve.

The hill climbing method is to disturb the command value of the fan speed control at a certain speed, and then observe the power change of the wind turbine. If the power is increased, the disturbance direction of the windmill speed is unchanged. If the power is reduced, the disturbance of the windmill speed is reversed. The Chinese patent application with the application number 201110173155.1 improved the climbing method. The patent algorithm not only inherits the advantages of the variable step climbing method to quickly search to the vicinity of MPP, but also has the maximum power point (MPP) detection and stopping mechanism. When the wind turbine is tracked to the vicinity of the MPP, the mechanism can not only effectively reduce the wear of the rotational speed oscillation on the mechanical components of the fan system, but also overcome the interference of the search direction judgment when the wind speed changes again after the algorithm stops acting, thereby further improving the wind energy capture efficiency. . The problem with this method is that it is suitable for small wind power generation systems with small inertia. For large wind turbine systems with large inertia, because the wind turbine has a large moment of inertia, the time constant of the system is long, making the method for large wind power. The unit cannot be effectively controlled.

The Chinese patent application with the application number of 200610097565.1 adopts the initial state to control the power signal of the fan according to the original maximum power curve. When the wind speed changes little, the hill climbing method is used to optimize the control, and the maximum output power at the current wind speed is obtained by the speed disturbance and the corresponding The generator speed is obtained from the original maximum power curve and the newly added data points to obtain the corrected maximum power curve. When the wind speed changes greatly Power signal feedback control is applied to the system with the revised latest power curve. The method requires high wind speed conditions of the wind field, especially the larger the unit capacity, the greater the inertia of the wind wheel. The longer the delay time required to control the fan to reach equilibrium by using the hill climbing method, the stability of the climbing system control system is usually required. Time is about five times the time required for the table to reach stability. For some Class A wind farms with high wind speed turbulence, it is more difficult to use this method for power curve correction.

Therefore, a new technical solution is needed to solve the above problems.

Summary of the invention

In order to solve the above technical problems, the present invention provides an optimal blade tip speed ratio tracking control method for a wind power generator set.

In order to achieve the above object, the optimal tip speed ratio tracking control method for the wind turbine of the present invention can adopt the following technical solutions:

An optimal blade tip speed ratio tracking control method for a wind power generator includes the following steps:

(1) Calculate the exact generator power value by feedback torque and speed, and calculate the wind speed by the power factor corresponding to the power and the optimal tip speed ratio;

(2) When the speed can be adjusted, adjust the speed to make the fan run at the optimum tip speed ratio state, adjust the pitch angle if the speed cannot be adjusted, and make the fan run at the optimal tip speed ratio state;

(3), using the statistical average climbing method, the minimum tip speed ratio corresponding to the minimum pitch angle is corrected, and the method of correcting the minimum blade angle ^0 corresponding to the optimal tip speed ratio by statistical average climbing method is : During the operation of the fan, the statistics of the calculated wind speed and the corresponding tip speed ratio in the specified sampling range are calculated. After the sampling statistics reach the expected scale, the average calculation is performed; after the first statistics are completed, the 3⁄4^ U3. After the disturbance is repeated, the stalk is repeatedly counted and compared with the previous statistical values, and the better ^ ' _{ρ Μ} 3 is selected. groom. After the re-count the optimal ^{¾ 0¾} running for some time the statistical verification process, retrieve ^^ - ^. The optimal value.

Compared with the prior art, the problems solved by the present invention are as follows: 1. How to obtain a precise wind speed to adjust the fan to make the fan run at the optimum tip speed ratio state; 2. How to increase the fan speed at the optimal tip speed The range of wind speed in the ratio state; 3. How to determine the optimum tip speed ratio corresponding to the 0° angle of the fan after the optimum tip speed ratio is uncertain or as the blade is deformed for a long time.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing a curve cluster of a power factor and a tip speed ratio as a function of a pitch angle in the present invention. Figure 2 is a graph showing the ideal state of operation of the fan in the present invention.

3 is a flow chart of the optimal tip speed ratio tracking control strategy of the present invention.

Fig. 4 is a flow chart showing the correction of the statistical average climbing method for the optimum tip speed ratio at the minimum angle in the present invention. detailed description The invention will be further clarified with reference to the drawings and specific embodiments, which are to be construed as illustrative only and not to limit the scope of the invention. Modifications of equivalent forms are intended to fall within the scope defined by the appended claims.

(1) Calculate the exact generator power value by feedback torque and speed, and calculate the wind speed by the power factor corresponding to the power and the optimum tip speed ratio.

(2) Adjust the speed to adjust the speed so that the fan operates at the optimum tip speed ratio. If the speed cannot be adjusted, adjust the pitch angle to make the fan run at the optimum tip speed ratio.

(3) Using the statistical average hill climbing method, the optimum tip speed ratio corresponding to the minimum pitch angle is corrected.

In the present invention, a method for obtaining a current wind speed by calculation is disclosed, and the wind speed can be used to more accurately control the optimal tip speed ratio tracking of the wind turbine. From aerodynamics we know the power P absorbed by the wind wheel. The relationship with wind speed is as follows:

Where t is the swept surface area of the wind wheel, p is the air density, and c is the power factor. Wherein / ^ can be obtained by the power measurement module, in order to ensure the accuracy of the calculation, the present invention proposes to use the current feedback torque I of the frequency converter and the current generator speed ω.

Ρ ₀ = Τ. * ω ,. (2) To calculate the wind speed value from equations (1) and ( 2), you need to know the size of ί ^ in the current state. Actually, the size of £^ is unknown, so it is assumed that the fan is currently running. For the optimum tip speed ratio state, it can be determined that ^ is the maximum power factor C _p — _ax ^ at the current pitch angle. After the simultaneous equations (1) and (2), the calculated wind speed is 1 = 2 * _s * ω _τ C. _p - _ni . _ax _β * p * A) (3) In the present invention, how to increase the fan is disclosed. The range of wind speeds at the optimum tip speed ratio. It can be seen from Fig. 1 that as the pitch angle increases, the optimal tip speed ratio corresponding to the maximum power factor also gradually increases. The formula for calculating the tip speed ratio is: Where w is the angular velocity of the fan blade, R is the radius of rotation of the fan blade, and V is the wind speed.

For different fans, the grid-connected speed range is basically constant, and the usual control method does not change the paddle during the maximum power tracking phase. Due to the limitation of the speed range, the maximum power tracking wind speed range is also determined. In the invention, it is proposed that under the small wind, when the fan is running at the lowest minimum grid-connected speed stage, the pitch control is performed according to the calculated wind speed, thereby changing the relationship between the power factor and the optimum tip speed ratio. From equation (4), as the optimum tip speed ratio increases and the minimum grid speed does not change, the optimal tip speed ratio tracking wind speed is smaller, thus increasing the fan operation at the optimal leaf. The purpose of the wind speed range in the sharp speed ratio state.

In the present invention, it is disclosed that the optimal tip speed ratio tracking control strategy is divided into two parts. According to the ideal operating curve of the fan in Figure 2, the AB phase is the constant speed phase, and the BC phase is the optimal tip speed ratio tracking phase at the constant pitch angle. In the AB phase, the torque is kept constant by adjusting the torque. The pitch angle is adjusted to ensure that the fan operates at the optimum tip speed ratio state. In the BC phase, the pitch angle is constant at the minimum blade angle |3⁄4 position. The moment command changes the generator speed to ensure that the fan operates at the optimum tip speed ratio. In the present invention, a correction of the minimum blade angle β _β corresponding to the optimum tip speed ratio value 3⁄4 by the statistical average hill climbing method is disclosed. _.ρ;ϋ 5. In the operation process of the fan, the values corresponding to the calculated wind speed and the corresponding tip speed ratio in the specified sampling range are counted, and the sampling statistics are averaged after reaching the expected scale. After the first statistics are completed, the 3⁄4^tj3⁄4 is perturbed, and the statistical process is repeated and compared with the previous statistical values to select a better value. After the optimal operation is counted for a period of time, the statistical verification process is re-executed, and the A _E _ optimal value is reacquired. Embodiments will be given below in conjunction with the drawings. The wind turbine converts the mechanical energy (P _n , ) into the electrical energy ( ) coefficient p = ^, and C _p , which is also the tip speed ratio A and the pitch angle: The function. That is to say, the power factor can be expressed as c _p = / , β \ The relationship between the three can be seen by the curve in Figure 1, for each of the determined pitch angle /? The maximum point C _ _m3X corresponds to an optimum tip speed ratio A _{pt →} g. Therefore, the optimal tip speed ratio tracking can be achieved by adjusting the pitch angle or adjusting the blade speed at a certain wind speed.

The invention divides the maximum power tracking control into two parts according to FIG. 2, one part adjusts the pitch angle to realize the fan running under the optimal tip speed ratio condition, and the other part operates by adjusting the blade rotation speed. Under the optimal tip speed ratio conditions. The process of completing the maximum power tracking by controlling the fan operation at the optimum tip speed ratio condition will be described below with reference to FIG.

1) Initialize the maximum power tracking control of the optimal tip speed ratio. The initialization content includes feedback torque, generator speed, power factor, output torque, and pitch angle command value.

2) According to the table, select the .^ :: value corresponding to the optimal tip speed ratio λ _{ίψί at} the current angle and substitute the formula (3) to calculate the current calculated wind speed _> .

3), use ^ and the actual speed Wr to calculate the tip speed ratio at the current time by the formula (4).

4) Compare the tip speed ratio of the current time with the corresponding pitch angle of 0° and the optimum tip speed ratio 1⁄2. If you enter step 8) of the adjustment. If you enter step 5) of the adjustment.

5) Adjust the pitch angle to 0° at a speed of Γ /s. According to the formula (1), and by .½ _¾ "calculate the optimal target rotational speed W

6) If the actual speed is greater than ^ f, increase the torque command value T by PI adjustment. If, less than the torque adjustment command value T _& i

7) Repeat steps 2), 3), 4) after the speed change. Until the fan calculates the ratio between the wind speed and the speed, the proportional relationship is the equilibrium state.

8) Maintain the constant speed at the lowest grid-connected speed by adjusting the torque command value 'i«f.

9) Look up the blade tip speed ratio, which is the pitch angle value corresponding to the optimum tip speed ratio. Use the lookup table pitch angle value as the target pitch angle value for pitch adjustment.

10) Repeat steps 2), 3), 4) after the pitch angle changes. Until the fan reaches the calculated wind speed, speed, and pitch angle, the balance is reached.

For high-power units, because the moment of inertia is too large, it is not easy to achieve the optimal value by tracking the optimal tip speed ratio in real time using the hill climbing method, and the dynamic disturbance is caused by the constant dynamic disturbance. Oscillation will deepen the wear of mechanical components and affect the operating life of the fan. The invention proposes a statistical climbing method, that is, by averaging the values in a certain range, the average tip speed ratio is disturbed and then statistically compared, thereby obtaining a suitable optimal leaf for fan control. Sharp speed ratio. The method is described below in conjunction with Figure 4:

1) Initialize the control of correcting the optimum tip speed ratio at a constant angle. The initialization includes the initial tip speed ratio initial value, the sampling scale, and the calculated wind speed range of the sample = ΐ3⁄4 «1, the tip speed of the sampling point Ratio range, tip speed ratio disturbance, etc.

2) Record all the calculated wind speeds within the calculated wind speed range, and record the corresponding tip speed ratio within the sampling tip speed ratio range. The recorded contents include: Calculate the wind speed and current power.

3), after the statistical scale reaches the set statistical scale, store the wind speed average and power average, and calculate the corresponding wind energy absorption efficiency - ^ 4), give the best tip speed to a disturbance of one step, repeat steps 2), 3). Compare the wind energy absorption efficiency of the two statistics.

5) If it is disturbed in the opposite direction, repeat steps 2), 3), 4). If ₃ . < _3⁄4, it will be disturbed in the same direction and repeat steps 2), 3), 4).

6) When both the forward disturbance and the reverse disturbance are less efficient than the current wind energy absorption efficiency, the current tip speed ratio is selected as the optimal tip speed ratio.

7) Determine an optimal tip speed ratio. Repeat steps 2), 3), 4), 5), and 6) after one year of operation to adjust the new optimum tip speed ratio.

The present invention has been described in terms of a preferred embodiment. It should be understood that the above embodiments are not intended to limit the invention in any form, and the technical solutions obtained by equivalent substitution or equivalent transformations fall within the scope of the present invention. Inside.

Claims

O 2014/176862 ττ rCtl 3⁄4 -l^ -H« PCT/CN2013/083656

A method for tracking and controlling an optimum tip speed ratio of a wind power generator, comprising the steps of:

(3) Using the statistical average climbing method to correct the optimal tip speed ratio corresponding to the minimum pitch angle, and correct the minimum blade angle _e corresponding to the optimal tip speed ratio λ by the statistical average climbing method. The method of ^― is: During the operation of the fan, the values corresponding to the calculated wind speed and the corresponding tip speed ratio in the specified sampling range are counted, and the sampling statistics are averaged after reaching the expected scale; the first statistical completion is completed. After the disturbance of A^y^, the statistical process is repeated and compared with the previous statistical values, and the better ^^ is selected. value. The statistics are optimal. After running for a period of time, the statistical verification process is re-executed, and the .__ optimal value is reacquired.

2. The optimal blade tip speed ratio tracking control method for a wind power generator according to claim 1, wherein: the method for calculating the wind speed in the step (1) is: the relationship between the power _Pg and the wind speed is: P _s = C _p pAv ³ ; where 4 is the swept surface area of the wind turbine, p is the air density, and C _p is the power factor; the current feedback torque I of the frequency converter and the current generator speed are used for calculation: p _g = 3⁄4 * ω _Γ ; Set ς, the maximum power factor under the current pitch angle?

^p ni^ ' Get the calculated wind speed as:

^ ^r? cG^.n. A γ 2 *' 3⁄4 * / ^-pjaisK--β Ρ ·

3. The optimal blade tip speed ratio tracking control method for a wind power generator according to claim 1, wherein: adjusting the pitch angle to adjust the pitch angle to enable the fan to operate at an optimum tip speed in the step (2) The ratio state method is: The tip speed ratio λ is calculated as: λ = =, where w is the fan blade angular velocity,

R is the radius of rotation of the fan blade, and V is the wind speed. With the increase of the optimum tip speed ratio and the minimum grid speed, the wind speed of the best tip speed ratio tracking is smaller, thus increasing the fan operation. At the most The purpose of the wind speed range in the state of the tip speed ratio.

4. The optimal blade tip speed ratio tracking control method for a wind power generator according to claim 1, wherein: adjusting the pitch angle to prevent the fan from operating at an optimum tip speed in the case where the speed cannot be adjusted in step (2) The ratio state is as follows: When the fan is in the constant speed phase, the torque is kept constant by adjusting the torque, and the blade angle is adjusted to ensure that the fan operates at the optimum tip speed ratio state; when the fan is at the constant pitch angle stage, the paddle is The angle angle is constant at the minimum blade angle position, and the generator speed is changed by adjusting the torque command to ensure that the fan operates at the optimum tip speed ratio state.