Wind turbine generator active power coordination control method for load optimization of variable pitch system

Abstract

The invention relates to the technical field of variable-speed wind generating set control, in particular to a wind generating set active power coordination control method for load optimization of a variable-pitch system. The method comprises the steps that a fuzzy controller is designed to update a variable pitch range limiting parameter # imgabs0 #, and # imgabs1 # and a rotating speed range limiting parameter are used for conducting coordinated control over a pitch angle and torque so that a unit can accurately track an active power instruction issued by a wind power plant, and the load of a variable pitch system can be reduced. According to the method, the rotating speed and the rotating speed variation serve as input variables of a fuzzy controller, a fuzzy rule is established to dynamically update a variable pitch range limiting parameter # imgabs2 #, rotating speed range limiting parameters # imgabs3 # and # imgabs4 # are further introduced, the rotating speed adjusting error at the moment is redefined, and active power control of pitch angle and torque coordination is designed according to the rotating speed adjusting error. The method is simple and easy to implement, the range that the rotating speed participates in active power adjustment at any pitch angle is effectively expanded, and the load of a variable pitch system is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of variable speed wind turbine generator set control, and in particular to a wind turbine generator set active power coordinated control method with load optimization of a variable pitch system. Background Art

[0002] Faced with the challenges brought by global climate change and sustainable development goals, wind energy, as an important renewable energy source, is gradually increasing its share in the global energy structure. However, due to the inherent randomness and intermittency of wind speed, the impact of wind power generation systems on grid frequency and voltage stability is becoming more and more significant. Therefore, active power control of wind turbines remains a challenging topic.

[0003] In order to ensure that the wind turbine can track the active power command issued by the wind farm center, a proportional-integral control strategy is usually used to adjust the pitch angle to adapt to the change in power output. At the same time, the speed is kept at a non-optimal reference value to ensure the safety of the unit in high wind speed environments and track the active power command. In order to further improve the effect of power tracking, scholars have introduced The control strategy uses the linear matrix inequality method to optimize the control performance and smooths the power fluctuation caused by wind speed fluctuation by more finely adjusting the pitch angle. However, the above methods all rely on adjusting the pitch angle to smooth the power fluctuation in order to achieve active power control, which greatly increases the frequency of pitch angle adjustment and causes greater wear on the key components of the unit.

[0004] In order to reduce the frequency of pitch angle adjustment, scholars have proposed a rotor speed control method, which can smooth power fluctuations only by adjusting the speed at low wind speeds, effectively reducing the frequency of pitch adjustment. However, in high wind speed environments, it is still necessary to rely on adjusting the pitch angle to smooth power fluctuations, and its effect on reducing the load on the variable pitch system is limited. In order to more effectively reduce the load of the pitch system without significantly increasing the burden on the transmission system, further research is needed, which is also the main problem solved by the present invention. Summary of the invention

[0005] In order to expand the speed participation active power regulation range under any pitch angle and reduce the pitch angle regulation frequency, the present invention provides a simple, easy and low-cost wind turbine active power coordinated control method for load optimization of variable pitch system, which takes the speed and speed change as the input of the fuzzy controller, establishes fuzzy rules, and dynamically updates the variable pitch range limit parameters. At the same time, in order to reduce the increase in the transmission chain load, a speed range limitation parameter was further introduced, which effectively expanded the speed participation active power adjustment range, thereby reducing the pitch angle adjustment frequency and reducing the pitch system load.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a wind turbine active power coordinated control method with load optimization of a variable pitch system, comprising the following steps: A wind turbine active power coordinated control method with load optimization of a variable pitch system, the method comprising the following steps: (1) Using the wind power technology simulation platform, under turbulent wind conditions, the wind rotor speed , calculate the speed change, and use Indicates that the expression is: ; in, is the wind wheel speed at the current sampling time, is the wind wheel speed at the last sampling moment; (2) The speed obtained in step 1 and speed change , respectively design the proportional factors and It is normalized to obtain better response in transient and steady state, and the expression is: ; ; Among them, the scaling factor and The function is to normalize the data (that is, to limit the data much larger than plus or minus 1 to between plus or minus 1 through the proportional factor) to obtain better response in transient and steady state. Because the speed and speed change of the variable speed wind turbine are both limited physical quantities, the proportional factor is generally taken as a positive constant to achieve the purpose of normalization; (3) Normalize the speed after step 2 and speed change As the input of the fuzzy controller, the pitch range limit parameter is used as the output of the fuzzy controller, and the fuzzy set of input and output is designed, wherein the pitch range limit parameter is updated in real time by the rotational speed and the rotational speed change, and the updating strategy is realized by establishing fuzzy rules, that is, the rotational speed and the rotational speed change are used as the input of the fuzzy controller, and the pitch range limit parameter is used as the output of the fuzzy controller. Fuzzy rules are established before input and output, and the pitch range limit parameter is updated in real time; using overlapping triangular membership functions, the linguistic variables are represented by negative big (NB), negative small (NS), zero (ZO), positive small (PS), and positive big (PB); (4) Based on the language variables obtained in step 3, fuzzy rules are established to dynamically update the pitch range limit parameters. , whose expression is: ; in is the scale factor, is the total number of rules, Indicates Rules, For the The output of the rule, Indicates The weight of the rule, is the normalized pitch range limit parameter; (5) In order to reduce the increase in the load on the transmission chain, the speed adjustment range limit parameter is further introduced and , effectively expanding the range of speed participation in active power regulation at any pitch angle; (6) Redefine the adjustment error by using the pitch range limit parameters and speed adjustment range limit parameters introduced in steps 4 and 5 , whose expression is: ; in is the speed rating, is the optimal power curve and the reference power The intersection of (7) Using the adjustment error obtained in step 6, the pitch angle controller is designed using the PI control method. The specific expression is: ; in, and are the proportional and integral control parameters respectively; (8) Further design a multi-mode torque controller to work in conjunction with the pitch angle controller designed in step 7 to ensure efficient and stable operation of the wind turbine in the full wind speed range. The expression is: ; in, It is the active power instruction issued by the wind farm. is the optimal wind wheel speed control gain, is the generator torque.

[0007] Preferably, in step 4, the fuzzy rule table established is:

[0008] In the designed fuzzy controller, if-then statements are used, that is, if is NB and is NB, then α1 is PS, and so on; where the input and output language variables NB, NS, ZO, PS, and PB are in Fig.12,13, and 14 have been established.

[0009] Preferably, in step 6, is the optimal power curve and the reference power The specific expression is: ; in, is the optimal wind wheel speed control gain.

[0010] Compared with the prior art, the present invention has the following advantages: In view of the current situation that the RSC method can buffer the unbalanced power between input and output by adjusting the rotational speed only under zero pitch angle, which increases the load of the variable pitch system, the present invention designs a wind turbine active power coordinated control method for variable pitch system load optimization, and utilizes the rotational speed adjustment range limitation parameter and the variable pitch range limitation parameter to effectively expand the rotational speed participation active power adjustment range under any pitch angle without significantly increasing the transmission chain load, and significantly reduce the variable pitch frequency; in view of the fact that the RSC method can ensure that the wind turbine generator set accurately tracks the active power command issued by the wind farm center, a multi-mode torque controller is further designed to work in coordination with the designed pitch angle controller, so as to ensure that the wind turbine generator set operates efficiently and stably within the full wind speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described below in conjunction with the accompanying drawings.

[0012] Figure 1 is the true wind speed diagram; Figure 2 It is a design flow chart of wind turbine active power coordinated control method for load optimization of variable pitch system; Figure 3 The controller block diagram of the wind turbine active power coordinated control method for load optimization of the variable pitch system; Figure 4 This is a comparison chart of wind wheel speed; Figure 5 This is a pitch angle comparison chart; Figure 6 This is a comparison chart of power generation; Figure 7 It is a comparison chart of pitch angle change rate; Figure 8 This is a comparison diagram of the friction of the pitch bearing; Fig. 9 This is the Mx comparison diagram of the blade root; Fig.10 This is the comparison picture of My at the root of the leaf; Fig.11 This is the Mz comparison chart at the blade root; Fig.12is the membership function of the normalized speed; Fig.13 is the membership function of the normalized speed change; Fig.14 is the normalized membership function of the pitch range limit parameter. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] Example 1 The present invention provides a wind turbine active power coordinated control method with load optimization of a variable pitch system, comprising the following steps: Step 1: Take the turbulent wind with a duration of 600 seconds and an average wind speed of 9 m / s as the input of the GH Bladed wind power technology simulation platform. , calculate the speed change, and use Indicates that the expression is: ; in, is the wind wheel speed at the current sampling time, is the wind wheel speed at the last sampling moment.

[0015] Step 2: According to the speed obtained in step 1 and speed change , respectively design the proportional factors and It is normalized to obtain better response in transient and steady state, and the expression is: ; .

[0016] Step 3: Normalize the speed after step 2 and speed change As the input of the fuzzy controller, the pitch range limit parameter is used as the output of the fuzzy controller, and the fuzzy sets of input and output are designed. Using triangular membership functions with overlap, the linguistic variables are represented by negative big (NB), negative small (NS), zero (ZO), positive small (PS), and positive big (PB).

[0017] Step 4: Based on the language variables obtained in step 3, fuzzy rules are established to dynamically update the pitch range limit parameters. , whose expression is: ; in is the scale factor, is the total number of rules, Indicates Rules, For the The output of the rule, Indicates The weight of the rule. The established fuzzy rule table is: ; Step 5: In order to reduce the increase in the transmission chain load, the speed adjustment range limit parameter is further introduced. and , effectively expanding the range of speed participation in active power regulation at any pitch angle.

[0018] Step 6: Redefine the adjustment error by using the pitch range limit parameters and speed adjustment range limit parameters introduced in steps 4 and 5. , whose expression is: ; in is the speed rating, is the optimal power curve and the reference power The specific expression is: .

[0019] Step 7, using the adjustment error obtained in step 6, the pitch angle controller is designed, sampling PI control mode, and its specific expression is: ; in, and are the proportional and integral control parameters respectively.

[0020] In step 8, a multi-mode torque controller is further designed to work in conjunction with the pitch angle controller designed in step 7 to ensure efficient and stable operation of the wind turbine in the full wind speed range. The torque controller expression is: ; in, It is the active power instruction issued by the wind farm center. is the optimal wind wheel speed control gain.

[0021] The pitch angle controller designed in the present invention works in coordination with the speed controller to achieve accurate tracking of the active power control instructions issued by the wind farm and reduce the load on the variable pitch system. Under the action of the set speed range limit parameters and the variable pitch range limit parameters, the speed can effectively expand the range of active power regulation under any pitch angle without significantly increasing the load on the transmission chain. This method is simple and easy to use, and not only ensures that the wind turbine accurately tracks the active power instructions issued by the wind farm, but also significantly reduces the pitch angle adjustment frequency and reduces the load on the variable pitch system. The final controller block diagram of the wind turbine active power coordinated control method for variable pitch system load optimization is shown in the figure below. Figure 3 shown.

[0022] In order to quantitatively compare the control effects of the wind turbine active power coordinated control method for variable pitch system load optimization proposed in the present invention and the RSC method, it is necessary to explain the evaluation index of the pitch angle load. In practice, frequent adjustment of the pitch angle will accelerate the wear of key components of the unit, thereby shortening its service life. Therefore, the present invention uses the following index (PF, Pitch Fatigue) to evaluate the pitch system load: ; in, Represents the pitch angle of the wind turbine generator set, in units of , so the unit of this indicator is , which quantifies the time period during which the unit is in operation The average change of the pitch angle per second within seconds can effectively evaluate the load of the pitch system. In addition, the present invention compares the moment changes at the root of the blade respectively to more comprehensively evaluate the fatigue degree of the blade.

[0023] Example 2 This embodiment uses the wind power technology development software GH bladed simulation platform to verify the effectiveness of the method of the present invention.

[0024] The embodiment uses a 1.5MW three-blade horizontal axis variable speed wind turbine model, and its main parameters are shown in the following table:

[0025] The controller parameters are selected as follows: .

[0026] To simplify the description, in the comparison results, the name of the RSC method is replaced by RSC, and the name of the method of the present invention is replaced by fuzzy.

[0027] Figure 1 This is the actual wind speed diagram.

[0028] Figure 2This is a flow chart for the design of a wind turbine active power coordinated control method for load optimization of the variable pitch system. Using the GH bladed simulation platform, under turbulent wind conditions, the speed change is calculated based on the wind rotor speed, and the speed and speed change are normalized. The normalized speed and speed change are used as the input of the fuzzy controller, and the variable pitch range limit parameter is used as the output. The fuzzy sets of input and output are designed, and language variables are established. Based on the language variables, fuzzy rules are established to dynamically update the variable pitch range limit parameters. In order to reduce the increase in the transmission chain load, the speed range limit parameter is further introduced to effectively expand the speed participation active power regulation range under any pitch angle. The speed regulation error is further redefined, and the active power control coordinated with pitch angle and torque is designed based on the adjustment error.

[0029] Figure 3 This is a block diagram of the wind turbine active power coordinated control method for load optimization of the variable pitch system. The pitch angle controller first calculates the speed change according to the wind rotor speed, and normalizes the speed and speed change. Then the normalized speed and speed change are used as the input of the fuzzy controller, and the variable pitch range limit parameter is used as the output. Fuzzy rules are established to dynamically update the variable pitch range limit parameter. In order to reduce the increase in the load on the transmission chain, the speed adjustment range limit parameter is further introduced. and , and redefined the corresponding speed regulation error at this time. The torque controller switches different control modes according to the speed and works in conjunction with the pitch angle controller; in practice, this control framework can effectively expand the speed participation in active power regulation range under any pitch angle, while ensuring tracking of the active power command issued by the wind farm, significantly reducing the pitch angle adjustment frequency and reducing the load of the variable pitch system.

[0030] Figure 4 This is a comparison chart of wind wheel speed.

[0031] Figure 5 The pitch angle comparison chart is shown in Figure 2. After calculation, the total amount of pitch angle adjustment of the traditional RSC method is 95.11 The total amount of pitch angle adjustment of the method of the present invention is 57.94 , a decrease of 39.08%.

[0032] Figure 6 It can be seen that the method of the present invention can accurately track the active power command issued by the wind farm.

[0033] Figure 7 The comparison chart of pitch angle change rate is shown in Figure 2. After calculation, the traditional RSC method's pitch system load evaluation index PF=0.192 , the pitch system load evaluation index PF of the method of the present invention is 0.097 , a decrease of 49.6%.

[0034] Figure 8 It is a comparison diagram of the friction of the pitch bearing. It can be seen that compared with the traditional RSC method, the method of the present invention significantly reduces the friction at the pitch bearing.

[0035] Fig. 9 The figure is a comparison of the Mx moment at the root of the blade. After calculation, the equivalent fatigue load of the RSC method when the material coefficient of the blade root in the Mx direction is 10 is 1841000Nm, and the equivalent fatigue load of the method of the present invention when the material coefficient of the blade root in the Mx direction is 10 is 1836000Nm, which is reduced by 2.72%.

[0036] Fig.10 The figure is a comparison of the My moment at the root of the blade. After calculation, the equivalent fatigue load of the RSC method when the material coefficient in the My direction of the blade root is 10 is 1942000Nm, and the equivalent fatigue load of the method of the present invention when the material coefficient in the My direction of the blade root is 10 is 1492000Nm, which is reduced by 23.17%.

[0037] Fig.11 The figure is a comparison of the Mz moment at the root of the blade. After calculation, the equivalent fatigue load of the RSC method when the material coefficient in the Mz direction of the blade root is 10 is 16182Nm, and the equivalent fatigue load of the method of the present invention when the material coefficient in the Mz direction of the blade root is 10 is 13978.8Nm, which is reduced by 13.62%.

[0038] Fig.12 , Fig.13 and Fig.14 are the normalized speed, speed change and membership function of the pitch range limit parameter, that is, Fig.12 , Fig.13 and Fig.14 These are the membership functions of the input (normalized speed and speed change) and output (normalized pitch range limit parameter) established respectively. To design a fuzzy controller, the membership functions of the input and output must be established respectively before the fuzzy rules between them can be established.

Claims

1. A wind turbine active power coordinated control method with load optimization of a variable pitch system, characterized in that: The method comprises the following steps: (1) Using the wind power technology simulation platform, under turbulent wind conditions, the wind rotor speed , calculate the speed change, and use Indicates that the expression is: ； in, is the wind wheel speed at the current sampling time, is the wind wheel speed at the last sampling moment; (2) The speed obtained in step 1 and speed change , respectively design the proportional factors and It is normalized to obtain better response in transient and steady state, and the expression is: ； ； (3) Normalize the speed after step 2 and speed change As the input of the fuzzy controller, the pitch range limit parameter is used as the output of the fuzzy controller, and the fuzzy sets of input and output are designed; using triangular membership functions with overlap, the linguistic variables are represented by negative large NB, negative small NS, zero ZO, positive small PS, and positive large PB; (4) Based on the language variables obtained in step 3, fuzzy rules are established to dynamically update the pitch range limit parameters. , whose expression is: ； in is the scale factor, is the total number of rules, Indicates Rules, For the The output of the rule, Indicates The weight of the rule, is the normalized pitch range limit parameter; (5) In order to reduce the increase in the transmission chain load, the speed adjustment range limit parameter is further introduced and , effectively expanding the range of speed participation in active power regulation at any pitch angle; (6) Redefine the adjustment error by using the pitch range limit parameters and speed adjustment range limit parameters introduced in steps 4 and 5 , whose expression is: ； in is the speed rating, is the optimal power curve and the reference power The intersection of (7) Using the adjustment error obtained in step 6, the pitch angle controller is designed using the PI control method. The specific expression is: ； in, and are the proportional and integral control parameters respectively; (8) Further design a multi-mode torque controller to work in conjunction with the pitch angle controller designed in step 7 to ensure efficient and stable operation of the wind turbine in the full wind speed range. The expression is: ； in, It is the active power instruction issued by the wind farm. is the optimal wind wheel speed control gain, is the generator torque.

2. The method for coordinated control of active power of wind turbines with optimized pitch system load according to claim 1, characterized in that: In step 6, is the optimal power curve and the reference power The specific expression is: ； in, is the optimal wind wheel speed control gain.

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