KR101716073B1 - Method and apparatus for controlling torque mode switch of wind turbine - Google Patents

Abstract

The present invention relates to a method to control a torque mode switch of a wind turbine and a system thereof, comprising: a rotary speed measurement unit to measure a rotary speed of a generator in real time; a pitch controller to calculate a pitch command angle of a blade in real time; a pitch angle limit device unit limiting a pitch command angle to determine a pitch angle of an actual blade; the torque mode switch to select a mode value based on the rotary speed measured in the rotary speed measurement unit, and the pitch angle determined in the pitch controller and the pitch angle limit device unit; and a torque controller to control torque of the generator in accordance with the mode value selected by the torque mode switch. Thus, a torque chattering problem occurring due to the torque mode switch when a wind speed is rapidly dropped to a wind speed lower than the rating wind speed from a wind speed higher than the rating wind speed can be prevented, and the torque controller can be stably operated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of controlling a torque mode switch of a wind turbine,

The present invention relates to a method and a system for controlling a torque mode switch of a wind turbine. More particularly, the present invention relates to a method for changing the torque magnitude of a generator depending on whether the output power of the wind turbine is less than or equal to the rated output and the rated output or greater.

Generally, a wind turbine is a machine that converts the kinetic energy of the wind into mechanical energy through rotation of the blades and converts the mechanical energy into electric energy by using the generator.

The output control method of the wind turbine is conceptually divided into two methods, torque control for controlling the rotation speed of the generator and pitch control for controlling the pitch angle. Torque control is performed in the region below the rated wind speed and pitch control is performed in the region above the rated wind speed.

The torque controller controls the torque magnitude of the generator to obtain the maximum output in the region below the rated wind speed, and the pitch controller adjusts the pitch angle so that the rated output is maintained in the region above the rated wind speed.

The torque controller of the wind turbine has two control logic when it is above the rated output. One of them is a method of keeping the torque magnitude of the generator constant at a rated torque magnitude and the other is a method of keeping the output power of the generator constant at the rated output power.

The important consideration in the torque control of such wind turbines is that the torque of the generator should be different when the wind is below the rated value or above the rated value. Therefore, there is a need for a method of appropriately controlling the torque mode switch for changing the torque magnitude of the generator.

The torque mode switch control method of a general wind turbine considers two kinds of information: the generator rotation speed and the blade pitch angle. If the rotation speed of the generator is higher than the rated rotation speed and the pitch angle is larger than the fine pitch angle, it is determined that the rated wind speed is higher than the rated wind speed and the generator mode torque of the rated torque magnitude is generated using the torque mode switch.

If the rotation speed of the generator is smaller than the rated rotation speed and the pitch angle is fine pitch angle, it is determined that the speed is less than the rated wind speed, and the generator torque is generated along the pre-calculated turn table using the torque mode switch . In this way, better output power can be obtained than when the torque mode switch is not used.

However, when the torque mode switch is used, torque chattering occurs when the wind speed falls below the rated wind speed from the rated wind speed. Since torque chattering occurs, there is a possibility that the stability problem of the torque controller itself and the abrupt change in the generator torque magnitude may cause the actual life of the wind turbine to decrease.

Therefore, there is a need for a torque mode switch control method capable of overcoming such torque chattering problems.

Korean Patent No. 1251285 Korea Patent No. 2012-0130892 Korea Patent No. 1264169 Korean Patent No. 1282540

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a torque mode control device and a torque mode control method for controlling the torque mode of a wind turbine, And to provide a method and system for controlling a torque mode switch of a wind turbine capable of preventing a torque chattering problem caused by a torque converter and operating the torque controller stably.

According to an embodiment of the present invention, both of the information on the generator rotation speed and the blade pitch angle are taken into consideration, and when the wind speed suddenly changes from the rated output to the rated output, the value of the torque mode switch is changed to the " And to provide a method and a system for controlling a torque mode switch of a wind turbine which can prevent torque chattering.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. It can be understood.

SUMMARY OF THE INVENTION A first object of the present invention is to provide a rotary speed measuring device for measuring a rotational speed of a generator in real time; A pitch controller for calculating a pitch command angle of the blade in real time; A pitch angle restricting unit for limiting a pitch command angle to determine a pitch angle of an actual blade; A torque mode switch for selecting a mode value based on the rotational speed measured by the rotational speed measuring unit and the pitch angle determined by the pitch controller and the pitch angle limiting unit; And a torque controller for controlling the torque of the generator according to the mode value selected in the torque mode switch.

The torque mode switch selects a first mode value when it is determined that the rated wind speed is based on the rotation speed and the pitch angle and selects a second mode value when it is determined that the rated wind speed is higher than the rated wind speed, The controller may control the generator torque at a torque value corresponding to the pre-calculated rotational speed in the case of the first mode value and the generator torque at a rated torque size in the case of the second mode value.

The torque value according to the pre-calculated rotational speed may be calculated by the following equations (1) and (2).

[Equation 1]

&Quot; (2) "

Ω _g is the generator rotational speed, T _g (t) is the first mode value, the generator torque is controlled in, K _opt is the optimum mode gain, C _{P, max} is the maximum power coefficient, λ _opt is the optimal state sokbi, R is blade length , rho is the air density, and N _gb is the gear ratio.

The torque mode switch selects the second mode value when the rotational speed is equal to or higher than the rated rotational speed and the pitch angle exceeds the pitch angle with the pitch, Selects the second mode value when the pitch angle is less than the fine pitch angle and selects the previously selected mode value as it is when the rotation speed is less than the rated rotation speed and the pitch angle exceeds the pitch angle which is a fine pitch, And selects the first mode value when the pitch angle is less than the rated rotation speed and the pitch angle is not greater than the fine pitch angle.

The pitch controller maintains the pitch angle at a fine pitch angle when the rotation speed is equal to or lower than the rated rotation speed and the pitch controller controls the pitch command based on the error between the rotation speed and the rated rotation speed when the rotation speed exceeds the rated rotation speed. And the pitch angle limiting unit determines the pitch angle of the actual blade by restricting the pitch command angle between the predetermined minimum pitch angle and the maximum pitch angle.

A second object of the present invention is to provide a method of controlling a vehicle, comprising: setting a rated rotational speed, a fine pitch angle, and a rated torque magnitude; Determining a pitch angle of the actual blade by the rotational speed measuring unit in real time, measuring the rotational speed of the generator in real time, calculating the pitch command angle of the blade in real time by the pitch controller, and limiting the pitch angle limiter with the pitch angle limit; Selecting a mode value based on the rotational speed measured by the rotational speed measuring unit and the pitch angle determined by the pitch controller and the pitch angle limiter; And controlling the torque of the generator in accordance with the mode value selected in the torque mode switch by the torque controller.

According to a second aspect of the present invention, in the selecting step, the torque mode switch selects a first mode value when it is determined that the rated wind speed is based on the rotation speed and the pitch angle, The torque controller controls the generator torque at a torque value corresponding to the pre-calculated rotational speed in the case of the first mode value, and the second mode value , The generator torque is controlled by the rated torque magnitude.

According to a second aspect of the present invention, the torque value according to the pre-computed rotation speed is calculated by the following equations (1) and (2).

[Equation 1]

&Quot; (2) "

Ω _g is the generator rotational speed, T _g (t) is the first mode value, the generator torque is controlled in, K _opt is the optimum mode gain, C _{P, max} is the maximum power coefficient, λ _opt is the optimal state sokbi, R is blade length , rho is the air density, and N _gb is the gear ratio.

According to a second object of the present invention, in the selecting step, the torque mode switch selects the second mode value when the rotation speed is equal to or higher than the rated rotation speed and the pitch angle exceeds a pitch angle which is a pitch And the second mode value is selected when the rotation speed is equal to or higher than the rated rotation speed and the pitch angle is equal to or less than the finite pitch angle and the rotation speed is less than the rated rotation speed and the pitch angle exceeds the fine pitch angle , The first mode value is selected as it is, and the first mode value is selected when the rotation speed is less than the rated rotation speed and the pitch angle is less than the pitch angle.

According to a second aspect of the present invention, in the case where the rotational speed is equal to or lower than the rated rotational speed, the pitch angle is maintained at a fine pitch angle, and when the rotational speed exceeds the rated rotational speed, The pitch angle limiting unit calculates the pitch angle of the actual blade by limiting the pitch command angle between the predetermined minimum pitch angle and the maximum pitch angle.

According to an embodiment of the present invention, it is possible to prevent the torque chattering problem caused by the torque mode switch when the wind speed suddenly drops below the rated wind speed in the torque control of the wind turbine at a speed higher than the rated wind speed, It has an effect that can be operated.

According to an embodiment of the present invention, both of the information on the generator rotation speed and the blade pitch angle are taken into consideration, and when the wind speed suddenly changes from the rated output to the rated output, the value of the torque mode switch is changed to the " So that torque chattering can be prevented.

It should be understood, however, that the effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those skilled in the art to which the present invention belongs It will be possible.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a block diagram showing a configuration of a torque mode switch control system of a wind turbine according to an embodiment of the present invention;
2 is a flow chart of a method of controlling a torque mode switch of a wind turbine according to an embodiment of the present invention,
3 is a graph of generator torque versus generator rotational speed according to an embodiment of the present invention,
4 is a block diagram of a pitch controller according to an embodiment of the present invention,
5 is a block diagram illustrating a torque mode switch and a torque control method according to a first embodiment of the present invention;
6 is a block diagram of a torque mode switch according to a first embodiment of the present invention;
FIG. 7 is a graph showing an air velocity versus time representing a stair wind speed,
8 is a graph showing a step response graph according to the first embodiment of the present invention,
9 is a graph showing a torque chattering analysis graph according to the first embodiment of the present invention,
Figure 10 is a graph of the pitch angle response over time,
11 is a step response graph according to the second embodiment of the present invention,
12 is a graph showing the torque chattering analysis graph according to the second embodiment of the present invention,
13 is a step response comparison graph of the first embodiment and the second embodiment,
14 is a block diagram of a torque mode switch according to a second embodiment of the present invention;
FIG. 15 is a graph of a turbulent wind speed over time,
Fig. 16 is a graph showing that the wind speed is lower than the rated wind speed in Fig. 15,
17 is a graph (1) of a turbulent wind speed numerical experiment result according to the first embodiment of the present invention,
18 is a graph (2) of a turbulent wind speed numerical experiment result according to the first embodiment of the present invention,
19 is a graph (3) of a turbulent wind velocity numerical experiment result according to the first embodiment of the present invention,
20 is a graph (1) of a turbulent wind speed numerical experiment result according to the second embodiment of the present invention,
21 is a graph (2) of a turbulent wind speed numerical experiment result according to the second embodiment of the present invention,
FIG. 22 is a graph showing the result (3) of a turbulent wind speed numerical experiment result according to the second embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more readily apparent from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

In this specification, when an element is referred to as being on another element, it may be directly formed on another element, or a third element may be interposed therebetween. Also in the figures, the thickness of the components is exaggerated for an effective description of the technical content.

Embodiments described herein will be described with reference to cross-sectional views and / or plan views that are ideal illustrations of the present invention. In the drawings, the thicknesses of the films and regions are exaggerated for an effective description of the technical content. Thus, the shape of the illustrations may be modified by manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention are not limited to the specific forms shown, but also include changes in the shapes that are produced according to the manufacturing process. For example, the area shown at right angles may be rounded or may have a shape with a certain curvature. Thus, the regions illustrated in the figures have attributes, and the shapes of the regions illustrated in the figures are intended to illustrate specific forms of regions of the elements and are not intended to limit the scope of the invention. Although the terms first, second, etc. have been used in various embodiments of the present disclosure to describe various components, these components should not be limited by these terms. These terms have only been used to distinguish one component from another. The embodiments described and exemplified herein also include their complementary embodiments.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms "comprises" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other elements.

In describing the specific embodiments below, various specific details have been set forth in order to explain the invention in greater detail and to assist in understanding it. However, it will be appreciated by those skilled in the art that the present invention may be understood by those skilled in the art without departing from such specific details. In some instances, it should be noted that portions of the invention that are not commonly known in the description of the invention and are not significantly related to the invention do not describe confusing reasons to explain the present invention.

<Configuration>

Hereinafter, the configuration and function of a torque mode switch control system for a wind turbine according to an embodiment of the present invention will be described. 1 is a block diagram illustrating a configuration of a torque mode switch control system for a wind turbine according to an embodiment of the present invention. FIG. 2 is a block diagram of a torque mode switch control system of a wind turbine according to an exemplary embodiment of the present invention. &Lt; / RTI &gt;

 1, a torque mode switch control system for a wind turbine according to an embodiment of the present invention includes a rotation speed measurement unit 10, a pitch angle limit unit 20, a torque mode switch 30, A torque controller 40, a pitch controller 50, and the like.

3 shows a generator torque graph for the generator rotation speed according to an embodiment of the present invention.

The torque controller 40 of the wind turbine can be divided into two cases when the output power is higher than or equal to the rated output power. As shown in Fig. 3, the "torque mode 1" is divided into a case where the output is equal to or lower than the rated output, and the case where the "torque mode 2" is equal to or higher than the rated output. As will be described later, when the first mode value is selected by the torque mode switch 30, the torque controller 40 sets the generator torque to the torque mode 1, and when the second mode value is selected, Respectively.

3, &quot; SpeedSet1 &quot; is the generator rotation speed at which control of the generator torque magnitude is started, &quot; SpeedSet2 &quot; is the generator rotation speed at the start of maintaining the rated torque magnitude of the generator, Speed.

The torque controller 40 at the rated output or less uses the torque T _g (t ₎ of the generator using Equation 1 below, which represents the steady-state relationship characteristic of the torque-speed in order to obtain the optimum main speed ratio λ _opt according to the magnitude of the wind speed ) Is proportional to the square of the rotational speed (? _G ) of the generator. The torque controller 40 at or below the rated output generates a generator torque using a pre-calculated lookup table, as shown in &quot; torque mode 1 &quot;

[Equation 1]

K _opt is a coefficient indicating the secondary characteristic between the torque of the generator and the rotational speed of the generator as the optimum mode gain, and is defined by the following equation (2).

&Quot; (2) &quot;

Here, C _{P, max} is the maximum output coefficient, λ _opt is the optimum principal speed ratio, R is the blade length, ρ is the air density, and N _gb is the gear ratio.

Also, the torque controller 40 of the wind turbine has two control logic when it is above the rated power. One is a method of keeping the torque magnitude of the generator constant at the rated torque magnitude and the other is a method of keeping the output power of the generator constant at the rated output power. In one embodiment of the present invention, a control method of keeping the torque magnitude of the generator constant as indicated by &quot; torque mode 2 &quot; in Fig. 3 is used. The equation for keeping the torque magnitude of the generator constant at the rated torque magnitude is shown in Equation 3 below.

&Quot; (3) &quot;

는 일반적으로 발전기의 정격토크크기이다. here

Is generally the rated torque magnitude of the generator.

The torque control method of a wind turbine according to an embodiment of the present invention first sets the rated rotation speed, the fine pitch angle, and the rated torque magnitude (S10).

Then, the rotational speed measuring unit 10 measures the generator rotational speed in real time, the pitch controller 50 calculates the pitch command angle of the blade in real time, and the pitch angle limiter unit 20 limits the pitch command angle To determine the pitch angle of the actual blade (S20). The torque mode switch 30 selects the mode value based on the rotational speed measured by the rotational speed measuring unit 10 and the pitch angle determined by the pitch controller 50 and the pitch angle limiter unit 20 .

Then, the torque controller 40 controls the torque of the generator in accordance with the mode value selected by the torque mode switch 30.

The torque mode switch 30 selects the first mode value when it is determined that the rated wind speed is based on the rotation speed and the pitch angle, and selects the second mode value when it is determined that the rated wind speed is higher than the rated wind speed.

As described above, in the case of the first mode value, the torque controller 40 controls the generator torque by the torque value according to the pre-calculated rotational speed, and in the case of the second mode value, by the rated torque size, .

In addition, the control system according to an embodiment of the present invention may further include a pitch controller (50). In the torque mode switch 30 of the wind turbine, not only the rotational speed of the generator is considered but the pitch angle of the blade is taken into consideration.

At a wind speed below the rated value, the pitch angle of the blade is maintained at a fine pitch angle which is an optimal constant value to produce the maximum output power. Generally, the fine pitch angle is "0 degree".

Here, the fine pitch angle is set to &quot; 0 degree &quot;. Even when the average wind speed is higher than the rated wind speed, the actual wind speed is the turbulent wind speed, and the rotational speed of the generator changes around the rated speed. If the rotational speed is smaller than the rated speed and the pitch angle is larger than the fine pitch in order to improve the output power even in this situation, the torque mode switch 30 keeps the rated torque magnitude constantly. This allows more rated power to be maintained.

In the output control of the wind turbine, the pitch controller 50 operates above the rated wind speed. The pitch controller 50 of the wind turbine generally uses pitch gain-scheduling with a PI controller in the form of a speed control loop, and the pitch controller 50 feeds back the rotational speed of the generator to calculate the generator's rated rotational speed (SpeedSet2) And the pitch angle of the blade is controlled by the PI controller over the rated wind speed.

The concept of the pitch gain-scheduling is that the absolute value of the nonlinear parameter of the aerodynamic torque with respect to the pitch angle becomes larger as the wind speed increases, so that the natural frequency of the pitch controller 50 is increased. The PI gain value is reduced by using the gain multiplier in order to use a smaller PI gain value.

는 피드백 되는 발전기 회전속도(Ω_g)와 기준입력인 발전기 정격 회전속도(Ω_ref)와의 오차이다. 4 shows a block diagram of a pitch controller 50 according to an embodiment of the present invention. The system configuration of the pitch controller 50 in the actual front wind speed section is indicated by a block diagram as shown in FIG. As shown in Figure 4,

Is the error between the generator rotational speed (Ω _g ) being fed back and the generator rated rotational speed (Ω _ref ) being the reference input.

)를 최소화하도록 피치 명령각(βc)을 조절한다. 실제적으로 피치각(β)은 피치각 제한장치(20)를 통하여 이하의 수학식 4와 같이 피치각의 최소값과 최대값 사이로 제한한다. The pitch controller 50 feeds back the generator rotation speed? _G to calculate an error (? _Ref ) with the generator input rotation speed? _Ref

) To minimize the pitch command angle ([beta] c). In practice, the pitch angle? Is limited between the minimum value and the maximum value of the pitch angle through the pitch angle limiter 20 as shown in Equation (4) below.

&Quot; (4) &quot;

? _min ????? _max

β _min is the minimum value of the pitch angle, and generally uses a fine pitch angle (β _fine ) value. Here, the fine pitch angle (beta _fine ) value is &quot; 0 degree &quot;. Is limited to a _fine pitch angle (beta _fine ) to produce the maximum output power below the rated wind speed. The maximum value (? _Max ) of the pitch angle is the maximum value of the pitch angle and can be set arbitrarily according to the wind turbine.

&Lt; Torque mode switch control method >

Hereinafter, a control method of the torque mode switch 30 will be described. That is, it will be explained how the first mode value (hereinafter, referred to as '0') or the second mode value (hereinafter, '1') is selected.

The torque mode switch control method according to the first embodiment of the present invention can be divided into the following four cases according to the rotational speed and the pitch angle of the generator. The four cases are as follows.

"Case 1 (Case1)":

If Ω _g ≥ Ω _grat and β> β _fine

Torque mode switch mode value = '1' (T _g = T _grat )

"Case 2 (Case 2)":

If Ω _g ≥ Ω _grat and β ≤ β _fine

Torque mode switch mode value = '1' (T _g = T _grat )

"Case 3 (Case 3)":

If Ω _g <Ω _grat and β> β _fine

Torque mode switch mode value = '1' (T _g = T _grat )

"Case 4 (Case 4)":

If Ω _g <Ω _grat and β ≤ β _fine

Torque mode switch mode value = '0' (T _g = Lookup Table)

Where ω _g is the generator rotation speed, Ω _grat is the generator rated rotation speed, β is the blade pitch angle, β _fine is the pitch angle of the pitch angle _, T _g is the torque magnitude of the generator, and T _grat is the rated torque magnitude to be.

As mentioned above, when the mode value of the torque mode switch 30 is &quot; 1 &quot;, the torque of the generator uses the rated torque magnitude. When the mode value of the torque mode switch 30 is &quot; 0 &quot;, a precomputed lookup table is used.

5 is a block diagram showing a torque mode switch 30 and a torque control method according to the first embodiment of the present invention. 6 shows a block diagram of a torque mode switch 30 according to a first embodiment of the present invention. When the rated wind speed is higher than the rated wind speed, set the value of the torque mode switch (30) to "1" to use the rated torque magnitude of the generator. When the engine speed is less than the rated wind speed, the value of the torque mode switch 30 is set to &quot; 0 &quot; so as to generate the generator torque using a pre-calculated lookup table using the optimum mode gain. There are many ways to implement the above four cases with the torque mode switch 30, one of which is implemented using a logic circuit &quot; OR &quot; statement.

The meaning of this implementation is that when the rotation speed of the generator is higher than the rated rotation speed and the pitch angle is larger than the fine pitch angle, it is judged that it is higher than the rated wind speed and the generator torque of the rated torque size is determined through the torque mode switch 30 Generate. The implementation of the "OR" statement is shown in FIG. The torque mode switch control method according to the first embodiment of the present invention can prevent the instantaneous drop in the torque magnitude due to the influence of the turbulent air velocity or the like.

However, the control method according to the above-mentioned first embodiment has a problem that torque chattering occurs at the torque magnitude of the generator when the rated wind speed is lower than the rated wind speed.

In order to solve the problem of torque chattering, a 2MW wind turbine will be described as an example in order to analyze why torque chattering occurs. In order to analyze the cause of torque chattering in the numerical experiments of wind turbine, step wind speed was used. FIG. 7 shows a graph of the wind speed versus time showing the stair wind speed.

The rated wind speed of a 2MW wind turbine is about 12m / s (11.7m / s) and the generator's rated rotation speed is 1,500rpm. Rated wind turbine

For the analysis of the case where the wind speed suddenly drops below the rated wind speed, a stair wind speed varying from 13 m / s to 11 m / s is used as shown in FIG. The results of the experiment are as shown in Fig. In FIG. 7, V is the wind speed.

First, when the steady state at the rated wind speed or more and the rated wind speed or less is discriminated and checked, the numerical experiment result is as shown in FIG. 8, P _g is the output power of the generator, T _g is the torque magnitude of the generator, _{Ω g} is the rotational speed of the generator, and β is the pitch angle of the blade. FIG. 9 and Table 1 below show the case where the step response in FIG. 8 is divided into cases corresponding to time zones. In Table 1, t represents time.

[Table 1]

Explaining the steady state above the rated wind speed, the wind speed is 13 m / s for 0 to 5 seconds, which is higher than the rated wind speed, and the generator rotation speed is 1,500 rpm, which is the rated rotation speed. In order to maintain the rated output, the aerodynamic torque generated by the blade must be reduced.

When the pitch angle of the blades is larger than the fine pitch angle &quot; 0 DEG C &quot;, the aerodynamic torque is reduced. When the wind speed is 13 m / s, the steady state value of the pitch angle is maintained at about 6.5 DEG . The torque mode switch 30 at this time corresponds to &quot; Case 1 &quot;, and the torque magnitude of the generator generates the rated torque magnitude.

Explaining the steady state below the rated wind speed, the wind speed is 11 m / s for 7.67 to 15 seconds, and the rotational speed of the generator is 1,494 rpm less than the rated rotational speed, which is less than the rated wind speed. Since the wind speed falls below the rated wind speed, the pitch angle is maintained at a pitch angle of "0 degrees" to obtain more aerodynamic torque. At this time, the torque mode switch 30 corresponds to &quot; Case 4 &quot;, and the torque magnitude of the generator adjusts the torque magnitude of the generator according to the rotational speed of the generator.

Next, let's examine the problem of torque chattering caused by the transient response when it suddenly falls below the rated wind speed above the rated wind speed.

For 5 ~ 7.67 seconds, when the aerodynamic torque and the generator torque are changed, the rotational speed of the generator changes, resulting in the transient response due to the dynamic characteristics of the wind turbine. However, below the rated wind speed, the rotation speed of the generator is always less than the rated rotation speed, so that there is no relation to the occurrence of torque chattering. The blade pitch angle also causes transient response due to the dynamic characteristics of the pitch controller 50. The pitch angle does not stop immediately at 6.27 seconds, which is a pitch angle of &quot; 0 degrees &quot;, but after 6.27 seconds, And remains at &quot; 0 degrees &quot; after vibrating. When vibrating around "0 degree", the pitch angle is not smaller than "0", which is the minimum value of the fine pitch angle due to the pitch angle limiter, but is slightly larger than "0" .

Due to this phenomenon, when the torque mode switch 30 is suddenly dropped below the rated wind speed above the rated wind speed, the state of "Case 4" is not maintained constantly after "Case 1" to "Case 4" The case where the fine pitch impression is greater than "0 degree" occurs, and then the state changes to "Case 3" again and then to "Case 4". In case "Case 3", the rated torque is generated. In case 4, the torque of the generator is adjusted in accordance with the rotational speed of the generator. Because "Case 3" and "Case 4" The torque chattering occurs.

FIG. 8 shows that torque chattering occurs for about 1.5 seconds from the time when the wind speed is changed from 13 m / s to 11 m / s and then falls to the pitch angle "0". At this time, it can be seen that the pitch angle is maintained at "0 degree" after several very small vibrations occur between "0 and 0.02 degrees" for about 1.5 seconds.

The problem of torque chattering caused by the above-described reason is a phenomenon appearing in &quot; Case 3 &quot; of the torque mode switch 30, and therefore, there is a need to compensate for &quot; Case 3 &quot;.

The control method of the torque mode switch 30 according to the second embodiment of the present invention described below is intended to solve the torque chattering problem shown in the first embodiment. When controlling the torque mode switch 30 according to the second embodiment of the present invention, both of the rotational speed of the generator and the pitch angle of the blade are considered as in the first embodiment.

As described above, when the first embodiment is applied, when the wind speed suddenly drops below the rated wind speed from the rated wind speed to below the rated wind speed, the pitch angle becomes a fine pitch angle &quot; 0 &quot; due to torque chattering caused by the dynamic characteristics of the pitch controller 50 &Quot;, a very small vibration is generated.

As mentioned above, when the rotational speed of the generator is smaller than the rated rotational speed and the pitch angle of the blade vibrates about &quot; 0 degrees &quot;, the &quot; Case 3 &quot; out of the four cases of the torque mode switch 30 causes the torque Chattering occurs. When the wind turbine suddenly falls below the rated power at or above the rated power, the phenomenon that the pitch angle oscillates near "0 degrees" is physically inevitable, but the "3" torque mode switch value is controllable.

In case 3, which is related to the occurrence of torque chattering in order to prevent torque chattering, it is preferable to use "1" or "0" instead of always using the value of the torque mode switch 30 as "1" need. 0 &quot; and &quot; 1 &quot; can be determined by using the &quot; previous value &quot; of the torque mode switch 30. [

A control method of the torque mode switch 30 according to the second embodiment of the present invention proposed to solve the torque chattering problem is as follows. It can be divided into four cases according to the rotational speed and pitch angle of the generator.

"Case 1 (Case1)":

If Ω _g ≥ Ω _grat and β> β _fine

Torque mode switch mode value = '1' (T _g = T _grat )

"Case 2 (Case 2)":

If Ω _g ≥ Ω _grat and β ≤ β _fine

Torque mode switch mode value = '1' (T _g = T _grat )

"Case 3 (Case 3)":

If Ω _g <Ω _grat and β> β _fine

Torque mode switch mode value (k) = torque mode switch mode value (k-1)

('1' or '0')

(T _g = T _grat or T _g = Lookup Table)

"Case 4 (Case 4)":

If Ω _g <Ω _grat and β ≤ β _fine

Torque mode switch mode value = '0' (T _g = Lookup Table)

Where k is "current state" and k-1 means "previous state".

5 for the result of using the &quot; previous state &quot; of the torque mode switch 30 in &quot; Case 3 &quot; falling below the rated wind speed above the rated wind speed. The numerical experiment results are shown in Fig. 11 is divided into time-based responses, and the result is shown in FIG. 12 and Table 2 below. In Table 2, t represents time.

[Table 2]

First, check the steady state under the rated wind speed and below the rated wind speed separately. Explaining the steady state above the rated wind speed, the speed of the generator is 1,500 rpm, which is the rated rotation speed, and the pitch angle is about "6.5 degrees" because the wind speed is 13 m / s over the rated wind speed for 0 to 5 seconds. Lt; / RTI &gt; This corresponds to "Case 1" and the value of the torque mode switch 30 is maintained at "1". This is the same as the result of the first embodiment.

When the steady state at the rated wind speed or below is explained, the wind speed is 11 m / s for 11.17 to 15 seconds, the rated wind speed is less than the rated wind speed, and the generator rotation speed is 1,494 rpm and the pitch angle is smaller than the rated rotation speed. to be. This corresponds to "Case 4" and the value of the torque mode switch 30 is maintained at "0". This is the same as the result of the first embodiment.

Next, check the operation of the torque mode switch 30 in the transient response that occurs when the rated wind speed drops below the rated wind speed.

First, when the transient response is 5 ~ 6.27 seconds after changing the wind speed to 11m / s, the rotational speed of the generator is smaller than the rated rotational speed, but the pitch angle is larger than the fine pitch angle. Since this corresponds to &quot; Case 3 &quot;, the value of the torque mode switch 30 should be judged from &quot; 1 &quot;

In this case, since the &quot; previous value &quot; of the torque mode switch 30 is &quot; 1 &quot;, it is determined to be &quot; 1 &quot; Next, at 6.27 seconds, the pitch angle falls to a pitch angle of &quot; 0 degrees &quot;. At this time, since the rotation speed of the generator is smaller than the rated rotation speed and the pitch angle is a fine pitch angle, it corresponds to "Case 4" and the value of the torque mode switch 30 changes to "0". Next, during 6.27 to 11.17 seconds, the pitch angle becomes larger than the pitch angle again due to the dynamic characteristics of the pitch controller 50.

Since this corresponds to &quot; Case 3 &quot;, the value of the torque mode switch 30 should be judged from &quot; 1 &quot; In this case, since the &quot; previous value &quot; of the torque mode switch 30 is &quot; 0 &quot;, it is judged as &quot; 0 &quot; At this time, the torque magnitude of the generator does not change abruptly to the rated torque magnitude, so torque chattering can be prevented.

Therefore, even if the pitch angle oscillates near &quot; 0 degree &quot; due to the dynamic characteristic of the pitch controller 50 after the pitch angle has fallen to the pitch angle of &quot; 0 degrees &quot;, the value of the torque mode switch 30 is &Quot;, it can be seen that the occurrence of torque chattering which is indicated in &quot; Case 3 &quot; of the conventional method can be prevented.

The results of numerical experiments comparing the torque mode switch control method of the first embodiment and the method of the second embodiment with respect to the stair wind speed are shown in Fig. It can be seen that the torque chattering is prevented by applying the control method of the torque mode switch 30 according to the second embodiment, thereby improving the transient response characteristic.

The control method of the torque mode switch 30 according to the second embodiment of the present invention is as shown in FIG. 14 in which the proposed method according to the above logic is implemented by Matlab / Simulink. This is one of several implementations and is implemented using logic circuit "AND" and integer delay z ^-1 . Where z ^-1 means "previous value".

In the proposed implementation, when the rotational speed of the generator is equal to or higher than the rated speed, the torque mode switch 30 is judged to be equal to or higher than the rated output and the value of the torque mode switch 30 becomes "1". If the rotation speed of the generator is smaller than the rated speed and the pitch angle is a pitch angle, the value of the torque mode switch 30 is determined to be "0". If the rotational speed of the generator is smaller than the rated speed and the pitch angle is larger than the pitch angle, the value of the torque mode switch 30 becomes "previous value" by using the integral delay function.

<Numerical Experiment Data>

The numerical experiment data of the first embodiment and the second embodiment in which the torque chattering problem is solved will be described below. It is very important to evaluate the output performance of a wind turbine control system using turbulent wind speeds that are similar to actual wind speeds. Turbulent wind speeds as shown in Fig. 15 were used to confirm the problem of torque chattering occurring when the wind speed suddenly drops below the rated wind speed above the rated wind speed. The turbulent wind velocity used was generated according to IEC-61400-1, with an average wind speed of 16m / s for 10 minutes and a turbulent intensity of 17.6%.

As shown in Fig. 15, the actual turbulence wind speed is very large and the operation of the correct torque mode switch 30 is important because the turbulence intensity is very large and the wind speed falls below the rated wind speed more than the rated wind speed (about 12 m / s) .

(1), 46.1 seconds (2), 56.6 seconds (3), 97.5 seconds (4), 205.9 seconds (5), and 228.1 seconds when the wind speed drops below the rated wind speed above the rated wind speed as shown in FIG. 6), 264.2 seconds (7), 277.8 seconds (8), 376.2 seconds (9), 389.7 seconds (10), 435.2 seconds (11), 489.5 seconds (12), 571.2 seconds (13), 585.6 seconds 14 times in total. The results of the numerical experiments using the turbulent wind speed and the control method of the torque mode switch 30 according to the first embodiment are as shown in Fig. 17, and the enlarged views for confirming torque chattering are shown in Figs. 18 and 19 same.

In the case of 14 times of falling wind speed below the rated wind speed from the rated wind speed to below the rated wind speed, a total of 11 times (corresponding to 1, 2, 3, 4, 6, 7, 8, 9, 11, 12, The pitch angle fell to &quot; 0 deg. &Quot; 17 shows that torque chattering occurs several times. Among the 11 times that the pitch angle falls to a pitch angle of &quot; 0 degrees &quot;, the torque chattering is performed 8 times in total (1, 4, 6, 7, 9, 11, 12, and 13). In the meantime, when the degree of torque chattering was large, it occurred in the vicinity of 97.5 seconds (4) and 489.5 seconds (12) shown in FIG. 18 and FIG.

The results of the numerical experiment using the control method according to the second embodiment of the present invention are as shown in FIG. 20, and the enlarged views are shown in FIGS. 21 and 22 to confirm the solution of the torque chattering. In this case, it can be seen that the problem of torque chattering which occurs when the wind speed suddenly drops from the rated wind speed to the rated wind speed or less can be prevented.

When the control method of the torque mode switch 30 according to the first embodiment is applied, the average output power is 1.97 MW, and the average output power when the control method according to the second embodiment is applied is also equal to 1.97 MW. Therefore, by using the control method of the torque mode switch 30 according to the second embodiment at the actual turbulent air velocity, it is possible to prevent the occurrence of torque chattering, which is a problem of the torque mode switch control method according to the first embodiment, It can be seen that there is an advantage to be able to do.

Therefore, according to the second embodiment of the present invention, as described above, the problem of torque chattering which occurs when the wind turbine suddenly falls below the rated wind speed in excess of the rated wind speed can be completely solved, and the torque of the generator You can control the size.

It should be noted that the above-described apparatus and method are not limited to the configurations and methods of the embodiments described above, but the embodiments may be modified so that all or some of the embodiments are selectively combined .

10: rotational speed measuring unit
20: Pitch angle limiter unit
30: Torque mode switch
40: torque controller
50: pitch controller

Claims (10)

A rotational speed measuring unit for measuring the rotational speed of the generator in real time;
A pitch controller for calculating the pitch command angle of the blade in real time;
A pitch angle restricting unit for limiting a pitch command angle to determine a pitch angle of an actual blade;
A torque mode switch for selecting a mode value based on the rotational speed measured by the rotational speed measuring unit and the pitch angle determined by the pitch controller and the pitch angle limiting unit; And
And a torque controller for controlling the torque of the generator according to the mode value selected in the torque mode switch,
Wherein the torque mode switch selects a first mode value when it is determined that the rated wind speed is based on the rotation speed and the pitch angle and selects a second mode value when it is determined that the rated wind speed is higher than the rated wind speed,
Wherein the torque controller controls the generator torque at a torque value according to the pre-calculated rotational speed in the case of the first mode value, controls the generator torque at a rated torque size in the case of the second mode value,
Wherein the torque mode switch selects the second mode value when the rotational speed is equal to or higher than the rated rotational speed and the pitch angle exceeds a pitch angle which is a pitch and the rotational speed is equal to or higher than the rated rotational speed, When the rotation speed is less than the rated rotation speed and the pitch angle exceeds a pitch angle which is a fine pitch angle, the previously selected mode value is directly selected, and when the rotation speed is lower than the rated rotation speed And when the pitch angle is less than or equal to the fine pitch angle, the first mode value is selected. delete The method according to claim 1,
Wherein the torque value according to the pre-calculated rotational speed is calculated by the following equations (1) and (2): &lt; EMI ID = 1.0 &gt;
[Equation 1]

&Quot; (2) &quot;

Ω _g is the generator rotation speed, T _g (t) is the generator torque controlled at the first mode value, K _opt is the optimum mode gain, C _{p, max} is the maximum output coefficient, λ _opt is the optimum primary speed ratio, R is the blade length, ρ is the air density, and N _gb is the gear ratio. delete The method according to claim 1,
The pitch controller maintains the pitch angle at a fine pitch angle when the rotational speed is equal to or lower than the rated rotational speed and the pitch controller calculates the pitch command angle based on the error between the rotational speed and the rated rotational speed when the rotational speed exceeds the rated rotational speed And the pitch angle limiting unit determines the pitch angle of the actual blade by limiting a pitch command angle between a predetermined minimum pitch angle and a maximum pitch angle. Setting a rated rotational speed, a fine pitch angle, and a rated torque magnitude;
Determining a pitch angle of the actual blade by the rotational speed measuring unit in real time, measuring the rotational speed of the generator in real time, calculating the pitch command angle of the blade in real time by the pitch controller, and limiting the pitch angle limiter with the pitch angle limit;
Selecting a mode value based on the rotational speed measured by the rotational speed measuring unit and the pitch angle determined by the pitch controller and the pitch angle limiter; And
And a torque controller controlling the torque of the generator according to the mode value selected in the torque mode switch,
Wherein the torque mode switch selects the first mode value when it is determined that the rated wind speed is based on the rotation speed and the pitch angle and selects the second mode value when it is determined that the rated wind speed is higher than the rated wind speed,
In the controlling step, the torque controller controls the generator torque at a torque value according to the pre-computed rotational speed in the case of the first mode value, and controls the generator torque at the rated torque size in the case of the second mode value. Lt; / RTI &gt;
In the selecting step, the torque mode switch selects the second mode value when the rotation speed is equal to or higher than the rated rotation speed and the pitch angle exceeds the pitch angle, and when the rotation speed is equal to or higher than the rated rotation speed And selecting the second mode value when the pitch angle is less than or equal to the finite pitch angle, selecting the previously selected mode value as it is when the rotation speed is less than the rated rotation speed and the pitch angle exceeds the pitch angle, Wherein the first mode value is selected when the rotation speed is less than the rated rotation speed and the pitch angle is less than or equal to the pitch angle. delete The method according to claim 6,
Wherein the torque value according to the pre-calculated rotational speed is calculated by the following equations (1) and (2): &lt; EMI ID = 1.0 &gt;
[Equation 1]

&Quot; (2) &quot;

Ω _g is the generator rotation speed, T _g (t) is the generator torque controlled at the first mode value, K _opt is the optimum mode gain, C _{p, max} is the maximum output coefficient, λ _opt is the optimum primary speed ratio, R is the blade length, ρ is the air density, and N _gb is the gear ratio. delete The method according to claim 6,
The pitch controller maintains the pitch angle at a fine pitch angle when the rotational speed is equal to or lower than the rated rotational speed and the pitch controller calculates the pitch command angle based on the error between the rotational speed and the rated rotational speed when the rotational speed exceeds the rated rotational speed Wherein the pitch angle limiting unit determines the pitch angle of the actual blade by limiting a pitch command angle between a predetermined minimum pitch angle and a maximum pitch angle.

Images