KR101304402B1 - Variable speed wind turbine system - Google Patents

Abstract

A variable speed wind turbine system is provided. A variable speed wind turbine system according to an embodiment of the present invention includes a rotor including a blade; A generator connected to the rotor; An air density measurer or estimator for measuring the air density; An wind speed measuring wind speed outside the nacelle; A power converter converting the voltage and current output through the singer generator into a constant voltage and current and transmitting the same to a system; The diameter of the blade, the gear ratio between the rotor and the generator, the pitch angle input from the rotor, the rotational speed measurement of the rotor, the air density measurement or estimate input from the air density measurement or estimator, the wind speed measurement input from the wind speed generator and the generator And a system controller for outputting a torque command for controlling the torque of the generator based on the input generator rotation speed measurement value.

Description

Variable speed wind turbine system {VARIABLE SPEED WIND TURBINE SYSTEM}

It relates to a wind turbine system, and more particularly to a variable speed wind turbine system based on a change in air density.

Wind turbines are machines that convert power energy from wind into mechanical energy. If mechanical energy is used directly by a machine, such as pumping water or grinding a mill, a wind turbine is a windmill. Similarly, if the mechanical energy is converted to electricity, the machine can be called a wind turbine or wind power plant. Since wind turbines use pollution-free and indefinite winds scattered everywhere, there is little effect on the environment and the land can be used efficiently. In addition, wind power generation is easier to operate and manage because it is relatively simple in structure and installation as compared with other power generation methods, and can be operated unmanned / automated, and thus it is emerging as a new energy generation means at a level that can compete with existing power generation methods.

As a means of generating new energy, it is of paramount importance to maximize the output of the wind turbine under the given natural environment. In addition, wind turbines must be installed for longer than 20 years once installed, minimizing the fatigue load of the wind turbine. Therefore, it is very important to suppress the reduction of the output of the wind turbine by an unexpected load while maintaining the output of the wind turbine at its maximum.

The present invention provides a wind turbine system capable of improving output performance and minimizing the effect of fatigue load by generating a torque command changed according to the change of air density in a low temperature environment and controlling the rotation speed of the generator based on the change. For the purpose of

According to an aspect of the present invention, a rotor including a blade, a generator connected to the rotor, an air density measuring or estimator for measuring air density, an wind speed measuring wind speed outside the nacelle, a voltage output through a singer generator, and A power converter that converts the current into a constant voltage and current and transfers it to the grid; And a diameter of the blade, a gear ratio between the rotor and the generator, a pitch angle input from the rotor, an air density measurement or estimated value input from the air density measurement or estimator, a wind speed measurement value input from the wind speed generator, and the generator. A variable speed wind turbine system is provided that includes a system controller that outputs a torque command for controlling torque of the generator based on an input generator rotation speed measurement.

The power converter may control power generation of the generator based on the torque command, a voltage and frequency measurement value input from the system, and an internal voltage and current value of the power converter.

In addition, when the temperature of the outside air is lower than the specified reference temperature value, the rated speed of the generator may be set to be lower than the rated speed when the reference temperature value.

The system controller outputs the torque command so that the output of the generator is maximum while controlling the pitch angle so that the pitch of the blade is the optimum pitch in the maximum output control section, and the torque of the generator is constant in the pitch angle control section. The torque command may be output to maintain the value, and the pitch angle may be controlled to fluctuate so that the generator maintains the rated output.

The output is calculated based on Equations 1 and 2 below, and the torque command may be calculated based on Equation 3 below.

[Equation 1]

Where ρ * is the air density measurement or estimated value, R is the diameter of the blade, Cp is the output coefficient, β is the pitch angle, υ is the wind speed measurement, and λ is expressed by the following equation Become,

&Quot; (2) "

ω _r is the rotational speed measurement of the rotor,

&Quot; (3) "

ω _g is the rotational speed measurement of the generator and G is the gear ratio between the rotor and the generator.

The air density measurement or estimator is a measurement device configured to measure air density directly or based on pressure, temperature and humidity measurements transmitted from pressure sensors, temperature sensors and humidity sensors installed in the wind turbine system. It may be a device capable of estimating the air density.

The details of other embodiments are included in the detailed description and drawings.

Wind turbine system according to an embodiment of the present invention can improve the output performance and can minimize the effect of the fatigue load due to the change in air density.

1 is a driving graph of a wind turbine for explaining why a wind turbine system according to an embodiment of the present invention is required.
2 is a graph showing an operating graph of a generator along with a power characteristic graph of a wind turbine system according to an embodiment of the present invention.
3 is a schematic configuration diagram of a wind turbine system according to an embodiment of the present invention implemented to apply the driving graph illustrated in FIG. 2.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise. Embodiments described herein will be described with reference to schematic diagrams and / or flow diagrams, which are ideal illustrations of the invention. Thus, the regions illustrated in the figures have schematic attributes and are not intended to limit the scope of the invention. Like reference numerals refer to like elements throughout.

1 is a graph illustrating a reason why a wind turbine system according to an embodiment of the present invention is required. The graph ① illustrated in FIG. 1 shows a case where the generator of the wind turbine is operated on the basis of the air density value 1.225 kg / m3 under the condition of 1 atm and an average temperature of 9.3 ° C. (reference temperature), and the graph ② shows the outside temperature − A case of 1.452 kg / m 3, which is an air density value under a 30 ° C. condition, is shown. Referring to Figure 1, it can be seen that higher air density requires higher torque at the same generator rotational speed in order to maintain an optimum peripheral speed ratio that maximizes the output coefficient. This leads to an increase in output. Based on this finding, the inventors conceived a wind turbine system that improves power performance at or below rated rotation speed by operating based on air density.

Hereinafter, a wind turbine system according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3.

2 is a graph showing an operating graph of a generator along with a power characteristic graph of a wind turbine system according to an embodiment of the present invention. Another wind turbine system in one embodiment of the invention may be a wind turbine system placed in a low temperature environment. Wind turbine systems can be placed in a wide variety of low temperature environments. For example, it may be installed in a cold district where the outside temperature is below 30 degrees Celsius, or may be installed in a region with a large daily crossing or a region with a great seasonal change. At low temperatures, the air density increases. Thus, the wind turbine system according to an embodiment of the present invention reflects a change in air density during operation.

운전 구간이고, B-C 구간은 최대 출력 제어 구간이고, C-D 구간은 발전기 일정속 구간이고, D-E 구간은 피치각 제어 구간이다. 미설명된 υ_min, υ_{rated ,} υ_max는 각각 최소 또는 시동(cut in) 풍속, 정격 풍속, 최대(cut out) 풍속을 각각 나타낸다. AB section in Figure 2 is the generator minimum speed

The driving section, the BC section is the maximum output control section, the CD section is the generator constant speed section, the DE section is the pitch angle control section. Unexplained υ _min , υ _{rated and} υ _max represent the minimum or cut in wind speed, rated wind speed and cut out wind speed, respectively.

3 is a schematic configuration diagram of a wind turbine system 100 according to an embodiment of the present invention, which is implemented to apply the driving graph illustrated in FIG. 2.

The wind turbine system 100 uses the aerodynamic characteristics of the kinetic energy of the flow of air to rotate the rotor 4 consisting of the hub 5 and the blade 6 to convert it into mechanical energy, which is then converted into mechanical energy. Rotates the rotor of the generator 7 and converts it into electrical energy. However, since the voltage and current output through the generator 7 is not constant, it is converted to a constant voltage and current through the power converter 20 and transferred to the system 30.

에 도달하게 되면, 발전기의 토크 또한 증가하기 시작한다. 이 구간이 발전기 최소 속도 운전 구간(도 2의 A-B 구간)에 해당한다. A wind speed, ie, cut-in wind speed (υ _min ), is reached that is sufficient to rotate the rotor 4 immediately after the wind power generation system 100 is initially started or paused for maintenance / check and then driven again. In turn, the system controller 40 transmits a pitch command β ^C to the rotor 4 such that the pitch β of the blade 6 is a nominal pitch. At nominal pitch the floating force is able to generate torque and accelerate the rotor 4. The speed of generator 7 at nominal pitch is the minimum rotational speed

When is reached, the torque of the generator also begins to increase. This section corresponds to the generator minimum speed operation section (AB section of FIG. 2).

In the maximum output control section (BC section in FIG. 2), the wind speed is below the rated speed (υ _rated ). The control goal in this section is to produce the maximum output. The output may be represented by Equation 1 below.

[Equation 1]

(Ρ *) is the air density measurement or the estimated value, R is the diameter of the blade, Cp is the output coefficient, β is the pitch angle, υ represents the wind speed measurement value.

As can be seen from Equation 1, in order to maximize the output P, the output coefficient Cp (λ, β) should be maximized. By the way, it is known that when the pitch of the blade 6 is maintained at the optimum pitch [beta] opt, there is an optimum peripheral speed ratio [lambda] opt which can maximize the aerodynamic torque Tr. The circumferential speed ratio λ can be obtained by Equation 2 below.

&Quot; (2) "

ω _r is the rotational speed of the rotor.

In general, the output coefficients Cp ([lambda], [beta] opt), which are functions of the main speed ratio [lambda] and the optimum pitch [beta] opt, become maximum when the main speed ratio [lambda] is the optimum main speed ratio [lambda] opt.

In conclusion, in order to keep the output coefficient Cp (λ, βopt) at maximum, the rotational speed of the rotor 4 should be linearly increased as the wind speed increases, so that the peripheral speed ratio becomes the optimal peripheral speed ratio λopt.

The increase in the rotational speed ωr of the rotor 4 can be controlled by controlling the torque Tg of the generator.

를 출력하고 출력 계수(Cp(λ, βopt))가 최대가 되도록 하여 결과적으로 최대 출력(P)이 생산될 수 있도록 한다. Therefore, the system controller 40 torque command for controlling the torque Tg of the generator.

The output coefficient Cp (λ, βopt) is maximized so that the maximum output P can be produced as a result.

The torque command can be obtained by Equation 3 below.

&Quot; (3) "

ω _g is the rotational speed of the generator 7 and G is the gear ratio between the rotor 4 and the generator 7.

In the conventional wind turbine system, the torque command is output with the air density ρ as a fixed constant, but in the wind turbine system 100 according to the exemplary embodiment of the present invention, the generator 7 and the generator 7 in the air density measurement or estimator 50 are used. The air density measurement or the estimated value ρ * measured by measuring the air density outside the nacelle 3 where the power converter 20 is installed is input to the system controller 40. The system controller 40 measures the wind speed υ input from the wind speed generator 20, the rotational speed ω _r of the rotor 4 input from the rotor 4, and the air input from the air density measurement or estimator 50. The torque command is output based on the density value (ρ *) to produce the maximum output at wind speeds below the rated speed (υ _rated ).

If the torque command is output using a fixed value of air density as in the related art, a problem may occur in which the output cannot be maximized. If the air in the outside air of the nacelle 3 becomes low and the actual air density increases, and outputs a torque command based on the fixed air density, the aerodynamic torque Tr applied to the rotor 4 by wind and The magnitude difference of the torque Tg of the generator controlled by the torque command becomes large, so that the generator rotational speed ωg moves to a place other than the target operating point and the rotational speed ωr of the rotor 4 at a point other than the target operating point. Is in equilibrium. After all, the wind speed υ is constant, but the rotational speed ωr of the rotor 4 has changed, so the circumferential speed ratio λ has changed, and the output coefficient Cp (λ, β) in accordance with the change in the circumferential speed ratio λ. Since is no longer the maximum value, the output falls short of the target output.

On the other hand, in the wind turbine system 100 according to an embodiment of the present invention, since the torque command is generated based on this value by measuring or estimating the actual air density, the output may be the maximum target output.

According to the present embodiment, the torque command output from the system controller 40 is input to the controller 28 of the power converter 20. The controller 28 of the power converter 20 may be provided from the current and voltage values 23 and 27 and / or the capacitor 24 transmitted from the generator 7 side converter 22 and the grid 30 side converter 26. Switching elements of the converters 22 and 26 (e.g., based on the value 25 of the transmitted DC voltage 25, the voltage V * and frequency f * input from the grid 30 and the torque command input) , Pulse width modulation (PWM) signal 29 that controls the turn-on or turn-off of the IGBTs, MOSFETs, GTOs, or SCRs. That is, through the turn-on turn-off control of the switches of the converters 22 and 26, the power generated by the power converter 20 can be stably supplied to the system 30.

에 먼저 도달한다. 이는 일반적으로 풍력 터빈의 기계적인 하중이나 로터(4)에서 발생되는 소음의 영향 때문이다. 따라서, 이 구간에서는 발전기(7) 속도(ωg)의 아핀 함수(affine function)로 토크 지령

을 계산한다. 즉, 도 2에 도시되어 있는 바와 같이 발전기 속도는 정격 속도

로 유지되지만 토크는 지속적으로 증가하는 전이(transition) 상태가 된다. 도 1에 도시되어 있는 바와 같이, 저온 환경하에서 측정된 공기 밀도값(ρ*)이 적용될 경우, 정격 속도

가 종래의 1기압, 외기 온도 9.3℃ 조건 하의 공기 밀도 값인 1.225kg/㎥ 조건하에서 적용되는 정격 속도

에 비해 낮게 설정되어야 함을 알 수 있다. 그러므로, 풍력 터빈 시스템(100)은 저온 환경하에서 공기 밀도가 변화(증가)하므로, 외기의 온도가 소정 기준온도값(예; 9.3℃) 보다 저온인 경우 발전기(7)의 정격 속도를 상기 기준온도값일 경우의 정격 속도보다 낮도록 설정함으로써 공기 밀도의 변화에 따라 변화된 토크 지령을 출력할 수 있다. 이 때, 상기 기준온도값은 외기의 온도에 의해 변화되는 공기 밀도 변화(증가)를 추정하기 위한 값으로 사용될 수 있으며, 외기의 온도 변화만으로도 밀도의 변화를 예측할 수 있기 때문에 지역적(예; 한랭지), 계절적 온도 변화에 대처하여 효과적으로 최대 출력을 생산하도록 할 수 있다.In the generator constant speed section (CD section in Fig. 2), the speed (ωg) of the generator 7 becomes the rated speed as the wind speed approaches the rated wind speed (υ _rated ).

To reach first. This is usually due to the mechanical load of the wind turbine or the effects of noise generated in the rotor 4. Therefore, in this section, torque command is made by affine function of generator 7 speed ωg.

. That is, the generator speed is the rated speed as shown in FIG.

It remains at, but the torque is in a constantly increasing transition state. As shown in Fig. 1, when the air density value ρ * measured under a low temperature environment is applied, the rated speed

Rated speed applied under 1.225kg / ㎥ condition, which is the air density value under the conventional 1 atmosphere and 9.3 ℃

It can be seen that it should be set lower than. Therefore, since the air density changes (increases) in the low temperature environment, the wind turbine system 100 changes the rated speed of the generator 7 when the temperature of the outside air is lower than a predetermined reference temperature value (for example, 9.3 ° C). When the value is set lower than the rated speed, the torque command changed according to the change in the air density can be output. At this time, the reference temperature value may be used as a value for estimating the change in air density (increase) that is changed by the temperature of the outside air, and because the change in density can be predicted only by the change in the temperature of the outside air (eg, cold districts). For example, it can effectively cope with seasonal temperature changes to produce maximum output.

The pitch angle control section (DE section in FIG. 2) is a section in which the wind speed is a value of the rated wind speed υ _rated or higher. At this time, generate a torque command so that the torque Tg of the generator is maintained at a constant value, and gradually increase the pitch angle in the system controller 40 to decrease the power generation efficiency to maintain the rated output (β ^c ). Pitch control to lower the

The air density measurement or estimator 50 illustrated in FIG. 3 is one device configured to measure air density directly, or pressure delivered from pressure sensors, temperature sensors and humidity sensors already installed in existing wind turbine systems. It may be a device capable of estimating the air density based on the temperature, humidity, and measurement values.

The wind turbine system 100 according to the embodiment of the present invention generates a torque command that is changed according to the change in air density and controls the rotational speed of the generator based thereon, thereby improving output performance and minimizing the influence of fatigue load. Can be.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are illustrative and explanatory only and are intended to be illustrative of the invention and are not to be construed as limiting the scope of the invention as defined by the appended claims. It is not. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

2: tower 3: nacelle
4: rotor 5: hub
6: blade 7: generator
20: power converter 30: system
40: system controller 50: air density measurement or estimator
60: wind fan

Claims (6)

A rotor comprising a blade;
A generator connected with the rotor;
An air density measurer or estimator for measuring the air density;
An wind speed measuring wind speed outside the nacelle;
A power converter converting the voltage and current output through the generator into a constant voltage and current and transmitting the same to a system; And
Diameter of the blade, gear ratio between the rotor and the generator, pitch angle input from the rotor, rotation speed measurement value of the rotor, air density measurement or estimation value input from the air density measurement or estimator, input from the wind speed controller A system controller for outputting a torque command for controlling the torque of the generator based on the wind speed measurement value and the generator rotation speed measurement value input from the generator,
And the system controller sets the rated speed of the generator to be lower than the rated speed of the generator when the temperature of the outside air is lower than the predetermined reference temperature. The method according to claim 1,
And the power converter controls power generation based on the torque command, voltage and frequency measurement values input from the system, and internal voltage and current values of the power converter. delete The method of claim 2,
The system controller
In the maximum output control section, the pitch angle is controlled so that the pitch of the blade is the optimum pitch, and the torque command is output so that the output of the generator is maximum,
In the pitch angle control section, the variable speed wind turbine system, characterized in that for outputting the torque command so that the torque of the generator is maintained at a constant value, and controlling the pitch angle so that the generator maintains the rated output. The variable speed wind turbine system according to claim 4, wherein the output is calculated based on Equations 1 and 2, and the torque command is calculated based on Equation 3 below.
[Equation 1]

Where ρ * is the air density measurement or estimated value, R is the diameter of the blade, Cp is the output coefficient, β is the pitch angle, υ is the wind speed measurement, and λ is expressed by the following equation Become,
&Quot; (2) "

ωr is the rotational speed measurement of the rotor,
&Quot; (3) "

ω g is the rotational speed measurement of the generator and G is the gear ratio between the rotor and the generator. 3. The method according to claim 1 or 2,
The air density measurement or estimator is a measurement device configured to measure air density directly or based on pressure, temperature and humidity measurements transmitted from pressure sensors, temperature sensors and humidity sensors installed in the wind turbine system. A variable speed wind turbine system, characterized in that the device that can estimate the air density.
.

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