JP2014143803A - Method of preventing overspeed of wind power generation device by employing pwm converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in the case where a wind velocity increases when extracting energy by means of a PWM converter connected to a wind power generator, it is necessary to release winds by means of an expensive pitch control device or the power generator and the PWM converter fall into overload if the winds are not released.SOLUTION: In a wind power generation device, a PWM converter is connected to a generator which is driven by a wind mill, and wind mill maximal output is extracted from varying winds. According to a method of preventing an overspeed of the wind power generation device by employing the PWM converter, the overspeed of the wind mill is prevented by torque control of the PWM converter based on a rotating speed of the wind mill.

Description

  The present invention relates to a torque control for connecting a PWM converter to a generator driven by a windmill, converting wind energy, and taking out an electrical output, and in particular, without using a wing pitch control in a windmill, The present invention relates to a method for preventing over-rotation of a wind turbine generator using a PWM converter, wherein output is continuously taken out even when the wind speed is high, and over-rotation and over-output of a wind turbine are prevented.

  The present applicant previously controlled a PWM converter connected to a windmill by a torque pattern based on the windmill rotation speed, and thus can take out the maximum output from the wind without requiring an anemometer. Has been proposed (see, for example, FIG. 1 of Patent Document 1 described later).

  Here, the characteristics of the wind turbine will be described. In general, the output of a windmill can be expressed as in equation (1). Further, the peripheral speed ratio λ is a ratio of the peripheral speed of the tip of the wind turbine blade to the wind speed, and can be expressed by the equation (2) using the radius R of the wind turbine.

P = K ₁ CpV ³ (1)
λ = Rω / V (2)

Here, P is the wind turbine output, R represents windmill radius, omega windmill angular velocity, V is the wind speed, Cp is the power coefficient of the wind turbine, K ₁ is a constant determined by the swept area of the air density and wind turbine.

  In general, the output coefficient Cp of the windmill represents a ratio of the output of the windmill that can be extracted from the wind input, and is uniquely determined when the shape of the windmill and the angle of the blade are determined. As an example, when the blade angle is set to a certain value, the output coefficient Cp of the windmill changes according to the peripheral speed ratio λ as shown in FIG. 2, and has a characteristic having a certain maximum value (Cpmax). Then, the peripheral speed ratio λ that maximizes the output coefficient Cp is determined.

  Now, if the peripheral speed ratio with the maximum output coefficient is λm, and the expressions (3) and (4) are substituted into the expression (1), the output P of the windmill can be expressed by the expression (5).

λm = Rω / V (3)
ω = 2πN / 60 (4)
Pt = K ₁ Cpmax (2πN / (60 × λm)) ³ = K ₂ N ³ (5)

Here, Pt is the windmill maximum output, omega windmill angular velocity, N is the wind turbine's rotational speed, K ₂ is a proportionality constant. From this equation (5), it can be seen that the maximum output Pt of the wind turbine is proportional to the cube of the wind turbine rotation speed N.

T = P / ω (6)
T = 60K ₂ N ³ / (2 × π × N) = K ₃ N ² (7)

  Further, the torque is expressed as in equation (6). Substituting Equations (4) and (5) into Equation (6) yields Equation (7), and it can be seen that the torque T of the windmill is proportional to the square of the windmill speed N.

  Based on the above relationship, the wind turbine rotation speed versus wind turbine torque characteristic of FIG. 3 and the wind turbine rotation speed versus wind turbine output characteristic of FIG. 4 are obtained, and a conventional example based on the principles of the wind turbine torque characteristic and the wind turbine output characteristic is shown in FIG. This will be described in detail with reference to a wind turbine generator connection diagram for explaining a torque command circuit using a PWM converter in wind power generation.

FIG. 4 is a diagram for explaining the outline of the wind turbine rotation speed versus the wind turbine output characteristic when the wind speed is used as a parameter.
As described above, when the shape of the windmill and the wind speed V are determined, the windmill output P with respect to the windmill rotation speed N is uniquely determined, and the windmill output P with respect to each wind speed V is shown as a thin solid line in FIG. . And the peak of the windmill output P in each wind speed V becomes the cube characteristic with respect to the windmill rotation speed like the maximum output curve Pt shown by the thick continuous line of FIG.

Further, FIG. 3 is a diagram for explaining the outline of the wind turbine rotational speed versus wind turbine torque characteristic used in the conventional example, which is obtained from the wind turbine rotational speed versus wind turbine output characteristic, and the wind turbine torque for each wind speed V is thin as shown in FIG. As shown by the solid line.
At this time, at each wind speed V, the wind turbine torque at the time of outputting the peak of the wind turbine output has a square characteristic with respect to the wind turbine rotation speed such as the maximum output torque curve Tt indicated by a thick solid line in FIG.

  Here, for example, the windmill rotational speed Nx at which the maximum output Px at the wind speed Vx in FIG. 4 and the windmill rotational speed Nx at the intersection Rx between the wind speed Vx and the maximum output torque curve in FIG. Represents something.

  In order to always obtain the maximum output of the wind turbine from the steady wind, it is only necessary to operate at a torque that is uniquely determined by the wind turbine rotation speed N along the maximum output torque curve Tt.

  FIG. 9 shows a connection diagram of a conventional wind power generator. In FIG. 9, 1 is a windmill, 2 is a tachometer, 3 is a generator, 4 is a PWM converter, 5 is a load, 10 is a torque command circuit, 6 is a pitch angle actuator, and 20 is a pitch angle command generation circuit.

The AC side of the generator 3 driven by the windmill 1 is connected to the PWM converter 4 and the windmill 1
The AC power of the generator 3 driven at a variable speed is converted into DC power by the PWM converter 4 and output to the load 5.
The torque command circuit 10 receives the wind turbine rotation speed N from the tachometer 2, generates a pattern control torque command value T * based on the maximum output torque curve of FIG. The PWM converter 4 is controlled by *.

  The operation of the wind turbine speed N and the wind turbine torque T when the wind speed fluctuates when the PWM converter 4 is controlled by such a pattern control torque command value T *, and the wind turbine speed vs. wind turbine torque characteristics of FIG. This will be described with reference to the figure.

  When the wind speed is Vx, the vehicle is operated at the intersection Rx on the maximum output torque curve, that is, the wind turbine torque Tx, and when the wind speed is low, the vehicle is operated at the intersection Ry, that is, the torque Ty on the maximum output torque curve.

  In this way, even if the wind speed V fluctuates, since the engine is always operated on the maximum output torque curve determined by the wind turbine rotational speed N, the wind turbine 1 is eventually operated on the maximum output curve shown by the thick solid line in FIG. Is operated at maximum output.

Japanese Patent Laid-Open No. 2003-239843

  However, since there is a rated load in the generator and the PWM converter, when the wind turbine is controlled using torque pattern control based on such a rotational speed, the wind turbine rotational speed increases when the wind speed exceeds a certain level. The machine and the PWM converter were overloaded, and there was a problem that they were damaged. In order to prevent overloading due to overwinding of the windmill, if it is attempted to keep the electrical load at the rated state, the wind energy must be increased because the wind energy is large, resulting in mechanical damage to the windmill. There was a problem of reaching.

  Further, there is a method of pitch control in which the wind turbine blade angle is changed to release wind energy. However, the actuator and the control device are expensive, and there are problems in terms of cost and maintenance.

  The present invention has been made in view of the above problems. In a wind turbine generator that connects a PWM converter to a generator driven by a wind turbine and extracts the maximum output of the wind turbine from the fluctuating wind, the PWM based on the wind turbine rotation speed is provided. An object of the present invention is to provide a method for preventing over-rotation of a wind power generator for controlling torque of a converter and preventing overload of a generator and a PWM converter and over-rotation of a windmill.

  According to the first aspect of the present invention, in the PWM converter connected to the generator driven by the wind turbine, the wind turbine maximum torque characteristic with respect to the wind turbine rotational speed uniquely determined from the shape of the wind turbine is determined, and the rated rotational speed of the wind turbine is determined. A method for preventing over-rotation of a wind turbine generator using a PWM converter, wherein torque control of the generator is performed so that a load torque of the generator is equal to or greater than a maximum torque of the wind turbine.

  According to the invention of claim 2, the torque characteristic at the time of the wind turbine maximum output with respect to the wind turbine rotational speed that is uniquely determined from the shape of the wind turbine is determined, and up to a predetermined overtorque start rotational speed that is less than the wind turbine rated rotational speed of the wind turbine. Driving at the wind turbine maximum output torque characteristic, and from the intersection of the over torque start rotation speed and the wind turbine maximum output torque above the over torque start rotation speed, the wind turbine rated rotation speed and the wind turbine maximum torque characteristic are 2. The method of preventing over-rotation of a wind turbine generator using a PWM converter according to claim 1, wherein the operation is performed with a torque characteristic that increases in proportion to an increase in the number of revolutions of the windmill through the intersection.

  According to the invention of claim 3, the wind turbine maximum output torque characteristic with respect to the wind turbine rotational speed that is uniquely determined from the shape of the wind turbine is determined, and up to a predetermined overtorque start rotational speed that is less than the wind turbine rated rotational speed of the wind turbine. Driving at the wind turbine maximum output torque characteristic, and from the intersection of the over torque start rotation speed and the wind turbine maximum output torque above the over torque start rotation speed, the wind turbine rated rotation speed and the wind turbine maximum torque characteristic are 2. The method of preventing over-rotation of a wind turbine generator using a PWM converter according to claim 1, wherein the wind turbine generator is operated with a torque characteristic that is greater than or equal to a square characteristic with respect to an increase in the number of revolutions of the windmill through the intersection.

  According to the invention of claim 4, the wind turbine maximum output torque characteristic with respect to the wind turbine rotational speed that is uniquely determined from the shape of the wind turbine is determined, and up to a certain overtorque start rotational speed that is less than the wind turbine rated rotational speed of the wind turbine. Driving at the wind turbine maximum output torque characteristic, and from the intersection of the over torque start rotation speed and the wind turbine maximum output torque above the over torque start rotation speed, the wind turbine rated rotation speed and the wind turbine maximum torque characteristic are 2. The method of preventing over-rotation of a wind turbine generator using a PWM converter according to claim 1, wherein the wind turbine generator is operated with a gradually increasing torque characteristic greater than or equal to a square characteristic with respect to an increase in the number of revolutions of the windmill through the intersection.

  In the method for preventing over-rotation of a wind turbine generator using a PWM converter connected to a generator driven by a wind turbine according to the present invention, the PWM converter based on the wind turbine rotation speed vs. torque characteristic that is the maximum output of the wind turbine until the wind turbine rated rotation speed is reached. It can be operated by torque control by and the maximum output can be obtained from the wind turbine.

  Furthermore, if the wind turbine tries to rotate more than the rated speed, the load torque of the generator as a load exceeds the maximum torque of the wind turbine, so the wind turbine speed can be kept near the rated speed of the wind turbine, and the wind turbine is over-rotated. Can be prevented.

It is a wind turbine generator connection diagram for demonstrating the over-rotation prevention torque command circuit by the PWM converter of this invention. It is a figure for demonstrating the relationship between the output coefficient of a windmill, and a circumferential speed ratio. It is a figure explaining the outline | summary of a windmill rotational speed versus windmill torque characteristic when a wind speed is made into a parameter. It is a figure explaining the outline | summary of a windmill rotation speed versus windmill output characteristic when a wind speed is made into a parameter. It is a figure for demonstrating the output characteristic and torque characteristic with respect to the peripheral speed ratio of the windmill which concerns on this invention. It is explanatory drawing which shows the outline | summary of the torque characteristic which added the method of preventing the excessive rotation of the wind power generator by the wind turbine rotational speed and PWM converter which concerns on this invention, and a PWM converter. It is explanatory drawing which shows the outline | summary of the output characteristic which added the excessive rotation prevention method of the wind power generator by the windmill rotational speed vs. windmill maximum output characteristic and PWM converter which concerns on this invention. It is a figure for demonstrating the outline | summary of the torque characteristic with respect to the increase in the windmill rotational speed of Examples 2-4 in the torque characteristic which added the excessive rotation prevention method of the wind power generator by the PWM converter which concerns on this invention. It is a wind turbine generator connection diagram for demonstrating the torque command circuit by the PWM converter of a prior application.

  In a PWM converter connected to a generator driven by a windmill, a windmill rotation speed vs. torque characteristic which is a windmill maximum output uniquely determined from the shape of the windmill and a windmill rotation speed vs. windmill torque characteristic which is a windmill maximum torque are determined, A method for preventing over-rotation of a wind turbine generator using a PWM converter, wherein torque control of the generator is performed so that a load torque of the generator is not less than a maximum torque of the wind turbine at a rated rotational speed of the wind turbine. is there.

  FIG. 1 is a connection diagram of a wind power generator in which a PWM converter is connected to a generator driven by the windmill of the present invention. Reference numeral 11 denotes an over-rotation prevention torque command generation circuit, and the same reference numerals as those in FIG. 9 denote the same components. Hereinafter, FIG. 1 will be described using the principles of FIGS. 5 and 6 applied in the present invention.

  FIG. 5 is an explanatory diagram for explaining the output coefficient Cp and the torque coefficient Ct with respect to the peripheral speed ratio λ of the wind turbine according to the present invention.

  Ct = Cp / λ (8)

  In general, the torque coefficient Ct is expressed by equation (8), but for convenience of explanation, the maximum value of the output coefficient Cp and the torque coefficient Ct with respect to the peripheral speed ratio λ is expressed by the same vertical axis. In FIG. 5, the peripheral speed ratio at which the output coefficient Cp is maximum is λx, the maximum output coefficient Cpmax is at the maximum output point Sx, the peripheral speed ratio at which the torque coefficient Ct is maximum is λy, and at the maximum torque point Ty. The maximum torque coefficient Ctmax is obtained.

An outline of the characteristics of the wind turbine torque and the load torque of the generator shown in FIG. 6 will be described with reference to FIG. The maximum output torque curve Tt is obtained by expressing the maximum output point Sx of FIG. 5 at each wind speed of a certain wind turbine as the wind turbine torque with respect to the wind turbine rotation speed N using the above equation (6). The wind turbine maximum torque curve Tv represents the maximum torque point Ty in FIG. 5 at each wind speed of a certain wind turbine as the wind turbine torque with respect to the wind turbine rotation speed N. That is, the wind turbine maximum output torque Tt of the wind turbine at all wind speeds is in the lower right portion of the maximum torque curve Tv.
The brake additional torque curve Ts represents the load torque of the generator 3 using the method for preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention.
These torque curves are uniquely determined with respect to the wind turbine rotation speed.

  The brake additional torque curve Ts in FIG. 6 will be described. Since the wind turbine is operated along the maximum output torque curve Tt of the wind turbine up to the wind turbine rotation speed Nu, the maximum output of the wind turbine is obtained by the torque control by the method of preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention. be able to. Then, at the wind turbine speed Nu below the rated speed, the brake additional torque curve Ts becomes a point U in FIG. 6 on the maximum output torque curve Tt. When the wind turbine rotational speed N rises above Nu, the brake additional torque curve Ts rapidly increases and intersects the wind turbine maximum torque curve Tv at the intersection R.

  When a wind turbine applies a load torque larger than the maximum torque curve Tv of the wind turbine, the wind turbine rotation speed N does not increase even if the wind speed V increases. The reason for this will be described below.

In FIG. 6, at the wind turbine speed Nr, the maximum torque curve Tv of the wind turbine 1 and the brake additional torque curve Ts of the generator of the present invention intersect at the intersection R.
Here, the wind speed when in the operating state at the intersection R is, for example, 12 m / s. For example, when the wind speed reaches 13 m / s, the operating point tends to shift to the intersection Q on the maximum torque curve Tv in FIG.

However, even if the wind speed is increased from 12 m / s to 13 m / s and the wind turbine rotational speed is increased, the load torque of the generator 3 represented by the brake additional torque curve Ts is greater than the wind turbine rotational speed Nr. The windmill cannot be accelerated because it is larger than the maximum torque curve Tv of the windmill 1.
The phenomenon of continuing the operation at the intersection R is due to the fact that when the wind speed reaches 13 m / s, the windmill operates on the left side of the maximum torque point Ty in the torque coefficient Ct of FIG.

Applying the above principle, the present invention realizes a method for preventing over-rotation of a wind turbine generator. The over-rotation prevention torque command generation circuit 11 in FIG. 1 receives the wind turbine rotation speed N from the tachometer 2 and reaches the wind turbine rotation speed Nu in FIG. 6 at the time of maximum wind turbine output with respect to the wind turbine rotation speed shown in FIGS. The torque command T * having the torque curve as described above is output to the PWM converter 4.
When the wind turbine speed Nu is equal to or higher than the wind turbine speed Nu in FIG. 6, the wind turbine speed N is input from the tachometer 2 and a torque command τ * such as the brake additional torque curve Ts that becomes the wind turbine maximum torque at the wind turbine speed Nr is output to the PWM converter 4. To do.

  Here, this windmill rotational speed Nu is set to a windmill rotational speed of about 3/4 to 4/5 of the rated rotational speed, for example.

  In this way, by detecting the wind turbine rotational speed N and appropriately designing the torque characteristics with respect to the wind turbine rotational speed, the brake additional torque curve Ts shown in FIG. 6 can be realized.

From the viewpoint of the wind turbine maximum output, the brake added torque curve Ts will be described with respect to the wind turbine rotation speed vs. wind turbine maximum output characteristics of FIG.
The brake additional output curve Ps in FIG. 7 is an output characteristic when the brake additional torque curve Ts in FIG. 6 is applied as the load torque of the generator. Until the wind turbine rotation speed N reaches Nu, the brake applied torque curve Ts and the maximum output torque curve Tt are operated so as to overlap each other. At the operating point U at the wind turbine rotation speed Nu, the wind turbine output Pu is obtained. Further, when the wind turbine rotational speed N rises to the wind turbine rated rotational speed Nr, the operating point becomes R and the wind turbine output Pr is obtained. Here, since the wind turbine output in the case of applying the method for preventing over-rotation of the wind turbine generator by the PWM converter of the present invention prevents over-rotation, the operating point R shown in the brake additional output curve Ps shown in FIG. It becomes a stop output characteristic.

  In FIG. 7, the wind turbine rotation speed Nu to Nr, that is, between the wind turbine outputs Pu to Pr is, for example, because the wind turbine is operating on the left side of the maximum output point Sx of the wind speed Vx in FIG. Is not obtained, but the difference is very small.

  Therefore, in the method for preventing over-rotation of the wind turbine generator by the PWM converter of the present invention, the maximum output is obtained based on the wind turbine rotation speed vs. torque characteristics at the time of the wind turbine maximum output, and the wind turbine is not increased above the wind turbine rated rotation speed Nr. Thus, it is possible to prevent over-rotation of the windmill.

  A brake applied torque curve Ts in the second embodiment is shown in FIG. The brake additional torque curve Ts represents the load torque of the generator 3 using the method for preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention.

  The brake applied torque curve Ts in the second embodiment shown in FIG. Since the wind turbine is operated along the maximum output torque curve Tt of the wind turbine up to the wind turbine rotation speed Nu, the maximum output of the wind turbine is obtained by the torque control by the method of preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention. be able to. When the wind turbine speed Nu is equal to or lower than the rated speed, the brake additional torque curve Ts is a point U in FIG. 8 on the maximum output torque curve Tt. When the wind turbine rotational speed N rises above Nu, the brake additional torque curve Ts (A) rises and intersects the wind turbine maximum torque curve Tv at the intersection R.

Here, the brake addition curve Ts in the second embodiment is given by the following equation, for example.
ΔN = N−Nu (N ≧ Nu) (9)
Ts = K ₄ N ² (0 ≦ N <Nu) (10)
Ts = K ₅ ΔN + K ₆ (N ≧ Nu) (11)

Here, K ₄ , K ₅ , and K ₆ are constants determined by the wind turbine rotation speed vs. wind turbine torque characteristics and the wind turbine output characteristics. Further, the windmill rotational speed Nu is set to a windmill rotational speed of about 3/4 to 4/5 of the rated rotational speed, for example.

  In FIG. 8, the wind turbine accelerates because the load torque of the generator 3 represented by the brake additional torque curve Ts (A) is larger than the maximum torque curve Tv of the wind turbine at a wind turbine speed Nr or higher. I can't. Therefore, even if the wind speed V increases, the wind turbine speed N does not increase.

As described above, in the second embodiment, the brake additional torque curve Ts (A) is set to realize the method for preventing over-rotation of the wind turbine generator. The over-rotation prevention torque command generation circuit 11 shown in FIG. 1 receives the wind turbine rotation speed N from the tachometer 2 until the wind turbine rotation speed Nu shown in FIG. A torque command T * is output to the PWM converter 4 such that the torque curve at the maximum output of the wind turbine with respect to the wind turbine rotation speed.
When the wind turbine rotational speed Nu is equal to or higher than the wind turbine rotational speed Nu shown in FIG. 8, the wind turbine rotational speed N is input from the tachometer 2, and the wind turbine maximum torque is obtained at the wind turbine rotational speed Nr. Command τ * is output to PWM converter 4.

  In this way, by detecting the wind turbine rotational speed N and appropriately designing the torque characteristics with respect to the wind turbine rotational speed, the brake added torque curve Ts (A) shown in FIG. 8 can be realized.

  Therefore, in the method for preventing over-rotation of the wind turbine generator by the PWM converter of the present invention, the maximum output is obtained based on the wind turbine rotation speed vs. torque characteristics at the time of the wind turbine maximum output, and the wind turbine is not increased above the wind turbine rated rotation speed Nr. Thus, it is possible to prevent over-rotation of the windmill.

  A brake applied torque curve Ts in the third embodiment is shown in FIG. The brake additional torque curve Ts represents the load torque of the generator 3 using the method for preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention.

  The brake applied torque curve Ts in the third embodiment shown in FIG. Since the wind turbine is operated along the maximum output torque curve Tt of the wind turbine up to the wind turbine rotation speed Nu, the maximum output of the wind turbine is obtained by the torque control by the method of preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention. be able to. When the wind turbine speed Nu is equal to or lower than the rated speed, the brake additional torque curve Ts is a point U in FIG. 8 on the maximum output torque curve Tt. When the wind turbine rotation speed N rises above Nu, the brake additional torque curve Ts (b) rises and intersects the wind turbine maximum torque curve Tv at the intersection R.

  Here, the torque characteristics after the wind turbine rotation speed Nu need to avoid a sudden torque change so as not to cause hunting or the like. Therefore, since the torque torque characteristic is up to the windmill speed Nu up to the windmill speed Nu, the torque characteristic that rises above the square characteristic is preferable after that.

Therefore, the brake addition curve Ts in the third embodiment is given by the following equation, for example.
ΔN = N−Nu (N ≧ Nu) (9) (re-written)
Ts = K ₄ N ² (0 ≦ N <Nu) (12)
Ts = K ₄ ΔN ⁿ¹ + K ₇ (N ≧ Nu, n ₁ ≧ 2) (13)

Here, K ₄ and K ₇ are constants determined by the wind turbine rotation speed vs. wind turbine torque characteristics and the wind turbine output characteristics. Further, the windmill rotational speed Nu is set to a windmill rotational speed of about 3/4 to 4/5 of the rated rotational speed, for example.

  In the third embodiment, in the torque characteristic at the wind turbine rotational speed Nu, a sudden torque change is avoided so as not to cause hunting or the like. The torque is set to increase.

  In FIG. 8, the wind turbine accelerates because the load torque of the generator 3 represented by the brake additional torque curve Ts (b) is larger than the maximum torque curve Tv of the wind turbine at a wind turbine speed Nr or higher. I can't. Therefore, even if the wind speed V increases, the wind turbine speed N does not increase.

As described above, in the third embodiment, the brake additional torque curve Ts (b) is set to realize the method for preventing over-rotation of the wind turbine generator. The over-rotation prevention torque command generation circuit 11 shown in FIG. 1 receives the wind turbine rotation speed N from the tachometer 2 until the wind turbine rotation speed Nu shown in FIG. A torque command T * is output to the PWM converter 4 such that the torque curve at the maximum output of the wind turbine with respect to the wind turbine rotation speed.
When the wind turbine rotational speed Nu is equal to or higher than the wind turbine rotational speed Nu in FIG. 8, the wind turbine rotational speed N is input from the tachometer 2, and the wind turbine maximum torque is obtained at the wind turbine rotational speed Nr. Command τ * is output to PWM converter 4.

  In this way, the brake additional torque curve Ts (b) shown in FIG. 8 can be realized by detecting the windmill rotational speed N and appropriately designing the torque characteristics with respect to the windmill rotational speed.

  Therefore, in the method for preventing over-rotation of the wind turbine generator by the PWM converter of the present invention, the maximum output is obtained based on the wind turbine rotation speed vs. torque characteristics at the time of the wind turbine maximum output, and the wind turbine is not increased above the wind turbine rated rotation speed Nr. Thus, it is possible to prevent over-rotation of the windmill.

  A brake applied torque curve Ts in the fourth embodiment is shown in FIG. The brake additional torque curve Ts represents the load torque of the generator 3 using the method for preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention.

  The brake additional torque curve Ts in the fourth embodiment shown in FIG. Since the wind turbine is operated along the maximum output torque curve Tt of the wind turbine up to the wind turbine rotation speed Nu, the maximum output of the wind turbine is obtained by the torque control by the method of preventing over-rotation of the wind turbine generator by the PWM converter that can be realized by the present invention. be able to. When the wind turbine speed Nu is equal to or lower than the rated speed, the brake additional torque curve Ts is a point U in FIG. 8 on the maximum output torque curve Tt. When the wind turbine rotation speed N rises above Nu, the brake additional torque curve Ts (c) rises and intersects the wind turbine maximum torque curve Tv at the intersection R.

  Here, the torque characteristics after the wind turbine rotation speed Nu need to avoid a sudden torque change so as not to cause hunting or the like. Therefore, since the torque characteristic is square with respect to the wind turbine rotation speed up to the wind turbine rotation speed Nu, a torque characteristic that increases while gradually shifting to the square characteristic or more with respect to the increase in the wind turbine rotation speed is preferable thereafter.

Therefore, the brake additional curve Ts in the fourth embodiment is given by the following equation, for example.
ΔN = N−Nu (N ≧ Nu) (9) (re-written)
Ts = K ₄ N ² (0 ≦ N <Nu) (14)
Ts = K ₄ ΔN ^m (N ≧ Nu) (15)
m = 2 + K ₈ ΔN ⁿ² (n ₂ ≧ 1) (16)

Here, K ₄ and K ₈ are constants determined by the wind turbine rotational speed versus wind turbine torque characteristics and the wind turbine output characteristics. Further, the windmill rotational speed Nu is set to a windmill rotational speed of about 3/4 to 4/5 of the rated rotational speed, for example.

  In the fourth embodiment, in the torque characteristic at the wind turbine rotational speed Nu, a sudden torque change is avoided so as not to cause hunting or the like. For example, the square is gradually raised with respect to the increase in the wind turbine rotational speed as shown in the equation (15). It is set so that the torque rises above the characteristic.

  Further, in the fourth embodiment, compared with the first, second, and third embodiments, the operation is performed with the torque characteristic along the maximum output torque curve Tt between the windmill rotation speed Nu and the rated rotation speed Nr. The wind turbine maximum output can be obtained efficiently in the vicinity of a few.

  In FIG. 8, the wind turbine accelerates because the load torque of the generator 3 represented by the brake additional torque curve Ts (c) is larger than the maximum torque curve Tv of the wind turbine at a wind turbine speed Nr or higher. I can't. Therefore, even if the wind speed V increases, the wind turbine speed N does not increase.

As described above, in the fourth embodiment, the brake additional torque curve Ts (c) is set, and the over-rotation preventing method for the wind turbine generator is realized. The over-rotation prevention torque command generation circuit 11 shown in FIG. 1 receives the wind turbine rotation speed N from the tachometer 2 until the wind turbine rotation speed Nu shown in FIG. A torque command T * is output to the PWM converter 4 such that the torque curve at the maximum output of the wind turbine with respect to the wind turbine rotation speed.
When the wind turbine rotational speed Nu in FIG. 8 or higher, the wind turbine rotational speed N is input from the tachometer 2, and the wind turbine maximum torque is obtained at the wind turbine rotational speed Nr. Command τ * is output to PWM converter 4.

  In this way, by detecting the wind turbine rotation speed N and appropriately designing the torque characteristics with respect to the wind turbine rotation speed, the brake additional torque curve Ts (c) shown in FIG. 8 can be realized.

  Therefore, in the method for preventing over-rotation of the wind turbine generator by the PWM converter of the present invention, the maximum output is obtained based on the wind turbine rotation speed vs. torque characteristics at the time of the wind turbine maximum output, and the wind turbine is not increased above the wind turbine rated rotation speed Nr. Thus, it is possible to prevent over-rotation of the windmill.

  In the above-described embodiment of the present invention, the case where the windmill rotational speed N is detected from the tachometer 2 has been described. However, the windmill rotational speed N is also obtained in the sensorless system using the voltage and current of the PWM converter 4 connected to the generator 3. Can be detected, and its value may be used.

  Furthermore, the generator 3 is not only a synchronous generator, but also a wind turbine rotation speed vs. wind turbine maximum output characteristic as shown in FIG. 4 and a maximum output torque curve of the wind turbine rotation speed vs. wind turbine maximum torque characteristic as shown in FIG. If the relationship is grasped, an induction generator may be used.

  Also, for fixed-wing wind turbines without pitch control, if the relationship between the wind turbine maximum output torque and the wind turbine maximum torque with respect to the wind turbine rotation speed at each wind speed is grasped, it is possible to obtain high Even when the wind speed is reached, sufficiently practical maximum output control can be performed.

  In the PWM converter connected to the generator driven by the wind turbine of the present invention, the maximum output can be taken out from the wind turbine up to a high speed wind turbine rotational speed lower than the wind turbine rated rotational speed, and even if the rotational speed of the wind turbine rises The maximum windmill output can be obtained. Next, when the wind speed becomes high and the wind turbine rated rotational speed Nr is exceeded, the torque of the generator as a load exceeds the wind turbine maximum torque, so the wind turbine rotational speed N may remain near the wind turbine rated rotational speed Nr. it can.

Therefore, it is possible to prevent overload and breakage of the generator or the PWM converter due to overrotation of the windmill without using an expensive pitch control for reducing the input from the windmill by escaping the wind, which is extremely useful in practice.

DESCRIPTION OF SYMBOLS 1 Windmill 2 Tachometer 3 Generator 4 PWM converter 5 Load 6 Pitch angle actuator 10 Torque command generation circuit 11 Overrotation prevention torque command generation circuit 20 Pitch angle command generation circuit

Claims (4)

  In a PWM converter connected to a generator driven by a wind turbine, a wind turbine maximum torque characteristic with respect to the wind turbine rotation speed that is uniquely determined from the shape of the wind turbine is defined, and the load torque of the generator is determined at the rated rotation speed of the wind turbine. A method for preventing over-rotation of a wind power generator by a PWM converter, wherein torque control of the generator is performed so as to be equal to or greater than a maximum torque.   The torque characteristic at the time of the wind turbine maximum output is determined with respect to the wind turbine rotation speed that is uniquely determined from the shape of the wind turbine, and the wind turbine maximum output torque characteristic is operated up to a predetermined overtorque start rotation speed that is less than the wind turbine rated rotation speed of the wind turbine. When the overtorque start rotational speed is exceeded, the wind turbine rotational speed is increased from the intersection of the overtorque start rotational speed and the wind turbine maximum output torque through the intersection of the wind turbine rated rotational speed and the wind turbine maximum torque characteristic. 2. The method of preventing over-rotation of a wind power generator by a PWM converter according to claim 1, wherein the operation is performed with a torque characteristic that increases in proportion.   The torque characteristic at the time of the wind turbine maximum output is determined with respect to the wind turbine rotation speed that is uniquely determined from the shape of the wind turbine, and the wind turbine maximum output torque characteristic is operated up to a predetermined overtorque start rotation speed that is less than the wind turbine rated rotation speed of the wind turbine. When the overtorque start rotational speed is exceeded, the windmill rotational speed increases from the intersection of the overtorque start rotational speed and the windmill maximum output torque through the intersection of the windmill rated rotational speed and the windmill maximum torque characteristic. 2. The method of preventing over-rotation of a wind power generator by a PWM converter according to claim 1, wherein the operation is performed with a torque characteristic that is greater than or equal to a square characteristic. The torque characteristic at the time of the wind turbine maximum output is determined with respect to the wind turbine rotation speed that is uniquely determined from the shape of the wind turbine, and the wind turbine maximum output torque characteristic is operated up to a predetermined overtorque start rotation speed that is less than the wind turbine rated rotation speed of the wind turbine. When the overtorque start rotational speed is exceeded, the windmill rotational speed increases from the intersection of the overtorque start rotational speed and the windmill maximum output torque through the intersection of the windmill rated rotational speed and the windmill maximum torque characteristic. 2. The method of preventing over-rotation of a wind power generator by a PWM converter according to claim 1, wherein the operation is performed with a gradually increasing torque characteristic that is greater than or equal to a square characteristic.

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