TECHNICAL FIELD
The present invention relates to a wind turbine generator and a method of controlling the same.
BACKGROUND ART
Conventionally, in such a wind turbine generator for performing interconnected operation together with a utility-grid, by controlling the rotational speed of a rotor and excitation current of the rotor, active power and reactive power are controlled, and the active and reactive powers are supplied to the utility grid.
Patent citation 1 discloses a technique for detecting a frequency of a utility grid, determining an active power demand value so that a grid frequency is equal to a predetermined value, and controlling the active power based on the active power demand value.
Patent Citation 1: Japanese Unexamined Patent Application, Publication No. 2002-44867
DISCLOSURE OF INVENTION
However, when fluctuation in the rotational speed of the
rotor is large, in association with the fluctuation, the
active power also largely fluctuates. Thus, for example, even
in a case where an active power amount per unit time required
by the utility grid side is small, the fluctuation in the

rotational speed of the rotor is large, so that the active power cannot be adjusted to a desired value. An excessive active power is supplied to the utility grid in response to the request, thereby causing a problem that an adverse influence is exerted on stability of the utility grid such as fluctuations in voltage or frequency.
The present invention has been achieved to solve the above problem, and it is an object thereof to provide a wind turbine generator capable of supplying active power according to a request of a utility grid, as well as a method of controlling the same.
A first mode of the present invention relates to a wind turbine generator, wherein in a case where a request for changing a maximum value of active power and a newly defined maximum value of active power are received from a utility grid side, a maximum value of an active power demand value set to a rated value is changed to the newly defined maximum value of active power at a predetermined change rate or less.
With such a configuration, in the case where the request
for changing the maximum value of active power and the newly
defined maximum value of active power are received from the
utility grid side, the maximum value of the active power
demand value, which is set to the rated value, is changed to
the newly defined maximum value of active power at the
predetermined change rate or less.
Since the maximum value of active power is changed at the predetermined rate or less, for example, by setting the predetermined rate to a change rate at which fluctuations in the voltage value or frequency fluctuations of the utility grid are suppressed to a predetermined value or less, a rapid change in the maximum value of the active power demand value set to the rated value can be prevented, and the frequency fluctuations or power fluctuations of the utility grid can be suppressed to a predetermined value or less. Examples of the operation state parameter include a rotor rotational speed, an excitation current of the rotor, and the like.
The wind turbine generator may include: a detecting unit
for detecting a parameter related to an operation state; a
demand value obtaining unit for storing first information in
which the parameter related to the operation state and an
active power demand value are associated with each other, and
obtaining an active power demand value corresponding to the
operation state parameter detected by the detecting unit
based on the first information; and a changing unit for
changing, in a case where a request for changing a maximum
value of active power and a newly defined maximum value of
active power are received from the utility grid side, a
maximum value of an active power demand value in the first
information, which is set to a rated value, to the newly
defined maximum value of active power at the predetermined
change rate or less.
With such a configuration, the first information in which a parameter related to an operation state and an active power demand value are associated with each other is held in the demand value obtaining unit. The active power demand value corresponding to the operation state parameter is read from the first information by the demand value obtaining unit. Based on the read active power demand value, the active power is controlled. In the case where a request for changing a maximum value of active power and a newly defined maximum value of active power are received from the utility grid side, the maximum value of the active power demand value in the first information, which is set to the rated value, is changed to the newly defined maximum value of active power at the predetermined change rate or less.
The changing unit in the wind turbine generator may
calculate the change rate by dividing a difference between
the active power demand value set to the rated value and the
newly defined maximum value of active power by predetermined
time required for the change, and employs the calculated
change rate in a case where the calculated change rate is
equal to or less than the predetermined change rate, while
employing the predetermined change rate in a case where the
calculated change rate exceeds the predetermined change rate
preliminarily set.
By determining the change rate as described above, the active power demand value set to the rated value can be gently changed. As a result, in a period in which the first information is being changed, active power can be prevented from sharply changing, and the influence on the utility grid of the change in the maximum value of active power can be reduced.
The wind turbine generator may further include a plurality of pieces of second information in which a parameter related to an operation state and an active power demand value are associated with each other and maximum values of the active power demand values are different from each other, for changing, in a case where a request for changing a maximum value of active power and a newly defined maximum value of active power are received from the utility grid side, an active power demand value set to a rated value step by step by using the second information in which the maximum value of the active power demand value is between the rated active power value and the maximum value of active power newly defined.
Since the maximum value of active power is changed by
using the plurality of pieces of second information held in
the changing unit as described above, the active power demand
value set to the rated value can be promptly changed. Since
the active power demand value set to the rated value is
changed step by step to the newly defined maximum value of active power in response to the request for changing the maximum value of active power, for example, by providing a large number of pieces of second information so as to suppress fluctuations in the voltage value or frequency fluctuations of the utility grid to a predetermined value or less, a sharp change in the active power demand value can be prevented, and the frequency fluctuations or power fluctuations of the utility grid can be suppressed to a predetermined value or less. Examples of the operation state parameter include the rotor rotational speed, the excitation current of the rotor, and the like.
A second mode of the present invention relates to a wind farm including a plurality of wind turbine generators, wherein at least one of the plurality of wind turbine generators is the wind turbine generator described above.
A third mode of the present invention relates to a
method of controlling a wind turbine generator, wherein in a
case where a request for changing a maximum value of active
power and a newly defined maximum value of active power are
received from a utility grid side, a maximum value of an
active power demand value, which is set to a rated value, is
changed to the newly defined maximum value of active power at
a predetermined change rate or less.
A fourth mode of the present invention relates to a
method of controlling a wind farm having a plurality of wind turbine generators, wherein the method of controlling a wind turbine generator described above is applied to at least one of the plurality of wind turbine generators.
According to the present invention, there is exerted an effect that active power can be controlled according to the request of a utility grid.
BRIEF DESCRIPTION OF DRAWINGS
[FIG. 1] Block diagram showing an example of a wind turbine generator according to an embodiment of the present invention.
[FIG. 2] Functional block diagram showing an example of an active power control unit.
Explanation of Reference: 1: wind turbine generator 2: utility grid 20: power converting unit 21: converter control unit 27: active power control unit 50: rotor speed detecting unit 51: demand value obtaining unit 52: changing unit 53: power demand value arithmetic unit
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a wind turbine generator and a method of controlling the same according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an example of the configuration of a power generator 6 provided in a wind turbine generator 1 and its periphery.
As shown in FIG. 1, the wind turbine generator 1 includes wind turbine blades 4, a gear 5, the power generator 6, a power converting unit 20, a converter control unit 21, a blade control unit 22, and a main control unit 24. The power generator 6 and a utility grid 2 are connected to each other. A rotor of the power generator 6 is joined to a wind turbine rotor (not shown) via the gear 5.
In the periphery of the power generator 6, there is provided a rotor speed detecting unit (detecting unit) 50 for detecting the rotor speed of the power generator 6. The rotor speed detected by the rotor speed detecting unit 50 is outputted to the main control unit which will be described later.
In the present embodiment, the power generator
(induction machine) 6 is constructed so as to be able to
output power generated by the power generator 6 to the
utility grid 2 from both of a stator winding and a rotor
winding. Concretely, the stator winding of the power
generator 6 is connected to the utility grid 2, and the rotor winding is connected to the utility grid 2 via the power converting unit 20.
The power converting unit 20 has a converter 14, a DC bus 15, and an inverter 16, and converts AC power received from the rotor winding to AC power adapted to the frequency of the utility grid 2. The converter 14 converts AC power generated in the rotor winding to DC power and outputs the DC power to the DC bus 15. The inverter 16 converts the DC power received from the DC bus 15 to AC power having the same frequency as that of the utility grid 2, and outputs the AC power.
The power converting unit 20 also has the function of converting the AC power received from the utility grid 2 to AC power adapted to the frequency of the rotor winding. In this case, the inverter 16 converts the AC power to DC power and outputs the DC power to the DC bus 15. The converter 14 converts the DC power received from the DC bus 15 to AC power adapted to the frequency of the rotor winding, and supplies the AC power to the rotor winding of the power generator 6.
The main control unit 24 has an active power control
unit 27. The active power control unit 27 has, as shown in
FIG. 2, the rotor speed detecting unit 50, an demand value
obtaining unit 51, a changing unit 52, and a power demand
value arithmetic unit 53„
The rotor speed detecting unit 50 detects, as a parameter in the operation state of the wind turbine generator 1, a rotor speed of the power generator 6, and outputs it to the demand value obtaining unit 51.
The demand value obtaining unit 51 has, as shown in FIG. 2, first information in which a rotor speed (operation state parameter) and a target value of active power (herein below, called "active power demand value") supplied to the utility grid 2 are associated with each other, obtains an active power demand value corresponding to the rotor speed detected by the rotor speed detecting unit 50 by using the first information, and outputs the active power demand value to the blade control unit 22 and the power demand value arithmetic unit 53. In the first information, the maximum active power value is set to a rated value P0. In a region where the rotor speed has a predetermined value or more, the rated value is outputted as the active power demand value.
The changing unit 52 changes the maximum value of the
active power demand value in the first information, at a
predetermined change rate or less, which is referred to by
the demand value obtaining unit 51 in a case where a request
for changing the maximum value of active power is received
from the utility grid 2 side for the purpose of suppressing
power fluctuations, improving transient stability, or the
like. For example, the changing unit 52 preliminarily stores
information on an upper limit value "a" of the change rate and time T required to change the first information, and determines the change rate within this range.
Concretely, in a case where the rated value of the present active power is denoted by PO and the maximum value of newly defined active power is denoted by P1, the changing unit 52 calculates a change rate (b = (P1 - P0)/T) by dividing the difference (P1 - P0) between the active power rated value PO and the maximum value PI of the newly defined active power by time T (for example, five minutes) required for such a change. The changing unit 52 employs a calculated change rate "b" in a case where the calculated change rate "b" is equal to or less than the upper limit value "a" of the preset change rate, while employing the upper limit value "a" in a case where the calculated change rate "b" exceeds the upper limit value "a". The change rate is not limited to this example but can be arbitrarily set by design.
With respect to the change rate of the changing unit 52
according to the present embodiment, as the time T required
for the change, preliminarily-determined time (for example,
five minutes) is employed. However, the present invention is
not limited to such predetermined time. For example, in a
case of receiving time T' together with a request for
changing the maximum value of active power, the changing unit
52 employs the received time T' as time information for
calculating the change rate "b", and the change rate "b" is calculated by b = (P1 - P0)/T". Further, in the case where the calculated change rate "b" is equal to or less than the preset predetermined change rate "a", the calculated change rate "b" is employed. In the case where the calculated change rate "b" exceeds the predetermined change rate "a" which is preset, the predetermined change rate "a" is employed. As described above, time required to change the maximum value of active power may be arbitrarily set.
When obtaining the rotor speed in a period in which the first information is changed by the changing unit 52, the demand value obtaining unit 51 reads the active power demand value from the first information which is being changed, and outputs it.
The active power demand value output from the demand value obtaining unit 51 is inputted to the blade control unit 22 and also inputted to the power demand value arithmetic unit 53.
The power demand value arithmetic unit 53 calculates a
reactive power demand value to be outputted to the utility
grid 2 based on the active power demand value outputted from
the demand value obtaining unit 51 and a power factor demand
value. The power factor demand value is a value obtained by
controlling cos9 of the phase difference 9 [rad] of voltage
and current as a power factor so as to be a power factor
required by the utility grid. More concretely, in a case where U denotes an effective value of voltage and I denotes an effective value of current, apparent power S = UI [VA], effective power P = UIcos [W], and reactive power Q = UIsin[var]. In this case, it is known that the following equation (1) is satisfied among the apparent power S, the active power P, and the reactive power Q. Based on the equation, the reactive power is calculated, and the calculated reactive power is used as a reactive power demand value. S2 = p2 + Q2 (l)
The power demand value arithmetic unit 53 outputs the reactive power demand value and the active power demand value obtained from the demand value obtaining unit 51 to the converter control unit 21 (refer to FIG. 1).
The converter control unit 21 generates a PWM (Pulse Width Modulation) signal based on the active power demand value and the reactive power demand value obtained from the active power control unit 27, and provides the PWM signal to the converter 14 and the inverter 16. Consequently, the active power and the reactive power according to the active power demand value and the reactive power demand value, respectively, provided from the active power control unit 27, are supplied to the utility grid 2.
The blade control unit 22 generates a pitch angle demand
value ß* based on the active power demand value received from
the active power control unit 27 in the main control unit 24 and the rotor speed, and controls the pitch angle of the wind turbine blade 4 so that an actual pitch angle ß coincides with the pitch angle demand value ß*.
Next, the action of the wind turbine generator 1 according to the present embodiment will be described.
First, the rotor speed of the wind turbine generator 1 is detected by the rotor speed detecting unit 50 at predetermined time intervals, and the detection value is provided to the active power control unit 27 in the main control unit 24. In the active power control unit 27, the active power demand value corresponding to the rotor speed is obtained from the first information by the demand value obtaining unit 51, and the obtained active power demand value is provided to the blade control unit 22 and the power demand value arithmetic unit 53.
In the blade control unit 22, the pitch angle demand
value ß* corresponding to the active power demand value is
obtained, and the blade pitch angle is controlled based on
the pitch angle demand value [3*. On the other hand, in the
power demand value arithmetic unit 53, the reactive power
demand value is calculated based on the inputted active power
demand value and the power factor demand value, and these
demand values are provided to the converter control unit 21.
The converter control unit 21 controls the power converting
unit 20 based on the provided active power demand value and reactive power demand value. As a result, the active power and the reactive power according to the active power demand value and the reactive power demand value are supplied to the utility grid 2.
In a case of repeatedly performing such a control, when a request for changing the maximum value of the active power and the maximum value P1 of the newly defined active power are received from the utility grid 2 side, the first information is changed by the changing unit 52 so that the rated value P0 of the active power in the present first information becomes the maximum value P1 of the active power newly defined.
Concretely, the changing unit 52 gradually changes the
rated value P0 in the first information to the maximum value
P1 of the newly defined active power at the predetermined
change rate. In the transient period of the first
information, using the first information being changed, an
active power demand value corresponding to the rotor speed
detected by the rotor speed detecting unit 50 is obtained by
the demand value obtaining unit 51, and the obtained active
power demand value is provided to the blade control unit 22
and the power demand value arithmetic unit 53. Accordingly,
the active power demand value can be prevented from rapidly
increasing/decreasing. As a result, the amount of active
power supplied to the utility grid 2 can be gently changed to the maximum value of the active power newly defined.
After the change of the first information by the changing unit 52 is completed, that is, when the rated value of the first information reaches the newly defined maximum value P1 of the active power, control of the active power value based on the changed first information is performed until a demand of changing the maximum value of active power is received again.
In the wind turbine generator 1 and the method of
controlling the same according to the present embodiment, the
changing unit 52 gradually changes the maximum value of the
active power demand value of the first information which is
set to the rated value to the newly defined maximum value of
active power at a predetermined change rate, so that the
active power demand value can be prevented from being rapidly
changed in response to a request for changing the maximum
value of active power. As a result, by setting the
predetermined change rate to a change rate to suppress
fluctuations in the voltage value or frequency fluctuations
of the utility grid to a predetermined value or less, a rapid
change of the maximum value of the active power demand value
which is set to the rated value can be prevented, and the
frequency fluctuation or power fluctuation in the utility
grid can be suppressed to the predetermined value or less.
Although the speed of the rotor is defined as the operation state parameter detected by the rotor speed detecting unit 50 (detecting unit) in the present embodiment, the present invention is not limited thereto. For example, as the operation state parameter detected by the detecting unit, excitation current of the rotor may be used in place of the speed of the rotor.
Modification 1
In a case where the changing unit 52 according to the present embodiment changes the maximum value of active power at a predetermined change rate or less, a change rate "b" is calculated based on the difference (P0 - P1) between the active power maximum value before the change and the active power maximum value after the change and time T taken for the change, and the maximum value is changed at the change rate "b" equal to or less than the predetermined change rate "a". However, the present invention is not limited to the present embodiment. For example, it is alternatively possible to specify a change rate equal to or less than the predetermined change rate "a", that is, a change amount of the active power per unit time, and change the maximum value of active power based on the specified change rate.
Modification 2
In the present embodiment, the changing unit 52 changes the maximum value of the active power demand value of the first information held by the demand value obtaining unit 51 to the newly defined maximum value of active power at a predetermined change rate specified or less. The present invention, however, is not limited to the present embodiment. For example, the changing unit 52 may have a plurality of pieces of second information in which the maximum values of the active power demand values are set as values different from the rated value PO of the first information and, in a case where a request to change the maximum value of active power is received from the utility grid side, the active power demand value may be gradually changed by using the plurality of pieces of second information.
For example, the changing unit 52 may change the active
power demand value step by step by extracting, from the
plurality of pieces of second information, a plurality of
pieces of second information in which the maximum value of
the active power demand value is between the rated value PO
of the first information and the newly defined maximum value
of active power, and employing in order, out of the extracted
second information, from second information having the
maximum value of the active power demand value close to the
rated value PO to second information having the maximum value
of active power demand value close to the newly defined
maximum value of active power.
As described above, the second information preliminarily held in the changing unit 52 is outputted to the demand value obtaining unit 51, and the demand value obtaining unit 51 outputs the active power demand value based on the second information. Therefore, the active power demand value can be promptly outputted to the power demand value arithmetic unit 53.
In a case where the changing unit 52 according to the
present embodiment changes the active power demand value in
the first information, which is set to the rated value, to
the newly defined maximum value of active power, it is
sufficient that the maximum value of the active power demand
value before the change coincides with the maximum value of
active power newly defined in the end. The method of changing
an active power demand value other than the maximum value is
not specifically limited. For example, in a case where the
first information is expressed in a graph as shown in FIG. 2,
the graph may be reduced without changing the shape of the
graph and the maximum value of the active power demand value
may be made coincide with the newly defined maximum value, or
the active power demand value of the first information before
the change may be used as it is as the active power demand
value other than the maximum value of the active power demand
value. Such a method of changing the characteristic of the
first information is based on a predetermined algorithm.
Although the first information is expressed in the graph in the present embodiment, the first information is not limited thereto. Concretely, it is sufficient that the operation state parameter and the active power demand value are associated with each other. For example, the first information may be provided in the form of a mathematical expression or a table.

WE CLAIM:
1. A wind turbine generator, wherein in a case where a request for changing a maximum value of active power and a newly defined maximum value of active power are received from a utility grid side, a maximum value of an active power demand value set to a rated value is changed to the newly defined maximum value of active power at a predetermined change rate or less.
2. The wind turbine generator according to claim 1, comprising:
a detecting unit for detecting a parameter related to an operation state;
a demand value obtaining unit for storing first information in which the parameter related to the operation state and an active power demand value are associated with each other, and obtaining an active power demand value corresponding to the operation state parameter detected by the detecting unit based on the first information; and
a changing unit for changing, in a case where a request
for changing a maximum value of active power and a newly
defined maximum value of active power are received from the
utility grid side, a maximum value of an active power demand
value in the first information, which is set to a rated
value, to the newly defined maximum value of active power at
the predetermined change rate or less.
3. The wind turbine generator according to claim 1 or 2, wherein the changing unit calculates the change rate by dividing a difference between the active power demand value set to the rated value and the newly defined maximum value of active power by predetermined time required for the change, and employs the calculated change rate in a case where the calculated change rate is equal to or less than the predetermined change rate, while employing the predetermined change rate in a case where the calculated change rate exceeds the predetermined change rate preliminarily set.
4. The wind turbine generator according to claim 1, further
comprising a plurality of pieces of second information in
which a parameter related to an operation state and an active
power demand value are associated with each other and maximum
values of the active power demand values are different from
each other, for changing, in a case where a request for
changing a maximum value of active power and a newly defined
maximum value of active power are received from the utility
grid side, an active power demand value set to a rated value
step by step by using the second information in which the
maximum value of the active power demand value is between the
rated active power value and the maximum value of active
power newly defined.
5. A wind farm comprising a plurality of wind turbine generators, wherein at least one of the plurality of wind turbine generators is the wind turbine generator according to any one of claims 1 to 4.
6. A method of controlling a wind turbine generator, wherein in a case where a request for changing a maximum value of active power and a newly defined maximum value of active power are received from a utility grid side, a maximum value of an active power demand value, which is set to a rated value, is changed to the newly defined maximum value of active power at a predetermined change rate or less.
7. A method of controlling a wind farm having a plurality of wind turbine generators, wherein the method of controlling a wind turbine generator according to claim 6 is applied to at least one of the plurality of wind turbine generators.
8. A wind turbine generator substantially as herein described with reference to and as illustrated by the accompanying figures.
9. A method of controlling a wind turbine generator substantially as herein described with reference to and as illustrated by the accompanying figures.