CN107436176B - Method and device for determining natural vibration frequency of doubly-fed wind generator system - Google Patents
Method and device for determining natural vibration frequency of doubly-fed wind generator system Download PDFInfo
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Abstract
The invention discloses a method and a device for determining the natural vibration frequency of a doubly-fed wind generator system, wherein the method comprises the steps of controlling the variable pitch angle of the doubly-fed wind generator system to enable the rotating speed of a generator rotor to be stabilized at a set rotating speed value; detecting the rotating speed of the rotor while adjusting the exciting current frequency of the rotor, extracting a signal representing the mechanical vibration of the generator from the rotating speed, and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the signal; and determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs. The method does not need to add a sensor, simplifies the system structure and saves the cost. Meanwhile, the control algorithm is simple and reliable, and is easy to realize in engineering.
Description
Technical Field
The invention belongs to the technical field of wind power generation, and particularly relates to a method and a device for determining the natural vibration frequency of a doubly-fed wind power generator system.
Background
Wind power generation is one of the most potential renewable energy technologies as an environment-friendly power generation mode which does not pollute the environment and utilizes renewable resources. Has become a hot spot and a key point of competitive development of countries in the world, and has wide market prospect. With the increase of the number of the wind power generator sets and the increase of the capacity, the quality problem of the fan is more and more prominent, and the reliability of the wind power generator set used as a generator of a key part of the fan is more emphasized by wind power owners and related technical research personnel.
The vibration of the wind driven generator can reduce the efficiency of the generator, accelerate the abrasion of a bearing, loosen a generator fixing element and the like, finally cause a safety accident, and become an important factor influencing the reliability of the wind driven generator. Various causes of vibration of the wind turbine generator, such as imbalance during installation of the generator, bearing deformation and grease degradation caused by heat generation during long-term operation, or periodic electromagnetic force caused by interaction of magnetic fields of a stator and a rotor of the generator, are also reflected on mechanical vibration of movable parts of the generator. Most of the double-fed wind driven generators are mainly installed on an elastic supporting platform in a high-altitude fan cabin cover, so that severe vibration is more easily caused.
At present, the method for determining the natural vibration frequency of the doubly-fed wind generator system is mainly based on the detection of an acceleration sensor, so that the cost of the system is increased. And most sensors are modeled based on complex algorithms, so that the engineering application is difficult.
In view of the above, a method for determining the natural vibration frequency of the doubly-fed wind generator system without using an acceleration sensor is needed to solve the above problems.
Disclosure of Invention
One of the technical problems to be solved by the present invention is to provide a method for determining the natural vibration frequency of the doubly-fed wind generator system without an acceleration sensor.
In order to solve the above technical problem, an embodiment of the present application first provides a method for determining a natural frequency of a doubly-fed wind generator system, including controlling a pitch angle of the doubly-fed wind generator system, so that a rotating speed of a generator rotor is stabilized at a set rotating speed value; detecting the rotating speed of the rotor while adjusting the exciting current frequency of the rotor, extracting a signal representing the mechanical vibration of the generator from the rotating speed, and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the signal; and determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs.
Preferably, before controlling the variable pitch angle of the doubly-fed wind generator system to stabilize the rotating speed of the generator rotor at the set rotating speed value, the method further comprises disconnecting the doubly-fed wind generator system from the power grid.
Preferably, the signal indicative of the mechanical vibrations of the generator comprises a harmonic component signal of 1 times the grid voltage frequency.
Preferably, extracting from said rotation speed a signal representative of the mechanical vibrations of the generator comprises: filtering harmonic component signals of 1 time of power grid voltage frequency in the rotating speed by using a wave trap to obtain other harmonic component signals; and subtracting the other harmonic component signals from the rotating speed to obtain a signal representing the mechanical vibration of the generator.
Preferably, the determining whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate according to the signal includes: when the peak value of the signal representing the mechanical vibration of the generator is greater than or equal to a set threshold value, judging that the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate; when the peak value of the signal representing the mechanical vibration of the generator is smaller than a set threshold value, repeatedly adjusting the exciting current frequency of the rotor and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not based on the rotating speed of the rotor.
Preferably, the determining the natural frequency of vibration of the doubly-fed wind generator system from the frequency of the voltage of the stator output at which the resonance occurs comprises: establishing a relation model of the rotating speed of the rotor, the exciting current frequency of the rotor and the frequency of the voltage output by the stator; and determining the frequency of the voltage output by the stator when the resonance occurs according to the model, and determining the frequency as the natural vibration frequency of the doubly-fed wind generator system.
Preferably, a relational model of the rotational speed of the rotor, the excitation current frequency of the rotor, and the frequency of the voltage output by the stator is established according to the following expressions:
wherein f is1Frequency of voltage output for stator, f2Is the excitation current frequency of the rotor, nrThe number of pole pairs of the generator is p, which is the rotational speed of the rotor.
Preferably, an inverter is used to adjust the excitation current frequency of the rotor.
Preferably, the set rotating speed value is selected according to the number of pole pairs of the generator, and if the number of pole pairs is 3, the range of the set rotating speed value is 700-900 r/min; if the number of pole pairs is 2, the range of the set rotating speed value is 1200-1400 r/min.
The embodiment of the application also provides a device for determining the natural vibration frequency of the doubly-fed wind generator system, which comprises the following steps: the rotating speed setting module is used for controlling the variable pitch angle of the doubly-fed wind generator system so as to enable the rotating speed of the generator rotor to be stabilized at a set rotating speed value; the rotating speed adjusting and detecting module is used for adjusting the exciting current frequency of the rotor and detecting the rotating speed of the rotor at the same time, extracting a signal representing the mechanical vibration of the generator from the rotating speed, and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the signal; and the frequency determining module is used for determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the natural vibration frequency of the doubly-fed wind generator system is determined by adjusting the exciting current frequency of the rotor and based on a relation model of the rotating speed of the rotor, the exciting current frequency of the rotor and the frequency of the voltage output by the stator during electromagnetic resonance, a sensor is not required to be added, the system structure is simplified, and the cost is saved. Meanwhile, the control algorithm is simple and reliable, and is easy to realize in engineering.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings are included to provide a further understanding of the technology or prior art of the present application and are incorporated in and constitute a part of this specification. The drawings expressing the embodiments of the present application are used for explaining the technical solutions of the present application, and should not be construed as limiting the technical solutions of the present application.
FIG. 1 is a schematic flow chart of a method for determining natural vibration frequency of a doubly-fed wind generator system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a doubly-fed wind generator;
fig. 3 is a schematic structural diagram of an apparatus for determining the natural frequency of the doubly-fed wind generator system according to another embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the accompanying drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the corresponding technical effects can be fully understood and implemented. The embodiments and the features of the embodiments can be combined without conflict, and the technical solutions formed are all within the scope of the present invention.
The vibration of the wind turbine is caused by mechanical vibration and electromagnetic vibration. Electromagnetic resonance may also occur if the inherent mechanical vibration frequency of the stator and rotor machine itself is close to the electromagnetic vibration frequency of the stator and rotor core. In an embodiment of the present invention, a method for detecting a natural frequency of a doubly-fed wind turbine system based on electromagnetic resonance is provided, as shown in fig. 1, the method includes:
and S110, controlling the variable pitch angle of the doubly-fed wind generator system to enable the rotating speed of the generator rotor to be stabilized at a set rotating speed value.
And step S120, detecting the rotating speed of the rotor while adjusting the exciting current frequency of the rotor, extracting a signal representing the mechanical vibration of the generator from the rotating speed, and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the extracted signal.
And S130, determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs.
In step S110, before controlling the pitch angle of the doubly-fed wind generator system and stabilizing the rotation speed of the rotor, the doubly-fed wind generator system needs to be disconnected from the grid even if the generator exits the grid-connected power generation state. And then, controlling the variable pitch angle of the doubly-fed wind generator by using a control system of the wind turbine generator so as to stabilize the rotating speed of the rotor of the generator on a set rotating speed value.
The set rotating speed value is generally the synchronous rotating speed of the low generator and can be selected according to the pole pair number of the generator. For example, if the number of pole pairs is 3, the range of the set rotation speed value is 700-.
The doubly-fed wind generator is directly connected with a power grid, the stator of the generator must supply electric energy with the frequency near 50Hz to the power grid, meanwhile, the electric energy frequency of the rotor of the generator is also fixed to be 1/s of the stator frequency, and s is the slip ratio of the generator, so the electromagnetic vibration frequency of the stator and the rotor iron core of the generator is basically fixed. Namely, the electromagnetic vibration frequency of the stator core can only be around 50Hz, and the electromagnetic vibration frequency of the rotor core is generally 0-15 Hz. And because the encoder of the generator is fixed on the rotating shaft of the generator, the electromagnetic vibration frequency of the stator core can be superposed on the rotating speed signal of the rotor of the generator.
In step S120, the rotor speed is detected while adjusting the excitation current frequency of the rotor using a converter provided on the rotor side, and a harmonic component signal of 1 time the grid voltage frequency is extracted from the rotor speed to characterize the mechanical vibration of the generator under the action of the electromagnetic force.
Specifically, a wave trap is used for filtering harmonic component signals of 1 time of the grid voltage frequency in the rotating speed to obtain other harmonic component signals, and then the rotating speed signals are used for subtracting the other harmonic component signals to obtain signals representing the mechanical vibration of the generator. In one embodiment of the present invention, the transfer function of the employed trap is shown in expression (1):
in the formula, ω0The angular frequency of the trap, Q, is the quality factor. When ω is0When Q is 0.707 at 50Hz, the harmonic component signal at 50Hz in the rotating speed signal can be filtered.
If the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate with each other, the generator will vibrate violently, so the peak value of the signal representing the mechanical vibration of the generator will be increased. The set limit value is generally determined according to the amplitude of the signal representing the mechanical vibration of the generator when no resonance occurs, and for example, the amplitude 5 times that of the signal representing the mechanical vibration of the generator when no resonance occurs may be determined as the set limit value.
When the peak value of the signal representing the mechanical vibration of the generator is smaller than the set threshold value, the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator do not resonate at the moment, and the process of repeatedly adjusting the exciting current frequency of the rotor and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not based on the rotating speed signal of the rotor is repeated until the system generates electromagnetic resonance.
In step S130, a relational model of the rotational speed of the rotor, the excitation current frequency of the rotor, and the frequency of the voltage output from the stator is first established. And then determining the frequency of the voltage output by the stator when resonance occurs according to the obtained relation model, wherein the frequency of the voltage output by the stator is the natural vibration frequency of the doubly-fed wind generator system.
In particular, fig. 2 is a schematic view of a doubly-fed wind generator, as shown, f1And f2Respectively representing the frequency of the voltage output by the stator of the doubly-fed wind generator and the excitation current frequency of the rotor. n is1Is the rotational speed of the stator magnetic field, i.e. the synchronous rotational speed. n is2For the rotational speed of the rotor field relative to the rotor, nrThe rotating speed of the rotor of the doubly-fed wind generator is p pole pair number of the generator.
When the doubly-fed wind generator stably operates, the rotating magnetic fields of the stator and the rotor of the doubly-fed wind generator are relatively static, namely n1、n2And nrHas a relationship as shown in expression (2):
n1＝n2+nr(2)
and due to f1＝n1p/60，f2＝n2p/60, then:
from the expression (3), when the rotation speed n of the generator rotor is obtainedrWhen not changed, by adjusting the exciting current frequency f of the rotor2Capable of varying the frequency f of the voltage output by the stator1That is, in the embodiment of the present invention, it is feasible to obtain different voltage frequencies of the output of the stator core by adjusting the excitation current frequency of the rotor, so that the electromagnetic vibration of the stator and the rotor of the motor and the mechanical vibration of the generator resonate.
When the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate, the natural vibration frequency f of the doubly-fed wind generator system is further calculated according to the expression (3)n＝nrp/60+f2', wherein f2' is the excitation current frequency of the rotor at which resonance occurs, fnIs the natural vibration frequency of the doubly-fed wind generator system.
The embodiment of the invention provides a method for determining the natural vibration frequency of a doubly-fed wind generator system by adjusting the excitation current frequency of a rotor by using a converter based on electromagnetic resonance. Before the doubly-fed wind generator is not connected with a power grid, the frequency of voltage output by a stator of the generator is changed within a certain range by adjusting the frequency of exciting current of a rotor, and electromagnetic force vibration of a stator iron core is generated. And simultaneously detecting a rotating speed signal of the generator, judging whether the generator resonates with the inherent frequency of the stator and the rotor machine, and if the generator resonates, calculating the inherent vibration frequency of the doubly-fed wind driven generator system according to a relation model of the rotating speed of the rotor, the exciting current frequency of the rotor and the frequency of the voltage output by the stator.
According to the method, a speed sensor is not required to be added, and the system cost is saved. Meanwhile, the control algorithm is simple and reliable, and is easy to realize in an engineering mode.
In another embodiment of the present invention, an apparatus for determining the natural frequency of vibration of a doubly-fed wind generator system is further proposed, as shown in fig. 3, the apparatus comprising:
the rotation speed setting module 31 performs the operation of step S110 in the foregoing embodiment, the rotation speed adjusting and detecting module 32 performs the operation of step S120 in the foregoing embodiment, and the frequency determining module 33 performs the operation of step S130 in the foregoing embodiment, which is not described herein again.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A method of determining the natural vibration frequency of a doubly-fed wind generator system, comprising:
controlling the variable pitch angle of the doubly-fed wind generator system to stabilize the rotating speed of a generator rotor at a set rotating speed value;
the method comprises the following steps of adjusting the exciting current frequency of a rotor, detecting the rotating speed of the rotor, extracting a signal representing the mechanical vibration of a generator from the rotating speed, and judging whether the electromagnetic vibration of a stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the signal, wherein the method comprises the following steps:
when the peak value of the signal representing the mechanical vibration of the generator is greater than or equal to a set threshold value, judging that the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate;
when the peak value of the signal representing the mechanical vibration of the generator is smaller than a set threshold value, repeatedly adjusting the exciting current frequency of the rotor and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not based on the rotating speed of the rotor;
and determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs.
2. The method of claim 1, wherein before controlling the pitch angle of the doubly-fed wind generator system to stabilize the rotational speed of the generator rotor at the set rotational speed value, the method further comprises disconnecting the doubly-fed wind generator system from the grid.
3. The method of claim 2, wherein the signal indicative of generator mechanical vibration comprises a harmonic component signal of 1 grid voltage frequency.
4. The method of claim 3, wherein said extracting a signal indicative of generator mechanical vibration from said rotational speed comprises:
filtering harmonic component signals of 1 time of power grid voltage frequency in the rotating speed by using a wave trap to obtain other harmonic component signals;
and subtracting the other harmonic component signals from the rotating speed to obtain a signal representing the mechanical vibration of the generator.
5. The method according to any one of claims 1 to 4, wherein determining the natural vibration frequency of the doubly-fed wind generator system from the frequency of the voltage of the stator output at which resonance occurs comprises:
establishing a relation model of the rotating speed of the rotor, the exciting current frequency of the rotor and the frequency of the voltage output by the stator according to the following expression;
wherein f is1Frequency of voltage output for stator, f2Is the excitation current frequency of the rotor, nrThe rotating speed of the rotor is shown, and p is the pole pair number of the generator;
and determining the frequency of the voltage output by the stator when the resonance occurs according to the model, and determining the frequency as the natural vibration frequency of the doubly-fed wind generator system.
6. A method according to claim 5, characterized in that the excitation current frequency of the rotor is adjusted using a current transformer.
7. The method as claimed in claim 1, wherein the set rotational speed value is selected according to the number of pole pairs of the generator, and if the number of pole pairs is 3, the set rotational speed value is in the range of 700-900 r/min; if the number of pole pairs is 2, the range of the set rotating speed value is 1200-1400 r/min.
8. An apparatus for determining the natural frequency of vibration of a doubly-fed wind generator system, comprising:
the rotating speed setting module is used for controlling the variable pitch angle of the doubly-fed wind generator system so as to enable the rotating speed of the generator rotor to be stabilized at a set rotating speed value;
the rotating speed adjusting and detecting module is used for adjusting the exciting current frequency of the rotor and detecting the rotating speed of the rotor at the same time, extracting a signal representing the mechanical vibration of the generator from the rotating speed, and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not according to the signal, and comprises the following steps:
when the peak value of the signal representing the mechanical vibration of the generator is greater than or equal to a set threshold value, judging that the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate;
when the peak value of the signal representing the mechanical vibration of the generator is smaller than a set threshold value, repeatedly adjusting the exciting current frequency of the rotor and judging whether the electromagnetic vibration of the stator and the rotor of the generator and the mechanical vibration of the generator resonate or not based on the rotating speed of the rotor;
and the frequency determining module is used for determining the natural vibration frequency of the doubly-fed wind generator system according to the frequency of the voltage output by the stator when the resonance occurs.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103321854A (en) * | 2013-05-29 | 2013-09-25 | 国家电网公司 | Vibration control method for wind generator set tower |
| CN105403402A (en) * | 2015-11-12 | 2016-03-16 | 科诺伟业风能设备（北京）有限公司 | Method for monitoring torsional vibration state of driving chain system of wind generating set |
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| US7970556B2 (en) * | 2009-01-30 | 2011-06-28 | General Electric | System and method for monitoring the condition of a gear assembly |
| US8482456B2 (en) * | 2010-12-16 | 2013-07-09 | General Electric Company | Sensor assembly and method of measuring the proximity of a machine component to an emitter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103321854A (en) * | 2013-05-29 | 2013-09-25 | 国家电网公司 | Vibration control method for wind generator set tower |
| CN105403402A (en) * | 2015-11-12 | 2016-03-16 | 科诺伟业风能设备（北京）有限公司 | Method for monitoring torsional vibration state of driving chain system of wind generating set |
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