Radial air gap eccentricity fault detection method and system for doubly-fed induction generator based on rotor vibration characteristics

Abstract

The present invention discloses a method and system for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics, which belongs to the field of generator fault detection and includes the following steps: S1, using an acceleration sensor to monitor the acceleration signal of the rotor of the generator to be detected, and uploading the acceleration signal to a host computer with the help of a signal acquisition instrument; S2, the host computer determines whether a radial air gap eccentricity fault occurs according to the received acceleration signal, and determines the type and degree of the eccentricity fault after determining that the eccentricity fault occurs: S21, using Fourier transform to convert the acceleration signal into a vibration signal, and determine whether a new frequency component of the vibration signal appears, if so, executing step S22, otherwise, determining that the generator to be detected is normal; S22, determining the type and degree of the eccentricity fault according to the frequency component and amplitude change of the vibration signal; S23, outputting and displaying the type and degree of the eccentricity fault. The present invention adopts the above-mentioned method and system for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics, which can detect the radial air gap eccentricity fault of the generator at an early stage to avoid further expansion of losses.

Description

Technical Field

[0001] The invention relates to the technical field of generator fault detection, and in particular to a method and system for detecting radial air gap eccentricity fault of a double-fed induction generator based on rotor vibration characteristics. Background Art

[0002] As an important power generation equipment, the doubly-fed induction generator has high power density and good operating performance, and is widely used in fields such as wind power generation.

[0003] However, due to factors such as harsh environment, complex working conditions and long-term operation, the doubly-fed induction generator is prone to air gap eccentricity faults. These faults mainly include radial static air gap eccentricity, radial dynamic air gap eccentricity and radial mixed air gap eccentricity. When the generator has an air gap eccentricity fault, it will cause magnetic field distortion in the air gap, which will in turn aggravate the vibration of the stator and rotor, increase losses, reduce energy conversion efficiency, and cause insulation wear of the winding. In severe cases, it may cause bending wear of the rotor, insulation breakdown of the winding, and even cause the burning of the generator, resulting in serious economic losses and safety hazards. Therefore, it is necessary to detect the air gap eccentricity fault of the generator.

[0004] The existing research on air gap eccentricity fault detection of generators is as follows:

[0005] CN202310425801.1 discloses a generator fault detection method based on the air gap magnetic flux density characteristics, which includes the following steps: S1: installing a detection device in the generator and building a test platform; S2: obtaining an air gap magnetic flux density signal through the detection device; S3: using fast Fourier transform to transform the time domain signal of the magnetic flux density into a frequency domain signal; S4: judging whether the generator has air gap eccentricity or stator inter-turn short circuit fault by comparing the time domain and frequency domain; S5: obtaining the value of the air gap magnetic flux density by calculation, selecting the root mean square value of the magnetic flux density under different working conditions, and then comparing it with the root mean square value of the magnetic flux density under normal conditions to determine the severity of the fault.

[0006] It can be seen that the existing generator air gap eccentricity fault detection method has the following defects:

[0007] 1. The sensor needs to be installed in the air gap, which is an invasive or semi-invasive detection, which is inconvenient in actual engineering applications;

[0008] 2. The generator detection equipment only has temperature and vibration sensors. The detection of magnetic flux density and other parameters requires additional sensors, which is not conducive to practical promotion. Summary of the invention

[0009] To solve the above problems, the present invention provides a method and system for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics, which can detect radial air gap eccentricity fault of the generator at an early stage to avoid further expansion of losses. Compared with the prior art, there is no need to add additional sensors. Fault diagnosis can be achieved by simply adding signal processing steps on the basis of the original vibration sensor, which is more convenient.

[0010] To achieve the above object, the present invention provides a method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics, comprising the following steps:

[0011] S1. Use an acceleration sensor to monitor the acceleration signal of the generator rotor to be tested, and upload the acceleration signal to the host computer with the help of a signal acquisition instrument;

[0012] S2. The host computer determines whether a radial air gap eccentricity fault occurs based on the received acceleration signal, and determines the type and degree of the eccentricity fault after determining that an eccentricity fault occurs:

[0013] S21, converting the acceleration signal into a vibration signal by Fourier transform, and determining whether a new frequency component of the vibration signal appears, if so, executing step S22, otherwise determining that the generator to be detected is normal;

[0014] S22, determining the type and degree of the eccentricity fault according to the frequency component and amplitude change of the vibration signal;

[0015] S23, output displays the eccentricity fault type and fault degree.

[0016] Preferably, in step S1, the channel measured by the acceleration sensor is first balanced and cleared.

[0017] Preferably, in step S2, the permeance per unit area of ​​the generator to be detected when it is normal is set to:

[0018]

[0019] In the formula, α m is the circular angle of the air gap, t is the time, and g is the circular angle α at time t. m The radial air gap length corresponds to the air gap, Λ0 is the air gap permeability constant, The harmonic permeance is generated when the stator is slotted and the rotor surface is smooth. is the harmonic permeability generated when the rotor is slotted and the stator surface is smooth. It is the harmonic permeability generated by the interaction between the stator and the rotor when slotting simultaneously; k1 = ±1, ±2..., k2 = ±1, ±2...;

[0020] The air gap lengths when the generator to be tested is operating normally and when a radial air gap eccentricity fault occurs are set as follows:

[0021]

[0022] In the formula, ω r is the mechanical angular velocity of the rotor; δ s is the radial static eccentricity of the air gap; δ d is the radial dynamic eccentricity of the air gap;

[0023] The permeability per unit area is obtained from equations (1) and (2):

[0024]

[0025] Air gap angle α m At , the magnetomotive force of the generator to be tested is:

[0026]

[0027] In the formula, f p (α m ,t) is the main wave synthetic magnetomotive force, f v (α m ,t) is the stator winding harmonic magnetomotive force, f μ (α m , t) is the harmonic magnetomotive force of the rotor winding, p is the number of pole pairs of the generator to be tested, v and μ are the spatial orders corresponding to the stator and rotor of the generator to be tested respectively;

[0028] And f p (α m ,t),f v (α m ,t),f μ (α m ,t) is expressed as:

[0029]

[0030] Where, F0 is the amplitude of the main wave synthetic magnetomotive force, F v is the amplitude of the harmonic magnetomotive force of the stator winding, F μ is the amplitude of harmonic magnetomotive force of rotor winding, is the initial phase angle of the main wave synthetic magnetomotive force, is the stator v-order harmonic magnetomotive force, is the rotor μ-order harmonic magnetomotive force, ω1 is the electrical angular velocity of the generator to be measured, ω μ is the angular frequency of the μ-order harmonic magnetomotive force of the rotor relative to the stator, Z1 and Z2 are the number of slots in the stator and rotor respectively;

[0031] Among them, ω μThe expression is as follows:

[0032] ω μ =ω1[1+k2Z2(1-s) / p] (6)

[0033] Where, s is the slip rate of the generator to be tested;

[0034] The magnetic flux density before and after eccentricity is obtained by equations (3) and (4):

[0035]

[0036] According to the Maxwell tensor method, the radial magnetic pull per unit area on the stator surface of the generator to be tested is obtained:

[0037]

[0038] Where, μ0 is the vacuum magnetic permeability; B is the magnetic flux density;

[0039] Integrate the radial magnetic pull per unit area along the circumferential direction to obtain the unbalanced magnetic pull of the rotor:

[0040]

[0041] In the formula, F X 、F Y are the unbalanced magnetic pulls in the X and Y directions respectively; L is the axial length of the rotor; R is the rotor radius;

[0042] The relationship between exciting force and vibration:

[0043] {[m]{y″(t)}+[D]{y′(t)}+[K]{y(t)}={f(t)} (10)

[0044] Where, [m] is the mass matrix of the rotor mass point, [D] is the radial damping matrix, [K] is the radial stiffness matrix, y(t) is the displacement of the unit mass point, y′(t) is the velocity, y″(t) is the acceleration, and f(t) is the exciting force of the system, that is, the unbalanced magnetic pull of the rotor;

[0045] The obtained vibration frequency component is consistent with the exciting force frequency component, and then the exciting force frequency component is obtained from the frequency component of the vibration signal, so as to judge whether an eccentricity fault occurs and the severity of the fault.

[0046] Preferably, ω1 = 50 Hz;

[0047] s = 2.7%, that is, the rotor rotation speed is 1460rmp, k2 = ±1 vibration frequency f μ =535Hz or 635Hz.

[0048] Preferably, in step S21, Fourier transform is used to decompose a function (usually a function in the time domain) into a set of frequency components. Its main formula is as follows:

[0049]

[0050] Wherein, X(f) is a complex function in the frequency domain, which represents the frequency component of the original function x(t) at frequency f.

[0051] Preferably, in step S22, when (f μ -f1) When the vibration frequency is high, it is determined that the generator to be tested has a radial static air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree;

[0052] When f appears at the same time r and f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial dynamic air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree;

[0053] When it appears at the same time (f μ -f1),f r 、f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial mixed air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the degree of the fault.

[0054] Preferably, f μ -f1=485Hz or 585Hz; f r =25Hz; f1-(f μ ±f1)=460Hz, 510Hz, 560Hz or 610Hz.

[0055] Preferably, in step S21, a vibration characteristic curve at the rotor bearing seat is drawn and stored using a host computer, and at the same time, the frequency component and amplitude change of the vibration signal are read according to the vibration characteristic curve.

[0056] A system for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics comprises a generator to be detected, a drive motor and an acceleration sensor, wherein the rotor of the generator to be detected is connected to the output shaft of the drive motor, an acceleration sensor is arranged on the side of the rotor bearing seat of the generator to be detected, the acceleration sensor is connected to the input end of a signal acquisition instrument, and the output end of the signal acquisition instrument communicates with a host computer;

[0057] Wherein, the acceleration sensor is used to collect the acceleration signal of the rotor of the generator to be tested;

[0058] Signal acquisition instrument, used to upload acceleration signals to the host computer;

[0059] The upper computer is used to judge whether an eccentricity fault occurs according to the acceleration signal, and to determine the type and degree of the eccentricity fault after judging that the eccentricity fault occurs.

[0060] The present invention has the following beneficial effects:

[0061] 1. The radial air gap eccentricity fault of the generator can be detected at an early stage to avoid further loss;

[0062] 2. It can not only determine whether an air gap eccentricity fault occurs, but also determine the type and degree of the fault, which is more practical.

[0063] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a flow chart of a method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics of the present invention;

[0065] Figure 2 It is a structural diagram of the system of the method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics of the present invention.

[0066] Among them: 1. Generator to be tested; 2. Acceleration sensor; 3. Signal acquisition instrument; 4. Drive motor; 5. Host computer. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0068] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0069] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0070] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0071] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] like Figure 1 As shown, a method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics comprises the following steps:

[0073] S1. Use an acceleration sensor to monitor the acceleration signal of the generator rotor to be tested, and upload the acceleration signal to the host computer with the help of a signal acquisition instrument;

[0074] In step S1, the channel measured by the acceleration sensor is first balanced and cleared.

[0075] S2. The host computer determines whether a radial air gap eccentricity fault occurs based on the received acceleration signal, and determines the type and degree of the eccentricity fault after determining that an eccentricity fault occurs:

[0076] S21, converting the acceleration signal into a vibration signal by Fourier transform, and determining whether a new frequency component of the vibration signal appears, if so, executing step S22, otherwise determining that the generator to be detected is normal;

[0077] S22, determining the type and degree of the eccentricity fault according to the frequency component and amplitude change of the vibration signal;

[0078] S23, output displays the eccentricity fault type and fault degree.

[0079] In step S2, the permeance per unit area of ​​the generator to be tested is set to be normal:

[0080]

[0081] In the formula, α m is the circular angle of the air gap, t is the time, and g is the circular angle α at time t. m The radial air gap length corresponds to the air gap, Λ0 is the air gap permeability constant, The harmonic permeance is generated when the stator is slotted and the rotor surface is smooth. is the harmonic permeability generated when the rotor is slotted and the stator surface is smooth. It is the harmonic permeability generated by the interaction between the stator and the rotor when slotting simultaneously; k1 = ±1, ±2..., k2 = ±1, ±2...;

[0082] The air gap lengths when the generator to be tested is operating normally and when a radial air gap eccentricity fault occurs are set as follows:

[0083]

[0084] In the formula, ω r is the mechanical angular velocity of the rotor; δ s is the radial static eccentricity of the air gap; δ d is the radial dynamic eccentricity of the air gap;

[0085] The permeance per unit area is obtained from equations (1) and (2):

[0086]

[0087] Air gap angle α m At , the magnetomotive force of the generator to be tested is:

[0088]

[0089] In the formula, f p (α m ,t) is the main wave synthetic magnetomotive force, f v (α m ,t) is the stator winding harmonic magnetomotive force, f μ (α m , t) is the harmonic magnetomotive force of the rotor winding, p is the number of pole pairs of the generator to be tested, v and μ are the spatial orders corresponding to the stator and rotor of the generator to be tested respectively;

[0090] And f p (α m ,t),f v (α m ,t),f μ (α m ,t) is expressed as:

[0091]

[0092] Where, F0 is the amplitude of the main wave synthetic magnetomotive force, F v is the amplitude of the harmonic magnetomotive force of the stator winding, F μ is the amplitude of harmonic magnetomotive force of rotor winding, is the initial phase angle of the main wave synthetic magnetomotive force, is the stator v-order harmonic magnetomotive force, is the rotor μ-order harmonic magnetomotive force, ω1 is the electrical angular velocity of the generator to be measured, ω μ is the angular frequency of the μ-order harmonic magnetomotive force of the rotor relative to the stator, Z1 and Z2 are the number of slots in the stator and rotor respectively;

[0093] Among them, ω μ The expression is as follows:

[0094] ω μ =ω1[1+k2Z2(1-s) / p] (6)

[0095] Where, s is the slip rate of the generator to be tested;

[0096] The magnetic flux density before and after eccentricity is obtained by equations (3) and (4):

[0097]

[0098] According to the Maxwell tensor method, the radial magnetic pull per unit area on the stator surface of the generator to be tested is obtained:

[0099]

[0100] Where, μ0 is the vacuum magnetic permeability; B is the magnetic flux density;

[0101] Integrate the radial magnetic pull per unit area along the circumferential direction to obtain the unbalanced magnetic pull of the rotor:

[0102]

[0103] In the formula, F X 、F Y are the unbalanced magnetic pulls in the X and Y directions respectively; L is the axial length of the rotor; R is the rotor radius.

[0104] The relationship between exciting force and vibration:

[0105] {[m]{y″(t)}+[D]{y′(t)}+[K]{y(t)}={f(t)} (10)

[0106] Where, [m] is the mass matrix of the rotor mass point, [D] is the radial damping matrix, [K] is the radial stiffness matrix, y(t) is the displacement of the unit mass point, y′(t) is the velocity, y″(t) is the acceleration, and f(t) is the exciting force of the system, that is, the unbalanced magnetic pull of the rotor;

[0107] The obtained vibration frequency component is consistent with the exciting force frequency component, and then the exciting force frequency component is obtained from the frequency component of the vibration signal, so as to judge whether an eccentricity fault occurs and the severity of the fault.

[0108] Preferably, in step S21, Fourier transform is used to decompose a function (usually a function in the time domain) into a set of frequency components. Its main formula is as follows:

[0109]

[0110] Wherein, X(f) is a complex function in the frequency domain, which represents the frequency component of the original function x(t) at frequency f.

[0111] In step S22, when (f μ -f1) When the vibration frequency is high, it is determined that the generator to be tested has a radial static air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree;

[0112] When f appears at the same time r and f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial dynamic air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree;

[0113] When it appears at the same time (f μ -f1),f r 、f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial mixed air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the degree of the fault.

[0114] f μ -f1=485Hz or 585Hz; f r =25Hz; f1-(f μ ±f1)=460Hz, 510Hz, 560Hz or 610Hz.

[0115] In step S21, a vibration characteristic curve at the rotor bearing seat is drawn and stored by a host computer, and the frequency component and amplitude change of the vibration signal are read according to the vibration characteristic curve.

[0116] Example

[0117] Taking a 5.5kW doubly-fed wind turbine as an example, its main parameters are shown in Table 1.

[0118] Table 1 Main parameters of doubly-fed wind turbine generator

[0119]

[0120] The fault detection results are as follows:

[0121] Case 1: The unbalanced magnetic pull of the rotor is zero, there is a slight vibration at the bearing seat due to problems such as stator vibration transmission, and the generator operates normally;

[0122] Case 2: The rotor is subjected to an unbalanced magnetic pull in a fixed direction, with a frequency of (f μ -f1)(485 / 585Hz) vibration, the generator will have radial static air gap eccentricity, and the greater the amplitude of the vibration and characteristic frequency components, the greater the degree of eccentricity;

[0123] Case 3: The rotor is subjected to an unbalanced magnetic pull with a changing direction and a frequency of f r (25Hz) and f1-(f μ ±f1)(460 / 510 / 560 / 610Hz) vibration, the generator will have radial dynamic air gap eccentricity, and the greater the amplitude of the vibration and characteristic frequency components, the greater the degree of eccentricity;

[0124] Case 4: The rotor is subjected to an unbalanced magnetic pull with a changing direction and a frequency of (f μ -f1)(485 / 585Hz),f r (25), f1-(f μ ±f1)(460 / 510 / 560 / 610Hz) vibration, the generator will have radial mixed air gap eccentricity, and the greater the amplitude of the vibration and characteristic frequency components, the greater the degree of eccentricity;

[0125] like Figure 2 As shown, a system of a method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics comprises a generator 1 to be detected, a drive motor 4 and an acceleration sensor 2, wherein the rotor of the generator 1 to be detected is connected to the output shaft of the drive motor 4, the acceleration sensor 2 is arranged on the side of the rotor bearing seat of the generator 1 to be detected, the acceleration sensor 2 is connected to the input end of a signal acquisition instrument 3, and the output end of the signal acquisition instrument 3 communicates with a host computer 5; wherein the acceleration sensor 2 is used to collect the acceleration signal of the rotor of the generator 1 to be detected; the signal acquisition instrument 3 is used to upload the acceleration signal to the host computer 5; the host computer 5 is used to determine whether an eccentricity fault occurs according to the acceleration signal, and determine the type and degree of the eccentricity fault after determining that the eccentricity fault occurs.

[0126] Therefore, the present invention adopts the above-mentioned doubly-fed induction generator radial air gap eccentricity fault detection method and system based on rotor vibration characteristics, which can detect the radial air gap eccentricity fault of the generator at an early stage to avoid further expansion of losses.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics, characterized in that: The following steps are involved: S1. Use an acceleration sensor to monitor the acceleration signal of the generator rotor to be tested, and upload the acceleration signal to the host computer with the help of a signal acquisition instrument; In step S1, the channel measured by the acceleration sensor is first balanced and cleared; S2. The host computer determines whether a radial air gap eccentricity fault occurs based on the received acceleration signal, and determines the type and degree of the eccentricity fault after determining that an eccentricity fault occurs: S21, converting the acceleration signal into a vibration signal by Fourier transform, and determining whether a new frequency component of the vibration signal appears, if so, executing step S22, otherwise determining that the generator to be detected is normal; S22, determining the type and degree of the eccentricity fault according to the frequency component and amplitude change of the vibration signal; S23, output and display the type and degree of eccentricity fault; In step S2, the permeance per unit area of ​​the generator to be tested is set to be normal: In the formula, α m is the circular angle of the air gap, t is the time, and g is the circular angle α at time t. m The radial air gap length corresponds to the air gap, Λ0 is the air gap permeability constant, The harmonic permeance is generated when the stator is slotted and the rotor surface is smooth. is the harmonic permeability generated when the rotor is slotted and the stator surface is smooth. It is the harmonic permeability generated by the interaction between the stator and the rotor when slotting simultaneously; k1 = ±1, ±2..., k2 = ±1, ±2...; The air gap lengths when the generator to be tested is operating normally and when a radial air gap eccentricity fault occurs are set as follows: In the formula, ω r is the mechanical angular velocity of the rotor; δ s is the radial static eccentricity of the air gap; δ d is the radial dynamic eccentricity of the air gap; The permeance per unit area is obtained from equations (1) and (2): Air gap angle α m At , the magnetomotive force of the generator to be tested is: In the formula, f p (α m ,t) is the main wave synthetic magnetomotive force, f v (α m ,t) is the stator winding harmonic magnetomotive force, f μ (α m , t) is the harmonic magnetomotive force of the rotor winding, p is the number of pole pairs of the generator to be tested, v and μ are the spatial orders corresponding to the stator and rotor of the generator to be tested respectively; And f p (α m ,t),f v (α m ,t),f μ (α m ,t) is expressed as: Where, F0 is the amplitude of the main wave synthetic magnetomotive force, F v is the amplitude of the harmonic magnetomotive force of the stator winding, F μ is the amplitude of harmonic magnetomotive force of rotor winding, is the initial phase angle of the main wave synthetic magnetomotive force, is the stator v-order harmonic magnetomotive force, is the rotor μ-order harmonic magnetomotive force, ω1 is the electrical angular velocity of the generator to be measured, ω μ is the angular frequency of the μ-order harmonic magnetomotive force of the rotor relative to the stator, Z1 and Z2 are the number of slots in the stator and rotor respectively; Among them, ω μ The expression is as follows: oh μ =ω1[1+k2Z2(1-s) / p] (6) Where, s is the slip rate of the generator to be tested; The magnetic flux density before and after eccentricity is obtained by equations (3) and (4): According to the Maxwell tensor method, the radial magnetic pull per unit area on the stator surface of the generator to be tested is obtained: Where, μ0 is the vacuum magnetic permeability; B is the magnetic flux density; Integrate the radial magnetic pull per unit area along the circumferential direction to obtain the unbalanced magnetic pull of the rotor: In the formula, F X 、F Y are the unbalanced magnetic pulls in the X and Y directions respectively; L is the axial length of the rotor; R is the rotor radius; The relationship between exciting force and vibration: {[m]{y″(t)}+[D]{y′(t)}+[K]{y(t)}={f(t)} (10) Where, [m] is the mass matrix of the rotor mass point, [D] is the radial damping matrix, [K] is the radial stiffness matrix, y(t) is the displacement of the unit mass point, y′(t) is the velocity, y″(t) is the acceleration, and f(t) is the exciting force of the system, that is, the unbalanced magnetic pull of the rotor; The obtained vibration frequency component is consistent with the exciting force frequency component, and then the exciting force frequency component is obtained from the frequency component of the vibration signal, so as to judge whether an eccentricity fault occurs and the severity of the fault.

2. The method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics according to claim 1, characterized in that: ω1=50Hz; s = 2.7%, that is, the rotor rotation speed is 1460rmp, k2 = ±1; vibration frequency f μ =535Hz or 635Hz.

3. The method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics according to claim 1, characterized in that: In step S21, Fourier transform is used to decompose a function into a set of frequency components, and its formula is as follows: Wherein, X(f) is a complex function in the frequency domain, which represents the frequency component of the original function x(t) at frequency f.

4. The method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics according to claim 3, characterized in that: In step S22, when (f μ -f1) When the vibration frequency is high, it is determined that the generator to be tested has a radial static air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree; When f appears at the same time r and f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial dynamic air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the fault degree; When it appears at the same time (f μ -f1),f r 、f1-(f μ ±f1) vibration frequency, it is determined that the generator to be tested has a radial mixed air gap eccentricity fault, and the greater the change in frequency component and amplitude, the greater the degree of the fault.

5. The method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics according to claim 4, characterized in that: f μ -f1=485Hz or 585Hz; f r =25Hz; f1-(f μ ±f1)=460Hz, 510Hz, 560Hz or 610Hz.

6. The method for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics according to claim 1, characterized in that: In step S21, a vibration characteristic curve at the rotor bearing seat is drawn and stored by a host computer, and the frequency component and amplitude change of the vibration signal are read according to the vibration characteristic curve.

7. A system for detecting radial air gap eccentricity fault of a doubly-fed induction generator based on rotor vibration characteristics as claimed in any one of claims 1 to 6, characterized in that: The invention comprises a generator to be tested, a driving motor and an acceleration sensor, wherein the rotor of the generator to be tested is connected to the output shaft of the driving motor, the acceleration sensor is arranged on the side of the rotor bearing seat of the generator to be tested, the acceleration sensor is connected to the input end of the signal acquisition instrument, and the output end of the signal acquisition instrument communicates with the host computer; Wherein, the acceleration sensor is used to collect the acceleration signal of the rotor of the generator to be tested; Signal acquisition instrument, used to upload acceleration signals to the host computer; The host computer is used to judge whether an eccentricity fault occurs according to the acceleration signal, and to determine the type and degree of the eccentricity fault after judging that the eccentricity fault occurs.

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