CN112147548B - Method and device for detecting short-circuit fault of exciting winding of multiphase angular brushless exciting system - Google Patents
Method and device for detecting short-circuit fault of exciting winding of multiphase angular brushless exciting system Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/72—Testing of electric windings
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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Abstract
The invention relates to a method and a device for detecting a short-circuit fault of an exciting winding of a multiphase angular brushless exciting system, wherein the method for detecting the short-circuit fault of the exciting winding comprises the following steps: sampling exciting current in a stator exciting winding; carrying out Fourier analysis on the sampling current, and extracting m/P times subharmonic current and even subharmonic current; and determining whether a short circuit fault occurs to the exciting winding according to the m/P multiple subharmonic current and the even harmonic current. By implementing the technical scheme of the invention, the characteristic of the inter-turn short circuit fault of the exciting winding can be effectively extracted without modifying the motor, and further, the inter-turn short circuit fault of the exciting winding of the multiphase angular brushless exciter can be effectively monitored and protected on line.
Description
Technical Field
The invention relates to the field of relay protection of main equipment of an electric power system, in particular to a method and a device for detecting short-circuit faults of an excitation winding of a multiphase angular brushless excitation system.
Background
The excitation system is an important component of a large-sized generator, and the excitation system with excellent performance and high reliability is a foundation for ensuring the safety of the generator and the stable operation of the power system. The brushless excitation mode cancels the carbon brush and the slip ring of the generator, reduces the maintenance workload of an excitation system, obviously improves the reliability of the excitation system, is the first-choice excitation mode of a large-scale nuclear power generator set, but due to the addition of an exciter and a rotating rectifying link, the excitation system faults often occur in practice. The slight fault does not have serious influence on the excitation system, but the long-term fault operation can bring serious potential safety hazard to the unit, thereby influencing the reliability of the whole power generation system.
The current brushless exciter operated on site is only provided with stator overcurrent protection, but is not provided with special protection for stator exciting winding short circuit. For the turn-to-turn short circuit fault of the exciting winding of the synchronous generator, expert scholars at home and abroad propose various fault detection methods, namely, the fault detection and protection are carried out by utilizing the electric quantity such as stator parallel branch circulation, detection coil voltage, shaft voltage, reactive power deviation, exciting current harmonic wave and the like or the mechanical quantity such as mechanical vibration in the operation of the generator. The monitoring methods all need to modify the motor structure, have defects in real-time performance and reliability, and increase the process difficulty and cost.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method and a device for detecting the short-circuit fault of the exciting winding of the multiphase angular brushless exciting system, aiming at the defects of insufficient real-time performance and reliability of detecting the short-circuit fault of the exciting winding in the prior art.
The technical scheme adopted for solving the technical problems is as follows: a method for detecting short-circuit faults of exciting windings of a multiphase angular brushless exciting system is constructed, and comprises the following steps:
sampling: sampling exciting current in a stator exciting winding;
the analysis step: carrying out Fourier analysis on the sampling current, and extracting m/P times subharmonic current and even subharmonic current, wherein m is the phase number of the brushless excitation system, and P is the pole pair number of the brushless excitation system;
determining: and determining whether a short circuit fault occurs to the exciting winding according to the m/P multiple subharmonic current and the even harmonic current.
Preferably, the determining step includes:
and determining whether the exciting winding has short circuit fault according to the m/P harmonic current and/or the 2m/P harmonic current and the 2 nd harmonic current and/or the 4 th harmonic current.
Preferably, the determining step includes:
respectively calculating the effective value of the m/P subharmonic current and the effective value of the 2m/P subharmonic current;
respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current;
calculating a total effective value of the m/P subharmonic current and the 2m/P subharmonic current;
and determining whether a short circuit fault occurs in the exciting winding according to the effective value of the m/P harmonic current, the effective value of the 2 harmonic current, the effective value of the 4 harmonic current and the total effective value.
Preferably, the method comprises the steps of,
the analyzing step further comprises: extracting a direct current component;
the determining step includes: and determining whether the exciting winding has short circuit fault according to the m/P harmonic current, the 2 harmonic current, the 4 harmonic current and the direct current component.
Preferably, the determining step includes:
respectively calculating the effective value of the m/P harmonic current and the effective value of the 2m/P harmonic current, and judging whether the effective value of the m/P harmonic current is more than 2 times of the effective value of the 2m/P harmonic current;
respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current, and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not;
calculating a fault characteristic value according to the following formula, and judging whether the fault characteristic value is larger than a second threshold value or not;
wherein z is a fault characteristic value, i m/P Is m/P subharmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
if the following conditions are satisfied at the same time: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and if the fault characteristic value is larger than the second threshold value, determining that the exciting winding has short-circuit fault.
The invention also constructs an excitation winding short-circuit fault detection device of the multiphase angular brushless excitation system, which comprises:
the sampling module is used for sampling exciting current in the stator exciting winding;
the analysis module is used for carrying out Fourier analysis on the sampling current and extracting m/P multiple harmonic current and even harmonic current, wherein m is the phase number of the brushless excitation system, and P is the pole pair number of the brushless excitation system;
and the determining module is used for determining whether the exciting winding has short circuit faults or not according to the m/P multiple harmonic current and the even harmonic current.
Preferably, the determining module is configured to determine whether the exciting winding has a short circuit fault according to the m/P harmonic current and/or the 2m/P harmonic current, and the 2 nd harmonic current and/or the 4 th harmonic current.
Preferably, the determining module includes:
a first calculation unit for calculating the effective value of the m/P harmonic current and the effective value of the 2m/P harmonic current respectively;
a second calculation unit for calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current respectively;
a third calculation unit for calculating a total effective value of the m/P harmonic current and the 2m/P harmonic current;
and the first determining unit is used for determining whether the exciting winding has a short circuit fault according to the effective value of the m/P harmonic current, the effective value of the 2 harmonic current, the effective value of the 4 harmonic current and the total effective value.
Preferably, the method comprises the steps of,
the analysis module is also used for extracting direct current components;
the determining module is used for determining whether the exciting winding has short circuit fault or not according to the m/P harmonic current, the 2 harmonic current, the 4 harmonic current and the direct current component.
Preferably, the determining module includes:
a first judging unit, configured to calculate an effective value of the m/P harmonic current and an effective value of the 2m/P harmonic current, respectively, and judge whether the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current;
the second judging unit is used for respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not;
a third judging unit for calculating a fault characteristic value according to the following formula and judging whether the fault characteristic value is greater than a second threshold value;
wherein z is a fault characteristic value, i m/P Is m/P harmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
a second determination unit configured to, when the following conditions are simultaneously satisfied: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and the fault characteristic value is larger than a second threshold value, and the short-circuit fault of the exciting winding is determined.
According to the technical scheme provided by the invention, only the exciting current entering the exciting winding is acquired from the exciting end, then Fourier analysis is carried out on the exciting current, m/P multiple harmonic current and even harmonic current are extracted, and whether the short circuit fault of the exciting winding occurs or not can be judged together according to the m/P multiple harmonic current and the even harmonic current, so that the effective extraction of the characteristic of the short circuit fault between the exciting winding can be realized under the condition that a motor is not required to be modified, and the effective on-line monitoring and protection of the short circuit fault between the exciting winding of the multiphase angular brushless exciter can be further carried out.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the drawings that are required for the description of the embodiments will be briefly described below, it being apparent that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art. In the accompanying drawings:
FIG. 1 is a magnetomotive force spatial distribution diagram of a normal field winding when a forward current is applied;
FIG. 2 is a spatial distribution diagram of fault excitation magnetomotive force;
FIG. 3 is a magnetomotive force spatial distribution plot of a shorted turn winding with reverse current;
FIG. 4 is a flow chart of a first embodiment of a method for detecting a short circuit fault of an excitation winding of the multiphase angular brushless excitation system of the present invention;
FIG. 5A is a waveform of exciting current of the 5-pole 11-phase angle brushless exciter under normal working conditions;
FIG. 5B is a steady-state waveform of the exciting current of the 5-pole 11-phase angle brushless exciter after an exciting winding short-circuit fault occurs;
FIG. 6A is a waveform of the exciting current of the 11 pole 39 phase angle brushless exciter under normal operation;
FIG. 6B is a steady-state waveform of the exciting current of the 11-pole 39 phase angle brushless exciter after an exciting winding short-circuit fault occurs;
fig. 7 is a logic structure diagram of an embodiment of a field winding short-circuit fault detection device of the multiphase angular brushless excitation system of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a method for detecting short-circuit faults of an excitation winding of a multiphase angular brushless excitation system based on excitation current harmonic characteristics, which firstly explains the technical principle of the technical scheme:
the multiphase brushless exciter is a salient pole synchronous motor, the exciting windings are of a centralized structure, exciting magnetomotive forces are distributed identically under each level under normal operation conditions, and are distributed as rectangular waves in space only under adjacent poles due to opposite winding directions, as shown in fig. 1, so that the multiphase brushless exciter can be obtained:
wherein f fd For distributed magnetomotive force under normal operating conditions of the field winding, α is the coordinate system established on the stator, N fd I 'being the number of turns of the excitation winding' fd Is the forward current of the exciting winding when the exciter operates normally.
Fourier analysis of equation 1 yields:
wherein:
p is the pole pair number.
As can be seen from the formula 2, the exciting magnetomotive force contains only the fundamental wave and odd-order harmonic components such as 3 and 5 times, and does not contain the fractional harmonic components, and the calculation results are shown in table 1:
TABLE 1
After the excitation winding has turn-to-turn short circuit fault, the distribution of the excitation magnetomotive force is not the same under each pole, and the excitation magnetomotive force when the excitation winding has fault is regarded as the synthesis of the magnetomotive force when the normal excitation winding is connected with forward current and the short circuit turn winding is connected with reverse current, namely f' fd ＝f fd +Δf fd . Wherein f f ′ d Represents magnetomotive force generated by the failed field winding, f as shown in FIG. 2 fd Magnetomotive force indicating normal excitation winding forward current, Δf as shown in FIG. 1 fd Representing the magnetomotive force of the shorted turn winding passing a reverse current, as shown in fig. 3. Thereby, can obtain:
wherein DeltaN fd The number of turns of the shorted winding is excited.
Fourier analysis of equation 3 yields Δf fd Contains odd-order and fractional harmonic components, the results are shown in table 2:
TABLE 2
From the above analysis, it is found that when an inter-turn fault occurs in the exciting winding, the fault exciting magnetomotive force contains not only odd harmonic components such as fundamental waves 3 and 5, but also fractional harmonic components related to the pole pair number, and no even harmonic component.
The salient pole synchronous motor has symmetrical magnetic poles and uneven air gap, the variation period of the length of the air gap along the circumferential direction of the motor stator is pi, and the air gap permeability coefficient lambda can be expressed as:
wherein lambda is 0 2 is a constant term of the magnetic permeability coefficient, 2l is the harmonic order of the magnetic permeability coefficient, lambda 2l Is the magnitude of the 2l subharmonic flux guide.
The fault excitation magnetic field established by the fault excitation magnetomotive force in the air gap is:
wherein,the j'/P times excitation magnetomotive force harmonic amplitude is represented.
Equation 5 shows that the harmonic component in the fault excitation magnetic field is consistent with the component contained in the fault excitation magnetomotive force, that is, the excitation magnetic field also contains odd-order and fractional harmonic magnetic fields under the fault condition of the excitation winding, and no even-order harmonic magnetic field is contained.
The harmonic components of the fault excitation magnetic field generated by the fault excitation current have synchronous relative motion with the armature winding, the odd harmonic magnetic field induces odd harmonic current on the armature winding, and the fractional harmonic magnetic field induces fractional harmonic current on the armature winding.
The mu/P current harmonics on the column write k-phase armature winding are:
wherein, mu/P is the harmonic frequency of armature current, I μ/P Is the effective value of mu/P subharmonic current, m is the phase number,the electric angle value which is the phase difference of the armature windings of each phase of the m-phase brushless exciter is related to the placement position of the windings.
The v/P armature reaction magnetomotive force generated by the mu/P current harmonic on the k-phase winding is:
wherein,the v/P armature generated for the mu/P current harmonics reacts to magnetomotive force amplitude.
Wherein θ is re Coordinates are established on the rotor, and the formula 6 is brought into the formula 7, so that the following results:
the magnetic potential generated by each phase winding is pulse vibration magnetic potential and can be decomposed into positive and reverse magnetic potential:
synthesizing the armature reaction magnetomotive force of each phase to obtain the positive and negative rotation armature reaction synthesized magnetomotive force:
simplifying the process:
from equations 13 and 14, it can be seen that: when v=m+μ,non-zero, m+μ positive rotation components are present in the armature reaction. Similarly, when v=m- μ, then ++>Non-zero, only m-mu reversal components are present in the armature reaction.
Armature reaction Synthesis magnetomotive force the armature reaction Synthesis magnetomotive force (exemplified by the forward component) is established across the air gap, wherein θ se Built on the stator coordinate system and hasθ re ＝θ se +ωt。
The above analysis shows that: when the positive rotation component of the armature reaction resultant magnetic field is odd number times or fraction times, the induction electromotive force of (mu-v)/P times is generated on the short-circuit turn winding, namely, the (mu-v)/P times harmonic current exists in the stator exciting current. Similarly, the armature reaction synthesized magnetic field reversal component generates (mu+v)/P-time induced electromotive force on the shorted turn winding, namely (mu+v)/P-time harmonic current exists in the stator exciting current. It is also known that the forward rotation component satisfies μ - ν=m, the reverse rotation component satisfies μ+ν=m, and that m/P multiple harmonics such as m/P and 2m/P exist in the excitation current, and even-numbered harmonics are not included.
Therefore, the m/P multiple harmonic current and the even harmonic current in the stator exciting current can be utilized for fault protection design.
Based on this, as shown in fig. 1, the present invention constructs a field winding short-circuit fault detection method of a multiphase angular brushless excitation system, the field winding short-circuit fault detection method of this embodiment includes the steps of:
sampling step S10: sampling exciting current in a stator exciting winding;
analysis step S20: carrying out Fourier analysis on the sampling current, and extracting m/P times subharmonic current and even subharmonic current, wherein m is the phase number of the brushless excitation system, and P is the pole pair number of the brushless excitation system;
determination step S30: and determining whether a short circuit fault occurs to the exciting winding according to the m/P multiple subharmonic current and the even harmonic current.
In this embodiment, since the m/P times harmonic component in the stator field current is approximately zero when the exciter is in normal operation; when the exciting winding of the exciter is in turn-to-turn short circuit, the stator exciting current contains larger m/P times harmonic components and does not contain even times harmonic components, so that the exciting current entering the exciting winding is collected from an exciting end, fourier analysis is carried out on the exciting current, m/P times harmonic current and even times harmonic current are extracted, whether the exciting winding short circuit fault occurs or not can be judged according to the m/P times harmonic current and the even times harmonic current, namely, whether the exciting winding short circuit fault occurs or not can be judged based on the unique characteristics of the multiphase angular brushless exciter magnetic winding turn-to-turn short circuit fault, the fault judging method is simple and effective, the generating safety of the machine set is ensured, and the running reliability of the machine set is improved. And the characteristic of the inter-turn short circuit of the exciting winding can be effectively extracted under the condition that a motor is not required to be modified, so that the inter-turn short circuit of the exciting winding of the multiphase angular brushless exciter is effectively monitored and protected on line.
Further, in an alternative embodiment, the determining step S30 includes: and determining whether the exciting winding has short circuit fault according to the m/P harmonic current and/or the 2m/P harmonic current and the 2 nd harmonic current and/or the 4 th harmonic current.
Taking a Taizhou 5-pole 11-phase angle brushless excitation system and a Honghe 11-pole 39-phase angle brushless excitation system as examples, calculating an excitation winding short-circuit fault which suddenly happens when the brushless excitation system normally operates by using an excitation winding short-circuit fault analysis technology based on a multi-loop model, wherein fig. 5A is an excitation current waveform diagram of the 5-pole 11-phase angle brushless exciter under a normal working condition, and fig. 5B is an excitation current steady-state waveform diagram of the 5-pole 11-phase angle brushless exciter after the excitation winding short-circuit fault happens. Fourier analysis was performed on stator excitation current steady state current before and after failure, and the results are shown in table 3:
| steady state operation before failure (A) | Steady state operation after failure (A) | |
| Direct flow rate | 138 | 154 |
| 1/5 th order harmonic | 2.74×10 -2 | 1.71×10 -2 |
| 2/5 th order harmonic | 1.90×10 -2 | 0.19×10 -2 |
| 3/5 th order harmonic | 0.80×10 -2 | 0.45×10 -2 |
| 4/5 th order harmonic | 0.84×10 -2 | 1.82×10 -2 |
| … | … | … |
| 10/5 th order harmonic | 0.18×10 -2 | 0.05×10 -2 |
| 11/5 th order harmonic | 0.45×10 -2 | 1.60 |
| 12/5 th order harmonic | 0.30×10 -2 | 1.79×10 -2 |
| 22/5 th order harmonic | 0.11×10 -2 | 0.71 |
TABLE 3 Table 3
Similarly, fig. 6A is a waveform diagram of exciting current of the 11-pole 39-phase angle brushless exciter under normal working conditions, fig. 6B is a waveform diagram of steady state exciting current of the 11-pole 39-phase angle brushless exciter after an exciting winding short-circuit fault occurs, and fourier analysis is performed on steady state stator exciting current before and after the fault, and the result is shown in table 4:
TABLE 4 Table 4
As can be seen from tables 3 and 4, the brushless excitation system contains larger m/P times and 2m/P harmonic components in the stator excitation current after the short-circuit fault of the excitation winding occurs, and these harmonics are caused by the short-circuit fault of the excitation winding. When the exciter is in normal operation, the m/P subharmonic current i m/P 2m/P subharmonic current i 2m/P Are all approximately zero, and when the exciter has a turn-to-turn short circuit of the exciting winding, the current i m/P And i 2m/P The increase is very large.
Further, in an alternative embodiment, the determining step S30 includes:
respectively calculating the effective value of the m/P subharmonic current and the effective value of the 2m/P subharmonic current;
respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current;
calculating a total effective value of the m/P subharmonic current and the 2m/P subharmonic current;
and determining whether a short circuit fault occurs in the exciting winding according to the effective value of the m/P harmonic current, the effective value of the 2 harmonic current, the effective value of the 4 harmonic current and the total effective value.
In the embodiment, the respective effective values of the m/P harmonic current, the 2 harmonic current and the 4 harmonic current and the total effective values of the m/P harmonic current and the 2m/P harmonic current are taken as the basis of fault judgment, so that the interference influence of other abnormal working conditions can be prevented, and the accuracy of fault detection is improved.
Further, in an alternative embodiment, the analyzing step S20 further includes: extracting a direct current component; further, the determining step S30 includes: and determining whether the exciting winding has short circuit fault according to the m/P harmonic current, the 2 harmonic current and the 4 harmonic current and the direct current component.
Specifically, the determining step S30 includes:
respectively calculating the effective value of the m/P harmonic current and the effective value of the 2m/P harmonic current, and judging whether the effective value of the m/P harmonic current is more than 2 times of the effective value of the 2m/P harmonic current;
respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current, and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not;
calculating a fault characteristic value according to the following formula, judging whether the fault characteristic value is larger than a second threshold value, and regarding the second threshold value, it is to be noted that the fault characteristic value can reliably avoid exciting currents under various working conditions in normal operation;
wherein z is a fault characteristic value, i m/P Is m/P subharmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
if the following conditions are satisfied at the same time: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and if the fault characteristic value is larger than the second threshold value, determining that the exciting winding has short-circuit fault.
In this embodiment, since the effective value of the characteristic quantity due to the same fault is changed with the change of the excitation level, this embodiment adopts the direct current component of the excitation current as the braking quantity, and compares the values of the root mean square ratio excitation current direct current components of the stator excitation current m/P and the 2m/P subharmonic components with the preset threshold fixed value, thereby realizing the effective judgment of the fault and effectively playing the role of preventing misoperation.
Fig. 7 is a logic structure diagram of a first embodiment of an excitation winding short-circuit fault detection device of the multiphase angular brushless excitation system according to the present invention, where the excitation winding short-circuit fault detection device of the embodiment includes a sampling module 10, an analysis module 20, and a determination module 30, where the sampling module 10 is configured to sample an excitation current in a stator excitation winding; the analysis module 20 is configured to perform fourier analysis on the sampled current, and extract m/P multiple harmonic current and even harmonic current therein, where m is the number of phases of the brushless excitation system, and P is the pole pair number of the brushless excitation system; the determining module 30 is configured to determine whether the exciting winding has a short-circuit fault according to the m/P multiple harmonic current and the even harmonic current.
Further, in an alternative embodiment, the determining module 30 is configured to determine whether the excitation winding has a short circuit fault according to the m/P harmonic current and/or the 2m/P harmonic current, and the 2 nd harmonic current and/or the 4 th harmonic current.
Further, in an alternative embodiment, the determining module 30 includes a first calculating unit, a second calculating unit, a third calculating unit, and a first determining unit, where the first calculating unit is configured to calculate an effective value of the m/P harmonic current and an effective value of the 2m/P harmonic current, respectively; the second calculation unit is used for calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current respectively; the third calculation unit is used for calculating the total effective value of the m/P harmonic current and the 2m/P harmonic current; the first determining unit is used for determining whether a short circuit fault occurs to the exciting winding according to the effective value of the m/P harmonic current, the effective value of the 2 harmonic current, the effective value of the 4 harmonic current and the total effective value.
Further, in an alternative embodiment, the analysis module 20 is further configured to extract a dc component thereof; the determining module 30 is configured to determine whether the exciting winding has a short-circuit fault according to the m/P harmonic current, the 2 nd harmonic current, the 4 th harmonic current and the dc component.
Further, in an alternative embodiment, the determining module 30 includes a first determining unit, a second determining unit, a third determining unit, and a second determining unit, where the first determining unit is configured to calculate an effective value of the m/P harmonic current and an effective value of the 2m/P harmonic current, respectively, and determine whether the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the second judging unit is used for respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not; the third judging unit is used for calculating a fault characteristic value according to the following formula and judging whether the fault characteristic value is larger than a second threshold value or not:
wherein z is a fault characteristic value, i m/P Is m/P harmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
the second determination unit is configured to, when the following conditions are simultaneously satisfied: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and the fault characteristic value is larger than a second threshold value, and the short-circuit fault of the exciting winding is determined.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any such modifications, equivalents, and improvements that fall within the spirit and principles of the present invention are intended to be covered by the following claims.
Claims (2)
1. A method for detecting short-circuit faults of exciting windings of a multiphase angular brushless exciting system is characterized by comprising the following steps:
sampling: sampling exciting current in a stator exciting winding;
the analysis step: carrying out Fourier analysis on the sampling current, and extracting m/P times subharmonic current and even subharmonic current, wherein m is the phase number of the brushless excitation system, and P is the pole pair number of the brushless excitation system;
determining: determining whether a short circuit fault occurs in the exciting winding according to the m/P multiple subharmonic current and the even harmonic current;
the analyzing step further comprises: extracting a direct current component;
the determining step includes: determining whether a short circuit fault occurs in the exciting winding according to the m/P harmonic current, the 2 harmonic current, the 4 harmonic current and the direct current component;
respectively calculating the effective value of the m/P harmonic current and the effective value of the 2m/P harmonic current, and judging whether the effective value of the m/P harmonic current is more than 2 times of the effective value of the 2m/P harmonic current;
respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current, and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not;
calculating a fault characteristic value according to the following formula, and judging whether the fault characteristic value is larger than a second threshold value or not;
Z=/I f ；
wherein z is a fault characteristic value, i m/P Is m/P subharmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
if the following conditions are satisfied at the same time: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and if the fault characteristic value is larger than the second threshold value, determining that the exciting winding has short-circuit fault.
2. An excitation winding short-circuit fault detection device of a multiphase angular brushless excitation system is characterized by comprising:
the sampling module is used for sampling exciting current in the stator exciting winding;
the analysis module is used for carrying out Fourier analysis on the sampling current and extracting m/P multiple harmonic current and even harmonic current in the sampling current, wherein m is the phase number of the brushless excitation system, and P is the pole pair number of the brushless excitation system;
the determining module is used for determining whether the exciting winding has short circuit faults or not according to the m/P multiple harmonic current and the even harmonic current;
the analysis module is also used for extracting direct current components;
the determining module is used for determining whether the exciting winding has short circuit fault or not according to the m/P harmonic current, the 2 harmonic current, the 4 harmonic current and the direct current component;
the determining module includes:
a first judging unit, configured to calculate an effective value of the m/P harmonic current and an effective value of the 2m/P harmonic current, respectively, and judge whether the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current;
the second judging unit is used for respectively calculating the effective value of the 2 nd harmonic current and the effective value of the 4 th harmonic current and judging whether the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value or not;
a third judging unit for calculating a fault characteristic value according to the following formula and judging whether the fault characteristic value is greater than a second threshold value;
Z=/I f ；
wherein z is a fault characteristic value, i m/P Is m/P subharmonic current, i 2m/P Is 2m/P subharmonic current, I f Is a direct current component;
a second determination unit configured to, when the following conditions are simultaneously satisfied: the effective value of the m/P harmonic current is greater than 2 times the effective value of the 2m/P harmonic current; the effective value of the 2 nd harmonic current and the 4 th harmonic current are smaller than a first threshold value; and the fault characteristic value is larger than a second threshold value, and the short-circuit fault of the exciting winding is determined.
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| CN116298872A (en) * | 2023-03-21 | 2023-06-23 | 吉林化工学院 | Stator parallel branch loop harmonic component detection method based on harmonic analysis |
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