FIELD OF THE INVENTION

The present invention relates to a node energy-based diagnosis method for fault of switched reluctance motor double-switch power converter, which is especially applicable to switched reluctance motor power converters with various phase numbers and double-switch structure.

BACKGROUND OF THE INVENTION

Accurate diagnosis for fault of switched reluctance motor power converter, on one hand, is depending on the information source of the fault, i.e., obtaining rich, authentic, and accurate fault information and symptoms is a prerequisite for the fault diagnosis; on the other hand, is depending on the fault diagnosing method. Therefore, to carry out fault diagnosis, not only rich, valid, and accurate fault information and data must be acquired, but also an advanced and efficient fault diagnosing method based on the limited fault data must be used, so as to accurately judge the fault type and accomplish fault diagnosis. Among existing fault diagnosing methods for the main circuit of switched reluctance motor switch converter, some utilize two fault characteristic quantities to identify a fault; while others utilize analog to digital conversion to extract fault characteristic quantities; all these methods have high requirements for hardware performance. An appropriate diagnosing method for fault of switched reluctance motor power converter, which is highly fault-targeted, can realize reliable and accurate fault diagnosis, and is highly practical, is an important guarantee for implementing fault-tolerant control of a switched reluctance motor system and for improving operating reliability of the switched reluctance motor system.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a diagnosing method for fault of switched reluctance motor double-switch power converter, which is based on analysis of the dispersion of wavelet packet node energy.

The object of the present invention is attained through the follows: detecting the transient value of phase current i(t) of switched reluctance motor double-switch power converter; calculating the standard deviation Ïƒ of node energy

with formula

$Ïƒ = {{âˆ‘}_{n = 1}^{8} î¢ž î¢ž {[E î¢ (5, j) - s]}^{2} / 8}^{1 / 2},$

wherein, the mean value of node
energy is

$s = {âˆ‘}_{j = 1}^{8} î¢ž E î¢ (5, j) / 8,$

the node energy is

$E î¢ (5, j) = âˆ« ï˜ƒ S î¢ (5, j) î¢ž (t) ï˜„ î¢ž ï Œ t = {âˆ‘}_{k = 1}^{n} î¢ž î¢ž {ï˜ƒ d_{5}^{j, n} ï˜„}^{2},$

(j=0,1,2,3,4,5,6,7,8), the number of nodes is j, wherein S(5,j) represents the node j in layer 5, and d₅^j,n(j=0,1,2,3,4,5,6,7,8, n=1,2,3, . . . ,) represents the wavelet packet coefficients of S(5,j);

taking the standard deviation Ïƒ of node energy as a fault characteristic quantity, and diagnosing whether there is any fault in the main circuit of switched reluctance motor double-switch power converter;

if the standard deviation Ïƒ of node energy in the entire range of rotation speed is greater than 29.0, then there is a main switch lower tube short circuit fault in switched reluctance motor double-switch power converter;

If the standard deviation Ïƒ of node energy in the entire range of rotation speed is not greater than 29.0, then there is no main switch lower tube short circuit fault in switched reluctance motor double-switch power converter.

Beneficial effects: with the technical scheme described above, the transient value of phase current of switched reluctance motor double-switch power converter is detected, the standard deviation Ïƒ of node energy is calculated and taken as a fault characteristic quantity, and whether there is a main switch lower tube short circuit fault in switched reluctance motor double-switch power converter is diagnosed with a curve of standard deviation Ïƒ of phase current node energy in switched reluctance motor double-switch power converter in the entire range of rotation speed, and thereby the object of the present invention is attained. The diagnosis method for fault of switched reluctance motor power converter is applicable to switched reluctance motor power converter with various phase numbers and a double-switch structure, and is highly fault-targeted, can realize reliable and accurate fault diagnosis, is highly practical, and has high practicability and wide application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of the three-phase double-switch type switched reluctance motor power converter for which the present invention is applied;

FIG. 2 is a curve diagram of standard deviation Ïƒ of phase current node energy in the three-phase double-switch type switched reluctance motor power converter for which the present invention is applied;

FIG. 3 is a diagram of phase current waveform of the three-phase double-switch switched reluctance motor power converter with main switch lower tube short circuit fault;

FIG. 4 is a diagram of phase current waveform of the three-phase double-switch switched reluctance motor power converter without fault.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereunder the present invention will be further detailed in an embodiment, with reference to the accompanying drawings:

As shown in FIG. 1, in the main circuit of the three-phase double-switch switched reluctance motor power converter, each phase has two main switches and two freewheel diodes; for example, in phase A, one end of an upper main switch S1 is connected to the positive electrode of the power supply Us, the other end of the upper main switch S1 is connected to one end of the winding of phase A, one end of the lower main switch S2 is connected to the negative electrode of the power supply Us, the other end of the lower main switch S2 is connected to the other end of the winding of phase A, one end of the upper freewheel diode VD1 is connected to the positive electrode of the power supply Us, the other end of the upper freewheel diode VD1 is connected to the other end of the winding of phase A, one end of the lower freewheel diode VD2 is connected to the negative electrode of the power supply Us, and the other end of the lower freewheel diode VD2 is connected to one end of the winding of phase A. The internal connections in phase B and phase C are similar to those in phase A. The phase A, B, and C are connected in parallel with the power supply Us.

First, the transient value of phase current i_Aof phase A of three-phase double-switch switched reluctance motor power converter is detected; then, the standard deviation Ïƒ_Aof node energy is calculated with formula

${Ïƒ}_{A} = {{âˆ‘}_{n = 1}^{8} î¢ž î¢ž {[E î¢ (5, j) - s]}^{2} / 8}^{1 / 2},$

wherein, the mean value of node energy is

$s = {âˆ‘}_{j = 1}^{8} î¢ž î¢ž E î¢ (5, j) / 8,$

the node energy is

$E î¢ (5, j) = âˆ« ï˜ƒ S î¢ž (5, j) î¢ž (t) ï˜„ î¢ž ï Œ t = {âˆ‘}_{k = 1}^{n} î¢ž î¢ž {ï˜ƒ d_{5}^{j, n} ï˜„}^{2},$

(j=0,1,2,3,4,5,6,7,8), the number of nodes is j, wherein S(5,j) represents the node j in layer 5, and d₅^j,n(j=0,1,2,3,4,5,6,7,8,n=1,2,3, . . . ,) represents the wavelet packet coefficients of S(5,j) of phase current i_Aof phase A;
the standard deviation Ïƒ_Aof node energy is taken as a fault characteristic quantity, and whether there is any fault in the main circuit of power converter is diagnosed;

As shown in FIG. 2, if the standard deviation Ïƒ_Aof node energy in the entire range of rotation speed is greater than 29.0, then there is main switch lower tube S2 short circuit fault in phase A of switched reluctance motor double-switch power converter; the phase current waveform is shown in FIG. 3;

As shown in FIG. 2, if the standard deviation Ïƒ_Aof node energy in the entire range of rotation speed is not greater than 29.0, then there is no main switch lower tube S2 short circuit fault in phase A of switched reluctance motor double-switch power converter; the phase current waveform is shown in FIG. 4;

As for detecting phase B of switched reluctance motor double-switch power converter for main switch lower tube S4 short circuit fault, the fault detection, fault type identification, and fault phase locating method thereof are similar to that for phase A of switched reluctance motor double-switch power converter;

As shown in FIG. 1, detecting the transient value of current i_Bof phase B of the three-phase double-switch switched reluctance motor power converter; calculating the standard deviation Ïƒ_Bof node energy with formula

${Ïƒ}_{B} = {{âˆ‘}_{n = 1}^{8} î¢ž î¢ž {[E î¢ (5, j) - s]}^{2} / 8}^{1 / 2};$

if the standard deviation Ïƒ_Bof node energy in the entire range of rotation speed is greater than 29.0, then there is main switch lower tube S4 short circuit fault in phase B of switched reluctance motor double-switch power converter; if the standard deviation Ïƒ_Bof node energy in the entire range of rotation speed is not greater than 29.0, then there is no main switch lower tube S4 short circuit fault in phase B of switched reluctance motor double-switch power converter.

As for detecting phase C of switched reluctance motor double-switch power converter is detected for main switch lower tube S6 short circuit fault, the fault detection, fault type identification, and fault phase locating method thereof are similar to that for phase A of switched reluctance motor double-switch power converter;

As shown in FIG. 1, detecting the transient value of current i_Cof phase C of three-phase double-switch switched reluctance motor power converter; calculating the standard deviation Ïƒ_Cof node energy with formula

${Ïƒ}_{C} = {{âˆ‘}_{n = 1}^{8} î¢ž î¢ž {[E î¢ (5, j) - s]}^{2} / 8}^{1 / 2};$

if the standard deviation Ïƒ_Cof node energy in the entire range of rotation speed is greater than 29.0, then there is main switch lower tube S6 short circuit fault in phase C of switched reluctance motor double-switch power converter; if the standard deviation Ïƒ_Cof node energy in the entire range of rotation speed is not greater than 29.0, then there is no main switch lower tube S6 short circuit fault in phase C of switched reluctance motor double-switch power converter.

As for detecting the switched reluctance motor power converter for lower tube short circuit fault in two or more phases, the fault detection, fault type identification, and fault locating method thereof are similar to the method described above;

The fault phases can be located by detecting the phase current of phase A, B, and C and judging whether the standard deviation Ïƒ_A, Ïƒ_B, and Ïƒ_Cof node energy are greater than 29.0 or not, respectively.

Detecting the transient values of phase current i_A, i_B, and i_Cof phases A, B, and C of the three-phase double-switch switched reluctance motor power converter respectively, and calculating the standard deviations Ïƒ_A, Ïƒ_B, and Ïƒ_Cof phase current node energy of phases A, B, and C respectively; if all the standard deviations Ïƒ_A, Ïƒ_B, and Ïƒ_Cof phase current node energy of phases A, B, and C are not greater than 29.0 in the entire range of rotation speed, then there is no main switch lower tubes S2, S4, or S6 short circuit faults in double-switch switched reluctance motor power converter; if the standard deviation Ïƒ_Aof phase current node energy of phase A, the standard deviation Ïƒ_Bof phase current node energy of phase B, and the standard deviation Ïƒ_Cof phase current node energy of phase C in the entire range of rotation speed are all greater than 29.0, then there are main switches lower tubes S2, S4, and S6 short circuit faults in the switched reluctance motor double-switch power converter; if the standard deviation Ïƒ_Aof phase current node energy of phase A and the standard deviation Ïƒ_Bof phase current node energy of phase B are greater than 29.0 in the entire range of rotation speed, then there are main switches lower tubes S2 and S4 short circuit faults in the switched reluctance motor double-switch power converter; if the standard deviation Ïƒ_Aof phase current node energy of phase A and the standard deviation Ïƒ_Cof phase current node energy of phase C in the entire range of rotation speed are greater than 29.0, then there are main switches lower tubes S2 and S6 short circuit faults in the switched reluctance motor double-switch power converter; if the standard deviation Ïƒ_Bof phase current node energy of phase B and the standard deviation Ïƒ_Cof phase current node energy of phase C are greater than 29.0 in the entire range of rotation speed, then there are main switches lower tubes S4 and S6 short circuit faults in the switched reluctance motor double-switch power converter.