CN114545133A - Fault diagnosis method of single-phase cascade H-bridge rectifier based on current detection - Google Patents

Fault diagnosis method of single-phase cascade H-bridge rectifier based on current detection Download PDF

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CN114545133A
CN114545133A CN202210189788.XA CN202210189788A CN114545133A CN 114545133 A CN114545133 A CN 114545133A CN 202210189788 A CN202210189788 A CN 202210189788A CN 114545133 A CN114545133 A CN 114545133A
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bridge rectifier
bridge
phase
ith
fault diagnosis
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CN114545133B (en
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谢锡锋
邓宇豪
杨帆
凌春香
王江伟
邓海鹰
左江林
罗宇强
谭社平
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Guangxi College of Water Resources and Electric Power
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01R31/26—Testing of individual semiconductor devices
    • G01R31/2601—Apparatus or methods therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01R31/327—Testing of circuit interrupters, switches or circuit-breakers

Abstract

The invention belongs to the technical field of power electronics, and particularly relates to a fault diagnosis method of a single-phase cascaded H-bridge rectifier based on current detection, which is used for realizing a fault diagnosis end of the single-phase cascaded H-bridge rectifier. The method comprises the steps of establishing a switching function according to the current direction in a bridge arm and a control signal of a switching tube, deducing a current calculation model of the single-phase cascade H-bridge rectifier, obtaining a difference value between calculated current and measured current under a fault state according to the current calculation model, establishing a fault diagnosis function of each switching tube, and determining the damaged switching tube by using the established fault diagnosis function. The invention can monitor whether the switch tube has a fault in real time under the condition of rectifier operation; the switching tube can be positioned to a fault when the fault occurs; the calculation method is simple, and has high efficiency and reliability; the realization difficulty is low, and extra hardware is not required to be added.

Description

Fault diagnosis method of single-phase cascade H-bridge rectifier based on current detection
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection.
Background
The traditional power frequency transformer has the defects of large volume, low efficiency and the like, so that the speed and power of a train are seriously influenced. Power Electronic Transformers (PET) are becoming hot spots and trends for engineering applications due to their advantages such as high Power density and intelligent control. A Cascaded H-bridge rectifier (CHBR) is often used as a front-end rectifier module in a PET, and the normal operation of the CHBR is very important for the rear end part of the PET, and if the voltage on the dc side of the CHBR is unbalanced, the stable operation of the system is easily affected.
Taking the operation of the PET in the traction power supply system as an example, the operation environment of the PET is complex, the failure rate is high, the single-phase CHBR contains a large number of power switching devices, and the power switching devices are very easy to generate short-circuit failure and open-circuit failure, wherein the short-circuit failure can be rapidly diagnosed in a hardware mode in engineering application, so that the system can rapidly perform short-circuit protection after the short-circuit failure occurs. Open circuit failure of power switching devices in a single phase CHBR does not immediately protect the system, but it can subject other devices to over-voltage causing secondary damage to the system. At present, the open-circuit fault diagnosis method for the single-phase CHBR is less, the open-circuit fault condition in the CHBR is complex, and the damaged switching device is difficult to locate. Therefore, on the basis of adding few sensors, the fault diagnosis of the single-phase cascade H-bridge rectifier is realized by analyzing the fault characteristics of the switching devices.
Disclosure of Invention
In order to solve the problems, the invention provides a fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection, which can monitor whether a switching tube has a fault or not in real time under the condition of rectifier operation and can locate the faulty switching tube when the fault occurs. The control algorithm can carry out real-time fault diagnosis on the single-phase cascade H-bridge rectifier, the fault diagnosis method is simple in calculation, and has high efficiency and reliability, and the specific technical scheme is as follows:
a fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection comprises the following steps:
step S1, carrying out real-time fault monitoring on the single-phase cascaded H-bridge rectifier, and carrying out real-time sampling on the network side current of the single-phase cascaded H-bridge rectifier in a fixed sampling period to obtain a measured value of the network side current of the single-phase cascaded H-bridge rectifier; the single-phase cascade H-bridge rectifier comprises a plurality of H-bridges; the ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein the left bridge arm is defined as an a bridge arm, and the right bridge arm is defined as a b bridge arm; wherein VTi1Is a switching tube above the bridge arm, VDi1A diode connected in reverse parallel thereto; VTi2Is a switch tube below the bridge arm, VDi2A diode connected in reverse parallel thereto; VTi3Is a switching tube above the b-bridge arm, VDi3A diode connected in reverse parallel thereto; wherein VTi4A switching tube below the b-bridge arm, VDi4A diode connected in reverse parallel thereto;
step S2, calculating the network side current of the single-phase cascade H-bridge rectifier under the condition of no fault to obtain a calculated value of the network side current of the single-phase cascade H-bridge rectifier;
step S3, subtracting the calculated value of the network side current of the single-phase cascaded H-bridge rectifier from the measured value of the network side current of the single-phase cascaded H-bridge rectifier to obtain the network side current error of the single-phase cascaded H-bridge rectifier;
step S4, establishing a fault diagnosis model of the single-phase cascaded H-bridge rectifier according to the network side current error of the single-phase cascaded H-bridge rectifier;
step S5, calculating the value of the single-phase cascade H-bridge rectifier fault diagnosis model, comparing the absolute value with the set threshold value th,
if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is smaller than or equal to the set threshold value, the single-phase cascaded H-bridge rectifier is not in fault, and the step S1 is returned; on the contrary, if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is larger than the set threshold, the single-phase cascaded H-bridge rectifier is represented to have a fault, and the step S6 is carried out;
step S6, establishing a fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier according to the fault diagnosis model of the single-phase cascaded H bridge rectifier, judging the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier, and representing that the ith H bridge of the single-phase cascaded H bridge rectifier has a class a fault if the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier is positive; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascaded H bridge rectifier has b-type faults; wherein, the a-type fault is the switching tube VT of the ith H-bridgei1Or switching tube VTi4Switching tube VT with i-th H-bridge as b-type faulti2Or switching tube VTi3A failure occurs;
and step S7, establishing a fault diagnosis function of the switch tube, detecting the corresponding switch tube according to the type of the fault, when the fault diagnosis function value of the corresponding switch tube is 0, representing that the switch tube is not in fault, and when the fault diagnosis function value of the corresponding switch tube is 1, representing that the switch tube is in fault, thus determining the switch tube in fault.
Preferably, the network-side current of the single-phase cascade H-bridge rectifier in step S2 is calculated as follows:
according to the single-phase cascaded H-bridge rectifier model, the network side voltage of the single-phase cascaded H-bridge rectifier is expressed as:
Figure BDA0003524123520000021
uaibi＝kiVdci；
wherein, UsThe voltage is the network side voltage of a single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i.e. iNThe current is the network side current of a single-phase cascade H-bridge rectifier; u. ofaibiThe output voltage of the ith H bridge of the single-phase cascade H bridge rectifier;
Vdcithe output voltage value of the ith H bridge of the single-phase cascade H bridge rectifier; k is a radical ofiAn ideal switching function for the ith H bridge of the single-phase cascade H bridge rectifier;
the network side current i of the single-phase cascaded H-bridge rectifier can be obtained through integrationNThe expression is as follows:
Figure BDA0003524123520000031
wherein E ismIs the amplitude of the AC power supply; omega is the angular frequency of the alternating current power supply.
Preferably, the ith H-bridge ideal switching function k of the single-phase cascaded H-bridge rectifieriThe calculation method of (c) is as follows: k is a radical ofi＝Hai-Hbi；
Wherein HaiA switching function of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier; hbiAnd the switching function is the switching function of the ith H-bridge b bridge arm of the single-phase cascade H-bridge rectifier.
Preferably, the switching function H of the ith H-bridge a-leg of the single-phase cascaded H-bridge rectifieraiThe method is established according to the conduction condition of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier, and comprises the following steps:
Figure BDA0003524123520000032
switching function H of ith H-bridge b bridge arm of single-phase cascade H-bridge rectifierbiThe method is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and comprises the following steps:
Figure BDA0003524123520000033
preferably, according to the conduction condition of the ith H-bridge of the single-phase cascade H-bridge rectifier, the logic expression of the switching function expressed by the conduction signal and the current flow direction of the switching tube is as follows:
Figure BDA0003524123520000034
wherein S isi1Is a switching tube VTi1Control signal of, control signal Si1Is 1 hour VTi1The switch tube is conducted to control the signal Si1Switching tube VT when 0i1Turning off;
Si2is a switching tube VTi2Control signal of, control signal Si2Is 1 hour VTi2The switch tube is conducted to control the signal Si2Switching tube VT when 0i2Turning off;
Figure BDA0003524123520000035
representing the control signal Si2Taking out of the solution;
Si3is a switching tube VTi3Control signal of, control signal Si3Is 1 hour VTi3The switch tube is conducted to control the signal Si3Switching tube VT when 0i3Turning off;
Si4is a switching tube VTi4Control signal of, control signal Si4Is 1 hour VTi4The switch tube is conducted to control the signal Si4Switching tube VT when 0i4Turning off;
Figure BDA0003524123520000041
representing the control signal Si4Taking out of the solution;
xi represents the measured value i of the network side current of the single-phase cascaded H-bridge rectifiersIs defined as follows:
Figure BDA0003524123520000042
wherein the content of the first and second substances,
Figure BDA0003524123520000043
indicating that ξ is negated.
Preferably, the calculated value of the grid-side current error of the single-phase cascaded H-bridge rectifier in step S3 is specifically:
according to the network side current i of the single-phase cascade H-bridge rectifier in the step S2NThe expression of (2) expresses the measured value of the network side current of the single-phase cascade H-bridge rectifier as follows:
Figure BDA0003524123520000044
wherein isThe current is measured value of the network side of the single-phase cascade H-bridge rectifier; k is a radical ofiThe switching function of the ith H bridge of the single-phase cascaded H bridge rectifier is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascaded H bridge rectifier;
the method for calculating the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
Figure BDA0003524123520000045
wherein the content of the first and second substances,
Figure BDA0003524123520000046
the single-phase cascade H-bridge rectifier network side current error is obtained;
preferably, the establishing of the fault diagnosis model of the single-phase cascaded H-bridge rectifier according to the network-side current error of the single-phase cascaded H-bridge rectifier specifically includes:
for single-phase cascade H bridge rectifier network side current error
Figure BDA0003524123520000047
Differentiating to obtain a single-phase cascade H-bridge rectifier fault diagnosis model according to current detection, which comprises the following specific steps:
Figure BDA0003524123520000048
preferably, the step S6 of establishing the fault diagnosis model of the ith H-bridge of the single-phase cascaded H-bridge rectifier according to the fault diagnosis model of the single-phase cascaded H-bridge rectifier specifically includes:
under the condition that a switching tube of the single-phase cascade H-bridge rectifier has no fault, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k of ith H-bridge of single-phase cascaded H-bridge rectifieriThe method is constant, and the fault diagnosis model of the single-phase cascade H-bridge rectifier is equal to 0;
under the condition that a switching tube of the single-phase cascade H-bridge rectifier fails, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k of ith H-bridge of single-phase cascaded H-bridge rectifieriIf the current values are not equal, the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is as follows:
Figure BDA0003524123520000051
and sequentially judging whether each H bridge has a fault according to the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier.
Preferably, the fault diagnosis function of the switching tube in step S7 is specifically:
Figure BDA0003524123520000052
Figure BDA0003524123520000053
Figure BDA0003524123520000054
Figure BDA0003524123520000055
the invention has the beneficial effects that: the invention can monitor whether the switch tube has a fault in real time under the condition of rectifier operation; the switching tube can be positioned to a fault when the fault occurs; the calculation method is simple, and has high efficiency and reliability; the realization difficulty is low, and extra hardware is not required to be added.
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In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a basic circuit topology diagram of a single-phase cascaded H-bridge rectifier according to the present invention;
FIG. 3 is a current-voltage relationship diagram of a single-phase cascaded H-bridge rectifier under normal operation;
FIG. 4 is a diagram of a critical waveform for fault diagnosis under a class a fault;
fig. 5 is a diagram of critical waveforms for fault diagnosis under a class b fault.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
As shown in fig. 1, the embodiment of the present invention provides a fault diagnosis method for a single-phase cascaded H-bridge rectifier based on current detection, including the following steps:
step S1, carrying out real-time fault monitoring on the single-phase cascaded H-bridge rectifier, and carrying out real-time sampling on the network side current of the single-phase cascaded H-bridge rectifier in a fixed sampling period to obtain a measured value of the network side current of the single-phase cascaded H-bridge rectifier; as shown in fig. 2, the single-phase cascaded H-bridge rectifier includes several H-bridges; the ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein the left bridge arm is defined as an a bridge arm, and the right bridge arm is defined as a b bridge arm; wherein VTi1Is a switching tube above the bridge arm, VDi1A diode connected in reverse parallel thereto; VTi2Is a switch tube below the bridge arm, VDi2A diode connected in reverse parallel thereto; VTi3Is a switching tube above the b-bridge arm, VDi3A diode connected in reverse parallel thereto; wherein VTi4Is a switch tube below the b bridge arm, VDi4A diode connected in reverse parallel thereto; wherein S isi1Is a switching tube VTi1Control signal of, control signal Si1Is 1 hour VTi1The switch tube is conducted to control the signal Si1Switching tube VT when 0i1Turning off; si2Is a switching tube VTi2Control signal of, control signal Si2Is 1 hour VTi2Switch with a switch bodyTube conduction, control signal Si2Switching tube VT when 0i2Turning off; si3Is a switching tube VTi3Control signal of, control signal Si3Is 1 hour VTi3The switch tube is conducted to control the signal Si3Switching tube VT when 0i3Turning off; si4Is a switching tube VTi4Control signal of, control signal Si4Is 1 hour VTi4The switch tube is conducted to control the signal Si4Switching tube VT when 0i4And (6) turning off.
And step S2, calculating the network side current of the single-phase cascaded H-bridge rectifier under the condition of no fault, and obtaining the calculated value of the network side current of the single-phase cascaded H-bridge rectifier. According to the topological model shown in the figure 1, an expression of the network side voltage of the single-phase cascaded H-bridge rectifier can be established, so that the network side resistance of the single-phase cascaded H-bridge rectifier is ignored during voltage expression in order to conveniently and efficiently diagnose faults, a large number of iterative calculation processes are avoided, and the fault diagnosis speed is increased. According to the single-phase cascade H-bridge rectifier model and the deduced port level expression, the calculation mode of the network side current of the single-phase cascade H-bridge rectifier is as follows:
according to the single-phase cascaded H-bridge rectifier model, the network side voltage of the single-phase cascaded H-bridge rectifier is expressed as:
Figure BDA0003524123520000071
uaibi＝kiVdci；
wherein, UsThe voltage is the network side voltage of a single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i.e. iNThe current is the network side current of a single-phase cascade H-bridge rectifier; u. ofaibiThe output voltage of the ith H bridge of the single-phase cascade H bridge rectifier;
Vdcithe output voltage value of the ith H bridge of the single-phase cascade H bridge rectifier; k is a radical ofiAn ideal switching function for the ith H bridge of the single-phase cascade H bridge rectifier;
the network side current i of the single-phase cascaded H-bridge rectifier can be obtained through integrationNThe expression is as follows:
Figure BDA0003524123520000072
wherein E ismIs the amplitude of the AC power supply; omega is the angular frequency of the alternating current power supply.
The output level and current flow of the single H-bridge in operation are conducted to the switching tube as shown in fig. 3.
According to the analysis under the condition of different levels of the output of a single H bridge, the conduction conditions of the switching tubes are different due to different current flowing directions in the H bridge under the condition of outputting the same level. The variable of the net side current direction is then added when the switching function is established. Xi represents the measured value i of the network side current of the single-phase cascaded H-bridge rectifiersIs defined as follows:
Figure BDA0003524123520000073
wherein the content of the first and second substances,
Figure BDA0003524123520000074
indicating that ξ is negated.
As can be seen from fig. 3, when the ith H-bridge outputs a positive voltage, when ξ is equal to 1, the device to be turned on is VDi1And VDi4At the moment, the control signals of the four switching tubes are all 0; when xi is equal to 0, the device turned on is VTi2And VTi3At this time, the control signal Si1＝S i41. When xi is 1, if the output is negative level, the control signal is Si2＝Si3When the output is 0 level, the control signal is S i31 or S i21. When xi is 0, the control signal is 0 if the output is at a negative level, and the control signal is S when the output is at a 0 level i11 or S i41. Therefore, the ideal switching function k of the ith H bridge of the single-phase cascade H bridge rectifier is obtainediThe calculation method of (c) is as follows:
ki＝Hai-Hbi；
wherein HaiA switching function of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier; hbiAnd the switching function is the switching function of the ith H-bridge b bridge arm of the single-phase cascade H-bridge rectifier.
Switching function H of ith H-bridge a bridge arm of single-phase cascade H-bridge rectifieraiThe method is established according to the conduction condition of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier, and comprises the following steps:
Figure BDA0003524123520000081
switching function H of ith H-bridge b bridge arm of single-phase cascade H-bridge rectifierbiThe method is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and comprises the following steps:
Figure BDA0003524123520000082
according to the conduction condition of the ith H bridge of the single-phase cascade H bridge rectifier, a logic expression of a switching function is expressed by adopting a conduction signal and a current flow direction of a switching tube as follows:
Figure BDA0003524123520000083
wherein the content of the first and second substances,
Figure BDA0003524123520000084
representing the control signal Si2Taking out of the solution;
Figure BDA0003524123520000085
representing the control signal Si4And (4) taking out the negation.
Step S3, subtracting the calculated value of the network side current of the single-phase cascade H-bridge rectifier from the measured value of the network side current of the single-phase cascade H-bridge rectifier to obtain the network side current error of the single-phase cascade H-bridge rectifier; the method specifically comprises the following steps:
according to the network side current of the single-phase cascade H-bridge rectifier in the step S2iNThe expression of (2) expresses the measured value of the network side current of the single-phase cascade H-bridge rectifier as follows:
Figure BDA0003524123520000086
wherein isThe method comprises the steps that a measured value of the grid-side current of the single-phase cascaded H-bridge rectifier is obtained by a current sensor in fault diagnosis; k is a radical ofiThe switching function of the ith H bridge of the single-phase cascaded H bridge rectifier is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascaded H bridge rectifier;
the method for calculating the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
Figure BDA0003524123520000091
wherein the content of the first and second substances,
Figure BDA0003524123520000092
the single-phase cascade H-bridge rectifier grid-side current error is realized.
Step S4, establishing a fault diagnosis model of the single-phase cascaded H-bridge rectifier according to the network side current error of the single-phase cascaded H-bridge rectifier; the method specifically comprises the following steps:
for single-phase cascade H bridge rectifier network side current error
Figure BDA0003524123520000093
Differentiating to obtain a fault diagnosis model of the single-phase cascade H-bridge rectifier according to current detection, which comprises the following steps:
Figure BDA0003524123520000094
step S5, calculating the value of the single-phase cascade H-bridge rectifier fault diagnosis model, comparing the absolute value with the set threshold value th,
if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is smaller than or equal to the set threshold value, the single-phase cascaded H-bridge rectifier is not in fault, and the step S1 is returned; on the contrary, if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is greater than the set threshold, it represents that the single-phase cascaded H-bridge rectifier has a fault, and the process goes to step S6.
Step S6, establishing a fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier according to the fault diagnosis model of the single-phase cascaded H bridge rectifier, judging the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier, and representing that the ith H bridge of the single-phase cascaded H bridge rectifier has a class a fault if the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier is positive; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascaded H bridge rectifier has b-type faults; wherein, the a-type fault is the switching tube VT of the ith H-bridgei1Or switching tube VTi4Switching tube VT with i-th H-bridge as b-type faulti2Or switch tube VTi3A failure occurs.
The method for establishing the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier according to the fault diagnosis model of the single-phase cascaded H bridge rectifier comprises the following steps:
under the condition that a switching tube of the single-phase cascade H-bridge rectifier has no fault, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k of ith H-bridge of single-phase cascaded H-bridge rectifieriThe method is constant, and the fault diagnosis model of the single-phase cascade H-bridge rectifier is equal to 0;
under the condition that a switching tube of the single-phase cascade H-bridge rectifier fails, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k of ith H-bridge of single-phase cascaded H-bridge rectifieriWhen the current voltage is not equal to the preset voltage, the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is as follows:
Figure BDA0003524123520000101
and sequentially judging whether each H bridge has faults and what kind of faults occur according to the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier.
And step S7, establishing a fault diagnosis function of the switch tube, detecting the corresponding switch tube according to the type of the fault, when the fault diagnosis function value of the corresponding switch tube is 0, representing that the switch tube is not in fault, and when the fault diagnosis function value of the corresponding switch tube is 1, representing that the switch tube is in fault, thus determining the switch tube in fault. The fault diagnosis function of the switching tube is specifically as follows:
Figure BDA0003524123520000102
Figure BDA0003524123520000103
Figure BDA0003524123520000104
Figure BDA0003524123520000105
when in use
Figure BDA0003524123520000106
The value of 1 indicates the switch tube VT of the ith H-bridgei1When a fault occurs and the value is 0, the switch tube VT is indicatedi1No failure occurred. Similarly, it can also be determined whether other switch tubes are in fault. When the fault is judged as a type a fault, the fault is only needed to be carried out
Figure BDA0003524123520000107
And
Figure BDA0003524123520000108
calculating (1); when the type b fault is judged, the method only needs to be carried out
Figure BDA0003524123520000109
And
Figure BDA00035241235200001010
and (4) calculating.
From the output level of fig. 3, it can be found that VT of i-th H-bridge when ξ is equal to 0i1When the tube fails, at the output positive level, due to the actual S i10, so that the actual output is 0 level; if the VT of the ith H-bridgei4When the tube is out of order, at the output positive level, due to the actual Si4And 0, so that the actual output is 0 level. The type a fault can cause the output value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier to be larger than a positive threshold value. Similarly, when xi is 1, if the ith H bridge VTi2When the tube fails, at the output negative level, due to the actual S i20, so that the actual output is 0 level; if the VT of the ith H-bridgei3When the tube fails, at the output negative level, due to the actual Si3And 0, so that the actual output is 0 level. The b-type fault can cause the fault diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier to be smaller than a negative threshold value.
As can be seen from the fault diagnosis flowchart of fig. 1, the fault diagnosis model of the single-phase cascaded H-bridge rectifier is used to determine whether a fault exists in the single-phase cascaded H-bridge rectifier, and if no fault occurs, the following steps are not required, and if a fault occurs, the following steps are required. When the single-phase cascade H-bridge rectifier has a fault, the type of the fault can be judged by judging the symbol of the fault diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier, so that the calculated amount is reduced, and the fault diagnosis efficiency is improved.
In order to verify the effectiveness and the practicability of the invention, simulation verification is carried out on a simulation platform. The specific implementation process comprises the following steps:
the first step is as follows: after the cascaded H-bridge rectifier is built, the controller enables the rectifier to normally operate, real-time fault monitoring is carried out on the cascaded H-bridge rectifier through a normally operating device, and network side current of the cascaded H-bridge rectifier is sampled in a fixed sampling period.
The second step is that: and calculating the network side current of the single-phase cascaded H-bridge rectifier under the condition of no fault to obtain a calculated value of the network side current of the single-phase cascaded H-bridge rectifier, subtracting the calculated value of the network side current of the single-phase cascaded H-bridge rectifier from the sampled measured value of the network side current of the single-phase cascaded H-bridge rectifier in real-time monitoring, and if no fault exists, the difference value is approximately equal to 0.
The third step: at a certain moment, a fault is put into operation, namely, the control signal of a certain switching tube is always 0.
The fourth step: when the single-phase cascaded H-bridge rectifier breaks down, the difference value between the measured grid-side current value of the single-phase cascaded H-bridge rectifier and the calculated grid-side current value of the single-phase cascaded H-bridge rectifier generates deviation near the value of 0, and when the deviation exceeds a threshold value, the single-phase cascaded H-bridge rectifier is determined to break down.
The fifth step: when the single-phase cascade H bridge rectifier breaks down, each H bridge of the single-phase cascade H bridge rectifier is detected one by one, which H bridge breaks down is judged, then the positive and negative of the deviation value are judged, and if the positive deviation occurs, a type a faults occur corresponding to the H bridges. If the deviation is negative, a b-type fault occurs in the corresponding H bridge.
And a sixth step: and detecting the corresponding switch tube according to the type of the fault, and determining the fault switch tube when the fault diagnosis function value of the corresponding switch tube is 1.
FIG. 4 shows the engagement of a class a fault (i.e., VT)11Or VT14Tube failure). It can be seen that the actual current is equal to the value of the calculated current during normal operation. After the fault is input, the difference value between the two values generates positive deviation, the fault diagnosis is carried out on the corresponding switch tube, and finally the VT is determined11A failure occurs. FIG. 5 shows the engagement of class b faults (i.e., VT)12Or VT13Tube failure). It can be seen that the actual current is equal to the value of the calculated current during normal operation. After the fault is input, the difference value between the two values generates negative deviation, the corresponding switch tube is subjected to fault diagnosis, and finally the VT is determined12A failure occurs.
Those of ordinary skill in the art will appreciate that the elements of the examples described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the components of the examples have been described above generally in terms of their functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present application, it should be understood that the division of the unit is only one division of logical functions, and other division manners may be used in actual implementation, for example, multiple units may be combined into one unit, one unit may be split into multiple units, or some features may be omitted.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims (9)

1. A fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection is characterized by comprising the following steps: the method comprises the following steps:
step S1, carrying out real-time fault monitoring on the single-phase cascaded H-bridge rectifier, and carrying out real-time sampling on the network side current of the single-phase cascaded H-bridge rectifier in a fixed sampling period to obtain a measured value of the network side current of the single-phase cascaded H-bridge rectifier; the single-phase cascade H-bridge rectifier comprises a plurality of H-bridges; the ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein the left bridge arm is defined as an a bridge arm, and the right bridge arm is defined as a b bridge arm;wherein VTi1Is a switching tube above the bridge arm, VDi1A diode connected in reverse parallel thereto; VTi2A switching tube under the arm of a, VDi2A diode connected in reverse parallel thereto; VTi3Is a switching tube above the b-bridge arm, VDi3A diode connected in reverse parallel thereto; wherein VTi4Is a switch tube below the b bridge arm, VDi4A diode connected in reverse parallel thereto;
step S2, calculating the network side current of the single-phase cascade H-bridge rectifier under the condition of no fault to obtain a calculated value of the network side current of the single-phase cascade H-bridge rectifier;
step S3, subtracting the calculated value of the network side current of the single-phase cascaded H-bridge rectifier from the measured value of the network side current of the single-phase cascaded H-bridge rectifier to obtain the network side current error of the single-phase cascaded H-bridge rectifier;
step S4, establishing a fault diagnosis model of the single-phase cascaded H-bridge rectifier according to the network side current error of the single-phase cascaded H-bridge rectifier;
step S5, calculating the value of the single-phase cascade H-bridge rectifier fault diagnosis model, comparing the absolute value with the set threshold value th,
if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is smaller than or equal to the set threshold value, the single-phase cascaded H-bridge rectifier is not in fault, and the step S1 is returned; on the contrary, if the absolute value of the fault diagnosis model of the single-phase cascaded H-bridge rectifier is larger than the set threshold, the single-phase cascaded H-bridge rectifier is represented to have a fault, and the step S6 is carried out;
step S6, establishing a fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier according to the fault diagnosis model of the single-phase cascade H bridge rectifier, judging the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier, and representing that the ith H bridge of the single-phase cascade H bridge rectifier has a type a fault if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is positive; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascaded H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascaded H bridge rectifier has b-type faults; wherein, the a-type fault is the switching tube VT of the ith H-bridgei1Or switching tube VTi4Failure, type b failure being of ith H-bridgeSwitching tube VTi2Or switching tube VTi3A failure occurs;
and step S7, establishing a fault diagnosis function of the switch tube, detecting the corresponding switch tube according to the type of the fault, when the fault diagnosis function value of the corresponding switch tube is 0, representing that the switch tube is not in fault, and when the fault diagnosis function value of the corresponding switch tube is 1, representing that the switch tube is in fault, thus determining the switch tube in fault.
2. The fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 1, wherein: in step S2, the network side current of the single-phase cascade H-bridge rectifier is calculated as follows:
according to the single-phase cascaded H-bridge rectifier model, the network side voltage of the single-phase cascaded H-bridge rectifier is expressed as:
Figure FDA0003524123510000021
uaibi＝kiVdci；
wherein, UsThe voltage is the network side voltage of a single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i.e. iNThe current is the network side current of a single-phase cascade H-bridge rectifier; u. ofaibiThe output voltage of the ith H bridge of the single-phase cascade H bridge rectifier;
Vdcithe output voltage value of the ith H bridge of the single-phase cascade H bridge rectifier; k is a radical ofiAn ideal switching function for the ith H bridge of the single-phase cascade H bridge rectifier;
the network side current i of the single-phase cascaded H-bridge rectifier can be obtained through integrationNThe expression is as follows:
Figure FDA0003524123510000022
wherein E ismIs the amplitude of the AC power supply; omega is the angular frequency of the alternating current power supply.
3. The fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 2, wherein: ideal switching function k of ith H-bridge of single-phase cascade H-bridge rectifieriThe calculation of (c) is as follows:
ki＝Hai-Hbi；
wherein HaiA switching function of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier; hbiAnd the switching function is the switching function of the ith H-bridge b bridge arm of the single-phase cascade H-bridge rectifier.
4. The fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 3, wherein: switching function H of ith H-bridge a bridge arm of single-phase cascaded H-bridge rectifieraiThe method is established according to the conduction condition of the ith H-bridge a bridge arm of the single-phase cascade H-bridge rectifier, and comprises the following steps:
Figure FDA0003524123510000023
switching function H of ith H-bridge b bridge arm of single-phase cascade H-bridge rectifierbiThe method is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and comprises the following steps:
Figure FDA0003524123510000024
5. the fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 4, wherein: according to the conduction condition of the ith H bridge of the single-phase cascade H bridge rectifier, a logic expression of a switching function is expressed by adopting a conduction signal and a current flow direction of a switching tube as follows:
Figure FDA0003524123510000031
wherein S isi1Is a switching tube VTi1Control signal of, control signal Si1Is 1 hour VTi1The switch tube is conducted to control the signal Si1Switching tube VT when 0i1Turning off;
Si2is a switching tube VTi2Control signal of, control signal Si2Is 1 hour VTi2The switch tube is conducted to control the signal Si2Switching tube VT when 0i2Turning off;
Figure FDA0003524123510000032
representing the control signal Si2Taking out of the solution;
Si3is a switching tube VTi3Control signal of, control signal Si3Is 1 hour VTi3The switch tube is conducted to control the signal Si3Switching tube VT when 0i3Turning off;
Si4is a switching tube VTi4Control signal of, control signal Si4Is 1 hour VTi4The switch tube is conducted to control the signal Si4Switching tube VT when 0i4Turning off;
Figure FDA0003524123510000033
representing the control signal Si4Taking out of the solution;
xi represents the measured value i of the network side current of the single-phase cascaded H-bridge rectifiersIs defined as follows:
Figure FDA0003524123510000034
wherein the content of the first and second substances,
Figure FDA0003524123510000035
indicating that ξ is negated.
6. The fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 2, wherein: in the step S3, the calculated single-phase cascade H-bridge rectifier network-side current error specifically includes:
according to the network side current i of the single-phase cascade H-bridge rectifier in the step S2NThe expression of (2) expresses the measured value of the network side current of the single-phase cascade H-bridge rectifier as follows:
Figure FDA0003524123510000036
wherein isThe current is measured value of the network side of the single-phase cascade H-bridge rectifier; k'iThe actual switching function of the ith H bridge of the single-phase cascaded H bridge rectifier is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascaded H bridge rectifier; the method for calculating the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
Figure FDA0003524123510000041
wherein the content of the first and second substances,
Figure FDA0003524123510000042
the current error is the network side current error of the single-phase cascade H-bridge rectifier;
7. the fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 6, wherein: the method for establishing the fault diagnosis model of the single-phase cascaded H-bridge rectifier according to the network side current error of the single-phase cascaded H-bridge rectifier specifically comprises the following steps:
for single-phase cascade H bridge rectifier network side current error
Figure FDA0003524123510000043
Differentiating to obtain a single-phase cascade H-bridge rectifier fault diagnosis model according to current detection, which comprises the following specific steps:
Figure FDA0003524123510000044
8. the fault diagnosis method of the single-phase cascaded H-bridge rectifier based on current detection as claimed in claim 7, wherein: in the step S6, the step of establishing the fault diagnosis model of the ith H-bridge of the single-phase cascaded H-bridge rectifier according to the fault diagnosis model of the single-phase cascaded H-bridge rectifier includes:
under the condition that a switching tube of the single-phase cascade H-bridge rectifier has no fault, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k 'of ith H-bridge of single-phase cascaded H-bridge rectifier'iThe method comprises the following steps that (1) the single-phase cascade H-bridge rectifier fault diagnosis model is equal to 0;
under the condition that a switching tube of the single-phase cascade H-bridge rectifier fails, the actual switching function k of the ith H-bridge of the single-phase cascade H-bridge rectifieriIdeal switching function k 'of ith H-bridge of single-phase cascaded H-bridge rectifier'iIf the current voltage is not equal to the preset voltage, the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is as follows:
Figure FDA0003524123510000045
and sequentially judging whether each H bridge has a fault according to the positive and negative conditions of the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier.
9. The fault diagnosis method of the single-phase cascaded H-bridge rectifier based on the current detection as claimed in claim 5, wherein: the fault diagnosis function of the switching tube in the step S7 is specifically:
Figure FDA0003524123510000046
Figure FDA0003524123510000051
Figure FDA0003524123510000052
Figure FDA0003524123510000053
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