CN114545133B - 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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CN114545133B
CN114545133B CN202210189788.XA CN202210189788A CN114545133B CN 114545133 B CN114545133 B CN 114545133B CN 202210189788 A CN202210189788 A CN 202210189788A CN 114545133 B CN114545133 B CN 114545133B
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bridge
bridge rectifier
phase cascade
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switching tube
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CN114545133A (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 cascade H-bridge rectifier based on current detection, which realizes a fault diagnosis end of the single-phase cascade H-bridge rectifier. According to the method, a switching function is established according to the current direction in a bridge arm and control signals of switching tubes, a current calculation model of a single-phase cascade H-bridge rectifier is deduced, the difference value between calculated current and actually measured current in a fault state is obtained according to the current calculation model, a fault diagnosis function of each switching tube is established, and the established fault diagnosis function is utilized to determine a damaged switching tube. According to the invention, whether the switching tube fails or not can be monitored in real time under the running condition of the rectifier; a switching tube capable of locating a fault when the fault occurs; the calculation method is simple and has high efficiency and reliability; the implementation difficulty is low, and no additional hardware is 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 the train are seriously influenced. Power electronic transformers (Power Electronic Transformer, PET) are becoming a hotspot and trend for engineering applications due to their high power density, intelligent control, etc. The cascade H-bridge rectifier (CASCADED H-bridge rectifier, CHBR) is often used as a front-end rectifier module in PET, and the normal operation of CHBR is critical to the back-end part of PET, and if the voltage on the direct current side of CHBR is unbalanced, the stable operation of the system is easily affected.
Taking the operation of PET in a traction power supply system as an example, the PET has a complex operation environment and a high failure rate, and a single phase CHBR contains a large number of power switch devices which are extremely 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. An open circuit failure of the power switching devices in the single phase CHBR does not allow the system to be protected immediately, but it can subject other devices to overvoltage and thus cause secondary damage to the system. The current open circuit fault diagnosis method for the single phase CHBR is few, and the open circuit fault condition in CHBR is complex, so that the damaged switching device is difficult to locate. Therefore, on the basis of few additional sensors, fault diagnosis of the single-phase cascade H-bridge rectifier is often realized by analyzing 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 breaks down in real time under the running condition of the rectifier and can locate the switching tube which breaks down when the switching tube breaks down. The control algorithm can perform real-time fault diagnosis of the single-phase cascade H-bridge rectifier, and 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, performing real-time fault monitoring on a single-phase cascade H-bridge rectifier, and performing real-time sampling on the network side current of the single-phase cascade H-bridge rectifier in a fixed sampling period to obtain a network side current actual measurement value of the single-phase cascade H-bridge rectifier; the single-phase cascade H-bridge rectifier comprises a plurality of H-bridges; an ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein a left side bridge arm is defined as an a bridge arm, and a right side bridge arm is defined as a b bridge arm; wherein VT i1 is a switching tube above the a bridge arm, and VD i1 is an inverse parallel diode thereof; VT i2 is a switch tube below an a bridge arm, and VD i2 is an anti-parallel diode thereof; VT i3 is the switch tube above the b bridge arm, VD i3 is the anti-parallel diode; wherein VT i4 is a switching tube below the b bridge arm, and VD i4 is an inverse parallel diode thereof;
step S2, calculating the network side current of the single-phase cascade H-bridge rectifier under the condition of no fault, and obtaining a network side current calculation value of the single-phase cascade H-bridge rectifier;
step S3, subtracting a network side current calculation value of the single-phase cascade H-bridge rectifier from a network side current actual measurement value of the single-phase cascade H-bridge rectifier to obtain a network side current error of the single-phase cascade H-bridge rectifier;
s4, establishing a fault diagnosis model of the single-phase cascade H-bridge rectifier according to the network side current error of the single-phase cascade H-bridge rectifier;
Step S5, calculating the value of the fault diagnosis model of the single-phase cascade H-bridge rectifier, comparing the absolute value with a set threshold value th,
If the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is smaller than or equal to a set threshold value, the single-phase cascade H-bridge rectifier is represented to be free from faults, and the step S1 is returned; otherwise, if the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is larger than the set threshold value, the single-phase cascade H-bridge rectifier is represented to be faulty, and step S6 is carried out;
S6, establishing a fault diagnosis model of an 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 if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is positive, representing that the ith H bridge of the single-phase cascade H bridge rectifier has an a-type fault; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascade H bridge rectifier has a b-type fault; the class a faults are faults of a switching tube VT i1 or a switching tube VT i4 of the ith H bridge, and the class b faults are faults of a switching tube VT i2 or a switching tube VT i3 of the ith H bridge;
and S7, establishing a fault diagnosis function of the switching tube, detecting the corresponding switching tube according to the type of the fault, and when the fault diagnosis function value of the corresponding switching tube is 0, representing that the switching tube does not have the fault, and when the fault diagnosis function value of the corresponding switching tube is 1, representing that the switching tube has the fault, thus determining the switching tube with the fault.
Preferably, in the step S2, the calculation manner of the network side current of the single-phase cascaded H-bridge rectifier is as follows:
The network side voltage of the single-phase cascade H-bridge rectifier is expressed as according to the single-phase cascade H-bridge rectifier model:
uaibi＝kiVdci；
Wherein U s is the network side voltage of the single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i N is the single-phase cascade H-bridge rectifier net side current; u aibi is the output voltage of the ith H-bridge of the single-phase cascaded H-bridge rectifier;
V dci is the output voltage value of the ith H-bridge of the single-phase cascaded H-bridge rectifier; k i is the ideal switching function of the ith H bridge of the single-phase cascade H bridge rectifier;
The network side current i N of the single-phase cascade H-bridge rectifier can be obtained through integration, and the expression is as follows:
Wherein E m is the amplitude of the alternating current power supply; omega is the angular frequency of the ac power supply.
Preferably, the calculation mode of the ideal switching function k i of the ith H-bridge of the single-phase cascaded H-bridge rectifier is as follows: k i＝Hai-Hbi;
Wherein H ai is the switching function of the ith H bridge a bridge arm of the single-phase cascade H bridge rectifier; h bi is the switching function of the ith H-bridge b-bridge arm of the single-phase cascaded H-bridge rectifier.
Preferably, the switching function H ai of the ith H-bridge a-arm of the single-phase cascaded H-bridge rectifier is established according to the conduction condition of the ith H-bridge a-arm of the single-phase cascaded H-bridge rectifier, and specifically is as follows:
The switching function H bi of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and is specifically as follows:
Preferably, according to the conduction condition of the ith H bridge of the single-phase cascade H bridge rectifier, the conduction signal and the current flow direction of the switching tube are adopted to express the logic expression of the switching function as follows:
Wherein S i1 is a control signal of the switching tube VT i1, when the control signal S i1 is 1, the VT i1 switching tube is turned on, and when the control signal S i1 is 0, the switching tube VT i1 is turned off;
S i2 is a control signal of the switching tube VT i2, when the control signal S i2 is 1, the switching tube VT i2 is turned on, and when the control signal S i2 is 0, the switching tube VT i2 is turned off; Representing the control signal S i2 as not;
S i3 is a control signal of the switching tube VT i3, when the control signal S i3 is 1, the switching tube VT i3 is turned on, and when the control signal S i3 is 0, the switching tube VT i3 is turned off;
S i4 is a control signal of the switching tube VT i4, when the control signal S i4 is 1, the switching tube VT i4 is turned on, and when the control signal S i4 is 0, the switching tube VT i4 is turned off; representing the control signal S i4 as not;
Xi represents the current direction of the net side current measured value i s of the single-phase cascade H-bridge rectifier, and is defined as follows:
wherein, And indicates xi is taken as not.
Preferably, the network side current error of the single-phase cascaded H-bridge rectifier calculated in the step S3 is specifically:
Expressing the net side current actual value of the single-phase cascade H-bridge rectifier as follows according to the expression of the net side current i N of the single-phase cascade H-bridge rectifier in the step S2:
wherein i s is a net side current actual measurement value of the single-phase cascade H-bridge rectifier; k i' is the actual switching function of the ith H bridge of the single-phase cascade H bridge rectifier, and is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascade H bridge rectifier;
The calculation mode of the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
wherein, The current error at the network side of the single-phase cascade H-bridge rectifier;
preferably, the establishing a fault diagnosis model of the single-phase cascade H-bridge rectifier according to the network side current error of the single-phase cascade H-bridge rectifier specifically comprises:
network side current error for single-phase cascade H-bridge rectifier And differentiating to obtain a single-phase cascade H-bridge rectifier fault diagnosis model according to current detection, wherein the single-phase cascade H-bridge rectifier fault diagnosis model comprises the following specific steps of:
Preferably, in the step S6, the building of 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 is specifically:
Under the condition that a switching tube of the single-phase cascade H-bridge rectifier has no fault, the actual switching function k i of the ith H-bridge of the single-phase cascade H-bridge rectifier is constantly equal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, 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 i of the ith H-bridge of the single-phase cascade H-bridge rectifier is unequal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, and then the failure diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier is as follows:
and judging whether each H bridge has faults or not in sequence according to the positive and negative conditions of the values 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 specifically includes:
The beneficial effects of the invention are as follows: according to the invention, whether the switching tube fails or not can be monitored in real time under the running condition of the rectifier; a switching tube capable of locating a fault when the fault occurs; the calculation method is simple and has high efficiency and reliability; the implementation difficulty is low, and no additional hardware is required to be added.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.
FIG. 1 is a schematic flow chart of the present invention;
FIG. 2 is a basic circuit topology of a single-phase cascaded H-bridge rectifier of the present invention;
FIG. 3 is a graph of current-voltage relationship for a single-phase cascaded H-bridge rectifier under normal operation;
FIG. 4 is a diagram of a fault diagnosis key waveform under a class a fault;
Fig. 5 is a waveform diagram of a fault diagnosis key under a class b fault.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. 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.
It should be understood that the terms "comprises" and "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 is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification 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 the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
As shown in fig. 1, the embodiment of the invention provides a fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection, which comprises the following steps:
step S1, performing real-time fault monitoring on a single-phase cascade H-bridge rectifier, and performing real-time sampling on the network side current of the single-phase cascade H-bridge rectifier in a fixed sampling period to obtain a network side current actual measurement value of the single-phase cascade H-bridge rectifier; as shown in fig. 2, the single-phase cascaded H-bridge rectifier comprises a number of H-bridges; an ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein a left side bridge arm is defined as an a bridge arm, and a right side bridge arm is defined as a b bridge arm; wherein VT i1 is a switching tube above the a bridge arm, and VD i1 is an inverse parallel diode thereof; VT i2 is a switch tube below an a bridge arm, and VD i2 is an anti-parallel diode thereof; VT i3 is the switch tube above the b bridge arm, VD i3 is the anti-parallel diode; wherein VT i4 is a switching tube below the b bridge arm, and VD i4 is an inverse parallel diode thereof; wherein S i1 is a control signal of the switching tube VT i1, when the control signal S i1 is 1, the VT i1 switching tube is turned on, and when the control signal S i1 is 0, the switching tube VT i1 is turned off; s i2 is a control signal of the switching tube VT i2, when the control signal S i2 is 1, the switching tube VT i2 is turned on, and when the control signal S i2 is 0, the switching tube VT i2 is turned off; s i3 is a control signal of the switching tube VT i3, when the control signal S i3 is 1, the switching tube VT i3 is turned on, and when the control signal S i3 is 0, the switching tube VT i3 is turned off; s i4 is a control signal of the switching transistor VT i4, when the control signal S i4 is 1, the switching transistor VT i4 is turned on, and when the control signal S i4 is 0, the switching transistor VT i4 is turned off.
And S2, calculating the network side current of the single-phase cascade H-bridge rectifier under the condition of no fault, and obtaining a network side current calculation value of the single-phase cascade H-bridge rectifier. According to the topology model of fig. 1, an expression of the network side voltage of the single-phase cascade H-bridge rectifier can be established, so that the network side resistance of the single-phase cascade H-bridge rectifier is ignored when the voltage expression is carried out, a large number of iterative calculation processes are avoided, and the fault diagnosis speed is improved. 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:
The network side voltage of the single-phase cascade H-bridge rectifier is expressed as according to the single-phase cascade H-bridge rectifier model:
uaibi＝kiVdci；
Wherein U s is the network side voltage of the single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i N is the single-phase cascade H-bridge rectifier net side current; u aibi is the output voltage of the ith H-bridge of the single-phase cascaded H-bridge rectifier;
V dci is the output voltage value of the ith H-bridge of the single-phase cascaded H-bridge rectifier; k i is the ideal switching function of the ith H bridge of the single-phase cascade H bridge rectifier;
The network side current i N of the single-phase cascade H-bridge rectifier can be obtained through integration, and the expression is as follows:
Wherein E m is the amplitude of the alternating current power supply; omega is the angular frequency of the ac power supply.
The output level and current flow of a single H-bridge in operation are shown in fig. 3 in connection with the switching tube conduction.
According to analysis under different level conditions of the output of a single H bridge, the conduction condition of the switching tube is different under the condition of the same level of the output due to different current flow directions in the H bridge. The variable of the net side current direction is then added at the time of the establishment of the switching function. Xi represents the current direction of the net side current measured value i s of the single-phase cascade H-bridge rectifier, and is defined as follows:
wherein, And indicates xi is taken as not.
As can be seen from fig. 3, when the ith H-bridge outputs positive level, if ζ=1, the devices that are turned on are VD i1 and VD i4, and at this time, the control signals of the four switching tubes are all 0; if ζ=0, the devices turned on are VT i2 and VT i3, and the control signal S i1＝Si4 =1. Similarly, when ζ=1, if the output is negative, the control signal is S i2＝Si3 =1, and if the output is 0, the control signal is S i3 =1 or S i2 =1. When ζ=0, if the outputs are negative levels, the control signals are all 0, and when the outputs are 0 levels, the control signals are S i1 =1 or S i4 =1. The calculation of the ideal switching function k i for the ith H-bridge of the single-phase cascaded H-bridge rectifier is thus as follows:
ki＝Hai-Hbi；
Wherein H ai is the switching function of the ith H bridge a bridge arm of the single-phase cascade H bridge rectifier; h bi is the switching function of the ith H-bridge b-bridge arm of the single-phase cascaded H-bridge rectifier.
The switching function H ai of the ith H-bridge a-arm of the single-phase cascade H-bridge rectifier is established according to the conduction condition of the ith H-bridge a-arm of the single-phase cascade H-bridge rectifier, and is specifically as follows:
The switching function H bi of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and is specifically as follows:
According to the conduction condition of the ith H bridge of the single-phase cascade H bridge rectifier, a conduction signal and a current flow direction of a switching tube are adopted to express a switch function logic expression as follows:
wherein, Representing the control signal S i2 as not; /(I)Indicating that the control signal S i4 is taken off.
Step S3, subtracting a network side current calculation value of the single-phase cascade H-bridge rectifier from a network side current actual measurement value of the single-phase cascade H-bridge rectifier to obtain a network side current error of the single-phase cascade H-bridge rectifier; the method comprises the following steps:
Expressing the net side current actual value of the single-phase cascade H-bridge rectifier as follows according to the expression of the net side current i N of the single-phase cascade H-bridge rectifier in the step S2:
Wherein i s is a net side current actual measurement value of the single-phase cascade H-bridge rectifier, and the value is obtained by a current sensor in fault diagnosis; k i' is the actual switching function of the ith H bridge of the single-phase cascade H bridge rectifier, and is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascade H bridge rectifier;
The calculation mode of the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
wherein, Is the network side current error of the single-phase cascade H-bridge rectifier.
S4, establishing a fault diagnosis model of the single-phase cascade H-bridge rectifier according to the network side current error of the single-phase cascade H-bridge rectifier; the method comprises the following steps:
network side current error for single-phase cascade H-bridge rectifier And differentiating to obtain a single-phase cascade H-bridge rectifier fault diagnosis model according to current detection, wherein the single-phase cascade H-bridge rectifier fault diagnosis model comprises the following specific steps of:
Step S5, calculating the value of the fault diagnosis model of the single-phase cascade H-bridge rectifier, comparing the absolute value with a set threshold value th,
If the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is smaller than or equal to a set threshold value, the single-phase cascade H-bridge rectifier is represented to be free from faults, and the step S1 is returned; otherwise, if the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is larger than the set threshold, the single-phase cascade H-bridge rectifier is represented to be faulty, and step S6 is carried out.
S6, establishing a fault diagnosis model of an 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 if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is positive, representing that the ith H bridge of the single-phase cascade H bridge rectifier has an a-type fault; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascade H bridge rectifier has a b-type fault; the a-type fault is a fault of a switching tube VT i1 or a switching tube VT i4 of the ith H bridge, and the b-type fault is a fault of a switching tube VT i2 or a switching tube VT i3 of the ith H bridge.
The method for establishing the 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 specifically 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 i of the ith H-bridge of the single-phase cascade H-bridge rectifier is constantly equal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, 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 i of the ith H-bridge of the single-phase cascade H-bridge rectifier is unequal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, and then the failure diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier is as follows:
And judging whether each H bridge has faults or not and what kind of faults occur according to the positive and negative conditions of the values of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier.
And S7, establishing a fault diagnosis function of the switching tube, detecting the corresponding switching tube according to the type of the fault, and when the fault diagnosis function value of the corresponding switching tube is 0, representing that the switching tube does not have the fault, and when the fault diagnosis function value of the corresponding switching tube is 1, representing that the switching tube has the fault, thus determining the switching tube with the fault. The fault diagnosis function of the switching tube is specifically as follows:
When (when) When the value is 1, the switching tube VT i1 of the ith H bridge is in fault, and when the value is 0, the switching tube VT i1 is not in fault. Similarly, whether other switching tubes have faults can be judged. When judging the a-type fault, only need to doAnd/>Is calculated; when the type b fault is judged, the method only needs to be carried outAnd/>Is calculated by the computer.
From the output level of fig. 3, it can be found that when ζ=0, if the VT i1 pipe of the ith H-bridge fails, at the output level, the actual output is at the 0 level due to the actual S i1 =0; when the VT i4 pipe of the ith H-bridge fails, the actual output is at the 0 level because of the actual S i4 =0 when the output is at the positive level. a class a fault may result in the output value of the fault diagnosis model of the ith H-bridge of the single-phase cascaded H-bridge rectifier being greater than a positive threshold. Similarly, when ζ=1, if the VT i2 pipe of the ith H-bridge fails, when the output level is at the negative level, the actual output is at the 0 level because of the actual S i2 =0; when the VT i3 pipe of the ith H-bridge fails, the actual output is at the 0 level because of the actual S i3 =0 when the output is at the negative level. Class b faults may result in the fault diagnosis model for the ith H-bridge of the single-phase cascaded H-bridge rectifier being less than a negative threshold.
As can be seen from the fault diagnosis flow chart of fig. 1, whether the single-phase cascade H-bridge rectifier has a fault or not is judged by the fault diagnosis model of the single-phase cascade H-bridge rectifier, if no fault occurs, the following steps are not needed, and if the fault occurs, the following steps are needed. When the single-phase cascade H-bridge rectifier fails, the type of the failure can be judged by judging the sign of the failure diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier, so that the calculated amount is reduced, and the failure 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: after the cascade H-bridge rectifier is built, the controller enables the rectifier to normally operate, real-time fault monitoring is conducted on the cascade H-bridge rectifier through normal operation devices, and network side current of the cascade H-bridge rectifier is sampled in a fixed sampling period.
And a second step of: and calculating the network side current of the single-phase cascade H-bridge rectifier under the fault-free condition to obtain a network side current calculation value of the single-phase cascade H-bridge rectifier, subtracting the network side current calculation value of the single-phase cascade H-bridge rectifier from the sampled network side current actual measurement value of the single-phase cascade H-bridge rectifier in real-time monitoring, and if the single-phase cascade H-bridge rectifier has no fault, obtaining a difference value approximately equal to 0.
And a third step of: at a certain moment, a fault is put into, i.e. the control signal of a certain switching tube is always 0.
Fourth step: when the single-phase cascade H-bridge rectifier fails, a difference value between a net side current measured value of the single-phase cascade H-bridge rectifier and a net side current calculated value of the single-phase cascade H-bridge rectifier generates a deviation around 0 value, and when the deviation exceeds a threshold value, the single-phase cascade H-bridge rectifier is determined to fail.
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 positive deviation occurs, a class-a fault occurs to the corresponding H bridge. If the deviation is negative, a b-type fault occurs in the corresponding H-bridge.
Sixth step: and detecting the corresponding switching tube according to the type of the fault, and determining the faulty switching tube when the fault diagnosis function value of the corresponding switching tube is 1.
Fig. 4 is a waveform diagram of fault diagnosis for a drop-in type a fault (i.e., a VT 11 or a VT 14 pipe fault). It can be seen that the actual current is equal to the calculated current value during normal operation. After the fault is input, the difference value between the two faults generates forward deviation, fault diagnosis is carried out on the corresponding switching tube, and finally, the VT 11 is determined to be faulty. Fig. 5 is a waveform diagram of a fault diagnosis of a drop-in type b fault (i.e., a VT 12 or a VT 13 pipe fault). It can be seen that the actual current is equal to the calculated current value during normal operation. After the fault is input, negative deviation occurs to the difference value between the two faults, fault diagnosis is carried out on the corresponding switching tube, and finally, the occurrence of the fault of VT 12 is determined.
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 elements of the examples have been described generally in terms of functionality in the foregoing description to clearly illustrate this 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 solution. 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 units is merely a logic function division, and there may be other division manners 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 for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention, and are intended to be included within the scope of the appended claims and description.

Claims (5)

1. A fault diagnosis method of a single-phase cascade H-bridge rectifier based on current detection is characterized by comprising the following steps of: the method comprises the following steps:
Step S1, performing real-time fault monitoring on a single-phase cascade H-bridge rectifier, and performing real-time sampling on the network side current of the single-phase cascade H-bridge rectifier in a fixed sampling period to obtain a network side current actual measurement value of the single-phase cascade H-bridge rectifier; the single-phase cascade H-bridge rectifier comprises a plurality of H-bridges; an ith H bridge in the single-phase cascade H bridge rectifier is divided into two bridge arms, wherein a left side bridge arm is defined as an a bridge arm, and a right side bridge arm is defined as a b bridge arm; wherein VT i1 is a switching tube above the a bridge arm, and VD i1 is an inverse parallel diode thereof; VT i2 is a switch tube below an a bridge arm, and VD i2 is an anti-parallel diode thereof; VT i3 is the switch tube above the b bridge arm, VD i3 is the anti-parallel diode; wherein VT i4 is a switching tube below the b bridge arm, and VD i4 is an inverse parallel diode thereof;
Step S2, calculating the network side current of the single-phase cascade H-bridge rectifier under the condition of no fault, and obtaining a network side current calculation value of the single-phase cascade H-bridge rectifier; in the step S2, the calculation mode of the network side current of the single-phase cascaded H-bridge rectifier is as follows:
The network side voltage of the single-phase cascade H-bridge rectifier is expressed as according to the single-phase cascade H-bridge rectifier model:
uaibi＝kiVdci；
Wherein U s is the network side voltage of the single-phase cascade H-bridge rectifier; l is the inductance value of the network side of the single-phase cascade H-bridge rectifier; i N is the single-phase cascade H-bridge rectifier net side current; u aibi is the output voltage of the ith H-bridge of the single-phase cascaded H-bridge rectifier;
V dci is the output voltage value of the ith H-bridge of the single-phase cascaded H-bridge rectifier; k i is the ideal switching function of the ith H bridge of the single-phase cascade H bridge rectifier;
The network side current i N of the single-phase cascade H-bridge rectifier can be obtained through integration, and the expression is as follows:
Wherein E m is the amplitude of the alternating current power supply; omega is the angular frequency of the alternating current power supply;
step S3, subtracting a network side current calculation value of the single-phase cascade H-bridge rectifier from a network side current actual measurement value of the single-phase cascade H-bridge rectifier to obtain a network side current error of the single-phase cascade H-bridge rectifier; the network side current error of the single-phase cascade H-bridge rectifier with the calculated value in the step S3 is specifically as follows:
Expressing the net side current actual value of the single-phase cascade H-bridge rectifier as follows according to the expression of the net side current i N of the single-phase cascade H-bridge rectifier in the step S2:
wherein i s is a net side current actual measurement value of the single-phase cascade H-bridge rectifier; k i' is the actual switching function of the ith H bridge of the single-phase cascade H bridge rectifier, and is determined by the actual conduction condition of each switching tube in the ith H bridge of the single-phase cascade H bridge rectifier;
The calculation mode of the network side current error of the single-phase cascade H-bridge rectifier specifically comprises the following steps:
wherein, The current error at the network side of the single-phase cascade H-bridge rectifier;
s4, establishing a fault diagnosis model of the single-phase cascade H-bridge rectifier according to the network side current error of the single-phase cascade H-bridge rectifier; the method comprises the following steps:
network side current error for single-phase cascade H-bridge rectifier And differentiating to obtain a single-phase cascade H-bridge rectifier fault diagnosis model according to current detection, wherein the single-phase cascade H-bridge rectifier fault diagnosis model comprises the following specific steps of:
Step S5, calculating the value of the fault diagnosis model of the single-phase cascade H-bridge rectifier, comparing the absolute value with a set threshold value th,
If the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is smaller than or equal to a set threshold value, the single-phase cascade H-bridge rectifier is represented to be free from faults, and the step S1 is returned; otherwise, if the absolute value of the fault diagnosis model of the single-phase cascade H-bridge rectifier is larger than the set threshold value, the single-phase cascade H-bridge rectifier is represented to be faulty, and step S6 is carried out;
S6, establishing a fault diagnosis model of an 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 if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is positive, representing that the ith H bridge of the single-phase cascade H bridge rectifier has an a-type fault; if the value of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier is negative, representing that the ith H bridge of the single-phase cascade H bridge rectifier has a b-type fault; the class a faults are faults of a switching tube VT i1 or a switching tube VT i4 of the ith H bridge, and the class b faults are faults of a switching tube VT i2 or a switching tube VT i3 of the ith H bridge; the method for establishing the 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 specifically 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 i of the ith H-bridge of the single-phase cascade H-bridge rectifier is constantly equal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, 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 i of the ith H-bridge of the single-phase cascade H-bridge rectifier is unequal to the ideal switching function k i' of the ith H-bridge of the single-phase cascade H-bridge rectifier, and then the failure diagnosis model of the ith H-bridge of the single-phase cascade H-bridge rectifier is as follows:
Judging whether each H bridge has faults or not in sequence according to the positive and negative conditions of the values of the fault diagnosis model of the ith H bridge of the single-phase cascade H bridge rectifier;
and S7, establishing a fault diagnosis function of the switching tube, detecting the corresponding switching tube according to the type of the fault, and when the fault diagnosis function value of the corresponding switching tube is 0, representing that the switching tube does not have the fault, and when the fault diagnosis function value of the corresponding switching tube is 1, representing that the switching tube has the fault, thus determining the switching tube with the fault.
2. The fault diagnosis method for the single-phase cascade H-bridge rectifier based on current detection according to claim 1, wherein: the calculation mode of the ideal switching function k i of the ith H bridge of the single-phase cascade H bridge rectifier is as follows:
ki＝Hai-Hbi；
Wherein H ai is the switching function of the ith H bridge a bridge arm of the single-phase cascade H bridge rectifier; h bi is the switching function of the ith H-bridge b-bridge arm of the single-phase cascaded H-bridge rectifier.
3. The fault diagnosis method for the single-phase cascade H-bridge rectifier based on current detection according to claim 2, wherein: the switching function H ai of the ith H-bridge a-bridge arm of the single-phase cascade H-bridge rectifier is established according to the conduction condition of the ith H-bridge a-bridge arm of the single-phase cascade H-bridge rectifier, and is specifically as follows:
The switching function H bi of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier is established according to the conduction condition of the ith H bridge b bridge arm of the single-phase cascade H bridge rectifier, and is specifically as follows:
4. A fault diagnosis method for a single-phase cascaded H-bridge rectifier based on current detection as in claim 3, wherein: according to the conduction condition of the ith H bridge of the single-phase cascade H bridge rectifier, a conduction signal and a current flow direction of a switching tube are adopted to express a switch function logic expression as follows:
Wherein S i1 is a control signal of the switching tube VT i1, when the control signal S i1 is 1, the VT i1 switching tube is turned on, and when the control signal S i1 is 0, the switching tube VT i1 is turned off;
S i2 is a control signal of the switching tube VT i2, when the control signal S i2 is 1, the switching tube VT i2 is turned on, and when the control signal S i2 is 0, the switching tube VT i2 is turned off; Representing the control signal S i2 as not;
S i3 is a control signal of the switching tube VT i3, when the control signal S i3 is 1, the switching tube VT i3 is turned on, and when the control signal S i3 is 0, the switching tube VT i3 is turned off;
S i4 is a control signal of the switching tube VT i4, when the control signal S i4 is 1, the switching tube VT i4 is turned on, and when the control signal S i4 is 0, the switching tube VT i4 is turned off; representing the control signal S i4 as not;
Xi represents the current direction of the net side current measured value i s of the single-phase cascade H-bridge rectifier, and is defined as follows:
wherein, And indicates xi is taken as not.
5. The fault diagnosis method for the single-phase cascade H-bridge rectifier based on current detection according to claim 4, wherein: the fault diagnosis function of the switching tube in the step S7 specifically includes:
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