CN113466596A - Fault diagnosis method for single-phase three-level cascade inverter - Google Patents
Fault diagnosis method for single-phase three-level cascade inverter Download PDFInfo
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Abstract
The invention discloses a fault diagnosis method of a single-phase three-level cascade inverter, which comprises the following steps: s1: setting a numbering rule of a switching tube in the single-phase three-level cascade inverter; s2: numbering the switching tubes of the single-phase three-level cascade inverter according to the numbering rule; s3: collecting fault sample data of the single-phase three-level cascade inverter; s4: digitizing the fault sample data according to the numbering result to obtain different digital character strings; s5: and obtaining corresponding fault diagnosis results according to the different digital character strings. According to the fault diagnosis method of the single-phase three-level cascade inverter, provided by the invention, the fault can be positioned to a specific device in a specific module by only using the self-carried voltage and current sensor in the through type power supply system without additionally adding the sensor, so that the hardware cost of the system is reduced, and the reliability of the system is improved.
Description
Technical Field
The invention relates to the technical field of inverter fault diagnosis, in particular to a fault diagnosis method for a single-phase three-level cascade inverter.
Background
With the development of power electronic technology, power electronic converters are widely applied to high-power occasions, and multilevel converter technology is developed in order to adapt to high voltage and large current of the high-power occasions. The diode-clamped three-level cascade converter has the advantages of high output voltage level, high equivalent switching frequency, low harmonic content and the like, and is widely applied to medium and high voltage occasions, such as the fields of photovoltaic grid-connected systems, through-type traction power supply systems and the like. However, the multi-level circuit uses a large number of switching devices, and a failure of any one device may cause the whole circuit to stop working, resulting in a decrease in the reliability of the converter, an immeasurable economic loss, and even a catastrophic accident. Generally, the faults of the power converter can be divided into open-circuit faults and short-circuit faults of the switching tube. Because the short-circuit fault exists for a very short time (usually within 10 us) and is difficult to diagnose, a hardware circuit is generally adopted for processing or a fast fuse is added to convert the short-circuit fault into an open-circuit fault, and the open-circuit fault is processed by using a diagnosis method of the open-circuit fault. Therefore, it is necessary to research an open-circuit fault diagnosis technology of the cascaded NPC inverter, so as to achieve the purposes of reducing maintenance cost, reducing unexpected shutdown time, and improving system operation reliability.
There have been some research foundations at home and abroad for fault diagnosis of inverters. The method mainly comprises two steps: the first method is to model the circuit, analyze and summarize the fault characteristics, and directly utilize the hardware circuit to realize fault diagnosis; and the other method is that the required sensor is additionally added to extract the voltage or current of the output side, the voltage or current is subjected to mathematical processing and then is used as a fault characteristic quantity, and then the fault diagnosis is realized by using methods such as a Bayesian network and a support vector machine. However, for the cascaded NPC inverter, if a fault diagnosis method of a common inverter is still adopted, due to the fact that the number of modules is large, multiple circuits in a switching state are complex, circuit modeling is difficult, fault diagnosis is difficult, and cost is high. And the extra addition of too many sensors not only increases the cost of the system, but also increases the unreliability of the system itself.
Therefore, for the cascaded NPC inverter in the through-type power supply system, it is necessary to research a method for efficiently diagnosing faults without additionally adding sensors.
Disclosure of Invention
The invention aims to locate a fault to a specific device in a specific module by only using a self-contained voltage and current sensor in a through type power supply system without additionally increasing the sensor, thereby reducing the hardware cost of the system and improving the reliability of the system.
The technical scheme for solving the technical problems is as follows:
the invention provides a fault diagnosis method of a single-phase three-level cascade inverter, which comprises the following steps:
s1: setting a numbering rule of a switching tube in the single-phase three-level cascade inverter;
s2: numbering the switching tubes of the single-phase three-level cascade inverter according to the numbering rule;
s3: collecting fault sample data of the single-phase three-level cascade inverter;
s4: according to the fault sample data, digitizing the fault sample data, and determining the positions of a fault module and a specific switch tube by utilizing information fusion to obtain different digital character strings;
s5: and obtaining corresponding fault diagnosis results according to the different digital character strings.
Alternatively, the step S2 includes the following substeps:
s21: sequentially labeling the three modules of the single-phase three-level cascade inverter to obtain labels 1, 2 and 3;
s22: sequentially labeling the first bridge arm of each of the three modules from top to bottom to obtain a label Si1、Si2、Si3And Si4；
S23: sequentially labeling the second bridge arm of each of the three modules from top to bottom to obtain a label Si5、Si6、Si7And Si8。
Optionally, in the step S3, the current and voltage sensor inside the pass-through power supply system collects sample data of the single-phase three-level cascade inverter.
Alternatively, the step S3 includes:
performing inter-module fault detection on three modules of the single-phase three-level cascade inverter to determine a fault module; and/or
And carrying out fault detection on all switching tubes in the fault module, and determining fault switching tubes.
Alternatively, the step S4 includes the following substeps:
s41: determining an encoding rule of the numeric character string;
s42: determining the total digits of the numeric character string and the meaning of each character in the numeric character string according to the encoding rule of the numeric character string;
s43: and according to the fault sample data, obtaining different digital character strings by adopting the method of the step S42.
Alternatively, in step S42, the total number of digits of the numeric character string is determined to be 7 digits.
Alternatively, in step S42, the determining the meaning of each character in the numeric character string is: the first three digits of the digital character string represent the module number where the fault module is located in a binary mode, the last four digits of the digital character string represent the number of the fault switch tube in the binary mode, and the digital character string 0000000 represents that no fault occurs.
The invention has the following beneficial effects:
1. the single-tube fault diagnosis of the multi-module cascaded NPC system can be realized by only utilizing the current and voltage sensor in the through type power supply system without additionally adding a sensor, the hardware cost and the size of the fault diagnosis are reduced, and the reliability of the system is improved;
2. compared with the method for identifying the module where the fault is located, the method positions the fault to the device level of the specific fault;
3. the installation position of the direct current side current sensor is selectable and can be installed on the direct current side of any module;
4. the method is independent of the number of cascaded modules, so that the method is generally applicable to different inverters.
Drawings
Fig. 1 is a flowchart of a fault diagnosis method for a single-phase three-level cascade inverter according to the present invention;
FIG. 2 is a flowchart illustrating the substeps of step S2 in FIG. 1;
FIG. 3 is a flowchart illustrating the substeps of step S4 in FIG. 1;
fig. 4 is a topology structure diagram of a single-phase three-level cascade inverter provided by the invention;
fig. 5 is a simulation waveform diagram of dc side bus current for inter-module fault detection of the single-phase three-level cascade inverter provided by the present invention;
fig. 6 is a simulated waveform diagram of output voltage of fault detection of switching tubes in a module of the single-phase three-level cascade inverter provided by the invention;
fig. 7 is a block diagram of a fault diagnosis system of a single-phase three-level cascade inverter provided by the present invention;
fig. 8 is a diagram illustrating a result of fault diagnosis of the single-phase three-level cascade inverter according to the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
Examples
The technical scheme for solving the technical problems is as follows:
the invention provides a fault diagnosis method of a single-phase three-level cascade inverter, which is shown in a reference figure 1 and comprises the following steps:
s1: setting a numbering rule of a switching tube in the single-phase three-level cascade inverter;
s2: numbering the switching tubes of the single-phase three-level cascade inverter according to the numbering rule;
s3: collecting fault sample data of the single-phase three-level cascade inverter;
s4: according to the fault sample data, digitizing the fault sample data, and determining the positions of a fault module and a specific switch tube by utilizing information fusion to obtain different digital character strings;
s5: and obtaining corresponding fault diagnosis results according to the different digital character strings.
The invention has the following beneficial effects:
1. the single-tube fault diagnosis of the multi-module cascaded NPC system can be realized by only utilizing the current and voltage sensor in the through type power supply system without additionally adding a sensor, the hardware cost and the size of the fault diagnosis are reduced, and the reliability of the system is improved;
2. compared with the method for identifying the module where the fault is located, the method positions the fault to the device level of the specific fault;
3. the installation position of the direct current side current sensor is selectable and can be installed on the direct current side of any module;
4. the method is independent of the number of cascaded modules, so that the method is generally applicable to different inverters.
Alternatively, referring to fig. 2, the step S2 includes the following sub-steps:
s21: sequentially labeling the three modules of the single-phase three-level cascade inverter to obtain labels 1, 2 and 3;
s22: sequentially labeling the first bridge arm of each of the three modules from top to bottom to obtain a label Si1、Si2、Si3And Si4；
S23: sequentially labeling the second bridge arm of each of the three modules from top to bottom to obtain a label Si5、Si6、Si7And Si8。
Optionally, in the step S3, the current and voltage sensor inside the pass-through power supply system collects sample data of the single-phase three-level cascade inverter.
Alternatively, the step S3 includes:
performing inter-module fault detection on three modules of the single-phase three-level cascade inverter to determine a fault module; and/or
And carrying out fault detection on all switch tubes in the module of the fault module to determine the fault switch tube.
Specifically, the current sensor Is arranged on a direct current input current side (Is) of each module, N sensors are cascaded to N modules, and the current sensor Is used for judging which module has a fault; the number of the voltage sensors is 1 at the port of the cascade output, and the voltage sensors are used for judging which switching tube has a fault.
In the through power supply system, the embedded current and voltage sensor continuously collects related current and voltage quantity to monitor whether the through power supply system normally operates. When the switching tube in the cascade inverter breaks down, the fault sample data can enter a fault diagnosis link through the sensor. At this time, the inter-module diagnosis and the switch tube diagnosis are simultaneously carried out, and the data are not influenced mutually.
After the current sensor collects the data, the fault information between the modules can be output through the judgment of a logic threshold value; after the voltage sensor collects information, amplitude and phase of related characteristic subharmonic are analyzed and collected through FFT, and fault information of the switching tube is comprehensively judged. And the two pieces of information are subjected to information fusion, so that which switching tube of which module of the cascade inverter has a fault can be accurately output.
Alternatively, referring to fig. 3, the step S4 includes the following sub-steps:
s41: determining an encoding rule of the numeric character string;
s42: determining the total digits of the numeric character string and the meaning of each character in the numeric character string according to the encoding rule of the numeric character string;
s43: and obtaining different digital character strings according to the fault sample data and the step S42.
Alternatively, in step S42, the total number of digits of the numeric character string is determined to be 7 digits.
Optionally, the determining the meaning of each character in the numeric string is: the first three digits of the digital character string represent the module number where the fault module is located in a binary mode, the last four digits of the digital character string represent the number of the fault switch tube in the binary mode, and the digital character string 0000000 represents that no fault occurs.
The following explains the fault diagnosis method of the single-phase three-level cascade inverter provided by the invention:
the invention provides a fault diagnosis device and method based on a cascaded diode neutral point clamped inverter in a through type power supply system. The applied topological structure diagram is shown in fig. 4. The port 1a of the unit 1 is connected with the port L of the load, the port 1b of the unit 1 is connected with the port 2a of the unit 2, the port 2b of the unit 2 is connected with the port 3a of the unit 3, and the like; the ia port of the unit i is connected with the (i-1) b port of the i-1 unit, the ib port of the unit i is connected with the (i +1) a port of the unit i +1, and so on, the Na port of the unit N is connected with the (N-1) b port of the unit N-1, the Nb port of the unit N is connected with the G end of the load, and i belongs to [1, N ]. In the through type power supply system, in order to ensure the stable operation of the system, corresponding current and voltage sensors are arranged on the direct current side and the output side of each cascade inverter, and the collection of fault information can be realized by utilizing the current and voltage sensors arranged on the system.
Analysis of I in the plot by real-time detectionsAnd UoutAnd the positioning of the fault switch tube is realized by combining the information fusion technology. The main controller FPGA independently operates to generate a driving signal, and the driving signal is connected with 8 power switches on a bridge arm through a driving circuit of each module to control the normal operation of the cascade inverter; meanwhile, a direct current bus side current and cascade voltage side sensor connected in series with the ith unit transmits a real-time current and voltage signal to an AD sampling board, and the AD sampling board digitalizes an analog signal and transmits the digital signal into an FPGA; embedding a fault diagnosis method in the FPGA, and extracting and diagnosing fault characteristic quantity in real time; and finally, the FPGA outputs a corresponding diagnosis result.
And constructing a single-phase 3-module cascaded NPC inverter based on Matlab/simulink software. The control method adopts single-voltage closed-loop control, and the modulation method adopts a mixed modulation mode of carrier shift plus carrier lamination. Matlab/simulink software is used for simulation, the input direct-current voltage is 7000V, the load is 100 omega, the supporting capacitance is 20mF, and modulation is carried outWave frequency f050Hz, carrier frequency fs1000 Hz. FIG. 5 is a DC side bus current simulation waveform for normal and inter-module faults of a cascaded NPC inverter to which the present invention is applied; in consideration of circuit symmetry and space limitations, fig. 6 shows the simulated waveforms of the cascade output voltage when the switching tubes in the first arm of the module are normal and failed.
Fault diagnosis between modules via IsAnd (4) determining the change. When the sensor acquires that a certain module has a wave lack phenomenon, the module can be judged to have a fault. The fault diagnosis of the specific switch tube in the module utilizes the cascade output voltage to judge, the FFT analysis is carried out on the cascade output voltage, the content and the phase position of each corresponding harmonic wave are collected, and the switch tubes can be locked one by one according to the different harmonic wave content and the different phase positions when different switch tubes have faults. The current sensor at the side of the direct current bus and the voltage sensor data output by the cascade are comprehensively utilized to carry out information fusion, and the fault diagnosis and the positioning of the cascade inverter can be realized.
Table 1 module 1 different switching tube fault cascade output side voltage harmonic amplitude (content) and phase
And (4) coding different fault types, wherein the coding comprises 7 digits, the first three digits represent the serial number of the module where the fault occurs in a binary mode, and the last four digits represent the serial number of the fault pipe in the binary mode (the serial number mode is the same as that of the component a). If code 1000001, the first switch tube (S) in module 1 is shown11) A failure; code 0010010 indicates the second switch tube (S) in module 332) A failure; specifically, let the code 0000000 denote no fault occurred. And digitizing the fault in a coding mode to be used as an output of fault diagnosis.
TABLE 2 Fault Module code
| Fault module | Encoding |
| Fault-free module | 000 |
| Switching tube failure in |
100 |
| Switching tube failure in module 2 | 010 |
| Switching tube failure in module 3 | 001 |
TABLE 3 Fault switch tube location code
Fig. 7 is a general block diagram of a fault diagnosis system of a cascaded NPC inverter, which includes a main circuit module, a voltage closed-loop control module, a modulation module, a fault characteristic quantity extraction module, and a diagnosis module.
Firstly, a driving signal generated by an FPGA control algorithm and a modulation algorithm is used for controlling the on and off of an IGBT (insulated gate bipolar transistor) tube on a main circuit board of a diode neutral point clamped cascade inverter through a driving board, then a direct-current side bus current sensor and a cascade voltage sensor acquire electric signals of corresponding module characteristic quantities, the electric signals are input into an AD (analog-to-digital) sampling board, the electric signals are input into the FPGA after being processed by the AD sampling board, and a fault state is diagnosed by utilizing a fault characteristic quantity extraction and information fusion algorithm in the FPGA to obtain a final diagnosis result.
The diagnosis results are shown in FIG. 8. The inter-module fault determination rule is as follows: when the phenomenon of 'wave missing' of the direct current side bus current is detected, the signal of the corresponding logic judgment module jumps from 0 to 1, and the corresponding module is indicated to be in fault. The switch tube changes the diagnosis signal from 0 jump to 1 according to each harmonic and phase of the cascade output voltage, namely, the corresponding switch tube is indicated to have a fault. In view of space limitations, FIG. 8 shows the normal failure-free time and S11、S13、S22、S24、S32And (4) diagnosis results in case of failure.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A fault diagnosis method of a single-phase three-level cascade inverter, characterized by comprising:
s1: setting a numbering rule of a switching tube in the single-phase three-level cascade inverter;
s2: numbering the switching tubes of the single-phase three-level cascade inverter according to the numbering rule;
s3: collecting fault sample data of the single-phase three-level cascade inverter;
s4: the method comprises the steps of digitizing fault sample data, determining the positions of a fault module and a specific switch tube by utilizing information fusion, and obtaining different digital character strings;
s5: and obtaining corresponding fault diagnosis results according to the different digital character strings.
2. The fault diagnosis method for the single-phase three-level cascade inverter according to claim 1, wherein the step S2 includes the following substeps:
s21: sequentially labeling the three modules of the single-phase three-level cascade inverter to obtain labels 1, 2 and 3;
s22: sequentially labeling the first bridge arm of each of the three modules from top to bottom to obtain a label Si1、Si2、Si3And Si4；
S23: sequentially labeling the second bridge arm of each of the three modules from top to bottom to obtain a label Si5、Si6、Si7And Si8。
3. The method according to claim 1, wherein in step S3, the method further includes collecting sample data of the single-phase three-level cascade inverter by a current-voltage sensor inside the pass-through power supply system.
4. The fault diagnosis method of the single-phase three-level cascade inverter according to claim 1 or 3, wherein the step S3 includes:
performing inter-module fault detection on three modules of the single-phase three-level cascade inverter to determine a fault module; and/or
And carrying out fault detection on all switching tubes in the fault module, and determining fault switching tubes.
5. The fault diagnosis method for the single-phase three-level cascade inverter according to claim 1, wherein the step S4 includes the following substeps:
s41: determining an encoding rule of the numeric character string;
s42: determining the total digits of the numeric character string and the meaning of each character in the numeric character string according to the encoding rule of the numeric character string;
s43: and according to the fault sample data, obtaining different digital character strings by adopting the step S42.
6. The method according to claim 5, wherein in step S42, the total number of bits of the digital character string is determined to be 7 bits.
7. The method for diagnosing faults of a single-phase three-level cascade inverter according to claim 5, wherein in the step S42, the determining meaning of each character in the digital character string is:
the first three digits of the digital character string represent the module number where the fault module is located in a binary mode, the last four digits of the digital character string represent the number of the fault switch tube in the binary mode, and the digital character string 0000000 represents that no fault occurs.
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| CN114759817A (en) * | 2022-04-07 | 2022-07-15 | 太原理工大学 | Seamless open-circuit fault model prediction fault-tolerant control method suitable for cascaded full-bridge NPC inverter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110208721A (en) * | 2019-07-09 | 2019-09-06 | 西南交通大学 | A kind of method for diagnosing faults and device cascading three-level inverter |
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| CN110208721A (en) * | 2019-07-09 | 2019-09-06 | 西南交通大学 | A kind of method for diagnosing faults and device cascading three-level inverter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114759817A (en) * | 2022-04-07 | 2022-07-15 | 太原理工大学 | Seamless open-circuit fault model prediction fault-tolerant control method suitable for cascaded full-bridge NPC inverter |
| CN114759817B (en) * | 2022-04-07 | 2024-04-12 | 太原理工大学 | Seamless open-circuit fault model prediction fault-tolerant control method suitable for cascading full-bridge NPC inverter |
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