Cascade five-level inverter with igbt open-circuit fault diagnosis

Abstract

The application provides a cascaded five-level inverter with IGBT open-circuit fault diagnosis, which has the characteristics of comprising a five-level inverter circuit module, three five-level inverters, a five-level inverter composed of two H-bridge sub-modules, an H-bridge sub-module comprising a full-bridge structure and a parallel capacitor, a detection module comprising a plurality of voltage sensors, output phase voltage waveforms of the five-level inverter and voltage waveforms across the diodes, a fault diagnosis module for judging whether the five-level inverter has an open-circuit fault according to total harmonic distortion of the output phase voltage waveforms, comparing the output phase voltage waveforms with output phase voltage waveforms of the five-level inverter under normal working conditions, determining the H-bridge sub-module having the open-circuit fault, and determining the diode having the open-circuit fault according to total harmonic distortion of the diode voltage waveforms. In summary, the cascaded five-level inverter can more accurately and quickly diagnose the IGBT device having the open-circuit fault.

Description

Technical Field

[0001] This invention relates to fault diagnosis of switching devices in a five-level inverter circuit, specifically to a cascaded five-level inverter with IGBT open-circuit fault diagnosis. Background Technology

[0002] In the field of high-voltage, high-power inverters, traditional two-level voltage-type inverters can no longer meet the requirements for voltage and power. Multilevel inverters, by increasing the number of output voltage levels, can solve this problem. Compared to traditional two-level voltage-type inverters, multilevel inverters have a better harmonic spectrum in their output voltage waveform, and the voltage stress on the switching devices is relatively lower. However, correspondingly, due to the use of more switching devices, the reliability of the entire inverter topology decreases. Failure of the inverter's switching devices may cause the inverter to stop working, affecting the stability of the entire inverter circuit. To reduce downtime caused by switching devices and improve the reliability of the inverter circuit, employing precise switching device fault detection methods for fault diagnosis of multilevel inverter circuits can improve the reliability of the inverter system and reduce the risk of secondary faults.

[0003] In recent years, researchers have proposed many fault diagnosis methods for switching devices in inverter circuits, which can be broadly classified into two categories: current-based methods and voltage-based methods. Current-based methods use the system current as the detection value to determine whether the system current is abnormal, thereby diagnosing the fault condition of the switching devices. Voltage-based methods use the system voltage as the detection value, judging whether the switching devices are faulty by analyzing the system's output voltage waveform. Voltage-based methods can shorten the diagnosis time and avoid the influence of current distortion on the diagnosis of switching devices. However, existing voltage-based fault diagnosis methods suffer from slow diagnosis speed and low reliability of diagnostic results. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a cascaded five-level inverter with IGBT open-circuit fault diagnosis.

[0005] This invention provides a cascaded five-level inverter with IGBT open-circuit fault diagnosis, characterized by the following features: a five-level inverter circuit module comprising three five-level inverters, each five-level inverter consisting of two H-bridge sub-modules, the output terminal of one H-bridge module being connected to the input terminal of the other H-bridge module; an H-bridge module comprising a full-bridge structure consisting of four IGBT devices connected in anti-parallel to four diodes and a parallel capacitor; and a detection module comprising multiple voltage sensors connected in parallel with the five-level inverters to acquire the output phase voltage waveform of the five-level inverters, the voltage sensors being connected in parallel with the diodes to acquire... The voltage waveform across the diode is used as the diode voltage waveform. The fault diagnosis module performs a fast Fourier transform analysis on the output phase voltage waveform and, combined with the fundamental frequency of the cascaded five-level inverter circuit module, obtains the total harmonic distortion (THD) of the output phase voltage waveform. Based on the THD of the output phase voltage waveform, it determines whether the five-level inverter has an open-circuit fault. If the five-level inverter has an open-circuit fault, it compares the output phase voltage waveform with the output phase voltage waveform of the five-level inverter under normal operation to determine the H-bridge sub-module with the open-circuit fault. Based on the THD of the diode voltage waveform, it determines the diode with the open-circuit fault.

[0006] The cascaded five-level inverter with IGBT open-circuit fault diagnosis provided by this invention may also have the following feature: wherein the total harmonic distortion calculation formula is as follows: In the formula, THD represents total harmonic distortion, U1 is the fundamental component, and U2, U3...U n These are harmonic components of different frequencies.

[0007] The cascaded five-level inverter with IGBT open-circuit fault diagnosis provided by this invention may also have the following features: the process of determining whether the five-level inverter has an open-circuit fault based on the total harmonic distortion is as follows: when the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the output phase voltage waveform is less than 20%, then the five-level inverter has not experienced an open-circuit fault; if the total harmonic distortion of the output phase voltage waveform is greater than 20% and less than 40%, then one IGBT device of the five-level inverter has experienced an open-circuit fault; if the total harmonic distortion of the output phase voltage waveform is greater than 40%, then two IGBT devices of the five-level inverter have experienced open-circuit faults.

[0008] In the cascaded five-level inverter with IGBT open-circuit fault diagnosis provided by the present invention, it may also have the following feature: wherein the process of determining the diode that has an open-circuit fault is as follows: when the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the diode voltage waveform is greater than 130%, then the diode has an open-circuit fault.

[0009] In the cascaded five-level inverter with IGBT open-circuit fault diagnosis provided by the present invention, it may also have the following feature: In one H-bridge submodule, a voltage sensor is connected in parallel with two diodes of the upper half-bridge or lower half-bridge of the H-bridge submodule, and the voltage waveform of the diode is collected as the diode voltage waveform. If one IGBT device of the H-bridge submodule has an open-circuit fault, and the total harmonic distortion of the voltage waveforms of the two diodes of the H-bridge submodule is less than 130%, then the IGBT device in operation corresponding to the diode voltage waveform has not had an open-circuit fault, and it is determined that the other IGBT device in operation has an open-circuit fault.

[0010] The role and effect of invention

[0011] According to the cascaded five-level inverter with IGBT open-circuit fault diagnosis of the present invention, since the open-circuit fault of the five-level inverter is determined by measuring the output phase voltage waveform of the single-phase five-level inverter and calculating the total harmonic distortion, the H-bridge sub-module with open-circuit fault is identified by measuring the output phase voltage waveform, and the diode with open-circuit fault is identified by measuring the voltage waveform across the diode and calculating the total harmonic distortion, the cascaded five-level inverter with IGBT open-circuit fault diagnosis of the present invention can more accurately and quickly diagnose the IGBT device with open-circuit fault. Attached Figure Description

[0012] Figure 1 This is a system structure diagram of the cascaded five-level inverter circuit in an embodiment of the present invention;

[0013] Figure 2 This is a schematic diagram of a five-level inverter in an embodiment of the present invention;

[0014] Figure 3 This is a schematic diagram of the fast Fourier transform analysis and total harmonic distortion of the output phase voltage waveform of a five-level inverter when a single tube fails in an embodiment of the present invention.

[0015] Figure 4 This is a schematic diagram of the fast Fourier transform analysis and total harmonic distortion of the output phase voltage waveform of a five-level inverter under dual-transistor fault in an embodiment of the present invention.

[0016] Figure 5 This is a schematic diagram of the output phase voltage waveform of a five-level inverter under normal operation in an embodiment of the present invention;

[0017] Figure 6 This is a schematic diagram of the output phase voltage waveform when a single IGBT device open-circuit fault occurs in an H-bridge submodule of a five-level inverter in an embodiment of the present invention;

[0018] Figure 7This is a schematic diagram of the output phase voltage waveform when a single IGBT device open-circuit fault occurs in another H-bridge submodule of the five-level inverter in an embodiment of the present invention;

[0019] Figure 8 This is a schematic diagram of the output phase voltage waveforms of the two H-bridge sub-modules of the five-level inverter in an embodiment of the present invention when a single IGBT device experiences an open-circuit fault.

[0020] Figure 9 This is a schematic diagram of the output phase voltage waveform when two IGBT devices in one H-bridge submodule of the five-level inverter in an embodiment of the present invention experience an open-circuit fault.

[0021] Figure 10 This is a schematic diagram of the output phase voltage waveform when two IGBT devices in another H-bridge submodule of the five-level inverter in an embodiment of the present invention experience an open-circuit fault. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, provide a detailed description of the cascaded five-level inverter with IGBT open-circuit fault diagnosis of the present invention.

[0023] Figure 1 This is a system structure diagram of a cascaded five-level inverter circuit in an embodiment of the present invention.

[0024] like Figure 1 As shown, the cascaded five-level inverter circuit includes: a five-level inverter circuit module, i.e., a five-level inverter IC. A IC B and IC C The detection module is the detection module M. A M B and M C The fault diagnosis module is also known as the fault diagnosis module FD. A FD B and FD C The modulation module is the modulation circuit D. A D B and D C and load module, i.e., load L A L B and L C Three five-level inverter ICs A IC B and IC C Each of the three corresponding detection modules M A M B and M C Three modulation circuits D A D B and DC and three loads L A L B and L C Connected, three fault diagnosis modules FD A FD B and FD C Each with the corresponding detection module M A M B and M C Connected.

[0025] Figure 2 This is a schematic diagram of a five-level inverter in an embodiment of the present invention.

[0026] like Figure 2 As shown, the five-level inverter consists of two H-bridge submodules, with the output of one submodule connected to the input of the other. Each H-bridge submodule includes four IGBT devices VT1, VT2, VT3, and VT4 connected in anti-parallel to form a full-bridge structure with four diodes VD1, VD2, VD3, and VD4, and a parallel capacitor C. In this embodiment, the DC source E is connected in parallel with the H-bridge submodule as the input power supply for the cascaded five-level inverter. The five-level inverter generates AC power for the corresponding load L. A L B and L C In this embodiment, the IGBT device used is the FF450R17ME3 device manufactured by Infineon Technologies.

[0027] Modulation circuit D A D B and D C The modulation method employed is carrier in-phase stacked modulation, which consists of four triangular carriers with the same amplitude and frequency symmetrically distributed in the vertical direction of the sinusoidal modulating wave. These carriers are compared layer by layer with the modulating wave to control the corresponding five-level inverter IC. A IC B and IC C The H-bridge submodule in the middle outputs different levels, as follows:

[0028] When the sinusoidal modulation wave is greater than the positive triangular carrier wave, the IGBT device VT1 of the H-bridge submodule is turned on and the IGBT device VT3 is turned off.

[0029] When the sinusoidal modulation wave is smaller than the positive triangular carrier wave, the IGBT device VT1 of the H-bridge submodule is turned off and the IGBT device VT3 is turned on.

[0030] When the sinusoidal modulated wave is greater than the negative triangular carrier wave, the IGBT device VT2 of the H-bridge submodule is turned off and the IGBT device VT4 is turned on.

[0031] When the sinusoidal modulated wave is less than the negative triangular carrier wave, the IGBT device VT2 of the H-bridge submodule is turned on and the IGBT device VT4 is turned off.

[0032] Each H-bridge submodule can output three voltage levels: -Vdc, 0, and +Vdc, as detailed below:

[0033] When IGBT devices VT1 and VT4 of the H-bridge module are turned on simultaneously, and IGBT devices VT2 and VT3 are turned off, the output voltage of the H-bridge module is +Vdc.

[0034] When IGBT devices VT2 and VT3 of the H-bridge submodule are turned on simultaneously, and IGBT devices VT1 and VT4 are turned off, the output voltage of the H-bridge submodule is -Vdc.

[0035] When IGBT devices VT1 and VT3 of the H-bridge submodule are simultaneously turned on, and IGBT devices VT2 and VT4 are turned off, or when IGBT devices VT2 and VT4 are simultaneously turned on, and IGBT devices VT1 and VT3 are turned off, the H-bridge output voltage is 0. Therefore, the five-level inverter IC formed by cascading two H-bridge submodules is... A IC B and IC C It can output five voltage levels: -2Vdc, -Vdc, 0, Vdc, and 2Vdc.

[0036] In this embodiment, the modulation circuit includes a field-programmable gate array (FPGA) chip and a digital signal processor (DSP). The FPGA chip obtains the modulation signal from the DSP, then compares it with the triangular carrier wave to generate a drive signal, which in turn drives the IGBT device in the corresponding five-level inverter. The FPGA chip is a Xilinx XC3S400-4PQG208C chip, and the DSP is a Texas Instruments TMS320F28335 chip.

[0037] Detection module M A M B and M C It includes multiple voltage sensors, with each detection module's voltage sensor connected in parallel with its corresponding five-level inverter, and collecting data from the five-level inverter IC. A IC B and IC CThe output phase voltage waveform is obtained. The voltage sensor of each detection module is also connected in parallel with the diode of each H-bridge submodule of the corresponding five-level inverter to collect the voltage waveform across the diode as the diode voltage waveform. In this embodiment, the voltage sensor is the AV100-2000 voltage sensor manufactured by LEM.

[0038] Fault Diagnosis Module FD A FD B and FD C For the corresponding detection module M, respectively A M B and M C The acquired output phase voltage waveform is analyzed using Fast Fourier Transform (FFT). Combined with the fundamental frequency of the cascaded five-level inverter circuit module, the total harmonic distortion (THD) of the output voltage waveform is obtained. The formula for calculating the THD is as follows:

[0039]

[0040] In the formula, THD represents total harmonic distortion, U1 is the fundamental component, and U2, U3...U n These are harmonic components of different frequencies.

[0041] Determining whether a five-level inverter has an open-circuit fault based on the total harmonic distortion (THD) of the output voltage waveform is as follows:

[0042] When the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the output phase voltage waveform is less than 20%, then the five-level inverter has not experienced an open circuit fault.

[0043] If the total harmonic distortion of the output phase voltage waveform is greater than 20% and less than 40%, then one IGBT device of the five-level inverter will have an open-circuit fault.

[0044] If the total harmonic distortion of the output phase voltage waveform is greater than 40%, then the two IGBT devices of the five-level inverter will experience an open-circuit fault.

[0045] Figure 3 This is a schematic diagram of the fast Fourier transform analysis and total harmonic distortion of the output voltage waveform of a five-level inverter when a single tube fails, according to an embodiment of the present invention.

[0046] like Figure 3 As shown, the horizontal axis represents the frequency of the harmonic components of the output voltage waveform, and the vertical axis represents the percentage of the harmonic component amplitude relative to the fundamental frequency, i.e., Mag. The measured amplitude of the harmonic component at the fundamental frequency is 295.8. Therefore, the calculated total harmonic distortion (THD) is 37.46%, indicating that a single transistor fault has occurred in the five-level inverter.

[0047] Figure 4 This is a schematic diagram of the fast Fourier transform analysis and total harmonic distortion of the output phase voltage waveform of a five-level inverter under a dual-transistor fault in an embodiment of the present invention.

[0048] like Figure 4 As shown, the horizontal axis represents the frequency of the harmonic components of the output phase voltage waveform, and the vertical axis represents the percentage of the harmonic component amplitude relative to the fundamental frequency, i.e., Mag. The measured amplitude of the harmonic component at the fundamental frequency is 165.3. Therefore, the calculated total harmonic distortion (THD) is 70.61%, indicating that the five-level inverter has a dual-transistor fault.

[0049] Figure 5 This is a schematic diagram of the output phase voltage waveform of a five-level inverter under normal operating conditions in an embodiment of the present invention. Figure 6 This is a schematic diagram of the output phase voltage waveform when a single IGBT device in an H-bridge submodule of a five-level inverter experiences an open-circuit fault in an embodiment of the present invention. Figure 7 This is a schematic diagram of the output phase voltage waveform when a single IGBT device open-circuit fault occurs in another H-bridge submodule of the five-level inverter in an embodiment of the present invention. Figure 8 This is a schematic diagram of the output phase voltage waveforms of the five-level inverter in an embodiment of the present invention when a single IGBT device in each of the two H-bridge submodules experiences an open-circuit fault. Figure 9 This is a schematic diagram of the output phase voltage waveform when two IGBT devices in one H-bridge submodule of a five-level inverter experience an open-circuit fault in an embodiment of the present invention. Figure 10 This is a schematic diagram of the output phase voltage waveform when two IGBT devices in another H-bridge submodule of the five-level inverter in an embodiment of the present invention experience an open-circuit fault. Figures 5 to 10 The horizontal axis represents time, and the vertical axis represents the amplitude of the output phase voltage.

[0050] like Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 As shown, when a single IGBT device in a single H-bridge submodule experiences an open-circuit fault, the output voltage waveform of that H-bridge submodule is distorted. Therefore, when different H-bridge submodules experience open-circuit faults and different numbers of IGBT devices experience open-circuit faults, the corresponding output phase voltage waveforms of the five-level inverter will experience different distortions. If the five-level inverter experiences an open-circuit fault, the output phase voltage waveform is compared with the output voltage waveform of the five-level inverter under normal operation to determine the H-bridge submodule that experienced the open-circuit fault.

[0051] The diode with an open-circuit fault is determined based on the total harmonic distortion of the diode voltage waveform. The process for determining the diode with an open-circuit fault is as follows:

[0052] When the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the diode voltage waveform is greater than 130%, the diode will have an open circuit fault.

[0053] In one H-bridge submodule, a voltage sensor is connected in parallel with two diodes VT1 and VT2 in the upper half-bridge or two diodes VT3 and VT4 in the lower half-bridge of the H-bridge submodule, respectively, to collect the diode voltage waveforms as diode voltage waveforms. If one IGBT device in the H-bridge submodule experiences an open-circuit fault, and the total harmonic distortion of the voltage waveforms of both diodes in the H-bridge submodule is less than 130%, then the IGBT device in operation corresponding to the diode voltage waveform has not experienced an open-circuit fault, and it is determined that the other IGBT device in operation has experienced an open-circuit fault.

[0054] The role and effect of the embodiments

[0055] According to the cascaded five-level inverter with IGBT open-circuit fault diagnosis involved in this embodiment, by measuring the output phase voltage waveform of a single-phase five-level inverter and calculating the total harmonic distortion (THD), it is determined whether the five-level inverter has an open-circuit fault. The H-bridge sub-module with the open-circuit fault is identified by measuring the output phase voltage waveform, and the diode with the open-circuit fault is determined by measuring the voltage waveform across the diode and calculating the THD. In summary, this cascaded five-level inverter can more accurately and quickly diagnose IGBT devices with open-circuit faults.

[0056] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A cascaded five-level inverter with IGBT open-circuit fault diagnosis, characterized in that, include: A five-level inverter circuit module includes three five-level inverters, each of which is composed of two H-bridge sub-modules, with the output terminal of one H-bridge sub-module connected to the input terminal of the other H-bridge sub-module. The H-bridge submodule includes a full-bridge structure consisting of four IGBT devices connected in anti-parallel to four diodes and a parallel capacitor; The detection module includes multiple voltage sensors, which are connected in parallel with the five-level inverter to collect the output phase voltage waveform of the five-level inverter. The voltage sensors are also connected in parallel with the diode to collect the voltage waveform across the diode as the diode voltage waveform. The fault diagnosis module performs a Fast Fourier Transform analysis on the output phase voltage waveform and, in conjunction with the fundamental frequency of the five-level inverter circuit module, obtains the total harmonic distortion (THD) of the output phase voltage waveform. Based on the THD of the output phase voltage waveform, it determines whether the five-level inverter has an open-circuit fault. If the five-level inverter has an open-circuit fault, it compares the output phase voltage waveform with the output phase voltage waveform of the five-level inverter under normal operation to identify the H-bridge sub-module with the open-circuit fault. Based on the THD of the diode voltage waveform, it identifies the diode with the open-circuit fault.

2. The cascaded five-level inverter with IGBT open-circuit fault diagnosis according to claim 1, characterized in that: in, The formula for calculating total harmonic distortion is as follows: ， In the formula For total harmonic distortion, For the fundamental component, These are harmonic components of different frequencies.

3. The cascaded five-level inverter with IGBT open-circuit fault diagnosis according to claim 1, characterized in that: in, The process of determining whether the five-level inverter has an open-circuit fault based on the total harmonic distortion is as follows: When the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the output phase voltage waveform is less than 20%, then the five-level inverter has not experienced an open-circuit fault. If the total harmonic distortion of the output phase voltage waveform is greater than 20% and less than 40%, then one of the IGBT devices in the five-level inverter has an open-circuit fault. If the total harmonic distortion of the output phase voltage waveform is greater than 40%, then the two IGBT devices of the five-level inverter have an open-circuit fault.

4. The cascaded five-level inverter with IGBT open-circuit fault diagnosis according to claim 1, characterized in that: in, The process of determining the diode that has an open-circuit fault is as follows: When the fundamental frequency is 50Hz and the maximum harmonic detection frequency is 1000Hz, if the total harmonic distortion of the diode voltage waveform is greater than 130%, the diode will have an open circuit fault.

5. The cascaded five-level inverter with IGBT open-circuit fault diagnosis according to claim 4, characterized in that: in, In one of the H-bridge submodules, the voltage sensor is connected in parallel with two diodes in the upper or lower half-bridge of the H-bridge submodule, respectively, to collect the voltage waveform of the diodes as the diode voltage waveform. If one of the IGBT devices in the H-bridge submodule experiences an open-circuit fault, and the total harmonic distortion of the voltage waveforms of both diodes in the H-bridge submodule is less than 130%, then the IGBT device in operation corresponding to the diode voltage waveform does not experience an open-circuit fault, and it is determined that the other IGBT device in operation experiences an open-circuit fault.

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