A high-voltage silicon carbide power module internal partial discharge detection system and method

Abstract

The application discloses a kind of high-pressure silicon carbide power module internal partial discharge detection system and method, including broadband light source, optical fiber isolator, optical fiber circulator, single-mode 3x3 optical fiber coupler, delay optical fiber, first single-mode 1x2 optical fiber coupler, optical fiber sensor, second single-mode 1x2 optical fiber coupler, optical power meter, first single-mode optical fiber, second single-mode optical fiber, third single-mode optical fiber, fourth single-mode optical fiber, fifth single-mode optical fiber, sixth single-mode optical fiber, optical fiber adapter, optical fiber adapter, balanced photoelectric detector, analog low-pass filter, data acquisition card and host computer.The application can adjust the size of optical fiber sensor itself for different frequency band partial discharge signals to obtain the detection signal-to-noise ratio that meets the demand;Meanwhile, the application will not be affected by electromagnetic interference, and can be applied in high-pressure field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of partial discharge test of power electronic equipment, and particularly relates to a high-voltage silicon carbide power module internal partial discharge detection system and method based on optical fiber ultrasonic sensing. BACKGROUND

[0002] SiC MOSFET as a wide bandgap power semiconductor device has many advantages compared to traditional silicon devices, such as higher operating temperature, lower on-state loss, higher switching frequency and greater critical breakdown field strength. With the gradual popularization of silicon carbide power devices in the high-voltage field, there is no mature and unified form for the detection method of the insulation reliability of high-voltage silicon carbide power device packaging. The existing electrical insulation partial discharge detection means is established on the basis of low frequency in traditional power grid equipment, and in the face of high switching frequency and internal fast pulse voltage of silicon carbide power device, the traditional partial discharge detection method will be seriously interfered by electromagnetic interference. This field needs to follow up the research and put forward new insulation detection method and evaluation strategy.

[0003] For the pulse current method to measure partial discharge, it is an offline detection method itself, and the measured equipment needs to be separated from the operating condition. At the same time, this method is only suitable for the detection of power frequency partial discharge. Under the operating condition of silicon carbide high-voltage power module, the pulse current method has the following problems that cannot be solved: the coupling capacitor is equivalent to an integral element, which will slow down the voltage rising speed when the power module is turned off; during the voltage to stable period, the coupling capacitor will be fully charged, and then discharged when the voltage drops, which will cause the detected partial discharge pulse current amplitude to be much larger than the normal value; the operating condition of the power module will cause the displacement current of the module insulation system to produce high-frequency capacity, which will affect the screening of the partial discharge signal.

[0004] For the ultra-high frequency method, the electromagnetic wave around the environment is detected to capture the partial discharge signal, but it still cannot solve the problem of electromagnetic interference under the operating condition of high-voltage silicon carbide power module. Further improving the detection frequency band can screen out higher frequency band partial discharge signals, but at the same time the partial discharge signal will become very weak, the overall signal-to-noise ratio is not high, and it will be affected by the communication signal. In addition, the extremely high bandwidth will bring great pressure to sampling and signal processing.

[0005] The traditional piezoelectric ceramic-based ultrasonic sensor is often large in size, and is affected by the packaging shell, which makes it impossible to be applied in the silicon carbide power module with limited space and in high-voltage environment. In addition, although ultrasonic detection will not be affected by electromagnetic interference, the piezoelectric effect will convert mechanical vibration signals into electrical signals, and at this time the electrical signals will be affected by the electromagnetic interference of the high-voltage silicon carbide module and the environment.

[0006] The limitations of the above detection methods are new problems faced by high-voltage silicon carbide power module insulation reliability detection. SUMMARY

[0007] The application aims to provide a high-voltage silicon carbide power module internal partial discharge detection system and method to solve the problem of difficult detection of high-voltage silicon carbide power module partial discharge, and can perform real-time online monitoring on the power module. The application can adjust the size of the optical fiber sensor itself according to different frequency bands of partial discharge signals to obtain a required detection signal-to-noise ratio, and the application will not be affected by electromagnetic interference and can be applied in high-voltage fields.

[0008] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0009] A high-voltage silicon carbide power module internal partial discharge detection system comprises a broadband light source, an optical fiber isolator, an optical fiber circulator, a single-mode 3x3 optical fiber coupler, a delay optical fiber, a first single-mode 1x2 optical fiber coupler, an optical fiber sensor, a second single-mode 1x2 optical fiber coupler, an optical power meter, a first single-mode optical fiber, a second single-mode optical fiber, a third single-mode optical fiber, a fourth single-mode optical fiber, a fifth single-mode optical fiber, a sixth single-mode optical fiber, an optical fiber adapter, an optical fiber adapter, a balanced photoelectric detector, an analog low-pass filter, a data acquisition card, and an upper computer.

[0010] The broadband light source is directly connected with the optical fiber isolator through a single-mode optical fiber; the optical fiber isolator is directly connected with port 1 of the optical fiber circulator through a single-mode optical fiber; port 2 of the optical fiber circulator is directly connected with a second port of one end of the single-mode 3x3 optical fiber coupler through a single-mode optical fiber; a first port of the other end of the single-mode 3x3 optical fiber coupler is connected with one end of the delay optical fiber through the first single-mode optical fiber; the other end of the delay optical fiber is connected with a first port of one end of the first single-mode 1x2 optical fiber coupler through the second single-mode optical fiber; a third port of the other end of the single-mode 3x3 optical fiber coupler is connected with a second port of one end of the first single-mode 1x2 optical fiber coupler through the third single-mode optical fiber; the other end of the first single-mode 1x2 optical fiber coupler is connected with the optical fiber sensor through the fourth single-mode optical fiber; a port of the other end of the optical fiber sensor is connected with one end of the second single-mode 1x2 optical fiber coupler through the fifth single-mode optical fiber; the two ports of the other end of the second single-mode 1x2 optical fiber coupler are connected through the sixth single-mode optical fiber; port 3 of the optical fiber circulator is connected with the optical power meter; a first port of one end of the single-mode 3x3 optical fiber coupler is directly connected with one end of the optical fiber adapter; a third port of one end of the single-mode 3x3 optical fiber coupler is directly connected with one end of the optical fiber adapter; the other end of the optical fiber adapter is connected with an input port of the balanced photoelectric detector through a single-mode optical fiber; the other end of the optical fiber adapter is connected with an input port of the balanced photoelectric detector through a single-mode optical fiber; three output ports of the balanced photoelectric detector are connected with input ports of the analog low-pass filter; three output ports of the analog low-pass filter are connected with the data acquisition card; an output port of the data acquisition card is connected with the upper computer.

[0011] Further, the optical fiber sensor is a bending-resistant single-mode optical fiber with a center wavelength of 1550 nm, which is wound into a circle, and when the radius is 5 mm, the macro-bending loss generated by each coil of the optical fiber is less than 0.10 dB.

[0012] Further, the optical fiber isolator is a double-mode isolator, and the isolation degree is required to be not less than 55 dB.

[0013] Further, the single-mode 3x3 optical fiber coupler is a broadband coupler, and the working bandwidth range is not less than 50 nm, and the splitting ratio of the single-mode 3x3 optical fiber coupler is 1:1:1.

[0014] Further, the first single-mode 1x2 optical fiber coupler and the second single-mode 1x2 optical fiber coupler are broadband couplers, and the working bandwidth range is not less than 50 nm, and the splitting ratio of the first single-mode 1x2 optical fiber coupler and the second single-mode 1x2 optical fiber coupler is 50:50.

[0015] Further, the optical fiber circulator has the following characteristics: the signal input from port 1 can be output from port 2 with low loss, and the signal input from port 2 can be output from port 3 with low loss.

[0016] A method for detecting internal partial discharge of a high-voltage silicon carbide power module, comprising the following steps:

[0017] Step 1: The diameter R of the optical fiber sensor is less than the wavelength λ of the acoustic wave in the internal medium of the power module.

[0018] Step 2: The optical fiber sensor is placed on the surface of the potting glue inside the power module, and the acoustic coupling agent is uniformly applied.

[0019] Step 3: Turn on the broadband light source, the internal partial discharge ultrasonic signal of the power module modulates the light wave passing through the optical fiber sensor, the modulated light wave interferes inside the single-mode 3x3 optical fiber coupler, and the signal containing phase changes is transmitted to the balanced photodetector. The balanced photodetector converts the optical signal containing phase changes into a voltage signal.

[0020] Step 4: The voltage signal output by the balanced photodetector is anti-aliasing filtered by the analog low-pass filter, becoming U1, U2 and U3 three-way signals; U1, U2 and U3 are transmitted to the data acquisition card, and the signal processing algorithm running in the data acquisition card demodulates the original partial discharge ultrasonic signal.

[0021] Step 5: Calculate the peak signal-to-noise ratio of the measured partial discharge ultrasonic signal, draw the power density spectrum, and combine the frequency distribution of the power density spectrum to determine whether the signal-to-noise ratio meets the requirements; if the partial discharge ultrasonic signal near the frequency component f1 is needed and the signal-to-noise ratio does not meet the requirements at this time, the optical fiber sensor is taken out and the test is started again from step 1. Make the optical fiber sensor that meets the frequency f1, and complete the test according to steps 2, 3, 4, and 5.

[0022] Further, the wavelength λ of the acoustic wave in the internal medium of the power module is calculated as follows:

[0023]

[0024] Where f is the frequency of the internal partial discharge ultrasonic signal of the high-voltage power module, and v is the acoustic velocity of the internal medium of the power module.

[0025] Further, the signal processing algorithm runs according to the following formula:

[0026]

[0027]

[0028] Wherein, U1, U2, and U3 are the three signals output by the analog low-pass filter, U PD This is the ultrasonic signal of partial discharge inside the high-voltage power module, U PD The waveform is transmitted to the host computer for display.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention is based on the principle of fiber optic interference, which converts the acoustic signal of partial discharge into a phase change of light waves. Through coherent interference, two coherent light waves interfere with each other within the fiber optic coupler, thereby converting the phase change into a change in optical power amplitude. Through a photodetector and signal demodulation algorithm, the original partial discharge acoustic signal can be recovered, achieving high-sensitivity detection. The sensor size can be freely adjusted according to actual frequency requirements. At the same time, it is completely unaffected by electromagnetic interference. Furthermore, since the optical fiber itself is an insulating material, it fully meets the insulation requirements of high-voltage power modules. Attached Figure Description

[0031] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 This is a schematic diagram of the structure of a high-voltage silicon carbide power module internal partial discharge detection system based on fiber optic ultrasonic sensing according to the present invention.

[0033] Figure 2 This is a schematic diagram of the fiber optic circulator structure selected for this invention;

[0034] Figure 3 This is a schematic diagram illustrating the steps of a method for detecting partial discharge inside a high-voltage silicon carbide power module based on fiber optic ultrasonic sensing, according to the present invention.

[0035] Among them, 1-broadband light source, 2-fiber optic isolator, 3-fiber optic circulator, 4-single-mode 3×3 fiber optic coupler, 5-delay fiber, 6-first single-mode 1×2 fiber optic coupler, 7-fiber optic sensor, 8-second single-mode 1×2 fiber optic coupler, 9-optical power meter, 10-first single-mode fiber, 11-second single-mode fiber, 12-third single-mode fiber, 13-fourth single-mode fiber, 14-fifth single-mode fiber, 15-sixth single-mode fiber, 16-fiber optic adapter, 17-fiber optic adapter, 18-balanced photodetector, 19-analog low-pass filter, 20-data acquisition card, 21-host computer. Detailed Implementation

[0036] In order to better understand the technical scheme of the present application, the technical scheme of the present application will be further described in detail below in conjunction with the accompanying drawings, which are used to explain the present application but not to limit it.

[0037] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of the present application are intended to cover not only the inclusive but also the exclusive, for example, a process, method, system, product, or apparatus that comprises a list of steps or units is not necessarily limited to those steps or units that are clearly listed, but can include other steps or units that are not clearly listed or inherent to such processes, methods, products, or apparatuses.

[0038] As Figure 1 and Figure 2As shown, the high-voltage silicon carbide power module internal partial discharge detection system based on optical fiber ultrasonic sensing designed by the application comprises a broadband light source 1, an optical fiber isolator 2, an optical fiber circulator 3, a single-mode 3x3 optical fiber coupler 4, a delay optical fiber 5, a first single-mode 1x2 optical fiber coupler 6, an optical fiber sensor 7, a second single-mode 1x2 optical fiber coupler 8, an optical power meter 9, a first single-mode optical fiber 10, a second single-mode optical fiber 11, a third single-mode optical fiber 12, a fourth single-mode optical fiber 13, a fifth single-mode optical fiber 14, a sixth single-mode optical fiber 15, an optical fiber adapter 16, an optical fiber adapter 17, a balanced photoelectric detector 18, an analog low-pass filter 19, a data acquisition card 20, and an upper computer 21. The broadband light source 1 is directly connected with the optical fiber isolator 2 through a single-mode optical fiber; the optical fiber isolator 2 is directly connected with a port 1 of the optical fiber circulator 4 through a single-mode optical fiber; a port 2 of the optical fiber circulator 3 is directly connected with a left second port of the single-mode 3x3 optical fiber coupler 4 through a single-mode optical fiber; a right first port of the single-mode 3x3 optical fiber coupler 4 is connected with a left end of the delay optical fiber 5 through the first single-mode optical fiber 10; a right end of the delay optical fiber 5 is connected with a left first port of the first single-mode 1x2 optical fiber coupler 6 through the second single-mode optical fiber 11; a right third port of the single-mode 3x3 optical fiber coupler 4 is connected with a left second port of the first single-mode 1x2 optical fiber coupler 6 through the third single-mode optical fiber 12; a right port of the first single-mode 1x2 optical fiber coupler 6 is connected with the optical fiber sensor 7 through the fourth single-mode optical fiber 13; a right port of the optical fiber sensor 7 is connected with a left end of the second single-mode 1x2 optical fiber coupler 8 through the fifth single-mode optical fiber 14; two ports of a right end of the second single-mode 1x2 optical fiber coupler 8 are connected through the sixth single-mode optical fiber 15; a port 3 of the optical fiber circulator 3 is connected with the optical power meter 9; a left first port of the single-mode 3x3 optical fiber coupler 4 is directly connected with one end of the optical fiber adapter 16 through a single-mode optical fiber; a left third port of the single-mode 3x3 optical fiber coupler 4 is directly connected with one end of the optical fiber adapter 17 through a single-mode optical fiber; the other end of the optical fiber adapter 16 is connected with an input port of the balanced photoelectric detector 18 through a single-mode optical fiber; the other end of the optical fiber adapter 17 is connected with an input port of the balanced photoelectric detector 18 through a single-mode optical fiber; three output ports of the balanced photoelectric detector 18 are connected with input ports of the analog low-pass filter 19; three output ports of the analog low-pass filter 19 are connected with the data acquisition card 20; an output port of the data acquisition card 20 is connected with the upper computer 21.

[0039] The fiber sensor 7 is a bending-resistant single-mode fiber with a center wavelength of 1550 nm, and when the radius is 5 mm, the macro-bending loss of each coil of the fiber is less than 0.10 dB; the fiber isolator 2 is a double-mode isolator, and the isolation degree is required to be not less than 55 dB; the single-mode 3×3 fiber coupler 4 is a broadband coupler, and the working bandwidth range is not less than 50 nm, and the splitting ratio of the single-mode 3×3 fiber coupler 4 is 1:1:1; the first single-mode 1×2 fiber coupler 6 and the second single-mode 1×2 fiber coupler 8 are broadband couplers, and the working bandwidth range is not less than 50 nm, and the splitting ratio of the first single-mode 1×2 fiber coupler 6 and the second single-mode 1×2 fiber coupler 8 is 50:50; the fiber circulator 3 has the following characteristics: the signal input from the port 1 can be output from the port 2 with low loss, and the signal input from the port 2 can be output from the port 3 with low loss.

[0040] As shown in Figure 3 A high-voltage silicon carbide power module internal partial discharge detection method based on fiber ultrasonic sensing, comprising the following steps:

[0041] Step 1: Construct a high-voltage silicon carbide power module internal partial discharge detection system based on fiber ultrasonic sensing, and wind the fiber sensor 7 with a bending-resistant single-mode fiber, compare the diameter R of the fiber sensor 7 with the sound wave wavelength λ of the internal medium of the power module.

[0042] (1.1)

[0043] Where f is the frequency of the high-voltage power module internal partial discharge ultrasonic signal, and v is the sound speed of the internal medium of the power module. Let the diameter R of the fiber sensor 7 be less than the sound wave wavelength λ of the internal medium of the power module.

[0044] Step 2: Place the fiber sensor 7 on the surface of the power module internal potting glue, and evenly apply the acoustic coupling agent;

[0045] Step 3: Turn on the broadband light source 1, and the high-voltage power module internal partial discharge ultrasonic signal will modulate the light wave passing through the fiber sensor 7, the modulated light wave will interfere in the single-mode 3×3 fiber coupler 4, and the signal containing the phase change will be transmitted to the balanced photodetector 18, and the balanced photodetector 18 will convert the optical signal containing the phase change into a voltage signal.

[0046] Step 4: the voltage signal output by the balanced photodetector 18 is subjected to anti-aliasing filtering of the analog low-pass filter 19, and becomes U1, U2 and U3 three-way signals; U1, U2 and U3 are transmitted to the data acquisition card 20, and a signal processing algorithm is run in the data acquisition card 20 to demodulate the original partial discharge ultrasonic signal; the demodulation algorithm is run according to the following formula.

[0047] (1.2)

[0048] (1.3)

[0049] wherein, U PD is the internal partial discharge ultrasonic signal of the high-voltage power module, U PD is transmitted to the host computer 21 for waveform display.

[0050] Step 5: the peak signal-to-noise ratio of the measured partial discharge ultrasonic signal is calculated, and the power density spectrum is drawn; the frequency distribution of the power density spectrum is combined to determine whether the signal-to-noise ratio meets the requirements. If the partial discharge ultrasonic signal near the frequency component f1 is needed and the signal-to-noise ratio at this time does not meet the requirements, the optical fiber sensor 7 needs to be taken out and the test is restarted from step 1, the optical fiber sensor 7 meeting the frequency f1 is made, and steps 2, 3, 4 and 5 are completed again.

[0051] From the common technical knowledge, the application can be realized by other embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above disclosed embodiments are only examples and are not the only ones. All changes within the scope of the application or within the scope equivalent to the application are included in the application.

Claims

1. A method for detecting partial discharge inside a high-voltage silicon carbide power module, based on a system for detecting partial discharge inside a high-voltage silicon carbide power module, characterized in that, The internal partial discharge detection system of the high-voltage silicon carbide power module based on a wideband light source (1), an optical fiber isolator (2), an optical fiber ring (3), a single-mode 3x3 optical fiber coupler (4), a delay optical fiber (5), a first single-mode 1x2 optical fiber coupler (6), an optical fiber sensor (7), a second single-mode 1x2 optical fiber coupler (8), an optical power meter (9), a first single-mode optical fiber (10), a second single-mode optical fiber (11), a third single-mode optical fiber (12), a fourth single-mode optical fiber (13), a fifth single-mode optical fiber (14), a sixth single-mode optical fiber (15), an optical fiber adapter (16), an optical fiber adapter (17), a balanced photodetector (18), an analog low-pass filter (19), a data acquisition card (20), and a host computer (21); The wideband light source (1) is directly connected to the optical fiber isolator (2) through a single-mode optical fiber; the optical fiber isolator (2) is directly connected to port 1 of the optical fiber ring (3) through a single-mode optical fiber; port 2 of the optical fiber ring (3) is directly connected to a second port of one end of the single-mode 3x3 optical fiber coupler (4) through a single-mode optical fiber; a first port of the other end of the single-mode 3x3 optical fiber coupler (4) is connected to one end of the delay optical fiber (5) through the first single-mode optical fiber (10); the other end of the delay optical fiber (5) is connected to a first port of one end of the first single-mode 1x2 optical fiber coupler (6) through the second single-mode optical fiber (11); a third port of the other end of the single-mode 3x3 optical fiber coupler (4) is connected to a second port of one end of the first single-mode 1x2 optical fiber coupler (6) through the third single-mode optical fiber (12); a port of the other end of the first single-mode 1x2 optical fiber coupler (6) is connected to the optical fiber sensor (7) through the fourth single-mode optical fiber (13); a port of the other end of the optical fiber sensor (7) is connected to one end of the second single-mode 1x2 optical fiber coupler (8) through the fifth single-mode optical fiber (14); the two ports of the other end of the second single-mode 1x2 optical fiber coupler (8) are connected through the sixth single-mode optical fiber (15); port 3 of the optical fiber ring (3) is connected to the optical power meter (9); a first port of one end of the single-mode 3x3 optical fiber coupler (4) is directly connected to one end of the optical fiber adapter (16) through a single-mode optical fiber; a third port of one end of the single-mode 3x3 optical fiber coupler (4) is directly connected to one end of the optical fiber adapter (17) through a single-mode optical fiber; the other end of the optical fiber adapter (16) is connected to the input port of the balanced photodetector (18) through a single-mode optical fiber; the other end of the optical fiber adapter (17) is connected to the input port of the balanced photodetector (18) through a single-mode optical fiber; the three output ports of the balanced photodetector (18) are connected to the input port of the analog low-pass filter (19); the three output ports of the analog low-pass filter (19) are connected to the data acquisition card (20); the output port of the data acquisition card (20) is connected to the host computer (21); The internal partial discharge detection method of the high-voltage silicon carbide power module comprises the following steps: Step 1: The diameter R of the optical fiber sensor (7) is less than the sound wave wavelength λ of the internal medium of the power module; Step 2: The optical fiber sensor (7) is placed on the surface of the potting glue inside the power module, and the acoustic coupling agent is uniformly applied; Step 3: Turn on the broadband light source (1), the internal partial discharge ultrasonic signal of the power module modulates the light wave passing through the optical fiber sensor (7), the modulated light wave interferes in the single-mode 3×3 optical fiber coupler (4), and the signal containing the phase change is transmitted to the balanced photodetector (18), the balanced photodetector (18) converts the optical signal containing the phase change into a voltage signal; Step 4: The voltage signal output by the balanced photodetector (18) is anti-aliasing filtered by the analog low-pass filter (19) and becomes U1, U2 and U3 three-way signals; U1, U2 and U3 are transmitted to the data acquisition card (20), and the signal processing algorithm running in the data acquisition card (20) demodulates the original partial discharge ultrasonic signal; the signal processing algorithm runs according to the following formula: Wherein, U1, U2 and U3 are three signals output by the analog low-pass filter (19) respectively, U PD Is the partial discharge ultrasonic signal inside the high-voltage power module, U PD Transmitted to the host computer (21) for waveform display; Step 5: Calculate the peak signal-to-noise ratio of the measured partial discharge ultrasonic signal, draw the power density spectrum, and judge whether the signal-to-noise ratio meets the requirements according to the frequency distribution of the power density spectrum; if the partial discharge ultrasonic signal near the frequency component f1 is needed and the signal-to-noise ratio at this time does not meet the requirements, the optical fiber sensor (7) is taken out and the test is started again from step 1, the optical fiber sensor (7) meeting the frequency f1 is made, and steps 2, 3, 4 and 5 are completed again.

2. The method according to claim 1, wherein The sound wave wavelength λ of the internal medium of the power module is calculated as follows: Wherein, f is the frequency of the internal partial discharge ultrasonic signal of the high-voltage power module, and v is the sound velocity of the internal medium of the power module.

3. The method according to claim 1, wherein The optical fiber sensor (7) is a bending-resistant single-mode optical fiber with a center wavelength of 1550nm, which is wound into a circle. When the radius is 5mm, the macro-bending loss of each coil of optical fiber is less than 0.10dB.

4. The method for detecting internal partial discharge of a high-voltage silicon carbide power module according to claim 1, characterized in that, The optical fiber isolator (2) is a double-mode isolator with an isolation degree not less than 55dB.

5. The method for detecting internal partial discharge of a high-voltage silicon carbide power module according to claim 1, characterized in that, The single-mode 3×3 optical fiber coupler (4) is a broadband coupler with a working bandwidth range not less than 50nm, and the splitting ratio of the single-mode 3×3 optical fiber coupler (4) is 1:1:

1.

6. The method for detecting internal partial discharge of a high-voltage silicon carbide power module according to claim 1, wherein The first single-mode 1×2 optical fiber coupler (6) and the second single-mode 1×2 optical fiber coupler (8) are broadband couplers with a working bandwidth range not less than 50nm, and the splitting ratio of the first single-mode 1×2 optical fiber coupler (6) and the second single-mode 1×2 optical fiber coupler (8) is 50:

50.

7. The method for detecting internal partial discharge of a high-voltage silicon carbide power module according to claim 1, characterized in that, The optical fiber circulator (3) has the following characteristics: the signal input from port 1 can be output from port 2 with low loss, and the signal input from port 2 can be output from port 3 with low loss.

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