SiC MOSFET characteristic evaluation device and method under DC circuit breaker

Abstract

The invention provides a SiC MOSFET characteristic evaluation device and method under a direct-current circuit breaker, and belongs to the field of MOSFET characteristic evaluation, and the method comprises the steps: carrying out the single turn-off test of a SiC MOSFET under different fault currents under the direct-current circuit breaker through changing the preset voltage value of an external adjustable voltage source, and carrying out the single turn-off test of the SiC MOSFET under different fault currents under the direct-current circuit breaker; obtaining a single-time maximum turn-off current value and a short-time scale single-time turn-off characteristic evaluation result; and fixing a preset voltage value of the external adjustable voltage source, performing a long-time scale repeated turn-off test on the SiC MOSFET under the direct current circuit breaker at a preset time interval, and obtaining a safe operation boundary and a long-time scale repeated turn-off characteristic evaluation result under a long time scale. The characteristic evaluation device established by the invention can completely simulate the operation characteristics of the SiC MOSFET device under the task profile of the direct current circuit breaker, and lays a foundation for safe and reliable operation of the SiC MOSFET device in the direct current circuit breaker.

Description

Technical Field

[0001] The present application belongs to the field of MOSFET characteristic evaluation, and more specifically, to a device and method for evaluating SiC MOSFET characteristics under a DC circuit breaker. Background Art

[0002] In recent years, flexible direct current transmission and direct current grid, which are mainly based on renewable energy such as wind power and photovoltaic power, have developed rapidly. However, when a system fails, due to the low impedance characteristics of the DC grid, the fault current in the circuit will rise sharply in a short time. In severe cases, it may even directly cause the failure of the entire grid. The DC circuit breaker (DCCB) can break strong short-circuit currents within milliseconds and has the ability to reliably and quickly cut off DC fault currents. It is a key device in the DC grid. SiC MOSFET (a metal oxide semiconductor field effect transistor MOSFET made of silicon carbide SiC material) can be used to build DCCB. Compared with silicon, SiC MOSFET has higher breakdown field strength and wider band gap width. In addition, it also has advantages in thermal conductivity and melting point, which is suitable for high temperature scenarios. It is an ideal choice to use SiC MOSFET to build DCCB. However, before SiC MOSFET is used to build DCCB, it is necessary to conduct experimental evaluation and test on the reliability and characteristics of the device. At present, the main method for studying the reliability and characteristic evaluation of SiC MOSFET devices is accelerated power cycle test. Through conventional power cycle experiments, the aging characteristics and failure mechanisms of SiC MOSFET chips can be determined, and the failure causes related to SiC MOSFET packaging can also be discussed. However, this test method does not take into account a special mission profile such as a DC circuit breaker that shuts off several times the rated current in a short period of time. Different mission profiles have their corresponding different specific working conditions, and a specific working condition such as a DC circuit breaker should also have its specific test device and measurement method. Therefore, in order to apply SiC MOSFET to the construction of DCCB, it is necessary to build a SiCMOSFET characteristic evaluation device under a DC circuit breaker and propose a corresponding test method, so as to evaluate and test the reliability and characteristics of SiC MOSFET under DC circuit breaker conditions. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of this application is to provide a device and method for evaluating the characteristics of SiC MOSFET under a DC circuit breaker, aiming to solve the problem that the reliability and characteristic evaluation of existing SiC MOSFET devices does not take into account the special task profile based on the need for DC circuit breakers to shut off several times the rated current in a short period of time, resulting in a blank corresponding test method for SiC MOSFET applied to circuit breakers.

[0004] To achieve the above-mentioned purpose, in a first aspect, the present application provides a device for evaluating the characteristics of a SiC MOSFET under a DC circuit breaker, wherein the SiC MOSFET is used to construct a DC circuit breaker, including: an external adjustable voltage source, a switch, an RLC power loop, an RCD buffer circuit, an MOV clamping circuit, and a drive controller;

[0005] The RLC power circuit, RCD buffer circuit and MOV clamp circuit are connected in parallel; the drive controller is connected to the SiC MOSFET; the SiC MOSFET is connected in series in the RLC power circuit; the switch is set in the circuit formed by the external adjustable voltage source and the capacitor in the RLC power circuit;

[0006] The external adjustable voltage source is used to provide different preset voltage values ​​to charge the capacitor in the RLC power loop; the drive controller is used to control the SiC MOSFET to turn off before charging the capacitor, and to control the SiC MOSFET to turn on after the capacitor is charged; the capacitor in the RLC power loop is used to increase the short-circuit current in the RLC power loop by discharging; the drive controller is used to control the SiC MOSFET to turn off when the short-circuit current reaches the maximum value under the current preset voltage value;

[0007] The RCD snubber circuit is used to suppress the transient voltage overshoot of the SiC MOSFET by current transfer after the SiC MOSFET is turned off; the MOV clamping circuit is used to absorb the energy in the RLC power loop based on the fact that the resistance value decreases and the circuit is in the on state when the voltage across the circuit reaches the operating voltage, and is used to clamp the voltage across the SiC MOSFET at the clamping value.

[0008] Further preferably, the device for evaluating the characteristics of SiC MOSFET under a DC circuit breaker is used to perform a short-time scale characteristic evaluation test and a long-time scale characteristic evaluation test on SiC MOSFET under a DC circuit breaker respectively;

[0009] The short-time scale characteristic evaluation test is to change the preset voltage value of the external adjustable voltage source to achieve the purpose of changing the maximum value of the short-circuit current, and perform a single shutdown test on the SiC MOSFET under different fault currents to obtain the single maximum shutdown current value; wherein, the maximum value of the short-circuit current under the current preset voltage value is taken as the fault current;

[0010] The long time scale characteristic evaluation test is to fix the preset voltage value of the external adjustable voltage source to the preset voltage value of the external adjustable voltage source corresponding to 90% to 95% of the single maximum shutdown current value, and perform long time scale repeated shutdown tests on the SiC MOSFET under a DC circuit breaker at preset time intervals.

[0011] Further preferably, the drive controller is an FPGA development board.

[0012] In the second aspect, the present application provides a corresponding method for evaluating the characteristics of a SiC MOSFET under a DC circuit breaker based on the above-mentioned device for evaluating the characteristics of a SiC MOSFET under a DC circuit breaker, which specifically includes the following steps:

[0013] Step 1: By changing the preset voltage value of the external adjustable voltage source to achieve the purpose of changing the maximum value of the short-circuit current, a single shutdown test is performed on the SiC MOSFET under different fault currents under the DC circuit breaker to obtain the single maximum shutdown current value that the SiC MOSFET can withstand and the short-time scale single shutdown characteristic evaluation result of the SiC MOSFET under the DC circuit breaker; wherein, the maximum value of the short-circuit current under the current preset voltage value is taken as the fault current;

[0014] Step 2: Fix the preset voltage value of the external adjustable voltage source to the preset voltage value of the external adjustable voltage source corresponding to the preset proportion of the single maximum switchable current value, perform long-time scale repeated shutdown test on the SiC MOSFET under the DC circuit breaker at preset time intervals until the SiC MOSFET fails, obtain the safe operation boundary under the long time scale, and compare and evaluate the characteristics of the SiC MOSFET under different test times to obtain the evaluation results of the long-time scale repeated shutdown characteristics of the SiC MOSFET under the DC circuit breaker; wherein, the safe operation boundary under the long time scale is the number of long-time scale repeated shutdown tests that the SiC MOSFET can withstand.

[0015] Further preferably, a shutdown test is performed on the SiC MOSFET under a DC circuit breaker, specifically comprising the following steps:

[0016] At time 0 to t1, the switch is closed, and the capacitor is charged through an external adjustable voltage source, and the charging is completed at time t1;

[0017] At time t1-t2, the switch is turned off, and the drive controller outputs a drive signal to turn on the SiC MOSFET, thereby turning on the RLC power loop. The capacitor is discharged, causing the short-circuit current in the RLC power loop to increase linearly. At time t2, the short-circuit current in the RLC power loop reaches its maximum value, and the SiC MOSFET is turned off by the drive controller.

[0018] At time t2-t3, the MOV clamping circuit is used to clamp the overshoot voltage at both ends of the SiC MOSFET to the clamping voltage; when the current in the MOV clamping circuit becomes zero at time t3, a shutdown test of the SiC MOSFET under the DC circuit breaker is completed;

[0019] Among them, after time t3, the preset voltage value is replaced or a fixed preset voltage value is set to recharge the capacitor, and this is repeated several times to obtain the short-time scale single shutdown characteristic evaluation results and long-time scale repeated shutdown characteristic evaluation results of the SiC MOSFET under the DC circuit breaker.

[0020] Further preferably, in step one, the preset voltage value of the external adjustable voltage source starts from 10V and gradually increases with 10V as the iteration interval. As the preset voltage value continues to increase, the maximum short-circuit current gradually increases until the maximum short-circuit current exceeds the safety boundary of the SiC MOSFET on a short time scale, and the SiC MOSFET fails to shut down; wherein, the safety boundary of the SiC MOSFET on a short time scale is the single maximum shutoff current value that the SiC MOSFET can withstand.

[0021] Further preferably, multiple SiC MOSFETs are selected to repeat step 1 to obtain a short-time scale single turn-off characteristic evaluation result of the SiC MOSFET under a DC circuit breaker.

[0022] Further preferably, the characteristics of the SiC MOSFET in step 2 include a DC circuit breaker turn-off time, a SiC MOSFET drain leakage current, a SiC MOSFET gate threshold voltage and a SiC MOSFET on-resistance.

[0023] Further preferably, in step 2, the preset voltage value of the external adjustable voltage source is fixed to the preset voltage value of the external adjustable voltage source corresponding to 90% to 95% of the single maximum switchable current value.

[0024] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0025] Based on the good performance of SiC MOSFET, this power semiconductor device is suitable for building a DC circuit breaker. In order to evaluate the operating characteristics of SiC MOSFET under the working condition of a DC circuit breaker, a complete SiC MOSFET characteristic evaluation device under a DC circuit breaker is built. The device is based on an RLC charge and discharge circuit, and fully considers the RCD buffer circuit and the MOV clamping circuit to achieve the purpose of transferring fault current and absorbing residual energy of the system. The constructed characteristic evaluation device can completely simulate the operating characteristics of SiC MOSFET under the task profile of the DC circuit breaker, laying the foundation for its safe and reliable operation in the DC circuit breaker.

[0026] Based on the SiC MOSFET characteristic evaluation device under the DC circuit breaker provided in the present application, the characteristic evaluation test of the SiC MOSFET can be performed from two dimensions: a short time scale test method and a long time scale test method. The short time scale test method can determine the safety problem between the stress on the device and the maximum safety boundary, and the long time scale test method can determine the reliability problem of the device's long-term aging failure. Combining the short time scale test results and the long time scale test results, the SiC MOSFET characteristic evaluation test results under the DC circuit breaker can be obtained. The proposed evaluation test method has good practical application effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of a method for evaluating characteristics of SiC MOSFET under a DC circuit breaker provided in an embodiment of the present application;

[0028] Figure 2 1 is a schematic diagram of a device for evaluating characteristics of a SiC MOSFET under a DC circuit breaker provided in an embodiment of the present application;

[0029] Figure 3 : is a test waveform diagram of a SiC MOSFET characteristic evaluation device provided in an embodiment of the present application;

[0030] Figure 4 The embodiment of the present application provides dc =Short-time scale single shutdown test waveform of the device at 50V;

[0031] Figure 5 The embodiment of the present application provides dc =120V device long time scale repeated shutdown with timing test waveform;

[0032] FIG6( a ) is a SiC MOSFET gate threshold voltage aging result on a long time scale provided by an embodiment of the present application;

[0033] FIG6( b ) is a SiC MOSFET on-resistance aging result on a long time scale provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0035] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0036] Next, the technical solutions provided in the embodiments of the present application are introduced.

[0037] like Figure 1 As shown, the present application provides a method for evaluating the characteristics of SiC MOSFET under a DC circuit breaker. In order to obtain the characteristic evaluation of SiC MOSFET under the DCCB task profile, the method specifically includes the following steps:

[0038] Step S1: Build a specific characteristic evaluation device under DC circuit breaker for SiC MOSFET devices:

[0039] like Figure 2 As shown in the figure, a hard switching test is performed on the SiC MOSFET device under test (DUT); the characteristic evaluation device built needs to generate a large current far greater than the rated current of the device within a few milliseconds; for this purpose, the test circuit device schematic diagram is shown in Figure 2 As shown; the device is essentially an RLC charging and discharging circuit. In each test, the SiC MOSFET device is initially in the off state; first, a preset value is set for the external adjustable voltage source, and the voltage source charges the capacitor; the charging process ends when the voltage across the capacitor reaches the preset value; after the charging is completed, the device under test is controlled to turn on by the drive controller; at this time, the power circuit is turned on and the capacitor is discharged; the short-circuit current in the circuit rises linearly, and when the current reaches the maximum value under the preset voltage, the SiC MOSFET will be controlled to turn off by the controller to achieve the purpose of the SiC MOSFET device interrupting the large fault current;

[0040] For low-inductance systems like DC grids, DCCBs need to have the ability to interrupt fault currents within a few milliseconds. The rapid change of current in such a short time will generate overvoltage, which may directly break down the device in severe cases. In addition, the energy stored in the inductor must also be absorbed. Therefore, it is necessary to take some effective measures to suppress the overvoltage during shutdown, and additional absorption circuits are required to absorb the remaining energy in the system.

[0041] Therefore, in order to achieve the above purpose and fully simulate the process of DCCB shutting off the fault current, an RCD snubber circuit and an MOV clamp circuit are connected in parallel at both ends of the device under test to transfer the fault current and absorb the remaining energy in the loop; the RCD snubber circuit can effectively suppress the voltage overshoot of the switch transient and realize the current transfer; MOV (metal oxide varistor) is essentially a variable resistor. Under normal circumstances, its resistance is large and presents a high resistance state; when the voltage across it reaches its MOV operating voltage, the resistance value will decrease and present a conducting state, thereby consuming most of the energy of the circuit and clamping the voltage across the SiCMOSFET at the clamping value to protect the DUT;

[0042] The waveform diagram of the device test is as follows: Figure 3 As shown:

[0043] 0~t1: Close the switch S, first pass the external adjustable voltage source V dc The capacitor C1 is charged and the charging is completed at time t1;

[0044] t1~t2: At t1, the switch S is turned off, and the drive controller gives a drive signal to turn on the device under test, the power circuit is turned on, and the capacitor is discharged through the C1-L-DUT-C1 circuit. The short-circuit current I in the power circuit a It rises linearly;

[0045] t2~t3: At time t2, I a When the voltage reaches the maximum value, the controller turns off the device under test. At the moment of shutdown, the existence of the MOV clamp circuit will cause the overshoot voltage V at both ends of the DUT to ds Clamped to clamp voltage V clamp This protects the device under test; after the device is turned off, I a Transfer to the RCD circuit and MOV circuit in turn, forming I RCD and I MOV ; MOV absorbs most of the remaining energy in the circuit. MOV When the time t3 becomes zero, a test is completed;

[0046] After t3: After one test, the voltage of the capacitor bank will be lower than the preset value and needs to be tested by V dc C1 is charged again for the next test.

[0047] After the test equipment is built, the short-time scale characteristic evaluation test and long-time scale characteristic evaluation test under the DC circuit breaker are carried out on the SiC MOSFET respectively:

[0048] Step S2: For the short-time scale test, the preset voltage value of the external adjustable voltage source is changed to achieve the purpose of changing the maximum value of the DUT shutdown current, so as to perform a single shutdown test on the DUT under different fault currents; the preset voltage value of the external adjustable voltage source starts from 10V and gradually increases with 10V as the iteration interval. As the preset value continues to increase, the current of the SiCMOSFET shutdown also gradually increases until the shutdown current of the device under test exceeds the safety boundary under the short-time scale and the device fails to shut down; in order to reduce the experimental error, it is necessary to select multiple identical devices to repeat the above test steps, and finally obtain the short-time scale single shutdown characteristic evaluation result of the device under test under the DC circuit breaker, and the maximum value of the single shutdown current of the device can be obtained;

[0049] Step S3: For long time scale test, based on the single shutdown characteristic evaluation result obtained under the above short time scale, the preset voltage of the external adjustable voltage source corresponding to 90% to 95% of the single maximum shutdown current value of the device is fixed, and the device under test is subjected to long time scale repeated shutdown test under DC circuit breaker with a time interval of 5 to 10 seconds, and the number of repetitions is until the device fails; with DCCB shutdown time, SiC MOSFET drain leakage current, SiC MOSFET gate threshold voltage and SiC MOSFET on-resistance as reference indicators, the characteristics of the devices under different test times are compared and evaluated, and the safe operation boundary is determined, and finally the long time scale repeated shutdown characteristic evaluation result of the device under test under DC circuit breaker is obtained.

[0050] Example

[0051] Take 1200V / 66A SiC MOSFET as an example to explain:

[0052] For this type of SiC MOSFET, the various components in the device are first selected: the adjustable DC voltage source powers the entire circuit, and the FPGA development board provides drive control signals for the device under test; the selected MOV clamping voltage is 405V; in the power circuit, the capacitor group C1=5mF, the load inductor L=1mH; in the RCD buffer circuit, R=100Ω, C2=5μF, and the diode D model is 1200V / 128A.

[0053] After the test device is built, first conduct a short time scale test, starting from 10V, and increase the preset value V of the external DC voltage source by 10V dc The maximum current in the loop occurs at 3ms, at which point the device under test is controlled to shut off the fault current. Figure 4 V dc =50V as an example, the shutdown waveform of the device under test; Figure 4 It can be seen that before 0ms, the DC voltage source Vdc V ds Charge to the preset value of 50V; at 0ms, the DUT is turned on and the current I in the loop a It rises approximately linearly and reaches the maximum value at 3ms. The device under test is controlled to be turned off at 3ms, and the off current is 48.7A, which is 0.74 times the rated current. After the DUT is turned off, the short-circuit current is transferred through the RCD circuit and the MOV circuit in turn, such as Figure 4 As shown on the right; after 205.5μs transfer time, the current in the loop becomes 0, and the single shutdown experiment ends; Figure 4 As can be seen from the left figure, at the moment of shutdown, the MOV clamps the voltage across the device under test to 344.6V to protect the device under test; Table 1 shows the short-time scale single shutdown characteristic evaluation results of the device under test under the DC circuit breaker obtained by taking 5 devices of the same specification and model and performing 5 repeated single shutdown tests. As can be seen from Table 1, V dc The value of I a It also increased from 9.31A to 131.4A, and the multiples of the maximum shutdown current of the device under test also gradually increased; the maximum current that the DUT can successfully shut down is about 1.99 times the rated current; in addition, the experiment found that under this short time scale test, the cause of SiC MOSFET failure is drain thermal failure.

[0054] Table 1

[0055]

[0056] Based on the short-time scale characteristic evaluation results, a long-time scale test is performed, and the shutdown current of 122.4A (92% of the maximum shutdown current) is taken to correspond to V dc (120V) is fixed and the test is repeated with a time interval of 5s; Figure 5 The shutdown waveform with timeline; before 0ms, V ds Passed V dc Charge to the preset value 120V; at 0ms, DUT is turned on, I a It rises linearly and reaches the maximum value at 3ms. The maximum current passing through the DUT is about 122.4A, which is 1.85 times the rated current. After the DUT is turned off, the current is transferred to the RCD buffer circuit and the MOV clamp circuit. The MOV clamp voltage at the moment of turn-off is 352.8V. Figure 5As shown in Figure 6, the duration of the entire current transfer process after shutdown is 398.4μs. Taking the DCCB shutdown time, drain leakage current, gate threshold voltage and on-resistance as reference indicators, the shutdown times of 0.6k times, 1.3k times and 2k times are selected, and the changes in reference indicators under different test times are compared with the initial values ​​to obtain the long-term characteristic aging results of the device under the DC circuit breaker condition; the long-term test times exceed 2000 times, and the device fails to shut down in the 2004th test, indicating that the safety margin of the device in this case is 2004 times; the cause of device failure is a short-circuit fault between the gate and the source; Figure 6(a) and Figure 6(b) are the aging results under long time scales.

[0057] In summary, compared with the prior art, the present application has the following advantages:

[0058] Based on the good performance of SiC MOSFET, this application makes this kind of power semiconductor device suitable for building a DC circuit breaker; in order to evaluate the operating characteristics of SiC MOSFET under the working condition of a DC circuit breaker, a complete SiC MOSFET characteristic evaluation device under a DC circuit breaker is built. The device is based on an RLC charging and discharging circuit, and fully considers the RCD buffer circuit and the MOV clamping circuit to achieve the purpose of transferring fault current and absorbing residual energy of the system. The constructed characteristic evaluation device can completely simulate the operating characteristics of SiC MOSFET under the task profile of the DC circuit breaker, laying the foundation for its safe and reliable operation in the DC circuit breaker.

[0059] Based on the above test device, the characteristics of SiC MOSFET can be evaluated and tested from two dimensions: short-time scale test method and long-time scale test method. The short-time scale test method can determine the safety problem between the stress on the device and the maximum safety boundary, and the long-time scale test method can determine the reliability problem of long-term aging failure of the device. Combining the short-time scale test results and the long-time scale test results, the SiC MOSFET characteristics evaluation test results under DC circuit breakers can be obtained. The proposed evaluation test method has good practical application effect.

[0060] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A device for evaluating the characteristics of SiC MOSFET under a DC circuit breaker, wherein: SiC MOSFET is used to construct a DC circuit breaker, which is characterized by comprising: an external adjustable voltage source, a switch, an RLC power loop, an RCD snubber circuit, an MOV clamping circuit and a drive controller; The RLC power circuit, RCD buffer circuit and MOV clamp circuit are connected in parallel; the drive controller is connected to the SiC MOSFET; the SiC MOSFET is connected in series in the RLC power circuit; the switch is set in the circuit formed by the external adjustable voltage source and the capacitor in the RLC power circuit; The external adjustable voltage source is used to provide different preset voltage values ​​to charge the capacitor in the RLC power loop; the drive controller is used to control the SiC MOSFET to turn off before charging the capacitor; and control the SiC MOSFET to turn on after the capacitor is charged. The capacitor in the RLC power loop is used to increase the short-circuit current in the RLC power loop by discharging; the drive controller is used to control the SiC MOSFET to turn off when the short-circuit current reaches the maximum value under the current preset voltage value. The RCD snubber circuit is used to suppress the transient voltage overshoot of the SiC MOSFET by current transfer after the SiC MOSFET is turned off; the MOV clamping circuit is used to reduce the resistance value and be in the on state when the voltage across the MOV reaches the operating voltage, thereby absorbing the energy in the RLC power circuit and clamping the voltage across the SiC MOSFET at the clamping value.

2. The device for evaluating the characteristics of SiC MOSFET under a DC circuit breaker according to claim 1, characterized in that: It is used to perform short-time scale characteristic evaluation test and long-time scale characteristic evaluation test of SiC MOSFET under DC circuit breaker respectively; The short-time scale characteristic evaluation test is to change the preset voltage value of the external adjustable voltage source to change the maximum value of the short-circuit current, and perform a single shutdown test on the SiC MOSFET under different fault currents to obtain the single maximum shutdown current value that the SiC MOSFET can withstand; wherein, the maximum value of the short-circuit current under the current preset voltage value is taken as the fault current; The long time scale characteristic evaluation test is to fix the preset voltage value of the external adjustable voltage source to the preset voltage value of the external adjustable voltage source corresponding to 90% to 95% of the single maximum shutdown current value, and perform long time scale repeated shutdown tests on the SiC MOSFET under a DC circuit breaker at preset time intervals.

3. The device for evaluating the characteristics of SiC MOSFET under a DC circuit breaker according to claim 1 or 2, characterized in that: The drive controller is an FPGA development board.

4. A method for evaluating the characteristics of SiC MOSFET under a DC circuit breaker based on the device for evaluating the characteristics of SiC MOSFET under a DC circuit breaker according to any one of claims 1 to 3, characterized in that: The specific steps include: Step 1: By changing the preset voltage value of the external adjustable voltage source to achieve the purpose of changing the maximum value of the short-circuit current, a single shutdown test is performed on the SiC MOSFET under different fault currents under the DC circuit breaker to obtain the single maximum shutdown current value that the SiC MOSFET can withstand and the short-time scale single shutdown characteristic evaluation result of the SiC MOSFET under the DC circuit breaker; wherein, the maximum value of the short-circuit current under the current preset voltage value is taken as the fault current; Step 2: Fix the preset voltage value of the external adjustable voltage source to the preset voltage value of the external adjustable voltage source corresponding to the preset proportion of the single maximum switchable current value, perform long-time scale repeated shutdown test on the SiC MOSFET under the DC circuit breaker at preset time intervals until the SiC MOSFET fails, obtain the safe operation boundary under the long time scale, and compare and evaluate the characteristics of the SiC MOSFET under different test times to obtain the evaluation results of the long-time scale repeated shutdown characteristics of the SiC MOSFET under the DC circuit breaker; wherein, the safe operation boundary under the long time scale is the number of long-time scale repeated shutdown tests that the SiC MOSFET can withstand.

5. The method for evaluating the characteristics of SiC MOSFET under a DC circuit breaker according to claim 4, characterized in that: The shutdown test of SiC MOSFET under DC circuit breaker includes the following steps: At time 0 to t1, the switch is closed, and the capacitor is charged through an external adjustable voltage source, and the charging is completed at time t1; At time t1-t2, the switch is turned off, and the drive controller outputs a drive signal to turn on the SiC MOSFET, thereby turning on the RLC power loop. The capacitor is discharged, causing the short-circuit current in the RLC power loop to increase linearly. At time t2, the short-circuit current in the RLC power loop reaches its maximum value, and the SiC MOSFET is turned off by the drive controller. At time t2-t3, the MOV clamping circuit is used to clamp the overshoot voltage at both ends of the SiC MOSFET to the clamping voltage; when the current in the MOV clamping circuit becomes zero at time t3, a shutdown test of the SiC MOSFET under the DC circuit breaker is completed; Among them, after time t3, the preset voltage value is replaced or a fixed preset voltage value is set to recharge the capacitor, and this is repeated several times to obtain the short-time scale single shutdown characteristic evaluation results and long-time scale repeated shutdown characteristic evaluation results of the SiC MOSFET under the DC circuit breaker.

6. The method for evaluating SiC MOSFET characteristics under a DC circuit breaker according to claim 4 or 5, characterized in that: In step one, the preset voltage value of the external adjustable voltage source starts from 10V and gradually increases with an iteration interval of 10V. As the preset voltage value continues to increase, the maximum short-circuit current gradually increases until the maximum short-circuit current exceeds the safety boundary of the SiC MOSFET in a short time scale, and the SiC MOSFET fails to shut down; wherein, the safety boundary of the SiC MOSFET in a short time scale is the single maximum turn-off current value that the SiC MOSFET can withstand.

7. The method for evaluating the characteristics of SiC MOSFET under a DC circuit breaker according to claim 6, characterized in that: Select multiple SiC MOSFETs and repeat step 1 to obtain the short-time scale single turn-off characteristic evaluation results of SiC MOSFET under the DC circuit breaker.

8. The method for evaluating SiC MOSFET characteristics under a DC circuit breaker according to claim 4, characterized in that: The characteristics of the SiC MOSFET in step 2 include the DC circuit breaker turn-off time, the SiC MOSFET drain leakage current, the SiC MOSFET gate threshold voltage and the SiC MOSFET on-resistance.

9. The method for evaluating SiC MOSFET characteristics under a DC circuit breaker according to claim 4 or 8, characterized in that: In step 2, the preset voltage value of the external adjustable voltage source is fixed to the preset voltage value of the external adjustable voltage source corresponding to 90% to 95% of the single maximum switchable current value.

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