A thyristor junction temperature online detection system and detection method

Abstract

The present invention discloses an online thyristor junction temperature detection system and method. The system comprises a main circuit unit connected to the thyristor and configured to provide the thyristor with a DC bus voltage and conduction current; a drive unit connected to the thyristor and configured to control the conduction process of the thyristor; a temperature control unit configured to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation; a sampling unit connected to the main circuit unit and the temperature control unit; and a junction temperature detection unit storing a database and a function model, connected to the sampling unit, the drive unit, and the thyristor. The sampling unit collects the thyristor's DC bus voltage, thyristor conduction current, and drive current, while the junction temperature detection unit collects the thyristor's gate voltage. The thyristor's operating junction temperature is obtained by inverse calculation using the above parameters by querying the database or the function model. The present invention can detect the thyristor's operating junction temperature in real time with high accuracy and resolution.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic device detection, and in particular to an online detection system and method for thyristor junction temperature. Background Art

[0002] Thyristors are currently the power electronic devices with the highest voltage resistance and largest output capacity. They have both forward and reverse voltage blocking capabilities and are widely used in the field of flexible HVDC transmission. They are the core components in HVDC transmission projects. In current large-capacity HVDC transmission projects, most use thyristor commutator valves.

[0003] According to industry surveys, the failure rate of power semiconductor devices in power converter systems is as high as 21%. Analysis of the causes of these failures revealed that temperature-related failures account for 55% of these failures. In power electronics, the operating junction temperature of power devices is the most critical parameter. For every 10°C increase in junction temperature, the device's service life is halved. Therefore, online monitoring of thyristor junction temperature is crucial for thyristor converter valves and the entire HVDC transmission system.

[0004] High-voltage, high-capacity thyristors typically utilize a press-fit package. Due to their unique packaging structure, current methods for monitoring their junction temperature primarily include infrared thermometers, thermal impedance models, and mathematical calculations. The infrared thermometer method suffers from significant measurement errors, providing only a rough estimate of the thyristor's junction temperature and failing to accurately measure the junction temperature for overload capacity analysis. The thermal impedance model method is challenging due to the need to accurately establish a thermal network model for the thyristor. Furthermore, errors in the thermal network model or case temperature measurement can lead to significant deviations between the calculated junction temperature and the actual value. The mathematical calculation method, based on the fundamental laws of heat transfer in thermal engineering, calculates the thyristor's junction temperature. While highly accurate, it is complex and costly. High-voltage, high-capacity thyristors often operate under high voltage and high current conditions, placing high demands on online detection technology. Therefore, achieving online detection of the operating junction temperature of high-voltage, high-capacity thyristors presents a significant challenge. Summary of the Invention

[0005] The purpose of the present invention is to provide a thyristor junction temperature online detection system and detection method. The present invention can detect the thyristor operating junction temperature in real time with high accuracy and resolution.

[0006] The technical solution of the present invention is: a thyristor junction temperature online detection system, comprising a main circuit unit connected to the thyristor, for providing a DC bus voltage and a conduction current for the thyristor;

[0007] A driving unit, connected to the thyristor, is used to control the conduction process of the thyristor;

[0008] Temperature control unit, used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation;

[0009] The sampling unit is connected with the main circuit unit and the temperature control unit;

[0010] The junction temperature detection unit stores a database and a function model, and is connected to the sampling unit, the driving unit and the thyristor.

[0011] The above-mentioned thyristor junction temperature online detection system, the main circuit unit includes a DC voltage source V, a diode D, an energy storage capacitor C, a current limiting resistor R2, a relay S, a discharge resistor R1 and a coaxial resistor R; the positive electrode of the DC voltage source V is connected to the anode of the diode D, and the cathode of the diode D is connected to one end of the energy storage capacitor C, one end of the relay S and one end of the current limiting resistor R2; the other end of the relay S is connected to one end of the discharge resistor R1; the other end of the current limiting resistor R2 is connected to the anode of the thyristor, and the cathode of the thyristor is connected to the coaxial resistor R; the energy storage capacitor C, the discharge resistor R1 and the coaxial resistor R are connected to the cathode of the DC voltage source V.

[0012] In the aforementioned thyristor junction temperature online detection system, the driving unit includes a thyristor driving circuit and a DC power supply; wherein the thyristor driving circuit provides the required driving current for the thyristor to change from an off state to an on state; and the DC power supply provides the required operating voltage for the thyristor driving circuit to operate normally.

[0013] The aforementioned thyristor junction temperature online detection system, wherein the junction temperature detection unit includes a thyristor gate voltage measurement module and a junction temperature calculation module. The thyristor gate voltage measurement module is used to measure the voltage between the gate and cathode of the thyristor during the process of switching from the off state to the on state; the junction temperature calculation module stores data tables and function models related to the DC bus voltage, thyristor conduction current, drive current, thyristor operating junction temperature, and the voltage between the thyristor gate and cathode under various operating conditions.

[0014] The above-mentioned thyristor junction temperature online detection system, the thyristor gate voltage measurement module includes resistors R0, R3, R4, and R es, diode D1, diode D2, diode D3, capacitor C0, operational amplifier U1, voltage regulator chip U2, signal MOSFET S0; the cathode of the diode D2 is connected to the gate of the thyristor, the anode of the diode D2 is connected to the cathode of the diode D1 and the anode of the diode D3; the cathode of the diode D1 and the anode of the diode D3 are connected to the non-inverting input terminal of the operational amplifier U1; the anode of the diode D1 and the cathode of the diode D3 are connected to the resistor R3 and the resistor R es The other end of the resistor R3 is connected to one end of the resistor R4 and the inverting input terminal of the operational amplifier U1; the other end of the resistor R4 is connected between the output terminal of the operational amplifier U1 and the resistor R0; one end of the resistor R0 is connected to the capacitor C0; the other end of the capacitor C0 is connected to the cathode of the thyristor; the drain of the signal MOSFET S0 is connected to the power supply terminal, and the source of the signal MOSFET S0 is connected to the input terminal of the voltage regulator chip U2; the adjustment terminal of the voltage regulator chip U2 is connected to the resistor R es One end of the voltage regulator chip U2 is connected to the resistor R es the other end.

[0015] In the aforementioned thyristor junction temperature online detection system, the junction temperature calculation module is implemented through digital signal processing or field programmable gate array.

[0016] The detection method of the aforementioned thyristor junction temperature online detection system comprises the following steps:

[0017] Step 1: The sampling unit collects the DC bus voltage V of the thyristor DC , thyristor conduction current I AK , driving current I G The junction temperature detection unit collects the thyristor gate voltage V GK ;

[0018] Step 2: According to the DC bus voltage V DC , thyristor conduction current I AK , driving current I G and the thyristor gate voltage V GK , and the operating junction temperature of the thyristor can be obtained by querying the database or calculating the function model.

[0019] In the aforementioned detection method of the thyristor junction temperature online detection system, the establishment of the database and function model includes the following steps:

[0020] Step 2.1: Within the rated current range of the thyristor, select n thyristor conduction current values ​​with Δi as the interval, that is, I AK -n×Δi to I AK ;

[0021] Step 2.2: Within the rated voltage range of the thyristor, select m DC bus voltage values ​​with Δu as the interval, i.e. V DC -m×Δu to V DC ;

[0022] Step 2.3: Within the trigger current range specified by the thyristor, use ΔI G As interval, select k driving current values, i.e. I AK -k×ΔI G to I G ;

[0023] Step 2.4: Within the specified junction temperature range of the thyristor, select p operating temperature values ​​with ΔT as the interval, that is, T jmax -p×ΔT to T jmax ;

[0024] Step 2.5: Select a set of parameters for calibration experiment within the range of thyristor conduction current, DC bus voltage, drive current, and operating temperature selected in Steps 2.1 to 2.4;

[0025] Step 2.6: Use the ergodic test method to perform junction temperature calibration experiments on the parameters within the specified range in turn, and measure the thyristor gate voltage V GK ;

[0026] Step 2.7: Through calibration experiments, we get n×m×k×p data points, and finally get U AK -I AK -I G -T j -V GK Database and function models.

[0027] In the aforementioned detection method of the thyristor junction temperature online detection system, the thyristor gate voltage is expressed as:

[0028] V GK =U f +U R ;

[0029] Where: U f It is expressed as the forward voltage of the PN junction inside the thyristor; U R Expressed as the voltage across the equivalent resistance of the lower case of the thyristor.

[0030] Compared with the prior art, the present invention provides an online detection system for thyristor junction temperature. The online detection system includes a main circuit unit, a drive unit, a temperature control unit, a sampling unit, and a junction temperature detection unit. The main circuit unit of the present invention is used to provide a DC bus voltage and a conduction current for the thyristor, the drive unit is used to control the conduction process of the thyristor, and the temperature control unit is used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation. The sampling unit is connected to the main circuit unit and the temperature control unit for data collection, and the junction temperature detection unit stores a database and a function model, and receives data from the sampling unit and the thyristor gate voltage collected by itself, thereby obtaining the corresponding operating junction temperature by querying the database or calculating according to the function model. The present invention utilizes the structure of the PN junction between the gate and cathode inside the thyristor and the approximately linear relationship between the forward conduction voltage drop of the PN junction and the PN junction temperature. The operating junction temperature of the thyristor is obtained by measuring the gate voltage of the thyristor. This method is more convenient and simple, and has good calculation accuracy and resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a circuit diagram of the detection system of the present invention;

[0032] Figure 2 This is the circuit diagram of the thyristor gate voltage measurement module;

[0033] Figure 3 This is a schematic diagram of the inside of a thyristor;

[0034] Figure 4 This is a schematic diagram of the internal structure of the thyristor press-fit package;

[0035] Figure 5 This is the equivalent circuit diagram of the internal structure of the thyristor press-fit package;

[0036] Figure 6 It is a flow chart of the detection method steps of the present invention;

[0037] Figure 7 It is a flowchart of the steps for establishing the database and function model;

[0038] Figure 8 It is a waveform diagram of the gate voltage during the conduction process of the thyristor;

[0039] Figure 9 This is a graph showing the relationship between the thyristor's operating junction temperature and gate voltage. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the examples, but they are not intended to limit the present invention.

[0041] Embodiment: A thyristor junction temperature online detection system, such as Figure 1 As shown, it includes a main circuit unit, which is connected to the thyristor and is used to provide a DC bus voltage and conduction current for the thyristor; the main circuit unit includes a DC voltage source V, a diode D, an energy storage capacitor C, a current limiting resistor R2, a relay S, a bleeder resistor R1 and a coaxial resistor R; the positive electrode of the DC voltage source V is connected to the anode of the diode D, and the cathode of the diode D is connected to one end of the energy storage capacitor C, one end of the relay S and one end of the current limiting resistor R2; the other end of the relay S is connected to one end of the bleeder resistor R1; the other end of the current limiting resistor R2 is connected to the anode of the thyristor, and the cathode of the thyristor is connected to the coaxial resistor R; the cathode of the energy storage capacitor C, the bleeder resistor R1 and the coaxial resistor R are connected to the cathode of the DC voltage source V.

[0042] A drive unit is connected to the thyristor and is used to control the conduction process of the thyristor; the drive unit includes a thyristor drive circuit and a DC power supply; wherein the thyristor drive circuit provides the required drive current for the thyristor to change from the off state to the on state; the DC power supply provides the required operating voltage for the normal operation of the thyristor drive circuit.

[0043] Temperature control unit, used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation;

[0044] The sampling unit is connected to the main circuit unit and the temperature control unit; the sampling unit collects the DC bus voltage V of the thyristor DC , thyristor conduction current I AK and drive current I G ; At the same time, the control temperature T of the temperature control unit and the working junction temperature of the thyristor are also collected by the sampling unit;

[0045] A junction temperature detection unit stores a database and function model and is connected to the sampling unit, drive unit, and thyristor. The junction temperature detection unit includes a thyristor gate voltage measurement module and a junction temperature calculation module. The thyristor gate voltage measurement module measures the voltage between the gate and cathode of the thyristor during the transition from the off state to the on state. The junction temperature calculation module stores data tables and function models related to the DC bus voltage, thyristor conduction current, drive current, thyristor operating junction temperature, and the voltage between the gate and cathode of the thyristor under various operating conditions. The junction temperature calculation module is implemented using digital signal processing or a field programmable gate array.

[0046] like Figure 2 As shown, the thyristor gate voltage measurement module includes resistors R0, R3, R4, and R es, diode D1, diode D2, diode D3, capacitor C0, operational amplifier U1, voltage regulator chip U2, signal MOSFET S0; the cathode of the diode D2 is connected to the gate of the thyristor, the anode of the diode D2 is connected to the cathode of the diode D1 and the anode of the diode D3; the cathode of the diode D1 and the anode of the diode D3 are connected to the non-inverting input terminal of the operational amplifier U1; the anode of the diode D1 and the cathode of the diode D3 are connected to the resistor R3 and the resistor R es The other end of the resistor R3 is connected to one end of the resistor R4 and the inverting input terminal of the operational amplifier U1; the other end of the resistor R4 is connected between the output terminal of the operational amplifier U1 and the resistor R0; one end of the resistor R0 is connected to the capacitor C0; the other end of the capacitor C0 is connected to the cathode of the thyristor; the drain of the signal MOSFET S0 is connected to the power supply terminal, and the source of the signal MOSFET S0 is connected to the input terminal of the voltage regulator chip U2; the adjustment terminal of the voltage regulator chip U2 is connected to the resistor R es One end of the voltage regulator chip U2 is connected to the resistor R es the other end.

[0047] Based on the above thyristor junction temperature online detection system, since the thyristor has a PNPN structure inside, such as Figure 3 As shown, there is a PN junction structure between the gate and cathode. The junction temperature detection method proposed in this invention utilizes the approximately linear relationship between the forward conduction voltage drop of the PN junction and the PN junction temperature to obtain the thyristor's operating junction temperature by measuring the thyristor's gate voltage. The principle is as follows:

[0048] For an ideal PN junction, the forward current I f and forward voltage U f The relationship is:

[0049]

[0050] Where: I s is the reverse saturation current of the PN junction, k is the Boltzmann constant, q is the absolute value of the electron charge, and T is the absolute temperature;

[0051] From formula (1), we can see that the forward current density j is related to the forward voltage U f The relationship is:

[0052]

[0053] Where: j s is the reverse saturation current density of the PN junction;

[0054] By taking the logarithm of both ends of equation (2), we can get the forward voltage U f The expression is:

[0055]

[0056] Since the forward current density is much greater than the reverse saturation current density, that is, j>>j s , so formula (3) can be simplified as:

[0057]

[0058] The function expression of the reverse saturation current density of the PN junction is:

[0059]

[0060] Where: n i is the intrinsic concentration, D p is the diffusion coefficient of the P region, L p is the diffusion width, N D is the doping concentration of the N region;

[0061] The functional expression of semiconductor intrinsic concentration is:

[0062]

[0063] Where: N C 、N V is the state density of the conduction band and valence band, E g is the band gap width of the semiconductor;

[0064] Substituting (5) and (6) into (4) we can obtain:

[0065]

[0066] From formula (7), we can see that when the forward current of the PN junction is constant, there is a certain relationship between the forward voltage drop of the PN junction and the junction temperature;

[0067] The bandgap function expression of semiconductor is:

[0068]

[0069] Where: E g (0), α, and β are semiconductor material parameters;

[0070] Taking the derivative of both ends of equation (8) with respect to temperature T, we can obtain:

[0071]

[0072] By taking the derivative of both ends of equation (8) with respect to temperature T, we can obtain:

[0073]

[0074] Since the thyristor chip is a silicon-based semiconductor chip, the parameters of the silicon semiconductor material at T = 300K are obtained:

[0075] E′ g | T＝300K =-2.55×10 -4 eV; (11)

[0076] E″ g | T＝300K =-4.37×10 -7 eV; (12)

[0077] From equations (11) and (12), we can see that the bandgap width is approximately a constant;

[0078] According to semiconductor materials, N C 、N V 、D p and L p ∝T ∝ , so we have:

[0079]

[0080] Where γ is a very small constant;

[0081] By taking the derivative of (13) at T = 300K, we can obtain:

[0082] (γTlnT)′| T＝300K =6.7γ; (14)

[0083]

[0084] From the above formula, we can see that when the forward current of the PN junction is constant, the forward voltage of the PN junction is approximately linearly related to the temperature T;

[0085] Combined with the internal structure of the thyristor press-fit package (such as Figure 4 As shown, the equivalent circuit diagram is as Figure 5 As shown in the figure, there is a thick cylindrical copper boss (lower tube shell) under the cathode of the thyristor chip, so the actual thyristor gate voltage V GK for:

[0086] V GK =U f +U R ; (16)

[0087] Where: U R is the equivalent resistance R of the copper boss (lower tube shell) sK The voltage on

[0088] The resistivity expression of copper material is:

[0089] ρ=ρ0(1+at); (17)

[0090] Where: ρ0 is the resistivity of copper at 0°C, a is the temperature coefficient of resistance, and t is the temperature in Celsius;

[0091] From formula (17), we can see that the resistivity of copper changes approximately linearly with temperature;

[0092] It can be seen that the thyristor gate voltage V GK It changes approximately linearly with the increase of the operating temperature of the thyristor.

[0093] Furthermore, based on the above detection system and working principle, as Figure 6 As shown, the detection method provided in this embodiment includes the following steps:

[0094] Step 1: The sampling unit collects the DC bus voltage V of the thyristor DC , thyristor conduction current I AK , driving current I G The junction temperature detection unit collects the thyristor gate voltage V GK ;

[0095] Step 2: According to the DC bus voltage V DC , thyristor conduction current I AK , driving current I G and the thyristor gate voltage V GK , and the operating junction temperature of the thyristor can be obtained by querying the database or calculating the function model.

[0096] Among them, such as Figure 7 As shown, the establishment of the database and function model includes the following steps:

[0097] Step 2.1: Within the rated current range of the thyristor, select n thyristor conduction current values ​​with Δi as the interval, that is, I AK -n×Δi to I AK ;

[0098] Step 2.2: Within the rated voltage range of the thyristor, select m DC bus voltage values ​​with Δu as the interval, i.e. V DC -m×Δu to V DC ;

[0099] Step 2.3: Within the trigger current range specified by the thyristor, use ΔI G As interval, select k driving current values, i.e. I AK -k×ΔI G to I G ;

[0100] Step 2.4: Within the specified junction temperature range of the thyristor, select p operating temperature values ​​with ΔT as the interval, that is, T jmax -p×ΔT to T jmax ;

[0101] Step 2.5: Select a set of parameters for calibration experiment within the range of thyristor conduction current, DC bus voltage, drive current, and operating temperature selected in Steps 2.1 to 2.4;

[0102] Step 2.6: Use the ergodic test method to perform junction temperature calibration experiments on the parameters within the specified range in turn, and measure the thyristor gate voltage V GK ;

[0103] Step 2.7: Through calibration experiments, we get n×m×k×p data points, and finally get U AK -I AK -I G -T j -V GK Database and function models.

[0104] After experiments, the gate voltage V GK The waveform diagram is as follows Figure 8 As shown in the figure, the relationship between the thyristor operating junction temperature and gate voltage is as follows: Figure 9 shown. Figure 8 It shows the waveform of the gate voltage VGK of the thyristor during the conduction process under the same voltage and current but different temperatures. Figure 9 It shows that the thyristor operating junction temperature and gate voltage V GK From Figure 8 and Figure 9 The junction temperature detection method proposed in the present invention can be verified by using the approximate linear relationship between the forward conduction voltage drop of the PN junction and the PN junction temperature, and measuring the gate voltage V GK The operating junction temperature of the thyristor can be obtained with certain accuracy and resolution, and it is more convenient and simple.

[0105] In summary, the present invention provides an online thyristor junction temperature detection system, comprising a main circuit unit, a drive unit, a temperature control unit, a sampling unit, and a junction temperature detection unit. The main circuit unit of the present invention is used to provide a DC bus voltage and conduction current for the thyristor, the drive unit is used to control the conduction process of the thyristor, and the temperature control unit is used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation. The sampling unit is connected to the main circuit unit and the temperature control unit for data collection, and the junction temperature detection unit stores a database and a function model, and receives data from the sampling unit and the thyristor gate voltage collected by itself, thereby obtaining the corresponding operating junction temperature by querying the database or calculating according to the function model. The present invention can detect the thyristor operating junction temperature in real time with high accuracy and resolution.

Claims

1. A thyristor junction temperature online detection system, characterized by: It includes a main circuit unit connected to the thyristor and used to provide the thyristor with a DC bus voltage and a conduction current; A driving unit, connected to the thyristor, is used to control the conduction process of the thyristor; Temperature control unit, used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation; The sampling unit is connected with the main circuit unit and the temperature control unit; A junction temperature detection unit stores a database and a function model, and is connected to the sampling unit, the drive unit, and the thyristor. The junction temperature detection unit includes a thyristor gate voltage measurement module and a junction temperature calculation module. The thyristor gate voltage measurement module is used to measure the voltage between the gate and cathode of the thyristor during the process of switching from the off state to the on state. The junction temperature calculation module stores data tables and function models related to the DC bus voltage, thyristor conduction current, drive current, thyristor operating junction temperature, and the voltage between the gate and cathode of the thyristor under various operating conditions.

2. The thyristor junction temperature online detection system according to claim 1, characterized in that: The main circuit unit includes a DC voltage source V, a diode D, an energy storage capacitor C, a current limiting resistor R2, a relay S, a discharge resistor R1 and a coaxial resistor R; the positive electrode of the DC voltage source V is connected to the anode of the diode D, and the cathode of the diode D is connected to one end of the energy storage capacitor C, one end of the relay S and one end of the current limiting resistor R2; the other end of the relay S is connected to one end of the discharge resistor R1; the other end of the current limiting resistor R2 is connected to the anode of the thyristor, and the cathode of the thyristor is connected to the coaxial resistor R; the other end of the energy storage capacitor C, the other end of the discharge resistor R1 and the other end of the coaxial resistor R are connected to the cathode of the DC voltage source V.

3. The thyristor junction temperature online detection system according to claim 1, characterized in that: The driving unit includes a thyristor driving circuit and a DC power supply; wherein the thyristor driving circuit provides the required driving current for the thyristor to change from an off state to an on state; and the DC power supply provides the required operating voltage for the thyristor driving circuit to operate normally.

4. The thyristor junction temperature online detection system according to claim 1, characterized in that: The thyristor gate voltage measurement module includes resistors R0, R3, R4, and R es , diode D1, diode D2, diode D3, capacitor C0, operational amplifier U1, voltage regulator chip U2, signal MOSFET S0; the cathode of the diode D2 is connected to the gate of the thyristor, the anode of the diode D2 is connected to the cathode of the diode D1 and the anode of the diode D3; the cathode of the diode D1 and the anode of the diode D3 are connected to the non-inverting input terminal of the operational amplifier U1; the anode of the diode D1 and the cathode of the diode D3 are connected to the resistor R3 and the resistor R es The other end of the resistor R3 is connected to one end of the resistor R4 and the inverting input terminal of the operational amplifier U1; the other end of the resistor R4 is connected between the output terminal of the operational amplifier U1 and the resistor R0; one end of the resistor R0 is connected to the capacitor C0; the other end of the capacitor C0 is connected to the cathode of the thyristor; the drain of the signal MOSFET S0 is connected to the power supply terminal, and the source of the signal MOSFET S0 is connected to the input terminal of the voltage regulator chip U2; the adjustment terminal of the voltage regulator chip U2 is connected to the resistor R es One end of the voltage regulator chip U2 is connected to the output of the resistor R es the other end.

5. The thyristor junction temperature online detection system according to claim 1, characterized in that: The junction temperature calculation module is implemented through digital signal processing or field programmable gate array.

6. The detection method of the thyristor junction temperature online detection system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: The sampling unit collects the DC bus voltage V of the thyristor DC , thyristor conduction current I AK , driving current I G The junction temperature detection unit collects the thyristor gate voltage V GK ; Step 2: According to the DC bus voltage V DC , thyristor conduction current I AK , driving current I G and the thyristor gate voltage V GK , and the operating junction temperature of the thyristor can be obtained by querying the database or calculating the function model.

7. The detection method according to claim 6, wherein: The establishment of the database and function model includes the following steps: Step 2.1: Within the rated current range of the thyristor, select n thyristor conduction current values ​​with Δi as the interval, i.e., I AK -n×Δi to I AK ; Step 2.2: Within the rated voltage range of the thyristor, select m DC bus voltage values ​​with Δu as the interval, i.e. V DC -m×Δu to V DC ; Step 2.3: Within the trigger current range specified by the thyristor, use ΔI G As interval, select k driving current values, i.e. I G -k×ΔI G to I G ; Step 2.4: Within the specified junction temperature range of the thyristor, select p operating temperature values ​​with ΔT as the interval, that is, T jmax -p×ΔT to T jmax ; Step 2.5: Select a set of parameters for calibration experiment within the range of thyristor conduction current, DC bus voltage, drive current, and operating temperature selected in Steps 2.1 to 2.4; Step 2.6: Use the ergodic test method to perform junction temperature calibration experiments on the parameters within the specified range in turn, and measure the thyristor gate voltage V GK ; Step 2.7: Through calibration experiments, we get n×m×k×p data points, and finally get V DC -I AK -I G -T j -V GK Database and function models.

8. The detection method according to claim 6, wherein: The thyristor gate voltage is expressed as: V GK =U f +U R ; Where: U f It is expressed as the forward voltage of the PN junction inside the thyristor; U R Expressed as the voltage across the equivalent resistance of the lower case of the thyristor.

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