A junction temperature monitoring system and method based on a cathode short-circuit thyristor.

Abstract

This invention discloses a junction temperature monitoring system and method based on a cathode short-circuit thyristor, comprising: a main circuit unit directly connected to the thyristor under test; a temperature control unit for regulating the ambient temperature of the thyristor during junction temperature calibration and actual operation; a gate drive and measurement unit directly connected to the gate and cathode of the thyristor; a sampling unit connected to the main circuit unit and the temperature control unit; and a junction temperature detection unit, which stores a database of gate voltages and function models under non-triggered gate current conditions and is connected to the sampling unit. The sampling unit acquires the gate current and gate voltage of the thyristor; the junction temperature detection unit, based on the acquired gate current and gate voltage, queries the internally stored database and function model, and then calculates and back-derives the operating junction temperature of the thyristor. This invention can detect the operating junction temperature of the thyristor in real time with high accuracy and resolution.

Description

Technical Field

[0001] This invention relates to the field of power electronic device testing technology, and in particular to a junction temperature monitoring system and method based on a cathode short-circuit thyristor. Background Technology

[0002] As the power electronic device with the highest single-device withstand voltage and the largest output capacity, the thyristor also has the ability to block forward and reverse voltages. It is widely used in the field of high voltage direct current (HVDC) power transmission and is the core component in HVDC power transmission projects. In the HVDC power transmission projects that are currently in operation, thyristors dominate the power devices used in converter valves.

[0003] Industry surveys show that temperature-related failures account for up to 55% of power semiconductor device failures in power electronic equipment. Junction temperature is the most critical parameter for power semiconductor devices; for every 10°C increase in junction temperature, the lifespan of a power device is halved. Therefore, monitoring the junction temperature of thyristors is of great significance for thyristor converter valves and the entire HVDC transmission system.

[0004] Extensive research by scientists and scholars has led to the classification of power device junction temperature measurement methods into four main categories: optical measurement, physical contact, thermal network modeling, and temperature-sensitive electrical parameter methods. Optical and physical contact methods typically require disassembling the device under test (DUT), which is unsuitable for thyristor junction temperature monitoring due to the unique press-fit packaging structure of thyristors. Currently, the thermal network modeling method is primarily used for thyristor junction temperature measurement. However, the press-fit packaging of thyristors results in double-sided heat dissipation, making accurate measurement of the thermal network model difficult. Inaccurate thermal network model measurements lead to inaccurate junction temperature measurements. In contrast, the temperature-sensitive electrical parameter method utilizes the relationship between external characteristic parameters of the power device and its junction temperature, deducing the junction temperature by measuring the corresponding characteristic parameters. This method offers advantages such as high measurement accuracy, fast response speed, and no need to damage the device packaging, making it considered the most promising junction temperature measurement method.

[0005] Currently, the commonly used temperature-sensitive electrical parameters of thyristors mainly include on-state voltage and gate voltage. However, in actual operation, thyristors in HVDC power transmission projects often operate under high voltage and high current conditions, making it difficult to monitor their temperature-sensitive electrical parameters online. This places high demands on measurement technology, so achieving online monitoring of thyristor junction temperature is a significant challenge. Summary of the Invention

[0006] The purpose of this invention is to provide a junction temperature monitoring system and method based on a cathode short-circuit thyristor. This invention can detect the thyristor's operating junction temperature in real time, with high accuracy and resolution.

[0007] The technical solution of the present invention is: a junction temperature monitoring system based on a cathode short-circuit thyristor, including a main circuit unit, which is directly connected to the thyristor under test and is used to provide the thyristor with DC bus voltage and conduction current;

[0008] Thyristors have a cathode short-circuit structure;

[0009] The temperature control unit is used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation.

[0010] The gate drive and measurement unit is directly connected to the gate and cathode of the thyristor and is used to drive the thyristor and control the conduction process of the thyristor, and to measure the gate voltage of the thyristor.

[0011] The sampling unit, connected to the main circuit unit and the temperature control unit, is used to collect the thyristor anode-cathode voltage, the ambient temperature of the temperature control unit, the high voltage and high capacity gate current, and the gate voltage.

[0012] The junction temperature detection unit is connected to the sampling unit and stores a database of gate voltages and function models under non-triggered gate current conditions.

[0013] The junction temperature monitoring system based on a cathode short-circuit thyristor described above includes a main circuit unit comprising a DC voltage source V, a diode D, an energy storage capacitor C, a current-limiting resistor R2, a relay S, and a bleeder resistor R1. The positive terminal 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 sampling unit. The cathode of the thyristor, the other end of the energy storage capacitor C, and the other end of the bleeder resistor R1 are connected to the cathode of the DC voltage source V.

[0014] The aforementioned junction temperature monitoring system based on a cathode short-circuit thyristor includes a gate drive and measurement unit comprising resistors R0, R3, R4, and R... es1 Resistance R es2 The system includes diodes D1, D2, D3, and D4, capacitor C0, operational amplifier U1, voltage regulator chip U2, voltage regulator chip U3, and signal MOSFET S0. The cathode of diode D2 is connected to the gate of the thyristor. The anode of diode D2 is connected to the cathode of diode D1, the anode of diode D3, and the non-inverting input of operational amplifier U1. The anode of diode D1, the cathode of diode D3, one end of resistor R3, the cathode of diode D4, and resistor R... es1 One end of the voltage regulator is connected to the adjustment terminal of the voltage regulator chip U2; the output terminal of the voltage regulator chip U2 is connected to the resistor R.es1 The other end is connected; the other end of resistor R3, one end of resistor R4, and the inverting input terminal of operational amplifier U1 are connected; the other end of resistor R4 is connected to the output terminal of operational amplifier U1 and one end of resistor R0; the other end of resistor R0 is connected to one end of capacitor C0; the other end of capacitor C0 is connected to the cathode of thyristor and the source of signal MOSFET S0; the anode of diode D4 is connected to the adjustment terminal of voltage regulator chip U3 and resistor R es2 One end is connected to the drain of the signal MOSFET S0; the output of the voltage regulator chip U3 is connected to the resistor R. es2 The other end is connected.

[0015] In the aforementioned junction temperature monitoring system based on a cathode short-circuit thyristor, the junction temperature detection unit is implemented using a digital signal processor or a field-programmable gate array.

[0016] The aforementioned monitoring method for the junction temperature monitoring system based on a cathode short-circuit thyristor includes the following steps:

[0017] Step 1: The sampling unit acquires the gate current I of the thyristor. G and gate voltage V GK ;

[0018] Step 2: The junction temperature detection unit detects the gate current I based on the collected data. G and gate voltage V GK Query the internally stored database and function model;

[0019] Step 3: The junction temperature detection unit calculates and back-derives the operating junction temperature of the thyristor.

[0020] The aforementioned monitoring method for the junction temperature monitoring system based on a cathode short-circuit thyristor includes the following steps in establishing the database and function model:

[0021] Step 2.1: Within the specified junction temperature range of the thyristor, select n operating junction temperature values ​​at intervals of ΔT, i.e., T j,max -n×ΔT to T j,max ;

[0022] Step 2.2: Within the specified gate non-trigger current range of the thyristor, with ΔI... gt For intervals, m gate non-trigger current values ​​are selected, i.e., I gt，max -m×ΔI gt To I gt，max ;

[0023] Step 2.3: Within the high-voltage, high-capacity thyristor junction temperature range and gate non-trigger current range selected in Steps 2.1-2.2 above, select a set of parameters to conduct a junction temperature calibration experiment;

[0024] Step 2.4: Using the traversal experimental method, perform junction temperature calibration experiments on parameters within each specified range sequentially, and measure the gate non-trigger current I of the thyristor. gt Gate voltage V under certain conditions GK ;

[0025] Step 2.7: Through the junction temperature calibration experiment, n×m data points are obtained, and finally I is obtained. gt -T j -V GK Database and function models.

[0026] In the aforementioned monitoring method for the junction temperature monitoring system based on a cathode short-circuit thyristor, step 3 involves the sampling unit acquiring the anode-cathode voltage V of the thyristor. AK Gate current I G thyristor gate voltage V GK When the collected gate current I G Equal to the gate non-trigger current I gt At this time, extract the gate voltage V. GK Then through I gt -T j -V GK The operating junction temperature T of the thyristor is obtained by reverse calculation using database and function model. j .

[0027] Compared with the prior art, the present invention provides a junction temperature monitoring system based on a cathode short-circuit thyristor. This online detection system includes a main circuit unit, a temperature control unit, a gate drive and measurement unit, a sampling unit, and a junction temperature detection unit. The main circuit unit provides DC bus voltage and conduction current to the thyristor. The temperature control unit regulates the ambient temperature of the thyristor during junction temperature calibration and actual operation. The gate drive and measurement unit drives the thyristor and controls its conduction process, and measures the gate voltage. The sampling unit collects the thyristor anode-cathode voltage, the ambient temperature of the temperature control unit, the high-voltage, high-capacity gate current, and the gate voltage. The junction temperature detection unit stores data in a database and a function model, and receives data from the sampling unit, thereby obtaining the corresponding operating junction temperature by querying the database or calculating from the function model. This invention utilizes the cathode short-circuit structure of a thyristor. When a non-triggered gate current passes through the gate of the thyristor, the thyristor is in a blocking state and will not conduct. By utilizing the approximately linear relationship between the voltage drop across the P-base region and the operating temperature, the operating junction temperature of the thyristor can be obtained by measuring the gate voltage under the non-triggered gate current. This method does not disrupt the normal operating state of the thyristor, is more convenient and simple, and has good calculation accuracy. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the detection system circuit of the present invention;

[0029] Figure 2 This is a circuit diagram of the thyristor gate drive and measurement unit;

[0030] Figure 3 This is a schematic diagram of the internal structure of a thyristor with a cathode short-circuit structure.

[0031] Figure 4 It is an equivalent circuit diagram of the internal structure of a thyristor with a cathode short-circuit structure;

[0032] Figure 5 This is a flowchart of the monitoring method steps of the present invention;

[0033] Figure 6 This is a flowchart of the steps for establishing the database and function model of this invention;

[0034] Figure 7 This is a graph showing the relationship between the junction temperature of a thyristor and the gate voltage under non-triggering gate current. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0036] Example: A junction temperature monitoring system based on a cathode short-circuit thyristor includes a main circuit unit directly connected to the thyristor under test, used to provide the thyristor with DC bus voltage and conduction current; 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, and a bleeder resistor R1; the positive terminal 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 a sampling unit; the cathode of the thyristor, the other end of the energy storage capacitor C, and the other end of the bleeder resistor R1 are connected to the cathode of the DC voltage source V.

[0037] Thyristors have a cathode short-circuit structure;

[0038] The temperature control unit is used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation.

[0039] A gate driving and measurement unit, directly connected to the gate and cathode of the thyristor, is used to drive the thyristor, control its conduction process, and measure its gate voltage. The gate driving and measurement unit includes resistors R0, R3, R4, and R... es1 Resistance R es2The system includes diodes D1, D2, D3, and D4, capacitor C0, operational amplifier U1, voltage regulator chip U2, voltage regulator chip U3, and signal MOSFET S0. The cathode of diode D2 is connected to the gate of the thyristor. The anode of diode D2 is connected to the cathode of diode D1, the anode of diode D3, and the non-inverting input of operational amplifier U1. The anode of diode D1, the cathode of diode D3, one end of resistor R3, the cathode of diode D4, and resistor R... es1 One end is connected to the adjustment terminal of the voltage regulator chip U2; the output terminal of the voltage regulator chip U2 is connected to the resistor R. es1 The other end is connected; the other end of resistor R3, one end of resistor R4, and the inverting input terminal of operational amplifier U1 are connected; the other end of resistor R4 is connected to the output terminal of operational amplifier U1 and one end of resistor R0; the other end of resistor R0 is connected to one end of capacitor C0; the other end of capacitor C0 is connected to the cathode of thyristor and the source of signal MOSFET S0; the anode of diode D4 is connected to the adjustment terminal of voltage regulator chip U3 and resistor R es2 One end is connected to the drain of the signal MOSFET S0; the output of the voltage regulator chip U3 is connected to the resistor R. es2 The other end is connected.

[0040] The sampling unit, connected to the main circuit unit and the temperature control unit, is used to collect the thyristor anode-cathode voltage, the ambient temperature of the temperature control unit, the high voltage and high capacity gate current, and the gate voltage.

[0041] A junction temperature detection unit, connected to the sampling unit, stores a database of gate voltages and a function model under non-triggered gate current conditions. The junction temperature detection unit is implemented using a digital signal processor or a field-programmable gate array (FPGA).

[0042] The principles of this invention will be explained below.

[0043] Thyristors have the ability to block both forward and reverse voltages and are widely used in high-voltage direct current applications. Based on the internal structure of the thyristor, the expression for the anode current is as follows:

[0044] (1)

[0045] In the formula: It refers to the common-base current gain of the internal PNP transistor. It is the common-base current gain of the internal NPN transistor. It is the leakage current of the internal PNP transistor. It is the leakage current of the internal NPN transistor.

[0046] When the transistor emitter current is very low, the transistor's common-base current gain It is very small, but once the emitter current is established, the common-base current gain... It grows rapidly.

[0047] When the thyristor is in the blocking state, the gate current I G =0, It is very small. Therefore, according to equation (1), the leakage current of the thyristor at this time is almost equal to the sum of the leakage currents of the two transistors.

[0048] When the thyristor is in the ON state, a forward voltage is applied across its terminals, and a gate current I is injected. G , As the value rapidly increases to near 1, the thyristor enters a saturated conduction state.

[0049] In the blocking state, as the positive voltage across the thyristor continuously increases, the leakage current of the thyristor will gradually increase. This is because under low current conditions... Since it is not equal to 0, its forward blocking voltage is much smaller than its reverse blocking voltage. Therefore, reducing the voltage of the NPN transistor on the cathode side... This will increase the forward blocking voltage of the thyristor. Therefore, cathode short-circuit technology is typically used in thyristors to reduce the forward blocking voltage of NPN transistors. This is to increase its forward blocking voltage. In fact, when When reduced to 0, the forward blocking voltage can be increased to near the reverse blocking voltage of the thyristor.

[0050] In this embodiment, the internal structure of the thyristor is as follows: Figure 3 As shown, this thyristor uses cathode short-circuit technology.

[0051] Cathode short-circuit technology involves placing the N-type transistor on the thyristor chip. + The cathode region and the P-type base region are short-circuited by the cathode metal electrode. The bulk resistance and contact resistance of the P-type base region form a shunt resistance between the gate and cathode of the thyristor, thereby reducing the current. The purpose. Figure 4 This is the internal equivalent circuit of a thyristor employing cathode short-circuit technology.

[0052] For metal-semiconductor contacts in semiconductors, the contact resistance can be expressed by the following formula:

[0053] ;

[0054] In the formula: It is the height of the barrier. It refers to the semiconductor doping concentration. It is the dielectric constant of a semiconductor. It is the effective electron mass. This is Planck's constant. Typically, in power semiconductor devices, the contact resistance is less than 1 × 10⁻⁶. -5 Ω∙cm 2 Therefore, the contact resistance of the thyristor It is usually negligible.

[0055] The bulk resistivity of the P-type base region can be expressed as:

[0056] (3)

[0057] In the formula: It is the carrier mobility in the P-base region. It represents the doping concentration of the P-based region. It is the absolute value of the electron charge;

[0058] Carrier mobility is a function of temperature T. The carriers in the p-type base region are holes. At low doping concentrations (less than 10⁻⁶),... 15 cm -3 In semiconductors, specifically silicon-based devices, the hole mobility can be expressed as:

[0059] (4)

[0060] From equations (3) and (4), it can be seen that the volume resistivity of the P-type base region is a function of temperature T.

[0061] When the gate non-triggered current flows through the thyristor gate, the gate voltage V is at this time. GK It can be represented as:

[0062] (5)

[0063] In the formula: It is the bulk resistance of the P-base region. The pressure drop generated above, It is the contact resistance between the p-based semiconductor and the cathode metal plate. The pressure drop generated above;

[0064] Due to contact resistance It is very small, usually negligible. Meanwhile, the gate non-trigger current I... gt Very small, typically in the milliampere range; therefore, the contact resistance is... Pressure drop This is also negligible. Therefore, the gate voltage V in equation (5) is... GK It can be simplified to:

[0065] ;

[0066] Due to the bulk resistivity of the P-type base region It is a function of temperature T, so the gate non-trigger current I... gt Under certain conditions, volume resistance Pressure drop It is also a functional relationship with temperature T, that is, the relationship between the thyristor and the gate non-triggering current I. gt Gate voltage V GK The operating temperature of a thyristor can be deduced from its temperature-sensitive electrical parameters.

[0067] Based on the above technical principles, this invention also provides a method for online monitoring of thyristor junction temperature, such as... Figure 5 As shown, it includes the following steps:

[0068] Step 1: The sampling unit acquires the gate current I of the thyristor. G and gate voltage V GK The gate current I G Essentially, there are two scenarios: one is during the driving process, the gate current I... G It is the drive current, while during non-drive periods, the gate current I... G This is the gate non-trigger current. The principle of this method utilizes the gate voltage corresponding to the non-trigger current.

[0069] Step 2: The junction temperature detection unit detects the gate current I based on the collected data. G and gate voltage V GK This step involves querying the internally stored database and function model; in this step, such as... Figure 6 As shown, the establishment of the database and function model includes the following steps:

[0070] Step 2.1: Within the specified junction temperature range of the thyristor, select n operating junction temperature values ​​at intervals of ΔT, i.e., T j,max -n×ΔT to T j,max ;

[0071] Step 2.2: Within the specified gate non-trigger current range of the thyristor, with ΔI... gt For intervals, m gate non-trigger current values ​​are selected, i.e., I gt，max -m×ΔI gt To I gt，max ;

[0072] Step 2.3: Within the high-voltage, high-capacity thyristor junction temperature range and gate non-trigger current range selected in Steps 2.1-2.2 above, select a set of parameters to conduct a junction temperature calibration experiment;

[0073] Step 2.4: Using the traversal experimental method, perform junction temperature calibration experiments on parameters within each specified range sequentially, and measure the gate non-trigger current I of the thyristor. gtGate voltage V under certain conditions GK ;

[0074] Step 2.7: Through the junction temperature calibration experiment, n×m data points are obtained, and finally I is obtained. gt -T j -V GK Database and function models.

[0075] Step 3: The junction temperature detection unit calculates and reverses to obtain the operating junction temperature of the thyristor, that is, the sampling unit collects the anode-cathode voltage V of the thyristor. AK Gate current I G thyristor gate voltage V GK When the collected gate current I G Equal to the gate non-trigger current I gt At this time, extract the gate voltage V. GK Then through I gt -T j -V GK The operating junction temperature T of the thyristor is obtained by reverse calculation using database and function model. j .

[0076] The applicant, through experiments, obtained the relationship between the thyristor junction temperature and the gate voltage under non-triggered gate current as follows: Figure 7 As shown. From Figure 7 This invention can verify the junction temperature detection method proposed in this invention, namely, the thyristor under gate non-trigger current I. gt Gate voltage V GK The operating temperature of a thyristor can be deduced from its temperature-sensitive electrical parameter by measuring its gate voltage V. GK It can obtain the operating junction temperature of the thyristor with a certain accuracy and resolution, and it is more convenient and simple.

[0077] In summary, this invention provides a junction temperature monitoring system based on a cathode short-circuit thyristor. This online monitoring system includes a main circuit unit, a temperature control unit, a gate drive and measurement unit, a sampling unit, and a junction temperature detection unit. The main circuit unit provides the thyristor with DC bus voltage and conduction current. The temperature control unit regulates the ambient temperature of the thyristor during junction temperature calibration and actual operation. The gate drive and measurement unit drives the thyristor, controls its conduction process, and measures its gate voltage. The sampling unit collects the thyristor anode-cathode voltage, the ambient temperature of the temperature control unit, the high-voltage, high-capacity gate current, and the gate voltage. The junction temperature detection unit stores data in a database and a function model, and receives data from the sampling unit, thereby obtaining the corresponding operating junction temperature by querying the database or calculating from the function model. This invention utilizes the cathode short-circuit structure of a thyristor. When a non-triggered gate current passes through the gate of the thyristor, the thyristor is in a blocking state and will not conduct. By utilizing the approximately linear relationship between the voltage drop across the P-base region and the operating temperature, the operating junction temperature of the thyristor can be obtained by measuring the gate voltage under the non-triggered gate current. This method does not disrupt the normal operating state of the thyristor, is more convenient and simple, and has good calculation accuracy.

Claims

1. A junction temperature monitoring system based on a cathode short-circuit thyristor, comprising a main circuit unit directly connected to the thyristor under test, used to provide the thyristor with DC bus voltage and conduction current; the thyristor having a cathode short-circuit structure; and a temperature control unit used to regulate the ambient temperature of the thyristor during junction temperature calibration and actual operation; characterized in that: It also includes a gate drive and measurement unit, which is directly connected to the gate and cathode of the thyristor, for driving the thyristor and controlling the conduction process of the thyristor, and measuring the gate voltage of the thyristor. The sampling unit, connected to the main circuit unit and the temperature control unit, is used to collect the thyristor anode-cathode voltage, the ambient temperature of the temperature control unit, the high voltage and high capacity gate current, and the gate voltage. The junction temperature detection unit is connected to the sampling unit and stores a database of gate voltages and function models under non-triggering current conditions. The bulk resistivity of the P-type base region inside the thyristor is a function of temperature T as follows: When the gate non-triggered current flows through the thyristor gate, the gate voltage V is at this time. GK Represented as: ； In the formula: It is the bulk resistance of the P-base region. The pressure drop generated above, It is the contact resistance between the p-based semiconductor and the cathode metal plate. The pressure drop generated above; Due to contact resistance Very small, usually negligible, while the gate non-trigger current I gt Very small, typically in the milliampere range, therefore the contact resistance is... Pressure drop This is also negligible, so the gate voltage V GK Simplified to: ； Due to the bulk resistivity of the P-type base region It is a function of temperature T, so the gate non-trigger current I... gt Under certain conditions, volume resistance Pressure drop It is also a functional relationship with temperature T, that is, the relationship between the thyristor and the gate non-triggering current I. gt Gate voltage V GK The operating temperature of a thyristor can be deduced from its temperature-sensitive electrical parameters. During the driving process, the gate current I G It is the drive current, while during non-drive periods, the gate current I... G It is the gate non-trigger current.

2. The junction temperature monitoring system based on a cathode short-circuit thyristor 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, and a bleeder resistor R1. The positive terminal 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 sampling unit. The cathode of the thyristor, the other end of the energy storage capacitor C, and the other end of the bleeder resistor R1 are connected to the cathode of the DC voltage source V.

3. The junction temperature monitoring system based on a cathode short-circuit thyristor according to claim 1, characterized in that: The gate driving and measurement unit includes resistors R0, R3, R4, and R... es1 Resistance R es2 The system includes diodes D1, D2, D3, and D4, capacitor C0, operational amplifier U1, voltage regulator chip U2, voltage regulator chip U3, and signal MOSFET S0. The cathode of diode D2 is connected to the gate of the thyristor. The anode of diode D2 is connected to the cathode of diode D1, the anode of diode D3, and the non-inverting input of operational amplifier U1. The anode of diode D1, the cathode of diode D3, one end of resistor R3, the cathode of diode D4, and resistor R... es1 One end is connected to the adjustment terminal of the voltage regulator chip U2; the output terminal of the voltage regulator chip U2 is connected to the resistor R. es1 The other end is connected; the other end of resistor R3, one end of resistor R4, and the inverting input terminal of operational amplifier U1 are connected; the other end of resistor R4 is connected to the output terminal of operational amplifier U1 and one end of resistor R0; the other end of resistor R0 is connected to one end of capacitor C0; the other end of capacitor C0 is connected to the cathode of thyristor and the source of signal MOSFET S0; the anode of diode D4 is connected to the adjustment terminal of voltage regulator chip U3 and resistor R es2 One end is connected to the drain of the signal MOSFET S0; the output of the voltage regulator chip U3 is connected to the resistor R. es2 The other end is connected.

4. The junction temperature monitoring system based on a cathode short-circuit thyristor according to claim 1, characterized in that: The junction temperature detection unit is implemented using a digital signal processor or a field-programmable gate array.

5. The monitoring method of the junction temperature monitoring system based on a cathode short-circuit thyristor according to any one of claims 1-4, characterized in that: Includes the following steps: Step 1: The sampling unit acquires the gate current I of the thyristor. G and gate voltage V GK ; Step 2: The junction temperature detection unit detects the gate current I based on the collected data. G and gate voltage V GK Query the internally stored database and function model; Step 3: The junction temperature detection unit calculates and back-derives the operating junction temperature of the thyristor.

6. The monitoring method of the junction temperature monitoring system based on a cathode short-circuit thyristor according to claim 5, characterized in that: The establishment of the database and function model includes the following steps: Step 2.1: Within the specified junction temperature range of the thyristor, select n operating junction temperature values ​​at intervals of ΔT, i.e., T j,max -n×ΔT to T j,max ; Step 2.2: Within the specified gate non-trigger current range of the thyristor, with ΔI... gt For intervals, m gate non-trigger current values ​​are selected, i.e., I gt，max -m×ΔI gt To I gt，max ; Step 2.3: Within the high-voltage, high-capacity thyristor junction temperature range and gate non-trigger current range selected in Steps 2.1-2.2 above, select a set of parameters to conduct a junction temperature calibration experiment; Step 2.4: Using the traversal experimental method, perform junction temperature calibration experiments on parameters within each specified range sequentially, and measure the gate non-trigger current I of the thyristor. gt Gate voltage V under certain conditions GK ; Step 2.7: Through the junction temperature calibration experiment, n×m data points are obtained, and finally I is obtained. gt -T j -V GK Database and function models.

7. The monitoring method of the junction temperature monitoring system based on a cathode short-circuit thyristor according to claim 6, characterized in that: In step 3, the monitoring process of the working junction temperature is achieved by the sampling unit acquiring the anode-cathode voltage V of the thyristor. AK Gate current I G thyristor gate voltage V GK When the collected gate current I G Equal to the gate non-trigger current I gt At this time, extract the gate voltage V. GK Then through I gt -T j -V GK The operating junction temperature T of the thyristor is obtained by reverse calculation using database and function model. j .

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