A Method and Device for Calculating the Junction Temperature of a DC Load Unloading Device

Abstract

The present application discloses a method and device for calculating the junction temperature of a DC unloading device. The method includes: creating an electromagnetic transient simulation model and simulating to obtain multiple sets of current, turn-on and turn-off information, determining the maximum total loss energy of the DC unloading device, using a thermal network simulation model to calculate the reference maximum junction temperature of the DC unloading device, calculating the target loss energy of the DC unloading device at the reference maximum junction temperature through target current information, so as to determine the target maximum junction temperature. It can be seen that by obtaining the current and switch action information during the input process of the DC unloading device through electromagnetic transient simulation, there is no need to establish a three-dimensional model of IGBT or IGCT, which greatly reduces the workload and time for calculating the maximum total loss energy. Using the calculated reference maximum junction temperature as the iterative input and performing iterative calculation on the loss again makes the finally calculated junction temperature more accurate, thereby improving the efficiency of calculating the junction temperature of the DC unloading device.

Description

Technical Field

[0001] The present application relates to the field of high - voltage flexible DC power transmission, and more specifically, to a method and device for calculating the junction temperature of a DC load shedding device. Background Art

[0002] With the continuous increase in power consumption demand, regions with high power generation need to transmit electricity to regions with large power consumption demands. This process may involve cross - sea power transmission, and the technology for transmitting offshore wind power needs to be continuously developed. During the process of transmitting offshore wind power, the reliability of the DC transmission project for offshore wind power needs to be ensured.

[0003] The DC load shedding device in the offshore wind power flexible DC transmission system is an important component. When an AC fault occurs in the receiving - end power grid, causing the offshore wind power flexible DC transmission system to be unable to transmit DC power, it will accumulate inside the offshore wind power flexible DC transmission system. At this time, the DC load shedding device can consume the accumulated DC power, thereby avoiding over - voltage or even tripping of the system caused by the inability to transmit DC power.

[0004] The working time of the DC load shedding device usually does not exceed 2 s. During this process, due to the frequent switching of high - power power electronic devices such as IGBT (Insulated Gate Bipolar Transistor) or IGCT (Integrated Gate Commutated Thyristor), a large amount of self - generated loss will cause thermal accumulation and temperature rise. Therefore, it is necessary to calculate the junction temperature of the temperature rise situation to protect the load shedding device from thermal breakdown.

[0005] Currently, the method for calculating the junction temperature of IGBT or IGCT is to use the finite - element simulation method, which requires building a three - dimensional model of IGBT or IGCT. This has a large workload, takes a long time, and requires a large amount of computing time and resources for the second - level power consumption load shedding, resulting in low simulation efficiency. For the DC load shedding device, applying the junction temperature calculation method of IGBT or IGCT is only applicable to high - voltage and high - power test scenarios, so it is not applicable either. Summary of the Invention

[0006] In view of the above problems, the present application is proposed to provide a method and device for calculating the junction temperature of a DC load shedding device to improve the efficiency of calculating the junction temperature of the DC load shedding device.

[0007] To achieve the above objective, the following specific solutions are proposed:

[0008] A method for calculating the junction temperature of a DC load shedding device includes:

[0009] Create an electromagnetic transient simulation model with a DC load shedding device;

[0010] Determine multiple preset power parameters, and under each power parameter, perform a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or an integrated gate-commutated thyristor (IGCT) is put into operation;

[0011] Analyze the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters, determine the maximum total loss energy of the DC unloading device, and the target current information of the DC unloading device at the maximum total loss energy;

[0012] Use the pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy;

[0013] Calculate the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy;

[0014] Determine the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0015] Optionally, the determining multiple preset power parameters, and under each power parameter, performing a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an IGBT or an IGCT is put into operation, includes:

[0016] Determine multiple power parameters for simulating the electromagnetic transient simulation model according to a preset unit power parameter;

[0017] Under each power parameter, drive the electromagnetic transient simulation model to put the IGBT or IGCT in the DC unloading device into operation when a three-phase short-circuit fault occurs, and after a preset simulation time after the DC unloading device is put into operation, determine the current information, turn-on information, and turn-off information of the DC unloading device under this power parameter.

[0018] Optionally, the analyzing the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters, determining the maximum total loss energy of the DC unloading device, and the target current information of the DC unloading device at the maximum total loss energy, includes:

[0019] Based on the current information of the DC unloading device under each power parameter, the first preset threshold voltage, and the first preset slope resistance, calculate the conduction loss energy of the DC unloading device within the preset simulation time under this power parameter;

[0020] Based on the turn-off information of the DC unloading device under each power parameter, calculate the turn-off loss energy of the DC unloading device within the preset simulation time under this power parameter;

[0021] Based on the turn-on information of the DC unloading device under each power parameter, calculate the turn-on loss energy of the DC unloading device within the preset simulation time under this power parameter;

[0022] Accumulate the conduction loss energy, the turn-off loss energy, and the turn-on loss energy under each power parameter to obtain the total loss energy of the DC unloading device under this power parameter;

[0023] Determine the maximum total loss energy among the total loss energies of the DC unloading device under various power parameters, and determine the current information of the DC unloading device under the power parameter corresponding to the maximum total loss energy as the target current information.

[0024] Optionally, the calculating the turn-off loss energy of the DC unloading device within the preset simulation time under each power parameter based on the turn-off information of the DC unloading device under each power parameter includes:

[0025] According to the turn-off information of the DC unloading device under each power parameter, determine the number of turn-offs of the DC unloading device within the preset simulation time under each power parameter;

[0026] Determine the loss energy of each turn-off of the DC unloading device under each power parameter;

[0027] Accumulate the loss energies of each turn-off of the DC unloading device under each power parameter as the turn-off loss energy of the DC unloading device within the preset simulation time.

[0028] Optionally, the calculating the turn-on loss energy of the DC unloading device within the preset simulation time under each power parameter based on the turn-on information of the DC unloading device under each power parameter includes:

[0029] According to the turn-on information of the DC unloading device under each power parameter, determine the number of turn-ons of the DC unloading device within the preset simulation time under each power parameter;

[0030] Determine the loss energy of each turn-on of the DC unloading device under each power parameter;

[0031] Accumulate the loss energy of each turn-on of the DC unloading device under each power parameter, which is the turn-off loss energy of the DC unloading device within the preset simulation time.

[0032] Optionally, the calculating the reference maximum junction temperature of the DC unloading device by using the pre-established thermal network simulation model with the DC unloading device and combining the maximum total loss energy includes:

[0033] Divide the maximum total loss energy by the preset simulation time to obtain the heating power of the DC unloading device;

[0034] Calculate the reference maximum junction temperature of the DC unloading device according to the heating power and the total resistance value of each resistor in the pre-established thermal network simulation model.

[0035] Optionally, calculating the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy includes:

[0036] Calculate the target turn-off loss energy and target turn-on loss energy of the DC unloading device at the reference maximum junction temperature;

[0037] Calculate the target threshold voltage of the DC unloading device at the reference maximum junction temperature by using the first preset threshold voltage and the second preset threshold voltage;

[0038] Calculate the target slope resistance of the DC unloading device at the reference maximum junction temperature by using the first preset slope resistance and the second preset slope resistance;

[0039] Calculate the target conduction loss of the DC unloading device at the reference maximum junction temperature according to the target current information, the target threshold voltage, the target slope resistance and the preset simulation time;

[0040] Accumulate the target conduction loss energy, the target turn-off loss energy and the target turn-on loss energy to obtain the target loss energy of the DC unloading device.

[0041] Optionally, calculating the target turn-off loss energy and target turn-on loss energy of the DC unloading device at the reference maximum junction temperature includes:

[0042] Determine the turn-off loss at the first reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the first reference temperature;

[0043] Determine the turn-off loss at the second reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the second reference temperature;

[0044] Determine the turn-on loss at the first reference temperature according to the relationship curve between the turn-on energy and the turn-on current at the existing first reference temperature;

[0045] Determine the turn-on loss at the second reference temperature according to the relationship curve between the turn-on energy and the turn-on current at the existing second reference temperature;

[0046] Calculate the target turn-off loss energy and the target turn-on loss energy of the DC unloading device according to the first reference temperature, the second reference temperature, the turn-off loss and the turn-on loss at the first reference temperature, the turn-off loss and the turn-on loss at the second reference temperature, and the reference maximum junction temperature.

[0047] Optionally, determining the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all the resistors in the thermal network simulation model includes:

[0048] Divide the target loss energy by the preset simulation time to obtain the target heating power of the DC unloading device;

[0049] Based on the target heating power and the total resistance value of each resistor in the thermal network simulation model, calculate the target maximum junction temperature of the DC unloading device.

[0050] A junction temperature calculation device for a DC unloading device, comprising:

[0051] A model creation unit for creating an electromagnetic transient simulation model with a DC unloading device;

[0052] A model simulation unit for determining a variety of preset power parameters, and performing a fault simulation on the electromagnetic transient simulation model under each power parameter to obtain the current information, turn-on information and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor IGBT or an integrated gate-commutated thyristor IGCT is put into operation;

[0053] A loss information determination unit for analyzing the current information, turn-on information and turn-off information of the DC unloading device with various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy;

[0054] A reference junction temperature calculation unit for using a pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy;

[0055] A target loss energy calculation unit, configured to calculate the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy;

[0056] A target junction temperature determination unit, configured to determine the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0057] Optionally, the model simulation unit includes:

[0058] A power parameter determination unit, configured to determine various power parameters for simulating the electromagnetic transient simulation model according to preset unit power parameters;

[0059] A power test parameter determination unit, configured to drive the IGBT or IGCT in the DC unloading device when the electromagnetic transient simulation model has a three-phase short-circuit fault under each power parameter, and determine the current information, turn-on information, and turn-off information of the DC unloading device under this power parameter after a preset simulation time after the DC unloading device is put into operation.

[0060] Optionally, the loss information determination unit includes:

[0061] A first loss information determination subunit, configured to calculate the conduction loss energy of the DC unloading device within the preset simulation time under this power parameter based on the current information of the DC unloading device, a first preset threshold voltage, and a first preset slope resistance under each power parameter;

[0062] A second loss information determination subunit, configured to calculate the turn-off loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-off information of the DC unloading device under each power parameter;

[0063] A third loss information determination subunit, configured to calculate the turn-on loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-on information of the DC unloading device under each power parameter;

[0064] A fourth loss information determination subunit, configured to accumulate the conduction loss energy, the turn-off loss energy, and the turn-on loss energy under each power parameter to obtain the total loss energy of the DC unloading device under this power parameter;

[0065] The fifth loss information determination subunit is configured to determine the maximum total loss energy among the total loss energies of the DC unloading device under various power parameters, and determine the current information of the DC unloading device under the power parameters corresponding to the maximum total loss energy as the target current information.

[0066] Optionally, the second loss information determination subunit includes:

[0067] The turn-off times determination unit is configured to determine the turn-off times of the DC unloading device within the preset simulation time under each power parameter according to the turn-off information of the DC unloading device under each power parameter;

[0068] The turn-off loss energy determination unit is configured to determine the loss energy of each turn-off of the DC unloading device under each power parameter;

[0069] The turn-off loss energy accumulation unit is configured to accumulate the loss energies of each turn-off of the DC unloading device under each power parameter as the turn-off loss energy of the DC unloading device within the preset simulation time.

[0070] Optionally, the third loss information determination subunit includes:

[0071] The turn-on times determination unit is configured to determine the turn-on times of the DC unloading device within the preset simulation time under each power parameter according to the turn-on information of the DC unloading device under each power parameter;

[0072] The turn-on loss energy determination unit is configured to determine the loss energy of each turn-on of the DC unloading device under each power parameter;

[0073] The turn-on loss energy accumulation unit is configured to accumulate the loss energies of each turn-on of the DC unloading device under each power parameter as the turn-off loss energy of the DC unloading device within the preset simulation time.

[0074] Optionally, the reference junction temperature calculation unit includes:

[0075] The heating power calculation unit is configured to divide the maximum total loss energy by the preset simulation time to obtain the heating power of the DC unloading device;

[0076] The reference maximum junction temperature calculation unit is configured to calculate the reference maximum junction temperature of the DC unloading device according to the heating power and the total resistance value of each resistor in the pre-established thermal network simulation model.

[0077] Optionally, the target loss energy calculation unit includes:

[0078] The first target loss energy calculation unit is configured to calculate the target turn-off loss energy and the target turn-on loss energy of the DC unloading device at the reference maximum junction temperature;

[0079] The second target loss energy calculation unit is configured to calculate the target threshold voltage of the DC unloading device at the reference maximum junction temperature by using the first preset threshold voltage and the second preset threshold voltage;

[0080] The third target loss energy calculation unit is configured to calculate the target slope resistance of the DC unloading device at the reference maximum junction temperature by using the first preset slope resistance and the second preset slope resistance;

[0081] The fourth target loss energy calculation unit is configured to calculate the target conduction loss of the DC unloading device at the reference maximum junction temperature according to the target current information, the target threshold voltage, the target slope resistance, and the preset simulation time;

[0082] The fifth target loss energy calculation unit is configured to accumulate the target conduction loss energy, the target turn-off loss energy, and the target turn-on loss energy to obtain the target loss energy of the DC unloading device.

[0083] Optionally, the first target loss energy calculation unit includes:

[0084] The first turn-off loss determination unit is configured to determine the turn-off loss at the first reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the first reference temperature;

[0085] The second turn-off loss determination unit is configured to determine the turn-off loss at the second reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the second reference temperature;

[0086] The first turn-on loss determination unit is configured to determine the turn-on loss at the first reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the first reference temperature;

[0087] The second turn-on loss determination unit is configured to determine the turn-on loss at the second reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the second reference temperature;

[0088] The target turn-on loss energy calculation unit is configured to calculate the target turn-off loss energy and the target turn-on loss energy of the DC unloading device according to the first reference temperature, the second reference temperature, the turn-off loss and turn-on loss at the first reference temperature, the turn-off loss and turn-on loss at the second reference temperature, and the reference maximum junction temperature.

[0089] Optionally, the target junction temperature determination unit includes:

[0090] A first target junction temperature determination subunit, configured to divide the target loss energy by the preset simulation time to obtain the target heating power of the DC unloading device;

[0091] A second target junction temperature determination subunit, configured to calculate the target maximum junction temperature of the DC unloading device based on the target heating power and the total resistance value of each resistor in the thermal network simulation model.

[0092] With the above technical solution, the present application creates an electromagnetic transient simulation model with a DC unloading device, determines a variety of preset power parameters, and performs a fault simulation on the electromagnetic transient simulation model under each power parameter to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or an integrated gate-commutated thyristor (IGCT) is turned on. Analyze the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy. Use the pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy. Calculate the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy, and determine the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model. It can be seen that by obtaining the current and switch action information during the input process of the DC unloading device through electromagnetic transient simulation, there is no need to establish a three-dimensional model of the IGBT or IGCT, which greatly reduces the workload and time for calculating the maximum total loss energy. Using the calculated reference maximum junction temperature as an iterative input to perform iterative calculation on the loss again makes the finally calculated target maximum junction temperature more accurate, thereby improving the efficiency of calculating the target maximum junction temperature of the DC unloading device. Description of the Drawings

[0093] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0094] Figure 1 It is a schematic flowchart of a method for implementing the junction temperature calculation of a DC unloading device provided by an embodiment of the present application;

[0095] Figures 2(a)-(c) are schematic diagrams of three electromagnetic transient simulation models with a DC unloading device provided by an embodiment of the present application;

[0096] Figure 3 It is a schematic diagram of the voltage and current waveforms of an IGBT or IGCT provided by an embodiment of the present application;

[0097] Figure 4 It is a schematic topological diagram of a thermal network simulation model of an IGBT or IGCT provided by an embodiment of the present application;

[0098] Figure 5 It is a schematic diagram of the device structure for implementing the junction temperature calculation of the DC unloading device provided by an embodiment of the present application;

[0099] Figure 6 It is a schematic diagram of the structure of a device for implementing the junction temperature calculation of the DC unloading device provided by an embodiment of the present application. Detailed implementation manners

[0100] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0101] The solution of the present application can be implemented based on a terminal with data processing capabilities, and the terminal can be a computer, a server, the cloud, etc.

[0102] Next, in combination with Figure 1 As described above, the method for calculating the junction temperature of the DC unloading device of the present application may include the following steps:

[0103] Step S110: Create an electromagnetic transient simulation model with a DC unloading device.

[0104] Specifically, for the electromagnetic transient simulation model with a DC unloading device, one of the several preset building schemes can be selected for building. As shown in Figure 2(a), a centralized electromagnetic transient simulation model with a DC unloading device can be built, and the devices within the circles in the figure are the DC unloading devices. As shown in Figure 2(b), a distributed electromagnetic transient simulation model with a DC unloading device can be built, and the devices within the circles in the figure are the DC unloading devices. As shown in Figure 2(c) again, a distributed electromagnetic transient simulation model with a DC unloading device can be built, and the devices within the circles in the figure are the DC unloading devices.

[0105] Step S120: Determine multiple preset power parameters, and under each power parameter, perform fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after the IGBT or IGCT is turned on.

[0106] Specifically, for the multiple preset power parameters: with 0.1 p.u. as the segmentation unit, ten power parameters between 0 and 1 p.u. can be taken. The preset simulation time can be customized, such as 1 s. These ten power parameters can be used as simulation condition parameters for simulation. For example, take ten groups of 0.1 p.u., 0.2 p.u., ……, 1.0 p.u. as the condition parameters for simulation to obtain 10 groups of voltage, current, and switching information of the DC unloading device within 1 s after the IGBT or IGCT is turned on.

[0107] Step S130: Analyze the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters, determine the maximum total loss energy of the DC unloading device, and the target current information of the DC unloading device at the maximum total loss energy.

[0108] Specifically, according to the voltage and current of the IGBT or IGCT after the IGBT or IGCT of the DC unloading device is turned on, the timing waveforms of the voltage and current of the IGBT or IGCT can be drawn, as Figure 3 shown. Taking the current timing waveform of the IGBT or IGCT as a reference, according to the current information, turn-on information, and turn-off information of the DC unloading device, calculate the conduction loss, turn-on loss, and turn-off loss, and sum them up to obtain the total loss. Compare the total losses under multiple groups of condition parameters, and the maximum total loss can be taken as the maximum total loss energy of the DC unloading device.

[0109] Step S140: Use the pre-established thermal network simulation model with the DC unloading device, and combine the maximum total loss energy to calculate the reference maximum junction temperature of the DC unloading device.

[0110] Specifically, a thermal network simulation model can be established according to the parameters provided in the device manual of the IGBT or IGCT in the DC unloading device. The topological structure of the thermal network simulation model is as Figure 4 shown. The thermal network simulation model has three grounding paths. The first grounding path is connected with a heating power tester, the second grounding path is connected with a voltage tester, and multiple RC combinations are connected in series between the second and third grounding paths. The total number of RC combinations can be the order of the IGBT or IGCT, and the ambient temperature can be measured on the third grounding path.

[0111] Step S150: Calculate the target loss energy of the DC unloading device at the reference maximum junction temperature based on the target current information of the DC unloading device at the maximum total loss energy.

[0112] Specifically, while referring to the target current information of the DC unloading device at the maximum total loss energy, it is also necessary to refer to the on-state volt-ampere characteristic curves at 25°C and 125°C, and determine the threshold voltage and slope resistance at the reference maximum junction temperature through the difference method. Then, based on the threshold voltage and the slope resistance, calculate the conduction loss, turn-on loss, and turn-off loss at the reference maximum junction temperature, and sum them up to obtain the target loss energy of the DC unloading device at the reference maximum junction temperature.

[0113] Step S160: Determine the target maximum junction temperature of the DC unloading device based on the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0114] It can be understood that the heat of the DC unloading device is related to the total resistance value of its IGBT or IGCT. The larger the total resistance value, the more heat the DC unloading device emits, and vice versa.

[0115] The junction temperature calculation method of the DC unloading device provided in this embodiment creates an electromagnetic transient simulation model with the DC unloading device, determines various preset power parameters, and performs fault simulations on the electromagnetic transient simulation model under each power parameter to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time when the insulated gate bipolar transistor IGBT or integrated gate-commutated thyristor IGCT is put into operation. Analyze the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy. Use the pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy, calculate the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy, and determine the target maximum junction temperature of the DC unloading device based on the target loss energy and the total resistance value of all resistors in the thermal network simulation model. Thus, by obtaining the current and switch action information during the input process of the DC unloading device through electromagnetic transient simulation, there is no need to establish a three-dimensional model of IGBT or IGCT, which greatly reduces the workload and time for calculating the maximum total loss energy. Using the calculated reference maximum junction temperature as the iterative input to perform iterative calculations on the loss again makes the finally calculated target maximum junction temperature more accurate, thereby improving the efficiency of calculating the target maximum junction temperature of the DC unloading device.

[0116] In some embodiments of the present application, the process of the above step S120, determining multiple preset power parameters, and performing fault simulations on the electromagnetic transient simulation model under each power parameter to obtain current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or integrated gate-commutated thyristor (IGCT) is turned on, will be introduced. This process may include:

[0117] S1. Determine multiple power parameters for simulating the electromagnetic transient simulation model according to a preset unit power parameter.

[0118] Specifically, the unit power parameter can be customized, such as 0.1 p.u., and multiple power parameters can be determined at intervals of the unit power parameter, such as these ten power parameters: 0.1 p.u., 0.2 p.u., ……, 1.0 p.u.

[0119] S2. Under each power parameter, drive the electromagnetic transient simulation model to turn on the IGBT or IGCT in the DC unloading device when a three-phase short-circuit fault occurs, and after a preset simulation time after the DC unloading device is turned on, determine the current information, turn-on information, and turn-off information of the DC unloading device under this power parameter.

[0120] Specifically, the electromagnetic transient simulation model may include a sending-end AC system, and when a three-phase short-circuit fault occurs in the electromagnetic transient simulation model, it is a three-phase short-circuit fault in the sending-end AC system.

[0121] Among them, the turn-on information may be related to time, that is, the instantaneous turn-on information, and the turn-off information may be related to time, that is, the instantaneous turn-off information.

[0122] The method for calculating the junction temperature of the DC unloading device provided in this embodiment, by determining multiple power parameters and performing simulation tests under each power parameter, obtains multiple sets of current information, turn-on information, and turn-off information, without establishing a three-dimensional model of the IGBT or IGCT, and reduces the time for obtaining current information, turn-on information, and turn-off information.

[0123] In some embodiments of the present application, the process of the above step S130, analyzing the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters, determining the maximum total loss energy of the DC unloading device, and the target current information of the DC unloading device at the maximum total loss energy, will be introduced. This process may include:

[0124] S1. Calculate the conduction loss energy of the DC unloading device within the preset simulation time under each power parameter based on the current information of the DC unloading device, the first preset threshold voltage, and the first preset slope resistance.

[0125] Specifically, the on-state volt-ampere characteristic curve at 25°C can be obtained from the device manual of IGBT or IGCT, and thus the first preset threshold voltage is determined as the threshold voltage of IGBT or IGCT at 25°C, and the first preset slope resistance is the slope resistance of IGBT or IGCT at 25°C. Substituting the timing waveform of the current of IGBT or IGCT, the conduction loss energy of the DC unloading device within the preset simulation time can be calculated.

[0126] The conduction loss energy can be calculated by the following formula:

[0127]

[0128] where, I c (t) is the current information of the DC unloading device, V ce(th)_25℃ is the first preset threshold voltage, R _25℃ is the first preset slope resistance, t = 1.5 represents the start time of the preset simulation time, and t = 2.5 represents the end time of the preset simulation time.

[0129] S2. Calculate the turn-off loss energy of the DC unloading device within the preset simulation time under each power parameter based on the turn-off information of the DC unloading device under each power parameter.

[0130] Specifically, according to the turn-off information of the DC unloading device under each power parameter, the number of turn-offs of the DC unloading device within the preset simulation time under each power parameter can be determined, so as to determine the loss energy of each turn-off of the DC unloading device under each power parameter. Finally, the loss energies of each turn-off of the DC unloading device under each power parameter can be accumulated to obtain the turn-off loss energy of the DC unloading device within the preset simulation time.

[0131] For example, assuming the preset simulation time is from the 1.5th second to the 2.5th second, then the turn-off information between the 1.5th second and the 2.5th second can be determined on the timing waveform of the current of IGBT or IGCT, the energy generated by each turn-off action can be determined, and the energy generated by each turn-off action between the 1.5th second and the 2.5th second can be accumulated to obtain the turn-off loss energy.

[0132] S3. Calculate the turn-on loss energy of the DC unloading device within the preset simulation time under each power parameter based on the turn-on information of the DC unloading device under each power parameter.

[0133] Specifically, according to the turn-on information of the DC unloading device under each power parameter, the number of turn-ons of the DC unloading device under each power parameter within the preset simulation time can be determined, so as to determine the loss energy of each turn-on of the DC unloading device under each power parameter. Finally, the loss energy of each turn-on of the DC unloading device under each power parameter can be accumulated to obtain the turn-off loss energy of the DC unloading device within the preset simulation time.

[0134] For example, assuming that the preset simulation time is from 1.5 s to 2.5 s, then the turn-on information between 1.5 s and 2.5 s can be determined from the timing waveform of the current of the IGBT or IGCT, the energy generated by each turn-on action can be determined, and the turn-on loss energy can be obtained by accumulating the energy generated by each turn-on action between 1.5 s and 2.5 s.

[0135] S4. Add up the conduction loss energy, the turn-off loss energy, and the turn-on loss energy under each power parameter to obtain the total loss energy of the DC unloading device under this power parameter.

[0136] Specifically, the total loss energy of the DC unloading device under each power parameter can be expressed by the following formula:

[0137] E loss (n)=E on (n)+E switch off (n)+E switch on (n)

[0138] Wherein, E on (n) is the conduction loss energy of the DC unloading device under each power parameter, E switch off (n) is the turn-off loss energy of the DC unloading device under each power parameter, and E switch on (n) is the turn-on loss energy of the DC unloading device under each power parameter.

[0139] S5. Determine the maximum total loss energy among the total loss energies of the DC unloading device under various power parameters, and determine the current information of the DC unloading device under the power parameter corresponding to the maximum total loss energy as the target current information.

[0140] For example, assuming that there are a total of 10 power parameters, then the maximum total loss energy is:

[0141] E loss_max =MAX{E loss (1), E loss (2), E loss (3),..., E loss(10)}

[0142] Assume that the maximum total loss energy is E loss_max = E loss (3), then the target current information is E loss (3) The current information of the DC unloading device under the corresponding power parameter (0.3 p.u.).

[0143] The method for calculating the junction temperature of the DC unloading device provided in this embodiment obtains the total loss energy of the DC unloading device under each power parameter by calculating the conduction loss energy, turn-off loss energy, and turn-on loss energy of the DC unloading device, so the maximum total loss energy of the DC unloading device can be determined.

[0144] In some embodiments of the present application, the process of step S140 above, using the pre-established thermal network simulation model with the DC unloading device, and calculating the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy, is introduced. This process may include:

[0145] S1. Divide the maximum total loss energy by the preset simulation time to obtain the heating power of the DC unloading device.

[0146] Specifically, the heating power of the DC unloading device can be calculated using the following formula:

[0147]

[0148] Among them, E loss_max is the maximum total loss energy of the DC unloading device, and T is the preset simulation time.

[0149] S2. Calculate the reference maximum junction temperature of the DC unloading device according to the heating power and the total resistance value of each resistor in the pre-established thermal network simulation model.

[0150] Specifically, the reference maximum junction temperature of the DC unloading device can be calculated using the following formula:

[0151]

[0152] Among them, T a is the ambient temperature measured by the third grounded path in the thermal network simulation model, R i is the resistor in the RC combination in the thermal network simulation model, n is the order of the IGBT or IGCT, and P loss_max is the heating power of the DC unloading device.

[0153] The method for calculating the junction temperature of the DC load shedding device provided in this embodiment obtains the heating power of the DC load shedding device by dividing the maximum total loss energy by the preset simulation time, and calculates the reference maximum junction temperature of the DC load shedding device according to the heating power and the total resistance values of each resistor in the pre-established thermal network simulation model for subsequent iterative calculation.

[0154] In some embodiments of the present application, the process of step S150, calculating the target loss energy of the DC load shedding device at the reference maximum junction temperature through the target current information of the DC load shedding device at the maximum total loss energy, is introduced. This process may include:

[0155] S1. Calculate the target turn-off loss energy and target turn-on loss energy of the DC load shedding device at the reference maximum junction temperature.

[0156] Specifically, the process of calculating the target turn-off loss energy and target turn-on loss energy of the DC load shedding device at the reference maximum junction temperature may include:

[0157] S11. Determine the turn-off loss at the first reference temperature according to the existing relationship curve between turn-off energy and turn-off current at the first reference temperature.

[0158] Among them, the first reference temperature may be 25°C, and the turn-off loss at 25°C can be determined through the relationship curve between turn-off energy and turn-off current at 25°C.

[0159] S12. Determine the turn-off loss at the second reference temperature according to the existing relationship curve between turn-off energy and turn-off current at the second reference temperature.

[0160] Among them, the second reference temperature may be 125°C, and the turn-off loss at 125°C can be determined through the relationship curve between turn-off energy and turn-off current at 125°C.

[0161] S13. Determine the turn-on loss at the first reference temperature according to the existing relationship curve between turn-on energy and turn-on current at the first reference temperature.

[0162] Among them, the first reference temperature may be 25°C, and the turn-on loss at 25°C can be determined through the relationship curve between turn-on energy and turn-on current at 25°C.

[0163] S14. Determine the turn-on loss at the second reference temperature according to the existing relationship curve between turn-on energy and turn-on current at the second reference temperature.

[0164] Among them, the second reference temperature may be 125°C, and the turn-on loss at 125°C can be determined through the relationship curve between turn-on energy and turn-on current at 125°C.

[0165] S15. Calculate the target turn-off loss energy and target turn-on loss energy of the DC unloading device according to the first reference temperature, the second reference temperature, the turn-off loss and turn-on loss at the first reference temperature, the turn-off loss and turn-on loss at the second reference temperature, and the reference maximum junction temperature.

[0166] Specifically, the target turn-off loss energy of the DC unloading device can be calculated by the following formula:

[0167]

[0168] where T vj is the reference maximum junction temperature, E switch off_125℃ is the turn-off loss at the second reference temperature, and E switch off_25℃ is the turn-off loss at the first reference temperature.

[0169] The target turn-on loss energy of the DC unloading device can be calculated by the following formula:

[0170]

[0171] where T vj is the reference maximum junction temperature, E switch on_125℃ is the turn-on loss at the second reference temperature, and E switch on_25℃ is the turn-on loss at the first reference temperature.

[0172] S2. Calculate the target threshold voltage of the DC unloading device at the reference maximum junction temperature by using the first preset threshold voltage and the second preset threshold voltage.

[0173] Among them, the second preset threshold voltage can be the threshold voltage of IGBT or IGCT at 125 °C.

[0174] Specifically, the target threshold voltage of the DC unloading device at the reference maximum junction temperature can be calculated by the following formula:

[0175]

[0176] where T vj is the reference maximum junction temperature, V ce(th)_125℃ is the second preset threshold voltage, and V ce(th)_25℃ is the first preset threshold voltage.

[0177] S3. Calculate the target slope resistance of the DC unloading device at the reference maximum junction temperature by using the first preset slope resistance and the second preset slope resistance.

[0178] Among them, the second preset slope resistance can be the slope resistance of IGBT or IGCT at 125 °C.

[0179] Specifically, the target slope resistance of the DC unloading device at the reference maximum junction temperature can be calculated using the following formula:

[0180]

[0181] Among them, T vj is the reference maximum junction temperature, R _125℃ is the second preset slope resistance, and R _25℃ is the first preset slope resistance.

[0182] S4. Calculate the target conduction loss of the DC unloading device at the reference maximum junction temperature according to the target current information, the target threshold voltage, the target slope resistance, and the preset simulation time.

[0183] Specifically, the target conduction loss of the DC unloading device at the reference maximum junction temperature can be calculated using the following formula:

[0184]

[0185] Among them, I c (t) is the target current information, V ce(th)_Tvj is the target threshold voltage, R _Tvj is the target slope resistance, t = 1.5 indicates that the start time of the preset simulation time is 1.5 s, and t = 2.5 indicates that the start time of the preset simulation time is 2.5 s.

[0186] S5. Accumulate the target conduction loss energy, the target turn-off loss energy, and the target turn-on loss energy to obtain the target loss energy of the DC unloading device.

[0187] In some embodiments of the present application, the process of step S160, determining the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model, is introduced. This process may include:

[0188] S1. Divide the target loss energy by the preset simulation time to obtain the target heating power of the DC unloading device.

[0189] Specifically, the target heating power of the DC unloading device can be calculated using the following formula:

[0190]

[0191] Among them, E loss_Tvjis the target loss energy, and T is the preset simulation time.

[0192] S2. Calculate the target maximum junction temperature of the DC unloading device based on the target heating power and the total resistance value of each resistor in the thermal network simulation model.

[0193] Specifically, the target maximum junction temperature of the DC unloading device can be calculated using the following formula:

[0194]

[0195] where T a is the ambient temperature measured by the third grounded path in the thermal network simulation model, R i is the resistor in the RC combination in the thermal network simulation model, n is the order of the IGBT or IGCT, and P' loss_max is the target heating power of the DC unloading device.

[0196] Next, the device for calculating the junction temperature of the DC unloading device provided in the embodiments of the present application will be described. The device for calculating the junction temperature of the DC unloading device described below can be correspondingly referred to the method for calculating the junction temperature of the DC unloading device described above.

[0197] See Figure 5 , Figure 5 which is a schematic structural diagram of a device for calculating the junction temperature of a DC unloading device disclosed in the embodiments of the present application.

[0198] As Figure 5 shown, the device may include:

[0199] A model creation unit 11 for creating an electromagnetic transient simulation model with a DC unloading device;

[0200] A model simulation unit 12 for determining a variety of preset power parameters and, under each power parameter, performing a fault simulation on the electromagnetic transient simulation model to obtain current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time when an insulated gate bipolar transistor IGBT or an integrated gate-commutated thyristor IGCT is turned on;

[0201] A loss information determination unit 13 for analyzing the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy;

[0202] A reference junction temperature calculation unit 14 for using a pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy;

[0203] A target loss energy calculation unit 15 is configured to calculate the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy.

[0204] A target junction temperature determination unit is configured to determine the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0205] Optionally, the model simulation unit includes:

[0206] A power parameter determination unit is configured to determine a variety of power parameters for simulating the electromagnetic transient simulation model according to preset unit power parameters.

[0207] A power test parameter determination unit is configured to drive the IGBT or IGCT in the DC unloading device when a three-phase short circuit fault occurs in the electromagnetic transient simulation model under each power parameter, and determine the current information, turn-on information, and turn-off information of the DC unloading device under this power parameter after a preset simulation time after the DC unloading device is put into operation.

[0208] Optionally, the loss information determination unit includes:

[0209] A first loss information determination subunit is configured to calculate the conduction loss energy of the DC unloading device within the preset simulation time under this power parameter based on the current information of the DC unloading device, a first preset threshold voltage, and a first preset slope resistance under each power parameter.

[0210] A second loss information determination subunit is configured to calculate the turn-off loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-off information of the DC unloading device under each power parameter.

[0211] A third loss information determination subunit is configured to calculate the turn-on loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-on information of the DC unloading device under each power parameter.

[0212] A fourth loss information determination subunit is configured to accumulate the conduction loss energy, the turn-off loss energy, and the turn-on loss energy under each power parameter to obtain the total loss energy of the DC unloading device under this power parameter.

[0213] The fifth loss information determining subunit is configured to determine the maximum total loss energy among the total loss energies of the DC unloading device under various power parameters, and determine the current information of the DC unloading device under the power parameters corresponding to the maximum total loss energy as the target current information.

[0214] Optionally, the second loss information determining subunit includes:

[0215] The turn-off times determining unit is configured to determine the turn-off times of the DC unloading device within the preset simulation time under each power parameter according to the turn-off information of the DC unloading device under each power parameter;

[0216] The turn-off loss energy determining unit is configured to determine the loss energy of each turn-off of the DC unloading device under each power parameter;

[0217] The turn-off loss energy accumulating unit is configured to accumulate the loss energies of each turn-off of the DC unloading device under each power parameter as the turn-off loss energy of the DC unloading device within the preset simulation time.

[0218] Optionally, the third loss information determining subunit includes:

[0219] The turn-on times determining unit is configured to determine the turn-on times of the DC unloading device within the preset simulation time under each power parameter according to the turn-on information of the DC unloading device under each power parameter;

[0220] The turn-on loss energy determining unit is configured to determine the loss energy of each turn-on of the DC unloading device under each power parameter;

[0221] The turn-on loss energy accumulating unit is configured to accumulate the loss energies of each turn-on of the DC unloading device under each power parameter as the turn-off loss energy of the DC unloading device within the preset simulation time.

[0222] Optionally, the reference junction temperature calculating unit includes:

[0223] The heating power calculating unit is configured to divide the maximum total loss energy by the preset simulation time to obtain the heating power of the DC unloading device;

[0224] The reference maximum junction temperature calculating unit is configured to calculate the reference maximum junction temperature of the DC unloading device according to the heating power and the total resistance value of each resistor in the pre-established thermal network simulation model.

[0225] Optionally, the target loss energy calculating unit includes:

[0226] The first target loss energy calculation unit is configured to calculate the target turn-off loss energy and the target turn-on loss energy of the DC unloading device at the reference maximum junction temperature;

[0227] The second target loss energy calculation unit is configured to calculate the target threshold voltage of the DC unloading device at the reference maximum junction temperature by using the first preset threshold voltage and the second preset threshold voltage;

[0228] The third target loss energy calculation unit is configured to calculate the target slope resistance of the DC unloading device at the reference maximum junction temperature by using the first preset slope resistance and the second preset slope resistance;

[0229] The fourth target loss energy calculation unit is configured to calculate the target conduction loss of the DC unloading device at the reference maximum junction temperature according to the target current information, the target threshold voltage, the target slope resistance, and the preset simulation time;

[0230] The fifth target loss energy calculation unit is configured to accumulate the target conduction loss energy, the target turn-off loss energy, and the target turn-on loss energy to obtain the target loss energy of the DC unloading device.

[0231] Optionally, the first target loss energy calculation unit includes:

[0232] The first turn-off loss determination unit is configured to determine the turn-off loss at the first reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the first reference temperature;

[0233] The second turn-off loss determination unit is configured to determine the turn-off loss at the second reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the second reference temperature;

[0234] The first turn-on loss determination unit is configured to determine the turn-on loss at the first reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the first reference temperature;

[0235] The second turn-on loss determination unit is configured to determine the turn-on loss at the second reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the second reference temperature;

[0236] The target turn-on loss energy calculation unit is configured to calculate the target turn-off loss energy and the target turn-on loss energy of the DC unloading device according to the first reference temperature, the second reference temperature, the turn-off loss and turn-on loss at the first reference temperature, the turn-off loss and turn-on loss at the second reference temperature, and the reference maximum junction temperature.

[0237] Optionally, the target junction temperature determination unit includes:

[0238] A first target junction temperature determination subunit, configured to divide the target loss energy by the preset simulation time to obtain the target heating power of the DC unloading device;

[0239] A second target junction temperature determination subunit, configured to calculate the target maximum junction temperature of the DC unloading device based on the target heating power and the total resistance value of each resistor in the thermal network simulation model.

[0240] The device for calculating the junction temperature of the DC unloading device provided by the embodiments of the present application can be applied to devices for calculating the junction temperature of the DC unloading device, such as terminals: mobile phones, computers, etc. Optionally, Figure 6 shows the hardware structure block diagram of the xx device. Refer to Figure 6 , the hardware structure of the device for calculating the junction temperature of the DC unloading device may include: at least one processor 1, at least one communication interface 2, at least one memory 3, and at least one communication bus 4;

[0241] In the embodiments of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 complete communication with each other through the communication bus 4;

[0242] The processor 1 may be a central processing unit CPU, or a specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention, etc.;

[0243] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory;

[0244] Wherein, the memory stores a program, and the processor can call the program stored in the memory. The program is used for:

[0245] Create an electromagnetic transient simulation model with a DC unloading device;

[0246] Determine a variety of preset power parameters, and under each power parameter, perform a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor IGBT or an integrated gate-commutated thyristor IGCT is put into operation;

[0247] Analyze the current information, turn-on information, and turn-off information of the DC load shedding device for various power parameters, determine the maximum total loss energy of the DC load shedding device, and the target current information of the DC load shedding device at the maximum total loss energy;

[0248] Utilize the pre-established thermal network simulation model with the DC load shedding device, and calculate the reference maximum junction temperature of the DC load shedding device in combination with the maximum total loss energy;

[0249] Calculate the target loss energy of the DC load shedding device at the reference maximum junction temperature through the target current information of the DC load shedding device at the maximum total loss energy;

[0250] Determine the target maximum junction temperature of the DC load shedding device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0251] Optionally, the refinement function and expansion function of the program can refer to the above description.

[0252] The embodiment of the present application also provides a storage medium, which can store a program suitable for execution by a processor, and the program is used for:

[0253] Create an electromagnetic transient simulation model with a DC load shedding device;

[0254] Determine a variety of preset power parameters, and perform fault simulations on the electromagnetic transient simulation model under each power parameter to obtain the current information, turn-on information, and turn-off information of the DC load shedding device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or an integrated gate-commutated thyristor (IGCT) is put into operation;

[0255] Analyze the current information, turn-on information, and turn-off information of the DC load shedding device for various power parameters, determine the maximum total loss energy of the DC load shedding device, and the target current information of the DC load shedding device at the maximum total loss energy;

[0256] Utilize the pre-established thermal network simulation model with the DC load shedding device, and calculate the reference maximum junction temperature of the DC load shedding device in combination with the maximum total loss energy;

[0257] Calculate the target loss energy of the DC load shedding device at the reference maximum junction temperature through the target current information of the DC load shedding device at the maximum total loss energy;

[0258] Determine the target maximum junction temperature of the DC load shedding device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

[0259] Optionally, the refinement function and expansion function of the program may refer to the description above.

[0260] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0261] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0262] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the junction temperature of a DC load shedding device, characterized in that including: creating an electromagnetic transient simulation model with a DC unloading device; determining a variety of preset power parameters, and under each power parameter, performing a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or an integrated gate-commutated thyristor (IGCT) is put into operation; analyzing the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy; using a pre-established thermal network simulation model with the DC unloading device to calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy; calculating the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy; determining the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

2. The method according to claim 1, wherein The determining a variety of preset power parameters, and under each power parameter, performing a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an IGBT or an IGCT is put into operation includes: determining a variety of power parameters for simulating the electromagnetic transient simulation model according to a preset unit power parameter; under each power parameter, driving the electromagnetic transient simulation model to put the IGBT or IGCT in the DC unloading device into operation when a three-phase short-circuit fault occurs, and after a preset simulation time after the DC unloading device is put into operation, determining the current information, turn-on information, and turn-off information of the DC unloading device under this power parameter.

3. The method according to claim 1, wherein The analyzing the current information, turn-on information, and turn-off information of the DC unloading device under various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy includes: calculating the conduction loss energy of the DC unloading device within the preset simulation time under this power parameter based on the current information, a first preset threshold voltage, and a first preset slope resistance of the DC unloading device under each power parameter; calculating the turn-off loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-off information of the DC unloading device under each power parameter; calculating the turn-on loss energy of the DC unloading device within the preset simulation time under this power parameter based on the turn-on information of the DC unloading device under each power parameter; accumulating the conduction loss energy, the turn-off loss energy, and the turn-on loss energy under each power parameter to obtain the total loss energy of the DC unloading device under this power parameter; Determine the maximum total loss energy in the total loss energy of the DC unloading device under various power parameters, and determine the current information of the DC unloading device under the power parameters corresponding to the maximum total loss energy as the target current information.

4. The method according to claim 3, characterized in that, Based on the turn-off information of the DC unloading device under each power parameter, calculate the turn-off loss energy of the DC unloading device within the preset simulation time under this power parameter, including: According to the turn-off information of the DC unloading device under each power parameter, determine the number of turn-offs of the DC unloading device within the preset simulation time under each power parameter; Determine the loss energy of each turn-off of the DC unloading device under each power parameter; Accumulate the loss energies of each turn-off of the DC unloading device under each power parameter, which is the turn-off loss energy of the DC unloading device within the preset simulation time.

5. The method according to claim 3, wherein Based on the turn-on information of the DC unloading device under each power parameter, calculate the turn-on loss energy of the DC unloading device within the preset simulation time under this power parameter, including: According to the turn-on information of the DC unloading device under each power parameter, determine the number of turn-ons of the DC unloading device within the preset simulation time under each power parameter; Determine the loss energy of each turn-on of the DC unloading device under each power parameter; Accumulate the loss energies of each turn-on of the DC unloading device under each power parameter, which is the turn-off loss energy of the DC unloading device within the preset simulation time.

6. The method according to claim 1, characterized in that, Using the pre-established thermal network simulation model with the DC unloading device, calculate the reference maximum junction temperature of the DC unloading device in combination with the maximum total loss energy, including: Divide the maximum total loss energy by the preset simulation time to obtain the heating power of the DC unloading device; Calculate the reference maximum junction temperature of the DC unloading device according to the heating power and the total resistance value of each resistor in the pre-established thermal network simulation model.

7. The method according to claim 3, wherein Based on the target current information of the DC unloading device at the maximum total loss energy, calculate the target loss energy of the DC unloading device at the reference maximum junction temperature, including: Calculate the target turn-off loss energy and target turn-on loss energy of the DC unloading device at the reference maximum junction temperature; Calculate the target threshold voltage of the DC unloading device at the reference maximum junction temperature using the first preset threshold voltage and the second preset threshold voltage; Calculate the target slope resistance of the DC unloading device at the reference maximum junction temperature using the first preset slope resistance and the second preset slope resistance; According to the target current information, the target threshold voltage, the target slope resistance, and the preset simulation time, calculate the target conduction loss energy of the DC unloading device at the reference maximum junction temperature; Accumulate the target conduction loss energy, the target turn-off loss energy, and the target turn-on loss energy to obtain the target loss energy of the DC unloading device.

8. The method according to claim 7, wherein Calculating the target turn-off loss energy and target turn-on loss energy of the DC unloading device at the reference maximum junction temperature includes: Determining the turn-off loss at the first reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the first reference temperature; Determining the turn-off loss at the second reference temperature according to the existing relationship curve between the turn-off energy and the turn-off current at the second reference temperature; Determining the turn-on loss at the first reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the first reference temperature; Determining the turn-on loss at the second reference temperature according to the existing relationship curve between the turn-on energy and the turn-on current at the second reference temperature; Calculating the target turn-off loss energy and target turn-on loss energy of the DC unloading device according to the first reference temperature, the second reference temperature, the turn-off loss and turn-on loss at the first reference temperature, the turn-off loss and turn-on loss at the second reference temperature, and the reference maximum junction temperature.

9. The method according to claim 1, characterized in that, Determining the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model includes: Dividing the target loss energy by the preset simulation time to obtain the target heating power of the DC unloading device; Calculating the target maximum junction temperature of the DC unloading device based on the target heating power and the total resistance value of each resistor in the thermal network simulation model.

10. A device for calculating the junction temperature of a DC load shedding device, characterized in that, Including: A model creation unit for creating an electromagnetic transient simulation model with a DC unloading device; A model simulation unit for determining a variety of preset power parameters and, under each power parameter, performing a fault simulation on the electromagnetic transient simulation model to obtain the current information, turn-on information, and turn-off information of the DC unloading device after a preset simulation time after an insulated gate bipolar transistor (IGBT) or an integrated gate-commutated thyristor (IGCT) is put into operation; A loss information determination unit for analyzing the current information, turn-on information, and turn-off information of the DC unloading device with various power parameters to determine the maximum total loss energy of the DC unloading device and the target current information of the DC unloading device at the maximum total loss energy; A reference junction temperature calculation unit for using a pre-established thermal network simulation model with the DC unloading device and combining the maximum total loss energy to calculate the reference maximum junction temperature of the DC unloading device; A target loss energy calculation unit for calculating the target loss energy of the DC unloading device at the reference maximum junction temperature through the target current information of the DC unloading device at the maximum total loss energy; A target junction temperature determination unit for determining the target maximum junction temperature of the DC unloading device according to the target loss energy and the total resistance value of all resistors in the thermal network simulation model.

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