Method and device for increasing rated current breaking times of direct-current solid-state circuit breaker and application of method and device

Abstract

The invention provides a method and device for increasing the rated current breaking frequency of a direct-current solid-state circuit breaker and application of the method and device, and aims to solve the problem that the breaking frequency of an existing direct-current solid-state circuit breaker is limited due to over-temperature damage caused by performance degradation after multiple current impacts of a piezoresistor and difficult measurement of the junction temperature of a power device. The system comprises a junction temperature prediction module based on a physical information neural network, an auxiliary energy absorption module and a power device voltage clamping module. The junction temperature prediction module is used for accurately predicting the junction temperature of the power device in real time by fusing a physical thermal model and a neural network; the voltage clamping module suppresses turn-off overvoltage; and the auxiliary energy absorption module is started when the junction temperature is close to the limit to absorb residual energy. According to the design, turn-off energy is reasonably distributed, the impact frequency and strength of the piezoresistor are reduced, the service life of the piezoresistor is remarkably prolonged (for example, the service life is prolonged by about 10 times under the impact of 200A), then the rated breaking frequency of the solid-state circuit breaker is greatly increased, and the solid-state circuit breaker is low in cost, high in reliability and suitable for scenes such as a direct-current power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to the circuit topology design of DC solid-state circuit breaker, and especially to the technology for improving the rated current breaking times of DC solid-state circuit breaker. BACKGROUND

[0002] As a key device in the field of power electronics, the DC solid-state circuit breaker realizes the turn-on, breaking and protection of the circuit through power semiconductor devices (such as IGBT, SiC MOSFET, etc.) and their control circuit. Compared with the traditional mechanical circuit breaker, it has the advantages of high-speed breaking, arcless breaking, long theoretical service life (hundreds of thousands of times), etc., and has broad application prospects in DC power grid, new energy system, etc.

[0003] However, the actual breaking times of the existing DC solid-state circuit breaker are still significantly limited, mainly in two aspects: on the one hand, the energy absorption circuit is usually composed of a varistor and an RCD circuit. After being subjected to multiple current surges, the varistor will have performance degradation problems such as increased leakage current and decreased energy absorption capacity, which becomes the core bottleneck limiting the service life of the circuit breaker; on the other hand, the power device needs to withstand a large amount of energy during the turn-off process, but its junction temperature is difficult to measure directly. If the junction temperature exceeds the limit, the device will be damaged, further reducing the breaking reliability.

[0004] The above defects seriously restrict the rated breaking times and practical application value of the DC solid-state circuit breaker, and therefore there is an urgent need for a technical solution that can optimize energy distribution and device protection in coordination. SUMMARY

[0005] The embodiments of the present application provide a method and device for improving the rated current breaking times of a DC solid-state circuit breaker and its application, which aims to solve the problems that the breaking times of the existing DC solid-state circuit breaker are limited by the performance degradation of the varistor after being subjected to multiple current surges, and the over-temperature damage caused by the difficulty in real-time monitoring of the junction temperature of the power device.

[0006] The core technology of the present application is mainly to monitor the junction temperature of the power device in real time through the junction temperature prediction module based on the physical information neural network, and to distribute the turn-off energy in coordination with the auxiliary energy absorption module and the voltage clamping module (preferentially absorbing energy by the power device, and starting auxiliary energy absorption when the junction temperature approaches the limit), so as to improve the rated current breaking times of the DC solid-state circuit breaker.

[0007] In a first aspect, the present application provides a device for improving the rated current breaking times of a DC solid-state circuit breaker, comprising a power device, which is an IGBT or a SiC MOSFET, and further comprising: a junction temperature prediction module based on a physical information neural network, an auxiliary energy absorption module, and a power device voltage clamping module; The junction temperature prediction module is electrically connected with the power device, and is used for monitoring the loss of the power device when the solid-state switch is turned off, and predicting the junction temperature of the power device in real time through an embedded physical information neural network; The power device voltage clamping module is associated with the drive side of the power device, and is used for suppressing overvoltage during the turn-off process of the solid-state switch, and preventing the power device from being damaged due to overvoltage; The auxiliary energy absorption module is connected in parallel with the power device, and is connected with the junction temperature prediction module, when the junction temperature prediction module predicts that the junction temperature of the power device is close to the preset limit value, the auxiliary energy absorption module responds and starts to absorb the residual energy in the turn-off process.

[0008] Further, the junction temperature prediction module comprises: A voltage and current sensing unit is used to collect the operating parameters of the power device; A processing unit is embedded with a physical information neural network model, the physical information neural network model fuses a physical thermal model of the power device and a neural network correction term, to fit the change of the thermal characteristics of the power device after aging, and outputs the real-time predicted junction temperature.

[0009] Further, the input of the physical information neural network model includes the loss, ambient temperature and operating voltage and current parameters of the power device, and the output is the prediction result related to the junction temperature of the power device; the neural network correction term is used to compensate for the change of the thermal resistance network parameters caused by the aging of the power device, and the weight β of the neural network correction term is updated in real time through an online learning algorithm.

[0010] Further, the auxiliary energy absorption module comprises: A voltage-dependent resistor, a thyristor and a voltage equalization resistor; The voltage equalization resistor is used to balance the voltage across the voltage-dependent resistor and the thyristor; The on-off state of the thyristor is triggered by the control signal output by the junction temperature prediction module, and after being turned on, the voltage-dependent resistor is connected to the circuit to absorb energy.

[0011] Further, the voltage-dependent resistor satisfies: the voltage at 100mA leakage current is greater than the bus voltage, the residual voltage is less than the maximum withstand voltage of the power device, and the energy absorption capacity is greater than the total energy in the turn-off process.

[0012] Further, the power device voltage clamping module is an active clamping circuit, comprising a transient voltage suppression diode in series, and the transient voltage suppression diode is adjusted through voltage feedback, to limit the voltage rise slope and peak value of the power device during the turn-off process.

[0013] In a second aspect, the application provides a method for improving the rated current breaking times of a direct current solid-state circuit breaker, using the above-mentioned device, and specifically comprising the following steps: S1. When the solid-state switch receives a turn-off signal, the power device starts to turn off, and a synchronous start power device voltage clamping module is started to suppress overvoltage to protect the power device; S2. A junction temperature prediction based on a physical information neural network is started to monitor the loss of the power device in real time and predict the junction temperature thereof; S3. If the predicted junction temperature is not close to a preset limit value, the turn-off energy is absorbed by the power device alone; if the predicted junction temperature is close to the preset limit value, an auxiliary energy absorption module is triggered to start, and the remaining energy is absorbed by the auxiliary energy absorption module; S4. After the auxiliary energy absorption module finishes absorbing energy, it is automatically turned off to complete the turn-off process. The condition for the automatic turn-off of the auxiliary energy absorption module is that the leakage current of the voltage-dependent resistor is reduced to be less than the holding current of the thyristor, and the thyristor is turned off.

[0014] Further, in step S2, the junction temperature prediction based on the physical information neural network comprises: Real-time operating parameters of the power device are collected through a voltage and current sensor; The operating parameters are input into a model that fuses a physical thermal model and a neural network correction term, and the model outputs a real-time junction temperature prediction value by compensating for changes in the thermal resistance network caused by aging of the power device through the neural network correction term.

[0015] Further, in step S3, the predicted junction temperature close to the preset limit value specifically refers to that the predicted junction temperature reaches a preset proportion of the limit junction temperature of the power device, and the preset proportion is 80%-90%. After the auxiliary energy absorption module is started, the current is commutated from the power device to the voltage-dependent resistor of the auxiliary energy absorption module, the voltage-dependent resistor absorbs the remaining energy, and voltage spikes are eliminated through the power device voltage clamping module during the commutation process.

[0016] In a third aspect, the present application provides an electronic device comprising a memory and a processor, the memory storing a computer program, and the processor being configured to run the computer program to execute the method for improving the breaking times of a DC solid-state circuit breaker according to the above.

[0017] In a fourth aspect, the present application provides a readable storage medium, the readable storage medium storing a computer program, and the computer program comprising program codes for controlling a process to execute the process, and the process comprising the method for improving the breaking times of a DC solid-state circuit breaker according to the above.

[0018] The main contributions and innovative points of the present application are as follows: 1. Significantly increase the number of breaking times: By precisely controlling the starting time of the auxiliary energy absorption module (only start when the junction temperature of the power device approaches the limit), reduce the number of current impact and intensity (single impact energy is reduced by about 50%) that the voltage-dependent resistor bears, combined with the voltage-dependent resistor decay characteristics (such as 200A impact, the service life is increased by about 10 times), greatly prolong its service life, and then improve the overall breaking times of the circuit breaker.

[0019] 2. Reliable protection of power devices: The junction temperature prediction module based on physical information neural network can correct the thermal model error caused by IGBT aging in real time, accurately predict the junction temperature and reserve a safety margin, cooperate with the voltage clamping module to suppress overvoltage, and avoid damage to the device due to overtemperature or overvoltage.

[0020] 3. Optimize energy distribution efficiency: Make full use of the complementary advantages of semiconductor devices (material recovery is high, long service life) and voltage-dependent resistors (energy absorption ability is strong), realize reasonable distribution of shutdown energy, and improve device utilization.

[0021] 4. Low cost and easy to implement: Without the need for additional high-cost components, performance improvement is achieved through the collaborative design of algorithms and circuit topology, and is easy to engineer and apply.

[0022] The details of one or more embodiments of the present application are presented in the following drawings and description, so that other features, objects and advantages of the present application are more apparent. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a schematic diagram of a direct current circuit breaker according to an embodiment of the present application; Figure 2 is a flowchart of a method for improving the rated current breaking times of a direct current solid state circuit breaker according to an embodiment of the present application; Figure 3 is a structure diagram of a junction temperature prediction module according to an embodiment of the present application; Figure 4 is a schematic diagram of an IGBT thermal model according to an embodiment of the present application; Figure 5 is a neural network training flowchart according to an embodiment of the present application; Figure 6 is a solid state circuit breaker design circuit diagram according to an embodiment of the present application; Figure 7 is a solid state circuit breaker shutdown process diagram according to an embodiment of the present application; Figure 8is a pressure sensitive resistor decay curve diagram of FTR40D112KJ model according to an embodiment of the present application; Figure 9 is a hardware structure schematic diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The following description is made with reference to the accompanying drawings in which like reference numerals refer to like elements, and the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Unless otherwise noted, the description of an embodiment below is not meant to imply that the described embodiment is the only way in which the described embodiment can be implemented. Rather, the description of an embodiment is meant to include all ways of implementing the described embodiment that are functionally equivalent, unless otherwise noted.

[0025] It should be noted that the steps of the methods in other embodiments are not necessarily performed in the order shown and described in this specification. In some other embodiments, the steps of the methods can include more or fewer steps than those described in this specification. In addition, a single step described in this specification can be split into multiple steps in other embodiments; and multiple steps described in this specification can be combined into a single step in other embodiments.

[0026] The breaking number of the existing DC solid-state circuit breaker is limited by the performance degradation of the pressure sensitive resistor after multiple current impacts and the over-temperature damage caused by the difficulty in real-time monitoring of the junction temperature of the power device.

[0027] Based on this, the present application solves the problems existing in the prior art based on a physical information neural network.

[0028] Embodiment one The present application aims to provide a device for improving the rated current breaking number of a DC solid-state circuit breaker, and specifically refers to Figure 1 The present application mainly includes three parts: the first part is a junction temperature prediction module based on a physical information neural network, the second part is an auxiliary energy absorption module (also referred to as a power absorption module), and the third part is a power device voltage clamping module (also referred to as a voltage clamping module).

[0029] As Figure 2As shown, the main switching device (power device, IGBT or SiC MOSFET) is connected in the circuit, and its breaking is determined by the control signal. The voltage clamping circuit and the control signal are both connected to the drive side, and the overvoltage is clamped by voltage feedback. The energy monitoring module based on physical information neural network is connected to the main circuit. The calculation of turn-off energy starts after the generation of turn-off overvoltage, and the junction temperature is predicted in real time. The auxiliary energy absorption module is connected in parallel with the main power device, and the auxiliary power device absorbs the residual energy in the turn-off process after receiving the signal from the monitoring module, preventing the IGBT from being damaged by high junction temperature.

[0030] In this embodiment, the auxiliary energy absorption module (power absorption module) is composed of two voltage-sharing resistors, a thyristor and a pressure-sensitive resistor. The voltage-sharing resistors are used to evenly distribute the voltage of the pressure-sensitive resistor and the thyristor, so that they do not start under normal circumstances. When the energy monitoring module gives a start signal, the power absorption module starts, and the auxiliary power device absorbs energy. Preferably, the pressure-sensitive resistor is selected to satisfy the following formula:

[0031] wherein, : the nominal voltage of the pressure-sensitive resistor under 100mA leakage current (manufacturer's test value, reflecting the "turn-on threshold"); : the rated operating voltage of the DC bus (such as 500V, 800V). When the bus voltage , the leakage current of the pressure-sensitive resistor is much smaller than 100mA (usually in the order of μA), showing a high resistance state (almost open circuit), which does not continuously consume bus energy and does not affect the normal operation of the main circuit. For example, when the bus voltage V line =800V, the pressure-sensitive resistor is selected to have a leakage current of 100mA, a voltage V 100mA =900V, and a residual voltage V C =1000V (such as FTR20D112KJ).

[0032] : the residual voltage of the pressure-sensitive resistor (the actual terminal voltage flowing through the surge current when absorbing energy, determined by the "voltage-current characteristic curve" provided by the manufacturer); : the maximum withstand voltage value of the IGBT module (such as 1200V, 1700V, defined by the datasheet of the device). When the pressure-sensitive resistor is turned on to absorb energy, the voltage across it is equal to the residual voltage , which will be directly applied across the IGBT (since the MOV is connected in parallel with the IGBT). The voltage must be forced to ensure that the MOV will not be thermally broken down due to energy overload during the energy absorption process. For example, if is calculated, a MOV with a voltage of should be selected (with a 25% margin to cope with extreme conditions).

[0033] : rated energy absorption capacity of the varistor (the maximum energy that can be absorbed by a single surge, marked by the manufacturer in joules); : total energy absorbed by the MOV during the shutdown process of the direct-current solid-state circuit breaker (SSCB); L: line inductance (including stray inductance, which determines the magnetic field energy storage); : peak fault current during shutdown (or rated breaking current); : IGBT shutdown time (the length of time for the current to drop from the peak value to 0).

[0034] This multi-dimensional constraint ultimately serves the core goal of "improving the breaking frequency of the SSCB" - by ensuring the reliable operation of the MOV, reducing the thermal and voltage stress of the IGBT, and prolonging its service life.

[0035] In this embodiment, the voltage clamping module is composed of an active clamping circuit, mainly a transient voltage suppression diode in series on the power device drive side, which feeds back and adjusts the overvoltage when the voltage is too high to prevent the power device from being damaged by excessive overvoltage breakdown during shutdown.

[0036] In this embodiment, as shown in Figure 3 , the junction temperature prediction module based on the physical information neural network is designed as follows: It mainly includes a voltage and current sensor for monitoring power, an FPGA for collecting power and outputting junction temperature in real time using a neural network model, and the FPGA sends an opening signal to the auxiliary energy absorption module according to its predicted junction temperature. For solid-state switches, the opening frequency is relatively low, and the opening process often lasts for about 100us due to the presence of current-limiting reactors, so the sampling frequency of the FPGA should at least meet 1us once, and its sampling frequency should be at least greater than 1Mh.

[0037] As shown in Figure 4 , the simple thermal model of the physical information neural network is composed of a simple RC network. Its thermal resistance network can be expressed by the following formula:

[0038] Among them, represents the state variable in the thermal resistance network; is the IGBT chip junction temperature (core monitoring target), and are two intermediate temperature nodes selected artificially (used to simulate the heat transfer path from the junction to the environment); is the input variable, is the power loss of the IGBT (heat source), is the ambient temperature (heat dissipation reference); The rate of change of each temperature node is described, which is determined by the loss heat production, environmental heat dissipation and the thermal resistance / thermal capacity characteristics between nodes; The output equation y=Cx shows that the final output of the model is the junction temperature (C=(1,0,0), only the first element in x is extracted).

[0039] The RC network model describes the heat dissipation law of IGBT from the physical layer, providing a basic constraint for the subsequent physical information neural network, which can correct the model error caused by aging by combining data-driven, and realize accurate junction temperature prediction.

[0040] However, the IGBT model itself will have aging problems, so its RC network model will not be fixed after multiple uses, and the value in the RC network model will change. For example, when the IGBT module is used for a long time, it will cause the bonding wire to separate or the heat-conducting silicone grease to be lost. When the heat-conducting silicone grease is 10% missing, it may cause the thermal resistance of the IGBT to rise by 5%, and the bonding wire is more serious. As the bonding wire goes from a healthy state to 4 falling, the thermal resistance will increase by 18%.

[0041] Therefore, the junction temperature obtained by the traditional model will significantly increase in error after the IGBT is aged for a period of time, so the present application optimizes the model by using a physical information neural network. The network model obtained is as follows:

[0042] Among them, Still represents the IGBT junction temperature and two intermediate temperature nodes; Is the input (power loss, ambient temperature); f(x,u) is the physical thermal model of the traditional RC network, which describes the temperature change law in the initial state; Is a correction term fitted by a neural network (w) The network weight), used to capture the RC network parameter changes (such as thermal resistance drift) caused by aging, compensate for the error of the traditional model, and increase Further fit the temperature loss; preferably, the weight Is updated in real time through an online learning algorithm (such as gradient descent).

[0043] The output y=Cx still takes the junction temperature As the core output.

[0044] By fusing the prior knowledge of the physical model and the data-driven ability of the neural network, the optimized model can adapt to the changes in the thermal characteristics of the IGBT after aging, significantly improve the junction temperature prediction accuracy, and provide a reliable basis for the accurate triggering of the subsequent auxiliary energy absorption module.

[0045] Preferably, the training process of the physical information neural network is substantially as shown in Figure 5 : 1. Constructing initial input values (x0, u0); 2. Solving the ODE differential equation to obtain ; 3. Obtaining using neural network weights; 4. Iterative optimization: repeat the following steps until convergence: (1) Time step loop: for k = 1 to N sim (analog step size) optimization; (2) Measure the loss: (predicted output compared with measured target); (3) Parameter update: perform optimization step to update network weights β.

[0046] Wherein, the settings of the physical information neural network are as shown in Table 1: Table 1

[0047] For example: neural network correction term A 3-layer fully connected network is adopted, the hidden layer activation function is LeakyReLU (α = 0.1), and the training data contains 1000 groups of IGBT aging working conditions (bonding wire shedding rate 0%-20%, heat-conducting silicone grease loss rate 0%-10%).

[0048] In this embodiment, as shown in Figure 6 , the solid-state circuit breaker after application of the present application, the circuit is a direct current solid-state circuit breaker core function circuit, integrating power switch module, voltage clamping module, auxiliary energy absorption module and junction temperature prediction module, each part function is realized through element cooperation, see Table 2: Table 2

[0049] Figure 6 The key component functions are as follows: (Line inductance): stores the energy of the DC line, when D1 is off, the inductance releases energy (manifested as reverse current), which is the core carrier of "energy source" in the off process.

[0050] C1 (buffer capacitor): suppresses the voltage mutation (overvoltage induced by di / dt) when D1 is off, and assists the voltage clamping module to stabilize the voltage.

[0051] D1 (IGBT module): main power switch, which needs to withstand the double stress of electric energy + line energy when off, and the junction temperature rises quickly; the antiparallel diode is used for freewheeling.

[0052] D2, D3 (clamp diode): constitute an active clamp circuit, dynamically adjust the voltage across D1 through voltage feedback, limit the voltage peak at turn-off (such as suppress the overvoltage within 90% of the withstand voltage of D1).

[0053] MOV (metal oxide varistor): auxiliary energy absorption core component, using the nonlinear voltage-current characteristic to absorb energy: Low voltage: very small leakage current, almost open circuit, does not affect the main circuit; High voltage: resistance drops, quickly absorbs the energy released by the inductor (such as 200A impact energy).

[0054] S1 (thyristor): auxiliary energy absorption "switch", triggered by the junction temperature prediction module signal: Normal junction temperature: off, MOV does not work; Junction temperature warning: on, making MOV connected to the circuit to absorb energy.

[0055] R2, R3 (voltage balancing resistor): balance the static voltage across MOV and S1 (such as bus voltage), to avoid S1 from turning on prematurely due to uneven voltage, or MOV from malfunctioning due to overvoltage.

[0056] Example two Based on the same concept, the present application also proposes a method for improving the rated current breaking times of a DC solid-state circuit breaker, using the device of example one, specifically including the following steps: S1. When the solid-state switch receives a turn-off signal, the power device starts to turn off, and the power device voltage clamping module is started simultaneously to suppress overvoltage and protect the power device; S2. Start the junction temperature prediction based on physical information neural network, monitor the power device loss in real time and predict its junction temperature; In this embodiment, the junction temperature prediction based on physical information neural network includes: Collect the real-time operating parameters of the power device through voltage and current sensors; Input the operating parameters into the model that fuses the physical thermal model and the neural network correction term, and the model outputs the real-time junction temperature prediction value by compensating the thermal resistance network changes caused by power device aging through the neural network correction term.

[0057] S3. If the predicted junction temperature is not close to the preset limit value, the remaining energy is absorbed by the power device alone; if the predicted junction temperature is close to the preset limit value, trigger the auxiliary energy absorption module to start, so that the remaining energy is absorbed by the auxiliary energy absorption module; In this embodiment, the predicted junction temperature close to the preset limit value specifically refers to: the predicted junction temperature reaches the preset proportion of the limit junction temperature of the power device, and the preset proportion is 80%-90%; After the auxiliary energy absorption module is started, the current is commutated from the power device to the pressure sensitive resistor of the auxiliary energy absorption module, the pressure sensitive resistor absorbs the residual energy, and the voltage spike is eliminated through the voltage clamping module of the power device during the commutation process.

[0058] S4. After the auxiliary energy absorption module absorbs energy, it is automatically turned off to complete the turn-off process. Among them, the condition for the auxiliary energy absorption module to automatically turn off is that the leakage current of the pressure sensitive resistor is reduced to less than the holding current of the thyristor, and the thyristor is turned off.

[0059] As shown in Figure 6 and Figure 7 Before turning off: (fault current or rated current, red solid line), keep stable (line inductance energy storage is not released); (IGBT saturated conduction, ), (equalizing resistor voltage division, MOV is in a high resistance state, and the leakage current can be ignored).

[0060] Figure 7 Among them, the horizontal axis: time ( ), corresponding to the four stages of the turn-off process; the upper half of the vertical axis: current (I), including the main switch current (IGBT current, purple dashed line) and MOV current (green dashed line); the lower half of the vertical axis: voltage (V), including the main switch voltage (IGBT voltage, solid line) and MOV voltage (green dashed line).

[0061] Figure 7 In the , the receiving of the turn-off instruction by the direct current solid state circuit breaker (SSCB) is taken as the trigger starting point, and the operation is divided into four stages: Stage one (t1-t2): 1. Trigger logic: IGBT turn-off start time node t1: The control unit of the direct current solid state circuit breaker (SSCB) sends a turn-off signal to the IGBT (D1), and the IGBT enters the turn-off process, and the collector current quickly drops.

[0062] 2. Physical root of voltage rise: inductance counter electromotive force Due to current mutation ( ), according to the law of electromagnetic induction , a reverse electromotive force will be induced, which is superimposed with the bus voltage, resulting in a rapid rise of the voltage across the IGBT.

[0063] ​3. The core role of the voltage equalization resistor: static voltage balance R1, R2 in the circuit (usually designed as R1=R2) form a static voltage division network, which divides the voltage into two parts:

[0064] Design constraints: MOV: Its 1mA nominal voltage Must be greater than "half bus voltage" (bus rated voltage before shutdown), to ensure that the MOV leakage current is minimal (much lower than 1mA) during t1-t2, and it is in a high resistance state, not participating in energy absorption.

[0065] SCR: The voltage withstand level must withstand at least "half bus voltage", at this time the SCR is in the off state due to the absence of a trigger signal, and the auxiliary energy absorption branch as a whole is in "standby".

[0066] 4. Stage end (t2): dual module start Active clamp module start: When Rises above the trigger threshold of the active clamp circuit (determined by the clamping characteristics of D2 and D3), the active clamp circuit dynamically adjusts through voltage feedback to suppress the rising slope and peak value, avoiding damage to the IGBT due to overvoltage.

[0067] Junction temperature prediction module start (IGBT off instantaneously, junction temperature prediction module starts simultaneously): Collecting IGBT voltage and current signals, calculating real-time power loss ; Substituting into the physical information neural network model (combining RC thermal model and aging correction term ), real-time prediction of IGBT junction temperature T j , providing a basis for subsequent "auxiliary energy absorption trigger".

[0068] This stage is a transition state of "main branch stress resistance + monitoring and early warning", laying the foundation for precise execution in stage two (auxiliary energy absorption trigger).

[0069] Stage two (t2-t3): 1. Starting feature: IGBT enters linear region (active region) IGBT gate voltage: drops to the threshold voltage nearby (such as IGBT threshold of 5V, at this time ), IGBT enters linear region (active region, increases with I_c) from saturation region (low resistance state, ).​

[0070] Equivalent resistance change: in linear region, dynamic equivalent resistance of IGBT Start to increase (due to weakened gate drive capability, channel conductance drops), leading to Rapid rise.

[0071] 2. Dynamic evolution of voltage and current Voltage characteristics: Due to Rapid rise due to increased, but constrained by secondary active clamping circuit (later analysis); Current characteristics: line inductance hinders current mutation ( ), so the bus current (i.e. ) slowly decreases (rather than mutating).

[0072] 3. "Early intervention" logic of secondary active clamping Design goal: slow down Rise slope, reduce instantaneous power loss of IGBT , thereby delaying the rise speed of junction temperature.

[0073] Parameter setting: the trigger voltage of secondary clamping is set to 90% of the primary clamping voltage (for example: if the primary clamping triggers at 800V, the secondary clamping triggers at 720V).

[0074] Working principle: when Reaches the secondary clamping voltage, the secondary clamping circuit (such as a more sensitive feedback branch) starts, and by dynamically adjusting the gate drive of the IGBT (or the shunt of the clamping diode), it forces to reduce Rise rate (e.g. from 100V / µs to 50V / µs).

[0075] This makes The drop speed is also slowed down (because , Rise slowly, di / dt decreases), ultimately achieving "voltage-current slope double reduction", controlling the loss growth rate of IGBT.

[0076] 4. Evolution of junction temperature and trigger decision Energy absorption body: in stage two, IGBT continuously absorbs two parts of energy: Inductor energy storage: (magnetic field energy released by inductor during current drop); Bus energy: (sustained energy injection driven by bus voltage).

[0077] These energies are converted into heat loss, causing the IGBT junction temperature to continuously rise.

[0078] Trigger condition design: The junction temperature output by the junction temperature prediction module reaches 80% of the IGBT limit junction temperature (e.g. limit junction temperature 150℃, pre-warning value set to 120℃). Preferably, the preset proportion is dynamically adjusted according to the aging degree of the power device, with an adjustment range of 70%-95%.

[0079] Margin design reason: Due to measurement errors (such as voltage / current sampling noise) and model errors (such as fitting residual of physical information neural network), a 20% margin is reserved to ensure that the actual junction temperature does not exceed the limit value (to avoid IGBT thermal failure).

[0080] 5. Core significance of thyristor triggering When the junction temperature reaches the pre-warning value, the SCR is triggered to conduct, allowing the auxiliary energy absorption branch (MOV) to access the main circuit: Energy commutation: The energy originally borne by the IGBT is shunted to the MOV for absorption, instantaneously reducing the thermal load of the IGBT; Protection closed loop: Through "junction temperature prediction → SCR triggering → energy shunting", a dynamic balance of "temperature control - energy absorption" is achieved, avoiding accelerated aging of the IGBT due to over-temperature, and ultimately improving the rated breaking times of the SSCB.

[0081] This stage is the key transition of "main branch loss control → auxiliary branch connection", and through multi-module cooperation, the unity of "thermal safety" and "breaking capacity" in the shutdown process is achieved.

[0082] Stage three (t3-t4): 1. Core triggering: Thyristor S1 conducts, auxiliary energy absorption branch accesses Trigger node t3: When the IGBT junction temperature reaches 80% of the limit junction temperature (end of stage two), the junction temperature prediction module sends a trigger signal to the thyristor S1, which immediately conducts.

[0083] Circuit topology change: After S1 conducts, the MOV is directly connected in parallel with the IGBT through S1, forming a "IGBT and MOV in parallel" circuit structure, providing a path for energy commutation.

[0084] 2. Current commutation: Smooth transition from IGBT to MOV Current evolution law: Before conduction (t<t3): circuit current (main switch current, i.e. collector current of IGBT) is mainly borne by the IGBT, used to absorb electrical energy; After conduction (t3-t4): due to the low resistance characteristic of the MOV after being connected in parallel (voltage lower than Small leakage current, but at this time the voltage has been due to the shutdown process, the MOV into the conduction zone), the current begins to gradually transfer from the IGBT branch to the MOV branch, forming the current of the MOV .

[0085] The commutation result is: IGBT current) decreases synchronously with the increase of MOV current) until , and the whole energy transfer is completed.

[0086] 3. Key breakthrough: active clamp circuit eliminates voltage spikes Pain point of traditional scheme: if only through the MOV directly parallel energy absorption, when the current is quickly commutated from the IGBT to the MOV, due to the "obstruction of current mutation" characteristics of the line inductance , , an abrupt voltage spike (may exceed the IGBT withstand voltage limit) will be generated, resulting in device damage.

[0087] Optimization of the application: In stage three, the active clamp module (including transient voltage suppression diode) works continuously, and the voltage across the IGBT is dynamically adjusted through voltage feedback: Limit the voltage rise rate (dv / dt), so that the voltage change rate is much lower than that of the traditional scheme; force the voltage to be clamped at a preset threshold (such as 90% of the IGBT withstand voltage), to ensure that there is no voltage spike during the commutation process.

[0088] Therefore, the current can be "commutated slowly" to the MOV, avoiding the stress overload of the device caused by the spike.

[0089] 4. Energy absorption: MOV absorbs the remaining energy Energy source: the remaining energy in the circuit at this time is mainly the magnetic field energy stored in the line inductance (part of the energy has been consumed in stages one and two, and the current has decreased compared to the initial shutdown, for example, using FZ600R17KE4 IGBT module for experiment, the experimental waveform shows that under normal circumstances, the current decreases to half, that is, if the fault current is 600A, the MOV absorbs energy when the current is 300A).

[0090] Absorption path: as the current is gradually commutated from to , the remaining energy of the inductor is completely absorbed by the MOV (the MOV presents a low resistance state under high voltage by using its nonlinear voltage-current characteristic, and quickly consumes energy).

[0091] IGBT reduction: after the MOV is connected, the current of the IGBT Rapidly drop, no longer withstand energy impact, junction temperature stop rising, avoid damage due to over-temperature.

[0092] 5. Stage core goal: balance "protect IGBT" and "reduce MOV impact" Because the first and second stages have absorbed part of the energy by the IGBT itself, the current during the third stage commutation has dropped significantly (usually to less than 50% of the initial off current), and the current impact on the MOV is much lower than the traditional solution (the traditional solution requires the MOV to absorb all the initial energy).

[0093] This "step-by-step energy absorption" design not only protects the IGBT (avoids over-temperature), but also reduces the impact frequency and intensity of the MOV, directly extending the life of the MOV (reference decay curve: life is increased by about 10 times under 200A impact), ultimately improving the rated breaking times of the SSCB.

[0094] This stage achieves "safe transfer of energy from IGBT to MOV" through the coordinated action of "thyristor conduction → MOV parallel → active clamping peak suppression → energy smooth commutation", solving the IGBT over-temperature problem and overcoming the voltage spike defect of the traditional solution, which is the core execution link of the invention to improve breaking times.

[0095] Stage four (t4-t n ): 1. Core state: MOV completes energy absorption, enters leakage current area Energy absorption end t4: After the commutation of stage three, the remaining energy in the line inductance has been completely absorbed by the MOV (voltage-sensitive resistor), and the working state of the MOV changes from "strong energy absorption state" (high voltage, large current) to "leakage current state" (low voltage, small current).

[0096] Definition of leakage current area: When the voltage across the MOV drops to close to its 100mA nominal voltage , the current flowing through the MOV is no longer the "surge current" of stage three, but a very small leakage current (about 100mA). At this time, the MOV exhibits high resistance characteristics (only allowing weak current to pass), hence the name "leakage current area".

[0097] 2. Voltage and current characteristics:

[0098] Here refers to the voltage across the MOV (since the MOV is now connected in parallel to the main circuit, it is approximately equal to the bus residual voltage). After energy absorption is complete, the voltage stabilizes around This is a inherent characteristic of the MOV: when the voltage is below this value, the leakage current decreases sharply with the decrease in voltage; when the voltage is equal to this value, the leakage current stabilizes at around 100mA.

[0099] 3. Key Logic for Automatic SCR Shutdown SCR turn-off condition: The conduction of a thyristor (SCR) requires that "anode current ≥ sustaining current" (the sustaining current is the minimum current that keeps the SCR conducting, which is determined by the device characteristics).

[0100] In stage four, the leakage current of the MOV is about 100mA, and this current is less than the holding current of the SCR (for example, if the holding current of the SCR is 150mA, the 100mA leakage current cannot maintain its conduction), so the SCR will automatically turn off.

[0101] 4. Core objective of this phase: System reset to prepare for the next breakdown. After the SCR is turned off, the auxiliary energy absorption module (MOV + SCR + voltage equalizing resistor) returns to standby mode: MOV due to When in a high-impedance state, the SCR is turned off, the voltage equalizing resistor continues to maintain a static voltage division, and the entire circuit returns to the "initial state before disconnection", ready to respond to the next shutdown command at any time.

[0102] 5. Design Value: The "self-reset" mechanism without additional control enhances reliability. Stage four requires no external control signal intervention, relying entirely on the inherent characteristics of the components (MOV leakage current characteristics, SCR holding current characteristics) to achieve automatic reset. This avoids voltage / current surges that may result from "forced shutdown," further reducing circuit complexity and fault risk. This "self-reset" design ensures stable operation of the solid-state circuit breaker during multiple breaking cycles, ultimately contributing to an increase in its rated current breaking capacity.

[0103] This stage, as the "final stage" of the shutdown process, utilizes the leakage current characteristics of the MOV and the sustaining current characteristics of the SCR to achieve the non-interventional reset of the auxiliary energy absorption module. This not only completes the closed loop of energy absorption but also prepares for the next shutdown, making it a key link in ensuring the long-term reliable operation of the system.

[0104] This design transforms what was originally only applicable to V... 1mA MOV upgraded to V MOV_100mA Simultaneously, an active clamping design eliminates previously uncontrollable voltage spikes, allowing the design to approach the IGBT's withstand voltage limit and improving IGBT utilization. Furthermore, to prevent frequent damage to the MOV from surges, a reasonable delay circuit is incorporated. Under small current and small surges, the IGBT is turned off alone, and the MOV is only connected after the IGBT has reached its single-surge energy limit. At this point, the current is only half of what it was at the start of the shutdown, thus significantly reducing current surges, increasing the MOV's usability, and greatly extending the SSCB's lifespan.

[0105] Compared with the MOV life curve, the energy absorbed by the MOV has been reduced by at least half when the bus current has been reduced by half from the start of the shutdown according to the application.

[0106] For example, as shown in Figure 8 FIG. 4, the degradation curve of a FTR40D112KJ model varistor is observed. The V 1mA of the varistor will attenuate by 10% after 1000 times of 500A 100us impact; if the impact is 200A 100us, the V 1mA of the varistor will attenuate by 10% after 10000 times. Therefore, the service life of the MOV can be increased by about ten times according to the application, and the rated breaking of the solid-state circuit breaker design is basically consistent with the increase.

[0107] In summary, the application ingeniously realizes the reasonable distribution of the shutdown energy in the shutdown process of the solid-state switch by introducing the physical information neural network into the design of the solid-state circuit breaker, and distributes small energy to the power device while ensuring that the junction temperature is not higher than the limit junction temperature, and distributes the remaining large energy to the varistor. On the premise of ensuring that the power device is not damaged, the current impact on the varistor is reduced, thereby greatly improving the use frequency of the varistor without increasing the cost, and the rated voltage of the solid-state circuit breaker is also greatly improved due to the use of the varistor and thyristor in series, and the efficiency is further improved.

[0108] Embodiment Three The embodiment also provides an electronic device, which includes a memory 404 and a processor 402, the memory 404 stores a computer program, and the processor 402 is configured to run the computer program to perform the steps in any of the above method embodiments. Figure 9

[0109] Specifically, the processor 402 can include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the application.

[0110] ​The memory 404 can include a mass storage that stores data or instructions. For example, and without limitation, the memory 404 can include a Hard Disk Drive (HDD), a floppy disk drive, a Solid State Drive (SSD), a flash drive, a Compact Disc Read Only Memory (CD-ROM), a magneto-optical disk, a magnetic tape, or a Universal Serial Bus (USB) drive, or a combination of two or more of these. The memory 404 can be removable and / or non-removable (or fixed) as appropriate. The memory 404 can be internal or external as appropriate. In particular embodiments, the memory 404 is a Non-Volatile memory. In particular embodiments, the memory 404 includes a Read-Only Memory (ROM) and a Random Access Memory (RAM). The ROM can be a mask-programmed ROM, a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM), an Electrically Alterable ROM (EAROM), or a FLASH memory, or a combination of two or more of these, as appropriate. The RAM can be a Static Random-Access Memory (SRAM) or a Dynamic Random Access Memory (DRAM), which can be a Fast Page Mode Dynamic Random Access Memory (FPMDRAM), an Extended Data Output Dynamic Random Access Memory (EDODRAM), a Synchronous Dynamic Random-Access Memory (SDRAM), or the like, as appropriate.

[0111] The memory 404 can be used to store or buffer various data files needed for processing and / or communication, and possible computer program instructions executed by the processor 402.

[0112] The processor 402 implements the method for increasing the rated current breaking times of the DC solid-state circuit breaker in any of the above embodiments by reading and executing the computer program instructions stored in the memory 404.

[0113] Optionally, the electronic device described above can further include a transmission device 406 connected to the processor 402 and an input / output device 408 connected to the processor 402.

[0114] The transmission device 406 can be used to receive or send data via a network. Specific examples of the network can include a wired or wireless network provided by a communication provider of the electronic device. In one example, the transmission device includes a network adapter (NIC) which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 406 can be a radio frequency (RF) module which is used to communicate with the Internet in a wireless manner.

[0115] The input / output device 408 is used to input or output information.

[0116] Embodiment Four The embodiment also provides a readable storage medium, and the readable storage medium stores a computer program. The computer program includes program codes for controlling a process to execute the process. The process includes the method for increasing the rated current breaking times of the DC solid-state circuit breaker according to the first embodiment.

[0117] It should be noted that the specific examples in the embodiment can refer to the examples described in the above embodiments and optional implementation manners, and the embodiment will not be described here.

[0118] Generally, various embodiments can be implemented in hardware or special-purpose circuitry, software, logic or any combination thereof. Some aspects of the application can be implemented in hardware, while other aspects can be implemented by firmware or software executed by a controller, microprocessor or other computing device, but the application is not limited thereto. Although various aspects of the application can be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein can be implemented in hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0119] Embodiments of the application can be implemented by computer software executable by a data processor of the mobile device such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, can be stored in any apparatus-readable data storage medium and they include program instructions to implement certain tasks. The program product can include one or more computer-executable components such as by way of example scripts, programs, routines, objects, components, data structures, procedures, subroutines, etc., for implementing one or more embodiments of the application. The computer-executable components can be stored in computer-readable storage medium. The computer-readable storage medium can include one or more of a floppy disk, a ZIP® disk, a hard disk, a video tape, a pen drive, a memory stick, a system memory, a RAM, a ROM, a programmable ROM (EPROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a portable computer disk, a Figure 2 Any block in the logical flow of the method described herein, including those of the artificial neural network, can represent a program step, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software can be stored on such physical media as memory chips, or memory blocks implemented in the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD, etc. The physical media are non-transitory media.

[0120] Those skilled in the art should understand that all or some of the technical features in the above embodiments can make any combinations, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0121] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as the limitation to the scope of the present application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A device for increasing the number of current breaking times of a DC solid state circuit breaker comprising power devices, either IGBTs or SiC MOSFETs, characterized in that, Also comprising: a junction temperature prediction module based on a physical information neural network, an auxiliary energy absorption module, and a power device voltage clamping module; the junction temperature prediction module is electrically connected with the power device, for monitoring the loss of the power device when the solid-state switch is turned off, and predicting the junction temperature of the power device in real time through the embedded physical information neural network; the power device voltage clamping module is associated with the drive side of the power device, for suppressing overvoltage during the off process of the solid-state switch, and preventing the power device from being damaged by overvoltage; the auxiliary energy absorption module is connected in parallel with the power device, and is signal connected with the junction temperature prediction module, when the junction temperature prediction module predicts that the junction temperature of the power device is close to the preset limit value, the auxiliary energy absorption module responds and starts to absorb the remaining energy in the off process.

2. The apparatus of claim 1, wherein, the junction temperature prediction module comprises: a voltage and current sensing unit for collecting operating parameters of the power device; a processing unit with a physical information neural network model, the physical information neural network model combines a physical thermal model of the power device and a neural network correction term to fit the changes in thermal characteristics of the power device after aging, and outputs the real-time predicted junction temperature.

3. The apparatus of claim 2, wherein, The input of the physical information neural network model includes the loss, ambient temperature and operating voltage and current parameters of the power device, and the output is the prediction result related to the junction temperature of the power device; the neural network correction term is used to compensate for the change in thermal resistance network parameters caused by the aging of the power device, and the weight β of the neural network correction term is updated in real time through an online learning algorithm.

4. The apparatus of claim 1, wherein, The auxiliary energy absorption module comprises: a voltage-dependent resistor, a thyristor and a voltage equalization resistor; the voltage equalization resistor is used to balance the voltage across the voltage-dependent resistor and the thyristor; the on state of the thyristor is triggered by the control signal output by the junction temperature prediction module, and after being turned on, the voltage-dependent resistor is connected to the circuit to absorb energy.

5. The apparatus of claim 4, wherein, The voltage-dependent resistor satisfies: the voltage at 100mA leakage current is greater than the bus voltage, the residual voltage is less than the maximum withstand voltage of the power device, and the energy absorption capacity is greater than the total energy in the off process.

6. The device of any one of claims 1 to 5, wherein, The power device voltage clamping module is an active clamping circuit, which includes a transient voltage suppression diode in series, and the transient voltage suppression diode is adjusted by voltage feedback to limit the voltage rise slope and peak value of the power device during the off process.

7. Method of increasing the number of breaking cycles at rated current of a direct current solid state circuit breaker, characterized in that, The device of any one of claims 1 to 6, specifically comprising the following steps: S1. When the solid-state switch receives a turn-off signal, the power device starts to turn off, and the power device voltage clamping module is started synchronously to suppress overvoltage and protect the power device; S2. Start the junction temperature prediction based on the physical information neural network to monitor the loss of the power device in real time and predict its junction temperature; S3. If the predicted junction temperature is not close to the preset limit value, the remaining energy in the off process is absorbed by the power device alone; if the predicted junction temperature is close to the preset limit value, the auxiliary energy absorption module is triggered to start, so that the remaining energy is absorbed by the auxiliary energy absorption module; S4. After the auxiliary energy absorption module finishes absorbing energy, it is automatically turned off to complete the off process; wherein the condition for the auxiliary energy absorption module to automatically turn off is that the leakage current of the voltage-dependent resistor is reduced to less than the holding current of the thyristor, and the thyristor is turned off.

8. The method of claim 7, wherein, In step S2, the junction temperature prediction based on the physical information neural network comprises: Real-time operating parameters of the power device are collected by a voltage and current sensor; The operating parameters are input into a model combining a physical thermal model and a neural network correction term, the model compensates for changes in the thermal resistance network caused by aging of the power device through the neural network correction term, and outputs a real-time junction temperature prediction value.

9. The method of claim 7, wherein, In step S3, the predicted junction temperature is close to a preset limit value, specifically, the predicted junction temperature reaches a preset proportion of the limit junction temperature of the power device, and the preset proportion is 80%-90%. After the auxiliary energy absorption module is started, the current is commutated from the power device to the pressure-sensitive resistor of the auxiliary energy absorption module, the pressure-sensitive resistor absorbs the residual energy, and the voltage spike is eliminated through the voltage clamping module of the power device during the commutation process.

10. A readable storage medium, characterized by, The readable storage medium stores a computer program, the computer program includes program codes for controlling a process to execute the process, and the process includes the method for improving the breaking times of the rated current of the direct current solid-state circuit breaker according to any one of claims 7 to 9.

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