Method and device for increasing the number of breaking times of a dc solid state circuit breaker and applications thereof

Abstract

The application provides a method and device for improving the rated current breaking times of a direct-current solid-state circuit breaker and application thereof, and aims at the problem that the performance of an existing direct-current solid-state circuit breaker is degraded after multiple current impacts on a voltage-dependent resistor, the junction temperature of a power device is difficult to measure, and the breaking times are limited due to over-temperature damage, the application 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 accurately predicts 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 the turn-off overvoltage. The auxiliary energy absorption module is started when the junction temperature is close to the limit, and absorbs the remaining energy. The design reasonably allocates the turn-off energy, reduces the impact times and intensity of the voltage-dependent resistor, significantly improves the service life (such as about 10 times under the impact of 200 A), and further greatly improves the rated breaking times of the solid-state circuit breaker, and is low in cost, high in reliability, and suitable for scenes such as a direct-current power grid.

Description

Technical Field

[0001] This invention relates to the field of power electronics, specifically to the circuit topology design of DC solid-state circuit breakers, and more particularly to a technique for increasing the rated current breaking capacity of DC solid-state circuit breakers. Background Technology

[0002] As a key device in the field of power electronics, DC solid-state circuit breakers realize the connection, disconnection and protection of circuits through power semiconductor devices (such as IGBTs, SiC MOSFETs, etc.) and their control circuits. Compared with traditional mechanical circuit breakers, they have significant advantages such as high-speed disconnection, arc-free disconnection and long theoretical life (hundreds of thousands of cycles), and have broad application prospects in DC power grids, new energy systems and other scenarios.

[0003] However, the actual breaking count of existing DC solid-state circuit breakers is still significantly limited, mainly in two aspects: First, their energy absorption circuit is usually composed of a varistor and an RCD circuit. After being subjected to multiple current surges, the varistor will experience performance degradation problems such as increased leakage current and decreased energy absorption capacity, becoming the core bottleneck limiting the life of the circuit breaker. Second, power devices need to withstand a large amount of energy during the turn-off process, but their junction temperature is difficult to measure directly. If the junction temperature exceeds the limit, it will cause device damage and further reduce the breaking reliability.

[0004] The aforementioned defects severely limit the rated breaking capacity and practical application value of DC solid-state circuit breakers. Therefore, there is an urgent need for a technical solution that can synergistically optimize energy distribution and device protection. Summary of the Invention

[0005] This invention provides a method, apparatus, and application for increasing the rated current breaking capacity of a DC solid-state circuit breaker. It addresses the problems of existing DC solid-state circuit breakers having limited breaking capacity due to performance degradation after multiple current surges to the varistor, and overheating damage caused by the difficulty in real-time monitoring of the junction temperature of power devices.

[0006] The core technology of this invention is to monitor the junction temperature of power devices in real time through a junction temperature prediction module based on physical information neural network, and to coordinate the distribution of turn-off energy by an auxiliary energy absorption module and a voltage clamping module (energy is preferentially absorbed by the power devices, and auxiliary energy absorption is activated when the junction temperature is close to the limit), so as to improve the rated current breaking number of DC solid circuit breakers.

[0007] In a first aspect, the present invention provides an apparatus for increasing the rated current breaking capacity of a DC solid-state circuit breaker, comprising a power device, such as an IGBT or a SiC MOSFET, and further comprising:

[0008] A junction temperature prediction module, an auxiliary energy absorption module, and a power device voltage clamping module based on a physical information neural network;

[0009] The junction temperature prediction module is electrically connected to the power device and is used to monitor the power device's losses when the solid-state switch is turned off, and to predict the junction temperature of the power device in real time through the embedded physical information neural network.

[0010] The power device voltage clamping module is associated with the drive side of the power device and is used to suppress overvoltage during the turn-off process of the solid-state switch to prevent the power device from being damaged by overvoltage.

[0011] The auxiliary energy absorption module is connected in parallel with the power device and is signal-connected to 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 during the turn-off process.

[0012] Furthermore, the junction temperature prediction module includes:

[0013] Voltage and current sensing units are used to collect operating parameters of power devices;

[0014] The processing unit has a built-in physical information neural network model. The physical information neural network model integrates the physical thermal model of the power device with the neural network correction term to fit the changes in the thermal characteristics of the power device after aging and output the real-time predicted junction temperature.

[0015] Furthermore, the input of the physical information neural network model includes the power device losses, ambient temperature, and operating voltage and current parameters, 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 changes 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.

[0016] Furthermore, the auxiliary energy absorption module includes:

[0017] Varistors, thyristors, and voltage equalizing resistors;

[0018] The voltage equalizing resistor is used to balance the voltage across the varistor and the thyristor;

[0019] The conduction state of the thyristor is triggered by the control signal output by the junction temperature prediction module. After conduction, the varistor is connected to the circuit to absorb energy.

[0020] Furthermore, the varistor satisfies the following requirements: its voltage at a leakage current of 100mA is greater than the bus voltage, its residual voltage is less than the maximum withstand voltage of the power device, and its energy absorption capacity is greater than the total energy during the turn-off process.

[0021] Furthermore, the power device voltage clamping module is an active clamping circuit, including a transient voltage suppression diode connected in series. The transient voltage suppression diode is regulated by voltage feedback to limit the voltage rise slope and peak value of the power device during the turn-off process.

[0022] Secondly, the present invention provides a method for increasing the rated current breaking capacity of a DC solid-state circuit breaker, using the aforementioned apparatus, specifically including the following steps:

[0023] S1. When the solid-state switch receives a turn-off signal, the power device begins to turn off, and the power device voltage clamping module is activated simultaneously to suppress overvoltage and protect the power device.

[0024] S2. Initiate junction temperature prediction based on physical information neural network to monitor the power device loss and predict its junction temperature in real time;

[0025] S3. If the predicted junction temperature is not close to the preset limit value, the power device will absorb the turn-off energy alone; if the predicted junction temperature is close to the preset limit value, the auxiliary energy absorption module will be triggered to start, so that the remaining energy will be absorbed by the auxiliary energy absorption module.

[0026] S4. After the auxiliary energy absorption module finishes absorbing energy, it will automatically shut down to complete the shutdown process;

[0027] The automatic shutdown condition for the auxiliary energy absorption module is: the leakage current of the varistor drops to less than the holding current of the thyristor, and the thyristor turns off.

[0028] Furthermore, in step S2, the junction temperature prediction based on the physical information neural network includes:

[0029] Real-time operating parameters of power devices are acquired through voltage and current sensors;

[0030] The operating parameters are input into the model that integrates the physical-thermal model and the neural network correction term. The model compensates for the changes in thermal resistance network caused by the aging of power devices through the neural network correction term and outputs the real-time junction temperature prediction value.

[0031] Furthermore, in step S3, predicting that the junction temperature is close to the preset limit value specifically means: predicting that the junction temperature reaches the preset proportion of the power device's limit junction temperature, where the preset proportion is 80%-90%;

[0032] After the auxiliary energy absorption module is started, the current is commutated from the power device to the varistor of the auxiliary energy absorption module. The varistor absorbs the remaining energy, and the voltage spikes are eliminated by the voltage clamping module of the power device during the commutation process.

[0033] Thirdly, the present invention provides an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the above-described method for increasing the rated current breaking capacity of a DC solid-state circuit breaker.

[0034] Fourthly, the present invention provides a readable storage medium storing a computer program, the computer program including program code for controlling a process to execute the process, the process including the method for increasing the number of rated current breaking times of a DC solid-state circuit breaker as described above.

[0035] The main contributions and innovations of this invention are as follows:

[0036] 1. Significantly increase the number of breaking cycles: By precisely controlling the start-up timing of the auxiliary energy absorption module (starting only when the junction temperature of the power device is close to the limit), the number and intensity of current surges that the varistor withstands are reduced (the energy of a single surge is reduced by about 50%). Combined with the degradation characteristics of the varistor (such as a lifespan increase of about 10 times under a 200A surge), its service life is greatly extended, thereby increasing the overall number of breaking cycles of the circuit breaker.

[0037] 2. Reliable protection for 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. Together with the voltage clamping module, it can suppress overvoltage and avoid device damage due to overtemperature or overvoltage.

[0038] 3. Optimize energy distribution efficiency: Give full play to the complementary advantages of semiconductor devices (high material recoverability and long life) and varistors (strong energy absorption capacity) to achieve reasonable distribution of turn-off energy and improve device utilization.

[0039] 4. Low cost and easy to implement: No need to add high-cost components, performance improvement is achieved through the co-design of algorithms and circuit topology, making it easy to be applied in engineering.

[0040] Details of one or more embodiments of the present invention are set forth in the following drawings and description, so that other features, objects and advantages of the invention will be more readily understood. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0042] Figure 1 This is a schematic diagram of a DC circuit breaker design according to an embodiment of the present invention;

[0043] Figure 2 This is a flowchart of a method for increasing the rated current breaking capacity of a DC solid-state circuit breaker according to an embodiment of the present invention;

[0044] Figure 3 This is a structural diagram of the junction temperature prediction module according to an embodiment of the present invention;

[0045] Figure 4This is a schematic diagram of an IGBT thermal model according to an embodiment of the present invention;

[0046] Figure 5 This is a flowchart of neural network training according to an embodiment of the present invention;

[0047] Figure 6 This is a circuit diagram of a solid-state circuit breaker according to an embodiment of the present invention;

[0048] Figure 7 This is a diagram illustrating the turn-off process of a solid-state circuit breaker according to an embodiment of the present invention;

[0049] Figure 8 This is a degradation curve of the FTR40D112KJ varistor according to an embodiment of the present invention;

[0050] Figure 9 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0051] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with one or more embodiments of this specification. Rather, they are merely examples of apparatuses and methods consistent with some aspects of one or more embodiments of this specification as detailed in the appended claims.

[0052] It should be noted that the steps of the corresponding methods are not necessarily performed in the order shown and described in this specification in other embodiments. In some other embodiments, the methods may include more or fewer steps than described in this specification. Furthermore, a single step described in this specification may be broken down into multiple steps in other embodiments; and multiple steps described in this specification may be combined into a single step in other embodiments.

[0053] The breaking capacity of existing DC solid-state circuit breakers is limited by the performance degradation of varistors after multiple current surges and the over-temperature damage caused by the difficulty in real-time monitoring of the junction temperature of power devices.

[0054] Based on this, the present invention addresses the problems existing in the prior art by using physical information neural networks.

[0055] Example 1

[0056] This invention aims to provide a device for increasing the rated current breaking capacity of a DC solid-state circuit breaker, specifically, referring to... Figure 1The present invention mainly comprises three parts: the first is a junction temperature prediction module based on physical information neural network; the second is an auxiliary energy absorption module (also known as a power absorption module); and the third is a power device voltage clamping module (also known as a voltage clamping module).

[0057] like Figure 2 As shown, the main switching device (power device, either an IGBT or a SiC MOSFET) is connected in the circuit, and its switching is determined by a control signal. The voltage clamping circuit and control signal are both connected to the drive side, clamping overvoltage through voltage feedback. An energy monitoring module based on a physical information neural network is connected to both ends of the main circuit. After a turn-off overvoltage occurs, it begins calculating the turn-off energy and predicts the junction temperature in real time. An auxiliary energy absorption module is connected in parallel with the main power device. Upon receiving the energy signal from the monitoring module, the auxiliary power device absorbs the remaining energy during the turn-off process, preventing damage to the IGBT junction temperature from excessively high levels.

[0058] In this embodiment, the auxiliary energy absorption module (power absorption module) consists of two voltage-equalizing resistors, a thyristor, and a varistor. The voltage-equalizing resistors are used to evenly distribute the voltage between the varistor and the thyristor, preventing them from activating under normal circumstances. When the energy monitoring module provides a start signal, the power absorption module starts, and the auxiliary power device absorbs energy. Preferably, the varistor selection should satisfy the following formula:

[0059]

[0060] in, The nominal voltage of the varistor under a leakage current of 100mA (manufacturer's test value, reflecting its "conduction threshold"); The rated operating voltage of the DC bus (e.g., 500V, 800V). When the bus voltage... At this time, the leakage current of the varistor is much less than 100mA (usually in the μA range), exhibiting a high-resistance state (approximately open circuit), and will not continuously consume bus power, nor affect the normal operation of the main circuit. For example, when the bus voltage V line When the voltage is 800V, a varistor with a leakage current voltage of 100mA should be selected. 100mA =900V, residual voltage V C =1000V models (such as FTR20D112KJ).

[0061] The residual voltage of the varistor (the surge current flowing during energy absorption). The actual terminal voltage is determined by the "volt-ampere characteristic curve" provided by the manufacturer. The maximum withstand voltage of the IGBT module (e.g., 1200V, 1700V, defined by the device datasheet). When the varistor is conducting and absorbing energy, the voltage across it is equal to the residual voltage. This voltage will be applied directly across the IGBT (because the MOV is connected in parallel with the IGBT). Forced This ensures that the MOV does not thermally break down due to energy overload during energy absorption. For example, if the calculation shows... You need to select The MOV (with a 25% margin to cope with extreme working conditions).

[0062] Rated energy absorption capacity of a varistor (the maximum energy that can be absorbed in a single surge, specified by the manufacturer in joules). : The total energy that the MOV needs to absorb during the turn-off process of a DC solid-state circuit breaker (SSCB); L: Line inductance (including stray inductance, which determines the energy stored in the magnetic field); Peak fault current (or rated breaking current) during shutdown. IGBT turn-off time (the time it takes for the current to drop from its peak value to 0).

[0063] This multi-dimensional constraint ultimately serves the core objective of "increasing the number of SSCB breakages"—by ensuring reliable operation of the MOV, reducing the thermal and voltage stresses of the IGBT, and extending its lifespan.

[0064] In this embodiment, the voltage clamping module is composed of an active clamping circuit, which mainly consists of a series transient voltage suppression diode placed on the power device drive side. When the voltage is too high, it provides feedback to regulate the overvoltage and prevent the power device from being damaged by excessive overvoltage when it is turned off.

[0065] In this embodiment, as Figure 3 As shown, the junction temperature prediction module based on physical information neural network is designed as follows:

[0066] This mainly includes voltage and current sensors for monitoring power, and an FPGA for acquiring power and outputting the junction temperature in real time using a neural network model. The FPGA sends an on / off signal to the auxiliary energy absorption module based on its predicted junction temperature. For solid-state switches, the on / off frequency is low, and the on / off process often lasts about 100µs due to the presence of a current-limiting reactor. Therefore, the FPGA sampling frequency must be at least once every 1µs, and its sampling frequency must be at least greater than 1MHz.

[0067] Among them, such as Figure 4 As shown, the simplified thermal model of the physical information neural network consists of a simple RC network. Its thermal resistance network can be expressed by the following formula:

[0068]

[0069] in, Represents the state variables in a thermal resistance network; The junction temperature of the IGBT chip (the core monitoring target). and These are two artificially selected intermediate temperature nodes (used to simulate the heat transfer path from the junction to the environment).

[0070] For input variables, It is the power loss (heat source) of the IGBT. It is the ambient temperature (heat dissipation reference).

[0071] The rate of change of each temperature node is described by the heat loss, heat dissipation from the environment, and the thermal resistance / heat capacity characteristics between nodes.

[0072] The output equation y=Cx indicates that the final output of the model is the junction temperature. (Since C=(1,0,0), only the first element of x is extracted).

[0073] This RC network model physically characterizes the heat dissipation behavior of IGBTs, providing a basic constraint for subsequent physical information neural networks. This enables the network to combine data-driven correction of model errors caused by aging and achieve accurate junction temperature prediction.

[0074] However, IGBT models themselves are subject to aging issues, so their RC network models are not fixed and their values ​​will change after repeated use. For example, prolonged use of IGBT modules can lead to bond wire detachment or thermal grease depletion. When 10% of the thermal grease is lost, the IGBT thermal resistance may increase by 5%, and bond wire detachment is even more serious. As the number of bond wires detached from a healthy state increases to 4, the thermal resistance increases by 18%.

[0075] Therefore, the junction temperature obtained by the traditional model will have a significant increase in error after the IGBT has aged for a period of time. Thus, this invention uses a physical information neural network to optimize the model. The resulting network model is as follows:

[0076]

[0077] in, This still refers to the IGBT junction temperature and the two intermediate temperature nodes;

[0078] Inputs (power loss, ambient temperature);

[0079] f(x,u) is the physical thermal model of a traditional RC network, which describes the temperature change under the initial state.

[0080] It is a correction term fitted by the neural network ( (as network weights) are used to capture changes in RC network parameters caused by aging (such as thermal resistance drift), compensate for errors in traditional models, and add weights to the original f(x,u). Further fit the missing temperature; preferably, weights Updated in real time using online learning algorithms (such as gradient descent).

[0081] The output y=Cx is still based on the junction temperature. The core output.

[0082] By integrating the prior knowledge of the physical model with the data-driven capabilities of the neural network, this optimized model can adapt to the changes in thermal characteristics after IGBT aging, significantly improve the accuracy of junction temperature prediction, and provide a reliable basis for the precise triggering of subsequent auxiliary energy absorption modules.

[0083] Preferably, the training process of the physical information neural network is roughly as follows: Figure 5 As shown:

[0084] 1. Construct the initial input values ​​(x0, u0);

[0085] 2. Solving the ODE differential equation yields... ;

[0086] 3. Obtaining weights using neural network ;

[0087] 4. Iterative optimization: Repeat the following steps until convergence:

[0088] (1) Time step loop: from k=1 to N sim Optimize using (simulated step size);

[0089] (2) Measuring loss: (Comparison between predicted output and measured target);

[0090] (3) Parameter update: Execute optimization steps to update network weight β.

[0091] The physical information neural network is configured as shown in Table 1 below:

[0092] Table 1

[0093]

[0094] For example: neural network correction terms A 3-layer fully connected network was used, with the hidden layer activation function being LeakyReLU (α=0.1). The training data included 1000 IGBT aging conditions (bond wire detachment rate 0%-20%, thermal grease loss rate 0%-10%).

[0095] In this embodiment, as Figure 6The diagram shows a solid-state circuit breaker after applying this invention. This circuit is the core functional circuit of a DC solid-state circuit breaker, integrating a power switching module, a voltage clamping module, an auxiliary energy absorption module, and a junction temperature prediction module. The functions of each part are realized through the cooperation of components, as shown in Table 2.

[0096] Table 2

[0097]

[0098] Figure 6 The functions of key components are analyzed as follows:

[0099] (Line inductance): Stores the energy of the DC line. When D1 is turned off, the inductor releases energy (manifested as reverse current) and is the core carrier of the "energy source" during the turn-off process.

[0100] C1 (buffer capacitor): suppresses voltage surges (overvoltage caused by di / dt) when D1 is turned off, and assists the voltage clamping module in stabilizing the voltage.

[0101] D1 (IGBT module): Main power switch, which needs to withstand the dual stress of inductor energy and line energy when turned off, and the junction temperature is prone to rapid rise; the anti-parallel diode is used for freewheeling.

[0102] D2 and D3 (clamping diodes): form an active clamping circuit, which dynamically adjusts the voltage across D1 through voltage feedback to limit the voltage peak during turn-off (such as suppressing overvoltage to within 90% of the withstand voltage of D1).

[0103] MOV (Metal Oxide Varistor): An auxiliary energy absorption core component that absorbs energy using nonlinear current-voltage characteristics.

[0104] At low voltage: leakage current is extremely small, almost like an open circuit, and does not affect the main circuit;

[0105] Under high voltage: the resistance drops sharply, quickly absorbing the energy released by the inductor (such as 200A of impact energy).

[0106] S1 (thyristor): An auxiliary energy absorption "switch" triggered by a signal from the junction temperature prediction module.

[0107] When the junction temperature is normal: the MOV is turned off and does not work;

[0108] When junction temperature warning occurs: the circuit is turned on, allowing the MOV to absorb energy in the circuit.

[0109] R2 and R3 (equalizing resistors): balance the static voltage (such as bus voltage) across MOV and S1 to prevent S1 from conducting prematurely due to voltage imbalance or MOV from malfunctioning due to overvoltage.

[0110] Example 2

[0111] Based on the same concept, this invention also proposes a method for increasing the rated current breaking capacity of a DC solid-state circuit breaker, using the apparatus of Embodiment 1, specifically including the following steps:

[0112] S1. When the solid-state switch receives a turn-off signal, the power device begins to turn off, and the power device voltage clamping module is activated simultaneously to suppress overvoltage and protect the power device.

[0113] S2. Initiate junction temperature prediction based on physical information neural network to monitor the power device loss and predict its junction temperature in real time;

[0114] In this embodiment, the junction temperature prediction based on a physical information neural network includes:

[0115] Real-time operating parameters of power devices are acquired through voltage and current sensors;

[0116] The operating parameters are input into the model that integrates the physical-thermal model and the neural network correction term. The model compensates for the changes in thermal resistance network caused by the aging of power devices through the neural network correction term and outputs the real-time junction temperature prediction value.

[0117] S3. If the predicted junction temperature is not close to the preset limit value, the power device will absorb the turn-off energy alone; if the predicted junction temperature is close to the preset limit value, the auxiliary energy absorption module will be triggered to start, so that the remaining energy will be absorbed by the auxiliary energy absorption module.

[0118] In this embodiment, predicting that the junction temperature is close to the preset limit value specifically means: predicting that the junction temperature reaches the preset percentage of the power device's limit junction temperature, where the preset percentage is 80%-90%;

[0119] After the auxiliary energy absorption module is started, the current is commutated from the power device to the varistor of the auxiliary energy absorption module. The varistor absorbs the remaining energy, and the voltage spikes are eliminated by the voltage clamping module of the power device during the commutation process.

[0120] S4. After the auxiliary energy absorption module finishes absorbing energy, it will automatically shut down to complete the shutdown process;

[0121] The automatic shutdown condition for the auxiliary energy absorption module is: the leakage current of the varistor drops to less than the holding current of the thyristor, and the thyristor turns off.

[0122] like Figure 6 and Figure 7 As shown, before shutdown: (Fault current or rated current, solid red line), remain stable (the energy stored in the line inductance has not been released); (IGBT saturation conduction, ), (Equalizing resistor) With voltage division, the MOV is in a high-resistivity state, and the leakage current is negligible.

[0123] Figure 7 In the middle, the horizontal axis represents time ( ), corresponding to the four stages of the turn-off process; upper half of the vertical axis: current (I), including the main switch current. (IGBT current, purple dashed line) and MOV current (Green dashed line); Lower half of the vertical axis: Voltage (V), including main switch voltage (IGBT voltage, solid line) and MOV voltage (Green dashed line).

[0124] Figure 7 In this process, the DC solid-state circuit breaker (SSCB) receives a shutdown command as the trigger point and operates in four stages:

[0125] Phase 1 (t1-t2):

[0126] 1. Triggering logic: IGBT shutdown and startup time nodes

[0127] t1: The control unit of the DC solid-state circuit breaker (SSCB) sends a turn-off signal to the IGBT (D1), and the IGBT enters the turn-off process, with the collector current... Rapid decline.

[0128] 2. The physical cause of voltage rise: inductor back electromotive force.

[0129] Line inductance Due to sudden change in current ( According to the law of electromagnetic induction This will induce a back electromotive force, which, when superimposed on the bus voltage, will cause the voltage across the IGBT to... Rapid rise.

[0130] 3. The core function of voltage equalizing resistors: static voltage balancing.

[0131] In the circuit, R1 and R2 (usually designed as R1=R2) form a static voltage divider network, which... Divided into two routes:

[0132]

[0133] Design constraints:

[0134] MOV: its 1mA nominal voltage It needs to be greater than "half the bus voltage" (the rated bus voltage before shutdown) to ensure that the MOV leakage current is extremely small (far below 1mA) during t1-t2, and that it is in a high-resistivity state and does not participate in energy absorption.

[0135] SCR: The withstand voltage rating must withstand at least "half of the bus voltage". At this time, the SCR is also in the off state because there is no trigger signal, and the auxiliary energy absorption branch is "standby".

[0136] 4. Stage End (t2): Dual-module startup

[0137] Active clamp module startup:

[0138] when The rise exceeds the trigger threshold of the active clamping circuit. (Determined by the clamping characteristics of D2 and D3), the active clamping circuit dynamically adjusts through voltage feedback to suppress... The rising slope and peak value are adjusted to prevent IGBTs from being damaged by overvoltage.

[0139] Junction temperature prediction module starts up (the junction temperature prediction module starts up synchronously at the moment the IGBT is turned off):

[0140] Collect voltage and current signals from IGBTs and calculate real-time power loss. ;

[0141] Substitute into the physical information neural network model (integrating the RC thermal model and aging correction term) Real-time prediction of IGBT junction temperature T j This provides a basis for judgment in subsequent "assisted energy absorption triggering".

[0142] This stage is a transitional phase of "main branch stress resistance + monitoring and early warning", laying the foundation for the precise execution of stage two (auxiliary energy absorption triggering).

[0143] Phase 2 (t2-t3):

[0144] 1. Initial characteristics: IGBT enters the linear region (active region)

[0145] IGBT gate voltage: Drop to threshold voltage Nearby (e.g., if the IGBT threshold is 5V, at this time) IGBTs transition from the saturation region (low resistance state) to the saturation region. ) enters the linear region (active region, It increases as I_c increases.

[0146] Equivalent internal resistance variation: Dynamic equivalent internal resistance of IGBT in the linear region It begins to increase (due to weakened gate drive capability and decreased channel conductance), leading to Rapid rise.

[0147] 2. Dynamic Evolution of Voltage and Current

[0148] Voltage characteristics: because It increases rapidly, but is constrained by the two-stage active clamping circuit (to be analyzed later).

[0149] Current characteristics: Line inductance Impede sudden changes in current ( Therefore, the bus current (i.e.) It decreases slowly (rather than mutating).

[0150] 3. The "early intervention" logic of secondary active clamping

[0151] Design goal: To mitigate The rising slope reduces the instantaneous power loss of the IGBT. This slows down the rate of temperature rise in the junction.

[0152] Parameter settings: The trigger voltage of the secondary clamp is set to 90% of the primary clamp voltage (for example, if the primary clamp is triggered at 800V, the secondary clamp is triggered at 720V).

[0153] Working principle: When When the secondary clamping voltage is reached, the secondary clamping circuit (such as a more sensitive feedback branch) is activated, forcibly reducing the voltage by dynamically adjusting the IGBT gate drive (or the shunt of the clamping diode). The rate of increase (e.g., from 100V / µs to 50V / µs).

[0154] This move made The rate of descent slowed down synchronously (because) , If the rise is slow, then di / dt decreases, ultimately achieving a "double decrease in voltage-current slope" and controlling the rate of increase in IGBT losses.

[0155] 4. Junction Temperature Evolution and Triggering Decision

[0156] Energy absorption main body: In stage two, the IGBT continuously absorbs two parts of energy:

[0157] Inductive energy storage: (Magnetic field energy released by the inductor during the current decrease).

[0158] Busbar Energy: (Continuous energy injection driven by bus voltage).

[0159] This energy is converted into heat loss, causing the IGBT junction temperature to rise continuously.

[0160] Trigger condition design: The junction temperature output by the junction temperature prediction module reaches 80% of the IGBT's limit junction temperature (e.g., if the limit junction temperature is 150℃, the warning value is set to 120℃). Preferably, the preset ratio is dynamically adjusted according to the aging degree of the power device, with an adjustment range of 70%-95%.

[0161] Margin design reason: Due to the existence of measurement errors (such as voltage / current sampling noise) and model errors (such as the fitting residuals of physical information neural networks), reserving a 20% margin can ensure that the actual junction temperature will not exceed the limit value (to avoid IGBT thermal failure).

[0162] 5. The core significance of thyristor triggering When the junction temperature reaches the warning value, trigger the SCR to conduct, and connect the auxiliary energy absorption branch (MOV) to the main circuit:

[0163] Energy commutation: Shunt the energy originally borne by the IGBT to the MOV for absorption, and instantly reduce the thermal load of the IGBT;

[0164] Protection closed-loop: Through "junction temperature prediction → SCR triggering → energy shunting", achieve the dynamic balance of "temperature control - energy absorption", avoid the IGBT from accelerating aging due to overheating, and ultimately improve the rated breaking times of the SSCB.

[0165] This stage is the key transition from "main branch loss control → auxiliary branch connection". Through multi-module cooperation, the unity of "thermal safety" and "breaking ability" in the turn-off process is achieved.

[0166] Stage three (t3 - t4):

[0167] 1. Core triggering: The thyristor S1 conducts, and the auxiliary energy absorption branch is connected

[0168] Triggering node t3: When the IGBT junction temperature reaches 80% of the maximum junction temperature (the end of stage two), the junction temperature prediction module sends a trigger signal to the thyristor S1, and S1 conducts immediately.

[0169] Circuit topology change: After S1 conducts, the varistor (MOV) is directly connected in parallel across the IGBT through S1, forming a circuit structure of "IGBT in parallel with MOV", providing a path for energy commutation.

[0170] 2. Current commutation: Smooth transition from IGBT to MOV

[0171] Current evolution law:

[0172] Before conduction (t < t3): The loop current (the main switch current, that is, the collector current of the IGBT) is mainly borne by the IGBT and is used to absorb the inductor energy;

[0173] After conduction (t3 - t4): Due to the low-resistance characteristic of the MOV in parallel (the leakage current is small when the voltage is lower than but the voltage has increased due to the turn-off process at this time, and the MOV enters the conduction region), the current begins to gradually transfer from the IGBT branch to the MOV branch, forming the current of the MOV .

[0174] Continuous switching results: (IGBT current) with The MOV current increases and decreases synchronously until... This completes the transfer of all energy.

[0175] 3. Key Breakthrough: Active Clamping Circuit Eliminates Voltage Spikes

[0176] The pain point of traditional solutions: If energy is absorbed directly in parallel via MOV, the current rapidly commutates from the IGBT to the MOV, due to the line inductance... The property of "impeding sudden change in current" ( This can produce steep voltage spikes (which may exceed the IGBT's withstand voltage limit), leading to device damage.

[0177] Optimizations of this invention:

[0178] In Phase 3, the active clamping module (including transient voltage suppression diodes) continues to operate, dynamically adjusting the voltage across the IGBT through voltage feedback:

[0179] Limit the voltage rise slope (dv / dt) to make the voltage change rate much lower than that of traditional solutions; force the voltage clamped at a preset threshold (such as 90% of the IGBT withstand voltage) to ensure that there are no voltage spikes during the commutation process.

[0180] Therefore, the current can be "slowly commutated" to the MOV, avoiding device stress overload caused by spikes.

[0181] 4. Energy absorption: The MOV absorbs the residual inductance energy.

[0182] Energy source: The remaining energy in the circuit at this time is mainly due to the line inductance. The stored magnetic field energy (due to the partial consumption of energy in stages one and two, and the current) The current has decreased since the initial shutdown. For example, in an experiment using an FZ600R17KE4IGBT module, the experimental waveform shows that, under normal circumstances, the current decreases to... Half of that, meaning if the fault current is 600A, then the MOV absorbs energy at 300A.

[0183] Absorption path: As the current flows from Gradually switch to All the remaining energy of the inductor is absorbed by the MOV (the MOV utilizes its nonlinear current-voltage characteristics to exhibit a low-resistance state under high voltage, thus rapidly consuming energy).

[0184] IGBT load reduction: After MOV connection, the IGBT current... The temperature drops rapidly, no longer subject to energy surges, and the junction temperature stops rising, thus avoiding damage due to overheating.

[0185] 5. Core objective of this phase: Balancing "protecting IGBTs" with "reducing MOV impact"

[0186] Since some energy has been absorbed by the IGBT itself in stages one and two, the current during commutation in stage three... The current surge intensity has been significantly reduced (usually to less than 50% of the initial shutdown current), and the current surge intensity that the MOV can withstand is much lower than that of the traditional solution (the MOV in the traditional solution needs to absorb all the initial energy).

[0187] This "step-by-step energy absorption" design not only protects the IGBT (avoiding overheating) but also reduces the number and intensity of MOV impacts, directly extending the MOV's lifespan (referencing the degradation curve: lifespan increases by approximately 10 times under a 200A impact), ultimately increasing the rated breaking capacity of the SSCB.

[0188] This stage achieves "safe energy transfer from IGBT to MOV" through the coordinated action of "thyristor conduction → MOV parallel connection → active clamping peak suppression → smooth energy commutation". It not only solves the IGBT overheating problem, but also overcomes the voltage spike defect of traditional solutions. It is the core execution link of this invention to improve the number of interruptions.

[0189] Phase 4 (t4-t) n ):

[0190] 1. Core state: The MOV has completed energy absorption and entered the leakage current region.

[0191] Energy absorption endpoint t4: After the commutation in stage three, the remaining energy in the line inductance has been completely absorbed by the MOV (varistor), 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).

[0192] Leakage current region is defined as the region where the voltage across the MOV drops to near its 100mA nominal voltage. At this point, 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 a small current to pass through), hence it is called the "leakage current region".

[0193] 2. Characteristics of voltage and current:

[0194] Here This refers to the voltage across the MOV (since the MOV is connected in parallel with the main circuit at this time, it is approximately equal to the residual voltage of the bus). After energy absorption is complete, the voltage stabilizes at... Nearby – this is an inherent characteristic of MOVs: when the voltage is below this value, the leakage current decreases sharply as the voltage decreases; when the voltage is equal to this value, the leakage current stabilizes at around 100mA.

[0195] 3. Key Logic for Automatic SCR Shutdown

[0196] 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).

[0197] 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.

[0198] 4. Core objective of this phase: System reset to prepare for the next breakdown.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] This design transforms what was originally only applicable to V... 1mA MOV upgraded to V MOV_100mASimultaneously, 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.

[0203] Comparing the MOV life curves, in this invention, the current absorbed by the MOV from the start of shutdown has already decreased by half, so the energy absorbed by the MOV at this time is at least half that of the traditional solution.

[0204] For example, such as Figure 8 As shown, observe the degradation curve of the FTR40D112KJ varistor. Under a 500A 100µs impact, the varistor's VA changes after 1000 cycles. 1mA It will decrease by 10%; if subjected to a 200A 100us impact, its V will decrease after 10,000 cycles. 1mA It will decrease by 10%. Therefore, this invention can increase the service life of MOV by about ten times, and the rated breaking capacity of solid-state circuit breakers is basically consistent with this increase.

[0205] In summary, this invention cleverly achieves the rational allocation of turn-off energy during the solid-state switch's turn-off process by introducing a physical information neural network into the design of the solid-state circuit breaker. It allocates a small amount of energy to the power device while ensuring its junction temperature does not exceed the limit junction temperature, and allocates the remaining large amount of energy to the varistor. While ensuring the power device is not damaged, it reduces the current surge experienced by the varistor, thus significantly increasing the varistor's lifespan with almost no increase in cost. Furthermore, the use of a varistor connected in series with a thyristor greatly increases the rated voltage of the solid-state circuit breaker, further improving efficiency.

[0206] Example 3

[0207] This embodiment also provides an electronic device, see reference. Figure 9 It includes a memory 404 and a processor 402, wherein 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.

[0208] Specifically, the processor 402 may include a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement embodiments of the present invention.

[0209] Memory 404 may include a mass storage device for data or instructions. For example, and not limitingly, memory 404 may include a hard disk drive (HDD), a floppy disk drive, a solid-state drive (SSD), flash memory, an optical disk drive, a magneto-optical disk drive, magnetic tape, or a Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 404 may include removable or non-removable (or fixed) media. Where appropriate, memory 404 may be internal or external to a data processing device. In a particular embodiment, memory 404 is non-volatile memory. In a particular embodiment, memory 404 includes read-only memory (ROM) and random access memory (RAM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable read-only memory (PROM), an erasable read-only memory (EPROM), an electrically erasable read-only memory (EEPROM), an electrically alterable read-only memory (EAROM), or flash memory, or a combination of two or more of these. Where appropriate, the RAM can be Static Random-Access Memory (SRAM) or Dynamic Random-Access Memory (DRAM). DRAM can be Fast Page Mode Dynamic Random-Access Memory (FPMDRAM), Extended Data Out Dynamic Random-Access Memory (EDODRAM), Synchronous Dynamic Random-Access Memory (SDRAM), etc.

[0210] The memory 404 can be used to store or cache various data files that need to be processed and / or communicated, as well as possible computer program instructions executed by the processor 402.

[0211] The processor 402 reads and executes computer program instructions stored in the memory 404 to implement any of the methods described in the above embodiments for increasing the rated current breaking capacity of a DC solid-state circuit breaker.

[0212] Optionally, the electronic device may further include a transmission device 406 and an input / output device 408, wherein the transmission device 406 is connected to the processor 402, and the input / output device 408 is connected to the processor 402.

[0213] The transmission device 406 can be used to receive or send data via a network. Specific examples of the network described above may include wired or wireless networks provided by the communication provider of the electronic device. In one example, the transmission device includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 406 may be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0214] Input / output device 408 is used to input or output information.

[0215] Example 4

[0216] This embodiment also provides a readable storage medium storing a computer program, the computer program including program code for controlling a process to execute the process, the process including a method for increasing the rated current breaking number of a DC solid-state circuit breaker according to Embodiment 1.

[0217] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0218] Generally, various embodiments can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects of the invention can be implemented in hardware, while others can be implemented by firmware or software executed by a controller, microprocessor, or other computing device, but the invention is not limited thereto. Although various aspects of the invention may be shown and described as block diagrams, flowcharts, or using some other graphical representation, it should be understood that, by way of non-limiting example, these blocks, apparatuses, systems, techniques, or methods described herein can be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0219] Embodiments of the present invention can be implemented by computer software, which may be executable by a data processor of a mobile device, such as a processor entity, or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products) including software routines, applets, and / or macros can be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. The computer program product may include one or more computer-executable components configured to perform the embodiments when the program is run. The one or more computer-executable components may be at least one piece of software code or a portion thereof. Additionally, it should be noted in this respect that, as Figure 2 Any box in the logical flow can represent a program step, or interconnected logic circuits, boxes and functions, or a combination of program steps and logic circuits, boxes and functions. Software can be stored on physical media such as memory chips or blocks of storage implemented within a processor, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and their data variants, CDs, etc. The physical medium is a non-transient medium.

[0220] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0221] The above embodiments are merely illustrative of several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by 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 power device 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 electrically connected with the driving side of the power device, for suppressing overvoltage during the off process of the power device to prevent 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-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.

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 power device 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 to 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 off energy 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 decreases 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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