Coordinated Optimization Method for IGBT Peak Voltage Suppression

Abstract

This invention discloses a coordinated optimization method for suppressing IGBT peak voltage, comprising the following steps: establishing an equivalent model of the main topology of a mining frequency converter with stray inductance; establishing a behavioral model of the IGBT; establishing the correspondence between the structural parameters of the busbar and the stray inductance; establishing the correspondence between the structural parameters of the busbar and the IGBT peak voltage and IGBT power loss; establishing the correspondence between the gate drive resistor, the structural parameters of the busbar, and the IGBT peak voltage and IGBT power loss; determining the optimal solution for the absorption capacitor; using the gate drive resistor and the structural parameters of the busbar as decision variables, performing multi-objective extreme value optimization for the IGBT peak voltage, the highest junction temperature, and the highest surface temperature of the heat sink, and finally determining the optimal solution for the gate drive resistor and the structural parameters of the busbar. This invention can effectively reduce the IGBT peak voltage caused by stray inductance, improve voltage oscillation, and provide a guarantee for the safe, stable, and reliable operation of the mining frequency converter.

Description

Technical Field

[0001] This invention relates to the field of insulated gate bipolar transistor (IGBT) technology, and more particularly to a coordinated optimization method for suppressing IGBT spike voltage. Background Technology

[0002] An insulated-gate bipolar transistor (IGBT) is a composite, fully controllable, voltage-driven power semiconductor device composed of a bipolar transistor and an insulated-gate field-effect transistor. It combines the advantages of high input impedance of a metal-oxide-semiconductor field-effect transistor and low on-state voltage drop of a power transistor.

[0003] The reliability of IGBTs plays a crucial role in ensuring the stable operation of mining frequency converters, improving coal mine safety, and promoting the efficient development and energy conservation of the coal industry. Because various components of mining frequency converters have stray inductance (which is generally related to topology, component layout, processing, and assembly techniques), IGBTs can generate high voltage spikes during switching transients. The long-term cyclic action of significant electro-thermal stress on the IGBTs can lead to fatigue, random failure, and even complete failure of the mining frequency converter, while also accelerating the aging of the motor insulation.

[0004] Methods for suppressing voltage spikes include increasing the gate resistance, optimizing the bus structure, designing snubber circuits, and optimizing snubber capacitor parameters. Existing suppression methods only address individual measures and do not reveal strategies for combining multiple suppression measures to effectively suppress voltage spikes. However, these suppression methods often have contradictory relationships, and simply combining them does not achieve optimal suppression. Therefore, there is an urgent need to propose a coordinated optimization method for IGBT voltage spike suppression, capable of coordinating multiple suppression measures to achieve the best results. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the issue of stray inductance causing high voltage spikes in IGBTs, leading to performance degradation. This invention provides a coordinated optimization method for suppressing IGBT voltage spikes, which can effectively reduce IGBT voltage spikes caused by stray inductance and improve voltage oscillation phenomena.

[0006] The technical solution adopted by this invention to solve its technical problem is: a coordinated optimization method for IGBT peak voltage suppression, comprising the following steps:

[0007] S1. Establish an equivalent model of the main topology of a mining frequency converter with stray inductance;

[0008] S2. Establish the behavioral model of IGBT;

[0009] S3. Establish the correspondence between the structural parameters of the busbar and the stray inductance.

[0010] S4. Establish the correspondence between the structural parameters of the busbar and the peak voltage of the IGBT; B. Establish the correspondence between the structural parameters of the busbar and the power loss of the IGBT; C.

[0011] S5. Establish the correspondence between the gate drive resistor, the structural parameters of the busbar, and the peak voltage of the IGBT; D. Establish the correspondence between the gate drive resistor, the structural parameters of the busbar, and the power loss of the IGBT. E.

[0012] S6. Design an absorption circuit and determine the optimal solution for the absorption capacitor;

[0013] S7. Combined with the water-cooled heat dissipation system of the mining frequency converter, the power loss of the IGBT is converted into the highest junction temperature and the highest surface temperature of the heat sink.

[0014] S8. Using the gate drive resistor and busbar structural parameters as decision variables, perform multi-objective extreme value optimization on the IGBT peak voltage, maximum junction temperature and maximum surface temperature of the heat sink, and finally determine the optimal solution for the gate drive resistor and busbar structural parameters.

[0015] Furthermore, the equivalent model includes: a DC capacitor module, a DC busbar positive stray inductor, a DC busbar negative stray inductor, an AC-DC connection busbar positive stray inductor, an AC-DC connection busbar negative stray inductor, and an AC busbar module. One end of the DC capacitor module is connected to the DC busbar positive stray inductor, and the other end of the DC capacitor module is connected to the DC busbar negative stray inductor. The DC busbar positive stray inductor is connected to the AC-DC connection busbar positive stray inductor, and the DC busbar negative stray inductor is connected to the AC-DC connection busbar negative stray inductor. The AC-DC connection busbar positive stray inductor is connected to one end of the AC busbar module, and the AC-DC connection busbar negative stray inductor is connected to the other end of the AC busbar module. The AC busbar module is connected to three-phase AC power.

[0016] Furthermore, the AC busbar module (6) includes: a first IGBT, a second IGBT, a third IGBT, a fourth IGBT, a fifth IGBT, a sixth IGBT, and a stray inductor L. U++ Stray inductance L V++ Stray inductance L W++ Stray inductance L U+～ Stray inductance L V+～ Stray inductance L W+～ Stray inductance L U～+ Stray inductance L V～+ Stray inductance LW～+ Stray inductance L U-- Stray inductance L V-- and stray inductance L W-- The stray inductance L U++ Stray inductance L U+～ The stray inductance L is connected to the positive and negative terminals of the first IGBT respectively. V++ Stray inductance L V+～ The stray inductance L is connected to the positive and negative terminals of the third IGBT respectively. W++ Stray inductance L W+～ The stray inductance L is connected to the positive and negative terminals of the fifth IGBT respectively. U～+ Stray inductance L U-- The stray inductance L is connected to the positive and negative terminals of the second IGBT respectively. V～+ Stray inductance L V-- The stray inductance L is connected to the positive and negative terminals of the fourth IGBT respectively. W～+ Stray inductance L W-- Connect to the positive and negative terminals of the sixth IGBT.

[0017] Furthermore, the corresponding relationship A is as follows: the stray inductance is positively correlated with the length of the busbar, and the stray inductance is negatively correlated with the width of the busbar.

[0018] Furthermore, the corresponding relationship B is: the IGBT peak voltage decreases as the busbar length decreases, and the IGBT peak voltage decreases as the busbar width increases; the corresponding relationship C is: the IGBT power loss decreases as the busbar length decreases, and the IGBT power loss decreases as the busbar width increases, and the relationship between the IGBT power loss and the busbar structural parameters is linear.

[0019] Furthermore, the corresponding relationship D is: the IGBT peak voltage decreases as the gate drive resistor value increases, and the IGBT peak voltage decreases as the busbar length decreases; the corresponding relationship E is: the IGBT power loss increases as the gate drive resistor value increases, and the IGBT power loss decreases as the busbar length decreases.

[0020] Furthermore, the multi-objective optimization employs a neural network-non-dominated sorting genetic fusion algorithm with an elitist strategy, specifically including:

[0021] S81. The neural network model is trained using simulation data of decision variables and optimization objectives to obtain a neural network prediction model;

[0022] S82. Using the predicted target output by the neural network prediction model, calculate the non-dominated ranking and crowding degree;

[0023] S83. Set the population size N, maximum number of iterations m, crossover probability, and mutation probability;

[0024] S84, generate subpopulation;

[0025] S85. Merge the child population and the parent population, and recalculate the non-dominated ordering and crowding.

[0026] S86. Generate a new parent population;

[0027] S87. Determine whether the current iteration count has reached the maximum iteration count. If yes, proceed to step S88; otherwise, return to step S84.

[0028] S88. Determine the Pareto optimal solution set.

[0029] Furthermore, a range is set for the maximum junction temperature and the maximum surface temperature of the heat sink. Within this range, the minimum value of the IGBT peak voltage is selected. Based on the minimum value of the IGBT peak voltage, the optimal solution for the gate drive resistor and the structural parameters of the busbar is determined.

[0030] Furthermore, when the highest surface temperature of the heat sink is 55℃~65℃ and the highest junction temperature is 74℃~80℃, the minimum value of the IGBT peak voltage is 1861V. At this time, the gate drive resistor is 5Ω, the length of the AC busbar is 300mm, and the width of the AC busbar is 200mm.

[0031] Furthermore, the neural network model has 6 hidden layers, each with 200 neurons, and is trained 20,000 times.

[0032] The beneficial effects of this invention are that the coordination optimization method of this invention can effectively reduce the IGBT peak voltage caused by stray inductance, improve the voltage oscillation phenomenon, and provide a guarantee for the safe, stable and reliable operation of mining frequency converters. It has the characteristics of multi-physics field analysis, intelligent auxiliary decision-making and optimal comprehensive performance. Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Figure 1 This is a flowchart of the coordination optimization method of the present invention.

[0035] Figure 2 This is a schematic diagram of the equivalent model of the present invention.

[0036] Figure 3 These are the IGBT collector-emitter voltage waveforms under different load conditions according to the present invention.

[0037] Figure 4This is the IGBT switching transient curve of the present invention.

[0038] Figure 5 The length, width, and L of the AC busbar of this invention U / V / W++ , LU / V / W～+ The correspondence diagram.

[0039] Figure 6 This is a diagram showing the correspondence between the length and width of the AC busbar and the peak voltage of the IGBT in this invention.

[0040] Figure 7 This is a diagram showing the correspondence between the length and width of the AC busbar and the power loss of the IGBT in this invention.

[0041] Figure 8 This is a diagram showing the relationship between the gate drive resistor, the length of the AC busbar, and the peak voltage of the IGBT in this invention.

[0042] Figure 9 This is a diagram showing the relationship between the gate drive resistor, the length of the AC busbar, and the power loss of the IGBT in this invention.

[0043] Figure 10 This is a schematic diagram of the absorption circuit of the present invention.

[0044] Figure 11 This is a waveform diagram of IGBT turn-off under different absorption capacitors according to the present invention.

[0045] Figure 12 This is a diagram showing the relationship between the gate drive resistor, the length of the AC busbar, and the IGBT peak voltage after the absorption circuit is adopted in this invention.

[0046] Figure 13 This is a diagram showing the relationship between the gate drive resistor, the length of the AC busbar, and the IGBT power loss after the adoption of the absorption circuit in this invention.

[0047] Figure 14 This is a flowchart of the multi-objective optimization process of the present invention.

[0048] Figure 15 This is a schematic diagram of the Pareto optimal solution set of the present invention.

[0049] Figure 16 This is an experimental waveform diagram of the IGBT turn-off voltage of the present invention.

[0050] In the diagram: 1. DC capacitor module; 2. DC busbar positive stray inductance; 3. DC busbar negative stray inductance; 4. AC-DC connection busbar positive stray inductance; 5. AC-DC connection busbar negative stray inductance; 6. AC busbar module. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0052] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] like Figure 1 As shown, the coordinated optimization method for IGBT peak voltage suppression of the present invention includes the following steps:

[0055] S1. Establish an equivalent model of the main topology of a mining frequency converter with stray inductance.

[0056] S2. Establish the behavioral model of IGBT.

[0057] S3. Establish the correspondence between the structural parameters of the busbar and the stray inductance.

[0058] S4. Establish the correspondence between the structural parameters of the busbar and the peak voltage of the IGBT; B. Establish the correspondence between the structural parameters of the busbar and the power loss of the IGBT.

[0059] S5. Establish the correspondence between the gate drive resistor, the structural parameters of the busbar and the peak voltage of the IGBT; D. Establish the correspondence between the gate drive resistor, the structural parameters of the busbar and the power loss of the IGBT. E.

[0060] S6. Design an absorption circuit and determine the optimal solution for the absorption capacitor.

[0061] S7. Combined with the water-cooled heat dissipation system of the mining frequency converter, the power loss of the IGBT is converted into the highest junction temperature and the highest surface temperature of the heat sink.

[0062] S8. Using the gate drive resistor and busbar structural parameters as decision variables, perform multi-objective extreme value optimization on the IGBT peak voltage, the highest junction temperature, and the highest surface temperature of the heat sink, and finally determine the optimal solution for the gate drive resistor and busbar structural parameters.

[0063] This invention establishes a correlation between the structural parameters of the busbar, the gate drive resistance, and the IGBT peak voltage and IGBT power loss. It further suppresses IGBT peak voltage through an absorption circuit. The optimal values ​​of the busbar structural parameters and the gate drive resistance are obtained through an algorithm. This method integrates multiple factors affecting IGBT peak voltage and performs coordinated optimization, effectively reducing IGBT peak voltage caused by stray inductance, improving voltage oscillation, and ensuring the safe, stable, and reliable operation of mining frequency converters.

[0064] For example, taking a four-quadrant frequency converter as an example, an equivalent model of the main topology of a mining frequency converter with stray inductance is established by introducing DC capacitors, IGBTs, and stray inductances of various busbars. Figure 2 As shown, the equivalent model includes: DC capacitor module 1, DC busbar positive stray inductance 2, DC busbar negative stray inductance 3, AC-DC connection busbar positive stray inductance 4, AC-DC connection busbar negative stray inductance 5, and AC busbar module 6. One end of DC capacitor module 1 is connected to DC busbar positive stray inductance 2, and the other end of DC capacitor module 1 is connected to DC busbar negative stray inductance 3. DC busbar positive stray inductance 2 is connected to AC-DC connection busbar positive stray inductance 4, DC busbar negative stray inductance 3 is connected to AC-DC connection busbar negative stray inductance 5, AC-DC connection busbar positive stray inductance 4 is connected to AC busbar module 6, and AC-DC connection busbar negative stray inductance 5 is connected to the other end of AC busbar module 6. AC busbar module 6 is connected to three-phase AC power. C is the DC capacitor, L... C The stray inductance of a DC capacitor; L DC1+ L DC2+ and L DC1- L DC2- The stray inductance of the positive and negative terminals of the DC bus; L DCU+ L UV+ L VW+ and L DCU- L UV- L VW- These are the stray inductances of the positive and negative terminals of the AC-DC connection busbar, respectively.

[0065] The AC busbar module 6 includes: a first IGBT, a second IGBT, a third IGBT, a fourth IGBT, a fifth IGBT, a sixth IGBT, and a stray inductor L. U++ Stray inductance L V++ Stray inductance L W++ Stray inductance L U+～ Stray inductance L V+～ Stray inductance L W+～ Stray inductance L U～+ Stray inductance L V～+ Stray inductance L W～+ Stray inductance L U-- Stray inductance L V-- and stray inductance L W-- Stray inductance L U++ Stray inductance L U+～ The stray inductance L is connected to the positive and negative terminals of the first IGBT respectively. V++ Stray inductance L V+～ The stray inductance L is connected to the positive and negative terminals of the third IGBT respectively. W++ Stray inductance L W+～ Connected to the positive and negative terminals of the fifth IGBT respectively, stray inductance L U～+ Stray inductance L U-- The stray inductance L is connected to the positive and negative terminals of the second IGBT respectively. V～+ Stray inductance L V-- Connected to the positive and negative terminals of the fourth IGBT respectively, stray inductance L W～+ Stray inductance L W-- Connect to the positive and negative terminals of the sixth IGBT.

[0066] Various types of stray inductance are introduced into the equivalent model. For ease of analysis, the stray inductance of the AC busbar, AC-DC connection busbar, and DC busbar can be extracted using ANSYS Q3D software. Taking the AC busbar as an example, due to the skin effect and proximity effect affecting the electromagnetic field distribution in the converter circuit, the stray inductance is relatively high at low frequencies and gradually decreases at high frequencies. When the excitation frequency increases to 1.5MHz, the stray inductance tends to stabilize. For example, with an excitation frequency of 1.5MHz, the stray inductance of each part of the AC busbar, AC-DC connection busbar, and DC busbar can be obtained (see Table 1).

[0067] Table 1

[0068]

[0069] For example, a behavioral model of the IGBT can be established using ANSYS Simplorer software, and a corresponding simulation circuit can be built based on the equivalent model. With the input three-phase AC voltage set to 1140V, the fundamental frequency to 50Hz, the switching frequency to 2kHz, and the gate drive resistor to 8Ω, the collector-emitter voltage waveforms of the IGBT are obtained under no-load, half-load, and full-load conditions (e.g., ...). Figure 3 As shown, taking the first IGBT as an example, by Figure 3 It can be seen that the peak voltage of the IGBT increases with the increase of the load, under full-load conditions (such as...). Figure 3 As shown in (c), the IGBT peak voltage reaches 2854V, exceeding 77% of the DC bus voltage. Figure 4 As shown, the IGBT switching transient curves of the main topology circuit of the mining frequency converter are different when there is no stray inductance and when stray inductance is introduced. By integrating the switching transient curves and taking a single pulse period, the calculation results of IGBT losses can be obtained (see Table 2). As can be seen from Table 2, after introducing stray inductance into the main topology of the mining frequency converter, the IGBT turn-on loss will decrease, while the turn-off loss, conduction loss, and total power loss will increase.

[0070] Table 2

[0071] type Turn-on loss Turn-off losses Conduction loss Total power loss Stray inductance 467W 449W 687W 1603W Introducing stray inductance 387W 694W 820W 1901W

[0072] In addition, the temperature distribution of the water-cooled heat dissipation system of the mining frequency converter can be simulated using ANSYS Icepak software to analyze the impact of stray inductance on the heat dissipation performance of IGBTs. For example, with the ambient temperature set at 30℃ and the water flow rate at 18L / min, after introducing stray inductance into the main topology circuit of the mining frequency converter, the highest surface temperature of the heat sink, the highest junction temperature of the IGBT, and the outlet temperature are 72℃, 84℃, and 38℃, respectively, which are 11%, 12%, and 3% higher than when there is no stray inductance.

[0073] Therefore, a large stray inductance will cause a sharp increase in IGBT peak voltage, which will increase the total power loss of the IGBT, cause overheating, and easily lead to fatigue failure.

[0074] For example, IGBT voltage spikes can be suppressed by optimizing the busbar structure parameters, increasing the gate drive resistance, and designing snubber circuits. However, how to coordinate these three measures to achieve the optimal effect in suppressing IGBT voltage spikes still needs further research.

[0075] According to Table 1, the stray inductance L of the AC busbar is... U / V / W++ L U / V / W～+ It is far greater than other stray inductances. Therefore, this invention uses AC busbar structural parameters as an example for explanation.

[0076] Specifically, the relationship A between the structural parameters of the busbar and the stray inductance is as follows: stray inductance is positively correlated with the length of the busbar, and negatively correlated with the width of the busbar. For example, the structural parameters of the busbar include its length and width. Figure 5 (a) shows the stray inductance L U / V / W++ The relationship between the length and width of the AC busbar and the stray inductance L can be seen from the figure. U / V / W++ The stray inductance L decreases as the length of the AC busbar decreases. U / V / W++ It decreases as the width of the AC busbar increases. From Figure 5 From (b), we can see that the stray inductance L U / V / W～+ The stray inductance L decreases as the length of the AC busbar decreases. U / V / W～+ The stray inductance decreases as the width of the AC busbar increases. Therefore, stray inductance is positively correlated with busbar length and negatively correlated with busbar width. This is because a shorter busbar results in a smaller current coupling loop area, leading to a lower stray inductance; a wider busbar means more stray inductors are connected in parallel, thus reducing the total stray inductance. In other words, during design, the busbar should be as short as possible and as wide as possible to minimize stray inductance.

[0077] Specifically, the relationship B between the busbar structural parameters and the IGBT peak voltage is as follows: the IGBT peak voltage decreases as the busbar length decreases, and the IGBT peak voltage decreases as the busbar width increases. The relationship C between the busbar structural parameters and the IGBT power loss is as follows: the IGBT power loss decreases as the busbar length decreases, and the IGBT power loss decreases as the busbar width increases, and the relationship between the IGBT power loss and the busbar structural parameters is linear. For ease of analysis, a fixed-value gate drive resistor is used, and the changes in IGBT peak voltage and IGBT power loss are observed by changing the structural parameters of the AC busbar. Figure 6 The figure illustrates the relationship between IGBT peak voltage and the structural parameters of the AC busbar. As shown in the figure, the IGBT peak voltage decreases as the length of the AC busbar decreases, and decreases as the width of the AC busbar increases. Figure 7The figure illustrates the relationship between IGBT power loss and the structural parameters of the AC busbar. As shown, IGBT power loss decreases with decreasing busbar length and increases with increasing busbar width, exhibiting a linear relationship between power loss and busbar structural parameters. In other words, shorter busbar length results in lower IGBT peak voltage and power loss, while wider busbar width also leads to lower peak voltage and power loss. Since the width of the AC busbar has almost no impact on IGBT layout and heat dissipation performance, a width of 200mm is optimally chosen to reduce decision variables during the optimization process.

[0078] Specifically, such as Figure 8 and Figure 9 As shown, the relationship D between the gate drive resistance, busbar structural parameters, and IGBT peak voltage is as follows: the IGBT peak voltage decreases as the gate drive resistance increases, and decreases as the busbar length decreases. The relationship E between the gate drive resistance, busbar structural parameters, and IGBT power loss is as follows: IGBT power loss increases as the gate drive resistance increases, and decreases as the busbar length decreases. It should be noted that increasing the gate drive resistance can reduce the rate of current change, thereby reducing the IGBT peak voltage. Figure 8 It can be seen that the IGBT peak voltage decreases as the gate drive resistor value increases. When the gate drive resistor value is 4Ω, the IGBT peak voltage is 3104V. Increasing the gate drive resistor value to 16Ω reduces the IGBT peak voltage to 2428V. However, due to... Figure 9 It is known that as the gate drive resistor value increases, the IGBT power loss also increases (when the gate drive resistor value is 16Ω, the IGBT power loss is approximately 2000W). Therefore, it is necessary to find an optimal gate drive resistor value to balance the IGBT peak voltage and the IGBT power loss.

[0079] The absorption circuit can also suppress IGBT voltage spikes. In this embodiment, the absorption circuit uses diodes to clamp transient voltages, thereby reducing voltage resonance caused by the filter capacitor. Figure 10 As shown, the absorption circuit includes absorption capacitors C1 and C2, diodes D1, D2, D3, and D4, and inductors L1 and L2. The size of the absorption capacitors has different effects on suppressing IGBT peak voltages. For example, absorption capacitors of 0.5μF, 1μF, 2μF, and 3μF, and an inductor of 0.1μH were selected to analyze the IGBT turn-off waveforms with different absorption capacitors. Figure 11As shown, with the increase of the absorption capacitor, the IGBT peak voltage gradually decreases, the oscillation period gradually increases, and the oscillation phenomenon weakens. However, when the absorption capacitor is 2μF and 3μF, it is found that further increasing the absorption capacitor has no significant improvement on the suppression effect of the IGBT peak voltage. Therefore, considering the size and cost, as well as the computational load of the optimization coordination process, the absorption capacitor of 2μF can be preferred.

[0080] like Figure 12 and Figure 13 As shown, after adding the snubber circuit, the IGBT spike voltage decreases as the gate drive resistor value increases. Increasing the gate drive resistor value to 16Ω reduces the IGBT spike voltage to approximately 1660V, compared to the voltage without a snubber circuit. Figure 8 Compared to the previous method, the IGBT peak voltage can be further reduced. Simultaneously, adding the snubber circuit also reduces IGBT power loss; with a gate drive resistor of 16Ω, the IGBT power loss is approximately 1650W. In other words, the snubber circuit not only suppresses IGBT peak voltage but also reduces IGBT power loss.

[0081] This study obtains the correspondence between the gate drive resistance, busbar structural parameters, and IGBT peak voltage after adding the absorption circuit, as well as the correspondence between the gate drive resistance, busbar structural parameters, and IGBT power loss. Combined with the water-cooling system of the mining frequency converter, simulation analysis shows that IGBT power loss is converted into the highest junction temperature and the highest surface temperature of the heat sink. The higher the IGBT power loss, the higher the converted highest junction temperature and the highest surface temperature of the heat sink. As the length of the AC busbar decreases, the longitudinal spacing of the IGBTs decreases, and the highest surface temperature of the heat sink increases. Therefore, the gate drive resistance and busbar structural parameters can be used as decision variables. A neural network-elite strategy non-dominated sorting genetic fusion algorithm is employed to perform multi-objective optimization of the IGBT peak voltage, highest junction temperature, and highest surface temperature of the heat sink. The changes in these three parameters are contradictory, exhibiting an inverse relationship (i.e., a decrease in one parameter leads to an increase in another). Therefore, it is necessary to use a neural network-elite strategy non-dominated sorting genetic fusion algorithm to find an optimal solution that balances the relationship between the three parameters.

[0082] Specifically, such as Figure 14 As shown, the multi-objective extremum optimization process includes:

[0083] S81. The neural network model is trained using simulation data of decision variables and optimization objectives to obtain a neural network prediction model.

[0084] S82. Using the predicted target output by the neural network prediction model, calculate the non-dominated ranking and crowding degree.

[0085] S83. Set the population size N, maximum number of iterations m, crossover probability, and mutation probability.

[0086] S84, generate subpopulation.

[0087] S85. Merge the child population and the parent population, and recalculate the non-dominated ordering and crowding.

[0088] S86, Generate a new parent population.

[0089] S87. Determine whether the current iteration count has reached the maximum iteration count. If yes, proceed to step S88; otherwise, return to step S84.

[0090] S88. Determine the Pareto optimal solution set.

[0091] It should be noted that the neural network model has 6 hidden layers, each with 200 neurons, and is trained 20,000 times. The neural network model is trained using simulation data of decision variables (gate drive resistance, busbar structural parameters) and optimization objectives (IGBT peak voltage, maximum junction temperature, maximum surface temperature of the heatsink), enabling the trained neural network prediction model to accurately predict the output value of the optimization objective (the accuracy of the neural network prediction model in this embodiment reaches 99.94%). Using the predicted target value output by the neural network prediction model, non-dominated ordering and crowding are calculated. Non-dominated ordering refers to the process of decomposing the solution set into Pareto fronts of different orders. Crowding can be represented by crowding distance, which is used to measure the quality of solutions within the same front. A crowding distance can be assigned to each solution to ensure that the obtained Pareto optimal solutions are as dispersed as possible in the target space. For example, the population size is set to 50, the maximum number of iterations is set to 500, the crossover probability is set to 0.9, and the mutation probability is set to 0.1. The final Pareto optimal solution set is as follows: Figure 15 As shown, the dashed area represents the mapping interval corresponding to the design optimization objective. Figure 15 It is known that within the range of the highest surface temperature of the heat sink (55℃~65℃) and the highest junction temperature of the IGBT (74℃~80℃), the minimum peak voltage of the IGBT is 1861V. At this point, the gate drive resistor is preferably 5Ω, and the AC busbar is preferably 300mm long and 200mm wide.

[0092] It should be noted that the neural network-nondominated sorting genetic algorithm with elitist strategy is a fusion of two algorithms. It utilizes the powerful nonlinear interpolation and self-learning capabilities of neural networks (BP) to train the model sample data, combined with the global optimization and multi-objective optimization capabilities of the nondominated sorting genetic algorithm with elitist strategy (NSGAII). Compared to the traditional NSGA algorithm, NSGAII introduces a quicksort method to construct the nondominated solution set and an elitist retention strategy, avoiding the determination and dynamic adjustment and modification of shared parameters. It also uses crowding density instead of shared parameters to maintain the distribution and diversity of the solution population, which helps improve the efficiency of the optimization algorithm and reduce its computational time complexity.

[0093] The coordinated optimization method of this invention, based on multiphysics simulation analysis, utilizes a neural network-non-dominated sorting genetic fusion algorithm with an elite strategy to achieve comprehensive optimization of IGBT peak voltage, maximum junction temperature, and maximum surface temperature of the heat sink. While suppressing IGBT peak voltage, it minimizes IGBT power loss, thereby optimizing IGBT performance and ensuring the stable operation of the mining frequency converter.

[0094] To verify the effectiveness of the coordinated optimization method of this invention in suppressing IGBT peak voltage, an experiment was conducted by building a mining frequency converter loading test platform. Figure 16 The figure shows the experimental waveform of the IGBT turn-off voltage under full-load conditions. Without suppression measures, the IGBT peak voltage of the mining frequency converter reaches as high as 2856V. After using the coordinated optimization method, the IGBT peak voltage is reduced to 1856V, a decrease of 53.9%, significantly improving the operational reliability of the IGBT and the mining frequency converter.

[0095] In summary, the coordinated optimization method of this invention analyzes the impact of busbar structural parameters and gate drive resistance on IGBT peak voltage and IGBT power loss. It reveals that a large stray inductance leads to a sharp increase in IGBT peak voltage, increasing the total power loss of the IGBT and causing overheating, which can easily lead to IGBT fatigue failure. The method designs and optimizes the absorption circuit, obtaining the corresponding relationship between the busbar structural parameters, gate drive resistance, and IGBT peak voltage and power loss after adopting this absorption circuit. Finally, based on the correspondence, decision variables are selected, and a fusion algorithm is used to comprehensively optimize the IGBT peak voltage, maximum junction temperature, and maximum surface temperature of the heat sink. This method not only effectively reduces IGBT peak voltage caused by stray inductance and improves voltage oscillation, but also minimizes IGBT power loss, ensuring the safe, stable, and reliable operation of mining frequency converters.

[0096] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A coordinated optimization method for suppressing IGBT peak voltage, characterized in that, Includes the following steps: S1. Establish an equivalent model of the main topology of a mining frequency converter with stray inductance; S2. Establish the behavioral model of IGBT; S3. Establish the correspondence between the structural parameters of the busbar and the stray inductance. S4. Establish the correspondence between the structural parameters of the busbar and the peak voltage of the IGBT; B. Establish the correspondence between the structural parameters of the busbar and the power loss of the IGBT; C. S5. Establish the correspondence between the gate drive resistor, the structural parameters of the busbar, and the IGBT peak voltage; Establish the correspondence between the gate drive resistor, the structural parameters of the busbar, and the IGBT power loss E; S6. Design an absorption circuit and determine the optimal solution for the absorption capacitor; S7. Obtain the correspondence between the gate drive resistance, the structural parameters of the busbar and the peak voltage of the IGBT after adding the absorption circuit, and the correspondence between the gate drive resistance, the structural parameters of the busbar and the power loss of the IGBT. Combined with the water-cooling heat dissipation system of the mining frequency converter, the power loss of the IGBT is converted into the highest junction temperature and the highest surface temperature of the heat sink. S8. Using the gate drive resistor and busbar structural parameters as decision variables, perform multi-objective extreme value optimization on the IGBT peak voltage, maximum junction temperature and maximum surface temperature of the heat sink, and finally determine the optimal solution for the gate drive resistor and busbar structural parameters.

2. The coordinated optimization method for IGBT peak voltage suppression as described in claim 1, characterized in that, The equivalent model includes: a DC capacitor module (1), a DC busbar positive stray inductor (2), a DC busbar negative stray inductor (3), an AC-DC connection busbar positive stray inductor (4), an AC-DC connection busbar negative stray inductor (5), and an AC busbar module (6). One end of the DC capacitor module (1) is connected to the DC busbar positive stray inductor (2), and the other end of the DC capacitor module (1) is connected to the DC busbar negative stray inductor (3). The positive stray inductor (2) of the busbar is connected to the positive stray inductor (4) of the AC-DC connection busbar, the negative stray inductor (3) of the DC busbar is connected to the negative stray inductor (5) of the AC-DC connection busbar, the positive stray inductor (4) of the AC-DC connection busbar is connected to one end of the AC busbar module (6), the negative stray inductor (5) of the AC-DC connection busbar is connected to the other end of the AC busbar module (6), and the AC busbar module (6) is connected to three-phase AC power.

3. The coordinated optimization method for IGBT peak voltage suppression as described in claim 2, characterized in that, The AC busbar module (6) includes: a first IGBT, a second IGBT, a third IGBT, a fourth IGBT, a fifth IGBT, a sixth IGBT, and a stray inductor L. U++ Stray inductance L V++ Stray inductance L W++ Stray inductance L U+～ Stray inductance L V+～ Stray inductance L W+～ Stray inductance L U～+ Stray inductance L V～+ Stray inductance L W～+ Stray inductance L U-- Stray inductance L V-- and stray inductance L W-- The stray inductance L U++ Stray inductance L U+～ The stray inductance L is connected to the positive and negative terminals of the first IGBT respectively. V++ Stray inductance L V+～ The stray inductance L is connected to the positive and negative terminals of the third IGBT respectively. W++ Stray inductance L W+～ The stray inductance L is connected to the positive and negative terminals of the fifth IGBT respectively. U～+ Stray inductance L U-- The stray inductance L is connected to the positive and negative terminals of the second IGBT respectively. V～+ Stray inductance L V-- The stray inductance L is connected to the positive and negative terminals of the fourth IGBT respectively. W～+ Stray inductance L W-- Connect to the positive and negative terminals of the sixth IGBT.

4. The coordinated optimization method for IGBT peak voltage suppression as described in claim 1, characterized in that, The corresponding relationship A is as follows: the stray inductance is positively correlated with the length of the busbar, and the stray inductance is negatively correlated with the width of the busbar.

5. The coordinated optimization method for IGBT peak voltage suppression as described in claim 4, characterized in that, The corresponding relationship B is: the IGBT peak voltage decreases as the busbar length decreases, and the IGBT peak voltage decreases as the busbar width increases; the corresponding relationship C is: the IGBT power loss decreases as the busbar length decreases, and the IGBT power loss decreases as the busbar width increases, and the relationship between the IGBT power loss and the busbar structural parameters is linear.

6. The coordinated optimization method for IGBT peak voltage suppression as described in claim 5, characterized in that, The corresponding relationship D is: the IGBT peak voltage decreases as the gate drive resistor value increases, and the IGBT peak voltage decreases as the busbar length decreases; the corresponding relationship E is: the IGBT power loss increases as the gate drive resistor value increases, and the IGBT power loss decreases as the busbar length decreases.

7. The coordinated optimization method for IGBT peak voltage suppression as described in claim 1, characterized in that, The multi-objective optimization employs a neural network-non-dominated sorting genetic fusion algorithm with an elitist strategy, specifically including: S81. The neural network model is trained using simulation data of decision variables and optimization objectives to obtain a neural network prediction model; S82. Using the predicted target output by the neural network prediction model, calculate the non-dominated ranking and crowding degree; S83. Set the population size N, maximum number of iterations m, crossover probability, and mutation probability; S84, generate subpopulation; S85. Merge the child population and the parent population, and recalculate the non-dominated ordering and crowding. S86. Generate a new parent population; S87. Determine whether the current iteration count has reached the maximum iteration count. If yes, proceed to step S88; otherwise, return to step S84. S88. Determine the Pareto optimal solution set.

8. The coordinated optimization method for IGBT peak voltage suppression as described in claim 7, characterized in that, Set the range of the highest junction temperature and the highest surface temperature of the heat sink. Within this range, select the minimum value of the IGBT peak voltage. Based on the minimum value of the IGBT peak voltage, determine the optimal solution for the gate drive resistor and the structural parameters of the busbar.

9. The coordinated optimization method for IGBT peak voltage suppression as described in claim 8, characterized in that, When the maximum surface temperature of the heat sink is 55℃~65℃ and the maximum junction temperature is 74℃~80℃, the minimum peak voltage of the IGBT is 1861V. At this time, the gate drive resistor is 5Ω, the length of the AC busbar is 300mm, and the width of the AC busbar is 200mm.

10. The coordinated optimization method for IGBT peak voltage suppression as described in claim 7, characterized in that, The neural network model has 6 hidden layers, each with 200 neurons, and is trained 20,000 times.

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