A soft-switching analysis method and system for three-phase interleaved independent bus LLC

Abstract

This invention discloses a soft-switching analysis method and system for three-phase interleaved independent bus LLC topologies. The method includes: obtaining an equivalent circuit based on the operating state of the three-phase interleaved independent bus LLC; obtaining a first and a second relationship equation between the two levels of the stepped voltage and the excitation current using Kirchhoff's voltage law; obtaining the ratio relationship between the two levels of the stepped voltage based on the first and second relationship equations; obtaining the excitation current change rate equation based on the inductance matrix of the five-limb three-phase integrated transformer and the ratio relationship; calculating the peak-to-peak value of the excitation current using the excitation current change rate equation; and obtaining the soft-switching implementation conditions based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor. This invention can provide a reference for parameter selection in three-phase interleaved independent bus LLC topologies.

Description

Technical Field

[0001] This invention belongs to the field of three-phase interleaved LLC topology analysis technology, and particularly relates to a soft-switching analysis method and system for three-phase interleaved independent bus LLC. Background Technology

[0002] On-board chargers (OBCs), a key component in the development of the new energy vehicle industry, typically consist of a two-stage structure: a power factor correction (PFC) rectifier and an LLC converter. In this structure, the totem-pole PFC configuration has three independent output buses. While traditional Y-type LLC converters can operate using these three independent bus voltages, a constant voltage difference must be maintained between the independent DC buses. Otherwise, additional current will be generated between the different voltage sources each cycle through the resonant capacitor. The voltage difference between the output buses of the totem-pole PFC rectifier is a low-frequency square wave voltage, making traditional Y-type LLC converters unsuitable for this application scenario.

[0003] Existing analysis methods for Y-type LLC converters are not applicable to three-phase interleaved independent bus LLC topologies because they fail to adequately consider the influence of the zero-sequence current component. Furthermore, traditional analysis methods cannot provide effective guidance for parameter selection in three-phase interleaved LLC topologies, leading to a degree of uncertainty in the design process and a lack of precise theoretical support. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a soft-switching analysis method and system for three-phase interleaved independent bus LLC, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a soft-switching analysis method for three-phase interleaved independent bus LLC, comprising:

[0006] Based on the operating state of the three-phase interleaved independent bus LLC, the equivalent circuit is obtained. Considering the coupling between two phases, and through Kirchhoff's voltage law, the first and second relationship equations between the two levels of the stepped voltage and the excitation current are obtained.

[0007] Based on the first relational equation and the second relational equation, the ratio relationship between the two levels of the stepped voltage is obtained;

[0008] Based on the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, the excitation current change rate equation is obtained, and the peak-to-peak value of the excitation current is calculated through the excitation current change rate equation.

[0009] Based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor, the conditions for achieving soft switching are obtained.

[0010] Preferably, the first and second relationship equations between the two levels of the stepped voltage and the excitation current include:

[0011] Define the excitation current of two adjacent phases, and use Kirchhoff's voltage law and the coupling relationship between each pair of phase windings to obtain the first voltage equation and the second voltage equation.

[0012] Based on the first voltage equation and the resonant inductor, the first relationship equation between the first level of the stepped voltage and the excitation current is obtained;

[0013] Based on the second voltage equation and the resonant inductor, the second relationship equation between the second level of the stepped voltage and the excitation current is obtained.

[0014] Preferably, obtaining the ratio relationship between the two levels of the stepped voltage includes:

[0015] By combining the first and second relational equations and introducing a coupling coefficient, a simplified ratio relationship between the two levels of the stepped voltage is obtained.

[0016] Preferably, the inductance matrix of the five-limb three-phase integrated transformer is as follows:

[0017]

[0018] Among them, i3 is the same as i2, which is the excitation current of the winding with a step voltage of u2. The difference between i2 and i3 is that they are in different phases. This is the inductance matrix of a five-column three-phase integrated transformer.

[0019] The equation for the rate of change of the excitation current is:

[0020]

[0021] Where u1 and u2 are the two levels of the stepped voltage, i1 is the magnetizing current of the winding with stepped voltage u1, and i2 is the magnetizing current of the winding with stepped voltage u2. m is the primary excitation inductance, and k is the coupling coefficient between each pair of phase windings.

[0022] Preferably, the expression for the peak-to-peak value of the excitation current is:

[0023]

[0024] Where, Δi m T is the peak-to-peak value of the excitation current. s The switching cycle.

[0025] Secondly, this invention also discloses a soft-switching analysis system for three-phase interleaved independent bus LLC, comprising:

[0026] The first calculation module is used to obtain the equivalent circuit based on the working state of the three-phase interleaved independent bus LLC, consider the coupling between two phases, and obtain the first and second relationship equations between the two levels of the stepped voltage and the excitation current through Kirchhoff's voltage law.

[0027] The second calculation module is used to obtain the ratio relationship between the two levels of the stepped voltage based on the first relational equation and the second relational equation.

[0028] The third calculation module is used to obtain the excitation current change rate equation based on the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, and to calculate the peak-to-peak value of the excitation current through the excitation current change rate equation.

[0029] The analysis module is used to obtain the soft-switching implementation conditions based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor.

[0030] Thirdly, the present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in the first aspect.

[0031] Fourthly, the present invention also discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0032] Fifthly, the present invention also discloses a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described in the first aspect.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] This invention provides a soft-switching analysis method for three-phase interleaved independent bus LLC converters. First, an accurate equivalent circuit model is constructed for the operating state of the three-phase interleaved independent bus LLC converter. This model can reflect the electrical characteristics of the converter under different operating conditions.

[0035] Secondly, considering the coupling between the two phases, Kirchhoff's voltage law (KVL) is used to obtain the first and second relationship equations between the two levels of the stepped voltage and the excitation current in the equivalent circuit. These equations describe how the excitation current responds to voltage changes at different voltage levels.

[0036] Next, using the first and second relational equations, the ratio between the two levels of the stepped voltage is derived. This ratio helps to simplify circuit analysis and provides a basis for subsequent calculations.

[0037] Furthermore, by combining the inductance matrix and ratio relationships of a five-limb three-phase integrated transformer, the excitation current change rate equation is derived. This equation accurately describes the change of excitation current over time and is key to analyzing soft-switching conditions. This invention calculates the peak-to-peak value of the excitation current using the excitation current change rate equation. This peak-to-peak value is an important parameter for achieving soft switching because it affects the turn-on and turn-off behavior of the switching transistor.

[0038] Finally, based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor, the conditions for achieving soft switching are determined. These conditions include the maximum value of the excitation current, the dead time, the parasitic capacitance of the switching transistor, the transformer turns ratio, and the primary input voltage. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0040] Figure 1 This is a three-phase interleaved independent bus LLC topology diagram according to an embodiment of the present invention;

[0041] Figure 2 This is an equivalent circuit diagram under a certain stable mode of an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of a five-limb three-phase transformer according to an embodiment of the present invention;

[0043] Figure 4 This is a waveform diagram of the stepped voltage and excitation current of a certain phase in an embodiment of the present invention;

[0044] Figure 5 This is a waveform diagram of the resonant tank current in an embodiment of the present invention. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0047] The technical terms used in the following embodiments will be explained first.

[0048] (1) Three-phase Interleaved Independent Bus LLC is a DC-DC converter mainly used in high voltage DC transmission systems.

[0049] A three-phase interleaved independent bus LLC is a resonant circuit that achieves a constant output voltage by controlling the switching frequency. Unlike traditional PWM (Pulse Width Modulation) converters, LLC controls the output voltage through frequency regulation and has the following characteristics:

[0050] Zero-voltage turn-on (ZVS): Before conduction, the voltage of the switching transistor drops to zero, achieving zero-voltage turn-on and thus reducing conduction losses.

[0051] Zero-current turn-off (ZCS): During turn-off, the current of the switching transistor drops to zero, achieving zero-current turn-off and reducing turn-off losses.

[0052] The basic structure of a three-phase interleaved independent bus LLC includes:

[0053] Switching circuit: A full-bridge inverter circuit composed of switching devices.

[0054] Resonant circuit: includes resonant inductor, resonant capacitor and magnetizing inductor, and is connected to the primary side of transformer.

[0055] Transformer secondary side: A full-wave uncontrolled rectifier circuit composed of diodes, connected to the load after being connected to the output capacitor.

[0056] Three-phase interleaved independent bus LLC performs exceptionally well in high-power applications, especially in high-voltage direct current transmission systems, offering the following advantages:

[0057] High efficiency: Through soft-switching technologies (ZVS and ZCS), switching losses are significantly reduced, and overall efficiency is improved.

[0058] Large capacity: Suitable for applications requiring high power.

[0059] Small size: Compared to traditional converters, it has a smaller size and weight.

[0060] Bidirectional transmission: Supports bidirectional power transmission, suitable for applications requiring bidirectional power supply.

[0061] (2) The five-column three-phase integrated transformer is a special transformer design. Its core feature is that the iron core consists of five columns, three of which are equipped with coils to form a three-phase winding, while the other two columns are used as a magnetic circuit. This design allows the zero-sequence magnetic flux to form a flow loop through the two outer iron core columns and the upper and lower iron jaws, thereby reducing the zero-sequence impedance.

[0062] The core structure of a five-limb three-phase integrated transformer consists of five limbs. The coils are mounted on the three middle limbs, forming the three-phase windings, while the two outer limbs serve as the magnetic circuit. This design allows the transformer to have lower impedance when handling zero-sequence current, making it suitable for applications requiring low zero-sequence impedance.

[0063] Due to its advantages in handling zero-sequence current, the five-limb three-phase integrated transformer is typically used in applications requiring low zero-sequence impedance, such as laboratories and power systems with special requirements. Furthermore, this type of transformer can reduce zero-sequence losses, although its manufacturing cost is higher.

[0064] advantage:

[0065] Low zero-sequence impedance: The zero-sequence magnetic flux can flow effectively through the flow loop formed by the two outer iron core columns and the upper and lower iron jaws, thus reducing the zero-sequence impedance.

[0066] Wide range of applications: Suitable for applications requiring low zero-sequence impedance, such as laboratories and power systems with special requirements.

[0067] Reduced losses: Using this type of transformer in a power system can reduce zero-sequence losses.

[0068] (3) The characteristics of a switching transistor mainly include its function as a voltage-controlled switch, its saturation conduction and cutoff characteristics, and its dynamic characteristics. Ideally, a switching transistor is considered a simple switch; as long as the gate voltage is sufficient, switching operation can be guaranteed. Switching transistors have limitations on maximum operating voltage and maximum operating current; these two parameters are crucial for the selection and safety of the switching transistor.

[0069] Dynamic characteristics specifically include:

[0070] Turn-on time: The switching transistor can switch from the open state to the closed state in almost no time, and can be completed instantly.

[0071] Turn-off time: The switching transistor can also switch from the closed state to the open state instantly.

[0072] The saturation conduction and cutoff characteristics are as follows:

[0073] When a switching transistor is saturated and conducting, it has good conductivity; when it is cut off, its conductivity is poor, making it suitable for use as an electronic switch.

[0074] Switching transistors are widely used in power management, motor drives, and signal switching and amplification. In power management, switching transistors regulate output voltage and current by controlling switching time and frequency to achieve stable power output; in motor drives, switching transistors can control the speed and direction of the motor; in communication equipment and digital circuits, switching transistors are often used for signal switching and amplification.

[0075] (4) The main conditions for soft switching include the following aspects:

[0076] Closing speed: The successful application of soft switches is closely related to their closing speed, which is usually required to be below 20ms. If the closing speed is too slow, the arc duration will be too long, which will exacerbate the wear and tear on the equipment.

[0077] Current magnitude: Soft switches have high precision in controlling current and voltage, but it is essential to ensure that the current magnitude does not exceed the current limit that the soft switch can withstand in order to avoid device damage or failure.

[0078] Transient overvoltages: Transient overvoltages are common in soft-switching applications, such as those caused by lightning strikes, line switching, and short circuits. To ensure the stable operation of soft switches, it is necessary to assess and analyze transient overvoltages and implement appropriate protective measures.

[0079] Frequency range: The application range of soft switching depends on the frequency of the circuit it controls, and it is generally used in the range of 20KHz to 100KHz.

[0080] Temperature and humidity environment: The operating environment of soft switches also affects their performance and lifespan, especially when there are large changes in temperature and humidity, soft switches need to be protected and maintained.

[0081] Soft-switching technology is the opposite of traditional hard-switching technology. In hard-switching technology, voltage and current occur simultaneously during the turn-on and turn-off processes of switching elements (such as transistors and MOSFETs), leading to significant switching losses and electromagnetic interference. Soft-switching technology, by introducing resonant circuits and buffer circuits, allows the voltage of the switching element to drop to zero before turn-on (zero-voltage turn-on, ZVS) or the current to drop to zero before turn-off (zero-current turn-off, ZCS), thereby significantly reducing switching losses and electromagnetic interference.

[0082] This embodiment provides a soft-switching analysis method for three-phase interleaved independent bus LLC, including:

[0083] S1. Based on the working state of the three-phase interleaved independent bus LLC, the equivalent circuit is obtained. Considering the coupling between two phases, and through Kirchhoff's voltage law, the first and second relationship equations between the two levels of the stepped voltage and the excitation current are obtained.

[0084] Specifically, the three-phase interleaved independent bus LLC topology diagram is as follows: Figure 1 As shown. Figure 1 In the middle, the left side is the primary input of the transformer. The input bus is a three-phase interleaved independent bus. N1 and N2 are the number of turns on the primary side and the number of turns on the secondary side of the transformer, respectively, and the transformation ratio is 10:12.

[0085] The equivalent circuit diagram under a certain stable mode is as follows: Figure 2 As shown. Figure 2 The equivalent circuit diagram for turning on switching transistors S5, S8, and S10. Figure 2 In this context, k represents the coupling coefficient between any two phases, and its range is (-0.5, 0). Figure 2 Each phase step voltage is labeled.

[0086] Furthermore, the first and second relationship equations between the two levels of the stepped voltage and the excitation current are obtained, including:

[0087] Define the excitation current of two adjacent phases, and use Kirchhoff's voltage law and the coupling relationship between each pair of phase windings to obtain the first voltage equation and the second voltage equation.

[0088] Based on the first voltage equation and the resonant inductor, the first relationship equation between the first level of the stepped voltage and the excitation current is obtained;

[0089] Based on the second voltage equation and the resonant inductor, the second relationship equation between the second level of the stepped voltage and the excitation current is obtained.

[0090] Specifically, the equation relating the two voltage levels of the stepped voltage and the current under the stable conduction mode is as follows:

[0091]

[0092] Where V is the input voltage of the preceding stage, u1 and u2 are the two levels of the stepped voltage, i1 is the magnetizing current of the winding with stepped voltage u1, i2 is the magnetizing current of the winding with stepped voltage u2, and L m For the primary magnetizing inductance, L r The primary resonant inductance is given by S, where k is the coupling coefficient between each pair of phase windings, and S is the coupling coefficient between each pair of phase windings. A S is the area of ​​the magnetic post containing the winding. B Let be the area of ​​the edge magnetic column.

[0093] S2. Based on the first relational equation and the second relational equation, the ratio relationship between the two levels of the stepped voltage is obtained;

[0094] Furthermore, the ratio relationship between the two levels of the stepped voltage is obtained as follows:

[0095] By combining the first and second relational equations and introducing a coupling coefficient, a simplified ratio relationship between the two levels of the stepped voltage is obtained.

[0096] Specifically, the expression for the ratio of the two levels of the stepped voltage is:

[0097]

[0098] Here, r is the ratio of u1 to u2, which is a reference value. The value of r ranges from [1,2], where r=1 represents the case where the side magnetic pillar is large enough, and r=2 represents the case where there is no side magnetic pillar.

[0099] S3. Based on the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, the excitation current change rate equation is obtained, and the peak-to-peak value of the excitation current is calculated through the excitation current change rate equation.

[0100] Specifically, a schematic diagram of a five-limb three-phase transformer is shown below. Figure 3 As shown.

[0101] Furthermore, the equation for calculating the rate of change of excitation current using the inductance matrix of a five-limb three-phase integrated transformer is as follows:

[0102]

[0103] Among them, i3 is the same as i2, which is the excitation current of the winding with a step voltage of u2. The difference between i2 and i3 is that they are in different phases. This is the inductance matrix of a five-column three-phase integrated transformer.

[0104] Furthermore, the expression for the rate of change of excitation current is:

[0105]

[0106] Furthermore, the expression for the peak-to-peak value of the excitation current is:

[0107]

[0108] Where, Δi m T is the peak-to-peak value of the excitation current. s The switching cycle.

[0109] S4. Based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor, the soft-switching implementation conditions are obtained.

[0110] Furthermore, the conditions for implementing soft switching are:

[0111] i max ·T d ≥2(C iss +N 2 C oss )·V dc (6)

[0112] in, T is the maximum value of the excitation current. d For the time of death, C iss C is the parasitic capacitance of the primary-side switching transistor. oss For the parasitic capacitance of the secondary-side switching transistor, the turns ratio of the N transformer, V dc This is the primary input voltage.

[0113] Figure 4 This is a waveform diagram of the stepped voltage and excitation current of a certain phase provided in this embodiment. Figure 4 In the figure, the green curve is the stepped voltage waveform and the blue curve is the excitation current waveform. The slope of the excitation current corresponds to the stepped voltage, and the corresponding relationship can be expressed by formula (4).

[0114] Figure 5 The waveform diagram of the resonant tank current provided in this embodiment is shown. Figure 5 In the diagram, the red, blue, and green curves represent the current waveforms of the abc three-phase resonant tank, respectively, indicating that the three-phase currents operate symmetrically and stably.

[0115] Beneficial effects of this embodiment:

[0116] This embodiment provides a soft-switching analysis method for three-phase interleaved independent bus LLC. Under stable conduction mode, the relationship between the stepped voltage and the corresponding excitation current is obtained according to Kirchhoff's voltage law. At the same time, the ratio of the two levels of the stepped voltage is obtained. The peak-to-peak value of the excitation current is calculated based on the inductance matrix of the five-limb three-phase integrated transformer. The soft-switching implementation conditions are given by the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor. This method is different from the analysis method of traditional Y-type LLC topology and has a good guiding role in the selection of parameters for three-phase interleaved LLC topology.

[0117] Compared with existing design processes, this embodiment innovatively considers the coupling between two phases and derives the excitation current through stepped voltage. This technical solution can solve the problem of zero-sequence current components in the front stage of a three-phase interleaved independent bus LLC topology. Unlike the analysis method of traditional Y-type LLC topology, it can help with the parameter selection of a three-phase interleaved independent bus LLC topology.

[0118] This embodiment proposes for the first time a soft-switching analysis method for three-phase interleaved independent bus LLC, and provides the implementation conditions for soft switching of three-phase interleaved independent bus LLC, which can provide a reference for the parameter selection of three-phase interleaved independent bus LLC topology.

[0119] The relationship between the stepped voltage and the corresponding excitation current, the relationship between the two levels of the stepped voltage, and the method of calculating the peak-to-peak value of the excitation current using the inductance matrix of a five-column three-phase integrated transformer analyzed in this embodiment can simplify the calculation process and expression, and assist in the selection of parameters for the three-phase interleaved independent bus LLC.

[0120] Example 2

[0121] Based on the same inventive concept, this embodiment also provides a soft-switching analysis system for three-phase interleaved independent bus LLC, including:

[0122] The first calculation module is used to obtain the equivalent circuit based on the working state of the three-phase interleaved independent bus LLC, consider the coupling between two phases, and obtain the first and second relationship equations between the two levels of the stepped voltage and the excitation current through Kirchhoff's voltage law.

[0123] The second calculation module is used to obtain the ratio relationship between the two levels of the stepped voltage based on the first relational equation and the second relational equation.

[0124] The third calculation module is used to obtain the excitation current change rate equation based on the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, and to calculate the peak-to-peak value of the excitation current through the excitation current change rate equation.

[0125] The analysis module is used to obtain the soft-switching implementation conditions based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor.

[0126] The soft-switching analysis system for three-phase interleaved independent bus LLC provided in this embodiment has all the advantages of the soft-switching analysis system for three-phase interleaved independent bus LLC provided in Embodiment 1.

[0127] Example 3

[0128] This embodiment also discloses a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in Embodiment 1.

[0129] Example 4

[0130] This embodiment also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0131] Example 5

[0132] This embodiment also discloses a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0133] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A soft switching analysis method for three-phase interleaved independent bus LLC, characterized in that, Includes the following steps: Based on the topology of a three-phase interleaved independent bus LLC, a five-limb three-phase integrated transformer is installed between the primary resonant circuit and the secondary rectifier circuit in the topology. Based on the inductance matrix of the five-column three-phase integrated transformer, the excitation current change rate equation is obtained, and the peak-to-peak value of the excitation current is calculated using the excitation current change rate equation. The equation for calculating the rate of change of excitation current using the inductance matrix of a five-limb three-phase integrated transformer is as follows: ； in, For primary magnetizing inductance, The step voltage is The excitation current of the winding, The step voltage is The excitation current of the winding, and The same, for step voltages. The excitation current of the winding, , The difference lies in the phase they are in; The inductance matrix of a five-column three-phase integrated transformer; ； in, This represents the area of ​​the magnetic post containing the winding. Let be the area of ​​the edge magnetic column. This represents the coupling coefficient between each pair of phase windings; The equation for the rate of change of the excitation current is: ； in, , These are the two levels of the stepped voltage; The expression for the peak-to-peak value of the excitation current is: ； in, This represents the peak-to-peak value of the excitation current. For switching cycles; Based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor, the soft-switching implementation conditions are obtained; The conditions for soft switching are: ； in, , is the maximum value of the excitation current. Dead time, This is the parasitic capacitance of the primary-side switching transistor. For the parasitic capacitance of the secondary-side switching transistor, Transformer turns ratio This is the primary input voltage.

2. A soft-switching analysis system for three-phase interleaved independent bus LLC, characterized in that, include: A structural module for installing a five-column three-phase integrated transformer between the primary resonant circuit and the secondary rectifier circuit in a topology based on a three-phase interleaved independent bus LLC. The calculation module is used to obtain the excitation current change rate equation based on the inductance matrix of the five-column three-phase integrated transformer, and to calculate the peak-to-peak value of the excitation current through the excitation current change rate equation. The equation for calculating the rate of change of excitation current using the inductance matrix of a five-limb three-phase integrated transformer is as follows: ； in, For primary magnetizing inductance, The step voltage is The excitation current of the winding, The step voltage is The excitation current of the winding, and The same, for step voltages. The excitation current of the winding, , The difference lies in the phase they are in; The inductance matrix of a five-column three-phase integrated transformer; ； in, This represents the area of ​​the magnetic post containing the winding. Let be the area of ​​the edge magnetic column. This represents the coupling coefficient between each pair of phase windings; The equation for the rate of change of the excitation current is: ； in, , These are the two levels of the stepped voltage; The expression for the peak-to-peak value of the excitation current is: ； in, This represents the peak-to-peak value of the excitation current. For switching cycles; The analysis module is used to obtain the soft-switching implementation conditions based on the peak-to-peak value of the excitation current and the equivalent output capacitance of the switching transistor. The conditions for soft switching are: ； in, , is the maximum value of the excitation current. Dead time, This is the parasitic capacitance of the primary-side switching transistor. For the parasitic capacitance of the secondary-side switching transistor, Transformer turns ratio This is the primary input voltage.

3. A computer device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of claim 1.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 1.

5. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 1.

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