Soft switching analysis method and system for three-phase staggered independent bus LLC

Abstract

The invention discloses a soft switching analysis method and system for a three-phase interlaced independent bus LLC, and the method comprises the steps: obtaining an equivalent circuit according to the working state of the three-phase interlaced independent bus LLC, and obtaining a first relation equation and a second relation equation between two levels of step voltage and excitation current through a Kirchhoff voltage law; according to the first relation equation and the second relation equation, the ratio relation between the two levels of the step voltage is obtained; according to an inductance matrix of the five-column type three-phase integrated transformer and the ratio relation, an excitation current change rate equation is obtained, and an excitation current peak-to-peak value is calculated through the excitation current change rate equation; and obtaining a soft switching implementation condition according to the excitation current peak-to-peak value and the equivalent output capacitance of the switching tube. According to the method, reference can be provided for parameter selection of the three-phase staggered independent bus LLC topology.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-phase staggered LLC topology analysis, and in particular relates to a soft switch analysis method and system for a three-phase staggered independent bus LLC. Background Art

[0002] As a key component in the development of the new energy vehicle industry, the on-board charger (OBC) usually includes a two-stage structure of a power factor correction (PFC) rectifier and an LLC converter. In this structure, the totem pole PFC structure has three independent output buses. Although the traditional Y-type LLC converter can operate using these three independent bus voltages, it requires that a constant voltage difference must be maintained between the independent DC buses. Otherwise, additional current will be formed between different voltage sources through the resonant capacitor in each cycle. The voltage difference between the buses output by the totem pole PFC rectifier is a low-frequency square wave voltage, which makes the traditional Y-type LLC converter unsuitable for this application scenario.

[0003] Existing Y-type LLC converter analysis methods are not applicable to three-phase interleaved independent bus LLC topology because they fail to fully consider the impact of zero-sequence current components. In addition, traditional analysis methods cannot provide effective guidance for parameter selection of three-phase interleaved LLC topology, resulting in a certain degree of blindness in the design process and a lack of precise theoretical support. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a soft switching analysis method and system for a three-phase staggered independent bus LLC to solve the above problems in the prior art.

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

[0006] According to the working state of the three-phase staggered independent bus LLC, the equivalent circuit is obtained, the coupling between the two phases is considered, and the first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current are obtained through Kirchhoff's voltage law;

[0007] According to the first relationship equation and the second relationship equation, a ratio relationship between two levels of the step voltage is obtained;

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

[0009] According to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube, the soft switching realization condition is obtained.

[0010] Preferably, obtaining the first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current includes:

[0011] The excitation currents of two adjacent phases are defined, and the first voltage equation and the second voltage equation are obtained by using Kirchhoff's voltage law and the coupling relationship between each two-phase winding;

[0012] According to the first voltage equation and the resonant inductance, a first relationship equation between the first level of the step voltage and the excitation current is obtained;

[0013] According to the second voltage equation and the resonant inductance, a second relationship equation between the second level of the step voltage and the excitation current is obtained.

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

[0015] The first relationship equation and the second relationship equation are processed jointly, and a coupling coefficient is introduced to obtain a simplified ratio relationship between two levels of the step voltage.

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

[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; It is the inductance matrix of a five-column three-phase integrated transformer.

[0019] The excitation current change rate equation is:

[0020]

[0021] Among them, u1 and u2 are two levels of the step voltage, i1 is the excitation current of the winding with the step voltage u1, i2 is the excitation current of the winding with the step voltage u2, L m is the primary excitation inductance, and k is the coupling coefficient between each two-phase winding.

[0022] Preferably, the peak-to-peak value of the excitation current is expressed as:

[0023]

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

[0025] In a second aspect, the present invention further discloses a soft switch analysis system for a three-phase staggered independent bus LLC, comprising:

[0026] The first calculation module is used to obtain an equivalent circuit according to the working state of the three-phase staggered independent bus LLC, consider the coupling between the two phases, and obtain a first relationship equation and a second relationship equation between the two levels of the step voltage and the excitation current through Kirchhoff's voltage law;

[0027] A second calculation module, used for obtaining a ratio relationship between two levels of a step voltage according to the first relationship equation and the second relationship equation;

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

[0029] The analysis module is used to obtain the soft switching realization conditions according to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube.

[0030] In a third aspect, the present invention further discloses a computer device, comprising 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] In a fourth aspect, the present invention further discloses a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method described in the first aspect when executed by a processor.

[0032] In a fifth aspect, the present invention further discloses a computer program product, including a computer program, which implements the steps of the method described in the first aspect when executed by a processor.

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

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

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

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

[0037] Furthermore, the excitation current change rate equation is derived by combining the inductance matrix and ratio relationship of the five-column three-phase integrated transformer. This equation can accurately describe the change of the excitation current over time and is the key to analyzing the soft switching conditions. The present invention calculates the peak-to-peak value of the excitation current through the excitation current change rate equation. This peak-to-peak value is an important parameter for realizing soft switching because it affects the on and off behavior of the switch tube.

[0038] Finally, according to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube, the conditions for soft switching are determined. These conditions include the maximum value of the excitation current, dead time, parasitic capacitance of the switch tube, transformer ratio and primary input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0040] Figure 1 A three-phase staggered independent bus LLC topology diagram of an embodiment of the present invention;

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

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

[0043] Figure 4 A waveform diagram of a phase step voltage and excitation current in an embodiment of the present invention;

[0044] Figure 5 4 is a waveform diagram of the resonant tank current according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

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

[0047] First, the technical terms involved in the following embodiments are explained.

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

[0049] The 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 by frequency regulation and has the following characteristics:

[0050] Zero Voltage Switching (ZVS): Before turning on, the voltage of the switch tube drops to zero, achieving zero voltage switching, thereby reducing conduction losses.

[0051] Zero Current Shutdown (ZCS): When shutting down, the current of the switch tube drops to zero, achieving zero current shutdown and reducing shutdown losses.

[0052] The basic structure of three-phase staggered 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 excitation inductor, and is connected to the primary side of the transformer.

[0055] Secondary side of the transformer: A full-wave uncontrolled rectifier circuit composed of diodes, connected to the output capacitor and then connected to the load.

[0056] Three-phase interleaved independent bus LLC performs well in high power applications, especially in HVDC transmission systems, with the following advantages:

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

[0058] Large capacity: suitable for application scenarios with high power requirements.

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

[0060] Bidirectional transmission: supports bidirectional power transmission, suitable for occasions requiring bidirectional power supply.

[0061] (2) The five-column three-phase integrated transformer is a special transformer design. Its core feature is that the 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 magnetic circuits. This design allows the zero-sequence magnetic flux to form a circulation loop with the upper and lower iron jaws through the two outer core columns, thereby reducing the zero-sequence impedance.

[0062] The core structure of the five-column three-phase integrated transformer includes five columns. The coils are installed on the three middle columns to form a three-phase winding, and the two side columns serve as magnetic circuits. This design enables the transformer to have lower impedance when processing zero-sequence current, and is suitable for occasions that require low zero-sequence impedance.

[0063] Due to the advantages of the five-column three-phase integrated transformer in handling zero-sequence current, it is often used in occasions requiring low zero-sequence impedance, such as laboratories and power systems with special requirements. In addition, this transformer can also reduce zero-sequence losses, although its manufacturing cost is higher.

[0064] advantage:

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

[0066] Widely used: Suitable for occasions requiring low zero-sequence impedance, such as laboratories and power systems with special requirements.

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

[0068] (3) The characteristics of the switch tube mainly include its voltage-controlled switch, saturation conduction and cutoff characteristics, dynamic characteristics, etc. Ideally, the switch tube is regarded as a simple switch. As long as the gate voltage is sufficient, the switch action can be guaranteed. The switch tube has the maximum operating voltage and maximum operating current limitations. These two parameters are crucial to the selection and safety of the switch tube.

[0069] Dynamic characteristics include:

[0070] Turn-on time: It takes almost no time for the switch tube to switch from the open state to the closed state, and it can be completed instantly.

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

[0072] The saturation conduction and cutoff characteristics are:

[0073] When the switch tube is in saturation conduction, it has good conductivity; when it is cut off, the conductivity is poor, and it is suitable for use as an electronic switch.

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

[0075] (4) The main conditions for achieving 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 will last too long, which will increase the loss of the equipment.

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

[0078] Transient overvoltage: Transient overvoltage usually exists in the application scenarios of soft switches, such as lightning strikes, line switching, short circuits, etc. In order to ensure the stable application of soft switches, it is necessary to evaluate and analyze transient overvoltage and take appropriate protection measures.

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

[0080] Temperature and humidity environment: The operating environment of the soft switch will also affect its performance and life, especially when the temperature and humidity change greatly, the soft switch needs to be protected and maintained.

[0081] Soft-Switching Technology is relative to the traditional hard-switching technology. In hard-switching technology, voltage and current will appear simultaneously during the on and off process of switching elements (such as transistors, MOSFET, etc.), resulting in large switching losses and electromagnetic interference. Soft-switching technology, by introducing resonance, snubber circuits and other means, makes the voltage of the switching element drop to zero before turning on (zero voltage turn-on ZVS) or the current drop to zero before turning off (zero current turn-off ZCS), thereby significantly reducing switching losses and electromagnetic interference.

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

[0083] S1. According to the working state of the three-phase staggered independent bus LLC, an equivalent circuit is obtained, the coupling between the two phases is considered, and the first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current are obtained through Kirchhoff's voltage law;

[0084] Specifically, the three-phase staggered independent bus LLC topology diagram is as follows: Figure 1 shown. Figure 1 In the figure, the left side is the primary input of the transformer, the input bus is a three-phase staggered independent bus, N1 and N2 are the primary and secondary turns 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 It is the equivalent circuit diagram of the switch tubes S5, S8 and S10 being turned on. Figure 2 Where k represents the coupling coefficient between each two phases, and its range is (-0.5, 0). Figure 2 The step voltage of each phase is marked.

[0086] Furthermore, the first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current include:

[0087] The excitation currents of two adjacent phases are defined, and the first voltage equation and the second voltage equation are obtained by using Kirchhoff's voltage law and the coupling relationship between each two-phase winding;

[0088] According to the first voltage equation and the resonant inductance, a first relationship equation between the first level of the step voltage and the excitation current is obtained;

[0089] According to the second voltage equation and the resonant inductance, a second relationship equation between the second level of the step voltage and the excitation current is obtained.

[0090] Specifically, the relationship equation between the two levels of the step voltage and the current in the stable conduction mode is:

[0091]

[0092] Where V is the previous input voltage, u1 and u2 are the two levels of the step voltage, i1 is the excitation current of the winding with the step voltage u1, i2 is the excitation current of the winding with the step voltage u2, L m is the primary magnetizing inductance, L r is the primary resonant inductance, k is the coupling coefficient between each two-phase winding, S A is the area of ​​the magnetic column where the winding is located, S B is the area of ​​the side magnetic column.

[0093] S2. Obtaining a ratio relationship between two levels of step voltage according to the first relationship equation and the second relationship equation;

[0094] Furthermore, the ratio relationship between the two levels of the step voltage is obtained including:

[0095] The first relationship equation and the second relationship equation are processed jointly, and a coupling coefficient is introduced to obtain a simplified ratio relationship between two levels of the step voltage.

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

[0097]

[0098] Among them, r is the ratio of u1 to u2, which is a reference quantity. The range of r is [1,2], r = 1 means the side magnetic column is large enough, and r = 2 means there is no side magnetic column.

[0099] S3, according to the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, obtain the excitation current change rate equation, and calculate the excitation current peak-to-peak value through the excitation current change rate equation;

[0100] Specifically, the schematic diagram of a five-column three-phase transformer is as follows: Figure 3 shown.

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

[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; It is the inductance matrix of a five-column three-phase integrated transformer.

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

[0105]

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

[0107]

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

[0109] S4. According to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube, a soft switching realization condition is obtained.

[0110] Furthermore, the soft switching realization conditions are:

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

[0112] in, is the maximum value of the excitation current, T d For the dead time, C iss is the parasitic capacitance of the primary switch tube, C oss is the parasitic capacitance of the secondary switch tube, N is the transformer ratio, V dc is the primary input voltage.

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

[0114] Figure 5 This is a waveform diagram of the resonant tank current provided in this embodiment. Figure 5 In the figure, the red, blue and green curves represent the abc three-phase resonant slot current waveforms respectively, and the three-phase current runs symmetrically and stably.

[0115] Beneficial effects of this embodiment:

[0116] This embodiment provides a soft switching analysis method for a three-phase staggered independent bus LLC. In a stable conduction mode, the relationship between the step voltage and the corresponding excitation current is obtained according to Kirchhoff's voltage law, and the ratio relationship between the two levels of the step voltage is obtained. The peak-to-peak value of the excitation current is calculated according to the inductance matrix of the five-column three-phase integrated transformer, and the soft switching realization conditions are given by the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube. This method is different from the analysis method of the traditional Y-type LLC topology, and has a good guiding role in the parameter selection of the three-phase staggered LLC topology.

[0117] Compared with the existing design process, this embodiment innovatively considers the coupling between the two phases and derives the excitation current through the step voltage. This technical solution can solve the problem of zero-sequence current component in the front stage of the three-phase staggered independent bus LLC topology. It is different from the analysis method of the traditional Y-type LLC topology and can help select parameters for the three-phase staggered independent bus LLC topology.

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

[0119] The relationship between the step voltage and the corresponding excitation current, the relationship between the two levels of the step 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 method, and assist in the parameter selection of the three-phase staggered independent bus LLC.

[0120] Embodiment 2

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

[0122] The first calculation module is used to obtain an equivalent circuit according to the working state of the three-phase staggered independent bus LLC, consider the coupling between the two phases, and obtain a first relationship equation and a second relationship equation between the two levels of the step voltage and the excitation current through Kirchhoff's voltage law;

[0123] A second calculation module, used for obtaining a ratio relationship between two levels of a step voltage according to the first relationship equation and the second relationship equation;

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

[0125] The analysis module is used to obtain the soft switching realization conditions according to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube.

[0126] The soft switch analysis system for three-phase staggered independent bus LLC provided in this embodiment has all the advantages of the soft switch analysis system for three-phase staggered independent bus LLC provided in the first embodiment.

[0127] Embodiment 3

[0128] This embodiment further 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 embodiment.

[0129] Embodiment 4

[0130] This embodiment further discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in the first embodiment are implemented.

[0131] Embodiment 5

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

[0133] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A soft switching analysis method for three-phase staggered independent bus LLC, characterized in that: The following steps are involved: According to the working state of the three-phase staggered independent bus LLC, the equivalent circuit is obtained, the coupling between the two phases is considered, and the first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current are obtained through Kirchhoff's voltage law; According to the first relationship equation and the second relationship equation, a ratio relationship between two levels of the step voltage is obtained; According to the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, an excitation current change rate equation is obtained, and the excitation current peak-to-peak value is calculated through the excitation current change rate equation; According to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube, the soft switching realization condition is obtained.

2. The method according to claim 1, characterized in that The first relationship equation and the second relationship equation between the two levels of the step voltage and the excitation current are obtained, including: The excitation currents of two adjacent phases are defined, and the first voltage equation and the second voltage equation are obtained by using Kirchhoff's voltage law and the coupling relationship between each two-phase winding; According to the first voltage equation and the resonant inductance, a first relationship equation between the first level of the step voltage and the excitation current is obtained; According to the second voltage equation and the resonant inductance, a second relationship equation between the second level of the step voltage and the excitation current is obtained.

3. The method according to claim 1, characterized in that The ratio relationship between the two levels of the step voltage includes: The first relationship equation and the second relationship equation are processed jointly, and a coupling coefficient is introduced to obtain a simplified ratio relationship between two levels of the step voltage.

4. The method according to claim 1, characterized in that: The inductance matrix of the five-column three-phase integrated transformer is: 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; It is the inductance matrix of a five-column three-phase integrated transformer. The excitation current change rate equation is: Among them, u1 and u2 are two levels of the step voltage, i1 is the excitation current of the winding with the step voltage u1, i2 is the excitation current of the winding with the step voltage u2, L m is the primary excitation inductance, and k is the coupling coefficient between each two-phase winding.

5. The method according to claim 1, characterized in that The expression of the peak-to-peak value of the excitation current is: Among them, Δi m is the peak-to-peak value of the excitation current, T s is the switching cycle.

6. A soft switch analysis system for three-phase staggered independent bus LLC, characterized in that: include: The first calculation module is used to obtain an equivalent circuit according to the working state of the three-phase staggered independent bus LLC, consider the coupling between the two phases, and obtain a first relationship equation and a second relationship equation between the two levels of the step voltage and the excitation current through Kirchhoff's voltage law; A second calculation module, used for obtaining a ratio relationship between two levels of a step voltage according to the first relationship equation and the second relationship equation; A third calculation module is used to obtain an excitation current change rate equation according to the inductance matrix of the five-column three-phase integrated transformer and the ratio relationship, and calculate the excitation current peak-to-peak value through the excitation current change rate equation; The analysis module is used to obtain the soft switching realization conditions according to the peak-to-peak value of the excitation current and the equivalent output capacitance of the switch tube.

7. 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 claims 1-5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to claims 1 to 5 are implemented.

9. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to claims 1 to 5 are implemented.

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