Simulation modeling method and system of direct current transformer

Abstract

The application relates to the technical field of transformer simulation, and discloses a simulation modeling method and system of a direct-current transformer. The method discretizes the direct-current transformer into H bridges and transformers, constructs equivalent circuit models of the H bridges and the transformers of the direct-current transformer respectively, connects the equivalent circuit models of the two H bridges through the equivalent circuit model of the transformer, and obtains a circuit simulation model of the direct-current transformer, so that the integrity and output characteristics of the circuit simulation model of the direct-current transformer are ensured, and the stability of the connection between the discrete models is improved.

Description

Technical Field

[0001] This invention relates to the field of transformer simulation technology, and in particular to a simulation modeling method and system for DC transformers. Background Technology

[0002] Currently, with the accelerated urbanization process in large and medium-sized cities, the demand for electricity load is growing rapidly. In cities where transmission corridors are increasingly congested, the trend of end-user loads shifting to DC is evident. The demand for "plug-and-play" distributed power sources and flexible loads on the user side is increasing daily, and the requirements for power quality and supply reliability are becoming increasingly stringent. With the maturity of flexible DC transmission technology, flexible DC distribution networks are playing an increasingly important role. Transformers, as core equipment in the power system, achieve energy isolation and voltage transformation through the principle of electromagnetic induction and have been widely used in all aspects of generation, transmission, distribution, and consumption.

[0003] In power distribution systems, AC transformers are widely used in urban power distribution systems. However, with the upgrading of the energy structure, the loads in traditional power distribution systems have undergone tremendous changes. The proportion of renewable energy, energy storage, and new loads in distribution networks is increasing. These elements, connected to the distribution network on a large scale, often exhibit DC characteristics. Traditional AC-based transformers are encountering more and more problems in the context of large-scale DC element integration, including the stability, efficiency, and reliability of AC grid-connected systems. On the other hand, with the maturity of flexible DC transmission and DC circuit breakers, medium-voltage DC distribution systems have become possible. Therefore, from the application perspective, it is necessary to construct DC-type transformer systems to meet the connection needs of medium-voltage DC distribution systems and low-voltage DC grids. This low-voltage DC grid can adapt to multiple voltage levels according to the needs of different elements. Therefore, multi-voltage-level DC transformers have become key core equipment for flexible DC distribution networks.

[0004] Real-time simulation modeling of DC transformers requires separate modeling of each dual-active-bridge (DAB) converter within the DC transformer, with each DAB requiring independent control. Typically, the model is segmented into individual sub-modules. However, this approach becomes unsuitable when dealing with a large number of DABs, resulting in substantial computational and data processing demands and significant waste of hardware resources. Furthermore, due to the inherent characteristics of the simulation modules—no electrical connection between them, only signal transmission—it's difficult to link the control system to the main circuit, making it challenging to ensure the stability of communication between the various simulation models. Summary of the Invention

[0005] This invention provides a simulation modeling method and system for DC transformers, which solves the technical problem of poor stability of the connection between the simulation models of various parts of a DC transformer.

[0006] In view of this, the first aspect of the present invention provides a simulation modeling method for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, and the two H-bridges are connected through the transformer, comprising the following steps:

[0007] Construct an equivalent circuit model of the H-bridge based on its preset configuration parameters;

[0008] An equivalent circuit model of the transformer is constructed based on the preset configuration parameters of the transformer.

[0009] The equivalent circuit models of the two H-bridges are interconnected through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer.

[0010] Preferably, the H-bridge includes four switching transistors, one power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups, each group comprising two transistors connected in series. The two groups are connected in parallel, and each group is connected in parallel with both the power supply capacitor and the bypass switch. The bypass switch is connected in parallel with the power supply capacitor. The step of constructing the equivalent circuit model of the H-bridge based on its preset configuration parameters specifically includes:

[0011] The main network module connected to the DC transformer obtains the bridge arm current and the status signals of each switch as simulation inputs.

[0012] An equivalent circuit model of the H-bridge is constructed using the electromagnetic transient method. This equivalent circuit model includes a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. Each bypass switch branch includes a current source and an equivalent bypass switch resistor, which are connected in parallel. Each switching transistor branch includes four equivalent switching transistor resistors, which are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two series-connected equivalent switching transistor resistors, and the two groups of equivalent switching transistor branches are connected in parallel. Each power supply capacitor branch includes a historical current source, a parallel capacitor resistor, and a parallel capacitor branch resistor. The historical current source and the parallel capacitor resistor are connected in parallel, and the parallel capacitor branch resistor is connected in parallel with the parallel capacitor resistor.

[0013] Normalizing the power supply capacitance within a preset simulation step size yields:

[0014]

[0015] In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size.

[0016] Transforming Equation 1, we obtain the parallel resistance of the capacitor as follows:

[0017]

[0018] The current value of the historical current source is calculated using the following formula 3.

[0019]

[0020] In Equation 3, I ch The current value of the historical current source, u c The voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor;

[0021] Each switch is equivalent to another switch based on its status signal to determine the resistance value of the equivalent resistance of each switch. The status signal of the switch includes on and off states.

[0022] Based on the equivalent circuit model, the admittance matrix of the node voltage is constructed as follows:

[0023]

[0024] In Equation 4, R K R1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm U represents the input voltage of the H-bridge. p and u n Represent the voltages across the H-bridge, I and I. ch This represents the current value of the historical current source. This represents the current input to the current source;

[0025] The admittance matrix of the node voltage is updated using the simulation input.

[0026] Preferably, the transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch. The step of constructing the equivalent circuit model of the transformer based on its preset configuration parameters specifically includes:

[0027] The current, voltage, resistance, and inductance in the secondary leakage inductance branch are attributed to the primary leakage inductance branch. An equivalent circuit model of the transformer is constructed based on the preset configuration parameters of the transformer. The equivalent circuit model includes: an equivalent primary leakage inductance branch and an equivalent secondary leakage inductance branch.

[0028] The equivalent primary leakage inductance branch includes a primary winding sub-branch, a transformer excitation sub-branch, a secondary winding sub-branch referred to the primary leakage inductance branch, a voltage source referred to the primary leakage inductance branch, and a current source referred to the primary leakage inductance branch; wherein, the primary winding sub-branch includes a primary winding resistor and a primary winding inductance connected in series, the transformer excitation sub-branch includes a transformer excitation resistor and a transformer excitation inductance connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes a secondary winding resistor and a secondary winding inductance referred to the primary leakage inductance branch;

[0029] The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch referred to as the primary leakage inductance sub-branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source referred to as the secondary leakage inductance sub-branch and the current source referred to as the secondary leakage inductance sub-branch.

[0030] The equivalent secondary leakage inductance branch includes a secondary leakage inductance current source and a secondary leakage inductance voltage source, and the current source of the secondary side referred to the primary leakage inductance branch is mutually inductively connected with the secondary leakage inductance current source.

[0031] The voltage source of the secondary side referred to the primary side leakage inductance branch satisfies the following equation 5:

[0032] V2'=n×V2 Equation 5

[0033] In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance.

[0034] The current source of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 6.

[0035] I² = n × I²' Equation 6

[0036] In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch.

[0037] The resistance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 7.

[0038] R2'=n×R2 Equation 7

[0039] In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch.

[0040] The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8.

[0041] L2'=n×L2 Equation 8

[0042] In Equation 8, L2 represents the secondary winding inductance, and L2' represents the secondary winding inductance referred to the primary leakage inductance branch.

[0043] Preferably, the step of connecting the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer specifically includes:

[0044] The equivalent circuit models of the two H-bridges are interconnected through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer. The circuit simulation model of the DC transformer satisfies the following equation (9).

[0045] u sm -V2=nX L ×I2 Equation 9

[0046] In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

[0047] Preferably, the method further includes:

[0048] Multiple circuit simulation models of DC transformers are constructed, and these multiple DC transformer circuit simulation models are cascaded in series.

[0049] Secondly, the present invention also provides a simulation modeling system for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, the two H-bridges being connected through the transformer, and the system includes:

[0050] The H-bridge equivalent construction module is used to construct the equivalent circuit model of the H-bridge according to the preset configuration parameters of the H-bridge.

[0051] A transformer equivalent construction module is used to construct an equivalent circuit model of the transformer based on the preset configuration parameters of the transformer.

[0052] The simulation module is used to connect the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer.

[0053] Preferably, the H-bridge includes four switching transistors, a power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups, each group including two switching transistors connected in series. The two groups are connected in parallel, and each group is connected in parallel with the power supply capacitor and the bypass switch, respectively. The bypass switch is connected in parallel with the power supply capacitor.

[0054] The H-bridge equivalent construction module specifically includes:

[0055] The acquisition module is used to acquire the bridge arm current and the status signals of each switch transistor as simulation input based on the main network module connected to the DC transformer;

[0056] A transient construction module is used to construct an equivalent circuit model of an H-bridge using an electromagnetic transient method. The equivalent circuit model includes: a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. Each bypass switch branch includes an inflow current source and an equivalent bypass switch resistor, which are connected in parallel. Each switching transistor branch includes four equivalent switching transistor resistors, which are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two series-connected equivalent switching transistor resistors, and the two groups of equivalent switching transistor branches are connected in parallel. Each power supply capacitor branch includes a historical current source, a parallel capacitor resistor, and a parallel capacitor branch resistor. The historical current source is connected in parallel with the parallel capacitor resistor, and the parallel capacitor branch resistor is connected in parallel with the parallel capacitor resistor.

[0057] The normalization module is used to normalize the power supply capacitance within a preset simulation step size, resulting in:

[0058]

[0059] In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size.

[0060] The transformation module is used to transform Equation 1 to obtain the capacitor parallel resistance as follows:

[0061]

[0062] The calculation module is used to calculate the current value of the historical current source using the following formula 3.

[0063]

[0064] In Equation 3, I ch The current value of the historical current source, u cThe voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor;

[0065] A switching transistor equivalent module is used to perform equivalent analysis on each switching transistor based on its status signal to determine the resistance value of the equivalent resistance of each switching transistor. The status signal of the switching transistor includes on and off states.

[0066] The admittance module is used to construct the admittance matrix of the node voltage based on the equivalent circuit model.

[0067]

[0068] In Equation 4, R K R1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm Indicates the H-bridge input voltage, u p and u n Representing the voltages across the H-bridge, I ch This represents the current value of the historical current source. This represents the current input to the current source;

[0069] An update module is used to update the admittance matrix of the node voltage using the simulation input.

[0070] Preferably, the transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch, and the transformer equivalent construction module specifically includes:

[0071] The transformer equivalent module is used to transfer the current, voltage, resistance and inductance in the secondary leakage inductance branch to the primary leakage inductance branch, and to construct the equivalent circuit model of the transformer according to the preset configuration parameters of the transformer. The equivalent circuit model includes: equivalent primary leakage inductance branch and equivalent secondary leakage inductance branch.

[0072] The equivalent primary leakage inductance branch includes a primary winding sub-branch, a transformer excitation sub-branch, a secondary winding sub-branch referred to the primary leakage inductance branch, a voltage source referred to the primary leakage inductance branch, and a current source referred to the primary leakage inductance branch; wherein, the primary winding sub-branch includes a primary winding resistor and a primary winding inductance connected in series, the transformer excitation sub-branch includes a transformer excitation resistor and a transformer excitation inductance connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes a secondary winding resistor and a secondary winding inductance referred to the primary leakage inductance branch;

[0073] The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch referred to as the primary leakage inductance sub-branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source referred to as the secondary leakage inductance sub-branch and the current source referred to as the secondary leakage inductance sub-branch.

[0074] The equivalent secondary leakage inductance branch includes a secondary leakage inductance current source and a secondary leakage inductance voltage source, and the current source of the secondary side referred to the primary leakage inductance branch is mutually inductively connected with the secondary leakage inductance current source.

[0075] The voltage source of the secondary side referred to the primary side leakage inductance branch satisfies the following equation 5:

[0076] V2'=n×V2 Equation 5

[0077] In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance.

[0078] The current source of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 6.

[0079] I² = n × I²' Equation 6

[0080] In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch.

[0081] The resistance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 7.

[0082] R2'=n×R2 Equation 7

[0083] In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch.

[0084] The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8.

[0085] L2'=n×L2 Equation 8

[0086] In Equation 8, L2 represents the secondary winding inductance, and LL2' represents the secondary winding inductance referred to the primary leakage inductance branch.

[0087] Preferably, the simulation module is specifically used to connect the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain a circuit simulation model of the DC transformer, wherein the circuit simulation model of the DC transformer satisfies the following equation 9.

[0088] u sm -V2=nX L ×I2 Equation 9

[0089] In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

[0090] Preferably, the system further includes:

[0091] The cascading module is used to construct circuit simulation models of multiple DC transformers, and to cascade the circuit simulation models of multiple DC transformers in series.

[0092] As can be seen from the above technical solutions, the present invention has the following advantages:

[0093] This invention discretizes a DC transformer into an H-bridge and a transformer. By constructing equivalent circuit models of the H-bridge and the transformer respectively, the equivalent circuit models of the two H-bridges are connected through mutual inductance via the equivalent circuit model of the transformer to obtain a circuit simulation model of the DC transformer. This ensures the integrity and output characteristics of the circuit simulation model of the DC transformer and improves the stability of the connection between the discrete models. Attached Figure Description

[0094] Figure 1 This is a schematic diagram of a DC transformer.

[0095] Figure 2 A flowchart illustrating a simulation modeling method for a DC transformer provided in an embodiment of the present invention;

[0096] Figure 3 A schematic diagram of the equivalent circuit model of the H-bridge provided in an embodiment of the present invention;

[0097] Figure 4 A schematic diagram of the equivalent circuit model of a transformer provided in an embodiment of the present invention;

[0098] Figure 5 This is a schematic diagram of a multi-voltage-level DC transformer.

[0099] Figure 6 This is a schematic diagram of the structure of a DC transformer simulation modeling system provided in an embodiment of the present invention. Detailed Implementation

[0100] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0101] The current mainstream core topology of DC transformers adopts, for example, Figure 1 The DAB structure shown is a dual-active-bridge (DAB) converter, which mainly consists of two H-bridges and a high-frequency transformer. The two H-bridges are connected through the transformer. Figure 1 In the middle, V P V S These are the primary and secondary voltages of the transformer, i. L The primary current of the transformer is given; the voltage turns ratio of the high-frequency transformer is n:1, L k For transformer leakage inductance; S 1P S 2P S 3P S 4P For the four switching transistors on the primary side of the transformer, S 1S S 2S S 3S S 4S These are four switching transistors on the secondary side of the transformer, each operating as a PWM signal with a 50% duty cycle. Specifically, the primary side switching transistor S... 1P S 4P and the switching transistor S on the secondary side of the transformer 1S S 4S Simultaneous conduction, with each bridge arm conducting alternately.

[0102] Real-time simulation modeling of DC transformers requires separate modeling of each DAB converter within the DC transformer, and each DAB converter needs independent control. Typically, the model is segmented into individual sub-modules. However, this method becomes problematic when there are many DABs, as the amount of data to be calculated and processed is enormous, leading to significant waste of hardware resources. Furthermore, due to the nature of the simulation modules themselves, there are no electrical connections between them, only signal transmission. This method makes it difficult to link the control system with the main circuit, and it's challenging to guarantee the stability of communication between the various simulation models.

[0103] Therefore, this invention provides a simulation modeling method for DC transformers. For ease of understanding, please refer to [link / reference needed]. Figure 2 This invention provides a simulation modeling method for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, and the two H-bridges are connected through the transformer. The method includes the following steps:

[0104] S1. Construct the equivalent circuit model of the H-bridge based on the preset configuration parameters of the H-bridge.

[0105] S2. Construct the equivalent circuit model of the transformer based on the preset configuration parameters of the transformer.

[0106] S3. Connect the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer.

[0107] This invention provides a simulation modeling method for DC transformers. The DC transformer is discretized into an H-bridge and a transformer. By constructing equivalent circuit models of the H-bridge and the transformer respectively, the equivalent circuit models of the two H-bridges are connected through mutual inductance via the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer. This method ensures the integrity and output characteristics of the circuit simulation model of the DC transformer and improves the stability of the connection between the discrete models.

[0108] The following is a detailed description of a specific embodiment of a simulation modeling method for DC transformers provided by the present invention.

[0109] In one specific embodiment, the H-bridge includes four switching transistors, a power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups of switching transistors. Each group of switching transistors includes two switching transistors connected in series. The two groups of switching transistors are connected in parallel. Each group of switching transistors is connected in parallel with the power supply capacitor and the bypass switch, respectively. The bypass switch is connected in parallel with the power supply capacitor.

[0110] Step S1 specifically includes:

[0111] S101. The main network module connected to the DC transformer obtains the bridge arm current and the status signals of each switch as simulation input.

[0112] It should be noted that the main network module is the control terminal of the DC transformer, used to input control commands to the DC transformer. The main network module runs on the CPU, while the simulation model of the DC transformer runs on the FPGA module.

[0113] S102. Construct the equivalent circuit model of the H-bridge using the electromagnetic transient method, such as... Figure 3 As shown, the equivalent circuit model includes a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. The bypass switch branch includes a current source. Equivalent resistance R of bypass switch K Flowing into the current source Equivalent resistance R of bypass switch K The circuit is connected in parallel. The switching transistor branch includes four equivalent resistors R1, R2, R3, and R4. These four equivalent resistors are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two equivalent switching transistor resistors connected in series. The two groups of equivalent switching transistor branches are connected in parallel. The power supply capacitor branch includes the historical current source I. ch , capacitor in parallel with resistor Rc The resistor R is connected in parallel with the capacitor branch, and the historical current source I... ch Resistor R in parallel with capacitor c Parallel connection, the parallel resistor R of the capacitor branch and the parallel resistor R of the capacitor c Parallel connection;

[0114] It is understandable that the power supply capacitor uses the Norton equivalent, meaning the equivalent circuit is the historical current source I. ch , capacitor in parallel with resistor R c The resistor R is connected in parallel with the capacitor branch, and the historical current source I... ch Resistor R in parallel with capacitor c Parallel connection, the parallel resistor R of the capacitor branch and the parallel resistor R of the capacitor c Parallel connection, with a parallel resistor R in the capacitor branch, can more accurately characterize the capacitor's intrinsic resistance. Using Norton's equivalent based on trapezoidal integral substitution, to maintain the mean admittance of the capacitor within a simulation step of Δt, the power supply capacitor within a preset simulation step is normalized, resulting in:

[0115]

[0116] In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size.

[0117] Transforming Equation 1, we obtain the parallel resistance of the capacitor as follows:

[0118]

[0119] The current value of the historical current source is calculated using the following formula 3.

[0120]

[0121] In Equation 3, I ch The current value of the historical current source, u c The voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor;

[0122] It should be noted that in the equivalent circuit, the vector sum of the node currents must be zero, i.e., the current value I of the historical current source must be zero. ch Capacitor in parallel with resistor (flowing through equivalent resistance) R c The current, the current i flowing through the capacitor c The sum is zero.

[0123] S103. Perform equivalent analysis on each switching transistor based on its status signal to determine the equivalent resistance value of each switching transistor. The status signal of the switching transistor includes on and off states.

[0124] In this example, the switching transistors are equivalent to the turn-on and turn-off method, and the four switching transistors S in the H-bridge are... 1P S 2P S 3P S 4P These are equivalent to resistors R1, R2, R3, and R4 that can be turned on or off, respectively. That is, when the IGBT or diode is on, the resistance of this branch is close to zero; when the IGBT or diode is off, the resistance of this branch is close to infinity. The switching state depends on the voltage and current of the switching transistor branch, as well as the externally input switching signal.

[0125]

[0126] In the formula, R on This is the on-resistance, which is typically very small, for example, 0.001Ω, R. off The shut-off resistor is typically very large, such as 100MΩ.

[0127] It is understandable that since the output voltage of the H-bridge depends on the capacitance of the input voltage, and the effect of the switching transistor on the output voltage depends on the control command, in practical applications, the effect of the switching transistor on the output voltage of the H-bridge is relatively small. In order to simplify the model, the conduction state of the switching transistor is equivalent to a resistor, and the power supply capacitor is equivalent to the Norton equivalent method. This simplifies the operating characteristics of the switching transistor and accurately simulates the port output characteristics of the H-bridge.

[0128] S104. Based on the equivalent circuit model, construct the admittance matrix of the node voltage as follows:

[0129]

[0130] In Equation 4, R K R1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm Indicates the H-bridge input voltage, u p and u n Representing the voltages across the H-bridge, I ch This represents the current value of the historical current source. This represents the current input to the current source;

[0131] S105. Update the admittance matrix of the node voltage using the simulation input.

[0132] In one specific embodiment, the transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch.

[0133] Step S2 specifically includes:

[0134] The current, voltage, resistance, and inductance in the secondary leakage inductance branch are attributed to the primary leakage inductance branch. An equivalent circuit model of the transformer is constructed based on the transformer's preset configuration parameters, such as... Figure 4 As shown, the equivalent circuit model includes: the equivalent primary leakage inductance branch and the equivalent secondary leakage inductance branch;

[0135] The equivalent primary leakage inductance branch includes the primary winding sub-branch, the transformer excitation sub-branch, the secondary winding sub-branch referred to the primary leakage inductance branch, the voltage source V2' referred to the primary leakage inductance branch, and the current source I2' referred to the primary leakage inductance branch; wherein, the primary winding sub-branch includes the primary winding resistor R1 and the primary winding inductance L1 connected in series, the transformer excitation sub-branch includes the transformer excitation resistor Rm and the transformer excitation inductance Lm connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes the secondary winding resistor R2' referred to the primary leakage inductance branch and the secondary winding inductance L2' referred to the primary leakage inductance branch;

[0136] The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch that is referred to as the primary leakage inductance branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source V2' and the current source I2' that are referred to as the primary leakage inductance branch.

[0137] The equivalent secondary leakage inductance branch includes the secondary leakage inductance current source I2 and the secondary leakage inductance voltage source V2. The secondary leakage inductance current source I2', which is referred to as the primary leakage inductance branch, is mutually inductively connected with the secondary leakage inductance current source I2.

[0138] Understandably, since the voltages at both ends of the transformer are inconsistent, it is necessary to reduce the voltage on the primary or secondary side. That is, the equivalent model reduces the voltage on the secondary side to the primary side, which is equivalent to a controlled voltage source. The impedance on the secondary side is reduced to the primary side according to the square of the turns ratio, forming an equivalent circuit model with a controlled voltage source on the primary side and a controlled current source on the secondary side.

[0139] In order to reduce the secondary voltage to the primary side as an equivalent controlled voltage source, the voltage source of the leakage inductance branch of the secondary side reduced to the primary side satisfies the following equation 5.

[0140] V2'=n×V2 Equation 5

[0141] In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance.

[0142] In order to reduce the secondary current to an equivalent current source, the current source of the leakage inductance branch of the primary side reduced from the secondary side satisfies the following equation 6.

[0143] I² = n × I²' Equation 6

[0144] In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch.

[0145] To simplify the FPGA model in the simulation, the resonant inductance in DAB and the primary leakage inductance of the transformer are calculated together. Considering the transformer impedance, the resistance of the secondary side referred to the primary leakage inductance branch satisfies the following equation 7.

[0146] R2'=n×R2 Equation 7

[0147] In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch.

[0148] The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8.

[0149] L2'=n×L2 Equation 8

[0150] In Equation 8, L2 represents the secondary winding inductance, and L2' represents the secondary winding inductance referred to the primary leakage inductance branch.

[0151] In one specific embodiment, step S3 specifically includes:

[0152] The equivalent circuit models of the two H-bridges are interconnected through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer. The circuit simulation model of the DC transformer satisfies the following equation (9).

[0153] u sm -V2=nX L ×I2 Equation 9

[0154] In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

[0155] Understandably, since the input voltage and output voltage of a DC transformer are not equal, the circuit simulation model of the DC transformer needs to satisfy Equation 9 in order to accurately characterize the output characteristics.

[0156] In one specific embodiment, existing multi-voltage level DC transformers generally employ, as shown below: Figure 5 The illustrated topology connects multiple DAB converters in series at the high-voltage side to the HV DC bus and in parallel at the low-voltage side to the LV DC bus, thereby increasing the high-voltage side voltage level by n times and the low-voltage side current level by many times. The high-frequency transformer provides electrical isolation and voltage matching for the circuit, while the inductor serves as a transient energy storage element. By controlling the square wave voltage on the AC output side of the full-bridge converter, the magnitude and phase of the voltage applied across the auxiliary inductor can be controlled, thereby controlling the power magnitude and flow. Therefore, to achieve simulation modeling of multi-voltage-level DC transformers, this embodiment further includes:

[0157] S4. Construct circuit simulation models of multiple DC transformers and cascade them in series.

[0158] The above is a detailed description of an embodiment of a simulation modeling method for a DC transformer provided by the present invention. The following is a detailed description of an embodiment of a simulation modeling system for a DC transformer provided by the present invention.

[0159] This invention provides a simulation modeling system for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, and the two H-bridges are connected through the transformer. (See also...) Figure 6 Its system includes:

[0160] H-bridge equivalent construction module 100 is used to construct the equivalent circuit model of H-bridge according to the preset configuration parameters of H-bridge;

[0161] The transformer equivalent construction module 200 is used to construct the equivalent circuit model of the transformer based on the preset configuration parameters of the transformer.

[0162] Simulation module 300 is used to connect the equivalent circuit models of two H-bridges through the equivalent circuit model of a transformer to obtain a circuit simulation model of a DC transformer.

[0163] In one specific embodiment, the H-bridge includes four switching transistors, a power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups of switching transistors. Each group of switching transistors includes two switching transistors connected in series. The two groups of switching transistors are connected in parallel. Each group of switching transistors is connected in parallel with the power supply capacitor and the bypass switch, respectively. The bypass switch is connected in parallel with the power supply capacitor.

[0164] The H-bridge equivalent construction module specifically includes:

[0165] The acquisition module is used to acquire the bridge arm current and the status signals of each switch transistor based on the main network module connected to the DC transformer as simulation inputs;

[0166] The transient construction module is used to construct the equivalent circuit model of the H-bridge using the electromagnetic transient method. The equivalent circuit model includes: a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. The bypass switch branch includes an inflow current source and an equivalent resistor of the bypass switch, which are connected in parallel. The switching transistor branch includes four equivalent resistors of the switching transistors, which are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two equivalent switching transistor resistors connected in series. The two groups of equivalent switching transistor branches are connected in parallel. The power supply capacitor branch includes a historical current source, a parallel capacitor resistor, and a parallel capacitor branch resistor. The historical current source and the parallel capacitor resistor are connected in parallel, and the parallel capacitor branch resistor is connected in parallel with the parallel capacitor resistor.

[0167] The normalization module is used to normalize the power supply capacitance within a preset simulation step size, resulting in:

[0168]

[0169] In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size.

[0170] The transformation module is used to transform Equation 1 to obtain the capacitor parallel resistance as follows:

[0171]

[0172] The calculation module is used to calculate the current value of the historical current source using the following formula 3.

[0173]

[0174] In Equation 3, I ch The current value of the historical current source, u c The voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor;

[0175] The switching transistor equivalent module is used to perform equivalent analysis on each switching transistor based on its status signal to determine the equivalent resistance value of each switching transistor. The status signal of the switching transistor includes on and off states.

[0176] The admittance module is used to construct the admittance matrix of the node voltages based on the equivalent circuit model.

[0177]

[0178] In Equation 4, R KR1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm U represents the input voltage of the H-bridge. p and u n Represent the voltages across the H-bridge, I and I. ch This represents the current value of the historical current source. This represents the current input to the current source;

[0179] The update module is used to update the admittance matrix of the node voltage using simulation inputs.

[0180] In one specific embodiment, the transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch. The transformer equivalent construction module specifically includes:

[0181] The transformer equivalent module is used to reduce the current, voltage, resistance and inductance in the secondary leakage inductance branch to the primary leakage inductance branch. It constructs the equivalent circuit model of the transformer based on the preset configuration parameters of the transformer. The equivalent circuit model includes: equivalent primary leakage inductance branch and equivalent secondary leakage inductance branch.

[0182] The equivalent primary leakage inductance branch includes the primary winding sub-branch, the transformer excitation sub-branch, the secondary winding sub-branch referred to the primary leakage inductance branch, the voltage source referred to the primary leakage inductance branch, and the current source referred to the primary leakage inductance branch. Among them, the primary winding sub-branch includes the primary winding resistance and the primary winding inductance connected in series, the transformer excitation sub-branch includes the transformer excitation resistance and the transformer excitation inductance connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes the secondary winding resistance and the secondary winding inductance referred to the primary leakage inductance branch.

[0183] The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch that is referred to as the primary leakage inductance branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source and the current source of the secondary winding referred to as the primary leakage inductance branch, respectively.

[0184] The equivalent secondary leakage inductance branch includes a secondary leakage inductance current source and a secondary leakage inductance voltage source. The current source of the secondary side referred to the primary leakage inductance branch is mutually inducted with the secondary leakage inductance current source.

[0185] Among them, the voltage source of the secondary side referred to the primary side leakage inductance branch satisfies the following equation 5.

[0186] V2'=n×V2 Equation 5

[0187] In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance.

[0188] The current source of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 6.

[0189] I² = n × I²' Equation 6

[0190] In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch.

[0191] The resistance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 7.

[0192] R2'=n×R2 Equation 7

[0193] In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch.

[0194] The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8.

[0195] L2'=n×L2 Equation 8

[0196] In Equation 8, L2 represents the secondary winding inductance, and L2' represents the secondary winding inductance referred to the primary leakage inductance branch.

[0197] In one specific embodiment, the simulation module is specifically used to connect the equivalent circuit models of two H-bridges through the equivalent circuit model of a transformer to obtain a circuit simulation model of a DC transformer, wherein the circuit simulation model of the DC transformer satisfies the following equation 9.

[0198] u sm -V2=nX L ×I2 Equation 9

[0199] In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

[0200] In one specific embodiment, the system further includes:

[0201] The cascade module is used to construct circuit simulation models of multiple DC transformers, and to cascade multiple DC transformer circuit simulation models in series.

[0202] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0203] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0204] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0205] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0206] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation modeling method for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, the two H-bridges being connected through the transformer, characterized in that, Includes the following steps: Construct an equivalent circuit model of the H-bridge based on its preset configuration parameters; The H-bridge includes four switching transistors, one power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups, each group consisting of two transistors connected in series. The two groups are connected in parallel, and each group is connected in parallel with both the power supply capacitor and the bypass switch. The bypass switch is connected in parallel with the power supply capacitor. The step of constructing the equivalent circuit model of the H-bridge based on its preset configuration parameters specifically includes: The main network module connected to the DC transformer obtains the bridge arm current and the status signals of each switch as simulation inputs. An equivalent circuit model of the H-bridge is constructed using the electromagnetic transient method. This equivalent circuit model includes a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. Each bypass switch branch includes a current source and an equivalent bypass switch resistor, which are connected in parallel. Each switching transistor branch includes four equivalent switching transistor resistors, which are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two series-connected equivalent switching transistor resistors, and the two groups of equivalent switching transistor branches are connected in parallel. Each power supply capacitor branch includes a historical current source, a parallel capacitor resistor, and a parallel capacitor branch resistor. The historical current source and the parallel capacitor resistor are connected in parallel, and the parallel capacitor branch resistor is connected in parallel with the parallel capacitor resistor. Normalizing the power supply capacitance within a preset simulation step size yields: In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size. Transforming Equation 1, we obtain the parallel resistance of the capacitor as follows: The current value of the historical current source is calculated using the following formula 3. In Equation 3, I ch The current value of the historical current source, u c The voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor; Each switch is equivalent to another switch based on its status signal to determine the resistance value of the equivalent resistance of each switch. The status signal of the switch includes on and off states. Based on the equivalent circuit model, the admittance matrix of the node voltage is constructed as follows: In Equation 4, R K R1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm Indicates the H-bridge input voltage, u p and u n Represent the voltages across the H-bridge, I and I. ch This represents the current value of the historical current source. This represents the current input to the current source; The admittance matrix of the node voltage is updated using the simulation input. An equivalent circuit model of the transformer is constructed based on the preset configuration parameters of the transformer. The equivalent circuit models of the two H-bridges are interconnected through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer.

2. The simulation modeling method for DC transformers according to claim 1, characterized in that, The transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch. The step of constructing the equivalent circuit model of the transformer based on the preset configuration parameters of the transformer specifically includes: The current, voltage, resistance, and inductance in the secondary leakage inductance branch are attributed to the primary leakage inductance branch. An equivalent circuit model of the transformer is constructed based on the preset configuration parameters of the transformer. The equivalent circuit model includes: an equivalent primary leakage inductance branch and an equivalent secondary leakage inductance branch. The equivalent primary leakage inductance branch includes a primary winding sub-branch, a transformer excitation sub-branch, a secondary winding sub-branch referred to the primary leakage inductance branch, a voltage source referred to the primary leakage inductance branch, and a current source referred to the primary leakage inductance branch; wherein, the primary winding sub-branch includes a primary winding resistor and a primary winding inductance connected in series, the transformer excitation sub-branch includes a transformer excitation resistor and a transformer excitation inductance connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes a secondary winding resistor and a secondary winding inductance referred to the primary leakage inductance branch; The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch referred to as the primary leakage inductance sub-branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source referred to as the secondary leakage inductance sub-branch and the current source referred to as the secondary leakage inductance sub-branch. The equivalent secondary leakage inductance branch includes a secondary leakage inductance current source and a secondary leakage inductance voltage source, and the current source of the secondary side referred to the primary leakage inductance branch is mutually inductively connected with the secondary leakage inductance current source. The voltage source of the secondary side referred to the primary side leakage inductance branch satisfies the following equation 5: V2'=n×V2 Equation 5 In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance. The current source of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 6. I² = n × I²' Equation 6 In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch. The resistance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 7. R2'=n×R2 Equation 7 In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch. The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8. L2'=n×L2 Equation 8 In Equation 8, L2 represents the secondary winding inductance, and L2' represents the secondary winding inductance referred to the primary leakage inductance branch.

3. The simulation modeling method for DC transformers according to claim 2, characterized in that, The step of connecting the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer specifically includes: The equivalent circuit models of the two H-bridges are interconnected through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer. The circuit simulation model of the DC transformer satisfies the following equation (9). u sm -V2=nX L ×I2 Equation 9 In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

4. The simulation modeling method for DC transformers according to claim 1, characterized in that, Also includes: Multiple circuit simulation models of DC transformers are constructed, and these multiple DC transformer circuit simulation models are cascaded in series.

5. A simulation modeling system for a DC transformer, wherein the DC transformer includes two H-bridges and a transformer, the two H-bridges being connected through the transformer, characterized in that, Its system includes: The H-bridge equivalent construction module is used to construct the equivalent circuit model of the H-bridge according to the preset configuration parameters of the H-bridge. The H-bridge includes four switching transistors, one power supply capacitor, and a bypass switch. The four switching transistors are divided into two groups, each group including two switching transistors connected in series. The two groups are connected in parallel, and each group is connected in parallel with the power supply capacitor and the bypass switch, respectively. The bypass switch is connected in parallel with the power supply capacitor. The H-bridge equivalent construction module specifically includes: The acquisition module is used to acquire the bridge arm current and the status signals of each switch transistor as simulation input based on the main network module connected to the DC transformer; A transient construction module is used to construct an equivalent circuit model of an H-bridge using an electromagnetic transient method. The equivalent circuit model includes: a bypass switch branch, a switching transistor branch, and a power supply capacitor branch. The bypass switch branch, the switching transistor branch, and the power supply capacitor branch are connected in parallel. Each bypass switch branch includes an inflow current source and an equivalent bypass switch resistor, which are connected in parallel. Each switching transistor branch includes four equivalent switching transistor resistors, which are divided into two groups of equivalent switching transistor branches. Each group of equivalent switching transistor branches includes two series-connected equivalent switching transistor resistors, and the two groups of equivalent switching transistor branches are connected in parallel. Each power supply capacitor branch includes a historical current source, a parallel capacitor resistor, and a parallel capacitor branch resistor. The historical current source is connected in parallel with the parallel capacitor resistor, and the parallel capacitor branch resistor is connected in parallel with the parallel capacitor resistor. The normalization module is used to normalize the power supply capacitance within a preset simulation step size, resulting in: In Equation 1, R c Δt represents the parallel resistance of the capacitor, C represents the power supply capacitor, and Δt represents the simulation step size. The transformation module is used to transform Equation 1 to obtain the capacitor parallel resistance as follows: The calculation module is used to calculate the current value of the historical current source using the following formula 3. In Equation 3, I ch The current value of the historical current source, u c The voltage across the power supply capacitor is represented by t, which represents the current simulation step size, and i is the current voltage across the capacitor. c This represents the current flowing through the power supply capacitor; A switching transistor equivalent module is used to perform equivalent analysis on each switching transistor based on its status signal to determine the resistance value of the equivalent resistance of each switching transistor. The status signal of the switching transistor includes on and off states. The admittance module is used to construct the admittance matrix of the node voltage based on the equivalent circuit model. In Equation 4, R K R1, R2, R3, and R4 represent the equivalent resistance of the bypass switch, R represents the equivalent resistance of the switching transistor, and u represents the parallel resistance of the capacitor branch. sm Indicates the H-bridge input voltage, u p and u n Represent the voltages across the H-bridge, I and I. ch This represents the current value of the historical current source. This represents the current input to the current source; The update module is used to update the admittance matrix of the node voltage using the simulation input. A transformer equivalent construction module is used to construct an equivalent circuit model of the transformer based on the preset configuration parameters of the transformer. The simulation module is used to connect the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain the circuit simulation model of the DC transformer.

6. The simulation modeling system for DC transformers according to claim 5, characterized in that, The transformer includes a primary leakage inductance branch, a secondary leakage inductance branch, and a mutual inductance branch. The transformer equivalent construction module specifically includes: The transformer equivalent module is used to transfer the current, voltage, resistance and inductance in the secondary leakage inductance branch to the primary leakage inductance branch, and to construct the equivalent circuit model of the transformer according to the preset configuration parameters of the transformer. The equivalent circuit model includes: equivalent primary leakage inductance branch and equivalent secondary leakage inductance branch. The equivalent primary leakage inductance branch includes a primary winding sub-branch, a transformer excitation sub-branch, a secondary winding sub-branch referred to the primary leakage inductance branch, a voltage source referred to the primary leakage inductance branch, and a current source referred to the primary leakage inductance branch; wherein, the primary winding sub-branch includes a primary winding resistor and a primary winding inductance connected in series, the transformer excitation sub-branch includes a transformer excitation resistor and a transformer excitation inductance connected in series, and the secondary winding sub-branch referred to the primary leakage inductance branch includes a secondary winding resistor and a secondary winding inductance referred to the primary leakage inductance branch; The primary winding sub-branch, the transformer excitation sub-branch, and the secondary winding sub-branch referred to as the primary leakage inductance sub-branch are connected and converge at one point. The transformer excitation sub-branch is connected in parallel with the voltage source referred to as the secondary leakage inductance sub-branch and the current source referred to as the secondary leakage inductance sub-branch. The equivalent secondary leakage inductance branch includes a secondary leakage inductance current source and a secondary leakage inductance voltage source, and the current source of the secondary side referred to the primary leakage inductance branch is mutually inductively connected with the secondary leakage inductance current source. The voltage source of the secondary side referred to the primary side leakage inductance branch satisfies the following equation 5: V2'=n×V2 Equation 5 In Equation 5, n represents the transformer mutual inductance ratio, V2' represents the voltage value of the voltage source of the secondary side referred to the primary side leakage inductance branch, and V2 represents the voltage value of the voltage source of the secondary side leakage inductance. The current source of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 6. I² = n × I²' Equation 6 In Equation 6, I2 represents the secondary leakage inductance current, and I2' represents the current of the current source in the secondary side referred to the primary leakage inductance branch. The resistance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 7. R2'=n×R2 Equation 7 In Equation 7, R2 represents the secondary winding resistance, and R2' represents the secondary winding resistance referred to the primary leakage inductance branch. The inductance of the leakage inductance branch from the secondary side to the primary side satisfies the following equation 8. L2'=n×L2 Equation 8 In Equation 8, L2 represents the secondary winding inductance, and L2' represents the secondary winding inductance referred to the primary leakage inductance branch.

7. The simulation modeling system for DC transformers according to claim 6, characterized in that, The simulation module is specifically used to connect the equivalent circuit models of the two H-bridges through the equivalent circuit model of the transformer to obtain a circuit simulation model of the DC transformer, wherein the circuit simulation model of the DC transformer satisfies the following equation 9. u sm -V2=nX L ×I2 Equation 9 In Equation 9, X L This represents the inductance value of the mutual inductance connection between the H-bridge and the transformer.

8. The simulation modeling system for DC transformers according to claim 5, characterized in that, Also includes: The cascading module is used to construct circuit simulation models of multiple DC transformers, and to cascade the circuit simulation models of multiple DC transformers in series.

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