A simulation method and system of a dual active bridge converter

Abstract

The application provides a simulation method and system of a dual active bridge converter, comprising calculating system admittance matrices of all switching states according to circuit parameters and saving the system admittance matrices respectively according to switching state numbers; checking switching change conditions, selecting a matrix corresponding to a current switching state from the saved system admittance matrices; calculating a historical current source according to circuit information of a last time step; solving new node voltages according to system node voltage equations, and then solving branch voltages and branch currents until simulation ends. The application saves system admittance matrices of all switching states by precalculation and according to switching state numbers. In a simulation iteration process, after switching states change, only the switching states are used as index numbers to directly index new system admittance matrices, so that the expense of recalculating system admittance matrices is avoided. Since the working frequency of the DAB is high and the switching states change frequently, the method of the application can effectively improve simulation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power system simulation technology, specifically relating to a simulation method and system for a dual active bridge converter. Background Technology

[0002] The dual active bridge DC-DC converter (DAB) is a commonly used basic structure in power electronic systems. It can achieve flexible DC-DC conversion and, through appropriate combinations, can also form more complex and functional devices such as DC transformers and electric vehicle charging piles.

[0003] In recent years, with the development of medium and low voltage DC distribution networks, the application of dual active bridge converters has become increasingly widespread. In order to fully study the control characteristics of DC distribution networks, it is often necessary to perform electromagnetic transient simulations of the system.

[0004] However, power electronic circuits composed of dual active bridge converters are characterized by tight electrical coupling and high nonlinearity. If the traditional method of combining discrete component models to construct the system model is used, the simulation efficiency decreases sharply with the increase of the number of power electronic switches. Summary of the Invention

[0005] In view of this, the present invention aims to solve the problem that when performing electromagnetic transient simulation of a system containing dual active bridge converters, the simulation efficiency decreases sharply with the increase of the number of power electronic switches when using the traditional method of combining separate component models to construct the system model.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a simulation method for a dual active bridge converter, comprising the following steps:

[0008] Calculate the system admittance matrix for all switching states based on the circuit parameters, and save them separately according to the switching state number;

[0009] Check the switch changes and select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix;

[0010] Calculate the historical current source based on the circuit information from the previous time step;

[0011] The new node voltages are obtained by solving the system node voltage equations.

[0012] Solve for the branch voltage and branch current;

[0013] Determine if the simulation has ended. If not, increase the time step by one step, re-check the switch changes, and execute subsequent steps until the simulation ends.

[0014] Furthermore, the equivalent circuit of the dual active bridge converter is calculated, and the circuit parameters are obtained based on the equivalent circuit. The circuit parameters include the switching equivalent parameters, and the calculation formula for the switching equivalent parameters is as follows:

[0015]

[0016]

[0017] In the formula, R on R is the on-resistance of the switch. off , where is the switch-off resistor, g is the switch signal, and n1 / n2 is the transformer turns ratio.

[0018] Furthermore, circuit parameters also include equivalent capacitance parameters, the formula for which is as follows:

[0019]

[0020]

[0021] In the formula, C1 and C2 are capacitance values, V C1 (t-dt), V' C2 (t-dt) is the voltage of the capacitor branch in the previous time step.

[0022] Furthermore, circuit parameters also include inductance equivalent parameters, the formula for calculating inductance equivalent parameters is as follows:

[0023]

[0024]

[0025]

[0026] Among them, L1, L2, L m L k I is the inductance value. L1 (t-dt), I Lm (t-dt), I' L2 (t-dt) represents the current in the inductor branch of the previous time step.

[0027] Furthermore, the system node voltage equations are as follows:

[0028] GV = I

[0029] In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

[0030] Secondly, the present invention provides a simulation system for a dual active bridge converter, comprising:

[0031] The pre-calculation unit is used to calculate the system admittance matrix for all switching states based on the circuit parameters and save them separately according to the switching state number.

[0032] The index unit is used to check the switch change and select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix.

[0033] The simulation calculation unit is used to calculate the historical current source based on the circuit information of the previous time step; it is also used to solve the new node voltage based on the system node voltage equation; it is also used to solve the branch voltage and branch current; it is also used to determine whether the simulation has ended. If not, it adds one time step and re-checks the switching changes and executes the subsequent steps until the simulation ends.

[0034] Furthermore, the equivalent circuit of the dual active bridge converter is calculated, and the circuit parameters are obtained based on the equivalent circuit. The circuit parameters include the switching equivalent parameters, and the calculation formula for the switching equivalent parameters is as follows:

[0035]

[0036]

[0037] In the formula, R on R is the on-resistance of the switch. off , where is the switch-off resistor, g is the switch signal, and n1 / n2 is the transformer turns ratio.

[0038] Furthermore, circuit parameters also include equivalent capacitance parameters, the formula for which is as follows:

[0039]

[0040]

[0041] In the formula, C1 and C2 are capacitance values, V C1 (t-dt), V' C2 (t-dt) is the voltage of the capacitor branch in the previous time step.

[0042] Furthermore, circuit parameters also include inductance equivalent parameters, the formula for calculating inductance equivalent parameters is as follows:

[0043]

[0044]

[0045]

[0046] Among them, L1, L2, L m L k I is the inductance value. L1 (t-dt), I Lm (t-dt), I' L2 (t-dt) represents the current in the inductor branch of the previous time step.

[0047] Furthermore, the system node voltage equations are as follows:

[0048] GV = I

[0049] In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

[0050] In summary, this invention provides a simulation method and system for a dual active bridge converter (DAB). The method includes calculating the system admittance matrix for all switching states based on circuit parameters and saving it according to the switching state number; checking switching changes and selecting the system admittance matrix corresponding to the current switching state from the saved system admittance matrices; calculating historical current sources based on the circuit information of the previous time step; solving for new node voltages based on the system node voltage equations; solving for branch voltages and branch currents; determining whether the simulation is complete; if not, increasing the time step and re-checking the switching changes before executing subsequent steps until the simulation ends. This invention pre-calculates the system admittance matrix for all switching states and saves it according to the switching state number. During simulation iteration, after a switching state change, only the switching state needs to be used as an index to directly obtain the new system admittance matrix, avoiding the overhead of recalculating the system admittance matrix. Since the DAB operates at a high frequency and switching states change frequently, this method can effectively improve simulation efficiency. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 A flowchart illustrating a simulation method for a dual active bridge converter provided in an embodiment of the present invention;

[0053] Figure 2 The circuit structure diagram of the dual active bridge converter provided in the embodiment of the present invention;

[0054] Figure 3This is an equivalent circuit diagram of a dual active bridge converter provided in an embodiment of the present invention;

[0055] Figure 4 A simulation calculation flowchart provided for an embodiment of the present invention. Detailed Implementation

[0056] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] The dual active bridge DC-DC converter (DAB) is a commonly used basic structure in power electronic systems. It can achieve flexible DC-DC conversion and, through appropriate combinations, can also form more complex and functional devices such as DC transformers and electric vehicle charging piles. Figure 2 A detailed circuit diagram of a DAB module is provided. It includes eight IGBTs and their anti-parallel diodes, and a high-frequency transformer.

[0058] In recent years, with the development of medium and low voltage DC distribution networks, the application of dual active bridge converters has become increasingly widespread. In order to fully study the control characteristics of DC distribution networks, it is often necessary to perform electromagnetic transient simulations of the system.

[0059] However, power electronic circuits composed of dual active bridge converters are characterized by tight electrical coupling and high nonlinearity. If the traditional method of combining discrete component models to construct the system model is used, the simulation efficiency decreases sharply with the increase of the number of power electronic switches.

[0060] Based on this, the present invention provides a simulation method and system for a dual active bridge converter.

[0061] The following is a detailed description of an embodiment of the simulation method for a dual active bridge converter according to the present invention.

[0062] Please see Figure 1 This embodiment provides a simulation method for a dual active bridge converter, specifically including:

[0063] S100: Calculate the system admittance matrix for all switching states based on the circuit parameters, and save them separately according to the switch state numbers. This circuit has 8 switches. Arranging the switch states sequentially by number yields a binary number (g). 11 g12 g 13 g 14 g 21 g 22 g 23 g 24 The value of this number ranges from 0 to 255, so there are a total of 256 system admittance matrices stored in memory.

[0064] like Figure 3 As shown, the secondary side parameters of the transformer are converted to the primary side, and the equivalent circuit is calculated.

[0065] contrast Figure 2 and Figure 3 It can be seen that the inductor and capacitor branches are equivalent to the parallel branches of the resistor and the historical current source, and the switch branch is equivalent to the resistor branch. Figure 3 There are 7 nodes and 13 branches in total.

[0066] Based on this equivalent circuit, various circuit parameters, including the equivalent parameters of the switches, capacitors, and inductors, can be obtained. The formulas for calculating each circuit parameter are as follows:

[0067] Formula for calculating the equivalent parameters of a switch:

[0068]

[0069]

[0070] Among them, R on R is the on-resistance of the switch. off , where is the switch-off resistor, g is the switch signal, and n1 / n2 is the transformer turns ratio.

[0071] Formula for calculating equivalent capacitance parameters:

[0072]

[0073]

[0074] Where C1 and C2 are capacitance values, V C1 (t-dt), V C2 (t-dt) represents the capacitor branch voltage at the previous time step. t is the current simulation time, and dt is the simulation step size.

[0075] Formula for calculating the equivalent parameters of inductance:

[0076]

[0077]

[0078]

[0079] Among them, L1, L2, L m L k I is the inductance value. L1 (t-dt), I Lm (t-dt), I' L2 (t-dt) represents the inductor branch current of the previous time step. t is the current simulation time, and dt is the simulation step size.

[0080] according to Figure 3 The system node voltage equations can be obtained as follows:

[0081] GV = I

[0082] Where G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

[0083] Based on the above circuit parameters, the system admittance matrix G, node voltage vector V, and node current vector I can be obtained as follows:

[0084]

[0085]

[0086]

[0087] S200: Check the switch change status, select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix, that is, according to the binary number (g 11 g 12 g 13 g 14 g 21 g 22 g 23 g 24 The system admittance matrix number is obtained and read directly from memory without recalculation.

[0088] S300: Calculate the historical current source based on the circuit information from the previous time step. That is, calculate the parameters in I based on the aforementioned circuit parameter formulas.

[0089] S400: The new node voltages are obtained by solving the system node voltage equations. That is, by obtaining the parameters in V, the voltage values ​​at the 7 nodes are obtained.

[0090] S500: Solve for branch voltage and branch current.

[0091] It should be noted that the branch voltage is the difference between the voltages at the two nodes of the branch, and the branch current is the branch voltage divided by the branch resistance.

[0092] S600: Determine if the simulation has ended. If not, increase the time step by one step, re-check the switch changes, and execute subsequent steps until the simulation ends.

[0093] Based on the above steps Figure 4 This is the simulation calculation process for the dual active bridge converter in this embodiment.

[0094] This embodiment provides a simulation method for a dual active bridge converter (DAB). It calculates the system admittance matrix for all switching states based on circuit parameters and saves them according to the switching state number. It checks the switching changes and selects the system admittance matrix corresponding to the current switching state from the saved system admittance matrices. It calculates historical current sources based on the circuit information from the previous time step. It solves the system node voltage equations to obtain the new node voltages. It solves for branch voltages and branch currents. It determines whether the simulation is complete; if not, it increases the time step, re-checks the switching changes, and executes subsequent steps until the simulation ends. This embodiment pre-calculates the system admittance matrix for all switching states and saves it according to the switching state number. During simulation iteration, after a switching state change, only the switching state needs to be used as an index to directly obtain the new system admittance matrix, avoiding the overhead of recalculating the system admittance matrix. Since the DAB operates at a high frequency and switching states change frequently, the method in this embodiment can effectively improve simulation efficiency.

[0095] The above is a detailed description of an embodiment of a simulation method for a dual active bridge converter according to the present invention. The following will provide a detailed description of an embodiment of a simulation system for a dual active bridge converter according to the present invention.

[0096] This embodiment provides a simulation system for a dual active bridge converter, including: a pre-calculation unit, an indexing unit, and a simulation calculation unit.

[0097] In this embodiment, the pre-calculation unit is used to calculate the system admittance matrix for all switching states based on the circuit parameters, and save them separately according to the switching state number.

[0098] First, calculate the equivalent circuit of the dual active bridge converter. Based on the equivalent circuit, obtain the circuit parameters, including the switching equivalent parameters. The formula for calculating the switching equivalent parameters is as follows:

[0099]

[0100]

[0101] In the formula, R on R is the on-resistance of the switch. off , where is the switch-off resistor, g is the switch signal, and n1 / n2 is the transformer turns ratio.

[0102] Furthermore, circuit parameters also include equivalent capacitance parameters, the formula for which is as follows:

[0103]

[0104]

[0105] In the formula, C1 and C2 are capacitance values, V C1 (t-dt), V' C2 (t-dt) is the voltage of the capacitor branch in the previous time step.

[0106] Furthermore, circuit parameters also include inductance equivalent parameters, the formula for calculating inductance equivalent parameters is as follows:

[0107]

[0108]

[0109]

[0110] Among them, L1, L2, L m L k I is the inductance value. L1 (t-dt), I Lm (t-dt), I' L2 (t-dt) represents the current in the inductor branch at the previous time step.

[0111] In this embodiment, the indexing unit is used to check the switch change and select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix;

[0112] In this embodiment, the simulation calculation unit is used to calculate the historical current source based on the circuit information of the previous time step; it is also used to obtain the new node voltage based on the system node voltage equation; it is also used to solve the branch voltage and branch current; it is also used to determine whether the simulation has ended. If not, it adds one time step and re-checks the switch change and executes the subsequent steps until the simulation ends.

[0113] The system node voltage equations are as follows:

[0114] GV = I

[0115] In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

[0116] It should be noted that the simulation system provided in this embodiment is used to implement the simulation method provided in the foregoing embodiment. The specific settings of each unit are based on the complete implementation of the method, and will not be repeated here.

[0117] 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 method for a dual active bridge converter, characterized in that, Includes the following steps: Calculate the system admittance matrix for all switching states based on the circuit parameters, and save them separately according to the switching state number; Check the switch changes and select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix; Calculate the historical current source based on the circuit information from the previous time step; The new node voltages are obtained by solving the system node voltage equations. Solve for the branch voltage and branch current; Determine if the simulation has ended. If not, increase the time step by one step, re-check the switch changes, and execute the subsequent steps until the simulation ends. The equivalent circuit of the dual active bridge converter is calculated, and the circuit parameters are obtained based on the equivalent circuit. The circuit parameters include switching equivalent parameters, and the calculation formula for the switching equivalent parameters is as follows: ； ； In the formula, The on-resistance of the switch. For switch-off resistor, For switching signals, This refers to the transformer turns ratio.

2. The simulation method for a dual active bridge converter according to claim 1, characterized in that, The circuit parameters also include equivalent capacitance parameters, which are calculated using the following formula: ； ； In the formula, , This is the capacitance value. , This is the voltage of the capacitor branch in the previous time step.

3. The simulation method for a dual active bridge converter according to claim 2, characterized in that, The circuit parameters also include the equivalent inductance parameter, which is calculated using the following formula: ； ； ； in, , , , This is the inductance value. , , This is the current in the inductor branch of the previous step.

4. The simulation method for a dual active bridge converter according to claim 1, characterized in that, The system node voltage equations are specifically as follows: ； In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

5. A simulation system for a dual active bridge converter, characterized in that, include: The pre-calculation unit is used to calculate the system admittance matrix for all switching states based on the circuit parameters and save them separately according to the switching state number. The index unit is used to check the switch change and select the system admittance matrix corresponding to the current switch state from the saved system admittance matrix; The simulation calculation unit is used to calculate the historical current source based on the circuit information of the previous time step; it is also used to solve the new node voltage based on the system node voltage equation; it is also used to solve the branch voltage and branch current; it is also used to determine whether the simulation has ended. If not, it will increase the time step by one step and re-enter the index unit until the simulation ends. The equivalent circuit of the dual active bridge converter is calculated, and the circuit parameters are obtained based on the equivalent circuit. The circuit parameters include switching equivalent parameters, and the calculation formula for the switching equivalent parameters is as follows: ； ； In the formula, The on-resistance of the switch. For switch-off resistor, For switching signals, This refers to the transformer turns ratio.

6. The simulation system for the dual active bridge converter according to claim 5, characterized in that, The circuit parameters also include equivalent capacitance parameters, which are calculated using the following formula: ； ； In the formula, , This is the capacitance value. , This is the voltage of the capacitor branch in the previous time step.

7. The simulation system for the dual active bridge converter according to claim 6, characterized in that, The circuit parameters also include the equivalent inductance parameter, which is calculated using the following formula: ； ； ； in, , , , This is the inductance value. , , This is the current in the inductor branch of the previous step.

8. The simulation system for the dual active bridge converter according to claim 5, characterized in that, The system node voltage equations are specifically as follows: ； In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

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