A simulation method and system of a dual active bridge converter with a circuit admittance matrix invariant

Abstract

The application provides a simulation method and system of a dual active bridge converter with an invariant circuit admittance matrix, wherein the method comprises the following steps: equivalent the dual active bridge converter to an equivalent circuit in which each branch is a parallel branch of a resistor and a historical current source; calculating a system admittance matrix according to each circuit parameter; checking a switching change condition, and calculating the historical current source according to circuit information of a previous time step; and solving a new node voltage according to a system node voltage equation, and then solving a branch voltage and a branch current until iteration is completed. The application calculates the system admittance matrix which does not change with a system state, and reflects the switching change in the equivalent current source of the switching branch. In the simulation process, only the equivalent current source of the switching branch needs to be updated, the overhead of recalculating the system admittance matrix is avoided, and a large memory required for precalculating a large number of system admittance matrices is also avoided.

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 with an invariant circuit admittance matrix. 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 with an invariant circuit admittance matrix, comprising the following steps:

[0008] Each branch of the dual active bridge converter is equivalent to a branch in parallel with a resistor and a historical current source to obtain the equivalent circuit.

[0009] The system admittance matrix is ​​calculated based on the circuit parameters of the equivalent circuit.

[0010] Check the switch changes and 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 circuit parameters include the switching equivalent parameters, and the formula for calculating the switching equivalent parameters is as follows:

[0015]

[0016]

[0017] Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; I g1x , I' g2x V is the current in the branch circuit of the previous step switch; g1x (t-dt), V′ g2x (t-dt) is the voltage of the switching branch in the previous time step.

[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 with an invariant circuit admittance matrix, comprising:

[0031] Equivalent units are used to convert each branch of a dual active bridge converter into a branch in parallel with a resistor and a historical current source, so as to obtain an equivalent circuit.

[0032] The admittance matrix calculation unit calculates the system admittance matrix based on the various circuit parameters of the equivalent circuit.

[0033] The simulation calculation unit is used to check the switching changes, calculate the historical current source based on the circuit information of the previous time step, obtain the new node voltage based on the system node voltage equation, solve the branch voltage and branch current, and 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.

[0034] Furthermore, the circuit parameters include the switching equivalent parameters, and the formula for calculating the switching equivalent parameters is as follows:

[0035]

[0036]

[0037] Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; I g1x , I' g2x V is the current in the branch circuit of the previous step switch; g1x (t-dt), V′ g2x (t-dt) is the voltage of the switching branch in the previous time step.

[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 with an invariant circuit admittance matrix. The method includes: equipping each branch of the dual active bridge converter with an equivalent circuit consisting of a resistor connected in parallel with a historical current source; calculating the system admittance matrix based on the circuit parameters of the equivalent circuit; checking switch changes and calculating the historical current source based on the circuit information from the previous time step; solving for the new node voltages using the system node voltage equations; solving for the branch voltages and currents; determining if the simulation is complete; if not, increasing the time step and re-checking the switch changes before executing subsequent steps until the simulation ends. This invention calculates a system admittance matrix that does not change with system state, while simultaneously reflecting switch changes in the equivalent current source of the switch branch. During simulation iteration, after a switch state change, only the equivalent current source of the switch branch needs to be updated, avoiding the overhead of recalculating the system admittance matrix and the large memory required for pre-calculating a large number of system admittance matrices. Since the DAB operates at a high frequency and switch states change frequently, this invention 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 with an invariant circuit admittance matrix 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 3 This 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 with an invariant circuit admittance matrix.

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

[0062] Please see Figure 1 This embodiment provides a simulation method for a dual active bridge converter with an invariant circuit admittance matrix, specifically including:

[0063] S100: Each branch of the dual active bridge converter is equivalent to a branch with a resistor connected in parallel with a historical current source to obtain the equivalent circuit.

[0064] like Figure 3 As shown, in this embodiment, each branch of the dual active bridge converter is equivalent to a branch in parallel with a resistor and a historical current source. This includes 7 nodes and 13 branches.

[0065] S200: Calculate the system admittance matrix based on the circuit parameters of the equivalent circuit.

[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] Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; I g1x , I' g2x V is the current in the branch circuit of the previous step switch; g1x (t-dt), V′ g2x (t-dt) is the voltage of the switching branch in the previous time step.

[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 kI 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] S300: Check the switch changes and 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.

[0088] 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.

[0089] S500: Solve for branch voltage and branch current.

[0090] 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.

[0091] 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.

[0092] Based on the above steps Figure 4 This is the simulation calculation process for the dual active bridge converter in this embodiment.

[0093] This embodiment provides a simulation method for a dual active bridge converter (DBC) with an invariant circuit admittance matrix. The method includes: equipping each branch of the DBC with an equivalent circuit by treating it as a branch with a resistor connected in parallel with a historical current source; calculating the system admittance matrix based on the circuit parameters of the equivalent circuit; checking for switch changes and calculating the historical current source based on the circuit information from the previous time step; solving for the new node voltages using the system node voltage equations; solving for the branch voltages and currents; determining if the simulation is complete; if not, increasing the time step and re-checking the switch changes before executing subsequent steps until the simulation ends. This embodiment calculates a system admittance matrix that does not change with system state, while reflecting switch changes in the equivalent current source of the switch branch. During simulation iteration, after a switch state change, only the equivalent current source of the switch branch needs to be updated, avoiding the overhead of recalculating the system admittance matrix and the large memory required for pre-calculating a large number of system admittance matrices. Since the DAB operates at a high frequency and switch states change frequently, the simulation method provided in this embodiment can effectively improve simulation efficiency.

[0094] The above is a detailed description of an embodiment of a simulation method for a dual active bridge converter with an invariant circuit admittance matrix 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 with an invariant circuit admittance matrix according to the present invention.

[0095] This embodiment provides a simulation system for a dual active bridge converter with an invariant circuit admittance matrix, including: an equivalent unit, an admittance matrix calculation unit, and a simulation calculation unit.

[0096] In this embodiment, the equivalent unit is used to convert each branch of the dual active bridge converter into a branch in parallel with a resistor and a historical current source, so as to obtain an equivalent circuit.

[0097] In this embodiment, the admittance matrix calculation unit is used to calculate the system admittance matrix based on the various circuit parameters of the equivalent circuit.

[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] Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; I g1x , I' g2x V is the current in the branch circuit of the previous step switch; g1x (t-dt), V′ g2x(t-dt) is the voltage of the switching branch in the previous time step.

[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 of the previous time step.

[0111] In this embodiment, the simulation calculation unit is used to check the switching changes, calculate the historical current source based on the circuit information of the previous time step, obtain the new node voltage based on the system node voltage equation, solve the branch voltage and branch current, and determine whether the simulation has ended. If not, it will increase the time step by one step, re-check the switching changes, and execute the subsequent steps until the simulation ends.

[0112] The system node voltage equations are as follows:

[0113] GV = I

[0114] In the formula, G is the system admittance matrix, V is the node voltage vector, and I is the injected current vector.

[0115] 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.

[0116] 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 with an invariant circuit admittance matrix, characterized in that, Includes the following steps: Each branch of the dual active bridge converter is equivalent to a branch in parallel with a resistor and a historical current source to obtain the equivalent circuit. The system admittance matrix is ​​calculated based on the circuit parameters of the equivalent circuit. Check the switch changes and 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 circuit parameters include switch equivalent parameters, and the calculation formula for the switch equivalent parameters is as follows: ； ； Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; , This refers to the current in the branch circuit of the previous time step switch; , This is the voltage of the branch circuit of the previous time step switch.

2. The simulation method for a dual active bridge converter with an invariant circuit admittance matrix 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 with an invariant circuit admittance matrix 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 with an invariant circuit admittance matrix 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 with an invariant circuit admittance matrix, characterized in that, include: Equivalent units are used to convert each branch of a dual active bridge converter into a branch in parallel with a resistor and a historical current source, so as to obtain an equivalent circuit. The admittance matrix calculation unit calculates the system admittance matrix based on the various circuit parameters of the equivalent circuit. The simulation calculation unit is used to check the switching changes, calculate the historical current source based on the circuit information of the previous time step, obtain the new node voltage based on the system node voltage equation, solve the branch voltage and branch current, and 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 circuit parameters include switch equivalent parameters, and the calculation formula for the switch equivalent parameters is as follows: ； ； Where e is the natural constant, g is the switching signal, and n1 / n2 is the transformer turns ratio; , This is the current in the branch circuit of the previous time step switch; , This is the voltage of the branch circuit of the previous time step switch.

6. The simulation system for a dual active bridge converter with an invariant circuit admittance matrix 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 a dual active bridge converter with an invariant circuit admittance matrix 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 a dual active bridge converter with an invariant circuit admittance matrix 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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