Modeling Method and Related Device of DAB Converter Based on Harmonic Analysis

Abstract

The present application discloses a modeling method and related device for a DAB converter based on harmonic analysis. The method includes: performing switch state analysis based on the constructed equivalent circuit of the DAB converter to obtain a bridge switch function; determining the initial time-domain state equation of the DAB converter according to preselected state variables and the bridge switch function; using the generalized state space method to perform state variable coefficient analysis and calculation according to the initial time-domain state equation to obtain a state coefficient differential equation, where the state variable coefficients include a zeroth-order coefficient and a first-order coefficient; constructing a time-domain state space model of the DAB converter according to a preset signal perturbation amount and the state coefficient differential equation; and converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain a frequency-domain state space model of the DAB converter. Therefore, the present application can solve the technical problem that the applicability of the existing technology is limited because the harmonic components or the coupling situation between different-frequency harmonics are not considered.

Description

Technical Field

[0001] This application relates to the technical field of power grid equipment modeling, and particularly to a modeling method and related device of a DAB converter based on harmonic analysis. Background Art

[0002] With the proposal of the "dual carbon" goal and the vigorous development of new energy technologies, more and more distributed generation and power electronic devices have begun to be connected to the power grid, making the power grid gradually show the characteristics of high power electronics. For different power electronic devices connected, in addition to the converters that occupy most of the dominant position, there are also many devices that will add high-frequency converters between the connected load and the converter to improve the voltage level and power quality. For the Dual Active Bridge (DAB) converter, it has the advantages of high power density and easy implementation of soft switching, and currently has a high frequency of application in various types of power electronic devices and DC power supply systems.

[0003] The generalized state space averaging method is used in the modeling process of high-power power electronic devices, but this method ignores the harmonic components and cannot reflect the interaction between nonlinear devices. The describing function method based on harmonic linearization can improve the modeling accuracy in the high-frequency band, but it is still essentially a single-input single-output model, does not consider the harmonic coupling between different frequencies, is difficult to realize the harmonic analysis in the low, medium, and high-frequency bands, and cannot be applied to multi-converter systems. Summary of the Invention

[0004] This application provides a modeling method and related device of a DAB converter based on harmonic analysis, which is used to solve the technical problem that the applicability of the existing technology is limited because it does not consider harmonic components or the coupling between harmonics of different frequencies.

[0005] In view of this, the first aspect of this application provides a modeling method of a DAB converter based on harmonic analysis, including:

[0006] Performing switch state analysis based on the constructed equivalent circuit of the DAB converter to obtain a bridge switch function;

[0007] Determining the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switch function;

[0008] Using the generalized state space method to perform state variable coefficient analysis and calculation according to the initial time-domain state equation to obtain a state coefficient differential equation, and the state variable coefficients include a zeroth-order coefficient and a first-order coefficient;

[0009] Constructing a time-domain state space model of the DAB converter according to a preset signal perturbation amount and the state coefficient differential equation;

[0010] Based on the harmonic state space modeling principle, the time-domain state space model is transformed into the frequency domain to obtain the frequency-domain state space model of the DAB converter.

[0011] Preferably, the switching state analysis is performed based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function, and the bridge switching function includes the primary-side bridge switching function and the secondary-side bridge switching function. It also includes before:

[0012] Construct an initial equivalent circuit according to the main circuit of the DAB converter;

[0013] Simplify the initial equivalent circuit by means of line excitation optimization to obtain the equivalent circuit of the DAB converter.

[0014] Preferably, after transforming the time-domain state space model into the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter, it further includes:

[0015] Solve the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter under steady-state conditions;

[0016] After calculating the frequency-domain steady-state solution according to the harmonic transfer function matrix, convert the frequency-domain steady-state solution into the time domain to obtain the time-domain steady-state solution;

[0017] Based on the time-domain steady state, verify the frequency-domain state space model to obtain the model verification result.

[0018] Preferably, after transforming the time-domain state space model into the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter, it further includes:

[0019] Construct a simulation model of the DAB converter according to the frequency-domain state space model, and perform simulation analysis of the DAB converter to obtain the simulation analysis result.

[0020] The second aspect of this application provides a DAB converter modeling device based on harmonic analysis, including:

[0021] A switching analysis unit for performing switching state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function;

[0022] A state analysis unit for determining the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switching function;

[0023] An equation calculation unit for performing state variable coefficient analysis and calculation according to the initial time-domain state equation by using the generalized state space method to obtain the state coefficient differential equation, and the state variable coefficients include the zeroth-order coefficient and the first-order coefficient;

[0024] A model construction unit, configured to construct a time-domain state space model of the DAB converter according to a preset signal perturbation amount and the state coefficient differential equation;

[0025] A time-frequency conversion unit, configured to convert the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain a frequency-domain state space model of the DAB converter.

[0026] Preferably, it further includes:

[0027] A circuit equivalent unit, configured to construct an initial equivalent circuit according to the main circuit of the DAB converter;

[0028] A circuit simplification unit, configured to simplify the initial equivalent circuit by means of line excitation optimization to obtain an equivalent circuit of the DAB converter.

[0029] Preferably, it further includes:

[0030] A model solution unit, configured to solve the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter in the steady state;

[0031] A steady-state solution unit, configured to calculate a frequency-domain steady-state solution according to the harmonic transfer function matrix and then convert the frequency-domain steady-state solution to the time domain to obtain a time-domain steady-state solution;

[0032] A model verification unit, configured to verify the frequency-domain state space model based on the time-domain steady state to obtain a model verification result.

[0033] Preferably, it further includes:

[0034] A simulation analysis unit, configured to construct a simulation model of the DAB converter according to the frequency-domain state space model and perform simulation analysis of the DAB converter to obtain a simulation analysis result.

[0035] The third aspect of the present application provides a DAB converter modeling device based on harmonic analysis, and the device includes a processor and a memory;

[0036] The memory is configured to store program codes and transmit the program codes to the processor;

[0037] The processor is configured to execute the DAB converter modeling method based on harmonic analysis described in the first aspect according to the instructions in the program codes.

[0038] The fourth aspect of the present application provides a computer-readable storage medium, and the computer-readable storage medium is configured to store program codes, and the program codes are used to execute the DAB converter modeling method based on harmonic analysis described in the first aspect.

[0039] As can be seen from the above technical solutions, the embodiments of the present application have the following advantages:

[0040] In the present application, a modeling method for a DAB converter based on harmonic analysis is provided, including: analyzing the switching states based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function; determining the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switching function; using the generalized state space method to analyze and calculate the state variable coefficients according to the initial time-domain state equation to obtain the state coefficient differential equation, where the state variable coefficients include the zeroth-order coefficient and the first-order coefficient; constructing the time-domain state space model of the DAB converter according to the preset signal perturbation amount and the state coefficient differential equation; and converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter.

[0041] The modeling method for a DAB converter based on harmonic analysis provided by the present application uses the generalized state space method to realize the modeling of the DAB converter. During this process, the state variable coefficients are analyzed and calculated for the initial time-domain state equation, which can grasp the coupling situation between harmonics of different frequencies, ensure the accuracy and reliability of the constructed model, and can realize harmonic analysis in the low, medium, and high frequency bands, improving the applicability of the solution. Therefore, the present application can solve the technical problem that the applicability of the existing technology is limited due to the lack of consideration of harmonic components or the coupling situation between harmonics of different frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic flowchart of the modeling method for a DAB converter based on harmonic analysis provided by the embodiments of the present application;

[0043] Figure 2 It is a schematic structural diagram of the modeling device for a DAB converter based on harmonic analysis provided by the embodiments of the present application;

[0044] Figure 3 It is a schematic structural diagram of the main circuit of the DAB converter provided by the embodiments of the present application;

[0045] Figure 4 It is a schematic structural diagram of the initial equivalent circuit of the DAB converter provided by the embodiments of the present application;

[0046] Figure 5 It is a schematic structural diagram of the equivalent circuit of the DAB converter provided by the embodiments of the present application;

[0047] Figure 6 It is a schematic flowchart of the harmonic state space modeling process provided by the embodiments of the present application;

[0048] Figure 7Schematic diagram of the DAB converter simulation structure provided by the embodiment of the present application;

[0049] Figure 8 Waveform diagram of the switch tube drive of single-phase shift control provided by the embodiment of the present application;

[0050] Figure 9 Waveform diagram of the primary and secondary side voltages of the transformer when the voltage transfer ratio is 1 provided by the embodiment of the present application;

[0051] Figure 10 Waveform diagram of the inductor voltage and inductor current when the voltage transfer ratio is 1 provided by the embodiment of the present application;

[0052] Figure 11 Waveform diagram of the output voltage and output current provided by the embodiment of the present application;

[0053] Figure 12 Waveform diagram of the primary and secondary side voltages of the transformer when the input voltage is increased to 1125V provided by the embodiment of the present application;

[0054] Figure 13 Waveform diagram of the inductor voltage and inductor current when the input voltage is increased to 1125V provided by the embodiment of the present application;

[0055] Figure 14 Waveform diagram of the output side voltage and current when a 4th-order voltage disturbance with an amplitude of 100V is added to the input side provided by the embodiment of the present application;

[0056] Figure 15 FFT diagram when a 4th-order voltage disturbance with an amplitude of 100V is added to the input side provided by the embodiment of the present application. Specific implementation manners

[0057] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0058] For ease of understanding, please refer to Figure 1 , the embodiment of the DAB converter modeling method based on harmonic analysis provided by the present application includes:

[0059] Step 101: Perform switch state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switch function.

[0060] Further, before step 101, it further includes:

[0061] Construct the initial equivalent circuit according to the main circuit of the DAB converter;

[0062] Simplify the initial equivalent circuit through line excitation optimization to obtain the equivalent circuit of the DAB converter.

[0063] For the main circuit of the DAB converter, please refer to Figure 3 , if n is the transformer turns ratio, and are the input voltage on the power supply side and the output voltage on the load side respectively; and are the output current on the power supply side and the complex variable output current of the transformer to the load side respectively; is the output current; and are the output voltages of the H-bridge at both ends of the converter respectively; is the auxiliary inductor; is the equivalent load; and are the buffer capacitor on the power supply side and the support capacitor on the load side respectively. Based on theoretical analysis, the following assumptions can be made about the circuit: the exciting inductance and resistance of the transformer are very large; the line resistance of the converter is very small and can be ignored; all capacitors of the converter are ideal capacitors; the IGBT loss is very small and can be ignored; the internal resistance of the power supply is very small and can be ignored; it is assumed that energy is transmitted from the primary side of the transformer to the secondary side of the transformer in a single phase, and the reactance and voltage on the secondary side are converted to the primary side.

[0064] Based on the above assumptions, the initial equivalent circuit of the main circuit of the DAB converter can be generated. For details, please refer to Figure 4 , where , are the equivalent resistance on the primary side and the equivalent leakage inductance on the primary side respectively, , are the exciting resistance and the exciting inductance respectively, , are the equivalent resistance on the secondary side and the equivalent leakage inductance on the secondary side respectively. Since the line resistance is very small while the exciting resistance is very large, the line exciting inductance and resistance branches are ignored, that is, line excitation optimization; after simplifying the initial equivalent circuit, the equivalent circuit of the DAB converter can be obtained. Please refer to Figure 5 , where and are the equivalent output voltages of the H-bridge at both ends of the converter respectively.

[0065] According to Figure 5 the equivalent circuit of the DAB converter, assuming that only the switching frequency is fixed and the duty cycle is 50% for the image shift modulation case, then the voltage across the transformer and There are only two states. The first state is when the switching transistors S1 and S3 are turned on. The second state is when the switching transistors S2 and S4 are turned on. Based on these two states, it can be obtained that:

[0066]

[0067] Among them, the switching function of the primary side bridge is:

[0068]

[0069] Among them, , and similarly, it can be obtained that:

[0070]

[0071] Among them, the switching function of the secondary side bridge is:

[0072]

[0073] Among them, and are the input voltage on the power supply side and the output voltage on the load side at time t respectively. Moreover, the bridge switching function includes the switching function of the primary side bridge and the switching function of the secondary side bridge.

[0074] Step 102: Determine the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switching function.

[0075] The preselected state variables are the inductor current and the output capacitor voltage . Combining the two bridge switching functions and , the initial time-domain state equation of the DAB converter can be obtained:

[0076]

[0077] Among them, in order to simplify the equation expression, the time expressions of the bridge switching functions and are omitted . This does not affect the representation of the bridge switching function and will not be elaborated further hereinafter.

[0078] Step 103: Adopt the generalized state space method to conduct state variable coefficient analysis and calculation according to the initial time-domain state equation to obtain the state coefficient differential equation. The state variable coefficients include the zeroth coefficient and the first coefficient.

[0079] Since the transformer current in the DAB converter is alternating current, the ripple is very large and the direct current is 0. The generalized averaging method can represent more details in the model with more terms in the Fourier series. Therefore, the generalized state space method is adopted in this embodiment to calculate the state variable coefficients according to the initial time domain state equation, specifically including state variables and , and the state variable coefficients include the zeroth coefficient and the first coefficient. The specific formula is expressed as:

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] Among them, represents the fundamental angular frequency.

[0087] Assume that the dynamic ratios of the input voltage and the load are much slower than the DAB converter. Then:

[0088]

[0089]

[0090] Since the duty cycle is fixed at 50%, the zeroth coefficients of the bridge switching function are all 0, that is:

[0091]

[0092] And the first coefficient is:

[0093]

[0094]

[0095] Substitute the zeroth coefficient and the first coefficient into the above several zeroth coefficient formulas and first coefficient formulas, and the state coefficient differential equation in matrix form can be solved:

[0096]

[0097] Among them, 、 、 They respectively represent the zeroth coefficient of the output capacitor voltage, the real part of the first coefficient of the inductor current, and the imaginary part of the first coefficient of the inductor current. According to the state coefficient differential equation, it can be found that the dynamic characteristics of the DAB converter can be expressed by using the zeroth coefficient of the output capacitor voltage and the first coefficient of the inductor current as state variables. If more orders are considered, the model will be more accurate.

[0098] Step 104: Construct a time-domain state space model of the DAB converter according to the preset signal perturbation amount and the state coefficient differential equation.

[0099] The preset signal perturbation amount in this embodiment is expressed as:

[0100]

[0101] Among them, , , respectively represent the phase shift ratio, the perturbation amount of the phase shift ratio, and the DC value of the phase shift ratio. , respectively represent the DC value of the zeroth coefficient of the output voltage and the perturbation amount of the zeroth coefficient of the output voltage. , , , respectively represent the DC value of the real part of the first coefficient of the inductor current, the perturbation amount of the real part of the first coefficient of the inductor current, the DC value of the imaginary part of the first coefficient of the inductor current, and the perturbation amount of the imaginary part of the first coefficient of the inductor current.

[0102] In the state coefficient differential equation, can be approximately expressed as:

[0103]

[0104] Therefore, the state coefficient differential equation with the preset signal perturbation amount can form a time-domain state space model of the DAB converter:

[0105]

[0106] Among them, , respectively represent the perturbation amounts of the bridge switching functions s1 and s2 of the bridge. , , respectively represent the input voltage perturbation amount, the output voltage perturbation amount, and the inductor current perturbation amount. C represents the bus capacitor on the output side.

[0107] Step 105: Convert the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter.

[0108] Please refer to the modeling principle of Harmonic State Space (HSS) in Figure 6 , which mainly utilizes the characteristics that the amplitude and phase angle of a periodic signal do not change with time in the frequency domain, converts time-domain variables to the frequency domain, and realizes the stationarization of a time-varying model. Define a linear time-periodic system as:

[0109]

[0110] Where, 、 、 、 represent the state coefficient, input coefficient, output coefficient, and correlation coefficient matrix of the harmonic state equation respectively, 、 、 、 represent the state variable, the frequency domain of the state variable, the output variable, and the input variable respectively. Any periodic signal can be represented by Fourier transform as:

[0111]

[0112] Where, represents the k-th Fourier coefficient of 、 represent the complex sign and the integer quantity respectively, is the fundamental angular velocity of

[0113] To describe the dynamic characteristics of the signal, use the exponentially modulated periodic signal as the general form of :

[0114]

[0115] Where, is the frequency domain parameter.

[0116] Expanding and analyzing the above formula, the harmonic state space equation containing all harmonic components can be obtained:

[0117]

[0118] Where, 、 are the defined integer signs respectively, 、 、 、 represent the value of the state variable X at the n-th time, the value of the state variable X at the m-th time, the value of the input variable U at the m-th time, and the value of the output variable Y at the n-th time respectively.

[0119] Represent the above harmonic state space equation in matrix form:

[0120]

[0121] Among them, , is the harmonic order considered, , , , are respectively Toeplitz matrices composed of the Fourier coefficients of , , , . Taking as an example, it is expressed as:

[0122]

[0123] The model constructed based on HSS is expressed as a harmonic state space equation, and its solution is expressed as X, which can be transformed into the time domain through the following formula:

[0124]

[0125] Among them, ; , is expressed as a diagonal matrix, and the diagonal elements are the values from e -jhω0t to e jhω0t .

[0126] Based on the above harmonic state space HSS modeling principle, the time-domain state space model of the DAB converter obtained above can be transformed into the frequency domain to obtain the frequency-domain state space model of the DAB converter:

[0127]

[0128] Among them, , represent the state variable matrices in the frequency domain and time domain, represents a block diagonal matrix composed of two N matrices, where N is a diagonal matrix of order (2h + 1), and h is the maximum harmonic order considered, is the input variable matrix, expressed as , , respectively represent the state coefficient matrix and input coefficient matrix in the main circuit, and can be respectively expressed as:

[0129]

[0130]

[0131] Among them, represents a zero matrix, , respectively represent the steady-state quantities of the switching function that defines the switching bridge, represents the toeplitz matrix of the switching function, , respectively represent the identity matrix and the steady-state quantity of the inductor current, represents the steady-state quantity of the output voltage. Taking the first element matrix in as an example, is composed of the Fourier coefficients after the exponential form Fourier decomposition of the time-domain signal of . Its dimension size is determined by the number of harmonics considered. For example, when studying the interaction relationship between h harmonics, then is a column matrix of 2h + 1, and the other matrix elements are similar. Define , in the matrix, is an identity matrix of order (2h + 1), is a zero matrix, with the size of a square matrix of order (2h + 1). is a block diagonal matrix composed of k matrices, where matrix is a diagonal matrix of order (2h + 1), and h is the maximum number of harmonics considered, represents the Toeplitz matrix of the corresponding elements. For the constant c, the corresponding Toeplitz matrix .

[0132] Furthermore, in step 105, it further includes:

[0133] Solving the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter in the steady state;

[0134] After calculating the frequency-domain steady-state solution according to the harmonic transfer function matrix, convert the frequency-domain steady-state solution to the time domain to obtain the time-domain steady-state solution;

[0135] Based on the time-domain steady state, verify the frequency-domain state space model to obtain the model verification result.

[0136] According to the above frequency-domain state space model of the DAB converter, the harmonic transfer function matrix in the stable state of the system can be solved:

[0137]

[0138] And according to the harmonic transfer function matrix the frequency-domain steady-state solution can be calculated again:

[0139]

[0140] Convert the frequency-domain steady-state solution Converting to the time domain, the steady-state solution in the time domain can be obtained. The steady-state solution in the time domain can verify the correctness of the already constructed frequency-domain state-space model to ensure the reliability of the model.

[0141] Furthermore, step 105 is followed by:

[0142] Construct a simulation model of the DAB converter based on the frequency-domain state-space model and conduct simulation analysis of the DAB converter to obtain the simulation analysis results.

[0143] For the simulation model of the DAB converter in this embodiment, please refer to Figure 7 , and for the simulation parameters, please refer to Table 1.

[0144] Table 1 DAB Converter Simulation Parameters

[0145]

[0146] When single-phase-shift control is adopted, there is only a phase-shift ratio between the full-bridges on both sides of the transformer, and the drive waves of its switching tubes are as Figure 8 shown. When the voltage transfer ratio is 1, for the voltage waveforms of the primary and secondary sides of the transformer, please refer to Figure 9 . It can be seen from this figure that when SPS control is adopted, square-wave voltages with a duty cycle of 50% are generated on both sides of the transformer, and the primary-side voltage leads the secondary-side voltage. For the waveforms of the inductor voltage and inductor current when the voltage transfer ratio is 1, please refer to Figure 10 . And for the waveforms of the output voltage and current, please refer to Figure 11 . According to this figure, it can be known that when the system is stable, the output voltage is stable at 400V and the voltage ripple is small. When other parameters remain unchanged and the input voltage is increased to 1125V, the voltage waveforms of the primary and secondary sides of the transformer are as Figure 12 shown, and its inductor voltage and current waveforms are as Figure 13 shown. Comparing Figs. 10 and Figure 13 , when the voltage transfer ratio increases, the maximum value of the inductor current increases from 50A to 63.6A, indicating that when the voltage transfer ratio is 1, the current stress is the smallest. When a 4th-order voltage disturbance with an amplitude of 100V is added to the input side, the output-side voltage and current waveforms obtained are as Figure 14 shown, and its corresponding FFT analysis is as Figure 15 shown; it can be seen from the figure that when a 4th-order voltage disturbance is introduced on the input side, DC voltage and current disturbances of the same frequency will be generated on the output side, and the amplitudes caused are both 0.457% of the output voltage and current in the steady state.

[0147] The DAB converter modeling method based on harmonic analysis provided by the embodiments of the present application uses the generalized state space method to implement the modeling of the DAB converter. During this process, the state variable coefficient analysis and calculation of the initial time-domain state equation are carried out, which can grasp the coupling situation between different-frequency harmonics, ensure the accuracy and reliability of the constructed model, and can realize the harmonic analysis in the low, medium, and high frequency bands, improving the applicability of the solution. Therefore, the embodiments of the present application can solve the technical problem that the prior art does not consider the harmonic components or the coupling situation between different-frequency harmonics, resulting in limited applicability of the method.

[0148] For ease of understanding, please refer to Figure 2 , embodiments of the DAB converter modeling device based on harmonic analysis provided by the present application include:

[0149] The switch analysis unit 201 is configured to perform switch state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switch function;

[0150] The state analysis unit 202 is configured to determine the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switch function;

[0151] The equation calculation unit 203 is configured to perform state variable coefficient analysis and calculation according to the initial time-domain state equation by using the generalized state space method to obtain the state coefficient differential equation, and the state variable coefficients include the zero-order coefficient and the first-order coefficient;

[0152] The model construction unit 204 is configured to construct the time-domain state space model of the DAB converter according to the preset signal perturbation amount and the state coefficient differential equation;

[0153] The time-frequency conversion unit 205 is configured to convert the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter.

[0154] Furthermore, it further includes:

[0155] The circuit equivalent unit 206 is configured to construct an initial equivalent circuit according to the main circuit of the DAB converter;

[0156] The circuit simplification unit 207 is configured to perform simplification processing on the initial equivalent circuit by means of line excitation optimization to obtain the equivalent circuit of the DAB converter.

[0157] Furthermore, it further includes:

[0158] The model solution unit 208 is configured to solve the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter in the steady state;

[0159] A steady-state solution unit 209, configured to calculate a steady-state solution in the frequency domain according to a harmonic transfer function matrix, and then convert the steady-state solution in the frequency domain to the time domain to obtain a steady-state solution in the time domain;

[0160] A model verification unit 210, configured to perform model verification on the frequency-domain state-space model based on the steady state in the time domain to obtain a model verification result.

[0161] Furthermore, it further includes:

[0162] A simulation analysis unit 211, configured to construct a simulation model of the DAB converter according to the frequency-domain state-space model and perform simulation analysis on the DAB converter to obtain a simulation analysis result.

[0163] This application also provides a DAB converter modeling device based on harmonic analysis. The device includes a processor and a memory;

[0164] The memory is used to store program codes and transmit the program codes to the processor;

[0165] The processor is configured to execute the DAB converter modeling method based on harmonic analysis in the method embodiments according to the instructions in the program codes.

[0166] This application also provides a computer-readable storage medium. The computer-readable storage medium is used to store program codes, and the program codes are used to execute the DAB converter modeling method based on harmonic analysis in the above method embodiments.

[0167] In several embodiments provided by this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the displayed or discussed coupling or direct coupling or communication connection to each other can be through some interfaces. The indirect coupling or communication connection of the devices or units can be in electrical, mechanical or other forms.

[0168] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0169] In addition, in each embodiment of the present application, the functional units can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0170] If the above integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks, or optical discs that can store program codes.

[0171] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present application.

Claims

1. A modeling method for DAB converters based on harmonic analysis, characterized in that Including: Performing switching state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function; Determining the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switching function; Using the generalized state space method to perform state variable coefficient analysis and calculation according to the initial time-domain state equation to obtain the state coefficient differential equation, where the state variable coefficients include the zeroth coefficient and the first coefficient; Constructing the time-domain state space model of the DAB converter according to the preset signal perturbation amount and the state coefficient differential equation; Converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter; Wherein, the bridge switching function includes the switching function of the primary bridge and the switching function of the secondary bridge; The switching function of the primary side bridge is as follows: ； Wherein, ； where f s is the switching frequency; The switching function of the secondary side bridge is as follows: ； The initial time-domain state equation is: ； is the inductor current, is the output capacitor voltage, omits the time expression of the switching function of the primary side bridge that omits the time expression of the switching function of the secondary side bridge, u in is the input voltage at the power supply side at the initial moment, L is the auxiliary inductor, is the equivalent load; is the load side support capacitor.

2. The method for modeling a DAB converter based on harmonic analysis according to claim 1, characterized in that, Before performing the switching state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function, which includes the primary bridge switching function and the secondary bridge switching function, it further includes: Constructing an initial equivalent circuit according to the main circuit of the DAB converter; Simplifying the initial equivalent circuit by means of line excitation optimization to obtain the equivalent circuit of the DAB converter.

3. The DAB converter modeling method based on harmonic analysis according to claim 1, wherein After converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter, it further includes: Solving the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter in the steady state; After calculating the frequency-domain steady-state solution according to the harmonic transfer function matrix, converting the frequency-domain steady-state solution to the time domain to obtain the time-domain steady-state solution; Performing model verification on the frequency-domain state space model based on the time-domain steady state to obtain the model verification result.

4. The modeling method of the DAB converter based on harmonic analysis according to claim 1, wherein After converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter, it further includes: Constructing a simulation model of the DAB converter according to the frequency-domain state space model and performing simulation analysis of the DAB converter to obtain the simulation analysis result.

5. DAB converter modeling device based on harmonic analysis, characterized in that Including: A switching analysis unit for performing switching state analysis based on the constructed equivalent circuit of the DAB converter to obtain the bridge switching function; A state analysis unit for determining the initial time-domain state equation of the DAB converter according to the preselected state variables and the bridge switching function; An equation calculation unit for using the generalized state space method to perform state variable coefficient analysis and calculation according to the initial time-domain state equation to obtain the state coefficient differential equation, where the state variable coefficients include the zeroth coefficient and the first coefficient; A model construction unit for constructing the time-domain state space model of the DAB converter according to the preset signal perturbation amount and the state coefficient differential equation; A time-frequency conversion unit for converting the time-domain state space model to the frequency domain based on the harmonic state space modeling principle to obtain the frequency-domain state space model of the DAB converter; Wherein, the bridge switching function includes the switching function of the primary bridge and the switching function of the secondary bridge; The switching function of the primary side bridge is as follows: ； Wherein, ； Where fs is the switching frequency; The switching function of the secondary side bridge is as follows: ； Among them, and are the input voltage on the power supply side and the output voltage on the load side at time t, respectively; The initial time-domain state equation is as follows: ； is the inductor current, is the output capacitor voltage, omits the time expression of switching function of the primary side bridge, omits the time expression of switching function of the secondary side bridge, u in is the input voltage at the power supply side at the initial moment, L is the auxiliary inductor, is the equivalent load; is the load side support capacitor.

6. The DAB converter modeling device based on harmonic analysis according to claim 5, characterized in that It further includes: A circuit equivalent unit for constructing an initial equivalent circuit according to the main circuit of the DAB converter; A circuit simplification unit for simplifying the initial equivalent circuit by means of line excitation optimization to obtain the DAB converter equivalent circuit.

7. The DAB converter modeling device based on harmonic analysis according to claim 5, characterized in that, It further includes: A model solution unit for solving the harmonic transfer function matrix of the frequency-domain state space model of the DAB converter under steady state; A steady-state solution unit for converting the frequency-domain steady-state solution to the time domain to obtain the time-domain steady-state solution after calculating the frequency-domain steady-state solution according to the harmonic transfer function matrix; A model verification unit for verifying the frequency-domain state space model based on the time-domain steady state to obtain a model verification result.

8. The DAB converter modeling device based on harmonic analysis according to claim 5, characterized in that, It further includes: A simulation analysis unit for constructing a simulation model of the DAB converter according to the frequency-domain state space model and performing DAB converter simulation analysis to obtain a simulation analysis result.

9. A DAB converter modeling device based on harmonic analysis, characterized in that The device includes a processor and a memory; The memory is used to store program codes and transmit the program codes to the processor; The processor is used to execute the DAB converter modeling method based on harmonic analysis according to the instructions in the program codes as described in any one of claims 1-4.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program codes, and the program codes are used to execute the DAB converter modeling method based on harmonic analysis according to any one of claims 1-4.

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