A state trajectory analysis method for short-circuit protection problem of CLLC converter

Abstract

The application provides a state trajectory analysis method for short-circuit protection of a CLLC converter, which comprises the following steps: performing work mode analysis on a time-domain working process of the CLLC converter in a soft-start process under constant-frequency constant-duty-ratio control, and obtaining time-domain equation groups under multiple working modes; adding resonant voltages and resonant currents of different edges in each time-domain equation group as trajectory variables; taking a sum of the resonant voltages as a horizontal axis and taking a sum of the resonant currents as a vertical axis, and drawing two-dimensional steady-state trajectories of the CLLC converter at different time points according to trajectory variable expressions; and based on a drawing rule of the two-dimensional steady-state trajectories, dynamically drawing short-circuit transient-state trajectories corresponding to each working mode after the CLLC converter occurs a short-circuit fault. The method establishes a state trajectory model of a short-circuit transient state of the CLLC converter based on work mode analysis, further introduces a time axis, dynamically generates three-dimensional state trajectories of short-circuit protection in a starting process, and improves analysis accuracy and convenience.

Description

Technical Field

[0001] This application relates to the field of short-circuit protection technology for resonant converters, and in particular to a state trajectory analysis method for short-circuit protection problems of CLLC converters. Background Technology

[0002] The Capacitor-Inductor-Inductor-Capacitor (CLLC) resonant converter is a high-frequency, high-efficiency isolated bidirectional DC / DC converter. Due to its outstanding soft-switching characteristics and excellent bidirectional power flow performance, CLLC converters have gradually attracted attention and have been applied in scenarios such as vehicle-to-grid (V2G) systems, battery energy storage systems (BES), and electric aircraft. Besides efficiency, reliability is also an important evaluation metric for CLLC converters, with short-circuit fault protection being a key aspect of reliability research.

[0003] In related technologies, the modeling and analysis of the short-circuit protection process for CLLC converters lacks effective methods. Consequently, the common approach for CLLC converter short-circuit protection is to use fundamental frequency analysis from the perspective of equivalent gain. However, the equivalent gain model established in this way only considers the fundamental frequency component, resulting in an inaccurate model for analyzing practical problems, which may affect the short-circuit protection results of the CLLC converter.

[0004] Therefore, how to analyze the short-circuit protection process of CLLC converters using simple and accurate analytical methods has become an urgent problem to be solved. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art.

[0006] Therefore, the first objective of this application is to propose a state trajectory analysis method for short-circuit protection of CLLC converters. This method establishes a state trajectory model of the short-circuit transient state of the CLLC converter based on operating mode analysis. By analyzing the dynamic changes of the trajectory, the transient behavior of the converter after the short-circuit process is analyzed, thereby improving the accuracy and convenience of short-circuit protection process analysis.

[0007] The second objective of this application is to propose a state trajectory analysis system for short-circuit protection of CLLC converters;

[0008] The third objective of this application is to provide a non-transitory computer-readable storage medium.

[0009] To achieve the above objectives, the first aspect of this application is to propose a state trajectory analysis method for short-circuit protection problems in CLLC converters, the method comprising the following steps:

[0010] The time-domain operating process of the CLLC converter under constant frequency and constant duty cycle control during soft start is analyzed to obtain the time-domain equations of the CLLC converter under multiple operating modes.

[0011] The time-domain equations under the multiple operating modes are organized, and the resonant voltage and resonant current of different sides in each time-domain equation are added together as trajectory variables to obtain the trajectory variable expression;

[0012] Using the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, the two-dimensional steady-state trajectory of the CLLC converter at different times is plotted according to the trajectory variable expression.

[0013] Based on the drawing rules of the two-dimensional steady-state trajectory, the short-circuit transient trajectory corresponding to each working mode after the CLLC converter experiences a short-circuit fault is dynamically drawn.

[0014] Optionally, in one embodiment of this application, the operational mode analysis of the time-domain operation of the CLLC converter under constant frequency and constant duty cycle control during soft start includes: dividing the operation of the CLLC converter under fixed duty cycle control into multiple operational modes according to the structure of the resonant cavity and the direction of the resonant current; constructing an equivalent circuit diagram corresponding to each operational mode; constructing a set of time-domain equations for each operational mode according to each equivalent circuit diagram; and setting boundary conditions for solving the time-domain equations for the multiple operational modes, taking into account the continuity of voltage and current, the symmetry of circuit operation, and the duration of each operational mode.

[0015] Optionally, in one embodiment of this application, the time-domain equation set for each operating mode includes: an expression for the primary resonant current, an expression for the secondary resonant current, an expression for the primary resonant voltage, and an expression for the secondary resonant voltage of the CLLC converter.

[0016] Optionally, in one embodiment of this application, the plurality of operating modes include: a first mode, a second mode, a third mode, and a fourth mode; the step of drawing the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression includes: determining the center of the first mode and the second mode at the initial time according to the trajectory variable expression, drawing the circular arc trajectory of the first mode and the second mode according to the different center, and drawing the elliptical arc trajectory corresponding to the third mode and the fourth mode; and analyzing the contraction of the two-dimensional steady-state trajectory corresponding to each operating mode at different times when the CLLC converter is soft-started.

[0017] Optionally, in one embodiment of this application, the step of dynamically drawing the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in the CLLC converter includes: analyzing the changes in the center and radius of the trajectories corresponding to the first and second modes after the short-circuit fault occurs; and determining the expanded range of the short-circuit transient trajectories corresponding to the first and second modes by combining the changes in the center, the changes in the radius, and the trajectories of the first and second modes at the initial time.

[0018] Optionally, in one embodiment of this application, after dynamically drawing the short-circuit transient trajectory corresponding to each operating mode after the CLLC converter experiences a short-circuit fault, the method further includes: building a time-domain model of the CLLC converter in a simulation analysis application using the operating mode method, and setting the operating parameters of the CLLC converter; and obtaining the state trajectory simulation results during the soft-start process of the CLLC converter through normalization based on the obtained simulation analysis data, wherein the simulation results show the contraction and transient change process of the state trajectory.

[0019] Optionally, in one embodiment of this application, after dynamically drawing the short-circuit transient trajectory corresponding to each working mode after the CLLC converter experiences a short-circuit fault, the method further includes: building an experimental prototype of the CLLC converter and setting the working parameters of the CLLC converter; setting the short-circuit fault time after the start of soft start on the introduced time axis, and dynamically generating the three-dimensional state trajectory of short-circuit protection during the converter startup process based on the acquired experimental waveform.

[0020] To achieve the above objectives, a second aspect of this application also proposes a state trajectory analysis system for short-circuit protection of CLLC converters, comprising the following modules:

[0021] The analysis module is used to perform operating mode analysis on the time-domain operation of the CLLC converter during the soft start process under constant frequency and constant duty cycle control, and obtain the time-domain equations of the CLLC converter under multiple operating modes.

[0022] The sorting module is used to sort out the time-domain equations under the multiple working modes, and add the resonant voltage and resonant current of different sides in each time-domain equation as trajectory variables to obtain the trajectory variable expression;

[0023] The first drawing module is used to draw the two-dimensional steady-state trajectory of the CLLC converter at different times, with the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, according to the trajectory variable expression.

[0024] The second drawing module is used to dynamically draw the short-circuit transient trajectory corresponding to each working mode after the CLLC converter experiences a short-circuit fault, based on the drawing rules of the two-dimensional steady-state trajectory.

[0025] To implement the above embodiments, a third aspect of this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the state trajectory analysis method for short-circuit protection of CLLC converters described in the first aspect.

[0026] The technical solution provided by the embodiments of this application brings at least the following beneficial effects: This application addresses the short-circuit fault occurrence during the constant-frequency, constant-duty-cycle soft-start process of a CLLC converter. Based on the operating mode analysis method, it models the CLLC converter, constructs new state variables using resonant current and resonant voltage to plot the steady-state state trajectory, and then provides the transient trajectory changes during the short-circuit protection process, constructing a short-circuit transient state trajectory model. Therefore, trajectory analysis can be used to reflect the converter's operating process, and the dynamic changes in the trajectory reflect the transient behavior of the CLLC converter after the short-circuit process, simplifying complex and abstract mathematical equation calculations into trajectory plotting. Thus, this application improves the accuracy, comprehensiveness, and convenience of CLLC converter short-circuit protection process analysis, providing a foundation for subsequent related protection and control design, and contributing to ensuring the safe and stable operation of the CLLC converter.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 This is a flowchart illustrating a state trajectory analysis method for short-circuit protection of CLLC converters proposed in an embodiment of this application;

[0030] Figure 2 This is a schematic diagram of the topology of a CLLC converter proposed in an embodiment of this application;

[0031] Figure 3 This is a schematic diagram illustrating multiple operating modes of a CLLC converter according to an embodiment of this application;

[0032] Figure 4 This is a schematic diagram of an equivalent circuit for different operating modes proposed in an embodiment of this application;

[0033] Figure 5 This is a schematic diagram of a boundary condition proposed in an embodiment of this application;

[0034] Figure 6 This is a schematic diagram of a state trajectory proposed in an embodiment of this application;

[0035] Figure 7 This is a schematic diagram of another state trajectory proposed in an embodiment of this application;

[0036] Figure 8 This is a schematic diagram of a transient trajectory after a short-circuit fault, as proposed in an embodiment of this application.

[0037] Figure 9 This is a schematic diagram of the simulation results of a short-circuit protection during startup proposed in an embodiment of this application;

[0038] Figure 10 This is a schematic diagram illustrating an experimental result presented in an embodiment of this application;

[0039] Figure 11 This is a schematic diagram illustrating another experimental result presented in an embodiment of this application;

[0040] Figure 12 This is a schematic diagram of the state trajectory analysis system for short-circuit protection of CLLC converters proposed in an embodiment of this application. Detailed Implementation

[0041] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0042] It should be noted that in the relevant embodiments, short-circuit protection analysis of CLLC converters generally utilizes the fundamental frequency analysis method, combining the switching frequency and duty cycle of the primary-side switches of the CLLC converter to establish an equivalent gain model of the converter. This method only considers the fundamental frequency component, therefore the resulting model is not accurate when analyzing practical problems. Furthermore, in other relevant embodiments, a time-domain operating model of the CLLC converter is established using the operating mode analysis method. This model can accurately characterize the actual operating state of the converter, but it is mainly suitable for steady-state analysis and cannot model the transient process of short-circuit protection.

[0043] The state trajectory method used in this application is proposed based on operating mode analysis. However, due to the complexity of the operating modes of CLLC converters, there is currently no state trajectory model. Furthermore, the short-circuit process of CLLC converters involves transient changes, for which there is currently no accurate modeling method.

[0044] Therefore, there is a lack of specific analysis methods for the short-circuit protection process during the startup of CLLC converters. This application proposes a state trajectory analysis and system for the short-circuit protection problem of CLLC converters, so as to reflect the working state of the converter through simple trajectory drawing.

[0045] The following description, with reference to the accompanying drawings, illustrates a state trajectory analysis method and system for short-circuit protection of CLLC converters, as proposed in an embodiment of the present invention.

[0046] Figure 1 This is a flowchart of a state trajectory analysis method for short-circuit protection of CLLC converters proposed in this application, as shown in the embodiment. Figure 1 As shown, the method includes the following steps:

[0047] Step S101: Perform a working mode analysis on the time-domain operation of the CLLC converter during the soft start process under constant frequency and constant duty cycle control to obtain the time-domain equations of the CLLC converter under multiple working modes.

[0048] Specifically, this application addresses the short-circuit fault occurrence during the constant-frequency, constant-duty-cycle soft-start process of a CLLC converter, and establishes a short-circuit transient state trajectory model based on operating mode analysis. To facilitate the subsequent analysis process, the CLLC converter involved in this application will be described below.

[0049] For example, the CLLC converter topology involved in this application is as follows: Figure 2 As shown, S1 to S4 are primary-side switches, S5 to S8 are secondary-side switches, and C... r1 L is the primary resonant capacitor. r1 For the primary resonant inductance, C r2For the secondary resonant capacitor, L r2 For secondary resonant inductance, L m The transformer has a magnetizing inductor with a turns ratio of n:1 and a primary resonant current i. p Secondary resonant current i s Excitation current i Lm The positive directions of the voltages at each terminal are shown in the figure. The voltage across the primary resonant capacitor is the primary resonant voltage, and the voltage across the secondary resonant capacitor is the secondary resonant voltage.

[0050] Furthermore, this application performs a working mode analysis on the time-domain operation of a CLLC converter with fixed narrow pulse control during soft start-up. As an example, in the analysis process, the switching frequency corresponding to the primary-side switch is set to be equal to the resonant frequency (f). s =f r The duty cycle is a fixed value D for achieving soft start. ref The secondary-side switch operates in uncontrolled rectification mode.

[0051] In one embodiment of this application, the time-domain operating mode analysis of the soft-start process of a CLLC converter under constant frequency and constant duty cycle control includes the following steps: First, based on the structure of the resonant cavity and the direction of the resonant current, the operating process of the CLLC converter under fixed duty cycle control is divided into multiple operating modes; then, an equivalent circuit diagram corresponding to each operating mode is constructed; next, based on each equivalent circuit diagram, a set of time-domain equations for the corresponding operating mode is constructed; finally, considering the continuity of voltage and current, the symmetry of circuit operation, and the duration of each operating mode, boundary conditions are set for solving the time-domain equations for multiple operating modes.

[0052] Specifically, in this embodiment, the analysis of the time-domain working process using the working mode method includes the following key steps:

[0053] The first step is to distinguish the operating modes. The operation of a CLLC converter under fixed duty cycle control can consist of different operating modes. In this embodiment, according to... Figure 2 The structure of the resonant cavity and the direction of the resonant current divide it into multiple operating modes, such as... Figure 3 As shown, different working modes are named as the first mode ( Figure 3 The four modes correspond to the P mode, the N mode, the Z0 mode, and the Z mode. The operating modes of the converter are consistent throughout the positive and negative half-cycles. In this embodiment, the following analysis focuses on the positive half-cycle. Figure 3 Devices that do not participate in operation in this mode are displayed in a diluted grayscale.

[0054] The second step is to refine the equivalent circuit. Based on the above division of operating modes, the equivalent circuits for different operating modes can be given as follows: Figure 4 As shown, in the P-mode and N-mode, both the primary and secondary resonant cavities participate in resonance, and the circuit is a fourth-order network. In the Z0-mode and Z-mode, only the secondary resonant cavity participates in resonance, and the circuit is a second-order network.

[0055] The third step is to derive the time-domain equations. Based on... Figure 4 The equivalent circuits of the LCC converter under different operating modes are given, and time-domain equations for each mode can be written separately. In this embodiment, the time-domain equations for each operating mode include: expressions for the primary resonant current, secondary resonant current, primary resonant voltage, and secondary resonant voltage of the CLLC converter. The time-domain equations for the P mode, N mode, Z0 mode, and Z mode are listed in detail in Table 1 below.

[0056] Table 1. Time-domain equations for different modes

[0057]

[0058] Where P1, P2, P3, and P4 represent the undetermined coefficients of the P mode, and N1, N2, N3, and N4 represent the undetermined coefficients of the N mode, Z... 01 Z 02 Z1 and Z2 are the undetermined coefficients of the Z0 mode and Z mode, respectively, M is the voltage gain, and the other variables are calculated as follows: φ = 2πf r t, k = L m / L r1 , The meaning of each parameter is as follows: Figure 2 The meanings are consistent, and this application will not repeat the meanings of parameters that have already been given.

[0059] The fourth step is to define the boundary conditions. After deriving the time-domain equations for different modes, the corresponding boundary conditions need to be given, as shown in Figure 5. Based on the continuity of voltage and current, the symmetry of circuit operation, and the duration of each mode, F1-F can be given. 16 There are 16 boundary conditions used to solve the modal equations.

[0060] The fifth step is to solve for the required parameters.

[0061] Step S102: Organize the time-domain equations under multiple operating modes, and add the resonant voltage and resonant current of different sides in each time-domain equation as trajectory variables to obtain the trajectory variable expression.

[0062] Specifically, based on the previous step, the state trajectory of the short-circuit protection for the CLLC converter proposed in this application is analyzed. This step first involves organizing the modal equations. Specifically, by applying the aforementioned working modal analysis method to model the time-domain operating process of the CLLC converter under fixed duty cycle control, the time-domain equations for P-mode, N-mode, Z0-mode, and Z-mode are obtained. The i-th equations for each mode are then... p and i s Add, u cr1 and u cr2 Adding them together creates a new trajectory variable, resulting in the trajectory variable expression represented by the following formula:

[0063]

[0064] Among them, i P =i p,P +i s,P u P =u cr1,P +u cr2,P i N =i p,N +i s,N u N =u cr1,N +u cr2,N i zo =i p,zo +i s,zo u zo =u cr1,zo +u cr2,2o i z =i p,z +i s,z u z =u cr1,z +u cr2,z .

[0065] Step S103: Using the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, plot the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression.

[0066] Specifically, the steady-state trajectory of the CLLC converter is plotted. Continuing with the example above, this application will... cr1 and u cr2 The sum of the two values ​​is used as the horizontal axis, i p and i s Using the sum as the vertical axis, the trajectory shapes of the P mode, N mode, Z0 mode, and Z mode can be obtained from the above trajectory variable expressions, as shown in Table 2 below.

[0067] Table 2. Shapes of State Trajectories in Different Modes

[0068]

[0069] In one embodiment of this application, drawing the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression includes: determining the center of the first mode and the second mode at the initial time according to the trajectory variable expression; drawing the circular arc trajectory of the first mode and the second mode according to the different center; and drawing the elliptical arc trajectory corresponding to the third mode and the fourth mode; and analyzing the contraction of the two-dimensional steady-state trajectory corresponding to each working mode at different times when the CLLC converter is soft-started.

[0070] Specifically, in this embodiment, Table 2 above is first obtained based on the trajectory variable expression, and then the trajectory drawing method is determined based on Table 2. The trajectory method can vividly represent the working state of the converter. The trajectory when M=0 and M=M1 are used as examples to specifically introduce the composition and drawing principle of the trajectory.

[0071] As an example, such as Figure 6 The diagram shows the state trajectory when M=0, where segment AE is the trajectory of the positive half-cycle, and the remaining part is the trajectory of the negative half-cycle. It should be noted that, for ease of understanding, different trajectories are distinguished by different colors in the accompanying drawings of this application, and to facilitate comparison of trajectory changes, [further details are needed]. Figures 6 to 8 In the image, the trajectory of M at other times is displayed in a faded form.

[0072] Specifically, segment AB is the P-mode trajectory, which is an arc centered at (1,0); segment BC is the N-mode trajectory, which is an arc centered at (-1,0); segment CD is the Z0-mode trajectory, which is an elliptical arc; and segment DE is the Z-mode trajectory, which is an elliptical arc.

[0073] Furthermore, in combination Figure 7 As shown in the trajectory when M=M1, the trajectory shows a contraction trend as startup progresses. Since this embodiment uses a fixed duty cycle control method, the time corresponding to the P mode remains unchanged. This is reflected in the trajectory as the central angle corresponding to segment AB remains unchanged. Therefore, the trajectory does not contract proportionally but rather rotates, which translates to longer times for the Z0 and Z modes in actual converter operation. Furthermore, since the state trajectory is drawn using resonant cavity parameters, its area reflects the energy transmitted by the converter to some extent. The contraction of the trajectory corresponds to the energy limitation characteristics of the converter during startup.

[0074] Step S104: Based on the drawing rules of the two-dimensional steady-state trajectory, dynamically draw the short-circuit transient trajectory corresponding to each working mode after the CLLC converter experiences a short-circuit fault.

[0075] Specifically, the short-circuit transient trajectory of the CLLC converter after a short-circuit fault is plotted. Based on the patterns observed in the steady-state trajectory plotting process in step S103 above, the state trajectory during the short-circuit protection transient process can be plotted.

[0076] In one embodiment of this application, the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in a CLLC converter is dynamically plotted, including: analyzing the changes in the center and radius of the trajectories corresponding to the first and second modes after the short-circuit fault occurs; and determining the expanded range of the short-circuit transient trajectories corresponding to the first and second modes respectively by combining the changes in the center and radius of the trajectories and the trajectories of the first and second modes at the initial moment.

[0077] Specifically, in this embodiment, for ease of description, it is assumed that a short-circuit fault occurs when the CLLC converter starts up to M=M1. Since the fixed duty cycle control method used in this application has natural short-circuit protection capability, the process trajectory is as follows: Figure 8 As shown, the principle of drawing transient trajectories will be discussed segment by segment below. Since the Z0 mode and the Z mode account for a very small proportion of the trajectory, they can be ignored in the analysis.

[0078] For trajectory AB: Trajectory AB is the P-mode trajectory after a short-circuit fault. Since the output voltage drops to 0 instantaneously during a short circuit, the center of the trajectory will move from (1-M1, 0) to (1, 0), and thus the trajectory radius will change from R. p1 Increase to R p2 Since point A lies on the locus of M = M1, the corresponding new radius should be smaller than the radius when M = 0, i.e., R. p2 <R p5 Therefore, the trajectory AB will expand, but it will not exceed the trajectory when M=0, and this will be the range of expansion.

[0079] For trajectory BC: Trajectory BC reflects the trajectories of N mode, Z0 mode and Z mode. It mainly considers the changes of N mode trajectory. Similar to P mode, the center of N mode trajectory moves to (-1,0). However, since point B is not on the trajectory of M=0 at this time, trajectory BC will expand but will not exceed the trajectory of M=0. This is used as the expansion range.

[0080] For trajectory CD: Trajectory CD reflects the P mode of the negative half-cycle, and its trajectory will further expand, but will not exceed the trajectory of M=0.

[0081] Therefore, the present application embodiment can intuitively depict the short circuit protection process using the above-mentioned state trajectory analysis method. Since the trajectory will be limited to the trajectory of M=0 after the fault occurs, that is, the voltage and current in the converter will not exceed the state at the start of startup after the short circuit occurs, thereby ensuring the reliability of the analysis method of the present application.

[0082] Based on the above embodiments, in order to more fully illustrate the feasibility and effectiveness of the state trajectory analysis method of this application, the following description uses two specific verification embodiments in practical applications.

[0083] In one embodiment of this application, after dynamically plotting the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in the CLLC converter, the method further includes: building a time-domain model of the CLLC converter in a simulation analysis application using the operating mode method, and setting the operating parameters of the CLLC converter; and obtaining the state trajectory simulation results during the soft-start process of the CLLC converter by normalization based on the obtained simulation analysis data, wherein the simulation results show the contraction and transient change process of the state trajectory.

[0084] Specifically, this embodiment provides simulation verification results for the state trajectory analysis method proposed in this application. In the simulation analysis software, the working mode method in step S101 above is used to build a time-domain model of the CLLC converter, and the CLLC converter parameters are set in the software as: L r1 =L r2 =35uH,C r1 =C r2 =34nF,L m =386uH, transformer turns ratio n=1, select D=0.167 as the control pulse duty cycle, and set the switching frequency fs. s =f r =145.9kHz. Then, run the simulation program according to the settings. Based on the obtained simulation data, the state trajectory of the short-circuit protection during startup can be obtained by normalization as follows: Figure 9 As shown. By Figure 9 The simulation results show that the state trajectory analysis method provided in this application accurately describes the working process of the converter through trajectory contraction and transient changes.

[0085] In one embodiment of this application, after dynamically drawing the short-circuit transient trajectory corresponding to each working mode after a short-circuit fault occurs in the CLLC converter, the method further includes: building an experimental prototype of the CLLC converter and setting the working parameters of the CLLC converter; setting the short-circuit fault time after the start of soft start on the introduced time axis; and dynamically generating the three-dimensional state trajectory of short-circuit protection during the start-up process of the converter based on the acquired experimental waveform, thereby constructing a three-dimensional state trajectory model of the CLLC converter that reflects time changes.

[0086] Specifically, this embodiment provides experimental verification results for the soft-start control method with natural short-circuit protection capability proposed in this application. In the experimental verification, the CLLC converter parameters are set as: L r1 =Lr2 =35uH,C r1 =C r2 =34nF,L m =386uH, transformer turns ratio n=1, and an experimental prototype was built. The prototype included: a short-circuit switch, control board, auxiliary power supply, input side, primary-side H-bridge, secondary-side H-bridge, output side, transformer, and resonant cavity. A short-circuit fault was applied to the output side 13ms after the prototype started, and the obtained experimental waveforms are shown below. Figure 10 and Figure 11 As shown, a timeline was constructed by introducing a timeline. Figure 11 The illustrated three-dimensional state trajectory model reflects time-varying characteristics. This model can be used to determine the three-dimensional state trajectory during short-circuit protection in the converter startup process. Therefore, the state trajectory analysis method of this application can accurately reflect the actual working process of the converter.

[0087] Therefore, this application first establishes a time-domain operating model of the CLLC converter under constant frequency and constant duty cycle control; then, it plots the two-dimensional state trajectory of the CLLC converter by adding the resonant voltage and resonant current; then, it proposes a dynamic plotting method for the state trajectory for short-circuit faults; finally, it introduces a time axis to construct a three-dimensional state trajectory model that reflects time-varying changes.

[0088] In summary, the state trajectory analysis method for short-circuit protection of CLLC converters in this application addresses the short-circuit fault occurrence during the constant-frequency, constant-duty-cycle soft-start process of the CLLC converter. Based on the operating mode analysis method, the CLLC converter is modeled, and new state variables are constructed using resonant current and resonant voltage to plot the steady-state state trajectory. This, in turn, provides the transient trajectory changes during the short-circuit protection process, constructing a short-circuit transient state trajectory model. Therefore, trajectory analysis can be used to reflect the converter's operating process, and the dynamic changes in the trajectory reflect the transient behavior of the CLLC converter after the short-circuit process, simplifying complex and abstract mathematical equation calculations into trajectory plotting. Thus, this method improves the accuracy, comprehensiveness, and convenience of short-circuit protection process analysis for CLLC converters, providing a foundation for subsequent protection and control design and contributing to ensuring the safe and stable operation of CLLC converters.

[0089] To implement the above embodiments, this application also proposes a state trajectory analysis system for the short-circuit protection problem of CLLC converters. Figure 12 This is a schematic diagram of the structure of a state trajectory analysis system for short-circuit protection of CLLC converters proposed in an embodiment of this application, as shown below. Figure 12 As shown, the system includes: an analysis module 100, an organization module 200, a first drawing module 300, and a second drawing module 400.

[0090] The analysis module 100 is used to perform working mode analysis on the time-domain working process of the CLLC converter during the soft start process under constant frequency and constant duty cycle control, and obtain the time-domain equations of the CLLC converter under multiple working modes.

[0091] The sorting module 200 is used to sort out the time-domain equations under multiple operating modes. It adds up the resonant voltage and resonant current of different sides in each time-domain equation as trajectory variables to obtain the trajectory variable expression.

[0092] The first plotting module 300 is used to plot the two-dimensional steady-state trajectory of the CLLC converter at different times, with the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, according to the trajectory variable expression.

[0093] The second drawing module 400 is used to dynamically draw the short-circuit transient trajectory corresponding to each working mode after a short-circuit fault occurs in the CLLC converter, based on the drawing rules of the two-dimensional steady-state trajectory.

[0094] Optionally, in one embodiment of this application, the analysis module 100 is specifically used to: divide the working process of the CLLC converter under fixed duty cycle control into multiple working modes according to the structure of the resonant cavity and the direction of the resonant current; construct an equivalent circuit diagram corresponding to each working mode; construct a set of time-domain equations for the corresponding working mode according to each equivalent circuit diagram; and set boundary conditions for solving the time-domain equations for multiple working modes by combining the continuity of voltage and current, the symmetry of circuit operation and the duration of each working mode.

[0095] It should be noted that the explanation of the aforementioned embodiment of the state trajectory analysis method for the short-circuit protection problem of CLLC converter also applies to the system of this embodiment. The implementation principle is the same, and the functions of each module will not be repeated here.

[0096] In summary, the real-time clock (RTC) fault detection system of this application embodiment, without requiring additional external hardware devices or relying on external communication, can monitor the RTC timestamp in real time through relevant software algorithms to detect the accuracy of the device chip RTC and accurately detect various types of RTC faults. Therefore, this system reduces the cost of RTC detection, saves external communication steps, and reduces the complexity of detection. Furthermore, it can detect multiple faults and specifically locate the current fault type in the RTC, improving the accuracy and reliability of the detection results and refining the results. Moreover, the system can also implement automatic RTC calibration, reporting faults after identification and calibrating the clock signal of abnormal RTCs based on the RTC detection results. The calibration method is relatively simple, which helps ensure the normal and stable operation of the RTC.

[0097] To implement the above embodiments, this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the state trajectory analysis method for short-circuit protection of CLLC converters as described in any one of the first aspect embodiments above.

[0098] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0099] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0100] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0101] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0102] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0103] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0104] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0105] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A state trajectory analysis method for short-circuit protection problems in CLLC converters, characterized in that, Includes the following steps: The time-domain operating process of the CLLC converter under constant frequency and constant duty cycle control during soft start is analyzed to obtain the time-domain equations of the CLLC converter under multiple operating modes. The time-domain equations under the multiple operating modes are organized, and the resonant voltage and resonant current of different sides in each time-domain equation are added together as trajectory variables to obtain the trajectory variable expression; Using the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, the two-dimensional steady-state trajectory of the CLLC converter at different times is plotted according to the trajectory variable expression. Based on the drawing rules of the two-dimensional steady-state trajectory, the short-circuit transient trajectory corresponding to each working mode after the CLLC converter experiences a short-circuit fault is dynamically drawn. The plurality of operating modes include: a first mode, a second mode, a third mode, and a fourth mode; the step of drawing the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression includes: Based on the trajectory variable expression, the centers of the first mode and the second mode at the initial moment are determined respectively. The circular arc trajectories of the first mode and the second mode are drawn according to the different centers, and the elliptical arc trajectories corresponding to the third mode and the fourth mode are drawn. The contraction of the two-dimensional steady-state trajectory corresponding to each operating mode is analyzed at different times during the soft start of the CLLC converter. The dynamic plotting of the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault in the CLLC converter includes: Analyze the changes in the center and radius of the trajectories corresponding to the first and second modes after a short-circuit fault occurs; Based on the changes in the center of the circle, the changes in the trajectory radius, and the trajectories of the first and second modes at the initial moment, the expanded range of the short-circuit transient trajectories corresponding to the first and second modes is determined, respectively. The time-domain equation of the first mode P is: ; The time-domain equation for the second mode N is: ; The time-domain equation for the third mode Z0 is: ; The time-domain equation for the fourth mode Z is: ; in, , , and Let represent the undetermined coefficients of the P-mode, , , and The undetermined coefficients of the mode, , , and They are The undetermined coefficients for the modal and Z-mode, M is the voltage gain, and the calculation methods for other variables are as follows: , , , .

2. The state trajectory analysis method according to claim 1, characterized in that, The operational mode analysis of the time-domain operation of the CLLC converter during soft-start under constant frequency and constant duty cycle control includes: Based on the structure of the resonant cavity and the direction of the resonant current, the working process of the CLLC converter under fixed duty cycle control is divided into the aforementioned multiple working modes; Construct the equivalent circuit diagram corresponding to each of the aforementioned operating modes; Based on each equivalent circuit diagram, construct the corresponding time-domain equation set for the operating mode; Taking into account the continuity of voltage and current, the symmetry of circuit operation, and the duration of each operating mode, boundary conditions are set for solving the time-domain equations under the multiple operating modes.

3. The state trajectory analysis method according to claim 2, characterized in that, The time-domain equations for each operating mode include: expressions for the primary resonant current, secondary resonant current, primary resonant voltage, and secondary resonant voltage of the CLLC converter.

4. The state trajectory analysis method according to claim 1, characterized in that, After dynamically plotting the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in the CLLC converter, the method further includes: The time-domain model of the CLLC converter is built in the simulation analysis application using the working mode method, and the operating parameters of the CLLC converter are set. Based on the obtained simulation analysis data, the state trajectory simulation results of the CLLC converter soft start process are obtained by normalization. The simulation results show the contraction and transient change process of the state trajectory.

5. The state trajectory analysis method according to claim 1, characterized in that, After dynamically plotting the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in the CLLC converter, the method further includes: Build an experimental prototype of the CLLC converter and set its operating parameters; The short-circuit fault moment after soft start is set on the introduced time axis, and the three-dimensional state trajectory of short-circuit protection during the converter startup process is dynamically generated based on the obtained experimental waveforms.

6. A state trajectory analysis system for short-circuit protection problems in CLLC converters, characterized in that, include: The analysis module is used to perform operating mode analysis on the time-domain operation of the CLLC converter during the soft start process under constant frequency and constant duty cycle control, and obtain the time-domain equations of the CLLC converter under multiple operating modes. The sorting module is used to sort out the time-domain equations under the multiple working modes, and add the resonant voltage and resonant current of different sides in each time-domain equation as trajectory variables to obtain the trajectory variable expression; The first plotting module is used to plot the two-dimensional steady-state trajectory of the CLLC converter at different times, with the sum of the resonant voltages as the horizontal axis and the sum of the resonant currents as the vertical axis, according to the trajectory variable expression. The multiple operating modes include a first mode, a second mode, a third mode, and a fourth mode. According to the trajectory variable expression, the center of the first mode and the second mode is determined at the initial time, and the circular arc trajectories of the first mode and the second mode are plotted according to different center points. The elliptical arc trajectories corresponding to the third mode and the fourth mode are also plotted. The contraction of the two-dimensional steady-state trajectory corresponding to each operating mode is analyzed at different times when the CLLC converter is soft-started. The second drawing module is used to dynamically draw the short-circuit transient trajectory corresponding to each operating mode after a short-circuit fault occurs in the CLLC converter, based on the drawing rules of the two-dimensional steady-state trajectory. Specifically, it analyzes the changes in the center and radius of the trajectories corresponding to the first and second modes after the short-circuit fault. Combining the center changes, the radius changes, and the trajectories of the first and second modes at the initial time, it determines the expanded range of the short-circuit transient trajectories corresponding to the first and second modes, respectively. The time-domain equation of the first mode P is: ; The time-domain equation for the second mode N is: ; The time-domain equation for the third mode Z0 is: ; The time-domain equation for the fourth mode Z is: ; in, , , and Let represent the undetermined coefficients of the P-mode, , , and The undetermined coefficients of the mode, , , and They are The undetermined coefficients for the modal and Z-mode, M is the voltage gain, and the calculation methods for other variables are as follows: , , , .

7. The state trajectory analysis system according to claim 6, characterized in that, The analysis module is specifically used for: Based on the structure of the resonant cavity and the direction of the resonant current, the working process of the CLLC converter under fixed duty cycle control is divided into the aforementioned multiple working modes; Construct the equivalent circuit diagram corresponding to each of the aforementioned operating modes; Based on each equivalent circuit diagram, construct the corresponding time-domain equation set for the operating mode; Taking into account the continuity of voltage and current, the symmetry of circuit operation, and the duration of each operating mode, boundary conditions are set for solving the time-domain equations under the multiple operating modes.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the state trajectory analysis method for short-circuit protection problem of CLLC converter as described in any one of claims 1-5.

Images