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

Abstract

The invention provides a state trajectory analysis method for a short-circuit protection problem of a CLLC converter, and the method comprises the steps: carrying out the working mode analysis of a time-domain working process of the CLLC converter in a soft start process under the control of a constant frequency and a constant duty ratio, and obtaining a time-domain equation set in a plurality of working modes; respectively adding the resonance voltage and the resonance current of different sides in each time domain equation set to serve as trajectory variables; taking the sum value of the resonance voltage as a horizontal axis and the sum value of the resonance current as a longitudinal axis, and drawing two-dimensional steady-state tracks of the CLLC converter at different moments according to a track variable expression; and based on the drawing rule of the two-dimensional steady-state track, dynamically drawing a short-circuit transient track corresponding to each working mode after the CLLC converter has a short-circuit fault. According to the method, the state trajectory model of the short-circuit transient state of the CLLC converter is established based on working modal analysis, a time axis is introduced, the three-dimensional state trajectory of short-circuit protection in the starting process is dynamically generated, and the accuracy and convenience of analysis are improved.

Description

Technical Field

[0001] The present application relates to the technical field of resonant converter short-circuit protection, and in particular to a state trajectory analysis method for a CLLC converter short-circuit protection problem. Background Art

[0002] The bidirectional full-bridge (Capacitor-Inductor-Inductor-Capacitor, CLLC for short) resonant converter is a high-frequency and high-efficiency isolated bidirectional DC / DC converter. Due to its outstanding soft switching characteristics and excellent bidirectional power flow performance, the CLLC converter has gradually attracted people's attention and has been applied to scenarios such as vehicle-to-grid interactive systems (V2G), battery energy storage systems (BES) and electric aircraft. In addition to efficiency, reliability is also an important evaluation indicator of the CLLC converter, among which short-circuit fault protection is a key link in reliability research.

[0003] When performing short-circuit fault protection for CLLC converters in related technologies, there is a lack of effective methods for modeling and analyzing the short-circuit protection process, resulting in the CLLC converter short-circuit protection method in related technologies usually using fundamental wave analysis from the perspective of equivalent gain. However, the converter equivalent gain model established in this way only considers the fundamental wave component, so the resulting model is not accurate when analyzing actual problems, which may affect the short-circuit protection results of the CLLC converter.

[0004] Therefore, how to analyze the short-circuit protection process of the CLLC converter through a simple and accurate analysis method has become a problem that needs to be solved urgently. Summary of the invention

[0005] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0006] To this end, the first purpose of the present application is to propose a state trajectory analysis method for the short-circuit protection problem of a CLLC converter. This method establishes a state trajectory model of the short-circuit transient of the CLLC converter based on working modal analysis, and analyzes the transient behavior of the converter after the short-circuit process through the dynamic changes of the trajectory, thereby improving the accuracy and convenience of the short-circuit protection process analysis.

[0007] The second object of the present application is to propose a state trajectory analysis system for the short-circuit protection problem of a CLLC converter;

[0008] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0009] To achieve the above object, a first aspect of the present application is to propose a state trajectory analysis method for a CLLC converter short-circuit protection problem, the method comprising the following steps:

[0010] Performing a working modal analysis on the time domain working process of the CLLC converter during the soft start process under constant frequency and constant duty cycle control to obtain a time domain equation group of the CLLC converter under multiple working modes;

[0011] Arrange the time domain equations under the multiple working modes, and add the resonant voltages and resonant currents of different sides in each of the time domain equations as trajectory variables to obtain trajectory variable expressions;

[0012] Taking the sum of the resonant voltage as the horizontal axis and the sum of the resonant current as the vertical axis, plotting the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression;

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

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

[0015] Optionally, in one embodiment of the present application, the time domain equation group under each of the working modes includes: an expression of the primary resonant current, an expression of the secondary resonant current, an expression of the primary resonant voltage and an expression of the secondary resonant voltage of the CLLC converter.

[0016] Optionally, in one embodiment of the present application, the multiple working modes include: a first mode, a second mode, a third mode and a fourth mode; drawing the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression includes: determining the centers of the first mode and the second mode at the initial time respectively according to the trajectory variable expression, drawing the circular arc trajectories of the first mode and the second mode according to different centers, and drawing the elliptical arc trajectories corresponding to the third mode and the fourth mode; analyzing the contraction status of the two-dimensional steady-state trajectory corresponding to each of the working modes at different times during the soft start of the CLLC converter.

[0017] Optionally, in one embodiment of the present application, the dynamic drawing of the short-circuit transient trajectory corresponding to each of the working modes after a short-circuit fault occurs in the CLLC converter includes: analyzing the change in the center of the circle and the change in the trajectory radius of the trajectories corresponding to the first mode and the second mode after the short-circuit fault occurs; combining the change in the center of the circle, the change in the trajectory radius, and the trajectories of the first mode and the second mode at the initial moment, respectively determining the expansion range of the short-circuit transient trajectories corresponding to the first mode and the second mode.

[0018] Optionally, in one embodiment of the present application, after dynamically drawing the short-circuit transient trajectory corresponding to each of the working modes after a short-circuit fault occurs in the CLLC converter, it also includes: building a time domain model of the CLLC converter in a simulation analysis application through a working mode method, and setting the working parameters of the CLLC converter; according to the obtained simulation analysis data, obtaining a state trajectory simulation result during the soft start process of the CLLC converter through a normalized method, wherein the simulation result shows the contraction and transient change process of the state trajectory.

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

[0020] To achieve the above-mentioned purpose, the second aspect of the present application further proposes a state trajectory analysis system for the short-circuit protection problem of a CLLC converter, comprising the following modules:

[0021] An analysis module is used to perform a 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 a time domain equation group of the CLLC converter under multiple working modes;

[0022] A sorting module, used for sorting the time domain equations under the multiple working modes, and adding the resonant voltages and resonant currents of different sides in each of the time domain equations as trajectory variables to obtain trajectory variable expressions;

[0023] A first drawing module is used to draw the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression, using the sum of the resonant voltage as the horizontal axis and the sum of the resonant current as the vertical axis;

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

[0025] In order to implement the above-mentioned embodiments, the third aspect embodiment of the present application also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the state trajectory analysis method for the short-circuit protection problem of the CLLC converter in the above-mentioned first aspect embodiment is implemented.

[0026] The technical solution provided by the embodiment of the present application brings at least the following beneficial effects: the present application models the CLLC converter based on the working modal analysis method for the working condition of a short-circuit fault occurring during the constant frequency and constant duty cycle soft start process of the CLLC converter, constructs a new state variable using the resonant current and resonant voltage to draw the state trajectory of the steady state, and then gives the transient trajectory change of the short-circuit protection process, and constructs a state trajectory model of the short-circuit transient. Thus, trajectory analysis can be used to reflect the converter working process, and the transient behavior of the CLLC converter after the short-circuit process can be reflected by the dynamic change of the trajectory, simplifying the complex and abstract mathematical equation group operation into the drawing of the trajectory. As a result, the present application improves the accuracy, comprehensiveness and convenience of the analysis of the short-circuit protection process of the CLLC converter, provides a basis for the subsequent related protection control design, and is conducive to ensuring the safe and stable operation of the CLLC converter.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 1 A flow chart of a state trajectory analysis method for a CLLC converter short-circuit protection problem proposed in an embodiment of the present application;

[0030] Figure 2 A topological diagram of a CLLC converter proposed in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of multiple operating modes of a CLLC converter proposed in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of an equivalent circuit of a different working mode proposed in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of a boundary condition proposed in an embodiment of the present application;

[0034] Figure 6 A schematic diagram of a state trajectory proposed in an embodiment of the present application;

[0035] Figure 7 A schematic diagram of another state trajectory proposed in an embodiment of the present application;

[0036] Figure 8 A schematic diagram of a transient trajectory after a short circuit fault proposed in an embodiment of the present application;

[0037] Fig. 9 A schematic diagram of a simulation result of a short-circuit protection during startup proposed in an embodiment of the present application;

[0038] Fig.10 A schematic diagram of an experimental result proposed in an embodiment of the present application;

[0039] Fig.11 A schematic diagram of another experimental result proposed in an embodiment of the present application;

[0040] Fig.12 A structural schematic diagram of a state trajectory analysis system for a CLLC converter short-circuit protection problem proposed in an embodiment of the present application. DETAILED DESCRIPTION

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

[0042] It should be noted that, when performing the short-circuit protection analysis of the CLLC converter in the relevant embodiments, the fundamental wave analysis method is generally used to establish the equivalent gain model of the converter in combination with the switching frequency and duty cycle of the primary switch tube of the CLLC converter. This method only considers the fundamental wave component, so the resulting model is not accurate when analyzing practical problems. On this basis, in other relevant embodiments, there is also a time domain working model of the CLLC converter established by using the working modal analysis method. The model can accurately characterize the actual working state of the converter, but the model 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 on the basis of working mode analysis. Since the working mode of the CLLC converter is relatively complex, there is no state trajectory model. In addition, the short-circuit process of the CLLC converter includes transient changes, and there is no accurate modeling method at present.

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

[0045] A state trajectory analysis method and system for the short-circuit protection problem of a CLLC converter proposed in an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0046] Figure 1 A flow chart of a state trajectory analysis method for a CLLC converter short-circuit protection problem proposed in an embodiment of the present application is shown in FIG. Figure 1 As shown, the method comprises the following steps:

[0047] Step S101, performing a working modal 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 obtaining a time domain equation group of the CLLC converter under multiple working modes.

[0048] Specifically, the present application is aimed at the condition that a short circuit fault occurs in a CLLC converter during a constant frequency and constant duty cycle soft start process, and establishes a state trajectory model of a short circuit transient based on operating modal analysis. To facilitate the description of the subsequent analysis process, the CLLC converter involved in the present application is first 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 switch tubes, S5 to S8 are secondary switch tubes, and C r1 is the primary resonant capacitor, L r1 is the primary resonant inductance, C r2is the secondary resonant capacitor, L r2 is the secondary resonant inductor, L m is the magnetizing inductance, the transformer turns ratio is n:1, and the primary resonant current i p , secondary side resonant current i s , excitation current i Lm The positive direction of the voltage at each end is shown in the figure. The voltage on the primary resonant capacitor is the primary resonant voltage, and the voltage on the secondary resonant capacitor is the secondary resonant voltage.

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

[0051] In one embodiment of the present application, a working mode analysis is performed on the time domain working process of the CLLC converter during the soft start process under constant frequency and constant duty cycle control, including the following steps: first, according to 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 multiple working modes; then, an equivalent circuit diagram corresponding to each working mode is constructed; then, according to each equivalent circuit diagram, a group of time domain equations under the corresponding working mode is constructed respectively; finally, in combination with the continuity of voltage and current, the symmetry of circuit operation and the duration of each working mode, boundary conditions for solving the time domain equations under multiple working modes are set.

[0052] Specifically, in this embodiment, analyzing the time domain working process by the working modal method includes the following key steps:

[0053] The first step is to distinguish the working modes. The working process of the CLLC converter under fixed duty cycle control can be composed of different working modes. In this embodiment, according to Figure 2 The structure of the resonant cavity and the direction of the resonant current divide the working modes into multiple modes, such as Figure 3 As shown, different working modes are named as the first mode ( Figure 3 The first mode corresponds to the P mode), the second mode (N mode), the third mode (Z0 mode) and the fourth mode (Z mode). The working modes of the converter are consistent in the positive and negative half cycles. In the embodiment of the present application, the following analysis is carried out around the positive half cycle. Figure 3 The components that do not work in this mode are displayed in a faded grayscale.

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

[0055] The third step is to derive the time domain equation. Figure 4 The LCC converter equivalent circuits under different working modes given can be used to list time domain equations of different modes. In this embodiment, the time domain equations under each working mode include: the expression of the primary resonant current, the expression of the secondary resonant current, the expression of the primary resonant voltage and the expression of the secondary resonant voltage of the CLLC converter. The time domain equations of P mode, N mode, Z0 mode and Z mode are specifically listed in Table 1 below.

[0056] Table 1 Time domain equations for different modes

[0057]

[0058] Among them, P1, P2, P3 and P4 represent the undetermined coefficients of P mode, N1, N2, N3 and N4 represent the undetermined coefficients of N mode, and Z 01 , Z 02 , Z1 and Z2 are the unknown coefficients of Z0 mode and Z mode respectively, M is the voltage gain, and the calculation method of other variables is as follows: φ=2πf r t, k=L m / L r1 , The meaning of each parameter is the same as Figure 2 The meanings are consistent in this application, and the parameters with given meanings will not be repeated in the following.

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

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

[0061] Step S102, sorting out the time domain equations under multiple working modes, and adding the resonant voltages and resonant currents of different sides in each time domain equation group as trajectory variables to obtain trajectory variable expressions.

[0062] Specifically, based on the previous step, the state trajectory of the short-circuit protection of the CLLC converter proposed in this application is analyzed. In this step, the modal equation is first sorted out. Specifically, the time domain equations of the P mode, N mode, Z0 mode and Z mode can be obtained by applying the above working modal analysis method to model the time domain working process of the CLLC converter under fixed duty cycle control, and the i of each mode is respectively p and i s Add, u cr1 and u cr2 Add them as new trajectory variables, and then we can get the trajectory variable expression expressed 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 voltage as the horizontal axis and the sum of the resonant current as the vertical axis, and drawing 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 drawn. cr1 and u cr2 The sum of the added values ​​is used as the horizontal axis, i p and i s The added sum is used 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 State trajectory shapes of different modes

[0068]

[0069] In one embodiment of the present application, a two-dimensional steady-state trajectory of the CLLC converter at different times is drawn according to a trajectory variable expression, including: determining the centers of the first mode and the second mode at the initial time respectively according to the trajectory variable expression, drawing circular arc trajectories of the first mode and the second mode according to different centers, and drawing elliptical arc trajectories corresponding to the third mode and the fourth mode; analyzing the contraction status of the two-dimensional steady-state trajectory corresponding to each working mode at different times of soft starting of the CLLC converter.

[0070] Specifically, in this embodiment, the above Table 2 is obtained according to the trajectory variable expression, and then the trajectory drawing method is determined according to Table 2. The working state of the converter can be vividly represented by the trajectory. The following takes the trajectory when M=0 and M=M1 as an example to specifically introduce the composition and drawing principle of the trajectory.

[0071] As an example, Figure 6 The state trajectory when M=0 is shown, where the AE segment 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 drawings of this application, and in order to facilitate comparison of the changes in the trajectories, Figures 6 to 8 In the example, M is the trajectory at other moments and is displayed in a faded form.

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

[0073] Further, combined with Figure 7 It can be seen from the trajectory when M=M1 that as the startup proceeds, the trajectory shows a shrinking trend. Since the embodiment of the present application adopts a control method with a fixed duty cycle, the time corresponding to the P mode remains unchanged, which is reflected in the trajectory, that is, the center angle corresponding to the AB segment trajectory remains unchanged. It can be seen that the trajectory is not proportionally shrunk but rotationally shrunk, which is reflected in the actual operation of the converter as the Z0 mode and Z mode time become longer. In addition, since the state trajectory is drawn by the resonant cavity parameters, its area reflects the energy transmitted by the converter to a certain extent, and the contraction of the trajectory corresponds to the energy limitation characteristics of the converter during the startup process.

[0074] Step S104, based on the drawing rule of the two-dimensional steady-state trajectory, dynamically draw the short-circuit transient trajectory corresponding to each working mode after the short-circuit fault occurs in the CLLC converter.

[0075] Specifically, the short-circuit transient trajectory is drawn after the short-circuit fault occurs in the CLLC converter. Based on the law reflected in the process of drawing the steady-state trajectory in the above step S103, the state trajectory of the short-circuit protection transient process can be drawn.

[0076] In one embodiment of the present application, a short-circuit transient trajectory corresponding to each working mode after a short-circuit fault occurs in a CLLC converter is dynamically drawn, including: analyzing the change in the center of the circle and the change in the trajectory radius of the trajectories corresponding to the first mode and the second mode after the short-circuit fault occurs; combining the change in the center of the circle, the change in the trajectory radius, and the trajectories of the first mode and the second mode at the initial moment, respectively determining the expansion range of the short-circuit transient trajectories corresponding to the first mode and the second mode.

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

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

[0079] For trajectory BC: Trajectory BC reflects the trajectories of N mode, Z0 mode and Z mode, and mainly considers the change of N mode trajectory. Similar to P mode, the center of N mode trajectory moves to (-1,0), but because 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, which 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 be further expanded, but will not exceed the trajectory of M=0.

[0081] Therefore, the embodiment of the present application utilizes the above-mentioned state trajectory analysis method to intuitively characterize the short-circuit protection process. Since the trajectory after the fault occurs will be limited to the trajectory of M=0, that is, the voltage and current in the converter after the short circuit occurs will not exceed the state at the beginning of startup, 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 effect of the state trajectory analysis method of the present application, two specific verification embodiments in actual applications are described below.

[0083] In one embodiment of the present application, after the above-mentioned dynamic drawing of the short-circuit transient trajectory corresponding to each working mode after a short-circuit fault occurs in the CLLC converter, it also includes: building a time domain model of the CLLC converter in a simulation analysis application through a working mode method, and setting the working parameters of the CLLC converter; according to the obtained simulation analysis data, obtaining the state trajectory simulation results of the CLLC converter during the soft start process through normalization, wherein the simulation results show the contraction and transient change process of the state trajectory.

[0084] Specifically, in this embodiment, simulation verification results are provided for the state trajectory analysis method proposed in this application. In the simulation analysis software, the time domain model of the CLLC converter is built using the working mode method in step S101 above, and the CLLC converter parameters are set in the software as follows: 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, set the switching frequency fs s =f r =145.9kHz. Then run the simulation program according to the setting method, and use the normalized method to obtain the state trajectory of the short-circuit protection during the startup process as follows based on the obtained simulation data Fig. 9 As shown. Fig. 9 The simulation results shown show that the state trajectory analysis method provided in the present application accurately describes the working process of the converter through the contraction and transient changes of the trajectory.

[0085] In one embodiment of the present application, after the above-mentioned dynamic drawing of the short-circuit transient trajectory corresponding to each working mode after a short-circuit fault occurs in the CLLC converter, it also includes: building an experimental prototype of the CLLC converter and setting the working parameters of the CLLC converter; setting the short-circuit fault moment after the start of soft start on the introduced time axis, and dynamically generating a three-dimensional state trajectory of the short-circuit protection during the converter startup process according to the acquired experimental waveform, that is, constructing a three-dimensional state trajectory model of the CLLC converter that reflects time changes.

[0086] Specifically, in this embodiment, an experimental verification result is provided 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 follows: r1 =Lr2 =35uH,C r1 =C r2 =34nF,L m =386uH, transformer turns ratio n=1, and build an experimental prototype. The experimental prototype includes: short-circuit switch, control board, auxiliary power supply, input side, primary H-bridge, secondary H-bridge, output side, transformer and resonant cavity. At 13ms after starting the experimental prototype, a short-circuit fault is applied to the output side. The experimental waveform obtained is as follows Fig.10 and Fig.11 As shown, by introducing the timeline, Fig.11 The three-dimensional state trajectory model reflecting time variation is shown, through which the three-dimensional state trajectory of short-circuit protection during the converter startup process can be determined. It can be seen that the state trajectory analysis method of the present application can accurately reflect the actual working process of the converter.

[0087] Therefore, this application first establishes a time domain working model of the CLLC converter under constant frequency and constant duty cycle control; then draws the two-dimensional state trajectory of the CLLC converter by adding the resonant voltage and the resonant current; then, for short-circuit faults, a dynamic drawing method of the state trajectory is proposed; finally, the time axis is introduced to construct a three-dimensional state trajectory model that reflects time changes.

[0088] In summary, the state trajectory analysis method for the short-circuit protection problem of the CLLC converter in the embodiment of the present application is aimed at the working condition that the short-circuit fault occurs in the constant frequency constant duty cycle soft start process of the CLLC converter. The CLLC converter is modeled based on the working modal analysis method, and a new state variable is constructed using the resonant current and the resonant voltage to draw the state trajectory of the steady state, and then the transient trajectory change of the short-circuit protection process is given, and the state trajectory model of the short-circuit transient is constructed. Thus, the trajectory analysis can be used to reflect the converter working process, and the transient behavior of the CLLC converter after the short-circuit process is reflected by the dynamic change of the trajectory, and the complex and abstract mathematical equation group operation is simplified to the drawing of the trajectory. As a result, the method improves the accuracy, comprehensiveness and convenience of the analysis of the short-circuit protection process of the CLLC converter, provides a basis for the subsequent related protection control design, and is conducive to ensuring the safe and stable operation of the CLLC converter.

[0089] In order to implement the above embodiment, the present application also proposes a state trajectory analysis system for the short-circuit protection problem of a CLLC converter. Fig.12 A structural diagram of a state trajectory analysis system for a CLLC converter short-circuit protection problem proposed in an embodiment of the present application is shown in FIG. Fig.12 As shown, the system includes: an analysis module 100 , a sorting module 200 , a first drawing module 300 and a second drawing module 400 .

[0090] The analysis module 100 is used to perform a 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 a time domain equation group of the CLLC converter under multiple working modes.

[0091] The sorting module 200 is used to sort the time domain equations under multiple working modes, and add the resonant voltages and resonant currents of different sides in each time domain equation group as trajectory variables to obtain trajectory variable expressions.

[0092] The first drawing module 300 is used to draw the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression, using the sum of the resonant voltage as the horizontal axis and the sum of the resonant current as the vertical axis.

[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 rule of the two-dimensional steady-state trajectory.

[0094] Optionally, in one embodiment of the present application, the analysis module 100 is specifically used to: divide the working process of the CLLC converter under fixed duty cycle control into the 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; according to each equivalent circuit diagram, respectively construct a group of time domain equations under the corresponding working mode; and set boundary conditions for solving the time domain equations under multiple working modes in combination with 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 aforementioned explanation of the embodiment of the state trajectory analysis method for the short-circuit protection problem of the CLLC converter is also applicable to the system of this embodiment, the implementation principle is the same, and the functions of each module are not repeated here.

[0096] In summary, the fault detection system of the real-time clock RTC of the embodiment of the present application can monitor the RTC timestamp in real time through relevant software algorithms to detect the accuracy of the device chip RTC without adding other external hardware devices and without relying on external communication, and can accurately detect various types of faults that may occur in the RTC. Therefore, on the one hand, the system reduces the cost of RTC detection, saves external communication steps, and reduces the complexity of detection. On the other hand, it can detect a variety of faults and specifically locate the type of fault currently occurring in the RTC, improve the accuracy and reliability of the detection results, and refine the detection results. In addition, the system can also realize the RTC automatic calibration function, report the fault after identifying the RTC fault, and calibrate the abnormal RTC clock signal at any time according to the RTC detection result. The calibration method is relatively simple, which is conducive to ensuring the normal and stable operation of the RTC function.

[0097] In order to implement the above-mentioned embodiments, the present application also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, a state trajectory analysis method for the short-circuit protection problem of the CLLC converter is implemented as described in any one of the above-mentioned first aspect embodiments.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0099] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0100] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

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

[0102] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0103] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0104] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0105] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A state trajectory analysis method for the short-circuit protection problem of a CLLC converter, characterized in that: The following steps are involved: Performing a working modal analysis on the time domain working process of the CLLC converter during the soft start process under constant frequency and constant duty cycle control to obtain a time domain equation group of the CLLC converter under multiple working modes; Arrange the time domain equations under the multiple working modes, and add the resonant voltages and resonant currents of different sides in each of the time domain equations as trajectory variables to obtain trajectory variable expressions; Taking the sum of the resonant voltage as the horizontal axis and the sum of the resonant current as the vertical axis, plotting the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression; Based on the drawing rule of the two-dimensional steady-state trajectory, the short-circuit transient trajectory corresponding to each of the working modes after a short-circuit fault occurs in the CLLC converter is dynamically drawn.

2. The state trajectory analysis method according to claim 1, characterized in that: The operating modal analysis of the time domain operating process of the CLLC converter during the soft start process under constant frequency and constant duty cycle control includes: According to the structure of the resonant cavity and the direction of the resonant current, the working process of the CLLC converter under the fixed duty cycle control is divided into the multiple working modes; Constructing an equivalent circuit diagram corresponding to each of the working modes; According to each of the equivalent circuit diagrams, respectively construct a corresponding time domain equation group under the working mode; In combination with the continuity of voltage and current, the symmetry of circuit operation, and the duration of each of the working modes, boundary conditions for solving the time domain equations under the multiple working modes are set.

3. The state trajectory analysis method according to claim 2, characterized in that: The time domain equation group under each working mode includes: an expression of the primary resonant current, an expression of the secondary resonant current, an expression of the primary resonant voltage and an expression of the secondary resonant voltage of the CLLC converter.

4. The state trajectory analysis method according to claim 1, characterized in that: The multiple working modes include: a first mode, a second mode, a third mode and a fourth mode; the two-dimensional steady-state trajectory of the CLLC converter at different times is drawn according to the trajectory variable expression, including: According to the trajectory variable expression, the centers of the first mode and the second mode at the initial moment are determined respectively, and the arc trajectories of the first mode and the second mode are drawn according to different centers, and the elliptical arc trajectories corresponding to the third mode and the fourth mode are drawn; The contraction status of the two-dimensional steady-state trajectory corresponding to each working mode at different moments of the soft start of the CLLC converter is analyzed.

5. The state trajectory analysis method according to claim 4, characterized in that: The dynamically drawing of the short-circuit transient trajectory corresponding to each of the working modes after a short-circuit fault occurs in the CLLC converter includes: Analyze the change of the center and the radius of the trajectory corresponding to the first mode and the second mode after the short circuit fault occurs; Based on the change of the circle center, the change of the trajectory radius, and the trajectories of the first mode and the second mode at the initial moment, the expansion ranges of the short-circuit transient trajectories corresponding to the first mode and the second mode are determined respectively.

6. The state trajectory analysis method according to claim 1, characterized in that: After dynamically drawing the short-circuit transient trajectory corresponding to each of the working modes 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 through the working mode method, and the working parameters of the CLLC converter are set; According to the obtained simulation analysis data, the state trajectory simulation result of the CLLC converter during the soft start process is obtained by normalization, wherein the simulation result shows the contraction and transient change process of the state trajectory.

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

8. A state trajectory analysis system for the short-circuit protection problem of a CLLC converter, characterized in that: include: An analysis module is used to perform a 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 a time domain equation group of the CLLC converter under multiple working modes; A sorting module, used for sorting the time domain equations under the multiple working modes, and adding the resonant voltages and resonant currents of different sides in each of the time domain equations as trajectory variables to obtain trajectory variable expressions; A first drawing module is used to draw the two-dimensional steady-state trajectory of the CLLC converter at different times according to the trajectory variable expression, using the sum of the resonant voltage as the horizontal axis and the sum of the resonant current as the vertical axis; The second drawing module is used to dynamically draw the short-circuit transient trajectory corresponding to each of the working modes after a short-circuit fault occurs in the CLLC converter based on the drawing rule of the two-dimensional steady-state trajectory.

9. The state trajectory analysis system according to claim 8, characterized in that: The analysis module is specifically used for: According to the structure of the resonant cavity and the direction of the resonant current, the working process of the CLLC converter under the fixed duty cycle control is divided into the multiple working modes; Constructing an equivalent circuit diagram corresponding to each of the working modes; According to each of the equivalent circuit diagrams, respectively construct a corresponding time domain equation group under the working mode; In combination with the continuity of voltage and current, the symmetry of circuit operation, and the duration of each of the working modes, boundary conditions for solving the time domain equations under the multiple working modes are set.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the state trajectory analysis method for the short-circuit protection problem of a CLLC converter is implemented as described in any one of claims 1 to 7.

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