Method and device for optimizing backflow power of DAB converter based on superspiral sliding mode control

Abstract

The invention relates to the technical field of dual active bridge converters, in particular to a DAB converter backflow power optimization method and device based on superspiral sliding mode control, and the method comprises the steps: constructing backflow power functions and transmission power functions of four working modes under dual phase shift control, carrying out the derivation of the backflow power function of each mode, and carrying out the optimization of the backflow power of the DAB converter. And the optimal backflow power path is determined and calculated, and the optimal backflow power path is optimized according to the junction point with the actual optimal backflow power path, so that the accuracy of the backflow power path is ensured. Under the fixed transmission power, according to the optimized backflow power path, the phase shift combination with the minimum backflow power is selected, and the backflow power of the DAB converter is remarkably reduced. According to the method, dual phase shift control is adopted, control signals do not need to be switched during two-way energy transmission, the power adjusting range is wider, and the control difficulty is reduced. In addition, the stability and robustness of the system are further enhanced by introducing a super-spiral sliding mode control strategy to dynamically adjust and optimize bridge outward shifting.

Description

Technical Field

[0001] The present application relates to the technical field of dual active bridge converters, and in particular to a method and device for optimizing the reflux power of a DAB converter based on super spiral sliding mode control. Background Art

[0002] Dual Active Bridge (DAB) DC-DC converters have the characteristics of bidirectional power flow, electrical isolation, high power density and easy zero voltage switching, and have gradually become the mainstream equipment in the construction of DC microgrids. However, the backflow power problem has always been one of the key factors affecting the efficiency and performance of DAB converters. Backflow power not only increases the energy loss of the system, but may also have an adverse effect on the stability and reliability of the power grid.

[0003] In order to effectively control the reflux power in the DAB converter, the existing patent with publication number CN109256955A provides a reflux power suppression and analysis method for a dual active bridge based on modal analysis. By adopting an extended phase shift (EPS) control method, the phase shift duty cycle and the timing of the primary switch drive signal are changed, and a freewheeling mode is added during the DAB modal evolution process to provide a freewheeling channel for the inductor to unload energy, thereby avoiding the freewheeling current from flowing to the input power supply and reducing or eliminating the reflux power. The extended phase shift control method adopted by this method introduces an additional internal phase shift angle in the secondary bridge of the transformer on the basis of the single phase shift (SPS) control, which can effectively reduce the reflux power and current stress of the transformer. However, in the process of changing the direction of power transmission by EPS control, the operating conditions often change, so that the original control parameters may no longer be applicable and need to be readjusted and optimized, which greatly increases the control difficulty of the system. Summary of the invention

[0004] Based on this, it is necessary to provide a DAB converter backflow power optimization method and device based on super-helical sliding mode control to address the problem that the existing backflow power suppression methods are relatively complicated.

[0005] In a first aspect, the present application provides a DAB converter reflux power optimization method based on super-helical sliding mode control, comprising:

[0006] Step S1, dividing the working modes of the DAB converter under the dual phase shift control mode into four types according to the size relationship between the inner bridge shift phase and the outer bridge shift phase, and constructing the return power function and the transmission power function of the four working modes;

[0007] Step S2, respectively deriving the return power functions of the four working modes to obtain the calculated optimal return power path of each working mode;

[0008] Step S3, calculating the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimizing the calculated optimal return power path according to the intersection point to obtain the calculated optimal return power path after optimization of each working mode;

[0009] Step S4, obtaining a shift ratio combination with the minimum return power under a condition of a certain transmission power according to the calculated optimal return power path after optimization of each working mode;

[0010] Step S5, defining the input and sliding surface of the super-helical sliding mode controller;

[0011] Step S6, obtaining an optimized bridge outer shift ratio according to the input and sliding surface of the super-helical sliding mode controller, the inner bridge shift ratio in the shift ratio combination with the minimum return power, and the return power function and the transmission power function in the four working modes.

[0012] In one embodiment, the magnitude relationships between the bridge inward displacement ratio D1 and the bridge outward displacement ratio D2 in the four working modes are respectively:

[0013] Mode a, 0<D1, D2<1, D1<D2, D1+D2≥1;

[0014] Mode b, 0<D1, D2<1, D1<D2, D1+D2<1;

[0015] Mode c, 0<D1, D2<1, D1≥D2, D1+D2<1;

[0016] Mode d, 0<D1, D2<1, D1≥D2, D1+D2≥1.

[0017] In one embodiment, for the four working modes of the DAB converter, the return power function and the transmission power function are constructed according to the following steps:

[0018] Step S11, obtaining the inductor current value of the DAB converter in one cycle;

[0019] Step S12, obtaining the return power and the transmission power according to the inductor current value and the port voltage of the H-bridge on the primary side of the transformer;

[0020] Step S13, normalizing the return power and the transmission power by taking the maximum value of the transmission power as the reference value for power normalization.

[0021] In one embodiment, the expressions of the return power function and the transmission power function of the four working modes after normalization are:

[0022]

[0023] Where P 1a represents the transmission power of mode a, P DPS-bf-a represents the return power of mode a, P 1b represents the transmission power of mode b, P DPS-bf-b represents the return power of mode b, P 1c represents the transmission power of mode c, P DPS-bf-c represents the return power of mode c, P 1d represents the transmission power of mode d, P DPS-bf-d represents the return power of mode d, and k represents the voltage transfer ratio.

[0024] In one embodiment, when the DAB converter operates in mode b, the expression of the inductor current value of the DAB converter in one cycle is:

[0025]

[0026] In the formula, i L is the inductor current, t0=0, t1=D1T hs , t2=D2T hs , t3=(D1+D2)T hs , T hs is the half switching period of the DAB converter, f s is the switching frequency, f s =1 / (2T hs ), L is the sum of the leakage inductance and auxiliary inductance of the transformer, n is the number of turns on the primary side of the transformer, u0 is the output side voltage, and k is the voltage transfer ratio;

[0027] The expressions of the return power function and transmission power function of mode b after normalization are:

[0028]

[0029] Where P 1b represents the transmission power of mode b, P DPS-bf-b Indicates the return power of mode b.

[0030] In one embodiment, step S2 comprises:

[0031] Step S21, deriving the return power function of mode b after normalization; the expression of the derivative result is:

[0032]

[0033] Step S22, setting the value of the derived return power function to 0, and obtaining the optimal return power path for mode b; the expression for calculating the optimal return power path for mode b is:

[0034]

[0035] Step S3 includes:

[0036] Step S31, let D1=D2, and obtain the intersection point between the calculated optimal return power path and the actual optimal return power path of mode b; the expression of the intersection point is:

[0037]

[0038] Where P′1 represents the transmission power of the junction point, and D′2 represents the bridge outward displacement ratio of the junction point;

[0039] Step S32, optimizing the calculated optimal return power path obtained in step S22 according to the intersection point, and obtaining the calculated optimal return power path after optimization of mode b; wherein, when When , the optimal return power path after optimization of mode b is:

[0040]

[0041] Where P1 represents the transmission power of the DAB converter.

[0042] In one embodiment, the shift ratio combination with the smallest return power and the return power corresponding to the shift ratio combination with the smallest return power include:

[0043] When 0≤P1<0.5, the working mode of the DAB converter is mode c, and the phase shift combination is The reflux power is 0.25(k-1) 2 P1k -1 ;

[0044] when When the DAB converter works in mode b, the shift phase combination is The return power is

[0045] when When , the working mode of DAB converter is mode b, and the shift phase combination is: The return power is: Wherein, P1 is the transmission power of the DAB converter.

[0046] In one embodiment, the input of the super-helical sliding mode controller and the sliding mode surface are expressed as:

[0047]

[0048] Where p represents the input of the super-helical sliding mode controller, L is the sum of the leakage inductance and auxiliary inductance of the transformer, and f s is the switching frequency, C o is the transformer output side support capacitor, n is the number of turns on the primary side of the transformer, u i is the voltage at the input side of the transformer, i o is the load current, k1 and k2 are both positive coefficients, sgn is the sign function, α and β are both positive parameters, e is the output voltage error, s is the sliding surface, represents the derivative of the sliding surface;

[0049] The sliding surface expression is: s = k1e + k2∫ (e) dt, and the output voltage error expression is: e = u o -u ref ,u o is the voltage at the output side of the transformer, u ref is the reference voltage.

[0050] In one embodiment, the expression of the optimized bridge outward displacement ratio is:

[0051]

[0052] Wherein, D1 is the bridge internal shift phase ratio in the shift phase ratio combination with the smallest reflux power in step S4.

[0053] In a second aspect, the present application provides a DAB converter reflux power optimization device based on super spiral sliding mode control, comprising:

[0054] The optimal return power path calculation module is used to divide the working modes of the DAB converter under the DPS control mode into four types according to the size relationship between the bridge inward shift ratio and the bridge outward shift ratio, and construct the return power function and transmission power function of the four working modes; respectively derive the return power function of the four working modes to obtain the calculated optimal return power path of each working mode;

[0055] The optimal return power path optimization module is used to calculate the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimize the calculated optimal return power path according to the intersection point to obtain the calculated optimal return power path after optimization of each working mode;

[0056] The shift-phase ratio combination and return power calculation module is used to calculate the optimal return power path after optimization of each working mode to obtain the shift-phase ratio combination with the minimum return power and the return power corresponding to the shift-phase ratio combination with the minimum return power under the condition of a certain transmission power;

[0057] The bridge outer shift phase optimization module is used to define the input and sliding surface of the super-helical sliding mode controller; the optimized bridge outer shift phase is obtained according to the input and sliding surface of the super-helical sliding mode controller, the bridge inner shift phase in the shift phase combination with the smallest reflux power, and the reflux power function and transmission power function in four working modes.

[0058] The above-mentioned DAB converter return power optimization method and device based on super-helical sliding mode control constructs the return power function and transmission power function of the DAB converter under the dual phase-shift control mode in four working modes, derives the return power function of each working mode to obtain the optimal return power path, and optimizes the intersection point with the actual optimal path to ensure the accuracy of the calculated optimal return power path. Then, under the condition of a certain transmission power, the phase shift ratio combination with the minimum return power is determined according to the calculated optimal return power path after optimization of each working mode, thereby significantly reducing the return power of the DAB converter. The DAB converter in this method is controlled by a dual phase-shift control method, and the dual phase-shift control does not need to switch the control signal in the case of bidirectional energy transmission, and the power adjustment range is wider, thereby reducing the control difficulty of the system; in addition, the method realizes dynamic adjustment and optimization of the bridge outer phase shift ratio by introducing the super-helical sliding mode control strategy, further improving the stability and robustness of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a structural schematic diagram of a DAB converter in one embodiment;

[0060] Figure 2 1 is a flow chart of a method for optimizing the reflux power of a DAB converter based on super-helical sliding mode control in one embodiment;

[0061] Figure 3 is a working waveform diagram of a DAB converter in a global mode in one embodiment;

[0062] Figure 4 is a normalized diagram of transmission power in a global mode of a DAB converter in one embodiment;

[0063] Figure 5 A schematic diagram of calculating the optimal return power path of DAB converter mode b in one embodiment;

[0064] Figure 6 is a structural block diagram of a DAB converter reflux power optimization device based on super-helical sliding mode control in one embodiment;

[0065] Figure 7 Schematic diagram of the structure of a DAB converter reflux power optimization system based on super-helical sliding mode control in one embodiment;

[0066] Figure 8 is a working waveform diagram of a DAB converter under light load conditions controlled by a conventional current stress optimization method in one embodiment;

[0067] Fig. 9 It is a working waveform diagram when a DAB converter under light load condition is controlled by using a DAB converter reflux power optimization method without adding super spiral sliding mode control in one embodiment;

[0068] Fig.10 is a working waveform diagram of a DAB converter under light load conditions when a DAB converter reflux power optimization method based on super spiral sliding mode control is used in one embodiment;

[0069] Fig.11 is a working waveform diagram of a DAB converter under medium load conditions controlled by a conventional current stress optimization method in one embodiment;

[0070] Fig.12 It is a working waveform diagram when a DAB converter under medium load condition is controlled by using a DAB converter reflux power optimization method without adding super spiral sliding mode control in one embodiment;

[0071] Fig.13 is a working waveform diagram of a DAB converter under medium load conditions when a DAB converter reflux power optimization method based on super spiral sliding mode control is used in one embodiment;

[0072] Fig.14 is a working waveform diagram of a DAB converter under heavy load conditions controlled by a conventional current stress optimization method in one embodiment;

[0073] Fig.15 It is a working waveform diagram when a DAB converter under heavy load condition is controlled by using a DAB converter reflux power optimization method without adding super spiral sliding mode control in one embodiment;

[0074] Fig.16 The figure is a working waveform diagram when a DAB converter under heavy load condition is controlled by using a DAB converter reflux power optimization method based on super spiral sliding mode control in an embodiment. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0076] The DAB converter reflux power optimization method based on super spiral sliding mode control provided in this application is used to control Figure 1 The DAB converter shown in the figure includes two identical full-bridge units, an auxiliary inductor L, a high-frequency transformer T, and an input-side support capacitor C. i And the output side support capacitor C o , and the two full-bridge units are connected through a high-frequency transformer. Among them, the full-bridge unit is composed of 4 identical power switching devices, the input side full bridge is represented by S1~S4, and the output side full bridge is represented by S5~S8. The primary and secondary side turns ratio of the high-frequency transformer is n:1, and the auxiliary inductance is the sum of the leakage inductance and the auxiliary inductance of the high-frequency transformer, u i is the input voltage, u o is the output voltage, v H1 is the terminal voltage of the H-bridge on the primary side of the transformer, v H2 is the terminal voltage of the H bridge on the secondary side of the transformer, i L is the inductor current, i o is the load current.

[0077] Embodiment 1

[0078] An embodiment of the present disclosure provides a DAB converter reflux power optimization method based on super spiral sliding mode control, such as Figure 2 As shown, the specific steps include:

[0079] Step S1, dividing the working modes of the DAB converter under the dual phase shift control mode into four types according to the size relationship between the inner bridge shift phase ratio and the outer bridge shift phase ratio, and constructing the return power function and the transmission power function of the four working modes.

[0080] Among them, dual-phase-shift control (DPS) is to increase the phase shift angle in the left and right bridges of the transformer at the same time, with two control degrees of freedom. In the case of bidirectional energy transmission, there is no need to switch the control signal, and the power adjustment range is wider. The phase shift ratio inside the bridge is the phase shift ratio between the two half-bridge arms inside the input side full-bridge unit or the output side full-bridge unit, denoted as D1, and the phase shift ratio outside the bridge is the phase shift ratio between the input side full-bridge unit and the output side full-bridge unit, denoted as D2.

[0081] Specifically, the working modes of the DAB converter under the DPS control mode are divided into four working modes: mode a, mode b, mode c and mode d. The magnitude relationship between the bridge inward shift phase D1 and the bridge outward shift phase D2 in each working mode is shown in formula (1):

[0082]

[0083] Figure 3The working waveforms of the DAB converter in four working modes are shown in FIG. 1 . As can be seen from the figure, since the DAB converter has a symmetrical structure, the inductor current i in one working cycle is L It also has symmetry. Let's start the analysis with mode b as the typical mode.

[0084] When the DAB converter works in mode b, the inductor current value within one working cycle can be obtained according to the relationship between the current and voltage across the inductor as shown in equation (2):

[0085]

[0086] In the formula, i L is the inductor current, t0=0, t1=D1T hs , t2=D2T hs , t3=(D1+D2)T hs , T hs is the half switching period of the DAB converter, f s is the switching frequency, f s =1 / (2T hs ), L is the sum of the leakage inductance and auxiliary inductance of the transformer, n is the number of turns on the primary side of the transformer, u0 is the output side voltage, k is the voltage transfer ratio, Among them, the maximum value of the inductor current is the current stress.

[0087] Then, substitute equation (2) into the calculation formula of the return power and transmission power of the DAB converter shown in equation (3), and obtain the return power and transmission power of mode b as shown in equation (4). In order to more intuitively compare and analyze the performance under different working modes, the maximum value of the transmission power of mode b is then calculated, and then the maximum value of the transmission power is used as the reference value of power normalization. The expression of the reference value of power normalization is shown in equation (5); then, based on equation (5), the transmission power and return power of mode b are normalized, and the return power function and transmission power function of mode b after normalization are obtained as shown in equation (6).

[0088] Among them, the calculation formula of the return power and transmission power of the DAB converter under the DPS control mode is:

[0089]

[0090] Where P1 represents the transmission power of the DAB converter, P DPS-bf represents the return power of the DAB converter, v H1(t) represents the terminal voltage of the H-bridge on the primary side of the transformer, t′2 is the time when the inductor current is 0 for the first time in one cycle;

[0091]

[0092] Where P 1b represents the transmission power of mode b, P DPS-bf-b Indicates the return power of mode b.

[0093]

[0094] Where P N It is the reference value of power normalization.

[0095]

[0096] The transmission power P of mode b in formula (6) is 1b is the normalized transmission power, the return power P of mode b DPS-bf-b is the normalized return power.

[0097] When the DAB converter works in the other three modes, similarly, firstly, the inductor current value within a working cycle is obtained according to the relationship between the current and voltage at both ends of the inductor, and then the inductor current value is substituted into formula (3) to obtain the return power and transmission power in the corresponding working mode, and then the return power and transmission power are normalized based on formula (5) to obtain the final return power function and transmission power function. Formula (7) lists the return power function and transmission power function of the four working modes, and Figure 4 The figure shows the transmission power normalization diagram of the DAB converter in the global mode, where "1" represents mode a, "2" represents mode b, "3" represents mode c, and "4" represents mode d:

[0098]

[0099] Where P 1a represents the transmission power of mode a, P DPS-bf-a represents the return power of mode a, P 1b represents the transmission power of mode b, P DPS-bf-b represents the return power of mode b, P 1c represents the transmission power of mode c, P DPS-bf-c represents the return power of mode c, P 1d represents the transmission power of mode d, P DPS-bf-d represents the return power of mode d, and k represents the voltage transfer ratio.

[0100] Step S2, respectively deriving the return power functions of the four working modes to obtain the calculated optimal return power path of each working mode.

[0101] The problem of minimizing the return power of the DAB converter when the output power is determined is transformed into solving the minimum value of the return power function in a specified scope under specified constraints. The specified constraints here refer to the fixed value of the output power, and the specified scope corresponds to the variable range of the transmission power.

[0102] Step S3, calculating the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimizing the calculated optimal return power path according to the intersection point to obtain the optimized calculated optimal return power path of each working mode.

[0103] For example, mode b is used as a typical mode to analyze the characteristics of the DAB converter under different shift ratio combinations, so as to optimize the return power. Specifically, firstly, the return power function in equation (6) is derived to obtain:

[0104]

[0105] Let the value of equation (8) be 0, and the optimal return power path for mode b is obtained as shown in equation (9):

[0106]

[0107] Figure 5 The calculated optimal return power path of mode b is shown. It can be seen from the figure that the calculated optimal return power path of mode b crosses other working modes. Therefore, the actual optimal return power path is the intersection of mode b and mode c under the calculated optimal return power path. Therefore, by combining equations (9) and (7) and making D1=D2, the intersection of the calculated optimal return power path of mode b and the actual optimal return power path can be obtained as:

[0108]

[0109] Wherein, P′1 represents the transmission power of the junction point, and D′2 represents the bridge outward displacement ratio of the junction point.

[0110] Then, the optimal return power path shown in equation (9) is optimized according to the intersection point shown in equation (10), and the optimal return power path shown in equation (9) is obtained. When , the optimal return power path after optimization of mode b is:

[0111]

[0112]

[0113] The same analysis method can be used to obtain the optimized and calculated optimal return power paths for the other three working modes.

[0114] Step S4, obtaining a shift ratio combination with the minimum return power under a condition of a certain transmission power according to the calculated optimal return power path after optimization of each working mode.

[0115] Specifically, under the condition of certain transmission power, by comparing the optimal return power paths in various working modes of the DAB converter, the path with the minimum return power is determined, and the shift ratio combination corresponding to the path is determined. Table 1 lists the shift ratio combination with the minimum return power and its corresponding return power value under different working modes and different transmission powers of the DAB converter. Among them, when the DAB converter works in mode a and mode d, the optimal operation cannot be obtained.

[0116] Table 1

[0117]

[0118] Step S5, defining the input and sliding surface of the super-helical sliding mode controller.

[0119] Among them, the super-helical sliding mode controller is an advanced nonlinear control strategy. In the design of the super-helical sliding mode controller, the input p is usually calculated based on the sliding surface function and its derivatives as well as the system state variables and their dynamics. The controller adjusts the input p to make the system state converge to the desired value quickly and stably along the predetermined sliding surface, thereby achieving the control goal of the system. The derivative s' of the sliding surface function reflects the rate at which the system state changes along the sliding surface, which is an important basis for the controller to adjust the system state to maintain or approach the sliding surface.

[0120] Specifically, the output capacitor C on the right side of the transformer o The stored energy can be expressed as:

[0121]

[0122] Where P o is the output power of the DAB converter, P o =u o i o , E c is the energy stored in the output capacitor, and P is the transmission power of the DAB converter. After simplifying equation (13), we get:

[0123]

[0124] In the formula, Indicates u o Perform derivation.

[0125] The output voltage error e is defined as:

[0126] e=u o-u ref (15)

[0127] In the formula, u ref is the reference voltage.

[0128] In order to ensure the tracking error e = 0, the sliding surface s of the super-helical sliding mode controller is designed as:

[0129] s=k1e+k2∫(e)dt (16)

[0130] Where k1 and k2 are positive coefficients that determine the convergence rate of the error e.

[0131] The input P of the super-helical sliding mode controller consists of two parts: the model equivalent part u * and the switching control part u1, where u * The role of is to guide the system state trajectory into and remain on the sliding surface. In sliding mode control, due to external disturbances, internal uncertainties or modeling errors in the system, the system state may deviate from the sliding variable. The purpose of u1 is to ensure that the system state does not leave the sliding surface. This switching control strategy helps to enhance the robustness and stability of the system. The specific expression of the input P of the super-helical sliding mode controller is shown in formula (17):

[0132]

[0133] In the formula, α and β are both positive parameters.

[0134] When the output voltage error e reaches the fixed time sliding surface, According to formula (16), we can get:

[0135]

[0136] The controller input P is used to replace the transmission power P1, and Substituting into equation (14) and combining equation (18), the final super-helical sliding mode controller is:

[0137]

[0138] Step S6, obtaining an optimized bridge outer shift ratio according to the input and sliding surface of the super-helical sliding mode controller, the inner bridge shift ratio in the shift ratio combination with the minimum return power, and the return power function and the transmission power function in the four working modes.

[0139] Specifically, according to the bridge inner shift ratio D1 in the shift ratio combination with the smallest return power in Table 1, the return power function and the transmission power function under the four working modes shown in formula (7), and the input and sliding mode surface of the super spiral sliding mode controller shown in formula (19), the optimized bridge outer shift ratio shown in formula (20) can be obtained.

[0140]

[0141] The DAB converter return power optimization method based on super-helical sliding mode control in this embodiment constructs the return power function and transmission power function of the DAB converter under the dual phase-shift control mode in four working modes, derives the return power function of each working mode to obtain the optimal return power path, and optimizes the intersection point with the actual optimal path to ensure the accuracy of the calculated optimal return power path. Then, under the condition of a certain transmission power, the phase shift ratio combination with the minimum return power is determined according to the calculated optimal return power path after optimization of each working mode, thereby significantly reducing the return power of the DAB converter. The DAB converter in this method is controlled by a dual phase-shift control method, and the dual phase-shift control does not need to switch the control signal in the case of bidirectional energy transmission, and the power adjustment range is wider, thereby reducing the control difficulty of the system. In addition, the method realizes dynamic adjustment and optimization of the bridge outer phase shift ratio by introducing the super-helical sliding mode control strategy, further improving the stability and robustness of the system.

[0142] Based on the same inventive concept, the embodiment of the present application also provides a DAB converter backflow power optimization device based on super spiral sliding mode control for implementing the DAB converter backflow power optimization method based on super spiral sliding mode control involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of one or more DAB converter backflow power optimization devices based on super spiral sliding mode control provided below can refer to the limitations of the DAB converter backflow power optimization method based on super spiral sliding mode control above, and will not be repeated here.

[0143] Embodiment 2

[0144] An embodiment of the present disclosure provides a DAB converter backflow power optimization device 600 based on super spiral sliding mode control, such as Figure 6 As shown, including:

[0145] The optimal return power path calculation module 601 is used to divide the working modes of the DAB converter under the DPS control mode into four types according to the size relationship between the bridge inward shift ratio and the bridge outward shift ratio, and construct the return power function and transmission power function of the four working modes; respectively derive the return power function of the four working modes to obtain the calculated optimal return power path of each working mode;

[0146] The optimal return power path optimization module 602 is used to calculate the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimize the calculated optimal return power path according to the intersection point to obtain the calculated optimal return power path after optimization of each working mode;

[0147] The shift ratio combination and return power calculation module 603 is used to calculate the optimal return power path after optimization of each working mode to obtain the shift ratio combination with the minimum return power under the condition of a certain transmission power and the return power corresponding to the shift ratio combination with the minimum return power;

[0148] The bridge outer shift ratio optimization module 604 is used to define the input and sliding surface of the super-helical sliding mode controller; the optimized bridge outer shift ratio is obtained according to the input and sliding surface of the super-helical sliding mode controller, the bridge inner shift ratio in the shift ratio combination with the minimum reflux power, and the reflux power function and transmission power function in four working modes.

[0149] Each module in the above-mentioned DAB converter backflow power optimization device based on super-helical sliding mode control can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0150] Embodiment 3

[0151] An embodiment of the present disclosure provides a DAB converter backflow power optimization system based on super spiral sliding mode control, such as Figure 7 As shown, the system includes a reflux power global optimization module, a super spiral sliding mode controller and a PWM controller. The reflux power global optimization module is used to obtain the auxiliary inductance L, the input side voltage u i , output side voltage u o , load current i o and the switching frequency f s , and according to the input side voltage u i , output side voltage u oThe voltage transfer ratio k is calculated based on the primary side turns n of the transformer, and the transmission power P1 of the DAB converter is calculated according to formula (3). Then, according to the voltage transfer ratio and the transmission power, the corresponding shift phase combination with the minimum return power is obtained from Table 1, including the inner bridge shift phase D1 and the outer bridge shift phase D2, and the inner bridge shift phase D1 is sent to the super spiral sliding mode controller and the PWM controller; the super spiral sliding mode controller optimizes the outer bridge shift phase D2 based on the inner bridge shift phase D1 and formulas (14)-(20), and sends the optimized outer bridge shift phase D2 to the PWM controller; the PWM controller controls the power switching devices in the DAB converter according to the inner bridge shift phase D1 and the optimized outer bridge shift phase D2.

[0152] Embodiment 4

[0153] Furthermore, in order to demonstrate the effectiveness of the DAB converter reflux power optimization method based on super-helical sliding mode control of the present application, this embodiment is compared with the traditional current stress optimization method, and experiments are carried out under three working conditions: light load, medium load and heavy load.

[0154] When the resistance R of the DAB converter load is 20Ω, the transmission power P1 is 0.256w, and the DAB converter operates in a light load condition. Figure 8 The output voltage u of the traditional current stress optimization method (DPS-CS) under light load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf . Fig. 9 The output voltage u of the DAB converter backflow power optimization method (DPS-BF) without super spiral sliding mode control in this application under light load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf . Fig.10 The output voltage u of the DAB converter reflux power optimization method (DPS-STSMC-BF) after adding super spiral sliding mode control in this application under light load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf .from Figure 8-Figure 10It can be seen that the current stress of DPS-CS is 6.4A and the reflow power is 110W, the current stress of DPS-BF is 7.6A and the reflow power is 50W, and the current stress of DPS-STSMC-BF is 7.6A and the reflow power is 40W. The current stress of DPS-BF and DPS-STSMC-BF is 1.2A higher than that of DPS-CS, and the reflow power is reduced by 60W and 70W respectively.

[0155] When the resistance R of the DAB converter load is 10Ω, the transmission power P1 is 0.512w, and the DAB converter operates in a medium load condition. Fig.11 The output voltage u of the traditional current stress optimization method (DPS-CS) under medium load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf . Fig.12 The output voltage u of the DAB converter backflow power optimization method (DPS-BF) without super spiral sliding mode control in this application under medium load conditions is shown. o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf . Fig.13 The output voltage u of the DAB converter reflux power optimization method (DPS-STSMC-BF) after adding super spiral sliding mode control in this application under medium load conditions is shown. o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf .from Figure 11-13 It can be seen that the current stress of DPS-CS is 8.0A, the reflow power is 180W, the current stress of DPS-BF is 9.8A, the reflow power is 75W, and the current stress of DPS-STSMC-BF is 9.9A, the reflow power is 75W. The current stress of the latter two is 1.8A and 1.9A higher than that of DPS-CS, and the reflow power is reduced by 105W.

[0156] When the resistance R of the DAB converter load is 7.3Ω, the transmission power P1 is 0.7w, and the DAB converter operates in a heavy load condition. Fig.14 The output voltage u of the traditional current stress optimization method (DPS-CS) under heavy load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power PDPS-bf . Fig.15 The output side voltage u of the DAB converter backflow power optimization method (DPS-BF) without adding super spiral sliding mode control in this application under heavy load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf . Fig.16 The output voltage u of the DAB converter reflux power optimization method (DPS-STSMC-BF) after adding super spiral sliding mode control in this application under heavy load conditions is shown o , the terminal voltage v of the H bridge on the primary side of the transformer H1 , inductor current i L and the DAB converter's return power P DPS-bf .from Figure 14-16 It can be seen that the current stress of DPS-CS is 9.5A and the reflow power is 200W; the current stress of DPS-BF is 9.9A and the reflow power is 180W; the current stress of DPS-STSMC-BF is 9.9A and the reflow power is 170W. The current stress of DPS-BF and DPS-STSMC-BF is 0.4A higher than that of DPS-CS, and the reflow power is reduced by 20W and 30W respectively.

[0157] It can be seen from the above experimental results that the DAB converter reflux power optimization method based on super-helical sliding mode control proposed in this application can achieve effective optimization of reflux power when the DAB converter operates under light load, medium load or heavy load conditions, and its optimization effect is remarkable.

[0158] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0159] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A DAB converter reflux power optimization method based on super-helical sliding mode control, characterized in that: The method comprises: Step S1, dividing the working modes of the DAB converter under the dual phase shift control mode into four types according to the size relationship between the inner bridge shift phase and the outer bridge shift phase, and constructing the return power function and the transmission power function of the four working modes; Step S2, respectively deriving the return power functions of the four working modes to obtain the calculated optimal return power path of each working mode; Step S3, calculating the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimizing the calculated optimal return power path according to the intersection point to obtain the calculated optimal return power path after optimization of each working mode; Step S4, obtaining a shift ratio combination with the minimum return power under a condition of a certain transmission power according to the calculated optimal return power path after optimization of each working mode; Step S5, defining the input and sliding surface of the super-helical sliding mode controller; Step S6, obtaining an optimized bridge outer shift ratio according to the input and sliding surface of the superhelical sliding mode controller, the inner bridge shift ratio in the shift ratio combination with the minimum return power, and the return power function and transmission power function in the four working modes.

2. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 1 is characterized in that: The magnitude relationships between the bridge inward displacement D1 and the bridge outward displacement D2 in the four working modes are as follows: Mode a, 0<D1, D2<1, D1<D2, D1+D2≥1; Mode b, 0<D1, D2<1, D1<D2, D1+D2<1; Mode c, 0<D1, D2<1, D1≥D2, D1+D2<1; Mode d, 0<D1, D2<1, D1≥D2, D1+D2≥1.

3. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 2 is characterized in that: For the four working modes of the DAB converter, the return power function and the transmission power function are constructed according to the following steps: Step S11, obtaining the inductor current value of the DAB converter in one cycle; Step S12, obtaining the return power and the transmission power according to the inductor current value and the port voltage of the H-bridge on the primary side of the transformer; Step S13: normalizing the return power and the transmission power by taking the maximum value of the transmission power as a reference value for power normalization.

4. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 3 is characterized in that: The expressions of the return power function and transmission power function of the four working modes after normalization are: Where P 1a represents the transmission power of mode a, P DPS-bf-a represents the return power of mode a, P 1b represents the transmission power of mode b, P DPS-bf-b represents the return power of mode b, P 1c represents the transmission power of mode c, P DPS-bf-c represents the return power of mode c, P 1d represents the transmission power of mode d, P DPS-bf-d represents the return power of mode d, and k represents the voltage transfer ratio.

5. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 4 is characterized in that: When the DAB converter operates in mode b, the expression of the inductor current value of the DAB converter in one cycle is: In the formula, i L is the inductor current, t0=0, t1=D1T hs , t2=D2T hs , t3=(D1+D2)T hs , T hs is the half switching period of the DAB converter, f s is the switching frequency, f s =1 / (2T hs ), L is the sum of the leakage inductance and auxiliary inductance of the transformer, n is the number of turns on the primary side of the transformer, u0 is the output side voltage, and k is the voltage transfer ratio; The expressions of the return power function and transmission power function of mode b after normalization are: Where P 1b represents the transmission power of mode b, P DPS-bf-b Indicates the return power of mode b.

6. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 5, characterized in that: The step S2 comprises: Step S21, deriving the return power function of mode b after normalization; the expression of the derivative result is: Step S22, setting the value of the derived return power function to 0, and obtaining the optimal return power path for mode b; the expression for calculating the optimal return power path for mode b is: The step S3 comprises: Step S31, let D1=D2, and obtain the intersection point between the calculated optimal return power path and the actual optimal return power path of the mode b; the expression of the intersection point is: Wherein, P′1 represents the transmission power of the junction point, and D′2 represents the bridge outward displacement ratio of the junction point; Step S32, optimizing the calculated optimal return power path obtained in step S22 according to the intersection point, and obtaining the calculated optimal return power path after optimization of mode b; wherein, when When , the optimal return power path after optimization of mode b is: Wherein, P1 represents the transmission power of the DAB converter.

7. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 4 is characterized in that: The shift ratio combination with the smallest return power and the return power corresponding to the shift ratio combination with the smallest return power include: When 0≤P1<0.5, the working mode of the DAB converter is mode c, and the phase shift combination is The reflux power is 0.25(k-1) 2 P1k -1 ; when When the working mode of the DAB converter is mode b, the shift ratio combination is The return power is when When the working mode of the DAB converter is mode b, the shift ratio combination is: The return power is: Wherein, P1 is the transmission power of the DAB converter.

8. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 2, characterized in that: The input and sliding surface expressions of the super-helical sliding mode controller are: Where p represents the input of the super-helical sliding mode controller, L is the sum of the leakage inductance and auxiliary inductance of the transformer, and f s is the switching frequency, C o is the transformer output side support capacitor, n is the number of turns on the primary side of the transformer, u i is the voltage on the transformer input side, i o is the load current, k1 and k2 are both positive coefficients, sgn is the sign function, α and β are both positive parameters, e is the output voltage error, s is the sliding surface, represents the derivative of the sliding surface; The expression of the sliding surface is: s = k1e + k2∫ (e) dt, and the expression of the output voltage error is: e = u o -u ref ,u o is the voltage at the output side of the transformer, u ref is the reference voltage.

9. The DAB converter reflux power optimization method based on super spiral sliding mode control according to claim 8, characterized in that: The expression of the optimized bridge outward displacement ratio is: Wherein, D1 is the bridge internal shift phase ratio in the shift phase ratio combination with the smallest reflux power in step S4.

10. A DAB converter reflux power optimization device based on super spiral sliding mode control, characterized in that: The device comprises: The optimal return power path calculation module is used to divide the working modes of the DAB converter under the DPS control mode into four types according to the size relationship between the bridge inward shift ratio and the bridge outward shift ratio, and construct the return power function and transmission power function of the four working modes; respectively derive the return power function of the four working modes to obtain the calculated optimal return power path of each working mode; An optimal return power path optimization module is used to calculate the intersection point between the calculated optimal return power path and the actual optimal return power path of each working mode, and optimize the calculated optimal return power path according to the intersection point to obtain the calculated optimal return power path after optimization of each working mode; A shift ratio combination and return power calculation module, used to calculate the optimal return power path after optimization of each working mode, and obtain the shift ratio combination with the minimum return power and the return power corresponding to the shift ratio combination with the minimum return power under the condition of a certain transmission power; The bridge outer shift ratio optimization module is used to define the input and sliding surface of the super-helical sliding mode controller; the optimized bridge outer shift ratio is obtained according to the input and sliding surface of the super-helical sliding mode controller, the bridge inner shift ratio in the shift ratio combination with the smallest reflux power, and the reflux power function and transmission power function in the four working modes.

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