Method, system, device and medium for optimizing current stress of dual active bridge converter

Abstract

The application discloses a dual active bridge converter current stress optimization method, system, device and medium, and relates to the technical field of converters, and comprises the following steps: a dual active bridge converter containing an inductor is constructed by introducing a transformer with a variable turns ratio; the turns ratio design basis of the transformer is analyzed according to a plurality of working modes of the dual active bridge converter under triple phase shifting; the average inductor current stress of each group of turns ratio under full-range input voltage and output voltage of the dual active bridge converter is calculated by using a double integral method based on the turns ratio design basis; the current stress surface corresponding to each turns ratio is determined according to the average inductor current stress, the intersection line of any two current stress surfaces is determined according to a to-be-transmitted power value, the intersection line is used as a critical line for turns ratio switching, and thus the design turns ratio of the transformer is determined, and the turns ratio is selected from the design turns ratio under each input and output voltage condition. The application solves the problems of large current stress, increased power switch loss and low transmission efficiency in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of converter technology, in particular to a dual active bridge converter current stress optimization method, system, device and medium. BACKGROUND

[0002] Due to the characteristics of electrical isolation, high power density, easy to realize soft switching, etc., the dual active bridge DC-DC converter (DAB converter) has been widely used in energy storage, distributed energy and electric vehicles, etc. However, the dual active full-bridge DC-DC converter has the problem of large current stress under extreme working conditions. The DAB converter uses single-phase-shift (SPS) control, which has only one control variable, large backflow power, large current stress under the condition of transmitting the same power, large inductance magnetic core volume, and the on-state loss of power switches also increases accordingly; dual-phase-shift (DPS) and extended-phase-shift (EPS) both have two control variables, which can reduce the backflow power and inductance current stress, but cannot optimize the double-sided backflow power on the input side and the output side; triple-phase-shift (TPS) has three control variables, which can further optimize the double-sided backflow power, reduce the inductance current peak value, and realize zero-voltage turn-on or zero-current turn-off of power devices.

[0003] In the prior art, for example, an invention patent with publication number CN118586198A discloses a magnetic element design method, device and equipment of a dual active bridge converter, the optimization process of which is relatively complex, and the adaptability to different working conditions is weak, making it difficult to achieve optimal performance under extreme working conditions. For another example, an invention patent with publication number CN118249628A discloses a dual active bridge converter efficiency optimization modulation method and device, which lacks comprehensive consideration of current stress and turn ratio selection, and cannot fully solve the problem of current stress under various working conditions. In general, the existing technology mainly has the following problems: 1) large current stress: under extreme working conditions, the current stress of the dual active full-bridge DC-DC converter is too large, which may cause the device to fail prematurely and reduce the reliability of the system. 2) increased power switch loss: under single-phase-shift control, due to the large current stress, the on-state loss of power switches increases accordingly, reducing the overall efficiency. 3) low transmission efficiency: although multi-phase-shift control can improve performance, under certain working conditions, especially under high load or high frequency operation, the transmission efficiency of the system may still be lower than expected, limiting the improvement of power density. SUMMARY

[0004] The application provides a dual active bridge converter current stress optimization method, system, device and medium, and aims at solving the problems of large current stress, increased power switch loss and low transmission efficiency in the prior art.

[0005] Therefore, the application provides a dual active bridge converter current stress optimization method in the first aspect, which comprises the following steps of:

[0006] a transformer with variable turns ratio is introduced to construct a dual active bridge converter containing inductance;

[0007] According to several working modes of the dual active bridge converter under triple phase shift, the turns ratio design basis of the transformer is analyzed;

[0008] Based on the turns ratio design basis, the average inductance current stress of each group of turns ratio under full range input voltage and output voltage of the dual active bridge converter is calculated by using double integration method;

[0009] According to the average inductance current stress, the current stress surface corresponding to each turns ratio is determined, the intersection line of any two current stress surfaces is determined according to the to-be-transmitted power value, the intersection line is taken as the critical line of turns ratio switching, the design turns ratio of the transformer is determined according to the critical line, and the turns ratio is selected from the design turns ratio under each input and output voltage condition.

[0010] Optionally, the transformer with variable turns ratio is introduced to construct the dual active bridge converter containing inductance, which comprises the following steps of:

[0011] The transformer and a single-pole double-throw relay are introduced to construct the dual active bridge converter containing inductance, wherein the single-pole double-throw relay is used to change the turns ratio of the transformer.

[0012] Optionally, the transformer is a high-frequency transformer, and the primary side and the secondary side of the high-frequency transformer both have double windings.

[0013] Optionally, the turns ratio design basis of the transformer is analyzed according to the several working modes of the dual active bridge converter under triple phase shift, which comprises the following steps of:

[0014] The several working modes of the dual active bridge converter under triple phase shift are determined, and the working mode with zero backflow power is selected from the several working modes, wherein the triple phase shift means that there are internal phase shift of the primary side, phase shift between the primary side and the secondary side and internal phase shift of the secondary side.

[0015] Based on the working mode with zero backflow power under triple phase shift control, the current characteristics of the dual active bridge converter are analyzed to obtain the inductance current peak value, and the transmission power of the working mode with zero backflow power is calculated according to the inductance current peak value.

[0016] The peak inductor current and the transmission power of the zero-return power operating mode are normalized to obtain the normalized peak inductor current and normalized transmission power under triple phase shift.

[0017] Based on the per-unit inductor current peak value and the per-unit transmission power, and in conjunction with the Lagrange equation, determine the phase shift combination that satisfies the power requirements and minimizes the inductor current peak value for each of the zero-return power operating modes.

[0018] The transmission power range of the zero-return power operating mode is determined based on the phase shift combination. An expression for the inductor current is constructed based on the transmission power range. Based on the expression for the inductor current, the inductor current stress is determined as the basis for the turns ratio design of the transformer.

[0019] Optionally, the step of calculating the average inductor current stress per turns ratio for the dual active bridge converter under the full range of input and output voltages using the double integral method includes:

[0020] Let the regions of the input voltage and the output voltage, and the area of ​​those regions, be defined.

[0021] The inductor current stress in the region is double-integrated to obtain the integral value of the inductor current stress in the region.

[0022] The average inductor current stress within the range of the input voltage and the output voltage is obtained by dividing the integral value of the inductor current stress in the region by the area of ​​the region.

[0023] Optionally, determining the design turns ratio of the transformer based on the critical line includes:

[0024] Based on the number of turns on the primary upper winding, the primary lower winding, the secondary lower winding, and the secondary upper winding of the high-frequency transformer, determine a set of turns ratios that includes several different turns ratios.

[0025] Using the critical line as the turns ratio switching condition, the turns ratio of the secondary and primary windings is gradually changed to obtain each turns ratio in the set of turns ratios. At the same time, based on the principle of optimal current stress, the average inductor current stress of each turns ratio in the set of turns ratios is calculated under the full range of input and output voltages according to the turns ratio switching condition.

[0026] The turns ratio corresponding to the minimum average inductance current stress is taken as the design turns ratio of the transformer.

[0027] Optionally, the set of turns ratios includes three cases: N1 / (N1+N2), (N1+N2) / (N1+N2), and (N1+N2) / N1, wherein the number of turns on the primary side upper winding of the high-frequency transformer is N1, the number of turns on the primary side lower winding is N2, the number of turns on the secondary side lower winding is N1, and the number of turns on the secondary side upper winding is N2.

[0028] A second aspect of the present invention provides a current stress optimization system for a dual active bridge converter, the system comprising:

[0029] A building block for constructing a dual active bridge converter with inductance by introducing a transformer with a variable turns ratio;

[0030] The analysis unit is used to analyze the turns ratio design basis of the transformer based on several operating modes of the dual active bridge converter under triple phase shift.

[0031] The calculation unit is used to calculate the average inductor current stress of each turns ratio under the full range of input and output voltages of the dual active bridge converter based on the turns ratio design and using the double integration method.

[0032] The optimization unit is used to determine the current stress surface corresponding to each of the turns ratios based on the average inductance current stress, determine the boundary line where any two of the current stress surfaces intersect based on the power value to be transmitted, and use the boundary line as the critical line for turns ratio switching. Based on the critical line, the design turns ratio of the transformer is determined, and the turns ratio is selected from the design turns ratio under each input and output voltage condition.

[0033] A third aspect of the present invention provides a current stress optimization device for a dual active bridge converter, the device comprising a processor and a memory:

[0034] The memory is used to store program code and transmit the program code to the processor;

[0035] The processor is configured to execute the steps of the dual active bridge converter current stress optimization method as described in the first aspect above, according to the instructions in the program code.

[0036] A fourth aspect of the present invention provides a computer-readable storage medium for storing program code for executing the current stress optimization method for a dual active bridge converter described in the first aspect above.

[0037] As can be seen from the above technical solutions, the present invention has the following advantages:

[0038] This invention provides a current stress optimization method for a dual active bridge converter. By introducing a variable turns ratio transformer, the transformer turns ratio is dynamically switched under different input and output voltage conditions. This design can automatically select the optimal turns ratio based on changes in the voltage ratio, achieving low current stress operation across different voltage ranges, thereby significantly reducing current stress. Specifically, by analyzing and calculating the current stress based on a given input and output voltage range and the required power level, the optimal turns ratio is selected. Under constant power transmission conditions, the conduction current of the inductor and switching transistor is significantly reduced, effectively lowering the current peak in the system and reducing switching and conduction losses. Simultaneously, the optimized turns ratio switching strategy enables the dual active bridge converter to transmit power with higher efficiency over a wide input and output voltage range. This design significantly improves the system's adaptability and stability under various operating conditions, broadening the converter's application range. Through phase shift optimization control under triple phase shift control, the transformer can dynamically adjust the combination of phase shifts under various voltage ratios and load conditions, further realizing automated optimization control and ensuring minimized current stress in any operating mode. This automatic adjustment feature reduces the complexity of system design and debugging, improves the converter's operating efficiency and overall performance, and meets a wider range of application needs, especially in applications requiring high power density and high efficiency.

[0039] In summary, this invention, through a combination of flexible turns ratio switching and phase shift optimization, enables the converter to maintain stable and efficient operation under different input and output voltages, while effectively reducing current stress, thereby improving the overall system efficiency and reliability, demonstrating significant technical advantages. For actual voltage variations in different application scenarios, this strategy ensures that the converter always operates in an optimal current stress state, thus improving overall system performance. This solves the problems of high current stress, increased power switching losses, and low transmission efficiency in existing technologies. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A flowchart illustrating a current stress optimization method for a dual active bridge converter provided in an embodiment of the present invention;

[0042] Figure 2 This invention provides a dual active bridge DC-DC converter.

[0043] Figure 3 The six operating modes of the three-phase shift control provided in the embodiments of the present invention;

[0044] Figure 4 The driving signal and voltage waveform diagrams of the dual active bridge converter under three-phase-shift control provided in the embodiments of the present invention are shown below.

[0045] Figure 5 Current stress curves under different turns ratio combinations provided in embodiments of the present invention;

[0046] Figure 6 This provides the turns ratio distribution region under different input / output voltage combinations in the embodiments of the present invention;

[0047] Figure 7 This is a schematic diagram of a current stress optimization system for a dual active bridge converter provided in an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] Please see Figure 1 The present invention provides a current stress optimization method for a dual active bridge converter, comprising:

[0050] Step 101: Construct a dual active bridge converter with inductance by introducing a transformer with a variable turns ratio.

[0051] In one embodiment, step 101 includes:

[0052] A dual active bridge converter with inductance is constructed by introducing a transformer and a single-pole double-throw relay, wherein the single-pole double-throw relay is used to change the turns ratio of the transformer; wherein the transformer is a high-frequency transformer, and both the primary and secondary sides of the high-frequency transformer have dual windings.

[0053] It should be noted that the dual active bridge converter of the present invention is a dual active bridge DC-DC converter, and will be described below as a dual active bridge converter.

[0054] Dual active bridge converter topology as follows Figure 2As shown, it consists of a high-frequency transformer T with a turns ratio of n:1, an inductor L, and an active full-bridge on the primary and secondary sides of the transformer (each full-bridge consists of 4 switching transistors, typically MOSFETs or IGBTs). Figure 2 In this example, the switching transistor used is a MOSFET, for illustrative purposes only. The transformer consists of capacitors C1 and C2, where transformer T is a variable turns ratio transformer, characterized by having dual windings on both the primary and secondary sides. The turns ratio of the high-frequency transformer can be changed via a single-pole double-throw relay. in U out These are the DC terminal voltages on both sides.

[0055] Step 102: Based on the various operating modes of the dual active bridge converter under triple phase shift, analyze the design basis of the transformer turns ratio.

[0056] In one embodiment, step 102 includes:

[0057] Step 1021: Determine several operating modes of the dual active bridge converter under triple phase shift, and select the zero return power operating mode from several operating modes. The triple phase shift refers to the existence of phase shift within the primary side, phase shift between the primary and secondary sides, and phase shift within the secondary side.

[0058] It should be noted that the power transfer expression of the dual active bridge converter under TPS (triple phase shift) control is as follows:

[0059] (1)

[0060] In the formula, f is the switching frequency, and D2 is the phase shift between the primary and secondary sides. From equation (1), the expressions for the maximum power and maximum current of the converter under TPS control are:

[0061] (2)

[0062] The per-unit expressions in the following text are all based on equation (2).

[0063] like Figure 2 As shown, under TPS control, the dual active bridge DC-DC converter employs three control degrees of freedom: with switch S1 as the reference, D1 is the phase shift within the primary side, i.e., the phase shift between switches S1 and S4; D2 is the phase shift between the primary and secondary sides, i.e., the phase shift between switches S1 and S5; and D3 is the phase shift within the secondary side, i.e., the phase shift between switches S5 and S8. Both full-bridge output voltages are three-level waves. Based on the relationship between the phase shifts, TPS control can be divided into six modes, and the full-bridge AC output voltage waveforms under different modes are shown below. Figure 3 As shown.

[0064] Figure 3All six operating modes can achieve positive energy transfer; however, there is overlap in the transferred power. For ease of analysis, the less efficient operating modes can be discarded. Figure 3 As can be seen from Modes 2, 3, and 6, the AC voltage output from the primary side of the DAB converter... u AB AC voltage output from the secondary side of the DAB converter u CD The part with the same polarity, i.e. When transmitting power, the inductor can only store energy under the influence of input or output voltage, causing the inductor current to increase rapidly, and then release the stored energy to the load. This mode is similar to the operating mode of a Buck-Boost converter. When transmitting the same power, the inductor current stress is high, efficiency is low, and the power transmission range is small. For other operating modes... Figure 3 Mode 1, Mode 4, and Mode 5 all have u AB with u CD For components with the same polarity, the energy can be directly transferred from the input to the output. The inductor current rises slowly, resulting in lower current stress. Therefore, when selecting the zero-return-power operating mode, inductor current stress should be disregarded. Figure 3 Mode 2, Mode 3, and Mode 6 are three power modes with high current peak values.

[0065] Define the voltage transfer ratio as k=U in / (nU out ), k>1 is defined as buck mode, and k<1 is defined as boost mode.

[0066] Mode 1: ;

[0067] Mode 2: ;

[0068] Mode 3: ;

[0069] Mode 4: ;

[0070] Mode 5: ;

[0071] Mode 6: .

[0072] Step 1022: Based on the zero-return power operating mode under triple phase-shift control, analyze the current characteristics of the dual active bridge converter, obtain the peak value of the inductor current, and calculate the transmission power of the zero-return power operating mode based on the peak value of the inductor current.

[0073] It should be noted that the basic characteristics of the converter are analyzed using TPS control mode 1 as an example; the analysis for other modes is the same. The magnitude of the converter current stress depends on the inductor current i. L The peak size. Figure 4 This indicates that at time t4, the inductor current i L If we obtain the maximum value and consider t0 as the starting time, then the times t1, t2, t3, and t4 are respectively t1=D1T hs t2=(D2-D1)T hs t3=(D2+D3)T hs t4=(1-D2-D3)T hs Let the switching frequency be f, then T hs =1 / 2f, according to the volt-second principle, the inductor current of the converter in steady-state operation satisfies i L (t0)=-i L (t4), based on this relationship, the expression for the peak inductor current can be obtained as follows:

[0074] (3)

[0075] Similarly, the peak inductor current for modes 4 and 5 under TPS control can be obtained. The converter's transmission power under TPS control is the integral of the product of the average inductor current and the voltage. Therefore, the transmission power expressions for modes 1, 4, and 5 can be derived as follows:

[0076] Mode 1: (4)

[0077] Mode 4: (5)

[0078] Mode 5: (6)

[0079] Step 1023: Normalize the peak inductor current and the transmission power in the zero-return power operating mode to obtain the normalized peak inductor current and normalized transmission power under triple phase shift.

[0080] It should be noted that, by normalizing equations (3), (4), (5), and (6), the normalized inductor current peak value i and transmission power P expressions for TPS control are as follows:

[0081] (7)

[0082] Mode 1: (8)

[0083] Mode 4: (9)

[0084] Mode 5: (10)

[0085] Step 1024: Determine the phase shift combination that meets the power requirement and has the minimum peak inductor current for each zero-backflow power operating mode according to the per-unit peak inductor current and the per-unit transmitted power, and in combination with the Lagrange equation.

[0086] It should be noted that Equations (7), (8), (9), and (10) indicate that the peak inductor current i and the transmitted power P are related to the phase shifts D1, D2, and D3. There are countless combinations of D1, D2, and D3, and the corresponding i and P for each combination are different. To obtain the phase shift combination that can both meet the power requirement and minimize the peak inductor current, the Lagrange equation is established:

[0087] (11)

[0088] In the above formula, μ is the multiplier factor and P0 is the given transmitted power value. Let:

[0089] (12)

[0090] Substitute Equations (7), (8), (9), and (10) into Equation (11), and in combination with Equation (12), it can be obtained that there is no solution for Mode 4. The optimal phase shift combination for Mode 1 is:

[0091] (13)

[0092] The optimal phase shift combination for Mode 5 is:

[0093] (14)

[0094] Since the constraint condition for the phase shift of Mode 1 is D2 > D1, in combination with Equation (11), the transmitted power range for Mode 1 operation can be obtained: .

[0095] The constraint conditions for the phase shift of Mode 5 are D2 < D1 and D2 < D3. In combination with Equation (12), the transmitted power range for Mode 5 operation is: , and the expression for the peak inductor current varying with the transmitted power P0 after current stress optimization can be obtained.

[0096] Step 1025: Determine the transmitted power range for the zero-backflow power operating mode according to the phase shift combination, construct the expression of the inductor current based on the transmitted power range, and perform analysis based on the expression of the inductor current to determine the inductor current stress as the design basis for the transformer turns ratio.

[0097] It should be noted that the optimized TPS control can achieve the global minimization of the current stress in Modes 1 and 5.

[0098] When k ≥ 1:

[0099] (15)

[0100] When 0 < k < 1:

[0101] (16)

[0102] The more the voltage conversion ratio k deviates from 1, the greater the inductor current stress and the return power will be. When the difference between the output voltage and the input voltage is large and the transformer turns ratio is not properly selected, even if the phase shift is optimized through the control strategy, the obtained inductor current stress may exceed the maximum conduction current that the switching device can withstand. At the same time, the inductor current stress is positively correlated with the switching loss and conduction loss of the dual-active-bridge converter. A large current stress will cause more losses in the switching device, resulting in a decrease in efficiency. Therefore, the main reference basis for the design of the transformer turns ratio is the inductor current stress under a large input-output voltage difference.

[0103] Step 103: Based on the turns ratio design basis, use the double integral method to calculate the average inductor current stress of each turns ratio under the full range of input voltages and output voltages of the dual-active-bridge converter.

[0104] It should be noted that when the inductor current stress is determined as the turns ratio design basis in Step 102, Step 103 uses the double integral method to calculate the average inductor current stress of each turns ratio under the full range of input voltages and output voltages of the dual-active-bridge converter, which is used to determine the transformer turns ratio in the dual-active-bridge converter subsequently.

[0105] Furthermore, it should be noted that a transformer with a variable turns ratio can meet the optimal current stress under extreme working conditions, and changing the turns ratio can broaden the input-output voltage adaptation range. Denote the number of turns of the upper winding side of the primary side as N1, the number of turns of the lower winding as N2, the number of turns of the lower winding side of the secondary side as N1, and the number of turns of the upper winding as N2. Since the number of turns of the upper winding of the primary side and the lower winding of the secondary side of the transformer is the same, and the number of turns of the lower winding of the primary side and the upper winding of the secondary side is the same, there are three cases for a set of turns ratios of the transformer: N1 / (N1 + N2), (N1 + N2) / (N1 + N2), (N1 + N2) / N1. To select a suitable turns ratio of the transformer, it is necessary to analyze the average inductor current stress of each turns ratio under the full range of input-output voltages. Since n is a variable, the current stress cannot be expressed as a per-unit value and needs to be converted into a nominal value form. When the turns ratio is n, the current stress formula is: . Under different combinations of input voltages and output voltages, when the current stress surface of one turns ratio intersects with the current stress surface of another turns ratio, the intersecting curve is the critical line for turns ratio switching. At this time, the inductor current stress can be minimized by switching the turns ratio, so as to achieve the purpose of overall optimization.

[0106] In one embodiment, step 103, which uses the double integration method to calculate the average inductor current stress per turns ratio for the dual active bridge converter across the full range of input and output voltages, includes:

[0107] Step 1031: Define the regions of input voltage and output voltage, as well as the area of ​​those regions.

[0108] It should be noted that the area A of the input / output voltage region R is calculated as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] The value range [a, b] and output voltage Given a fixed range [c, d], the area A of region R is obtained by multiplying the length of the input voltage interval by the length of the output voltage interval, i.e., A = (ba) × (dc), where a and b are the input voltage and output voltage interval, respectively. The lower and upper limits are given by c and d, respectively, which are the lower and upper limits of the output voltage U_out.

[0109] Step 1032: Perform a double integral on the inductor current stress in the region to obtain the integral value of the inductor current stress in the region.

[0110] It should be noted that the calculation function Integral over region R;

[0111] Step 1033: Divide the integral value of the inductor current stress of the region by the area of ​​the region to obtain the average inductor current stress within the range of input voltage and output voltage.

[0112] It should be noted that dividing the integral result by the area A of the region yields the average value I. a . (17)

[0113] Formula (17) is usually calculated based on parameters such as input and output voltages, power transmission requirements, and the switching frequency of the dual active bridge converter. It reflects the magnitude of the current when transmitting the same power.

[0114] Step 104: Determine the current stress surface corresponding to each turns ratio based on the average inductance current stress. Determine the boundary line where any two current stress surfaces intersect based on the power value to be transmitted. Use the boundary line as the critical line for turns ratio switching. Determine the design turns ratio of the transformer based on the critical line. Select the turns ratio from the design turns ratio under each input and output voltage condition.

[0115] In one embodiment, step 104, determining the transformer's design turns ratio based on the critical line, includes:

[0116] Step 1041: Determine the current stress surface corresponding to each average inductor current stress, determine the boundary line where any two current stress surfaces intersect based on the power value to be transmitted, and use the boundary line as the critical line for turns ratio switching.

[0117] Step 1042: Based on the number of turns on the primary upper winding, the primary lower winding, the secondary lower winding, and the secondary upper winding of the high-frequency transformer, determine a set of turns ratios that includes several different turns ratios.

[0118] Step 1043: Using the critical line as the turns ratio switching condition, gradually change the turns ratio of the secondary and primary windings to obtain each turns ratio in a set of turns ratios. At the same time, based on the principle of optimal current stress, calculate the average inductor current stress of each turns ratio in a set of turns ratios under the full range of input and output voltages according to the turns ratio switching condition.

[0119] Step 1044: Take the turns ratio corresponding to the minimum average inductance current stress as the design turns ratio of the transformer.

[0120] It should be noted that, as described in step 103: let the number of turns on the primary winding be N1, the number of turns on the secondary winding be N2, and the number of turns on the secondary winding be N1, and the number of turns on the secondary winding be N2. Since the number of turns on the primary winding and the secondary winding are the same, and the number of turns on the primary winding and the secondary winding are the same, a set of turns ratios for the transformer includes three cases: N1 / (N1+N2), (N1+N2) / (N1+N2), and (N1+N2) / N1. To select a suitable transformer turns ratio, it is necessary to analyze the average inductor current stress of each set of turns ratios under the full range of input and output voltages.

[0121] Therefore, given the power value to be transmitted, at that power level, when U in / U out When the turns ratio is too large, a turns ratio of n = (N1 + N2) / N1 is chosen to reduce current stress. In this case, the current carried on the secondary side of the transformer will be less. To determine when to switch from a turns ratio of 1 to a turns ratio of n = (N1 + N2) / N1, it is necessary to find their boundary, i.e., I. n=1 with I n=(N1+N2) / N1 There exists a boundary line, which represents the condition under which the current stress is equal under these two turns ratios. This curve can be obtained by comparing the current stress formulas, as shown below. Figure 5 As shown. This curve can be used as the switching condition between turns ratio 1 and n = (N1 + N2) / N1, let The boundary line is obtained as follows: . When U in / U out If the current is too small, choose a turns ratio n = N1 / (N1+N2) to reduce current stress. In this case, the primary current of the transformer will be smaller. n=1 with In=N1 / (N1+N2) There exists a boundary line, which can serve as the switching condition for the turns ratio n = N1 / (N1 + N2), let... The boundary line is obtained as follows: The turns ratio distribution regions under different input / output voltage combinations are as follows: Figure 6 As shown.

[0122] Given input voltage range Output voltage range The required power level is P0. Based on the principle of optimal current stress and the turns ratio switching condition, the current stress in the three regions is calculated as follows:

[0123] (18)

[0124] (19)

[0125] (20)

[0126] (twenty one)

[0127] The transformer has three possible turns ratios: N1 / (N1+N2), (N1+N2) / (N1+N2), and (N1+N2) / N1. The range of N2 / N1 is set from 0.1 to 2, with a step size of 0.1. A different secondary to primary turns ratio is assumed for each analysis, and the current stress is calculated for each case. For each N2 / N1 value, the current stress I under the three turns ratios is calculated. a Compare their magnitudes. Select the turns ratio that minimizes current stress as the optimal turns ratio under that voltage condition.

[0128] This invention ensures that the most suitable transformer turns ratio can be selected for each input and output voltage condition under a given power transmission requirement. By designing the turns ratio, the transformer turns ratio can be changed, thereby minimizing current stress and improving the overall efficiency and performance of the converter.

[0129] In summary, the current stress optimization method for a dual active bridge converter provided by this invention introduces a variable turns ratio transformer and a single-pole double-throw relay to achieve dynamic switching of the transformer turns ratio under different input and output voltage conditions. This design can automatically select the optimal turns ratio based on changes in the voltage ratio, achieving low current stress operation within different voltage ranges, thereby significantly reducing current stress. Specifically, by analyzing and calculating the current stress based on a given input and output voltage range and the required power level, the optimal turns ratio is selected. This significantly reduces the conduction current of the inductor and switching transistors under constant power transmission conditions, effectively reducing the current peak in the system and decreasing switching and conduction losses. Simultaneously, the optimized turns ratio switching strategy enables the dual active bridge converter to transmit power with higher efficiency over a wide input and output voltage range. This design significantly improves the system's adaptability and stability under various operating conditions, broadening the converter's application range. Through phase-shift optimization control under triple phase-shift control, the transformer can dynamically adjust the combination of phase shifts D1, D2, and D3 under various voltage ratios and load conditions, further realizing automated optimization control and ensuring minimized current stress in any operating mode. This automatic adjustment feature reduces the complexity of system design and debugging, improves the converter's operating efficiency and overall performance, and meets a wider range of application needs, especially in applications requiring high power density and high efficiency. In summary, this invention, through the combination of flexible turns ratio switching and phase-shift optimization, enables the converter to not only maintain stable and efficient operation under different input and output voltages but also effectively reduce current stress, thereby improving the overall system efficiency and reliability, demonstrating significant technical advantages. For actual voltage variations in different application scenarios, this strategy can ensure that the converter always operates in an optimal current stress state, thereby improving overall system performance.

[0130] The above is a current stress optimization method for a dual active bridge converter provided in the embodiments of the present invention. The following is a current stress optimization system for a dual active bridge converter provided in the embodiments of the present invention.

[0131] Please see Figure 7 The present invention provides a current stress optimization system for a dual active bridge converter, comprising:

[0132] Construction unit 201 is used to construct a dual active bridge converter containing inductance by introducing a transformer with a variable turns ratio;

[0133] Analysis unit 202 is used to analyze the turns ratio design basis of the transformer based on several operating modes of the dual active bridge converter under triple phase shift.

[0134] Calculation unit 203 is used to calculate the average inductor current stress of each group of turns ratios under the full range of input and output voltages of the dual active bridge converter based on the turns ratio design and using the double integration method.

[0135] The optimization unit 204 is used to determine the current stress surface corresponding to each turns ratio based on the average inductor current stress, determine the boundary line where any two current stress surfaces intersect based on the power value to be transmitted, and use the boundary line as the critical line for turns ratio switching. Based on the critical line, the design turns ratio of the transformer is determined, and the turns ratio is selected from the design turns ratio under each input and output voltage condition.

[0136] Furthermore, this embodiment of the invention also provides a current stress optimization device for a dual active bridge converter, the device comprising a processor and a memory:

[0137] The memory is used to store program code and transmit the program code to the processor;

[0138] The processor is used to execute the steps of the dual active bridge converter current stress optimization method as described in the above method embodiments, according to the instructions in the program code.

[0139] Furthermore, this embodiment of the invention also provides a computer-readable storage medium for storing program code, which is used to execute the method described in the above-described method embodiments.

[0140] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0141] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0142] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0143] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0144] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0145] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing current stress in a dual active bridge converter, characterized in that, include: A dual active bridge converter incorporating inductance is constructed by introducing a transformer with a variable turns ratio. Based on the various operating modes of the dual active bridge converter under triple phase shift, the turns ratio design basis of the transformer is analyzed. Based on the turns ratio design criteria, the average inductor current stress of each turns ratio under the full range of input and output voltages of the dual active bridge converter is calculated using the double integral method. The current stress surface corresponding to each turns ratio is determined based on the average inductance current stress. The boundary line where any two current stress surfaces intersect is determined based on the power value to be transmitted. The boundary line is used as the critical line for turns ratio switching. The design turns ratio of the transformer is determined based on the critical line. The turns ratio is selected from the design turns ratio under each input and output voltage condition.

2. The current stress optimization method for a dual active bridge converter according to claim 1, characterized in that, The method of constructing a dual active bridge converter with inductance by introducing a transformer with a variable turns ratio includes: A dual active bridge converter incorporating an inductor is constructed by introducing a transformer and a single-pole double-throw relay, wherein the single-pole double-throw relay is used to change the turns ratio of the transformer.

3. The current stress optimization method for a dual active bridge converter according to claim 2, characterized in that, The transformer is a high-frequency transformer, and both the primary and secondary sides of the high-frequency transformer have double windings.

4. The current stress optimization method for a dual active bridge converter according to claim 1, characterized in that, The analysis of the transformer's turns ratio design basis based on several operating modes of the dual active bridge converter under triple phase shift includes: Several operating modes of the dual active bridge converter under triple phase shift are determined, and a zero-return-power operating mode is selected from several operating modes, wherein the triple phase shift includes phase shift within the primary side, phase shift between the primary and secondary sides, and phase shift within the secondary side. Based on the zero-return-power operating mode under triple phase-shift control, the current characteristics of the dual active bridge converter are analyzed to obtain the peak value of the inductor current, and the transmission power of the zero-return-power operating mode is calculated based on the peak value of the inductor current. The peak inductor current and the transmission power of the zero-return power operating mode are normalized to obtain the normalized peak inductor current and normalized transmission power under triple phase shift. Based on the per-unit inductor current peak value and the per-unit transmission power, and in conjunction with the Lagrange equation, determine the phase shift combination that satisfies the power requirements and minimizes the inductor current peak value for each of the zero-return power operating modes. The transmission power range of the zero-return power operating mode is determined based on the phase shift combination. An expression for the inductor current is constructed based on the transmission power range. Based on the expression for the inductor current, the inductor current stress is determined as the basis for the turns ratio design of the transformer.

5. The current stress optimization method for a dual active bridge converter according to claim 1, characterized in that, The method of calculating the average inductor current stress per turns ratio for the dual active bridge converter under the full range of input and output voltages using the double integral method includes: Calculate the area of ​​the regions corresponding to the input voltage and the output voltage; The inductor current stress in the region is double-integrated to obtain the integral value of the inductor current stress in the region. The average inductor current stress within the range of the input voltage and the output voltage is obtained by dividing the integral value of the inductor current stress in the region by the area of ​​the region.

6. The current stress optimization method for a dual active bridge converter according to claim 3, characterized in that, Determining the design turns ratio of the transformer based on the critical line includes: Based on the number of turns on the primary upper winding, the primary lower winding, the secondary lower winding, and the secondary upper winding of the high-frequency transformer, determine a set of turns ratios that includes several different turns ratios. Using the critical line as the turns ratio switching condition, the turns ratio of the primary and secondary windings is gradually changed to obtain each turns ratio in the set of turns ratios. At the same time, based on the principle of optimal current stress, the average inductor current stress of each turns ratio in the set of turns ratios is calculated under the full range of input and output voltages according to the turns ratio switching condition. The turns ratio corresponding to the minimum average inductance current stress is taken as the design turns ratio of the transformer.

7. The current stress optimization method for a dual active bridge converter according to claim 6, characterized in that, The set of turns ratios includes: N 1 / ( N 1+ N 2), ( N 1+ N 2) / ( N 1+ N 2) and ( N 1+ N 2) / N 1. Three turns ratio scenarios, where the number of turns on the primary winding side of the high-frequency transformer is... N 1. The number of turns on the primary winding side is: N 2. The number of turns on the secondary lower winding side is N 1, and the number of turns on the secondary winding side is N 2.

8. A current stress optimization system for a dual active bridge converter, characterized in that, include: A building block for constructing a dual active bridge converter with inductance by introducing a transformer with a variable turns ratio; The analysis unit is used to analyze the turns ratio design basis of the transformer based on several operating modes of the dual active bridge converter under triple phase shift. The calculation unit is used to calculate the average inductor current stress of each group of turns ratios under the full range of input and output voltages of the dual active bridge converter based on the turns ratio design and using the double integration method. The optimization unit is used to determine the current stress surface corresponding to each turns ratio based on the average inductance current stress, determine the boundary line where any two current stress surfaces intersect based on the power value to be transmitted, and use the boundary line as the critical line for turns ratio switching. Based on the critical line, the design turns ratio of the transformer is determined, and the turns ratio is selected from the design turns ratio under each input and output voltage condition.

9. A current stress optimization device for a dual active bridge converter, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the current stress optimization method for a dual active bridge converter according to any one of the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the current stress optimization method for a dual active bridge converter according to any one of claims 1-7.

Images