A Multi-parameter Safety Region Constraint Design Method and Simulation System for a Dual Active Bridge Converter

Abstract

A multi-parameter safe operating region constraint design method and simulation system for a dual active bridge converter is disclosed. The method includes: determining the key parameters to be designed; designing transmission power constraints to ensure that the dual active bridge converter can still meet the theoretical maximum allowable power output requirement under maximum phase shift conditions; designing current stress constraints to ensure that the high-voltage side current stress and low-voltage side current stress are within the safe operating range of the corresponding switches in the dual active bridge converter; designing steady-state thermal stress constraints to ensure that the effective value of the current of the switches under continuous operation conditions does not exceed the allowable range of the switches; constructing a multi-parameter safe operating region by finding the intersection of the transmission power constraint, current stress constraint, and steady-state thermal stress constraint in the parameter space of the series inductor and the switching frequency of the switches; and then selecting the required parameters within the multi-parameter safe operating region. This invention provides an intuitive and engineering-operable design basis for parameter selection.

Description

Technical Field

[0001] This invention relates to the field of power electronics and power conversion technology, and in particular to a multi-parameter safe region constraint design method and simulation system for a dual active bridge converter. Background Technology

[0002] With the rapid development of new energy power generation, electrochemical energy storage systems, and bidirectional interaction technologies between electric vehicles and the power grid, the demand for bidirectional DC power flow is increasing. Dual active bridge converters, as key power electronic devices for realizing bidirectional energy transfer between DC systems of different voltage levels, are widely used in energy storage interfaces, on-board charging systems for electric vehicles, DC microgrids, and flexible DC distribution systems. Among them, dual active bridge converters employing high-frequency isolation structures combined with phase-shift control strategies have become the mainstream topology in current research and engineering applications due to their high power density, good bidirectional power controllability, and ease of electrical isolation.

[0003] In current engineering practice, the parameter design of dual active bridge converters is usually based on rated power or a single operating condition. For example, the series inductor parameters are selected according to the maximum transmission power requirement, or the switching frequency is determined based on the rated current of the switching transistors. However, in actual operation, dual active bridge converters often need to operate over a wide voltage and power range. Their operating status is not only affected by the transmission power requirement, but also closely related to various factors such as the high and low voltage levels, transformer turns ratio, and control strategies.

[0004] Under conditions such as high and low voltage fluctuations, sudden power changes, or bidirectional power switching, the voltage transformation ratio of a dual active bridge converter is prone to deviate from its rated value, leading to significant transient circulating currents. These transient circulating currents significantly increase the peak value of the series inductor current, causing the switching transistors to experience substantial current stress for a short period. If these transient conditions are not adequately constrained during the parameter design phase, it may result in frequent overcurrent protection trips of the switching transistors, or even transistor failure or a decrease in system reliability.

[0005] Furthermore, under long-term steady-state operating conditions, the effective value of the series inductor current directly determines the thermal stress level of the switching transistor. If parameter design is based solely on peak current or rated power, the impact of the effective current value on the junction temperature and lifespan of the switching transistor can easily be overlooked, thus introducing potential thermal reliability risks during long-term operation. Therefore, how to simultaneously consider transient current stress and steady-state current effective value constraints during the parameter design stage has become an important issue in the engineering design of dual active bridge converters.

[0006] Existing research mostly focuses on parameter analysis of dual active bridge converters under single constraints, lacking a systematic design method that can uniformly describe multiple constraints such as transmission power capability, current stress, and RMS current value. A clear description of the multi-parameter safe operating region has also not yet been established. This, to some extent, restricts the safety and reliability of dual active bridge converters under complex operating conditions. Summary of the Invention

[0007] This invention provides a multi-parameter safe region constraint design method and simulation system for a dual active bridge converter to solve the technical problems mentioned in the background.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: This invention provides a multi-parameter safe region constraint design method for a dual active bridge converter, comprising the following steps: S1. Determine the key parameters to be designed, including the series inductor on the dual active bridge converter. and the switching frequency of the switching transistor ; S2, Design for series inductors With the switching frequency of the switching transistor The combined applied transmission power constraints ensure that the dual active bridge converter can still meet the theoretical maximum allowable power under maximum phase shift conditions. The output requirements; S3, Design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter; S4, Design for series inductors With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective value of the current of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor. S5. Based on transmission power constraints, current stress constraints, and steady-state thermal stress constraints, in series inductors... With the switching frequency of the switching transistor The intersection of parameters within the parameter space is calculated to construct a multi-parameter safe working region, and then the required parameters are selected within the multi-parameter safe working region.

[0009] Furthermore, step S2 specifically includes the following steps: S21. In the single-phase shift control strategy and the actual transformer turns ratio k Based on the formula =1, a power transfer model for a dual active bridge converter is established. S22. By analyzing the power transfer model of the dual active bridge converter, the maximum output power of the dual active bridge converter is calculated. The minimum value; S23. Based on the rated transmission power of the dual active bridge converter A margin factor is introduced to calculate the theoretical maximum allowable power of the dual active bridge converter. That is, maximum output power The maximum value; S24. Utilizing the maximum output power of the dual active bridge converter The minimum value and the theoretical maximum allowable power of the dual active bridge converter Design for series inductors With the switching frequency of the switching transistor The combination of these factors applies a transmission power constraint to ensure that the dual active bridge converter can still meet the theoretical maximum allowable power requirement under maximum phase shift conditions. The output requirements.

[0010] Furthermore, the power transfer model of the dual active bridge converter in S21 is expressed as follows: ; in, This indicates the transmission power of the dual active bridge converter; Indicates a shift compared to; This represents the high-voltage side voltage of the dual active bridge converter; This indicates the low-voltage side voltage of the dual active bridge converter; This indicates the preset turns ratio of the transformer; The maximum output power of the dual active bridge converter in S22 The expression for the minimum value is: ; in, This represents the minimum value of the high-voltage side voltage of the dual active bridge converter; This represents the minimum value of the low-voltage side voltage of the dual active bridge converter.

[0011] Furthermore, step S3 specifically includes the following steps: S31, reduce the low-voltage side voltage U 2. The voltage value converted to the high-voltage side, i.e. U 2 ’ =n T U 2. Then, based on this, a current stress model incorporating the effects of transient circulating currents is constructed; whereby... U 2 ’ Indicates the low-voltage side terminal voltage U2. The terminal voltage value converted to the high-voltage side; S32. Calculate the corresponding shift ratio based on the power transfer model of the dual active bridge converter. The value of ; S33, compare the corresponding shifts Substituting the value of into the current stress model in S31, a new current stress model is obtained. S34. Current stress in the new current stress model , Calculate the transmission power separately. High voltage side voltage U 1. Low-voltage side terminal voltage U The partial derivatives of 2 are used to obtain the current stress. , Partial derivative model; S35, By analyzing current stress , The partial derivative model was used to calculate the current stress. , The maximum value; S36, Utilizing Current Stress , The maximum value, design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter.

[0012] Furthermore, the expression for the current stress model in S31 is as follows: ; in, Indicates the actual turns ratio of the transformer When the value is less than 1, the current stress of the dual active bridge converter; Indicates the actual turns ratio of the transformer Current stress in dual active bridge converters when the value is greater than or equal to 1. The S32 shift compared to The formula for calculation is: ; The expression for the new current stress model in S33 is as follows: ; Current stress in S35 , The formula for calculating the maximum value is: ; in, Indicates current stress The maximum value; Indicates current stress The maximum value; , These represent the voltages at the high-voltage side. U 1. Low-voltage side terminal voltage U The maximum value of 2; Furthermore, step S4 specifically includes the following steps: S41. Establish a constraint model based on the effective value of the series inductor current; S42, By analyzing the constraint model based on the effective value of the series inductor current and the relationship between the effective value of the series inductor current and the transmission power... High voltage side voltage U 1. Series inductor The relationship between these factors is used to calculate the maximum effective value of the series inductor current. S43. Using the maximum effective value of the series inductor current, design a series inductor... With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective current value of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor.

[0013] Furthermore, the expression for the constraint model in S41 is: ; in, This represents the effective value of the series inductor current within one resonant cycle. The formula for calculating the maximum effective value of the series inductor current in S42 is: ; in, This represents the maximum effective value of the series inductor current.

[0014] Furthermore, the expression for the transmission power constraint in S2 is as follows: ; in, Indicates the margin coefficient; The current stress constraint in S3 is: ; I stress ≥ μ ·max( I M1 , I M2 ); in, μ This is the margin coefficient; express , The maximum of the two; where I stress Indicates the maximum allowable current stress of the switching transistor; The expression for the steady-state thermal stress constraint in S4 is as follows: ; in, σ This is the current RMS margin factor. This is the effective current value that the high-voltage side switching transistor can withstand to operate for a time period not lower than the first set time. This refers to the effective current value that the low-voltage side switching transistor can withstand to operate for a time not less than the first set time.

[0015] Furthermore, the step S5 is followed by the following steps: S6. Select multiple groups within the multi-parameter safe working area ( , The parameters are combined, and the dynamic response, steady-state performance, current stress and efficiency of the dual active bridge converter under each set of parameters are compared and verified through offline simulation and / or semi-physical real-time simulation platforms to confirm the effectiveness of the boundary of the safe operating area of ​​the multi-parameter converter.

[0016] In another aspect, the present invention provides a simulation system, comprising: The host computer constructs a multi-parameter safe operating region by executing the multi-parameter safe region constraint design method for the dual active bridge converter described above, and selects the optimal parameters of the dual active bridge converter; these parameters include at least the series inductors on the dual active bridge converter. and the switching frequency of the switching transistor The optimal value; The hardware-in-the-loop real-time simulation platform is connected to the host computer via a local area network and is used to simulate and verify dual active bridge converters with parameters selected within the multi-parameter safe operating range. The controller is electrically connected to the host computer via USB serial port. It is used to generate phase-shift control door opening and closing signals and to interact with the hardware-in-the-loop real-time simulation platform through the I / O interface. An oscilloscope is electrically connected to a hardware-in-the-loop real-time simulation platform via an I / O interface to acquire simulated voltage and current waveforms.

[0017] The beneficial effects of this invention are: 1. This invention proposes a multi-parameter safety region constraint design method for dual active bridge converters. By uniformly modeling and analyzing transmission power constraints, current stress constraints, and steady-state thermal stress constraints, it avoids the problem of traditional parameter design methods relying on only a single index and realizes a systematic characterization of the safety operation boundary of dual active bridge converters.

[0018] 2. This invention achieves unified constraint analysis of the transient and steady-state operating characteristics of dual active bridge converters by using a current stress model that includes the influence of transient circulating current and combining it with current stress constraints under steady-state operating conditions, thereby improving the applicability and reliability of parameter design under complex operating conditions.

[0019] 3. This invention constructs a multi-parameter safe operating region under multiple constraints within the parameter space formed by the series inductor and the switching frequency, providing an intuitive, clear, and engineering-operable design basis for the parameter selection of dual active bridge converters, which helps to improve parameter design efficiency and reduce engineering implementation risks.

[0020] 4. The multi-parameter safety area constraint design method provided by this invention is applicable to a variety of applications such as energy storage interfaces, electric vehicle on-board chargers, DC microgrids and flexible DC power distribution systems, and has a wide range of applications. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the dual active bridge converter in this invention; Figure 2 This is a graph showing the relationship between maximum output power and series inductance in an embodiment of the present invention. Figure 3 Current stress in embodiments of the present invention Curve showing the relationship between the series inductance and the inductance. Figure 4 Current stress in embodiments of the present invention Curve showing the relationship between the series inductance and the inductance. Figure 5 This is a graph showing the relationship between the maximum effective value of the series inductor current and the series inductance in an embodiment of the present invention. Figure 6 This is a schematic diagram of the safe operating region of the dual active bridge converter in an embodiment of the present invention; Figure 7 This is a low-voltage side voltage curve diagram in an embodiment of the present invention; Figure 8 This is a current curve of the series inductor in an embodiment of the present invention; Figure 9 This is an efficiency curve of the dual active bridge converter in an embodiment of the present invention; Figure 10 This is a schematic diagram of the simulation system in an embodiment of the present invention; Figure 11 The waveforms of the low-voltage side voltage and series inductor current at test point A during forward operation of the dual active bridge converter. Figure 12 The waveforms of the low-voltage side voltage and series inductor current at test point B during forward operation of the dual active bridge converter. Figure 13 The waveforms of the low-voltage side voltage and series inductor current at test point C during forward operation of the dual active bridge converter. Figure 14 The waveforms of the low-voltage side voltage and series inductor current at test point A when the dual active bridge converter is running in reverse. Figure 15 The waveforms of the low-voltage side voltage and series inductor current at test point B during reverse operation of the dual active bridge converter. Figure 16 The waveforms of the low-voltage side voltage and series inductor current at test point C during reverse operation of the dual active bridge converter. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many other different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] Regarding the issue mentioned in the background section, existing parameter design methods for dual active bridge converters only consider a single constraint and are insufficient to comprehensively characterize the safe operating boundary. Furthermore, dual active bridge converters (DABs) have the following shortcomings: Series inductor and switching frequency of the switching transistor This is related to the transmission efficiency of the dual active bridge converter, the current stress of the high- and low-voltage side switches, and the effective values ​​of the high- and low-voltage side currents under normal operating conditions. If the series inductor... With the switching frequency of the switching transistor If the value is too large, the dual active bridge converter may not reach the expected output power; conversely, if the series inductor is too small... and switching frequency of the switching transistor If the value is too small, it may increase the circulating current in the dual active bridge converter, especially when the voltage ratio is mismatched, leading to excessive current stress and potentially causing the dual active bridge converter to break down. Therefore, in order to ensure that the dual active bridge converter operates within the expected safe operating range, a series inductor is used. and switching frequency of the switching transistor The design needs to meet the following requirements: 1. Under maximum phase shift conditions, the dual active bridge converter can still meet the theoretical maximum allowable power. The output requirements; 2. High-voltage side current stress Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter; 3. The effective value of the current of the switching transistor under continuous operating conditions shall not exceed the allowable range of the switching transistor.

[0025] To address the aforementioned issues, this invention proposes a multi-parameter safe operating region constraint design method for dual active bridge converters. By modeling and analyzing the key operating parameters of the dual active bridge converter, and comprehensively considering multiple safety constraints such as transmission power, transient current stress, and steady-state current RMS value within the parameter space, a multi-parameter safe operating region satisfying these multiple safety constraints is constructed. This multi-parameter safe operating region clearly defines the safe operating boundary of the dual active bridge converter, thereby improving the scientific rigor and engineering applicability of the parameter design. Specifically: Reference Figure 1 This application provides a multi-parameter safe region constraint design method for a dual active bridge converter, including the following steps: S1. Determine the key parameters to be designed, including the series inductor on the dual active bridge converter. and the switching frequency of the switching transistor ; S2, Design for series inductors With the switching frequency of the switching transistor The combined applied transmission power constraints ensure that the dual active bridge converter can still meet the theoretical maximum allowable power under maximum phase shift conditions. The output requirements; S3, Design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter; S4, Design for series inductors With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective value of the current of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor; the allowable range of the switching transistor refers to the allowable range of the effective value of the continuous operating current of the switching transistor, which is generally the parameter on the factory nameplate. S5. Based on the combined constraints of transmission power, current stress, and steady-state thermal stress, a total constraint module is obtained. Then, the total constraint module is connected in series with an inductor. With the switching frequency of the switching transistor The intersection of parameters within the parameter space is calculated to construct a multi-parameter safe working region, and then the required parameters are selected within the multi-parameter safe working region.

[0026] In some embodiments, S2 specifically includes the following steps: S21. In the single-phase shift control strategy and the actual transformer turns ratio k Based on the formula =1, a power transfer model for a dual active bridge converter is established. S22. By analyzing the power transfer model of the dual active bridge converter, the maximum output power of the dual active bridge converter is calculated. The minimum value; S23. Based on the rated transmission power of the dual active bridge converter A margin factor is introduced to calculate the theoretical maximum allowable power of the dual active bridge converter. That is, maximum output power The maximum value; S24. Utilizing the maximum output power of the dual active bridge converter The minimum value and the theoretical maximum allowable power of the dual active bridge converter Design for series inductors With the switching frequency of the switching transistor The combination of these factors applies a transmission power constraint to ensure that the dual active bridge converter can still meet the theoretical maximum allowable power requirement under maximum phase shift conditions. The output requirements.

[0027] In some embodiments, the power transfer model of the dual active bridge converter in S21 is expressed as follows: ; in, This indicates the transmission power of the dual active bridge converter; Indicates a shift compared to; This represents the high-voltage side voltage of the dual active bridge converter; This indicates the low-voltage side voltage of the dual active bridge converter; This indicates the preset turns ratio of the transformer; The maximum output power of the dual active bridge converter in S22 The expression for the minimum value is: ; in, This represents the minimum value of the high-voltage side voltage of the dual active bridge converter; This represents the minimum value of the low-voltage side voltage of the dual active bridge converter.

[0028] The maximum output power in S23 The expression for the maximum value is as follows: ; Among them, the shift compared =0.5.

[0029] In some embodiments, S3 specifically includes the following steps: S31. Under stable operating conditions, the power transmission model of the dual active bridge converter gives the actual transformer turns ratio. k The transformer's turns ratio is stable at 1, but when the terminal voltage fluctuates, the actual turns ratio of the transformer will inevitably change. k In cases where the value is not equal to 1, a large circulating current will appear inside the dual active bridge converter, impacting the components within the converter. When the impact exceeds the maximum stress that the switching transistors can withstand, it will cause damage to the switching transistors, ultimately leading to the collapse of the dual active bridge converter. Therefore, to ensure the stable operation of the dual active bridge converter and to keep the switching transistors operating within a safe stress range, it is necessary to control the transients during the control process of the dual active bridge converter. k ≠1) The working conditions are analyzed in detail, as follows: Low voltage side voltage U 2. The voltage value converted to the high-voltage side, i.e. U 2 ’ =n T U 2. Then, based on this, a current stress model incorporating the effects of transient circulating currents is constructed; whereby... U 2 ’ Indicates the low-voltage side terminal voltage U 2. The terminal voltage value converted to the high-voltage side; S32. Calculate the corresponding shift ratio based on the power transfer model of the dual active bridge converter. The value of ; S33, compare the corresponding shifts Substituting the value of into the current stress model in S31, a new current stress model is obtained. S34. Current stress in the new current stress model , Calculate the transmission power separately. High voltage side voltage U 1. Low-voltage side terminal voltageU The partial derivatives of 2 are used to obtain the current stress. , Partial derivative model; S35, By analyzing current stress , The partial derivative model was used to calculate the current stress. , The maximum value; S36, Utilizing Current Stress , The maximum value, design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter.

[0030] In some embodiments, the expression for the current stress model in S31 is as follows: ; in, Indicates the actual turns ratio of the transformer When the value is less than 1, the current stress of the dual active bridge converter; current stress refers to the current flowing through the series inductor. The maximum current; Indicates the actual turns ratio of the transformer Current stress in a dual active bridge converter when greater than or equal to 1; actual transformer turns ratio. The formula for calculation is: ; in, n Indicates the transformer turns ratio; The S32 shift compared to The formula for calculation is: ; The expression for the new current stress model in S33 is as follows: ; Current stress in S34 The partial derivative model is as follows: ; By observing current stress From the partial derivative model, it can be seen that the current stress With transmission power It increases with the increase of the voltage on the high-voltage side. U As 1 increases, it decreases, therefore in = Pmax and U 1 =U 1min At that time, current stress Get the maximum value . The partial derivative model is similar to the above formula, and will not be explained in detail below.

[0031] Current stress in S35 , The formula for calculating the maximum value is: ; in, Indicates current stress The maximum value; Indicates current stress The maximum value; , These represent the voltages at the high-voltage side. U 1. Low-voltage side terminal voltage U The maximum value of 2; In some embodiments, S4 specifically includes the following steps: S41. Establish a constraint model based on the effective value of the series inductor current; S42, By analyzing the constraint model based on the effective value of the series inductor current and the relationship between the effective value of the series inductor current and the transmission power... High voltage side voltage U 1. Series inductor The relationship between these factors is used to calculate the maximum effective value of the series inductor current. Specifically, after squaring the constraint model based on the effective value of the series inductor current, a partial derivative operation is performed to obtain the partial derivative model of the effective value of the series inductor current, as follows: ; By observing the partial derivative model of the effective value of the series inductor current, we can see that the square of the effective value of the inductor current... With the transmission power of the dual active bridge converter The voltage increases with the increase of the high-voltage side voltage. U As 1 increases, the effective value of the series inductor current decreases; therefore, the maximum value of the effective value of the series inductor current is at the output power. Maximum and high voltage side voltage U The minimum value is obtained, and then the maximum effective value of the series inductor current is calculated using the above information.

[0032] S43. Using the maximum effective value of the series inductor current, design a series inductor... With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective current value of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor.

[0033] In some embodiments, the expression for the constraint model in S41 is: ; in, This represents the effective value of the series inductor current within one resonant cycle. The formula for calculating the maximum effective value of the series inductor current in S42 is: ; in, This represents the maximum effective value of the series inductor current.

[0034] In some embodiments, the expression for the transmission power constraint in S2 is as follows: ; in, Indicates the margin coefficient; The current stress constraint in S3 is: ; I stress ≥ μ ·max( I M1 , I M2 ); in, μ This is the margin coefficient. μ The value is generally taken as 1.5 to 2; Indicates current stress The maximum value; I stress Indicates the maximum allowable current stress of the switching transistor; The expression for the steady-state thermal stress constraint in S4 is as follows: ; in, σ This refers to the current effective value margin factor. σ The value is generally taken as 1.5 to 3; This represents the effective current that the high-voltage side switching transistor can withstand during long-term operation. This ensures that the low-voltage side switching transistor can withstand an effective current value that is not lower than the current it can withstand during long-term operation.

[0035] In some embodiments, the expression for the total constraint module in S5 is as follows: .

[0036] In some embodiments, the following steps are further included after step S5: S6. Select multiple groups within the multi-parameter safe working area ( , The parameters are combined, and the dynamic response, steady-state performance, current stress and efficiency of the dual active bridge converter under each set of parameters are compared and verified through offline simulation and / or semi-physical real-time simulation platforms to confirm the effectiveness of the boundary of the safe operating area of ​​the multi-parameter converter.

[0037] In some embodiments, the following steps are further included after S1 or between S5 and S6: Other design parameters of the dual active bridge converter are determined based on the voltage level and capacity range of the connected power system, including the high-voltage side voltage of the dual active bridge converter. U 1. Low-voltage side terminal voltage U 2. Rated transmission power and the transformer's preset turns ratio .

[0038] The invention will be further illustrated by the following case studies: The block diagram of the dual active bridge converter is as follows: Figure 1 As shown, the parameters that need to be designed for a dual active bridge converter include the high-voltage side voltage. U 1. Low-voltage side terminal voltage U 2. Rated transmission power and the transformer's preset turns ratio Series inductor Switching frequency of switching transistor .

[0039] High-voltage side voltage of dual active bridge converter U 1. The AC output is supplied by the AC / DC converter, and its AC side is directly connected to the 220V / 50Hz power grid. To improve system operating efficiency and reduce harmonic coefficients, the high-voltage side voltage is set... U 1 represents a typical value of 400V. The low-voltage side voltage of the dual active bridge converter... U 2. Power is supplied by the vehicle's onboard battery, typically consisting of multiple 6V or 12V batteries connected in series, with a typical value of 48V. Given the miniaturization and lightweight characteristics of vehicles, the rated transmission power... No need to choose an excessively large value; select 1.5kW. The transformer's preset turns ratio. It is generally determined based on the voltage ratio of the high-voltage side and the low-voltage side, which is equivalent to the turns ratio of the coils on both sides.

[0040] First, determine the safe transmission power zone. (Refer to...) Figure 2 , Figure 2Based on the maximum output power of the dual active bridge converter The expression for the minimum value is given at different switching frequencies of the switching transistor. Below, series inductor The curve showing the relationship between the maximum and minimum output power of the dual active bridge converter. Figure 2 As can be seen from this, with the series inductance Increase, maximum output power The minimum value gradually decreases when the series inductance... When less than a certain value, Only then will it exceed the theoretical maximum allowable power of the dual active bridge converter. This area is defined as the Effective Area (EA).

[0041] Based on this, the safe zone for current stress is determined. (Refer to...) Figure 3 and Figure 4 , Figure 3 and Figure 4 Based on current stress constraints, the switching frequencies of different switching transistors are given. Under the condition of considering the margin factor, the current stress is... , With series inductor The relationship curve is different from that of output power. P Current stress With series inductor The relationship is not monotonic, and it also applies when series inductors are connected. When the current is small, the current stress generated during the operation of the dual active bridge converter will exceed the current limit of the switching transistor, and the design requirements will only be met within a certain range.

[0042] Subsequently, the safe range for the effective current value is determined. (Refer to...) Figure 5 , Figure 5 The figure shows the effective current value on the high-voltage side under different switching conditions. With series inductor L The relationship curve shows that when the series inductor L When the current is small, the magnitude of the current is related to the series inductance. L Positive correlation, when series inductors L When the current exceeds a certain value, the current magnitude is negatively correlated with the inductance value, and the steady-state thermal stress constraint is only satisfied within a certain region. Similarly, regarding the low-voltage side current and series inductance... L The relationship curve can also be generated according to the above process.

[0043] By finding the intersection of the aforementioned regions, the safe operating region of the dual active bridge converter is determined. Therefore, combined with the overall constraint model, the maximum allowable current stress of the switching transistors is determined. Take 100A, the effective value of the series inductor current. Taking 65A, we can finally obtain Figure 6 The series inductor shown L With the switching frequency of the switching transistor The relationship curve is shown, where the gray part represents the safe operating region of the dual active bridge converter.

[0044] exist Figure 6 Within the safe operating area shown, test point A (50μH, 20kHz) was selected. Outside the safe operating area, control test points B (5μH, 10kHz) and C (150μH, 40kHz) were selected respectively. A simulation model of the dual active bridge converter was built in MATLAB (Matrix Lab), and the above three sets of experimental parameters were substituted into the simulation experiment.

[0045] Under full load conditions, the corresponding low-voltage side voltage curves at each test point are as follows: Figure 7 As shown, under the parameters shown at test point A, the output of the dual active bridge converter stabilizes at 48V within 5ms, and the ripple is controlled within ±2%, which is an ideal experimental result. Test point B does not meet the current stress constraint, and the voltage ripple on the low-voltage side is large due to the low switching frequency. Test point C does not meet the power constraint, so the voltage on the low-voltage side cannot stabilize at 48V.

[0046] The steady-state current of the series inductor is as follows Figure 8 As shown, under the parameters indicated at test point A, the peak current is 17.64A, which is less than the current stress of the switching transistor. When the dual active bridge converter starts up, the series inductor... L The current it withstands is close to the peak-to-peak value of the steady-state current, which is still within the stable operating range of the switching transistor, indicating a reasonable design. Under the parameters shown at test point B, the peak-to-peak current value of 100.2A exceeds the current stress of the switching transistor, which will lead to damage to the switching transistor.

[0047] Substitute the parameters shown at test point A within the safe zone into the simulation model of the dual active bridge converter, change the load, record the efficiency of the dual active bridge converter under different load conditions, and plot the corresponding relationship curves, as shown below. Figure 9 As shown, the dual active bridge converter achieves its highest efficiency (96.2%) under full load, but its efficiency drops rapidly when the load falls below 750W. Based on these experimental results, the design meets expectations.

[0048] In another aspect, the present invention provides a simulation system, comprising: The host computer constructs a multi-parameter safe operating region by executing the multi-parameter safe region constraint design method for the dual active bridge converter described above, and selects the optimal parameters of the dual active bridge converter; these parameters include at least the series inductors on the dual active bridge converter. and the switching frequency of the switching transistor The optimal value; The hardware-in-the-loop real-time simulation platform is connected to the host computer via a local area network and is used to simulate and verify dual active bridge converters with parameters selected within the multi-parameter safe operating range. The controller is electrically connected to the host computer via USB serial port. It is used to generate phase-shift control door opening and closing signals and to interact with the hardware-in-the-loop real-time simulation platform through the I / O interface. An oscilloscope is electrically connected to a hardware-in-the-loop real-time simulation platform via an I / O interface to acquire simulated voltage and current waveforms.

[0049] Specifically, the construction is as follows Figure 10 The simulation system shown is used for hardware-in-the-loop simulation and rapid prototyping. The Simulink model of the dual active bridge converter hardware circuit is imported into a hardware-in-the-loop real-time simulation platform. An external STM32G474 main control chip (i.e., controller) is connected, and an internal SPS single-phase shift control algorithm is written to output 8 PWM control signals. These signals are connected to the PXI chassis via a DIO digital signal interface board as switching control signals for the dual active bridge converter hardware topology. Simultaneously, a 12-bit deep AD module is used to acquire the low-voltage side voltage of the simulation model of the dual active bridge converter. The sampling frequency is set to 170kHz, and the voltage range is 0-3.6V. The low-voltage side voltage and series inductor current of the simulated main circuit in the PXI chassis are output to an oscilloscope for observation via an AO analog signal interface board.

[0050] First, a forward operation test of the dual active bridge converter was conducted, i.e., power was transferred from the 400V DC bus to the 48V side. Since the external controller's AD acquisition range is 0~3.6V, and the PXI host's simulated low-voltage side voltage range is -10V~10V, the low-voltage side voltage was... U out Multiply by a factor of 1 / 24, inductor current I L Multiply by a coefficient of 0.1, select test point A (50μH, 20kHz), test point B (5μH, 20kHz), and test point C (150μH, 20kHz), and finally obtain three sets. U out , I L Waveform as Figures 11 to 13 As shown.

[0051] The semi-physical simulation results show that the low-voltage side voltage at test point A is stable at 48V, and the peak inductor current is around 20A, which is less than the stress on the switching transistor and meets the design requirements. The low-voltage side voltage at test point B is also stable at 48V, but the peak-to-peak inductor current exceeds 80A. When the dual active bridge converter starts up, the starting current significantly exceeds the stress on the switching transistor, which will lead to transistor damage. At test point C, due to the series inductor…L If the voltage is too high, the output power constraint cannot be met, and the low-voltage side voltage cannot reach 48V.

[0052] Next, a reverse operation test of the dual active bridge converter was conducted, in which power was fed back from the 48V energy storage system to the 400V DC bus. The output value of the low-voltage side terminal voltage was then measured. U out Multiply by a factor of 1 / 200, inductor current I L Multiply by a coefficient of 0.1 to get three sets. U out , I L Waveform as Figures 14 to 16 As shown.

[0053] It can be observed that the low-voltage side voltage at test point A is stable at 400V, and the peak-to-peak current does not exceed 80A, which is lower than the peak-to-peak current of 100A at test point B, indicating greater safety. In contrast, the low-voltage side voltage at test point C cannot be stabilized at 400V, consistent with the theoretical derivation above. In conclusion, test point A, located within the safe operating area, meets the design requirements.

[0054] Through the above implementation methods, the safe operating boundaries of the dual active bridge converter can be clearly defined during the parameter design stage, and the design results can be quickly verified by combining simulation with semi-physical real-time simulation verification, thereby providing a reliable basis for the engineering application of the dual active bridge converter.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-parameter safety region constraint design method for a dual active bridge converter, characterized in that, Includes the following steps: S1. Determine the key parameters to be designed, including the series inductor on the dual active bridge converter. and the switching frequency of the switching transistor ; S2, Design for series inductors With the switching frequency of the switching transistor The combined applied transmission power constraints ensure that the dual active bridge converter can still meet the theoretical maximum allowable power under maximum phase shift conditions. The output requirements; S3, Design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter; S4, Design for series inductors With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective value of the current of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor. S5. Based on transmission power constraints, current stress constraints, and steady-state thermal stress constraints, in series inductors... With the switching frequency of the switching transistor The intersection of parameters within the parameter space is calculated to construct a multi-parameter safe working region, and then the required parameters are selected within the multi-parameter safe working region.

2. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 1, characterized in that, S2 specifically includes the following steps: S21. In the single-phase shift control strategy and the actual transformer turns ratio k Based on the formula =1, a power transfer model for a dual active bridge converter is established. S22. By analyzing the power transfer model of the dual active bridge converter, the maximum output power of the dual active bridge converter is calculated. The minimum value; S23. Based on the rated transmission power of the dual active bridge converter A margin factor is introduced to calculate the theoretical maximum allowable power of the dual active bridge converter. That is, maximum output power The maximum value; S24. Utilizing the maximum output power of the dual active bridge converter The minimum value and the theoretical maximum allowable power of the dual active bridge converter Design for series inductors With the switching frequency of the switching transistor The combination of these factors applies a transmission power constraint to ensure that the dual active bridge converter can still meet the theoretical maximum allowable power requirement under maximum phase shift conditions. The output requirements.

3. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 2, characterized in that, The power transfer model of the dual active bridge converter in S21 is expressed as follows: ； in, This indicates the transmission power of the dual active bridge converter; Indicates a shift compared to; This represents the high-voltage side voltage of the dual active bridge converter; This indicates the low-voltage side voltage of the dual active bridge converter; This indicates the preset turns ratio of the transformer; The maximum output power of the dual active bridge converter in S22 The expression for the minimum value is: ； in, This represents the minimum value of the high-voltage side voltage of the dual active bridge converter; This represents the minimum value of the low-voltage side voltage of the dual active bridge converter.

4. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 3, characterized in that, S3 specifically includes the following steps: S31, reduce the low-voltage side voltage U 2. The voltage value converted to the high-voltage side, i.e. U 2 ’ =n T U 2. Then, based on this, a current stress model incorporating the effects of transient circulating currents is constructed; whereby... U 2 ’ Indicates the low-voltage side terminal voltage U 2. The terminal voltage value converted to the high-voltage side; S32. Calculate the corresponding shift ratio based on the power transfer model of the dual active bridge converter. The value of ; S33, compare the corresponding shifts Substituting the value of into the current stress model in S31, a new current stress model is obtained. S34. Current stress in the new current stress model , Calculate the transmission power separately. High voltage side voltage U 1. Low-voltage side terminal voltage U The partial derivatives of 2 are used to obtain the current stress. , Partial derivative model; S35, By analyzing current stress , The partial derivative model was used to calculate the current stress. , The maximum value; S36, Utilizing Current Stress , The maximum value, design for series inductors With the switching frequency of the switching transistor The combined applied current stress constraint is used to reduce the current stress on the high-voltage side. Low-voltage side current stress Within the safe operating range of the corresponding switching transistor in the dual active bridge converter.

5. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 4, characterized in that, The expression for the current stress model in S31 is as follows: ； in, Indicates the actual turns ratio of the transformer When the value is less than 1, the current stress of the dual active bridge converter; Indicates the actual turns ratio of the transformer Current stress in dual active bridge converters when the value is greater than or equal to 1. The S32 shift compared to The formula for calculation is: ； The expression for the new current stress model in S33 is as follows: ； Current stress in S35 , The formula for calculating the maximum value is: ； in, Indicates current stress The maximum value; Indicates current stress The maximum value; , These represent the voltages at the high-voltage side. U 1. Low-voltage side terminal voltage U The maximum value of 2.

6. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 5, characterized in that, S4 specifically includes the following steps: S41. Establish a constraint model based on the effective value of the series inductor current; S42, By analyzing the constraint model based on the effective value of the series inductor current and the relationship between the effective value of the series inductor current and the transmission power... High voltage side voltage U 1. Series inductor The relationship between these factors is used to calculate the maximum effective value of the series inductor current. S43. Using the maximum effective value of the series inductor current, design a series inductor... With the switching frequency of the switching transistor The combination of steady-state thermal stress constraints ensures that the effective current value of the switching transistor under continuous operating conditions does not exceed the allowable range of the switching transistor.

7. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 6, characterized in that, The expression for the constraint model in S41 is: ； in, This represents the effective value of the series inductor current within one resonant cycle. The formula for calculating the maximum effective value of the series inductor current in S42 is: ； in, This represents the maximum effective value of the series inductor current.

8. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 7, characterized in that, The expression for the transmission power constraint in S2 is as follows: ； in, Indicates the margin coefficient; The current stress constraint in S3 is: ； I stress ≥ μ ·max( I M1 , I M2 ); in, μ This is the margin coefficient; express , The maximum of the two; where I stress Indicates the maximum allowable current stress of the switching transistor; The expression for the steady-state thermal stress constraint in S4 is as follows: ； in, σ This is the current RMS margin factor. This is the effective current value that the high-voltage side switching transistor can withstand to operate for a time period not lower than the first set time. This refers to the effective current value that the low-voltage side switching transistor can withstand to operate for a time not less than the first set time.

9. The multi-parameter safe region constraint design method for a dual active bridge converter according to claim 1, characterized in that, Following step S5, the following steps are also included: S6. Select multiple groups within the multi-parameter safe working area ( , The parameters are combined, and the dynamic response, steady-state performance, current stress and efficiency of the dual active bridge converter under each set of parameters are compared and verified through offline simulation and / or semi-physical real-time simulation platforms to confirm the effectiveness of the boundary of the safe operating area of ​​the multi-parameter converter.

10. A simulation system, characterized in that, include: The host computer constructs a multi-parameter safe operating region by executing the multi-parameter safe region constraint design method for the dual active bridge converter according to any one of claims 1 to 9, and selects the optimal parameters of the dual active bridge converter; including at least the series inductor on the dual active bridge converter. and the switching frequency of the switching transistor The optimal value; The hardware-in-the-loop real-time simulation platform is connected to the host computer via a local area network and is used to simulate and verify dual active bridge converters with parameters selected within the multi-parameter safe operating range. The controller is electrically connected to the host computer via USB serial port. It is used to generate phase-shift control door opening and closing signals and to interact with the hardware-in-the-loop real-time simulation platform through the I / O interface. An oscilloscope is electrically connected to a hardware-in-the-loop real-time simulation platform via an I / O interface to acquire simulated voltage and current waveforms.

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