Active thermal management control method for three-phase dual-active bridge DC-DC converter based on SiC device

Abstract

The invention discloses an active thermal management control method for a three-phase dual-active bridge DC-DC converter based on a SiC device. The method comprises the following steps: step 1, carrying out loss analysis on the three-phase dual-active bridge DC-DC converter; step 2, respectively establishing a Foster thermal model of the SiC MOSFET and a Foster thermal model of the three-phase high-frequency transformer; and step 3, performing active thermal management on the three-phase dual-active bridge DC-DC converter. Compared with a traditional single physical heat dissipation method, the method has the advantages that the junction temperature of the SiC MOSFET can be reduced on the basis of physical heat dissipation, so that the overall operation efficiency is effectively improved, the service life of the SiC device of the device can be prolonged, and the reliability of the system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of power conversion and relates to an active thermal management control method for a three-phase dual active bridge DC-DC converter. Background Art

[0002] The development of silicon carbide (SiC) semiconductor devices, one of the representatives of the third generation of power semiconductors, has experienced significant progress, especially in the past two decades. Since SiC MOSFET has the characteristics of high voltage resistance, high efficiency, low loss and high temperature resistance, it is often used in high temperature environments. However, temperature is a key factor affecting the service life of power devices. In order to improve the operating efficiency and service life of the device, it is crucial to perform thermal management of the power device on the premise of accurately obtaining temperature data.

[0003] The three-phase dual-active-bridge (3p-DAB) DC converter has the advantages of high unit power density, soft switching operation capability, automatic seamless power flow switching capability, and flexible connection method of three-phase transformer. It is widely used in the field of power conversion.

[0004] Active thermal management control of the SiC MOSFET switching devices and transformers of the three-phase dual active bridge DC-DC converter helps to improve the operating efficiency and reliability of the system, and has a positive effect on applications in fields and occasions with strict temperature requirements. Summary of the invention

[0005] The present invention provides an active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices through variable frequency control with given temperature constraints and flux saturation constraints. The method can effectively stabilize the temperature of SiC MOSFET and the winding of a three-phase high-frequency transformer at a given temperature as much as possible.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] An active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices comprises the following steps:

[0008] Step 1: Loss analysis of three-phase dual-active DC-DC converter

[0009] Step 1.1. SiC MOSFET loss analysis

[0010] The losses of a SiC MOSFET during a switching cycle are as follows:

[0011] (1) The converter operates in the soft switching range, and the switching loss P sw_MOS≈0;

[0012] (2) Body diode switching loss P sw_bd ≈0;

[0013] (3) The conduction loss of SiC MOSFET in one switching cycle is calculated by the following formula:

[0014]

[0015] Among them, R on is the on-state voltage of SiC MOSFET, D is the duty cycle, T s is the time interval of a switching cycle, t dead is the dead time, I rms is the effective value of the current flowing;

[0016] (4) The conduction loss of the body diode during one switching cycle is calculated by the following formula:

[0017]

[0018] Among them, R gin is the internal gate resistance of SiC MOSFET, R gex is the external gate driver resistance, C gs is the gate-source capacitance of SiC MOSFET, C gd is the gate-drain capacitance of SiC MOSFET, V gsH To drive the SiC MOSFET high, V gsL To drive low level, V th is the SiC MOSFET turn-on threshold voltage, t on_delay Guidance delay time, I cond is the effective value during the conduction time of the body diode;

[0019] Step 1.2: Three-phase high-frequency transformer loss analysis

[0020] Total transformer loss P loss_total By no-load loss P no_load , load loss P load , core loss P Fe Three major components:

[0021] P loss_total =P load +P no_load +P Fe ;

[0022] Step 2: Build a thermal model

[0023] Establish the Foster thermal models of SiC MOSFET and three-phase high-frequency transformer respectively;

[0024] Step 3: Active thermal management of three-phase dual active bridge DC-DC converter

[0025] Step 3.1: The formula for the transmission power of the three-phase dual active bridge DC-DC converter is:

[0026]

[0027] Where V in is the input voltage of the DC-DC converter, ω is the switching angular frequency, and d is the voltage transformation ratio NV of the DC-DC converter out / V in , N is the ratio of the number of turns on the primary side of the transformer to the number of turns on the primary side, V out is the output voltage, L is the transformer leakage inductance, is the phase shift angle;

[0028] Step 3.2: When the output voltage and power are stable, the following formula is derived:

[0029]

[0030] The relationship between angular frequency and phase shift angle is as follows:

[0031]

[0032] Step 3.3: The square of the effective value of the phase current is expressed as follows:

[0033]

[0034] Step 3.4, command:

[0035]

[0036] The range of phase shift angle and voltage conversion ratio is:

[0037] Step 3.5, the equation for the magnetic flux of the three-phase high-frequency transformer is as follows:

[0038]

[0039] Where U p is the input voltage, U s is the output voltage, L p , L' s , L M The primary leakage inductance of the T-type equivalent circuit of the transformer, the equivalent inductance of the secondary leakage inductance converted to the primary side, and the transformer excitation inductance;

[0040] Its modulus length is:

[0041]

[0042] The saturation flux of a three-phase transformer is:

[0043]

[0044] Among them, α safe is the anti-saturation safety factor, B sat is the transformer saturation flux density, A is the transformer effective area;

[0045] Step 3.5, Design thermal management control:

[0046] Step 3.5.1 Active thermal management of SiC MOSFET junction temperature:

[0047] Predicted steady-state junction temperature T of SiC MOSFET j_s As a real-time variable input to the active thermal management control system, it is compared with the set junction temperature upper limit T j_lim If the difference is greater than 0, it means the steady-state junction temperature T j_s Less than the upper limit of junction temperature T j_lim No frequency conversion is required. If it is less than 0, continue to input the desired temperature difference ΔT. j * enter Solved as the square of the expected current effective value The square of the expected effective current Then compare it with the square of the real-time current effective value. Then continue to input; after frequency conversion calculation, calculate the output current effective value of each set switching frequency. Once the square of the output current effective value reaches the square of the expected current effective value Then the desired switching frequency and the corresponding phase shift angle are output;

[0048] Step 3.5.2, Active thermal management of three-phase high-frequency transformer:

[0049] In the frequency conversion calculation step, the output of the expected switching frequency needs to be compared with the expected switching frequency output by the active thermal management of the SiC MOSFET junction temperature. The smaller value is taken as the output, and the expected switching frequency f s * and the corresponding phase shift angle After magnetic link calculation Calculate the output switching frequency f s * Does it cause flux saturation? If it does not cause flux saturation, change the switching frequency to f s * , otherwise no frequency conversion operation is performed.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] Compared with the traditional single physical heat dissipation method, the present invention can further reduce the junction temperature of SiC MOSFET on the basis of physical heat dissipation, so that the overall operating efficiency is effectively improved, the service life of the SiC device of the device can be extended, and the reliability of the system is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a three-phase DAB circuit topology diagram;

[0053] Figure 2 This is the SiC MOSFET bridge arm and related voltage and current waveforms;

[0054] Figure 3 It is the Foster equivalent thermal circuit diagram;

[0055] Figure 4 About 3D graph of

[0056] Figure 5 yes and Relationship diagram;

[0057] Figure 6 It is the T-type equivalent circuit of the transformer;

[0058] Figure 7 is the magnetic chain constraint;

[0059] Figure 8 It is the active thermal management control block diagram;

[0060] Fig. 9 It is the comparison between the predicted temperature and the actual temperature of the thermocouple;

[0061] Fig.10 It is active thermal management control under 700W operation;

[0062] Fig.11 It is active thermal management control under 1200W operation;

[0063] Fig.12 It is the working efficiency of three-phase dual active bridge DC-DC converter. DETAILED DESCRIPTION

[0064] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0065] The power loss of the DC-DC converter is mainly dissipated in the form of heat, and the analysis and calculation of the loss will affect the accuracy of temperature prediction. In the actual operation of the three-phase dual-active DC-DC converter, there are two main sources of loss: (1) MOSFET, (2) three-phase high-frequency transformer. The present invention will analyze the loss model of the third-generation power semiconductor SiC MOSFET and the loss model of the three-phase high-frequency transformer. After establishing the loss model, the Foster thermal network model corresponding to the SiC MOSFET and the three-phase high-frequency transformer is established by the transient thermal impedance method (Thermal Resistance Analysis by Induced Transient, TRAIT) and data fitting. Through the establishment of the above loss model and thermal model, the SiC MOSFET junction temperature and the transformer winding temperature can be predicted in real time. After completing the temperature prediction, the present invention analyzes the relationship between power loss and temperature, and derives a simple calculation formula for the flux size of a three-phase high-frequency transformer. A thermal management control method is proposed to adjust the SiC MOSFET junction temperature and the transformer winding temperature by changing the switching frequency. The junction temperature and the transformer winding temperature can be limited to the set value as much as possible, and the real-time flux size of the transformer is constrained so that it does not exceed the saturation flux, thereby avoiding magnetic saturation of the transformer due to frequency reduction.

[0066] 1. Loss analysis of three-phase dual-active DC-DC converter

[0067] 1. SiC MOSFET loss analysis

[0068] In order to give full play to the advantages of wide-range soft switching of three-phase DAB and reduce the loss of SiC MOSFET switching process, three-phase DAB should work in soft switching conditions as much as possible. When the voltage conversion ratio of three-phase DAB is near 1, the power range covered by its soft switching is the largest. Therefore, when the voltage conversion ratio of the three-phase DAB of the present invention is near 1, SiC MOSFET can realize soft switching, so the loss of SiC MOSFET in one switching cycle under soft switching conditions will be analyzed below.

[0069] Take a bridge arm composed of SiC MOSFET as an example for loss analysis. The directions of various voltages and currents are specified as follows: Figure 2 , the relevant voltage and current waveforms are as follows Figure 2 shown.

[0070] Based on the above waveform, it can be concluded that the loss of a SiC MOSFET in a switching cycle is as follows:

[0071] (1) Switching loss

[0072] Since it works under soft switching conditions, the switching loss can be ignored. sw_MOS ≈0.

[0073] (2) Body diode switching loss

[0074] The body diode switching loss accounts for a small proportion and is very difficult to measure in real time, so it can be ignored. sw_bd ≈0.

[0075] (3) SiC MOSFET conduction loss

[0076] The conduction loss of SiC MOSFET in one switching cycle can be calculated as follows:

[0077]

[0078] Among them, R on is the on-state voltage of SiC MOSFET, D is the duty cycle, T s is the time interval of a switching cycle, t dead is the dead time, I rms is the effective value of the current flowing.

[0079] (4) Body diode conduction loss

[0080] The conduction loss of the body diode during one switching cycle can be calculated as follows:

[0081]

[0082] Among them, R gin is the internal gate resistance of SiC MOSFET, R gex is the external gate driver resistance, C gs is the gate-source capacitance of SiC MOSFET, C gd is the gate-drain capacitance of SiC MOSFET, V gsH To drive the SiC MOSFET high, V gsL To drive low level, V th is the SiC MOSFET turn-on threshold voltage, t on_delay Guidance delay time, I cond It is the effective value during the body diode conduction time. However, actual measurement is very difficult, so the effective value of the current flowing through the SiC MOSFET is used for approximation.

[0083] 2. Loss analysis of three-phase high-frequency transformer

[0084] Total transformer loss P loss_total The no-load loss P no_load , load loss P load , core loss P Fe Three major components:

[0085] Ploss_total =P load +P no_load +P Fe (3)

[0086] (1) No-load loss

[0087] Transformer no-load loss refers to the inherent loss of the transformer when it is no-load. It can be measured through experiments. It accounts for a very low proportion of the total transformer loss and can be ignored in actual engineering design.

[0088] (2) Load loss

[0089] The load loss of the transformer refers to the resistance loss P(I 2 R), eddy current loss P EC-R and stray loss P OSL-R Under the constraints of IEEE / ANSI C57.110 standard, the harmonic loss factor is introduced to respectively 2 R), P EC-R and P OSL-R Calculate and obtain the total harmonic loss of the main transformer winding under harmonic conditions. The calculation formula is:

[0090]

[0091] Where n represents the harmonic order, η max Indicates the maximum calculated harmonic order, I n Refers to the effective value of the nth harmonic current, R dc Indicates the DC resistance of the main transformer, F HL 、F HL-STR They represent the eddy current harmonic loss factor and the stray harmonic loss factor respectively. HL and F HL-STR The definition formula is as follows:

[0092]

[0093]

[0094] In general, only the DC resistance loss in equation (4) is considered, then equation (4) can be rewritten as:

[0095]

[0096] In the formula, K represents the harmonic loss coefficient of the main transformer. Studies have shown that the value of K is about 1.26.

[0097] (3) Iron loss

[0098]

[0099] In the formula, K B is a constant term, whose value is affected by the size and material of the core; f represents the magnetization frequency of the ferromagnetic; B max It represents the magnetic flux density of the main transformer core; η represents the hysteresis coefficient, which ranges from 2.0 to 3.5.

[0100] 2. Establishing Thermal Model

[0101] Foster's equivalent thermal circuit is Figure 3 shown.

[0102] In practical applications, the transient thermal impedance curve obtained by simulation (or measurement) can be fitted with a finite exponential term sequence to obtain an analytical expression for the transient thermal impedance:

[0103]

[0104] Among them, Z th-ref is the equivalent thermal impedance; τ i is the time constant, t is the time, and R i and C i The product of th is the number of fittings, which is related to the order of the established Foster thermal model. The present invention establishes Foster thermal models for SiC MOSFET and three-phase high-frequency transformer respectively. After obtaining the thermal impedance curve according to the steps of TRAIT, the Matlab curve fitting function lsqcurvefit is used to fit formula (9) to obtain the Foster thermal network model parameters.

[0105] 3. Active Thermal Management of Three-Phase Dual Active Bridge DC-DC Converter

[0106] From the Foster thermal model of the above SiC MOSFET and three-phase high-frequency transformer, we know that managing temperature is actually optimizing and managing losses. The main source of heat generation in SiC MOSFET and three-phase high-frequency transformer is the power loss caused by current, so managing the effective value of current becomes the key to active thermal management.

[0107] The formula for the transmission power of the three-phase dual active bridge DC-DC converter is:

[0108]

[0109] Where V in is the input voltage of the DC-DC converter, ω is the switching angular frequency, and d is the voltage transformation ratio NV of the DC-DC converter out / V in , N is the ratio of the number of turns on the primary side of the transformer to the number of turns on the primary side, V outis the output voltage, L is the transformer leakage inductance, is the phase shift angle.

[0110] When the output voltage and power are stable, the following formula can be derived:

[0111]

[0112] Then the relationship between angular frequency and phase shift angle can be deduced as follows:

[0113]

[0114] Formula (11) means that when the corresponding output voltage and output power are constant, the angular frequency and the phase shift angle have the relationship expressed by formula (12). Generally, the phase shift angle is between 0 and π / 3. This means that when the output voltage and output power are constant, a specific switching frequency corresponds to a specific phase shift angle.

[0115] The square of the effective value of the phase current can be expressed as follows:

[0116] (13)

[0118] From the above formula (13), we can see Proportional to a Function of d, let:

[0119]

[0120] In order to give full play to the advantages of wide range soft switching and high efficiency of the three-phase dual active bridge DC-DC converter, the range of phase shift angle and voltage conversion ratio is: d∈[0.8,1.2]. A three-dimensional image can be produced Figure 4 observe 's changing trend.

[0121] Figure 5 Given different power conditions and The curve shows that at the same frequency, the smaller the output power, the smaller the required phase shift angle, and the corresponding I rms Also smaller.

[0122] From the above analysis, it can be concluded that I can be controlled by frequency reduction. rms However, the frequency reduction control needs to be constrained, otherwise it will cause I rms In addition, the magnetic saturation of the three-phase high-frequency transformer needs to be considered. This is because when the frequency is reduced to a certain level, the transformer will experience magnetic saturation, which will have a serious adverse effect on the voltage waveform.

[0123] The T-type equivalent circuit of a three-phase high-frequency transformer is as follows Figure 6 As shown. After research and analysis, the following equation about magnetic flux is obtained:

[0124] Further analysis leads to the calculation formula of steady-state magnetic flux:

[0125]

[0126] Where N is the ratio of the number of turns on the primary side of the transformer to the number of turns on the primary side, Up is the input voltage, Us is the output voltage, Lp, L' s LM is Figure 6 The primary-side leakage inductance and secondary-side leakage inductance of the T-type transformer equivalent circuit shown are converted to the equivalent inductance on the primary side and the transformer excitation inductance.

[0127] Its modulus length is:

[0128]

[0129] The size of the saturation flux of the three-phase transformer of the experimental platform of the present invention is:

[0130]

[0131] Among them, α safe is the anti-saturation safety factor (value is less than or equal to 1), B sat is the transformer saturation flux density, and A is the transformer effective area.

[0132] Figure 7 Given d = 0.8, V in =120V, P out =The steady-state flux change when 1200W. From the figure, we can see that when the frequency is reduced to a certain level, the steady-state flux reaches saturation, which is exactly what we should try our best to avoid in thermal management frequency reduction control.

[0133] Based on the above analysis, the thermal management control is designed as follows:

[0134] Figure 8 The active thermal management control block diagram is shown in Figure 2. The active thermal management of SiC MOSFET junction temperature is used as an example to illustrate its principle. The predicted steady-state junction temperature T of SiC MOSFET j_s As a real-time variable input to the active thermal management control system, it is compared with the set junction temperature upper limit T j_lim If the difference is greater than 0, it means the steady-state junction temperature T j_s Less than the upper limit of junction temperature T j_lim No frequency conversion is required. If it is less than 0, continue to input. Expected temperature difference ΔT j * enter Solved as the square of the expected current effective value The square of the expected effective current Then compare it with the square of the real-time current effective value. Then continue to input. After the frequency conversion calculation, that is, according to the rated output power and the set switching frequency combination (such as f1, f2, f3, f4, f5), the output current effective value of each set switching frequency is calculated by the combined formula (13). Once the square of the output current effective value reaches the square of the expected current effective value The desired switching frequency and the corresponding phase shift angle are then output.

[0135] The thermal management principle of the three-phase high-frequency transformer is similar. In the frequency conversion calculation step, its output expected switching frequency needs to be compared with the active thermal management output expected switching frequency of the SiC MOSFET junction temperature. The smaller value is used as the output expected switching frequency f s * and the corresponding phase shift angle After the magnetic link calculation Calculate the output switching frequency f s * Does it cause flux saturation? If it does not cause flux saturation, change the switching frequency to f s * , otherwise no frequency conversion operation is performed.

[0136] Fig. 9 The changes and errors between the temperature predicted by DSP in real time and the temperature actually sampled by thermocouples are demonstrated. From the experiment, the predicted temperature rise process is consistent with the actual temperature change. The prediction accuracy of the SiC MOSFET related node temperature is relatively high, with a difference of about 2°C. The temperature prediction of the outer surface of the transformer winding is relatively low, which is related to the imprecise thermal model established. However, for the transformer, the prediction error is within an acceptable range.

[0137] Fig.10 The results of the active thermal management control algorithm under 700W are shown. It can be seen that the predicted steady-state temperature is effectively reduced, but the degree of reduction is not large. This is because the 700W output power itself is not large, so the degree of reduction is not obvious. Fig.11 The results of the active thermal management control algorithm in the 1200W case are shown, and it can be seen that the final predicted steady-state temperature is effectively reduced by about 2.3℃.

[0138] Fig.12 The efficiency of the three-phase dual active bridge DC-DC converter designed by the present invention is demonstrated at different output powers and with or without thermal management control. From the experimental results, it can be seen that the three-phase dual active bridge DC-DC converter designed by the present invention has high efficiency, with an average efficiency of more than 95%; under the thermal management control algorithm, the converter efficiency is slightly improved compared to without thermal management control.

Claims

1. An active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices, characterized in that The method comprises the following steps: Step 1: Loss analysis of three-phase dual-active DC-DC converter Step 1.

1. SiC MOSFET loss analysis The losses of a SiC MOSFET during a switching cycle are as follows: (1) The converter operates in the soft switching range, and the switching loss P sw_MOS ≈0; (2) Body diode switching loss P sw_bd ≈0; (3) The conduction loss of SiC MOSFET in one switching cycle is calculated by the following formula: Among them, R on is the on-state voltage of SiC MOSFET, D is the duty cycle, T s is the time interval of a switching cycle, t dead is the dead time, I rms is the effective value of the current flowing; (4) The conduction loss of the body diode during one switching cycle is calculated by the following formula: Among them, R gin is the internal gate resistance of SiC MOSFET, R gex is the external gate driver resistance, C gs is the gate-source capacitance of SiC MOSFET, C gd is the gate-drain capacitance of SiC MOSFET, V gsH To drive the SiC MOSFET high, V gsL To drive low level, V th is the SiC MOSFET turn-on threshold voltage, t on_delay Guidance delay time, I cond is the effective value during the conduction time of the body diode; Step 1.2: Three-phase high-frequency transformer loss analysis Total transformer loss P loss_total By no-load loss P no_load , load loss P load , core loss P Fe Three major components: P loss_total =P load +P no_load +P Fe ; Step 2: Build a thermal model Establish the Foster thermal models of SiC MOSFET and three-phase high-frequency transformer respectively; Step 3: Active thermal management of three-phase dual active bridge DC-DC converter Step 3.1: The formula for the transmission power of the three-phase dual active bridge DC-DC converter is: Where V in is the input voltage of the DC-DC converter, ω is the switching angular frequency, and d is the voltage transformation ratio NV of the DC-DC converter out / V in , N is the ratio of the number of turns on the primary side of the transformer to the number of turns on the primary side, V out is the output voltage, L is the transformer leakage inductance, is the phase shift angle; Step 3.2: When the output voltage and power are stable, the following formula is derived: The relationship between angular frequency and phase shift angle is as follows: Step 3.3: The square of the effective value of the phase current is expressed as follows: Step 3.4, command: The ranges of phase shift angle and voltage conversion ratio are: d∈[0.8,1.2]; Step 3.5, the equation for the magnetic flux of the three-phase high-frequency transformer is as follows: Where U p is the input voltage, U s is the output voltage, L p , L' s , L M The primary leakage inductance of the T-type equivalent circuit of the transformer, the equivalent inductance of the secondary leakage inductance converted to the primary side, and the transformer excitation inductance; Its modulus length is: The saturation flux of a three-phase transformer is: Among them, α safe is the anti-saturation safety factor, B sat is the transformer saturation flux density, A is the transformer effective area; Step 3.5, Design thermal management control: Step 3.5.1 Active thermal management of SiC MOSFET junction temperature: Predicted steady-state junction temperature T of SiC MOSFET j_s As a real-time variable, it is related to the set junction temperature upper limit T j_lim If the difference is greater than 0, it means the steady-state junction temperature T j_s Less than the upper limit of junction temperature T j_lim No frequency conversion is required. If it is less than 0, continue to input the desired temperature difference ΔT. j * enter Solved as the square of the expected current effective value The square of the expected effective current Then compare it with the square of the real-time current effective value. Then continue to input; after frequency conversion calculation, calculate the output current effective value of each set switching frequency. Once the square of the output current effective value reaches the square of the expected current effective value Then the desired switching frequency and the corresponding phase shift angle are output; Step 3.5.2, Active thermal management of three-phase high-frequency transformer: In the frequency conversion calculation step, the output of the expected switching frequency needs to be compared with the expected switching frequency output by the active thermal management of the SiC MOSFET junction temperature. The smaller value is taken as the output, and the expected switching frequency f s * and the corresponding phase shift angle After magnetic link calculation Calculate the output switching frequency f s * Does it cause flux saturation? If it does not cause flux saturation, change the switching frequency to f s * , otherwise no frequency conversion operation is performed.

2. The active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices according to claim 1 is characterized in that In step 1.2, the calculation formula of load loss is: Where n represents the harmonic order, η max Indicates the maximum calculated harmonic order, I n Refers to the effective value of the nth harmonic current, R dc represents the DC resistance of the main transformer, and K represents the harmonic loss coefficient value of the main transformer.

3. The active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices according to claim 1 is characterized in that In step 1.2, the calculation formula of core loss is: In the formula, K B is a constant term, f represents the magnetization frequency of ferromagnetic; B max represents the magnetic flux density of the main transformer core, and η represents the hysteresis coefficient.

4. The active thermal management control method for a three-phase dual active bridge DC-DC converter based on SiC devices according to claim 1 is characterized in that In step 2, after obtaining the thermal impedance curve according to the steps of TRAIT, the following equation is fitted using the Matlab curve fitting function lsqcurvefit to obtain the Foster thermal model parameters: Among them, Z th-ref is the equivalent thermal impedance, τ i is the time constant, t is the time, and R i and C i The product of th is the number of fittings.

Images