Transformer magnetic integration structure integrating double direct-current inductance and leakage inductance and integration method thereof

Abstract

The application discloses a transformer magnetic integration structure integrating double direct-current inductors and leakage inductors and an integration method thereof. In order to overcome the problems of complex magnetic core structure design, large leakage magnetic flux and lack of universality of the integration method in the prior art, the application uses a single standard EE magnetic core to realize integration of double direct-current inductors, leakage inductors and transformers by reasonably designing winding connection mode and air gap parameters for the transformer with three magnetic element structures of direct-current inductor, leakage inductor and transformer. Compared with separate magnetic components, the application can reduce the number of magnetic elements of the transformer, reduce the volume proportion of the magnetic components in the transformer, further reduce the volume of the transformer system, improve the power density, simplify the magnetic core design, reduce the manufacturing complexity of the magnetic integration structure, suppress the unbalanced current of the two side column windings, realize high-efficiency and high-power-density operation of the system, and improve the stability and reliability of the system operation.

Description

Technical Field

[0001] This invention relates to a power electronic magnetic integration technology, and more particularly to a transformer magnetic integration structure and integration method that integrates dual DC inductors and leakage inductors, belonging to the field of high-frequency isolated switching power supplies in the power electronics field. Background Technology

[0002] To achieve high-performance DC-DC conversion over a wide voltage range, including soft switching, low current stress, excellent current control, and simple structure, power electronic converters typically require multiple magnetic components for energy storage and release, and for shaping the current waveform. However, multiple magnetic components result in excessively large component sizes and higher losses, thus affecting the converter's power density and conversion efficiency. This contradicts the current development trend of power electronics towards high frequency, high efficiency, and high power density. Magnetic integration technology, which functionally and structurally winds multiple discrete magnetic components onto a single magnetic core, can effectively reduce the number of magnetic components, shrink the converter size, and lower magnetic component losses, significantly improving power conversion efficiency and power density.

[0003] Currently, researchers both domestically and internationally have proposed some magnetic integration structures and methods, but these have shortcomings in terms of core structure simplification and uniform magnetic flux distribution, and the integration forms are relatively simple, lacking universality. A 2022 paper published in IEEE Transactions on Industrial Electronics, titled "Three Winding Coupled Inductor-Based Dual Active Bridge DC-DC Converter With FullLoad Range ZVS Under Wide Voltage Range," proposes a dual active bridge DC-DC converter based on a three-winding coupled inductor. It integrates two equivalent DC inductors and a high-frequency transformer into a single three-winding coupled inductor. Its advantages include a minimum number of cores and maximized window utilization. However, its disadvantage is that the complexity of integrated structure design and manufacturing increases significantly with the increase in the number of windings. The 2022 paper "An Interleaved Bidirectional Coupled-Inductor Based DC–DC Converter With High Conversion Ratio for Energy Storage System," published in IEEE Transactions on Industrial Electronics, proposed an interleaved bidirectional coupled-inductor dual active bridge DC-DC converter, integrating two DC inductors and a high-frequency transformer by combining two coupled inductors. To further improve power density, the 2023 paper "Dual Coupled Inductors with Controllable Integrated Leakage Inductance and CM Noise Suppression for CF-DAB Converter," published in IEEE Transactions on Power Electronics, integrated leakage inductance into the dual coupled inductors. This simplifies the design of magnetic components by reducing the power capacity of the unit transformers. However, the increased number of cores and the increased leakage flux due to the series connection of windings in each unit transformer are significant drawbacks. It is important to note that a large leakage inductance can negatively impact the converter's power delivery and soft-switching performance. In fact, most current research requires the addition of additional inductors to achieve the necessary leakage inductance for power delivery and soft-switching requirements.

[0004] I. A search revealed Chinese invention patent application number CN202210217679.4, which discloses a cascaded topological magnetic integrated device. This device includes a magnetic core, a transformer, and an inductor assembly. The magnetic core comprises multiple magnetic branches. The transformer windings are wound on the magnetic branches. The inductor assembly windings are also wound on the magnetic branches. When both the inductor assembly and the transformer are energized, the DC magnetic flux of the inductor assembly is superimposed on the AC magnetic flux formed by the transformer windings on the magnetic branches, thereby improving the utilization rate of the magnetic core. This solves the technical problem of large size caused by the large number of magnetic cores in existing power management circuits.

[0005] The technical comparison between this application and the aforementioned prior art documents is as follows:

[0006] 1. The aforementioned prior art provides a cascaded topology magnetic integrated device, which solves the technical problem of excessive size caused by a large number of magnetic cores in the power management circuit in the prior art. It is mainly aimed at a cascaded topology.

[0007] This patent addresses the problems of complex core structure design, large leakage flux, and lack of universality in existing magnetic integration methods. The disclosed transformer magnetic integration structure and integration method integrating dual DC inductors and leakage inductors are mainly aimed at dual active bridge DC-DC converter topologies with dual DC inductors, leakage inductors, and transformers.

[0008] The two are fundamentally different in terms of application scenarios and usage background.

[0009] 2. The cascaded topology magnetic integrated device proposed in the aforementioned prior art includes: a magnetic core, the magnetic core including multiple magnetic branches; a transformer, the winding of the transformer wound on the magnetic branches; an inductor assembly, the winding of the inductor assembly wound on the magnetic branches; when both the inductor assembly and the transformer are energized, the DC magnetic flux of the inductor assembly is superimposed on the AC magnetic flux formed by the winding of the transformer on the magnetic branches, so as to improve the utilization rate of the magnetic core.

[0010] This patent discloses a transformer magnetic integration structure that integrates dual DC inductors and leakage inductance, comprising an EE core, primary windings Np1 and Np2, and secondary windings Ns1 and Ns2. All three posts of the EE core have air gaps. The primary winding Np1 is located on one post of the EE core, forming port 1, and the primary winding Np2 is located on the other post of the EE core, forming port 2. The secondary windings Ns1 and Ns2 are located on the two posts of the EE core respectively and connected in series to form port 3. Through this core structure and winding connection method, the transformer magnetic integration of dual DC inductors and leakage inductance is achieved. Compared with discrete magnetic components, this reduces the number of magnetic elements in the converter, decreases the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, increasing power density, simplifying core design, reducing the complexity of magnetic integration structure fabrication, suppressing unbalanced current in the two post windings, achieving efficient and high power density operation of the system, and improving the stability and reliability of system operation.

[0011] The two differ fundamentally in their technical solutions, implementation paths, physical structures, and beneficial effects.

[0012] II. According to the search, Chinese invention patent application number CN201410332723.1 provides a single-stage boost inverter using a magnetic integrated transformer, including a DC power supply (1), a single-stage boost network (2), and an inverter circuit (3). The DC power supply (1) includes a power source and an inductor L3. The single-stage boost inverter uses an integrated magnetic component (7) as the magnetic integrated transformer. The magnetic integrated component (7) includes opposing magnetic cores, on which primary windings (n1) and secondary windings (n2) are wound respectively. The inverter has a secondary winding (n2) and an inductor L3 winding (n3). The input terminal of the primary winding (n1) is connected to the primary circuit, and the output terminal of the secondary winding (n2) is connected to the secondary circuit. The winding (n3) of the inductor L3 is connected to the positive terminal of the power supply, and the other end is connected to a single-stage boost network (2). The primary winding (n1) and the secondary winding (n2) are composed of coupled inductors or tapped inductors. There is an air gap between the magnetic pillars of the oppositely arranged magnetic core. This inverter can reduce the size of the magnetic components and make leakage inductance easier to control, thereby reducing the copper loss of the winding.

[0013] The technical comparison between this application and the aforementioned prior art documents is as follows:

[0014] 1. The aforementioned prior art proposes a single-stage boost inverter using a magnetic integrated transformer, which includes a DC power supply, a single-stage boost network, and an inverter circuit. It is mainly aimed at a single-stage boost inverter topology.

[0015] This patent addresses the problems of complex core structure design, large leakage flux, and lack of universality in existing magnetic integration methods. The disclosed transformer magnetic integration structure and integration method integrating dual DC inductors and leakage inductors are mainly aimed at dual active bridge DC-DC converter topologies with dual DC inductors, leakage inductors, and transformers.

[0016] The two are fundamentally different in terms of application scenarios and usage background.

[0017] 2. The single-stage boost inverter in the above-mentioned comparative document uses integrated magnetic components as magnetic integrated transformers. The magnetic integrated components include magnetic cores arranged opposite each other. The magnetic cores are wound with a primary winding (n1), a secondary winding (n2), and a winding (n3) of inductor L3. The input terminal of the primary winding (n1) is connected to the primary circuit, and the output terminal of the secondary winding (n2) is connected to the secondary circuit. The winding (n3) of inductor L3 is connected to the positive terminal of the power supply, and the other end is connected to the single-stage boost network (2). The primary winding (n1) and the secondary winding (n2) are composed of coupled inductors or tapped inductors. There is an air gap between the magnetic columns of the oppositely arranged magnetic cores. This inverter can reduce the size of the magnetic components and make leakage inductance easier to control, thereby reducing the copper loss of the windings.

[0018] This patent discloses a transformer magnetic integration structure that integrates dual DC inductors and leakage inductance, comprising an EE core, primary windings Np1 and Np2, and secondary windings Ns1 and Ns2. All three posts of the EE core have air gaps. The primary winding Np1 is located on one post of the EE core, forming port 1, and the primary winding Np2 is located on the other post of the EE core, forming port 2. The secondary windings Ns1 and Ns2 are located on the two posts of the EE core respectively and connected in series to form port 3. Through this core structure and winding connection method, the transformer magnetic integration of dual DC inductors and leakage inductance is achieved. Compared with discrete magnetic components, this reduces the number of magnetic elements in the converter, decreases the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, increasing power density, simplifying core design, reducing the complexity of magnetic integration structure fabrication, suppressing unbalanced current in the two post windings, achieving efficient and high power density operation of the system, and improving the stability and reliability of system operation.

[0019] The two differ fundamentally in their technical solutions, implementation paths, physical structures, and beneficial effects. Summary of the Invention

[0020] This invention proposes a transformer magnetic integration structure and integration method that integrates dual DC inductors and leakage inductance. The technical problem to be solved is: for commonly used converters containing three types of magnetic components—DC inductor, leakage inductance, and transformer—this invention uses a single standard EE magnetic core and, through reasonable design of winding connection methods and air gap parameters, achieves the integration of dual DC inductors, leakage inductance, and transformer. Compared with discrete magnetic components, this invention can reduce the number of magnetic components in the converter, reduce the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, increasing power density, simplifying core design, reducing the complexity of magnetic integration structure fabrication, suppressing unbalanced current in the two-sided column windings, achieving efficient and high-power-density system operation, and improving the stability and reliability of system operation.

[0021] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0022] A transformer magnetic integrated structure integrating dual DC inductors and leakage inductance, characterized in that it includes an EE magnetic core and a primary winding N. p1 and N p2 Secondary winding N s1 and N s2 The EE magnetic core has three magnetic pillars: a first magnetic pillar, a second magnetic pillar, and a third magnetic pillar. The first and third magnetic pillars are located on opposite sides of the second magnetic pillar. The magnetic flux directions of the first and third magnetic pillars are the same but opposite to those of the second magnetic pillar. Air gaps are provided on the first, second, and third magnetic pillars. The primary winding N... p1 The primary winding N is located on the first magnetic post and forms port one thereon. p2 Located on the third magnetic post and forming port two thereon, the secondary winding N s1 and N s2 They are located on the first and third magnetic pillars respectively and form port three after being connected in series.

[0023] As a preferred technical solution of the present invention: the primary winding N p1 and N p2 Reused as dual DC inductor winding N L1 N L1 and transformer primary winding N p The secondary winding N s1 and N s2 For the secondary winding N of the transformer s The primary winding and the secondary winding satisfy formula (1):

[0024] (1).

[0025] As a preferred embodiment of the present invention: the current i flowing through the primary winding is a ib For the dual DC inductor current i L1 i L2 Superimposed transformer primary winding current i p It satisfies formula (2):

[0026] (2).

[0027] As a preferred embodiment of the present invention: the magnetic fluxes of the first magnetic column and the third magnetic column are ϕ1 and ϕ2 respectively, and the magnetic flux of the second magnetic column is ϕ. c The magnetic flux relationship is solved using the magnetic reluctance model of the magnetic integrated transformer, as shown in formula (3):

[0028] (3)

[0029] Where R1 and R2 are the air gap reluctances of the first and third magnetic pillars, respectively, R c The air gap reluctance of the second magnetic column.

[0030] According to Faraday's law of electromagnetic induction and formula (2), the inductance matrix is ​​as shown in formula (4):

[0031] (4)

[0032] Among them, L a and L b These are the primary windings N p1 and N p2 The sense of self, M ab For the primary winding N p1 and N p2 Mutual intuition between them, M ac and M bc These are the primary windings N p1 and secondary winding N s1 +N s2 Intermediate and primary winding N p2 and secondary winding N s1 +N s2 Mutual intuition between them, L c For secondary winding N s1 +N s2 Therefore, the design of a magnetic integrated transformer can be viewed as the design of a multi-winding coupled inductor L, due to its self-inductance.

[0033] The equivalent relationship between the multi-winding coupled inductance L and the transformer parameters required by the converter is shown in Equation (5):

[0034] (5)

[0035] Among them, L m1 and L m2N represents the equivalent magnetizing inductance of the winding, and the equivalent magnetizing inductance is used as a DC inductance. p :N s For the equivalent turns ratio of the transformer, L r_ab This is the equivalent leakage inductance.

[0036] As a preferred embodiment of the present invention, each of the EE magnetic cores is a standard EE magnetic core.

[0037] As a preferred embodiment of the present invention, the air gaps on the first magnetic column, the second magnetic column, and the third magnetic column are located at their respective middle positions.

[0038] As a preferred technical solution of the present invention, it further includes a first horizontal column and a second horizontal column, wherein the two ends of the first magnetic column, the second magnetic column and the third magnetic column are respectively fixed on the first horizontal column and the second horizontal column.

[0039] This application integrates a DC inductor, leakage inductance, and transformer into a single standard EE magnetic core using formula (5). The magnetic integrated structure integrates four magnetic components, including dual DC inductors, leakage inductance, and a transformer. The dual DC inductors are connected in series and then in parallel with the primary winding of the transformer. The secondary winding of the transformer is connected in series with the leakage inductance, realizing a transformer magnetic integrated structure that integrates dual DC inductors and leakage inductance. This transformer magnetic integrated structure can reduce the number of magnetic components in the converter, reduce the volume ratio of magnetic components in the converter, thereby reducing the volume of the converter system, reducing magnetic component losses, and achieving efficient and high power density operation of the system. In addition, the DC inductance, leakage inductance, and transformer turns ratio are only related to the number of winding turns and magnetic reluctance. Therefore, by adjusting the number of winding turns and air gap magnetic reluctance of a single EE magnetic core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying the magnetic core design and reducing the complexity of the magnetic integrated structure manufacturing. Finally, due to the presence of the column air gap in the transformer magnetic integrated structure, the N-axis windings on both sides... p1 and N p2 There is a natural coupling relationship between them, and the column windings on both sides can effectively suppress the unbalanced current between the windings, thereby improving the stability and reliability of the system operation.

[0040] A method for magnetically integrating a transformer with dual DC inductors and leakage inductance, characterized by comprising the following steps:

[0041] S1: Determine the transformer parameters required to achieve the converter's operating performance, including the dual DC inductors L1 and L2, and the leakage inductance L. r Transformer ratio N p :N s The coupling coefficient K of the two column windings;

[0042] S2: Obtain the multi-winding coupled inductance matrix L from the transformer parameters. Calculate the number of winding turns N of a single EE core according to formula (5). p1 N p2N s1 N s2 and air gap magnetoresistance R p R c ;

[0043] S3: Calculate the maximum magnetic flux of the converter. According to formula (3), the magnetic flux waveforms of the three magnetic columns of the magnetic integrated transformer can be obtained, and ϕ2–ϕ1 is the AC magnetic flux without DC bias flowing in the two columns.

[0044] S4: Determine the cross-sectional area of ​​the magnetic core based on the maximum magnetic flux, as shown in formula (6):

[0045] (6)

[0046] Among them, B recommed Select based on the converter's operating frequency.

[0047] S5: Determine the air gap length of the transformer's magnetic integrated structure, as shown in formula (7):

[0048] (7)

[0049] Where μ0 is the vacuum permeability, the design of a magnetically integrated transformer based on a single EE core is thus completed.

[0050] Based on the parameters of the magnetically integrated transformer obtained in steps S1 to S5, the DC inductor, leakage inductance, and transformer are integrated into a single standard EE magnetic core. This magnetically integrated structure integrates four magnetic components, including dual DC inductors, a leakage inductor, and a transformer. This transformer magnetically integrated structure reduces the number of magnetic components in the converter, decreases the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, lowering magnetic component losses, and achieving efficient, high-power-density system operation. Furthermore, the DC inductance, leakage inductance, and transformer turns ratio are only related to the number of winding turns and the magnetic reluctance. Therefore, by adjusting the number of winding turns and the air gap magnetic reluctance of a single EE magnetic core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying core design and reducing the complexity of manufacturing the magnetically integrated structure. Finally, due to the presence of the column air gap in the transformer magnetically integrated structure, the N-axis windings on both sides... p1 and N p2 There is a natural coupling relationship between them, and the column windings on both sides can effectively suppress the unbalanced current between the windings, thereby improving the stability and reliability of the system operation.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] 1. The transformer magnetic integration structure and integration method disclosed in this invention integrates dual DC inductors and leakage inductors. For commonly used converters containing three types of magnetic components—DC inductors, leakage inductors, and transformers—this invention uses a single standard EE magnetic core and achieves the integration of dual DC inductors, leakage inductors, and transformers through reasonable design of winding connection methods and air gap parameters. This reduces the number of magnetic components in the converter, decreases the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, reducing magnetic component losses, and helping to improve system efficiency and power density.

[0053] 2. The integrated transformer magnetic structure and its integration method that integrates dual DC inductors and leakage inductance disclosed in this invention can achieve flexible control of inductance parameters and transformer turns ratio by adjusting the number of winding turns and air gap magnetic resistance of a single EE magnetic core, simplifying magnetic core design and reducing the complexity of manufacturing the magnetic integrated structure.

[0054] 3. The transformer magnetic integration structure and integration method disclosed in this invention, which integrates dual DC inductors and leakage inductance, has N-type column windings on both sides due to the presence of column air gaps in the transformer magnetic integration structure. p1 and N p2 There is a natural coupling relationship between them, and the column windings on both sides can effectively suppress the unbalanced current between the windings, thereby improving the stability and reliability of the system operation. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the EE magnetic core structure and winding connections;

[0056] Figure 2 This is a circuit diagram of the EE magnetic core structure;

[0057] Figure 3 This is a diagram of the magnetoresistive model in this application;

[0058] Figure 4 This is a three-dimensional structural diagram of the present invention;

[0059] Figure 5 This is a schematic diagram of the current-source dual active bridge converter in this embodiment;

[0060] Figure 6 A flowchart illustrating a transformer magnetic integration method that integrates dual DC inductors and leakage inductance. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0062] like Figure 1-4 As shown, this invention proposes a transformer magnetic integrated structure that integrates dual DC inductors and leakage inductance, including an EE magnetic core and a primary winding N. p1 and N p2 Secondary winding Ns1 and N s2 The EE magnetic core has three magnetic pillars: a first magnetic pillar, a second magnetic pillar, and a third magnetic pillar. The first and third magnetic pillars are located on opposite sides of the second magnetic pillar. The magnetic flux directions of the first and third magnetic pillars are the same but opposite to those of the second magnetic pillar. Air gaps are provided on the first, second, and third magnetic pillars. The primary winding N... p1 The primary winding N is located on the first magnetic post and forms port one thereon. p2 Located on the third magnetic post and forming port two thereon, the secondary winding N s1 and N s2 They are located on the first and third magnetic pillars respectively and form port three after being connected in series.

[0063] The primary winding N p1 and N p2 Reused as dual DC inductor winding N L1 N L1 and transformer primary winding N p The secondary winding N s1 and N s2 For the secondary winding N of the transformer s The primary winding and the secondary winding satisfy formula (1):

[0064] (1).

[0065] The current i flowing through the primary winding a i b For the dual DC inductor current i L1 i L2 Superimposed transformer primary winding current i p It satisfies formula (2):

[0066] (2).

[0067] The magnetic fluxes of the first and third magnetic pillars are ϕ1 and ϕ2, respectively, and the magnetic flux of the second magnetic pillar is ϕ. c The magnetic flux relationship is solved using the magnetic reluctance model of the magnetic integrated transformer, as shown in formula (3):

[0068] (3)

[0069] Where R1 and R2 are the air gap reluctances of the first and third magnetic pillars, respectively, R cR1 represents the air gap reluctance of the second magnetic column. Since the permeability of the EE core is much greater than that of air, the core reluctance can be ignored. R1 and R2 are the air gap reluctances of the two side columns of the EE core, respectively. For design simplification, the air gap reluctances of the two side columns are usually equal, i.e., R1 = R2 = R p

[0070] According to Faraday's law of electromagnetic induction and formula (2), the inductance matrix is ​​as shown in formula (4):

[0071] (4)

[0072] Among them, L a and L b These are the primary windings N p1 and N p2 The sense of self, M ab For the primary winding N p1 and N p2 Mutual intuition between them, M ac and M bc These are the primary windings N p1 and secondary winding N s1 +N s2 Intermediate and primary winding N p2 and secondary winding N s1 +N s2 Mutual intuition between them, L c For secondary winding N s1 +N s2 Therefore, the design of a magnetic integrated transformer can be viewed as the design of a multi-winding coupled inductor L, due to its self-inductance.

[0073] The equivalent relationship between the multi-winding coupled inductance L and the transformer parameters required by the converter is shown in Equation (5):

[0074] (5)

[0075] Among them, L m1 and L m2 N represents the equivalent magnetizing inductance of the winding, and the equivalent magnetizing inductance is used as a DC inductance. p :N s For the equivalent turns ratio of the transformer, L r_ab This is the equivalent leakage inductance.

[0076] Each EE magnetic core is a standard EE magnetic core. The air gaps on the first, second, and third magnetic pillars are located at their respective center positions. The system also includes a first and second transverse pillar, with the ends of the first, second, and third magnetic pillars respectively fixed to the first and second transverse pillars.

[0077] Example: Taking a commonly used type of current source dual active bridge DC-DC converter as an example, this paper illustrates the effectiveness and feasibility of the integrated transformer magnetic structure and its design method that integrates dual DC inductors and leakage inductors disclosed in this invention.

[0078] Figure 5 This is a schematic diagram of a magnetically integrated dual active bridge converter provided in this embodiment. The magnetically integrated dual active bridge converter provided in this embodiment includes a primary-side full bridge, a secondary-side full bridge, a magnetically integrated section, a primary-side DC power supply, a secondary-side DC power supply, an intermediate stage clamping capacitor, and an output filter capacitor. The primary-side full bridge includes a switching device Q. 1a Q 2a Q1, Q2, points a and b are the midpoints of the two arms of the primary active bridge, respectively. ab The potential difference between points a and b; the secondary-side full bridge includes switching devices S1, S2, S3, and S4; points c and d are the midpoints of the two arms of the primary-side active bridge, respectively; v cd i represents the potential difference between points c and d; p and i s This refers to the current on the primary and secondary sides of the transformer in the converter; the magnetic integrated section includes DC inductors L1 and L2, and leakage inductance L... r High-frequency transformer T r .

[0079] The positive terminal of the primary-side DC power supply is connected to both DC inductors at point e, and the negative terminal of the primary-side DC power supply is connected to both the source of the switching device Q2 and the clamping capacitor C. c One end is connected. The drain of switching transistor Q1 is connected to the other end of switching transistor Q. 1a The source of transistor Q1 is connected to the source of transistor Q2, and the source of transistor Q2 is connected to the source of transistor Q3. The drain of transistor Q2 is connected to the source of transistor Q4. 2a The source of the transistor is connected to the source of the transistor, and it is connected to the DC inductor L2 at point b. The switching transistor Q... 1a Drain and clamping capacitor C c The other end and Q 2a The drain of the circuit is connected to the circuit and connected to DC inductor L1 at point a. DC inductor L1 is connected in series with DC inductor L2, and then connected to the high-frequency transformer T. r The primary winding of the high-frequency transformer T is connected in parallel at points a and b. r The secondary winding is connected to the leakage inductance L r Leakage inductance L r Simultaneously connecting the source of switch S1 and the drain of switch S3 at point c, the high-frequency transformer T... rThe secondary winding of the transistor is connected to the source of switching transistor S2 and the drain of switching transistor S4 at point d. The drain of switching transistor S1 is connected to the drain of switching transistor S2 and the positive terminal of output capacitor C, and is also connected to the positive terminal of the output voltage. The source of switching transistor S3 is connected to the source of switching transistor S4 and the negative terminal of output capacitor C, and is also connected to the negative terminal of the output voltage.

[0080] like Figure 6 As shown, the transformer magnetic integration method for integrating dual DC inductors and leakage inductance disclosed in this invention includes the following steps:

[0081] S1: Under the premise of achieving soft switching of all switching transistors and the current-source dual active bridge DC-DC converter operating at a relatively small effective current value, determine the required transformer parameters, including the dual DC inductors L1 and L2, and the leakage inductance L... r Transformer ratio N p :N s The coupling coefficient K of the two column windings;

[0082] S2: Obtain the multi-winding coupled inductance matrix L from the transformer parameters. Calculate the number of winding turns N of a single EE core according to formula (5). p1 N p2 N s1 N s2 and air gap magnetoresistance R p R c .

[0083] S3: Calculate the maximum magnetic flux of the converter. According to formula (3), the magnetic flux waveforms of the three magnetic columns of the magnetic integrated transformer can be obtained, and ϕ2–ϕ1 is the AC magnetic flux without DC bias flowing in the two columns.

[0084] S4: To prevent core saturation, determine the appropriate core cross-sectional area based on the maximum magnetic flux, as shown in formula (6):

[0085] (6)

[0086] Among them, B recommed Select based on the converter's operating frequency.

[0087] S5: Determine the air gap length of the transformer's magnetic integrated structure, as shown in formula (7):

[0088] (7)

[0089] Where μ0 is the permeability of free space. Thus, the design of a magnetically integrated transformer based on a single EE core is completed.

[0090] Based on the parameters of the magnetically integrated transformer obtained in steps S1 to S5, the DC inductor, leakage inductance, and transformer are integrated into a single standard EE magnetic core. This magnetically integrated structure integrates four magnetic components, including dual DC inductors, a leakage inductor, and a transformer. This transformer magnetically integrated structure reduces the number of magnetic components in the converter, decreases the volume ratio of magnetic components in the converter, thereby reducing the size of the converter system, lowering magnetic component losses, and achieving efficient, high-power-density system operation. Furthermore, the DC inductance, leakage inductance, and transformer turns ratio are only related to the number of winding turns and the magnetic reluctance. Therefore, by adjusting the number of winding turns and the air gap magnetic reluctance of a single EE magnetic core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying core design and reducing the complexity of manufacturing the magnetically integrated structure. Finally, due to the presence of the column air gap in the transformer magnetically integrated structure, the N-axis windings on both sides... p1 and N p2 There is a natural coupling relationship between them, and the column windings on both sides can effectively suppress the unbalanced current between the windings, thereby improving the stability and reliability of the system operation.

[0091] In the embodiments described, the primary and secondary full-bridge circuits of the current-source dual active bridge DC-DC converter can employ single-phase-shift control, extended phase-shift control, etc. When energy is transferred in the forward direction, the primary full-bridge operates in the inverter state, and the secondary full-bridge operates in the rectification state. When energy is transferred in the reverse direction, the secondary full-bridge operates in the inverter state, and the primary full-bridge operates in the rectification state.

[0092] Primary winding N p1 and N p2 Port 1 and Port 2, formed respectively, connect point e to points a and b, the midpoints of the bridge arms of the primary side of the full bridge. The secondary winding N... s1 and N s2 Port 3, formed by series connection, is connected to the midpoints c and d of the secondary full-bridge arm respectively. Under the magnetic integrated structure, through the access of the primary and secondary DC power supplies and the drive of the switching transistors, the magnetic integrated transformer assists the converter in realizing the power transmission of the dual active bridge DC-DC converter.

[0093] As can be seen from the above analysis, the present invention can optimize the transformer for electrical isolation of the converter, increase the degree of control freedom, and more flexibly assist the converter in bidirectional power transmission under soft switching in the full load range. It can also reduce the volume ratio and losses of the converter's magnetic components, improve the converter's power density and operating efficiency, and naturally achieve the suppression effect of unbalanced current on the two column windings, thereby improving the stability and reliability of the converter operation.

[0094] It should be noted that the above detailed description further elaborates on the purpose, technical solution, and beneficial effects of the invention. The magnetic integrated structure is applied to a current-source dual active bridge converter and is not intended to limit the scope of protection of this invention to this topology. Any modifications, equivalent substitutions, or improvements made based on this invention should be included within the scope of protection of this invention. The magnetic integrated structure and magnetic integrated transformer design method proposed in this invention can be applied to converters containing DC inductors, leakage inductors, and transformers, and can also be applied to the integration between coupled inductors and inductors, significantly improving the power density of the converter and achieving high-performance operation.

Claims

1. A transformer magnetic integrated structure integrating dual DC inductors and leakage inductance, characterized in that: Including EE magnetic core, primary winding N p1 and N p2 Secondary winding N s1 and N s2 The EE magnetic core has three magnetic pillars: a first magnetic pillar, a second magnetic pillar, and a third magnetic pillar. The first and third magnetic pillars are located on opposite sides of the second magnetic pillar. The magnetic flux directions of the first and third magnetic pillars are the same but opposite to those of the second magnetic pillar. Air gaps are provided on the first, second, and third magnetic pillars. The primary winding N... p1 The primary winding N is located on the first magnetic post and forms port one thereon. p2 The secondary winding N is located on the third magnetic post and forms port two thereon. s1 and N s2 They are located on the first and third magnetic pillars respectively and form port three after being connected in series; The primary winding N p1 and N p2 Reused as dual DC inductor winding N L1 N L1 and transformer primary winding N p The secondary winding N s1 and N s2 For the secondary winding N of the transformer s The primary winding and the secondary winding satisfy formula (1): (1)； The current i flowing through the primary winding a i b For the dual DC inductor current i L1 i L2 Superimposed transformer primary winding current i p It satisfies formula (2): (2)； The magnetic fluxes of the first and third magnetic pillars are ϕ1 and ϕ2, respectively, and the magnetic flux of the second magnetic pillar is ϕ. c The magnetic flux relationship is solved using the magnetic reluctance model of the magnetic integrated transformer, as shown in formula (3): (3) Where R1 and R2 are the air gap reluctances of the first and third magnetic pillars, respectively, R c The air gap reluctance of the second magnetic column. According to Faraday's law of electromagnetic induction and formula (2), the inductance matrix is ​​as shown in formula (4): (4) Among them, L a and L b These are the primary windings N p1 and N p2 The sense of self, M ab For the primary winding N p1 and N p2 Mutual intuition between them, M ac and M bc These are the primary windings N p1 and secondary winding N s1 +N s2 Intermediate and primary winding N p2 and secondary winding N s1 +N s2 Mutual intuition between them, L c For secondary winding N s1 +N s2 Therefore, the design of a magnetic integrated transformer can be viewed as the design of a multi-winding coupled inductor L, due to its self-inductance. The equivalent relationship between the multi-winding coupled inductance L and the transformer parameters required by the converter is shown in Equation (5): (5) Among them, L m1 and L m2 N represents the equivalent magnetizing inductance of the winding, and the equivalent magnetizing inductance is used as a DC inductance. p :N s For the equivalent turns ratio of the transformer, L r_ab This is the equivalent leakage inductance.

2. The transformer magnetic integration structure integrating dual DC inductors and leakage inductance according to claim 1, characterized in that: Each of the EE cores is a standard EE core.

3. The transformer magnetic integration structure integrating dual DC inductors and leakage inductance according to claim 1, characterized in that: The air gaps on the first, second, and third magnetic pillars are located at their respective center positions.

4. The transformer magnetic integration structure integrating dual DC inductors and leakage inductance according to claim 1, characterized in that: It also includes a first horizontal post and a second horizontal post, with the ends of the first magnetic post, the second magnetic post, and the third magnetic post respectively fixed to the first horizontal post and the second horizontal post.

5. The transformer magnetic integration method for integrating dual DC inductors and leakage inductance according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Determine the transformer parameters required to achieve the converter's operating performance, including the dual DC inductors L1 and L2, and the leakage inductance L. r Transformer ratio N p :N s The coupling coefficient K of the two column windings; S2: Obtain the multi-winding coupled inductance matrix L from the transformer parameters. Calculate the number of winding turns N of a single EE core according to formula (5). p1 N p2 N s1 N s2 and air gap magnetoresistance R p R c ; S3: Calculate the maximum magnetic flux of the converter. According to formula (3), the magnetic flux waveforms of the three magnetic columns of the magnetic integrated transformer can be obtained, and ϕ2–ϕ1 is the AC magnetic flux without DC bias flowing in the two columns. S4: Determine the cross-sectional area of ​​the magnetic core based on the maximum magnetic flux, as shown in formula (6): (6) Among them, B recommed Select based on the converter's operating frequency. S5: Determine the air gap length of the transformer's magnetic integrated structure, as shown in formula (7): (7) Where μ0 is the vacuum permeability, the design of a magnetically integrated transformer based on a single EE core is thus completed.

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