Transformer magnetic integration structure integrating double direct-current inductors and leakage inductors and integration method of transformer magnetic integration structure

Abstract

The invention discloses a transformer magnetic integration structure integrating double direct current inductors and leakage inductors and an integration method of the transformer magnetic integration structure. In order to solve the related problems that in an existing magnetic integration method, a magnetic core structure is complex in design and large in leakage magnetic flux, and an integration method lacks universality and the like, a single standard EE magnetic core is used for a common type converter with three magnetic element structures including a direct-current inductor, a leakage inductor and a transformer, the winding connection mode and the air gap parameters are reasonably designed, and the magnetic core structure is optimized. Compared with a discrete magnetic part, the number of magnetic elements of the converter can be reduced, the volume proportion of the magnetic part in the converter can be reduced, the volume of a converter system is further reduced, the power density is improved, the magnetic core design is simplified, and the manufacturing complexity of a magnetic integrated structure is reduced; unbalanced current of column windings on the two sides is suppressed, efficient and high-power-density operation of the system is achieved, and stability and reliability of operation of the system are improved.

Description

Technical Field

[0001] The present invention relates to a power electronics magnetic integration technology, in particular to a transformer magnetic integration structure integrating dual DC inductors and leakage inductors and an integration method thereof, and belongs to the field of high-frequency isolation switch power supply in the power electronics field. Background Art

[0002] To achieve high-performance DC conversion over a wide voltage range, including soft switching, low current stress, current control performance, and a simple structure, power electronic converters typically require multiple magnetic elements to store and release energy and shape the current waveform. However, multiple magnetic elements lead to excessively large magnetic components and high magnetic losses, which in turn affect the converter's power density and conversion efficiency. This contradicts the current development trend of power electronics, which is towards high frequency, high efficiency, and high power density. Magnetic integration technology, functionally and structurally winding multiple discrete magnetic components onto a single core, can effectively reduce the number of magnetic components, shrink the converter's size, and lower magnetic component losses, which is of great significance for improving power conversion efficiency and power density.

[0003] At present, researchers at home and abroad have proposed a number of magnetic integration structures and integration methods, but they have shortcomings in terms of simplified core structure and uniform magnetic flux distribution. In addition, the integration form is relatively simple, and the integration method lacks universal applicability. "ThreeWinding Coupled Inductor-Based Dual Active Bridge DC-DC Converter With FullLoad Range ZVS Under Wide Voltage Range," published in IEEE Transaction on Industrial Electronics in 2022, proposed a dual active bridge DC-DC converter based on three-winding coupled inductors. This integrates two equivalent DC inductors and a high-frequency transformer into a three-winding coupled inductor. Its advantages are the minimum number of magnetic cores and the maximum window utilization. The disadvantage is that as the number of windings increases, the complexity of the integrated structure design and production increases significantly. "An Interleaved Bidirectional Coupled-Inductor Based DC–DC Converter With High Conversion Ratio for Energy Storage System," published in IEEE Transaction on Industrial Electronics in 2022, proposed an interleaved, coupled-inductor, dual-active-bridge DC–DC converter. This design integrates two DC inductors and a high-frequency transformer by combining two coupled inductors. To further improve power density, the dual coupled inductors in "Dual Coupled Inductors with Controllable Integrated Leakage Inductance and CM Noise Suppression for CF-DAB Converter," published in IEEE Transaction on Power Electronics in 2023, integrate leakage inductance. This reduces the power capacity of the unit transformers and simplifies the design of the magnetic components. However, the increased number of magnetic cores and the series connection of the windings in each unit transformer increase leakage flux. It's important to note that large leakage inductance can compromise the converter's power transfer and soft-switching performance. In fact, most current literature requires the addition of additional inductors to achieve the required leakage inductance to achieve the power transfer and soft-switching requirements.

[0004] 1. After searching, the Chinese invention patent with application number CN202210217679.4 discloses a cascade topology magnetic integration device, which includes a magnetic core, a transformer and an inductor component. The magnetic core includes multiple magnetic branches. The winding of the transformer is wound on the magnetic branch. The winding of the inductor component is wound on the magnetic branch. When the inductor component and the transformer are both energized, the DC magnetic flux of the inductor component is superimposed on the AC magnetic flux formed by the winding of the transformer in the magnetic branch to improve the utilization rate of the magnetic core. This solves the technical problem of large size caused by the large number of magnetic cores in the power management circuit in the prior art.

[0005] The technical comparison between this application and the above-mentioned reference documents is as follows:

[0006] 1. The above-mentioned comparative document provides a cascade topology magnetic integrated device to solve the technical problem of excessive size caused by the large number of magnetic cores in the power management circuit in the prior art, and is mainly aimed at a cascade topology.

[0007] In order to overcome the problems of complex core structure design, large leakage flux, and lack of universality in existing magnetic integration methods, this patent discloses a transformer magnetic integration structure integrating dual DC inductors and leakage inductors and its integration method, which are mainly aimed at dual active bridge DC-DC converter topologies with dual DC inductors, leakage inductors and transformers.

[0008] There are essential differences between the two in application scenarios and usage backgrounds.

[0009] 2. The above-mentioned comparative document proposes a cascade topology magnetic integration device, which includes: a magnetic core, which includes multiple magnetic branches; a transformer, whose windings are wound on the magnetic branches; an inductor component, whose windings are wound on the magnetic branches; when the inductor component and the transformer are both energized, the DC magnetic flux of the inductor component is superimposed on the AC magnetic flux formed by the windings of the transformer in the magnetic branches, so as to improve the utilization rate of the magnetic core.

[0010] The patent discloses a transformer magnetic integration structure integrating dual DC inductors and leakage inductors, comprising an EE core, primary windings Np1 and Np2, and secondary windings Ns1 and Ns2. The three magnetic columns of the EE core all have air gaps. The primary winding Np1 is located on one side column of the EE core and forms port 1. The primary winding Np2 is located on the other side column of the EE core and forms port 2. The secondary windings Ns1 and Ns2 are located on the two side columns of the EE core and are connected in series to form port 3. The magnetic integration of the transformer with dual DC inductors and leakage inductors is achieved through the core structure and winding connection method. Compared with discrete magnetic parts, it can reduce the number of magnetic components of the converter, reduce the volume ratio of the magnetic parts in the converter, and thus reduce the volume of the converter system, improve the power density, simplify the core design, reduce the complexity of the magnetic integration structure, suppress the unbalanced current of the windings on both sides, achieve high efficiency and high power density operation of the system, and improve the stability and reliability of the system operation.

[0011] There are essential differences between the two in terms of technical solutions, implementation paths, physical structures and beneficial effects.

[0012] 2. After searching, the 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), characterized in that: the DC power supply (1) includes a power supply and an inductor L3, the single-stage boost inverter uses an integrated magnetic component (7) as a magnetic integrated transformer, and the magnetic integrated magnetic component (7) includes relatively arranged magnetic cores, and the relatively arranged magnetic cores are respectively wound with a primary winding (n1) and a secondary winding (n2). A secondary winding (n2) and a winding (n3) of an inductor L3, wherein the input end of the primary winding (n1) is connected to the primary circuit, and the output end of the secondary winding (n2) is connected to the secondary circuit; the winding (n3) of the inductor L3 is connected to the positive pole 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; an air gap is provided between the magnetic columns of the relatively arranged magnetic cores; the inverter can reduce the volume of the magnetic components, and can also make the leakage inductance easy to control, thereby reducing the copper loss of the winding.

[0013] The technical comparison between this application and the above-mentioned reference documents is as follows:

[0014] 1. The above-mentioned comparative document 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, and is mainly aimed at a single-stage boost inverter topology.

[0015] In order to overcome the problems of complex core structure design, large leakage flux, and lack of universality in existing magnetic integration methods, this patent discloses a transformer magnetic integration structure integrating dual DC inductors and leakage inductors and its integration method, which are mainly aimed at dual active bridge DC-DC converter topologies with dual DC inductors, leakage inductors and transformers.

[0016] There are essential differences between the two in application scenarios and usage backgrounds.

[0017] 2. The single-stage boost inverter in the above-mentioned comparative document adopts an integrated magnetic component as a magnetic integrated transformer, wherein the magnetic integrated magnetic component comprises relatively arranged magnetic cores, on which a primary winding (n1), a secondary winding (n2) and a winding (n3) of an inductor L3 are respectively wound, the input end of the primary winding (n1) is connected to the primary circuit, and the output end of the secondary winding (n2) is connected to the secondary circuit; the winding (n3) of the inductor L3 is connected to the positive pole 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 relatively arranged magnetic cores; the inverter can not only reduce the volume of the magnetic component, but also make the leakage inductance easy to control and reduce the copper loss of the winding.

[0018] The patent discloses a transformer magnetic integration structure integrating dual DC inductors and leakage inductors, comprising an EE core, primary windings Np1 and Np2, and secondary windings Ns1 and Ns2. The three magnetic columns of the EE core all have air gaps. The primary winding Np1 is located on one side column of the EE core and forms port 1. The primary winding Np2 is located on the other side column of the EE core and forms port 2. The secondary windings Ns1 and Ns2 are located on the two side columns of the EE core and are connected in series to form port 3. The magnetic integration of the transformer with dual DC inductors and leakage inductors is achieved through the core structure and winding connection method. Compared with discrete magnetic parts, it can reduce the number of magnetic components of the converter, reduce the volume ratio of the magnetic parts in the converter, and thus reduce the volume of the converter system, improve the power density, simplify the core design, reduce the complexity of the magnetic integration structure, suppress the unbalanced current of the windings on both sides, achieve high efficiency and high power density operation of the system, and improve the stability and reliability of the system operation.

[0019] There are essential differences between the two in terms of technical solutions, implementation paths, physical structures and beneficial effects. Summary of the Invention

[0020] The present invention proposes a transformer magnetic integrated structure integrating dual DC inductors and leakage inductors and an integration method thereof. The technical problem to be solved is: for a commonly used type of converter containing three magnetic component structures of DC inductor, leakage inductor and transformer, a single standard EE magnetic core is used to realize the integration of dual DC inductor, leakage inductor and transformer by reasonably designing the winding connection method and air gap parameters. Compared with discrete magnetic parts, the number of magnetic components of the converter can be reduced, the volume proportion of the magnetic parts in the converter can be reduced, and the volume of the converter system can be reduced, the power density can be improved, the magnetic core design can be simplified, the complexity of the magnetic integrated structure can be reduced, the unbalanced current of the column windings on both sides can be suppressed, the system can be operated with high efficiency and high power density, and the stability and reliability of the system operation can be improved.

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

[0022] The transformer magnetic integrated structure with integrated dual DC inductors and leakage inductors is characterized by comprising an EE magnetic core, a primary winding N p1 and N p2 , secondary winding N s1 and N s2 The EE core has three magnetic columns, namely the first magnetic column, the second magnetic column and the third magnetic column. The first magnetic column and the third magnetic column are respectively located on both sides of the second magnetic column. The magnetic flux directions of the first magnetic column and the third magnetic column are the same and opposite to the magnetic flux direction of the second magnetic column. The first magnetic column, the second magnetic column and the third magnetic column are respectively provided with air gaps. The primary winding N p1 Located on the first magnetic column and forming a port 1 thereon, the primary winding N p2 Located on the third magnetic column and forming port 2 thereon, the secondary winding N s1 and N s2 They are respectively located on the first magnetic column and the third magnetic column 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 Multiplexed into dual DC inductor winding N L1 、N L1 and transformer primary winding N p , the secondary winding N s1 and N s2 is the secondary winding N of the transformer s , the primary winding and the secondary winding satisfy formula (1):

[0024] (1).

[0025] As a preferred technical solution of the present invention: the current i flowing through the primary winding a 、ib is the dual DC inductor current i L1 、i L2 Superimposed transformer primary winding current i p , satisfying formula (2):

[0026] (2).

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

[0028] (3)

[0029] Among them, R1 and R2 are the air gap magnetic resistance of the first and third magnetic columns respectively, R c is 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 shown in formula (4):

[0031] (4)

[0032] Among them, L a and L b They are respectively the primary winding N p1 and N p2 Self-perception, M ab is the primary winding N p1 and N p2 Mutual inductance, M ac and M bc They are respectively the primary winding N p1 and the secondary winding N s1 +N s2 Intermediate and primary winding N p2 and the secondary winding N s1 +N s2 Mutual inductance, L c is the secondary winding N s1 +N s2 Therefore, the design of the magnetic integrated transformer can be regarded as the design of the multi-winding coupled inductor L.

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

[0034] (5)

[0035] Among them, L m1 and L m2are the equivalent magnetizing inductance of the winding, and the equivalent magnetizing inductance is used as the DC inductance, N p :N s is the transformer equivalent ratio, L r_ab is the equivalent leakage inductance.

[0036] As a preferred technical solution of the present invention: the single EE magnetic core is a standard EE magnetic core.

[0037] As a preferred technical solution of the present invention: the air gaps on the first magnetic column, the second magnetic column and the third magnetic column are respectively located in the middle of each.

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

[0039] This application integrates the DC inductor, leakage inductor and transformer into a single standard EE core through formula (5). The magnetic integration structure integrates four magnetic components, including dual DC inductors, leakage inductors and transformers. 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 and the leakage inductor are connected in series to realize the transformer magnetic integration structure integrating dual DC inductors and leakage inductors. The transformer magnetic integration structure can reduce the number of magnetic components of the converter, reduce the volume ratio of the magnetic components in the converter, and thus reduce the volume of the converter system, reduce the loss of magnetic components, and realize high efficiency and high power density operation of the system. In addition, the DC inductor, leakage inductor and transformer turns ratio are only related to the number of winding turns and magnetic resistance. Therefore, by adjusting the number of winding turns and air gap magnetic resistance of the single EE core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying the core design and reducing the complexity of the magnetic integration structure. Finally, due to the presence of the column air gap in the transformer magnetic integration structure, the column windings N on both sides are p1 and N p2 There is a natural coupling relationship between the two sides of the column winding, which can effectively suppress the unbalanced current between the windings and improve the stability and reliability of the system operation.

[0040] A transformer magnetic integration method integrating dual DC inductors and leakage inductors is 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, the leakage inductance L r , transformation ratio N p :N s , the coupling coefficient K of the column windings on both sides;

[0042] S2: The multi-winding coupled inductance matrix L is equivalent to the transformer parameters. According to formula (5), the number of winding turns N of the single EE core is calculated. p1 、N p2、N s1 、N s2 and air gap reluctance 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 columns on both sides;

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

[0045] (6)

[0046] Among them, B recommed According to the converter operating frequency selection,

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

[0048] (7)

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

[0050] According to the magnetic integrated transformer parameters of steps S1 to S5, the DC inductor, leakage inductor and transformer are integrated into a single standard EE core. The magnetic integrated structure integrates four magnetic components, including dual DC inductors, leakage inductors and transformers. The transformer magnetic integrated structure can reduce the number of magnetic components of the converter, reduce the volume ratio of magnetic components in the converter, and thus reduce the volume of the converter system, reduce the loss of magnetic components, and achieve high efficiency and high power density operation of the system. In addition, the DC inductor, leakage inductor and transformer turns ratio are only related to the number of winding turns and magnetic resistance. Therefore, by adjusting the number of winding turns and air gap magnetic resistance of a single EE core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying the core design and reducing the complexity of the magnetic integrated structure. Finally, due to the presence of the column air gap in the transformer magnetic integrated structure, the column windings N on both sides are p1 and N p2 There is a natural coupling relationship between the two sides of the column winding, which can effectively suppress the unbalanced current between the windings and improve the stability and reliability of the system operation.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. The transformer magnetic integration structure and integration method of the integrated dual DC inductor and leakage inductor disclosed in the present invention are targeted at commonly used converters containing three magnetic components: a DC inductor, a leakage inductor, and a transformer. By using a single standard EE magnetic core and rationally designing the winding connection method and air gap parameters, the dual DC inductor, leakage inductor, and transformer can be integrated. This can reduce the number of magnetic components in the converter and the volume ratio of the magnetic components in the converter, thereby reducing the volume of the converter system and reducing the loss of the magnetic components, which helps to improve the system efficiency and power density indicators.

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

[0054] 3. The transformer magnetic integrated structure and integration method of the integrated dual DC inductor and leakage inductor disclosed in the present invention, due to the presence of column air gap in the transformer magnetic integrated structure, the column windings N on both sides p1 and N p2 There is a natural coupling relationship between the two sides of the column winding, which can effectively suppress the unbalanced current between the windings and improve the stability and reliability of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of EE core structure and winding connection;

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

[0057] Figure 3 This is the magnetoresistance model diagram in this application;

[0058] Figure 4 It is a schematic diagram of the three-dimensional structure of the present invention;

[0059] Figure 5 Schematic diagram of a current source dual active bridge converter in this embodiment;

[0060] Figure 6 The flowchart of the transformer magnetic integration method for integrating dual DC inductors and leakage inductance. DETAILED DESCRIPTION

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

[0062] like Figure 1-4 As shown, the present invention proposes a transformer magnetic integrated structure integrating dual DC inductors and leakage inductors, including an EE magnetic core, a primary winding N p1 and N p2 , secondary winding Ns1 and N s2 The EE core has three magnetic columns, namely the first magnetic column, the second magnetic column and the third magnetic column. The first magnetic column and the third magnetic column are respectively located on both sides of the second magnetic column. The magnetic flux directions of the first magnetic column and the third magnetic column are the same and opposite to the magnetic flux direction of the second magnetic column. The first magnetic column, the second magnetic column and the third magnetic column are respectively provided with air gaps. The primary winding N p1 Located on the first magnetic column and forming a port 1 thereon, the primary winding N p2 Located on the third magnetic column and forming port 2 thereon, the secondary winding N s1 and N s2 They are respectively located on the first magnetic column and the third magnetic column and form port three after being connected in series.

[0063] The primary winding N p1 and N p2 Multiplexed into dual DC inductor winding N L1 、N L1 and transformer primary winding N p , the secondary winding N s1 and N s2 is 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 is the dual DC inductor current i L1 、i L2 Superimposed transformer primary winding current i p , satisfying formula (2):

[0066] (2).

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

[0068] (3)

[0069] Among them, R1 and R2 are the air gap magnetic resistance of the first and third magnetic columns respectively, R cis the air gap reluctance of the second magnetic column. Since the magnetic permeability of the EE core is much greater than that of air, the magnetic core reluctance can be ignored. R1 and R2 are the air gap reluctances of the two side columns of the EE core respectively. To simplify the design, the air gap reluctances of the two side columns are usually equal, that is, R1=R2=R p

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

[0071] (4)

[0072] Among them, L a and L b They are respectively the primary winding N p1 and N p2 Self-perception, M ab is the primary winding N p1 and N p2 Mutual inductance, M ac and M bc They are respectively the primary winding N p1 and the secondary winding N s1 +N s2 Intermediate and primary winding N p2 and the secondary winding N s1 +N s2 Mutual inductance, L c is the secondary winding N s1 +N s2 Therefore, the design of the magnetic integrated transformer can be regarded as the design of the multi-winding coupled inductor L.

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

[0074] (5)

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

[0076] The single EE core is a standard EE core. The air gaps on the first magnetic column, the second magnetic column, and the third magnetic column are located in the middle of each. The first cross column and the second cross column are fixed at both ends of the first cross column and the second cross column.

[0077] Example: Taking a commonly used current source dual active bridge dc-dc converter as an example, the effectiveness and feasibility of the transformer magnetic integration structure with integrated dual DC inductors and leakage inductors and the design method disclosed in the present invention are explained.

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

[0079] The positive electrode of the primary DC power supply is connected to the two DC inductors at point e, and the negative electrode of the primary DC power supply is connected to the source of the switching device Q2 and the clamping capacitor C c The drain of the switch tube Q1 is connected to the switch tube Q 1a The source of the switch tube Q2 is connected to the drain of the switch tube Q2. 2a The source of the switch is connected to the DC inductor L2 at point b. 1a The drain and clamping capacitor C c The other end and Q 2a The drain of the DC inductor L1 is connected to point a. The DC inductor L1 is connected in series with the 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 At the same time, the source of the switch tube S1 and the drain of the switch tube S3 are connected to point c, and the high-frequency transformer T rThe secondary winding of the MOSFET is connected to the source of switch S2 and the drain of switch S4 at point d. The drain of switch S1 is connected to the drain of switch S2 and the positive electrode of output capacitor C, and is also connected to the positive electrode of the output voltage. The source of switch S3 is connected to the source of switch S4 and the negative electrode of output capacitor C, and is also connected to the negative electrode of the output voltage.

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

[0081] S1: Under the premise of realizing soft switching of all switch tubes and the current source dual active bridge dc-dc converter working at a small current effective value, determine the required transformer parameters, including dual DC inductors L1 and L2, leakage inductance L r , transformation ratio N p :N s , the coupling coefficient K of the column windings on both sides;

[0082] S2: The multi-winding coupled inductance matrix L is equivalent to the transformer parameters. According to formula (5), the number of winding turns N of the single EE core is calculated. p1 、N p2 、N s1 、N s2 and air gap reluctance 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 columns on both sides.

[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 according to the converter operating frequency.

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

[0088] (7)

[0089] Here, μ0 is the magnetic permeability of vacuum. Thus, the design of magnetic integrated transformer based on a single EE core is completed.

[0090] According to the magnetic integrated transformer parameters of steps S1 to S5, the DC inductor, leakage inductor and transformer are integrated into a single standard EE core. The magnetic integrated structure integrates four magnetic components, including dual DC inductors, leakage inductors and transformers. The transformer magnetic integrated structure can reduce the number of magnetic components of the converter, reduce the volume ratio of magnetic components in the converter, and thus reduce the volume of the converter system, reduce the loss of magnetic components, and achieve high efficiency and high power density operation of the system. In addition, the DC inductor, leakage inductor and transformer turns ratio are only related to the number of winding turns and magnetic resistance. Therefore, by adjusting the number of winding turns and air gap magnetic resistance of a single EE core, the inductance parameters and transformer turns ratio can be flexibly controlled, simplifying the core design and reducing the complexity of the magnetic integrated structure. Finally, due to the presence of the column air gap in the transformer magnetic integrated structure, the column windings N on both sides are p1 and N p2 There is a natural coupling relationship between the two sides of the column winding, which can effectively suppress the unbalanced current between the windings and improve the stability and reliability of the system operation.

[0091] In the embodiment, the primary full bridge and the secondary full bridge of the current source dual active bridge DC-DC converter can adopt 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 The ports 1 and 2 formed are connected to point e to the midpoints a and b of the primary full bridge arms respectively, and the secondary winding N s1 and N s2 The ports 3 formed in series are respectively connected to the midpoints c and d of the bridge arms of the secondary full bridge. Under the magnetic integration structure, through the access of the original secondary DC power supply and the driving of the switch tube, the magnetic integration transformer assists the converter in realizing the power transmission of the dual active bridge DC-DC converter.

[0093] Through the above analysis, it can be seen that the present invention can optimize the transformer for achieving electrical isolation of the converter, increase the control freedom, and more flexibly assist the converter in performing bidirectional power transmission under soft switching in the full load range, reduce the volume proportion and loss occupied by the converter's magnetic components, improve the converter's power density and operating efficiency, and naturally achieve the effect of suppressing unbalanced currents on the column windings on both sides, thereby improving the stability and reliability of the converter's operation.

[0094] It should be noted that the above-mentioned specific description further details the purpose, technical solution and beneficial effects of the invention. The magnetic integration structure is applied to the current source dual active bridge converter, and is not intended to limit the scope of protection of the present invention to this topology. Any modifications, equivalent replacements, improvements, etc. made on the basis of the present invention should be included in the scope of protection of the present invention. The magnetic integration structure and magnetic integrated transformer design method proposed in the present 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 of the converter.

Claims

1. A transformer magnetic integration structure integrating dual DC inductors and leakage inductors, characterized by: Including EE core, primary winding N p1 and N p2 , secondary winding N s1 and N s2 The EE core has three magnetic columns, namely the first magnetic column, the second magnetic column and the third magnetic column. The first magnetic column and the third magnetic column are respectively located on both sides of the second magnetic column. The magnetic flux directions of the first magnetic column and the third magnetic column are the same and opposite to the magnetic flux direction of the second magnetic column. The first magnetic column, the second magnetic column and the third magnetic column are respectively provided with air gaps. The primary winding N p1 Located on the first magnetic column and forming a port 1 thereon, the primary winding N p2 Located on the third magnetic column and forming port 2 thereon, the secondary winding N s1 and N s2 They are respectively located on the first magnetic column and the third magnetic column and form port three after being connected in series.

2. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1, characterized in that: The primary winding N p1 and N p2 Multiplexed into dual DC inductor winding N L1 、N L1 and transformer primary winding N p , the secondary winding N s1 and N s2 is the secondary winding N of the transformer s , the primary winding and the secondary winding satisfy formula (1): (1)。 3. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1, characterized in that: The current i flowing through the primary winding a 、i b is the dual DC inductor current i L1 、i L2 Superimposed transformer primary winding current i p , satisfying formula (2): (2)。 4. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1 or 3, characterized in that: The magnetic fluxes of the first and third magnetic columns are ϕ1 and ϕ2 respectively, and the magnetic flux of the second magnetic column is ϕ c , the flux relationship is solved by the magnetic integrated transformer reluctance model, as shown in formula (3): (3) Among them, R1 and R2 are the air gap magnetic resistance of the first and third magnetic columns respectively, R c is the air gap reluctance of the second magnetic column, According to Faraday's law of electromagnetic induction and formula (2), the inductance matrix is shown in formula (4): (4) Among them, L a and L b They are respectively the primary winding N p1 and N p2 Self-perception, M ab is the primary winding N p1 and N p2 Mutual inductance, M ac and M bc They are respectively the primary winding N p1 and the secondary winding N s1 +N s2 Intermediate and primary winding N p2 and the secondary winding N s1 +N s2 Mutual inductance, L c is the secondary winding N s1 +N s2 Therefore, the design of the magnetic integrated transformer can be regarded as the design of the multi-winding coupled inductor L. The equivalent relationship between the multi-winding coupled inductor L and the transformer parameters required by the converter is shown in formula (5): (5) Among them, L m1 and L m2 are the equivalent magnetizing inductance of the winding, and the equivalent magnetizing inductance is used as the DC inductance, N p :N s is the transformer equivalent ratio, L r_ab is the equivalent leakage inductance.

5. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1, characterized in that: The single EE magnetic core is a standard EE magnetic core.

6. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1, characterized in that: The air gaps on the first magnetic column, the second magnetic column and the third magnetic column are respectively located in the middle of each.

7. The transformer magnetic integrated structure integrating dual DC inductors and leakage inductors according to claim 1, characterized in that: It also includes a first transverse column and a second transverse column, and two ends of the first magnetic column, the second magnetic column and the third magnetic column are fixed on the first transverse column and the second transverse column respectively.

8. The transformer magnetic integration method for integrating dual DC inductors and leakage inductors according to any one of claims 1 to 7, characterized in that: The steps include: S1: Determine the transformer parameters required to achieve the converter's operating performance, including the dual DC inductors L1 and L2, the leakage inductance L r , transformation ratio N p :N s , the coupling coefficient K of the column windings on both sides; S2: The multi-winding coupled inductance matrix L is equivalent to the transformer parameters. According to formula (5), the number of winding turns N of the single EE core is calculated. p1 、N p2 、N s1 、N s2 and air gap reluctance 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 columns on both sides; S4: Determine the core cross-sectional area based on the maximum magnetic flux, as shown in formula (6): (6) Among them, B recommed According to the converter operating frequency selection, S5: Determine the air gap length of the transformer magnetic integrated structure, as shown in formula (7): (7) Where μ0 is the magnetic permeability of vacuum. Thus, the design of magnetic integrated transformer based on a single EE core is completed.

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