Three-port transformer integrated with common mode choke

Abstract

The invention discloses a three-port transformer integrated with a common-mode inductor, and belongs to the power electronic technology. The single-stage ACAC three-port converter solves the problem that an existing single-stage ACAC three-port converter needs two transformers and a common-mode inductor with a large inductance value to achieve the single-stage ACAC three-port converter, and consequently the total size of the single-stage ACAC three-port converter is large. The magnetic core comprises primary side windings N1 and N2 wound on the primary side of the magnetic core, and secondary side windings N3-N5 wound on the secondary side of the magnetic core, the number of turns of the primary side winding N1 is the same as that of the primary side winding N2, the number of turns of the secondary side winding N4 is the same as that of the secondary side winding N5, and at the moment, leakage inductance Lf1 wound by the number of turns of the primary side winding N1 on the primary side of the transformer and leakage inductance Lf2 wound by the number of turns of the primary side winding N2 on the primary side of the transformer serve as common-mode inductors integrated on the primary side of the transformer. The single-stage ACAC three-port converter is mainly applied to the single-stage ACAC three-port converter to supply power to a high-voltage battery and a low-voltage battery of an electric vehicle.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and particularly relates to a three-port transformer integrated with a common-mode inductor, which is applied to a single-stage AC-AC three-port converter. Background Art

[0002] In response to the global net-zero emissions target, automakers have stepped up their electrification goals. Transformers play a key role in electric vehicles as they connect the high-voltage battery to the low-voltage battery and are responsible for transferring power from the grid side between the two batteries. As circuit topologies become increasingly complex, the requirements for transformer structures are becoming more diverse. Currently, there are two-port transformers with center taps, such as Figure 1 shown, and this two-port transformer has two different usage methods according to different required functions.

[0003] (1) The three points a, b, and n are the ports for the grid-side input to the primary side of the transformer, and c, d are the ports for output to the secondary-side topology.

[0004] (2) c, d are the ports for input to the primary side of the transformer, and the three points a, b, and n are the ports for output to the secondary-side topology.

[0005] An electric vehicle has two batteries, one is a high-voltage battery of 270 - 470V, and the other is a low-voltage battery of 12V - 13V. The high-voltage battery is responsible for starting and running the vehicle motor, and the low-voltage battery is responsible for functions such as lighting and charging in the electric vehicle. Currently, a single-stage AC-AC three-port converter is implemented by two transformers with center taps. One is a level-conversion transformer T1 from the 220V grid-side voltage to the 270 - 470V high-voltage battery, and the other is a level converter T2 from the 470V high-voltage battery to the 12V - 13V low-voltage battery, as Figure 2 shown. And a common-mode inductor and a grid-side filter inductor are externally connected to the grid side of the transformer T1.

[0006] For the former, the core model of the 6.6kW two-port transformer T1 with a center tap is E65 / 32 / 13 of Ferroxcube, and the total volume of the transformer is about 0.5L; for the latter, the volume of the 3.3kW two-port transformer T2 with a center tap is about 0.2L. For the circuit topology of this single-stage AC-AC three-port converter, the required common-mode inductor has a total inductance value of 22uH and a current-carrying capacity of 40A. However, the existing common-mode inductors on the market cannot carry a current of 40A and have a total inductance value of 22uH. Since such a common-mode inductor simply does not exist, a common-mode inductor with a larger inductance value is required to carry a current of 40A, which leads to an increase in the overall volume of the system. A larger inductance value also causes a larger voltage to be generated on it for the same current change rate, increasing the requirement for the voltage stress of the system switching transistors. Switches with a higher breakdown voltage and higher cost are needed to implement the functions of the system, resulting in poor versatility. Summary of the Invention

[0007] The object of the present invention is to solve the problem that the overall volume of the existing single-stage AC-AC three-port converter is relatively large due to the implementation of two transformers and a common-mode inductor with a relatively large inductance value. The present invention provides a three-port transformer integrated with a common-mode inductor, and this transformer integrates a common-mode inductor.

[0008] The three-port transformer integrated with a common-mode inductor includes a primary winding N wound around the primary side of the core 1 and N 2 , and a secondary winding N wound around the secondary side of the core 3 to N 5 ;

[0009] The non-corresponding end of the primary winding N 1 is connected to the corresponding end of the primary winding N 2 , and is used as the primary center tap n; and the corresponding end a of the primary winding N 1 , the primary center tap n, and the non-corresponding end b of the primary winding N 2 form a port as the grid side port on the primary side of the transformer;

[0010] The port formed between the corresponding end c and the non-corresponding end d of the secondary winding N 3 is used as the high-voltage battery side port of the transformer;

[0011] The non-corresponding end of the secondary winding N 4 is connected to the corresponding end of the secondary winding N 5 , and is used as the secondary center tap f; and the corresponding end e of the secondary winding N 4 , the secondary center tap f, and the non-corresponding end g of the secondary winding N 5 form a port as the low-voltage battery side port of the transformer;

[0012] Primary side winding N 1 and the primary side winding N 2 have the same number of turns. The secondary side winding N 4 and the secondary side winding N 5 also have the same number of turns. At this time, the leakage inductance L 1 induced by winding the number of turns of the primary side winding N f1 of the primary side of the transformer is taken as the common mode inductance integrated in the primary side of the transformer together with the leakage inductance L 2 induced by winding the same number of turns as the primary side winding N f2 .

[0013] Preferably, the magnetic core is an EE-type magnetic core.

[0014] Preferably, the model of the EE-type magnetic core is EE50 / 22 / 15-LP9.

[0015] Preferably, the winding types of the primary side windings N 1 and N 2 , as well as the secondary side windings N 3 to N 5 are film-covered wires.

[0016] Preferably, the winding method is a wire coil.

[0017] Advantages of the present invention:

[0018] In the present invention, the leakage inductance L 1 induced by winding the number of turns of the primary side winding N f1 of the primary side of the transformer is taken as the common mode inductance integrated in the primary side of the transformer together with the leakage inductance L 2 induced by winding the same number of turns as the primary side winding N f2 . This omits the need to externally connect a common mode inductance outside the transformer in the existing single-stage AC-AC three-port converter, and integrates the two transformers used in the existing single-stage AC-AC three-port converter into one transformer, reducing the number of transformers used and the overall volume of the transformer and the converter. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a two-port transformer with a center tap in the background art;

[0020] Figure 2 is a circuit topology diagram of a single-stage AC-AC three-port converter using a dual transformer;

[0021] Figure 3 is a schematic principle diagram of a three-port transformer integrating a common mode inductance according to the present invention;

[0022] Figure 4It is a schematic structural diagram of a three - port transformer of the integrated common - mode inductor embodying the present invention;

[0023] Figure 5 It is a circuit topology diagram of a single - stage AC - AC three - port converter using the three - port transformer of the integrated common - mode inductor of the present invention;

[0024] Figure 6 It is a three - dimensional diagram of the three - port transformer of the integrated common - mode inductor of the present invention;

[0025] Figure 7 It is a model diagram of the three - port transformer of the integrated common - mode inductor of the present invention;

[0026] Figure 8 It is a model diagram for loss analysis of the three - port transformer of the present invention;

[0027] Figure 9 It is a BP curve diagram of the loss curve of the EE50 / 22 / 15 - LP9 type magnetic core;

[0028] Figure 10 It is a schematic diagram of the EE50 / 22 / 15 - LP9 type magnetic core;

[0029] Figure 11 It is a schematic diagram of the winding - winding method of the three - port transformer of the integrated common - mode inductor of the present invention.

[0030] In the drawings, v g is the 220V grid - side voltage, v cd is the voltage between point c and point d, v c′d′ is the voltage between point c′ and point d′, i dc is the output current of the rectifier bridge, i s is the output current of the high - voltage battery - side winding of the transformer, i LV is the output current of the low - voltage battery - side, C HV1 、C HV2 and C dc3 are all filter capacitors, C c is the bus capacitor, D 1 to D 2 are all rectifier diodes, D 3 is the free - wheeling diode, S 1 to S 10 、and S buck are all power switch tubes, i P1 and i P2 respectively represent the currents on the windings of the transformer grid - side with turns N 1 and N 2 , the windings L diff1 and the winding L diff2 constitute the common - mode inductor, L LVis a filter inductor. Detailed implementation mode

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0032] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0033] Detailed implementation mode one, in combination with Figure 3 and Figure 4 This implementation mode is described. The three-port transformer of the integrated common-mode inductor described in this implementation mode includes a primary winding N 1 and N 2 wound on the primary side of the magnetic core, and a secondary winding N 3 to N 5 wound on the secondary side of the magnetic core;

[0034] After the opposite-named end of the primary winding N 1 is connected to the same-named end of the primary winding N 2 , it serves as the primary center tap n; and the same-named end a of the primary winding N 1 , the primary center tap n, and the opposite-named end b of the primary winding N 2 form a port as the grid side port on the primary side of the transformer;

[0035] The port formed between the same-named end c and the opposite-named end d of the secondary winding N 3 serves as the high-voltage battery side port of the transformer;

[0036] After the opposite-named end of the secondary winding N 4 is connected to the same-named end of the secondary winding N 5 , it serves as the secondary center tap f; and the same-named end e of the secondary winding N 4 , the secondary center tap f, and the opposite-named end g of the secondary winding N 5 form a port as the low-voltage battery side port of the transformer;

[0037] The turns of the primary winding N 1 and the primary winding N 2 are the same, and the turns of the secondary winding N 4 and the secondary winding N 5 are the same. At this time, the leakage inductance L 1 wound by the turns of the primary winding N f1The leakage inductance L wound with the number of turns of the original side winding N 2 is used as the common-mode inductance integrated on the primary side of the transformer. f2

[0038] For the schematic diagram of applying the three-port transformer with integrated common-mode inductance described in this embodiment to a single-stage AC-AC three-port converter, see Figure 5 ; In specific applications, the high-voltage battery side port is connected to the high-voltage battery of the tram through a rectifier circuit, and the low-voltage battery side port of the transformer can be output to the low-voltage battery of the tram through a rectifier circuit.

[0039] The three-port transformer with integrated common-mode inductance winds out the leakage inductance L of the primary side winding N 1 of the transformer as the common-mode inductance integrated on the primary side of the transformer, omitting the need to externally connect a common-mode inductance outside the transformer in the existing single-stage AC-AC three-port converter, and integrating the two transformers used in the existing single-stage AC-AC three-port converter into one transformer, reducing the number of transformers used and the overall volume of the transformer. f1 The leakage inductance L wound with the number of turns of the original side winding N 2 is used as the common-mode inductance integrated on the primary side of the transformer. f2

[0040] In specific applications, an EE-type magnetic core can be used. Further, the model of the EE-type magnetic core is EE50 / 22 / 15-LP9. As Figure 10 shown. This magnetic core is commonly used in high-frequency switching power supplies, high-power inductors, and photovoltaic inverters. The volume parameters of this magnetic core are shown in Table 1.

[0041] Table 1 Volume parameter table of EE50 / 22 / 15-LP9

[0042]

[0043] The magnetic core parameter table of the magnetic core is shown in Table 2.

[0044] Table 2 Magnetic core parameters and inductance factor table of EE50 / 22 / 15-LP9

[0045]

[0046] First, design the number of turns from the grid side to the high-voltage side. Calculate the number of turns of the magnetic core winding according to the index table of the transformer and the parameter table of the selected magnetic core. N 1 and N 2 are the primary side windings of the primary side. To ensure that the magnetic core does not saturate magnetically, it is necessary to ensure that the number of turns of N 1 and N 2 are the same, and the number of turns of N 4 and N 5 ​​The number of turns is the same. The magnetic core is wound, the winding type is selected as film-insulated wire, and the winding method is selected as coil, as shown in Figure 11 shown.

[0047] Verification test:

[0048] Through the following verification tests, the effectiveness of the present invention is verified, specifically:

[0049] The integrated design of the transformer for the three-port converter is realized. This design realizes two functions of level conversion from the 220V grid-side voltage to the high-voltage battery and level conversion from the high-voltage battery to the low-voltage battery through a three-port transformer, and realizes two functions through one magnetic core, which not only increases the utilization rate of the magnetic core, but also reduces the volume compared with the dual transformer. The final volume of the three-port transformer with an integrated common-mode inductor is only 0.523L. As shown in Figure 6 shown, the length of the transformer is 158mm, the width is 51mm, and the height is 65mm.

[0050] For the model diagram of the three-port transformer with an integrated common-mode inductor described in the present invention, see Figure 7 , for the loss analysis model diagram of the three-port transformer of the present invention, see Figure 8 , Figure 9 is the BP curve of the magnetic core, and the eddy current field simulation is carried out with Maxwell software. Figure 9 The four curves in it respectively refer to the curves of the power loss of the magnetic core varying with the magnetic field strength when the operating frequency of the magnetic core is 100kHz, 200kHz, 300kHz, 400kHz, and 500kHz. It can be obtained from Figure 9 that when the transformer is at a system frequency of 100kHz and a magnetic induction intensity of 100mT, its power loss is 40W / cm 3 ; when the transformer is under the conditions of 100kHz, power 6.6kW, input voltage 220V, high-voltage battery output voltage 450 - 900V, and low-voltage battery output voltage 10 - 16V, the total loss of the three-port transformer of the present invention is 140W. The transformer is a 6.6kW transformer, and its overall efficiency is 97.8%.

[0051] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A three-port transformer with integrated common-mode inductor, comprising primary windings N1 and N2 wound on the primary side of a magnetic core, and secondary windings N3 to N5 wound on the secondary side of the magnetic core; It is characterized in that After the opposite-name end of the primary winding N1 is connected to the same-name end of the primary winding N2, it serves as the primary center tap n; and the port formed by the same-name end a of the primary winding N1, the primary center tap n and the opposite-name end b of the primary winding N2 serves as the grid-side port of the primary side of the transformer; The port formed between the same-name terminal c and the opposite-name terminal d of the secondary winding N3 serves as the high-voltage battery side port of the transformer; After the opposite-name end of the secondary winding N4 is connected to the same-name end of the secondary winding N5, it serves as the secondary center tap f; and the port formed by the same-name end e of the secondary winding N4, the secondary center tap f and the opposite-name end g of the secondary winding N5 serves as the low-voltage battery side port of the transformer; The number of turns of the primary winding N1 is the same as that of the primary winding N2, and the number of turns of the secondary winding N4 is the same as that of the secondary winding N5. At this time, the leakage inductance L is wound by the number of turns of the primary winding N1 on the primary side of the transformer. f1 The leakage inductance L of the primary winding N2 turns is f2 , as the common-mode inductor integrated in the primary side of the transformer.

2. The three-port transformer with integrated common-mode inductor according to claim 1, characterized in that: The magnetic core adopts EE type magnetic core.

3. The three-port transformer with integrated common-mode inductor according to claim 2, characterized in that: The model of EE type core is EE50 / 22 / 15-LP9.

4. The three-port transformer with integrated common-mode inductor according to claim 1, characterized in that: The winding type of the primary windings N1 and N2 and the secondary windings N3 to N5 is film-wrapped wire.

5. The three-port transformer with integrated common-mode inductor according to claim 1, characterized in that: The winding method is coiled wire.

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