Transformer winding coupled low-voltage side parallel self-current-sharing dual-active full-bridge converter

Abstract

The invention discloses a transformer winding coupled low-voltage side parallel self-current-sharing dual-active full-bridge converter. The transformer winding coupled low-voltage side parallel self-current-sharing dual-active full-bridge converter comprises two low-voltage side parallel switching circuits, two isolation transformers, a series inductor and a high-voltage side switching circuit, the first isolation type transformer T1 is provided with a primary winding and two identical secondary windings, namely a first primary winding Np1, a first secondary winding Ns11 and a second secondary winding Ns12; the second isolation type transformer T2 is provided with a primary winding and two identical secondary windings, namely a first primary winding Np2, a first secondary winding Ns21 and a second secondary winding Ns22; the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the second secondary winding Ns12 and the second secondary winding Ns22 are connected in series; the influence of circuit parameter differences such as full-bridge module equivalent impedance and transformer leakage inductance of the low-voltage side parallel circuit on system current sharing can be eliminated, and the method has wide application scenes in low-voltage large-current scenes such as energy storage and direct-current micro-grids.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic cascade, and in particular to a transformer winding-coupled low-voltage side parallel self-current-sharing dual-active full-bridge converter. Background Art

[0002] In recent years, converters in power electronic systems are developing towards high power, integration, low cost, high power density and high efficiency. The dual active bridge converter has many advantages such as bidirectional power transmission, electrical isolation, high ratio buck-boost, and easy soft switch control. It has developed into one of the core topologies of high-power parallel switching power supplies in new energy power generation, electric vehicles, aerospace, uninterruptible power supplies, DC distribution systems, energy storage systems and other occasions. In low-voltage and high-current situations, due to the current resistance level of power electronic devices, the low-voltage side circuit of the dual active full-bridge converter cannot meet the current stress requirements. At this time, the most commonly used solution is to expand the capacity of multiple H-bridge modules in parallel on the low-voltage side. However, due to the mismatch of circuit parameters such as transformer leakage inductance and H-bridge equivalent impedance, the parallel H-bridge modules cannot achieve current sharing. The current stress of each module is collected by the current sensor, and the phase shift angle between the H-bridges on both sides of the transformer can be adjusted to achieve current sharing of the parallel circuit on the low-voltage side, but the current sensor and its supporting sampling circuit increase the cost of the system. IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol. 66, No. 9, “Dual-Active-Bridge Converter With Parallel-Connected Full Bridges in Low-Voltage Side for ZVS by Using Auxiliary Coupling Inductor” proposed a low-voltage side parallel self-current equalizing converter based on coupled inductors. Current equalization is achieved by adding an auxiliary coupled inductor between the two H-bridge modules, but this solution increases the size of the system. Summary of the invention

[0003] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art. The present invention proposes a low-voltage side parallel self-current equalizing dual-active full-bridge converter coupled with transformer windings, which can realize automatic current equalization of the low-voltage side parallel circuit through transformer coupling without adding any additional control, thereby reducing costs.

[0004] The technical solution to achieve the purpose of the present invention is:

[0005] A transformer winding coupled low voltage side parallel self-current balancing dual active full bridge converter, comprising:

[0006] The low-voltage side parallel self-current-sharing dual-active full-bridge converter includes a first switch circuit S11, a second switch circuit S12, a third switch circuit S13, and capacitors C11, C12, and C13 on the DC port side of the converter, a first isolation transformer T1, a first isolation transformer T2, and a first series inductor L1. The first switch circuit S11 has an input port 1-1 and an output port 1-2, the second switch circuit S12 has an input port 1-3 and an output port 1-4, and the third switch circuit S13 has an input port 1-5 and an output port 1-6;

[0007] The first isolation transformer T1 has one primary winding and two identical secondary windings, including a first primary winding Np1, a first secondary winding Ns11, and a second secondary winding Ns12; the second isolation transformer T2 has one primary winding and two identical secondary windings, including a first primary winding Np2, a first secondary winding Ns21, and a second secondary winding Ns22; the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the second secondary winding Ns12 and the second secondary winding Ns22 are connected in series.

[0008] Furthermore, the turns ratio between one primary winding and two identical secondary windings of the first isolation transformer T1 is n1:n2:n2; the turns ratio between one primary winding and two identical secondary windings of the second isolation transformer T2 is also n1:n2:n2.

[0009] Furthermore, the like-named ends of the first secondary winding Ns11 and the like-named ends of the second secondary winding Ns12 in the first isolation transformer T1 are connected together, and the connection point is P+; the opposite-named ends of the first secondary winding Ns21 and the opposite-named ends of the second secondary winding Ns22 in the second isolation transformer T2 are connected together, and the connection point is N+.

[0010] Furthermore, the first series inductor L1 is respectively connected to the P+ terminal and the input positive interface of the second switch circuit S12 input port 1-3, and the N+ terminal is connected to the input negative interface of the second switch circuit S12 input port 1-3.

[0011] Furthermore, the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the series branch currents are equal, which is defined as i s1 The second secondary winding Ns12 and the second secondary winding Ns22 are connected in series, and the series branch currents are equal and defined as i s2 , the first primary winding current of the first isolation transformer T1 is i p1 , and the relationship with the secondary winding current is:

[0012]

[0013] Wherein, n=(n1) / (n2+n2); the first primary winding current of the second isolation transformer T2 is i p2 , and the relationship with the secondary winding current is:

[0014]

[0015] From formula (1) and (2), we can find that:

[0016] i p1 =i p2 (3)

[0017] At this time, the first switch circuit S11 and the third switch circuit S13 automatically achieve current sharing without any additional control.

[0018] Compared with the prior art, the present invention adopts the above technical solution and has the following beneficial effects:

[0019] 1. The transformer winding-coupled low-voltage side parallel self-current-equalizing dual-active full-bridge converter proposed in the present invention can realize automatic current equalization of the low-voltage side parallel circuit by transformer coupling, without adding any additional control, thus reducing the cost.

[0020] 2. The transformer winding-coupled low-voltage side parallel self-current-equalizing dual-active full-bridge converter proposed in the present invention can eliminate the influence of the low-voltage side parallel circuit on the system current equalization due to the differences in circuit parameters such as the equivalent impedance of the full-bridge module and the transformer leakage inductance, and is more suitable for low-voltage and high-current scenarios.

[0021] 3. The low-voltage side parallel self-current-sharing dual-active full-bridge converter with transformer winding coupling proposed in the present invention can reduce the system volume through transformer coupling and has a relatively simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 It is a structural schematic diagram of Embodiment 1 of the present invention;

[0024] Figure 3 It is a traditional low-voltage side parallel dual active full-bridge converter circuit topology;

[0025] Figure 4 The experimental waveforms of low-voltage side currents iL1 and iL2 of the traditional low-voltage side parallel dual active full-bridge converter circuit topology;

[0026] Figure 5 1 and 2 are experimental waveforms of the low-voltage side currents iL1 and iL2 of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] A transformer winding coupled low voltage side parallel self-current balancing dual active full bridge converter, comprising:

[0029] The low-voltage side parallel self-current-sharing dual-active full-bridge converter includes a first switch circuit S11, a second switch circuit S12, a third switch circuit S13, and capacitors C11, C12, and C13 on the DC port side of the converter, a first isolation transformer T1, a first isolation transformer T2, and a first series inductor L1. The first switch circuit S11 has an input port 1-1 and an output port 1-2, the second switch circuit S12 has an input port 1-3 and an output port 1-4, and the third switch circuit S13 has an input port 1-5 and an output port 1-6;

[0030] The first isolation transformer T1 has one primary winding and two identical secondary windings, including a first primary winding Np1, a first secondary winding Ns11, and a second secondary winding Ns12; the second isolation transformer T2 has one primary winding and two identical secondary windings, including a first primary winding Np2, a first secondary winding Ns21, and a second secondary winding Ns22; the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the second secondary winding Ns12 and the second secondary winding Ns22 are connected in series.

[0031] Furthermore, the turns ratio between one primary winding and two identical secondary windings of the first isolation transformer T1 is n1:n2:n2; the turns ratio between one primary winding and two identical secondary windings of the second isolation transformer T2 is also n1:n2:n2.

[0032] Furthermore, the like-named ends of the first secondary winding Ns11 and the like-named ends of the second secondary winding Ns12 in the first isolation transformer T1 are connected together, and the connection point is P+; the opposite-named ends of the first secondary winding Ns21 and the opposite-named ends of the second secondary winding Ns22 in the second isolation transformer T2 are connected together, and the connection point is N+.

[0033] Furthermore, the first series inductor L1 is respectively connected to the P+ terminal and the input positive interface of the second switch circuit S12 input port 1-3, and the N+ terminal is connected to the input negative interface of the second switch circuit S12 input port 1-3.

[0034] Furthermore, the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the series branch currents are equal, which is defined as i s1 The second secondary winding Ns12 and the second secondary winding Ns22 are connected in series, and the series branch currents are equal and defined as i s2 , the first primary winding current of the first isolation transformer T1 is i p1 , and the relationship with the secondary winding current is:

[0035]

[0036] Wherein, n=(n1) / (n2+n2); the first primary winding current of the second isolation transformer T2 is i p2 , and the relationship with the secondary winding current is:

[0037]

[0038] From formula (1) and (2), we can find that:

[0039] i p1 =i p2 (3)

[0040] At this time, the first switch circuit S11 and the third switch circuit S13 automatically achieve current sharing without any additional control.

[0041] In this implementation, Figure 2 The circuit parameters of the present invention are: the input voltage signal U of the dual active full-bridge converter in =48V, the output voltage signal U of the dual active full-bridge converter o =384V, the turns ratio of the first isolation transformer T1 and the second isolation transformer T2 is n=1:4:4, the inductance of the first series inductor L1 is L1=60uH, C 11 =C 12 =C 13 =400uF, the switching frequency of the first, second and third switch circuits fs1=50kHz, and the load power is 1kW.

[0042] In this embodiment, Figure 3 The circuit parameters of the traditional low-voltage side parallel dual active full-bridge converter circuit topology are: The input voltage signal U of the dual active full-bridge converter in =48V, the output voltage signal U of the dual active full-bridge converter o=384V, the turns ratio of the first isolation transformer T1 and the second isolation transformer T2 is n=1:8, the primary leakage inductance L of the first isolation transformer T1 p2 =0.2e-6, the primary leakage inductance L of the second isolation transformer T2 p1 =0.22e-6, the inductance of the first series inductor L1 = 60uH, C 11 =C 12 =C 13 =400uF, the switching frequency of the first, second and third switch circuits fs1=50kHz, and the load power is 1kW.

[0043] By the attached Figure 4 It can be seen that when the present invention is not adopted, the currents of the two low-voltage side currents iL1 and iL2 of the low-voltage side parallel dual active full-bridge converter are 22A and 19A respectively, and the current sharing error reaches 7.3%.

[0044] By the attached Figure 5 It can be seen that when the method of the present invention is adopted, the currents of the two low-voltage side currents iL1 and iL2 of the low-voltage side parallel dual active full-bridge converter are 20A and 20A respectively, the current simulation waveform is very balanced, and the low-voltage side circuit achieves perfect current sharing.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-voltage side parallel self-current-sharing dual-active full-bridge converter coupled with transformer windings, characterized in that: include: The low-voltage side parallel self-current-sharing dual-active full-bridge converter includes a first switch circuit S11, a second switch circuit S12, a third switch circuit S13, and capacitors C11, C12, and C13 on the DC port side of the converter, a first isolation transformer T1, a first isolation transformer T2, and a first series inductor L1. The first switch circuit S11 has an input port 1-1 and an output port 1-2, the second switch circuit S12 has an input port 1-3 and an output port 1-4, and the third switch circuit S13 has an input port 1-5 and an output port 1-6; The first isolation transformer T1 has one primary winding and two identical secondary windings, including a first primary winding Np1, a first secondary winding Ns11, and a second secondary winding Ns12; the second isolation transformer T2 has one primary winding and two identical secondary windings, including a first primary winding Np2, a first secondary winding Ns21, and a second secondary winding Ns22; the first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the second secondary winding Ns12 and the second secondary winding Ns22 are connected in series.

2. The transformer winding coupled low voltage side parallel self-current sharing dual active full bridge converter according to claim 1, characterized in that: The turns ratio between one primary winding and two identical secondary windings of the first isolation transformer T1 is n1:n2:n2; the turns ratio between one primary winding and two identical secondary windings of the second isolation transformer T2 is also n1:n2:n2.

3. The transformer winding coupled low voltage side parallel self-current sharing dual active full bridge converter according to claim 1, characterized in that: The like-named ends of the first secondary winding Ns11 and the like-named ends of the second secondary winding Ns12 in the first isolation transformer T1 are connected together, and the connection point is P+; the opposite-named ends of the first secondary winding Ns21 and the opposite-named ends of the second secondary winding Ns22 in the second isolation transformer T2 are connected together, and the connection point is N+.

4. The transformer winding coupled low voltage side parallel self-current sharing dual active full bridge converter according to claim 1, characterized in that: The first series inductor L1 is respectively connected to the P+ terminal and the input positive interface of the input port 1-3 of the second switch circuit S12, and the N+ terminal is connected to the input negative interface of the input port 1-3 of the second switch circuit S12.

5. The transformer winding coupled low voltage side parallel self-current balancing dual active full bridge converter according to claim 1, characterized in that: The first secondary winding Ns11 and the first secondary winding Ns21 are connected in series, and the series branch currents are equal, which is defined as i s1 The second secondary winding Ns12 and the second secondary winding Ns22 are connected in series, and the series branch currents are equal and defined as i s2 , the first primary winding current of the first isolation transformer T1 is i p1 , and the relationship with the secondary winding current is: Wherein, n=(n1) / (n2+n2); the first primary winding current of the second isolation transformer T2 is i p2 , and the relationship with the secondary winding current is: From formula (1) and (2), we can find that: i p1 =i p2 (3) At this time, the first switch circuit S11 and the third switch circuit S13 automatically achieve current sharing without any additional control.

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