Dual-active bridge direct current converter of six-switch reconfigurable network based on coupling inductor and modulation method of dual-active bridge direct current converter

Abstract

The invention relates to a dual-active bridge direct current converter of a six-switch reconfigurable network based on coupling inductors. The dual-active bridge direct current converter comprises a first port, a second port, two transformers, two inductors and two switch loops, one of the first port and the second port is used as a power supply end, and the other port is correspondingly used as a load end; the first port is connected with a series circuit of a first filter capacitor and a support capacitor, and the second port is connected with a second filter capacitor; the first switch loop is composed of switch tubes S1-S4, the second switch loop is composed of switch tubes G1-G6, the support capacitor series circuit is composed of support capacitors C1-C4, the first switch loop and the support capacitor series circuit are connected with the second switch loop through two transformers and two inductors, and the two inductors are coupling inductors. The dual-active-bridge direct-current converter can be switched between two working modes, the working area of the dual-active-bridge direct-current converter is expanded, reactive power and circulating current can be reduced, and therefore the conduction loss of the converter is reduced, and efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and particularly relates to a dual-active-bridge DC converter based on a six-switch reconfigurable network with coupled inductors and its modulation method. Background Art

[0002] In recent years, with the booming development of new energy technologies, power electronic conversion devices are facing higher performance challenges. In view of the technological breakthroughs in the converter in the directions of high power, high efficiency, and high power density, a large amount of research work has been carried out by scientific researchers. Especially in the field of low-voltage large-current bidirectional power conversion, the application demand shows a significant growth trend. Currently, the two mainstream circuit topologies in this field are LLC resonant converters and bidirectional active-bridge converters. The LLC converter, relying on its unique resonant characteristics, can achieve soft-switching operation of the switching tubes within the full load range, thereby obtaining a relatively high power conversion efficiency. However, when applied to the scenario of bidirectional power transmission, this converter needs to switch the control logic, resulting in an increase in control complexity. To adapt to the low-voltage large-current working conditions, researchers have improved the low-voltage side switching loop and adopted a full-wave rectifier circuit structure. However, this improved solution will cause voltage spike problems of the switching tubes during bidirectional operation, which has an adverse impact on the system reliability.

[0003] The bidirectional active-bridge converter, on the other hand, has the significant advantage of simple control logic and can achieve natural switching of bidirectional power. Under heavy load conditions, this topology can effectively reduce the switching losses through zero-voltage turn-on technology. However, this solution has obvious application limitations: when the system is operating under light load or there is a large voltage difference between the two ends, the soft-switching conditions of the switching tubes will be destroyed, resulting in a significant increase in switching losses. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-active-bridge DC converter based on a six-switch reconfigurable network with coupled inductors and its modulation method. This dual-active-bridge DC converter can switch between two operating modes, expand the operating region of the dual-active-bridge DC converter, reduce the reactive power and circulating current, thereby reducing the conduction loss of the converter and improving the efficiency.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a dual-active-bridge DC converter based on a six-switch reconfigurable network with coupled inductors, including a first port, a second port, two transformers, two inductors, and two switching loops; one of the first port and the second port is selectively used as the power supply end, and the other port is correspondingly used as the load end; a first filter capacitor C V1 is connected in series with a support capacitor on the first port, and a second filter capacitor C V2; The first switching circuit is composed of switching tubes S1 to S4, the second switching circuit is composed of switching tubes G1 to G6, the support capacitor series circuit is composed of support capacitors C1 to C4, and the first switching circuit and the support capacitor series circuit are connected to the second switching circuit through two transformers T1, T2 and two inductors L k1 、L k2 Connect the second switching circuit, and the two inductors L k1 、L k2 are coupling inductors.

[0006] Furthermore, both ends of the first filter capacitor C V1 are respectively connected to the positive and negative poles of the first port; the positive pole of the first port is simultaneously connected to the drain of the switching tube S1 and one end of the support capacitor C1; the negative pole of the first port is simultaneously connected to the source of the switching tube S4 and one end of the support capacitor C4; the source of the switching tube S1 is simultaneously connected to the drain of the switching tube S2 and one end of the primary side of the transformer T1; the other end of the primary side of the transformer T1 is connected to one end of the inductor L k1 ; the other end of the inductor L k1 is simultaneously connected to the other end of the support capacitor C1 and one end of the support capacitor C2; the other end of the support capacitor C2 is simultaneously connected to one end of the support capacitor C3, the source of the switching tube S2 and the drain of the switching tube S3; the source of the switching tube S3 is simultaneously connected to the drain of the switching tube S4 and one end of the inductor L k2 ; the other end of the inductor L k2 is connected to one end of the primary side of the transformer T2; the other end of the primary side of the transformer T2 is simultaneously connected to the other end of the support capacitor C3 and the other end of the support capacitor C4; both ends of the second filter capacitor C V2 are respectively connected to the positive and negative poles of the second port; the positive pole of the second port is simultaneously connected to the drains of the switching tubes G1 and G4; the negative pole of the second port is simultaneously connected to the sources of the switching tubes G3 and G6; the source of the switching tube G1 is simultaneously connected to the drain of the switching tube G2 and one end of the secondary side of the transformer T1; the other end of the secondary side of the transformer T1 is simultaneously connected to the sources of the switching tubes G4 and G5; the source of the switching tube G2 is simultaneously connected to the drain of the switching tube G3 and one end of the secondary side of the transformer T2; the other end of the secondary side of the transformer T2 is simultaneously connected to the sources of the switching tubes G5 and G6.

[0007] Furthermore, the dual-active-bridge DC converter has two operating modes, corresponding to two modulation methods; the dual-active-bridge DC converter switches between the two operating modes according to specific operating conditions to expand the operating range of the dual-active-bridge DC converter.

[0008] Furthermore, when the dual-active-bridge DC converter operates in Mode 1, it has 6 operating modes:

[0009] From time t0 to t2, the dual-active-bridge DC converter is in operating mode 1: At time t0, switches S2 and S3 are turned off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of switches S1 to S4; when the junction capacitances of switches S1 to S4 are fully charged and discharged, the anti-parallel diodes of switches S1 and S4 conduct; then, the currents of the two inductors L k1 and L k2 in the coupled inductor first decrease in the reverse direction to zero and then increase in the forward direction to time t2; at this time, the voltage k1 between node a1, which is commonly connected to the source of switch S1, the drain of switch S2, and one end of the primary side of transformer T1, and node b1, which is commonly connected to one end of support capacitor C2, the other end of support capacitor C1, and the other end of inductor L The voltage between node c1, which is commonly connected to the source of switch G4, the drain of switch G5, and the other end of the secondary side of transformer T1, and node d1, which is commonly connected to the source of switch G1, the drain of switch G2, and one end of the secondary side of transformer T1 Therefore, the current i k1 of inductor L L1 rises linearly;

[0010] From time t2 to t3, the dual-active-bridge DC converter is in operating mode 2: At time t2, switches G1 and G3 are turned off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer exciting inductors charge and discharge the junction capacitances of switches G1 to G3 simultaneously; when the junction capacitances of switches G1 to G3 are fully charged and discharged, the anti-parallel diode of switch G2 conducts; at this time, Therefore, i L1 decreases linearly until time t3;

[0011] From time t3 to t4, the dual-active-bridge DC converter is in operating mode 3: At time t3, switches G4 and G6 are turned off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer exciting inductors charge and discharge the junction capacitances of switches G4 to G6 simultaneously; when the junction capacitances of switches G4 to G6 are fully charged and discharged, the anti-parallel diode of switch G5 conducts; at this time, Therefore, i L1 rises linearly until time t4;

[0012] From time t4 to t6, the dual-active-bridge DC converter is in operating mode 4: At time t4, switches S1 and S4 are turned off; then, the currents of the two inductors L k1 and L k2The current charges and discharges the junction capacitances of switching transistors S1 - S4; when the charging and discharging of the junction capacitances of switching transistors S1 - S4 are completed, the anti-parallel diodes of switching transistors S2 and S3 conduct; then, the currents in the two inductors L k1 and L k2 in the coupled inductor first decrease linearly to zero in the positive direction and then increase in the reverse direction to time t6; at this time, Therefore, i L1 increases linearly;

[0013] At time t6 - t7, the dual-active-bridge DC converter is in operating mode 5: at time t6, switching transistor G2 turns off; then, the currents in the two inductors L k1 and L k2 in the coupled inductor and the currents in the two transformer magnetizing inductors charge and discharge the junction capacitances of switching transistors G1 - G3 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G1 - G3 are completed, the anti-parallel diodes of switching transistors G1 and G3 conduct. At this time, Therefore, i L1 increases linearly until time t7;

[0014] At time t7 - t8, the dual-active-bridge DC converter is in operating mode 6: at time t7, switching transistor G5 turns off; then, the currents in the two inductors L k1 and L k2 in the coupled inductor and the currents in the two transformer magnetizing inductors charge and discharge the junction capacitances of switching transistors G4 - G6 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G4 - G6 are completed, the anti-parallel diodes of switching transistors G4 and G6 conduct; at this time, Therefore, i L1 decreases linearly until time t8.

[0015] Furthermore, when the dual-active-bridge DC converter operates in mode 2, switching transistors G2 and G5 are always at a high level to keep them conducting. The dual-active-bridge DC converter has 6 operating modes:

[0016] At time t0 - t2, the dual-active-bridge DC converter is in operating mode 1: at time t0, switching transistors S2 and S4 turn off; then, the currents in the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of switching transistors S1 - S4; when the charging and discharging of the junction capacitances of switching transistors S1 - S4 are completed, the anti-parallel diodes of switching transistors S1 and S3 conduct; then, the currents in the two inductors L k1 and L k2 in the coupled inductor first decrease in the reverse direction to zero and then increase in the positive direction to time t2; at this time, Therefore, i L1 increases linearly;

[0017] At time t2 - t3, the dual - active - bridge DC - DC converter is in operating mode 2: At time t2, switch G1 turns off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer magnetizing inductors charge and discharge the junction capacitances of switches G1 and G3 simultaneously; when the junction capacitances of switches G1 and G3 are fully charged and discharged, the anti - parallel diode of switch G3 conducts; at this time, Therefore, i L1 decreases linearly until time t3;

[0018] At time t3 - t4, the dual - active - bridge DC - DC converter is in operating mode 3: At time t3, switch G4 turns off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer magnetizing inductors charge and discharge the junction capacitances of switches G4 and G6 simultaneously; when the junction capacitances of switches G4 and G6 are fully charged and discharged, the anti - parallel diode of switch G6 conducts; at this time, Therefore, i L1 increases linearly until time t4;

[0019] At time t4 - t6, the dual - active - bridge DC - DC converter is in operating mode 4: At time t4, switches S1 and S3 turn off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of switches S1 - S4; when the junction capacitances of switches S1 - S4 are fully charged and discharged, the anti - parallel diodes of switches S2 and S4 conduct; then, the currents of the two inductors L k1 and L k2 in the coupled inductor first decrease to zero in the forward direction and then increase in the reverse direction until time t6; at this time, Therefore, i L1 increases linearly;

[0020] At time t6 - t7, the dual - active - bridge DC - DC converter is in operating mode 5: At time t6, switch G3 turns off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer magnetizing inductors charge and discharge the junction capacitances of switches G1 and G3 simultaneously; when the junction capacitances of switches G1 and G3 are fully charged and discharged, the anti - parallel diode of switch G1 conducts, at this time, Therefore, i L1 increases linearly until time t7;

[0021] At time t7 - t8, the dual - active - bridge DC - DC converter is in operating mode 6: At time t7, switch G6 turns off; then, the currents of the two inductors L k1and L k2 The current of and the currents of the two transformer excitation inductances charge and discharge the junction capacitances of switching transistors G4 and G6 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G4 and G6 are completed, the anti-parallel diode of switching transistor G4 conducts; at this time, Therefore, i L1 linearly decreases until time t8.

[0022] Compared with the prior art, the present invention has the following beneficial effects: In order to overcome the problem of reduced efficiency caused by the operation of a dual-active-bridge converter when the output voltages do not match, the present invention proposes a dual-active-bridge DC converter based on a six-switch reconfigurable network with coupled inductors and its modulation method. The converter has two operating modes corresponding to two modulation methods, enabling the converter to switch between the two operating modes according to specific operating conditions, thereby expanding the operating region of the dual-active-bridge converter. When switching between different operating modes, reactive power and circulating current can be reduced, thereby reducing the conduction loss of the converter and improving the efficiency. With this solution, the converter can operate in different operating modes according to specific circumstances, thereby having a wide ZVS region load range within a wide voltage range. Description of the Drawings

[0023] Figure 1 is the topological structure diagram of the dual-active-bridge DC converter based on a six-switch reconfigurable network with coupled inductors provided by an embodiment of the present invention;

[0024] Figure 2 is the waveform diagram of the dual-active-bridge DC converter operating in Mode 1 in an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of Operating Mode 1 of the dual-active-bridge DC converter in Mode 1 in an embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of Operating Mode 2 of the dual-active-bridge DC converter in Mode 1 in an embodiment of the present invention;

[0027] Figure 5 is a schematic diagram of Operating Mode 3 of the dual-active-bridge DC converter in Mode 1 in an embodiment of the present invention;

[0028] Figure 6 is a schematic diagram of Operating Mode 4 of the dual-active-bridge DC converter in Mode 1 in an embodiment of the present invention;

[0029] Figure 7 is a schematic diagram of Operating Mode 5 of the dual-active-bridge DC converter in Mode 1 in an embodiment of the present invention;

[0030] Figure 8It is a schematic diagram of operating mode 6 of the dual-active-bridge DC converter in Mode 1 in the embodiments of the present invention;

[0031] Figure 9 It is a waveform diagram of the dual-active-bridge DC converter operating in Mode 2 in the embodiments of the present invention;

[0032] Figure 10 It is a schematic diagram of operating mode 1 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention;

[0033] Figure 11 It is a schematic diagram of operating mode 2 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention;

[0034] Figure 12 It is a schematic diagram of operating mode 3 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention;

[0035] Figure 13 It is a schematic diagram of operating mode 4 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention;

[0036] Figure 14 It is a schematic diagram of operating mode 5 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention;

[0037] Figure 15 It is a schematic diagram of operating mode 6 of the dual-active-bridge DC converter in Mode 2 in the embodiments of the present invention. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0040] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] This embodiment provides a dual-active-bridge DC converter based on a coupled-inductor six-switch reconfigurable network, which includes a first port, a second port, two transformers, two inductors, and two switch circuits; one of the first port and the second port can be selectively used as the power supply end, and the other port corresponds to the load end; a first filter capacitor C is connected to the first port V1 in series with a support capacitor series circuit, and a second filter capacitor C is connected to the second port V2 ; the first switch circuit is composed of switch tubes S1 to S4, the second switch circuit is composed of switch tubes G1 to G6, the support capacitor series circuit is composed of support capacitors C1 to C4, and the first switch circuit and the support capacitor series circuit are connected to the second switch circuit through two transformers T1, T2 and two inductors L k1 、L k2 ; among them, the two inductors L k1 、L k2 are coupled inductors, which are composed of an external inductor and the leakage inductance of the transformer.

[0042] As Figure 1 shown, the specific topological structure of the dual-active-bridge DC converter is: both ends of the first filter capacitor C V1 are respectively connected to the positive and negative poles of the first port; the positive pole of the first port is simultaneously connected to the drain of switch tube S1 and one end of support capacitor C1; the negative pole of the first port is simultaneously connected to the source of switch tube S4 and one end of support capacitor C4; the source of switch tube S1 is simultaneously connected to the drain of switch tube S2 and one end of the primary side of transformer T1; the other end of the primary side of transformer T1 is connected to one end of inductor L k1 ; the other end of inductor L k1 is simultaneously connected to the other end of support capacitor C1 and one end of support capacitor C2; the other end of support capacitor C2 is simultaneously connected to one end of support capacitor C3, the source of switch tube S2, and the drain of switch tube S3; the source of switch tube S3 is simultaneously connected to the drain of switch tube S4 and one end of inductor L k2 ; the other end of inductor L k2 is connected to one end of the primary side of transformer T2; the other end of the primary side of transformer T2 is simultaneously connected to the other ends of support capacitors C3 and C4; the second filter capacitor C V2Both ends thereof are respectively connected to the positive and negative electrodes of the second port; the positive electrode of the second port is simultaneously connected to the drain electrodes of switch tubes G1 and G4; the negative electrode of the second port is simultaneously connected to the source electrodes of switch tubes G3 and G6; the source electrode of switch tube G1 is simultaneously connected to the drain electrode of switch tube G2 and one end of the secondary side of transformer T1; the other end of the secondary side of transformer T1 is simultaneously connected to the source electrode of switch tube G4 and the drain electrode of switch tube G5; the source electrode of switch tube G2 is simultaneously connected to the drain electrode of switch tube G3 and one end of the secondary side of transformer T2; the other end of the secondary side of transformer T2 is simultaneously connected to the source electrode of switch tube G5 and the drain electrode of switch tube G6.

[0043] The dual-active-bridge DC converter has two working modes, corresponding to two modulation methods; the dual-active-bridge DC converter switches between the two working modes according to specific working conditions to expand the working area of the dual-active-bridge DC converter.

[0044] When the dual-active-bridge DC converter operates in Mode 1, its working waveform is as Figure 2 shown. There are 6 working modes in Mode 1, and each working mode is described in detail as follows.

[0045] At t0 - t2, the dual-active-bridge DC converter is in Working Mode 1: corresponding to Figure 3 , at t0, switch tubes S2 and S3 are turned off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of switch tubes S1 - S4; when the junction capacitances of switch tubes S1 - S4 are fully charged and discharged, the anti-parallel diodes of switch tubes S1 and S4 conduct; then, the currents of the two inductors L k1 and L k2 in the coupled inductor first decrease in the reverse direction to zero and then increase in the forward direction to t2; at this time, the voltage between the node a1 commonly connected by the source electrode of switch tube S1, the drain electrode of switch tube S2, and one end of the primary side of transformer T1 and the node b1 commonly connected by one end of support capacitor C2, the other end of support capacitor C1, and the other end of inductor L k1 is the voltage between the node c1 commonly connected by the source electrode of switch tube G4, the drain electrode of switch tube G5, and the other end of the secondary side of transformer T1 and the node d1 commonly connected by the source electrode of switch tube G1, the drain electrode of switch tube G2, and one end of the secondary side of transformer T1 is Therefore, the current i k1 of inductor L L1 rises linearly.

[0046] At t2 - t3, the dual-active-bridge DC converter is in Working Mode 2: corresponding to Figure 4 , at t2, switch tubes G1 and G3 are turned off; then, the currents of the two inductors L k1and L k2 The current of k2 and the currents of the exciting inductances of the two transformers charge and discharge the junction capacitances of switching transistors G1 - G3 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G1 - G3 are completed, the anti-parallel diode of switching transistor G2 conducts; at this time, Therefore, i L1 decreases linearly until time t3.

[0047] At t3 - t4, the dual - active - bridge DC - DC converter is in operating mode 3: corresponding to Figure 5 , at time t3, switching transistors G4 and G6 turn off; then, the currents of the two inductances L k1 and L k2 in the coupled inductor and the currents of the exciting inductances of the two transformers charge and discharge the junction capacitances of switching transistors G4 - G6 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G4 - G6 are completed, the anti - parallel diode of switching transistor G5 conducts; at this time, Therefore, i L1 increases linearly until time t4.

[0048] At t4 - t6, the dual - active - bridge DC - DC converter is in operating mode 4: corresponding to Figure 6 , at time t4, switching transistors S1 and S4 turn off; then, the currents of the two inductances L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of switching transistors S1 - S4; when the charging and discharging of the junction capacitances of switching transistors S1 - S4 are completed, the anti - parallel diodes of switching transistors S2 and S3 conduct; then, the currents of the two inductances L k1 and L k2 in the coupled inductor first decrease positively to zero and then increase negatively until time t6; at this time, Therefore, i L1 increases linearly.

[0049] At t6 - t7, the dual - active - bridge DC - DC converter is in operating mode 5: corresponding to Figure 7 , at time t6, switching transistor G2 turns off; then, the currents of the two inductances L k1 and L k2 in the coupled inductor and the currents of the exciting inductances of the two transformers charge and discharge the junction capacitances of switching transistors G1 - G3 simultaneously; when the charging and discharging of the junction capacitances of switching transistors G1 - G3 are completed, the anti - parallel diodes of switching transistors G1 and G3 conduct, at this time, Therefore, i L1 increases linearly until time t7.

[0050] At t7 - t8, the dual - active - bridge DC - DC converter is in operating mode 6: corresponding to Figure 8 , at time t7, switching transistor G5 turns off; then, the currents of the two inductances Lk1 and L k2 The current of L and the currents of the exciting inductances of the two transformers charge and discharge the junction capacitances of the switching transistors G4 to G6 simultaneously. When the charging and discharging of the junction capacitances of the switching transistors G4 to G6 are completed, the anti-parallel diodes of the switching transistors G4 and G6 conduct. At this time, Therefore, i L1 decreases linearly until time t8.

[0051] The above is the working process of the converter in one switching period under Mode 1. From the above analysis, it can be seen that within one period, v L1 and v L2 , i L1 and i L2 are symmetric. Therefore, only the waveforms of v L1 , i L1 are drawn in its working waveform diagram. The primary sides of the transformers T1 and T2 are connected in series across V in . This modulation method can control the amplitude of the secondary voltage of the transformer to be V2 / 2. The transmitted power can be changed by adjusting the phase difference of the switching transistors.

[0052] When the dual-active-bridge DC converter operates in Mode 2, its working waveform is as shown in Figure 9 . In this mode, the secondary switching transistors G2 and G5 are always in the open state. There are 6 working modes in Mode 2, and each of them is described in detail as follows.

[0053] The switching transistors G2 and G5 are always at a high level to keep them conducting.

[0054] At t0 - t2, the dual-active-bridge DC converter is in Working Mode 1: corresponding to Figure 10 , at t0, the switching transistors S2 and S4 are turned off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of the switching transistors S1 to S4; when the charging and discharging of the junction capacitances of the switching transistors S1 to S4 are completed, the anti-parallel diodes of the switching transistors S1 and S3 conduct; then, the currents of the two inductors L k1 and L k2 in the coupled inductor first decrease in the reverse direction to zero, and then increase in the forward direction to time t2; at this time, Therefore, i L1 increases linearly.

[0055] At t2 - t3, the dual-active-bridge DC converter is in Working Mode 2: corresponding to Figure 11 , at t2, the switching transistor G1 is turned off; then, the currents of the two inductors L k1 and L k2The current and the currents of the two transformer excitation inductances charge and discharge the junction capacitances of the switching transistors G1 and G3 simultaneously; when the charging and discharging of the junction capacitances of the switching transistors G1 and G3 are completed, the anti-parallel diode of the switching transistor G3 conducts; at this time, Therefore, i L1 decreases linearly until time t3.

[0056] At time t3 - t4, the dual-active-bridge DC converter is in operating mode 3: corresponding to Figure 12 , at time t3, the switching transistor G4 turns off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer excitation inductances charge and discharge the junction capacitances of the switching transistors G4 and G6 simultaneously; when the charging and discharging of the junction capacitances of the switching transistors G4 and G6 are completed, the anti-parallel diode of the switching transistor G6 conducts; at this time, Therefore, i L1 increases linearly until time t4.

[0057] At time t4 - t6, the dual-active-bridge DC converter is in operating mode 4: corresponding to Figure 13 , at time t4, the switching transistors S1 and S3 turn off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor charge and discharge the junction capacitances of the switching transistors S1 to S4; when the charging and discharging of the junction capacitances of the switching transistors S1 to S4 are completed, the anti-parallel diodes of the switching transistors S2 and S4 conduct; then, the currents of the two inductors L k1 and L k2 in the coupled inductor first decrease to zero in the positive direction and then increase in the reverse direction until time t6; at this time, Therefore, i L1 increases linearly.

[0058] At time t6 - t7, the dual-active-bridge DC converter is in operating mode 5: corresponding to Figure 14 , at time t6, the switching transistor G3 turns off; then, the currents of the two inductors L k1 and L k2 in the coupled inductor and the currents of the two transformer excitation inductances charge and discharge the junction capacitances of the switching transistors G1 and G3 simultaneously; when the charging and discharging of the junction capacitances of the switching transistors G1 and G3 are completed, the anti-parallel diode of the switching transistor G1 conducts, at this time, Therefore, i L1 increases linearly until time t7.

[0059] At time t7 - t8, the dual-active-bridge DC converter is in operating mode 6: corresponding to Figure 15 , at time t7, the switching transistor G6 turns off; then, the currents of the two inductors L k1 and Lk2 The current and the currents of the exciting inductances of the two transformers charge and discharge the junction capacitances of the switching transistors G4 and G6 simultaneously; when the charging and discharging of the junction capacitances of the switching transistors G4 and G6 are completed, the anti-parallel diode of the switching transistor G4 conducts; at this time, Therefore, i L1 decreases linearly until time t8.

[0060] The above is the working process of one switching cycle of the converter in Mode 2. From the above analysis, it can be seen that within one cycle, v L1 and v L2 , i L1 and i L2 are exactly the same. Therefore, only the waveforms of v L1 , i L1 are drawn in its working waveform diagram. The primary sides of the transformers T1 and T2 are equivalent to being connected in parallel across V1. This modulation method can control the amplitude of the voltage on the secondary side of the transformer to be V2. By adjusting the phase difference of the switching transistors, the transmitted power can be changed.

[0061] In this embodiment, a 1000W converter prototype was built under the conditions that the input voltage is 250V - 450V and the output voltage is 800V. MOSFETs are used as the switching devices in the two switching circuits. The driving signals of the main circuit are generated by the TI digital signal processor TMS320F280049, and then isolated and amplified by the driving circuit to provide driving voltages for the switching transistors of the main circuit. Under these experimental conditions, the dual-active-bridge DC converter with a six-switch reconfigurable network based on coupled inductors proposed by the present invention can operate normally in a closed loop under its modulation method. The converter prototype can operate normally under different input voltages and different loads.

[0062] The above are only the preferred embodiments of the present invention, and are not limitations on the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A dual active bridge DC converter based on a six-switch reconfigurable network with coupled inductors, characterized in that: The invention comprises a first port, a second port, two transformers, two inductors and two switch loops; one of the first port and the second port is selectively used as a power supply end, and the other port is correspondingly used as a load end; the first port is connected to a first filter capacitor C V1 A series circuit with a supporting capacitor is formed, and a second filter capacitor C is connected to the second port. V2 The first switch loop is composed of switch tubes S1~S4, the second switch loop is composed of switch tubes G1~G6, the supporting capacitor series circuit is composed of supporting capacitors C1~C4, the first switch loop and the supporting capacitor series circuit are connected through two transformers T1, T2 and two inductors L k1 , L k2 Connect the second switch loop, two inductors L k1 , L k2 is a coupled inductor.

2. The dual active bridge DC converter based on a six-switch reconfigurable network with coupled inductors according to claim 1, characterized in that: The first filter capacitor C V1 The two ends of are connected to the positive and negative electrodes of the first port respectively; the positive electrode of the first port is connected to the drain of the switch tube S1 and one end of the support capacitor C1 at the same time; the negative electrode of the first port is connected to the source of the switch tube S4 and one end of the support capacitor C4 at the same time; the source of the switch tube S1 is connected to the drain of the switch tube S2 and one end of the primary side of the transformer T1 at the same time; the other end of the primary side of the transformer T1 is connected to the inductor L k1 One end of the inductor L k1 The other end of the supporting capacitor C1 is connected to the other end of the supporting capacitor C1 and one end of the supporting capacitor C2; the other end of the supporting capacitor C2 is connected to one end of the supporting capacitor C3, the source of the switch tube S2 and the drain of the switch tube S3; the source of the switch tube S3 is connected to the drain of the switch tube S4 and the inductor L k2 One end of the inductor L k2 The other end of the transformer T2 is connected to one end of the primary side; the other end of the transformer T2 primary side is connected to the other end of the support capacitor C3 and the other end of the support capacitor C4; the second filter capacitor C V2 The two ends are respectively connected to the positive and negative electrodes of the second port; the positive electrode of the second port is simultaneously connected to the drain of the switch tube G1 and the drain of the switch tube G4; the negative electrode of the second port is simultaneously connected to the source of the switch tube G3 and the source of the switch tube G6; the source of the switch tube G1 is simultaneously connected to the drain of the switch tube G2 and one end of the secondary side of the transformer T1; the other end of the secondary side of the transformer T1 is simultaneously connected to the source of the switch tube G4 and the drain of the switch tube G5; the source of the switch tube G2 is simultaneously connected to the drain of the switch tube G3 and one end of the secondary side of the transformer T2; the other end of the secondary side of the transformer T2 is simultaneously connected to the source of the switch tube G5 and the drain of the switch tube G6.

3. The modulation method of the dual active bridge DC converter based on the six-switch reconfigurable network of coupled inductors according to claim 1 or 2, characterized in that: The dual active bridge DC converter has two working modes, corresponding to two modulation modes; the dual active bridge DC converter switches between the two working modes according to specific working conditions to expand the working area of ​​the dual active bridge DC converter.

4. The modulation method of the dual active bridge DC converter based on the six-switch reconfigurable network of coupled inductors according to claim 3 is characterized in that: When the dual active bridge DC converter operates in mode 1, it has 6 operating modes: At the moment t0-t2, the dual active bridge DC converter is in working mode 1: at the moment t0, the switches S2 and S3 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current is used to charge and discharge the junction capacitance of the switch tubes S1 to S4; when the junction capacitance of the switch tubes S1 to S4 is charged and discharged, the reverse parallel diodes of the switch tubes S1 and S4 are turned on; Then, the two inductors L in the coupled inductor k1 and L k2 The current first decreases in the reverse direction to zero, and then increases in the forward direction to time t2; at this time, the node a1 connected to the source of the switch tube S1, the drain of the switch tube S2 and one end of the primary side of the transformer T1 and one end of the support capacitor C2, the other end of the support capacitor C1 and the inductor L k1 The voltage between the nodes b1 connected together at the other end The voltage between the node c1 where the source of the switch tube G4, the drain of the switch tube G5 and the other end of the secondary side of the transformer T1 are connected and the node d1 where the source of the switch tube G1, the drain of the switch tube G2 and one end of the secondary side of the transformer T1 are connected is Therefore, the inductance L k1 The current i L1 Linear rise; At the moment t2-t3, the dual active bridge DC converter is in working mode 2: at the moment t2, the switch tubes G1 and G3 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G1 to G3; when the junction capacitance of the switch tubes G1 to G3 is charged and discharged, the reverse parallel diode of the switch tube G2 is turned on; at this time, Therefore L1 Decrease linearly until time t3; At time t3-t4, the dual active bridge DC converter is in working mode 3: at time t3, the switch tubes G4 and G6 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G4 to G6; when the junction capacitance of the switch tubes G4 to G6 is charged and discharged, the reverse parallel diode of the switch tube G5 is turned on; at this time, Therefore L1 It rises linearly until time t4; At time t4-t6, the dual active bridge DC converter is in working mode 4: at time t4, the switches S1 and S4 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current charges and discharges the junction capacitance of the switch tubes S1 to S4; when the junction capacitance of the switch tubes S1 to S4 is charged and discharged, the reverse parallel diodes of the switch tubes S2 and S3 are turned on; then, the two inductors L in the coupled inductor k1 and L k2 The current first decreases to zero in the forward direction, and then increases in the reverse direction to time t6; at this time, Therefore L1 Linear rise; At time t6-t7, the dual active bridge DC converter is in working mode 5: at time t6, the switch tube G2 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G1 to G3; when the junction capacitance of the switch tubes G1 to G3 is charged and discharged, the reverse parallel diodes of the switch tubes G1 and G3 are turned on. Therefore L1 It rises linearly until time t7; At time t7-t8, the dual active bridge DC converter is in working mode 6: at time t7, the switch tube G5 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G4 to G6; when the junction capacitance of the switch tubes G4 to G6 is charged and discharged, the reverse parallel diodes of the switch tubes G4 and G6 are turned on; at this time, Therefore L1 It decreases linearly until time t8.

5. The modulation method of the dual active bridge DC converter based on the six-switch reconfigurable network of coupled inductors according to claim 3 is characterized in that: When the dual active bridge DC converter works in mode 2, the switch tubes G2 and G5 are always at a high level to keep them in the on state. The dual active bridge DC converter has 6 working modes: At time t0-t2, the dual active bridge DC converter is in working mode 1: at time t0, the switches S2 and S4 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current charges and discharges the junction capacitance of the switch tubes S1 to S4; when the junction capacitance of the switch tubes S1 to S4 is charged and discharged, the reverse parallel diodes of the switch tubes S1 and S3 are turned on; then, the two inductors L in the coupled inductor k1 and L k2 The current first decreases in the reverse direction to zero, and then increases in the forward direction to the moment t2; at this time, Therefore L1 Linear rise; At time t2-t3, the dual active bridge DC converter is in working mode 2: at time t2, the switch tube G1 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G1 and G3; when the junction capacitance of the switch tubes G1 and G3 is charged and discharged, the reverse parallel diode of the switch tube G3 is turned on; at this time, Therefore L1 Decrease linearly until time t3; At time t3-t4, the dual active bridge DC converter is in working mode 3: at time t3, the switch tube G4 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G4 and G6; when the junction capacitance of the switch tubes G4 and G6 is charged and discharged, the reverse parallel diode of the switch tube G6 is turned on; at this time, Therefore L1 It rises linearly until time t4; At time t4-t6, the dual active bridge DC converter is in working mode 4: at time t4, the switches S1 and S3 are turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current charges and discharges the junction capacitance of the switch tubes S1 to S4; when the junction capacitance of the switch tubes S1 to S4 is charged and discharged, the reverse parallel diodes of the switch tubes S2 and S4 are turned on; then, the two inductors L in the coupled inductor k1 and L k2 The current first decreases to zero in the forward direction, and then increases in the reverse direction to time t6; at this time, Therefore L1 Linear rise; At time t6-t7, the dual active bridge DC converter is in working mode 5: at time t6, the switch tube G3 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G1 and G3; when the junction capacitance of the switch tubes G1 and G3 is charged and discharged, the reverse parallel diode of the switch tube G1 is turned on. Therefore L1 It rises linearly until time t7; At time t7-t8, the dual active bridge DC converter is in working mode 6: at time t7, the switch tube G6 is turned off; Then, the two inductors L in the coupled inductor k1 and L k2 The current of the two transformer excitation inductors simultaneously charges and discharges the junction capacitance of the switch tubes G4 and G6; when the junction capacitance of the switch tubes G4 and G6 is charged and discharged, the reverse parallel diode of the switch tube G4 is turned on; at this time, Therefore L1 It decreases linearly until time t8.

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