A resonant dual active bridge DC-DC converter and a control method thereof
By adding a freewheeling bridge arm and controlling its conduction time in a resonant dual active bridge DC-DC converter, the problem of high common-mode voltage noise is solved, EMC characteristics are improved, and the demand and cost of common-mode filters are reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WANBANG DIGITAL ENERGY CO LTD
- Filing Date
- 2022-12-08
- Publication Date
- 2026-06-26
Smart Images
Figure CN115940598B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of DC-DC converter technology, specifically to a resonant dual active bridge DC-DC converter and its control method. Background Technology
[0002] Figure 1 The diagram illustrates the structure of a resonant dual active bridge DC-DC converter (DAB) in the related art. This converter allows for bidirectional power transmission and mainly comprises two active full-bridge circuits, a resonant cavity, a DC blocking capacitor, and a high-frequency isolation transformer. The first active full-bridge circuit consists of switches Q1-Q4, and the second active full-bridge circuit consists of switches Q7-Q10. The resonant cavity includes a capacitor Cr and an inductor Lr. The DC blocking capacitor is capacitor Cb, and the high-frequency isolation transformer is transformer T1. Besides frequency modulation, this converter can increase the voltage gain adjustment range by controlling the inward phase shift angle between the individual bridge arms of the active full-bridge circuits. Furthermore, the power flow direction can be controlled by controlling the outward phase shift angle between the two active full-bridge circuits.
[0003] Taking forward power transmission as an example (i.e.) Figure 1 (The current flows from DC power supply V1 to DC power supply V2), such as Figure 2a As shown, when the required voltage gain is large, the phase shift between the two arms of the output active full bridge causes the midpoints H3 and H4 of the output arms to be "short-circuited" (either the upper half or the lower half of the two arms is conducting, such as...). Figure 2a (As shown in the shaded area), during this phase shift time, the DC power supply V1 magnetizes the resonant cavity inductor to store energy. During power transmission, the energy stored in the inductor is released to the output terminal, thereby enabling the converter to achieve boost characteristics and increase the output voltage gain; as shown in the shaded area... Figure 2b As shown, when the required gain is small, the phase shift between the two arms of the active full-bridge on the input side causes the midpoints H1 and H2 of the arms to be "short-circuited" (either the upper half or the lower half of the two arms is conducting, such as...). Figure 2b (As shown in the shaded area), the input voltage of the resonant cavity is zero during this phase shift time, which reduces the effective input voltage of the resonant cavity, thereby enabling the converter to obtain buck characteristics and reduce the output voltage gain.
[0004] By controlling this converter, the requirements for controlling power flow and adjusting voltage gain can be met, but if... Figure 2a and Figure 2bAs shown, during the commutation process of the upper and lower switching transistors in the primary and secondary bridge arms, the midpoint voltage of the bridge arm switches between its DC bus voltage and 0V in a two-level operating mode. The large voltage change rate dv / dt generates a large amount of common-mode voltage noise. Furthermore, the sum of the midpoint voltages of the bridge arms in the phase-shifting bridge undergoes abrupt changes during phase shifting, which is detrimental to the mutual cancellation of common-mode currents within the topology. Moreover, the operating frequency of current resonant dual active bridges is generally around 100kHz-200kHz. The multiples of their switching frequency harmonics fall within the frequency range of conducted interference testing, resulting in poor EMC characteristics for this resonant dual active bridge DC-DC converter. This necessitates a large common-mode filter for suppression and requires significant cost for EMC remediation. Summary of the Invention
[0005] To address the above-mentioned technical problems, this invention provides a resonant dual active bridge DC-DC converter and its control method, which effectively reduces the common-mode voltage noise generated during the operation of the dual active bridge DC-DC converter.
[0006] The technical solution adopted in this invention is as follows:
[0007] A resonant dual active bridge DC-DC converter includes a first active full-bridge, a second active full-bridge, a high-frequency isolation transformer, a resonant cavity, and a DC blocking capacitor, wherein...
[0008] The first active full bridge includes a first power bridge arm and a second power bridge arm. The two ends of the first power bridge arm and the two ends of the second power bridge arm are respectively connected to the two ends of the first DC bus. The midpoint of the first power bridge arm is connected to the first end of the first winding of the high-frequency isolation transformer through the resonant cavity. The second end of the first winding of the high-frequency isolation transformer is connected to the midpoint of the second power bridge arm. A first freewheeling bridge arm is also connected between the midpoint of the first power bridge arm and the midpoint of the second power bridge arm.
[0009] The second active full bridge includes a third power bridge arm and a fourth power bridge arm. The two ends of the third power bridge arm and the two ends of the fourth power bridge arm are respectively connected to the two ends of the second DC bus. The midpoint of the third power bridge arm is connected to the first end of the second winding of the high-frequency isolation transformer via the DC blocking capacitor. The second end of the second winding of the high-frequency isolation transformer is connected to the midpoint of the fourth power bridge arm. A second freewheeling bridge arm is also connected between the midpoint of the third power bridge arm and the midpoint of the fourth power bridge arm.
[0010] When the first freewheeling bridge arm / second freewheeling bridge arm is turned on during power conversion, the midpoint of the two corresponding power bridge arms is short-circuited.
[0011] Furthermore,
[0012] The first power bridge arm includes a first switching transistor and a second switching transistor. The drain of the first switching transistor is connected to the first end of the first DC bus, the source of the first switching transistor is connected to the drain of the second switching transistor, and the source of the second switching transistor is connected to the second end of the first DC bus.
[0013] The second power bridge arm includes a third switch and a fourth switch. The drain of the third switch is connected to the first end of the first DC bus, the source of the third switch is connected to the drain of the fourth switch, and the source of the fourth switch is connected to the second end of the first DC bus.
[0014] The third power bridge arm includes a seventh switch and an eighth switch. The drain of the seventh switch is connected to the first end of the second DC bus, the source of the seventh switch is connected to the drain of the eighth switch, and the source of the eighth switch is connected to the second end of the second DC bus.
[0015] The fourth power bridge arm includes a ninth switch and a tenth switch. The drain of the ninth switch is connected to the first end of the second DC bus, the source of the ninth switch is connected to the drain of the tenth switch, and the source of the tenth switch is connected to the second end of the second DC bus.
[0016] Furthermore, the resonant cavity includes a resonant capacitor and a resonant inductor. The first end of the resonant capacitor is connected to the midpoint of the first power bridge arm, the second end of the resonant capacitor is connected to the first end of the resonant inductor, and the second end of the resonant inductor is connected to the first end of the first winding of the high-frequency isolation transformer.
[0017] Furthermore, the resonant capacitor includes a single capacitor or is composed of multiple capacitors connected in series / parallel; the resonant inductor is an independent resonant inductor or is integrated on the high-frequency isolation transformer.
[0018] Furthermore,
[0019] The first freewheeling bridge arm includes a fifth switch and a sixth switch. The source of the fifth switch is connected to the midpoint of the first power bridge arm, the drain of the fifth switch is connected to the drain of the sixth switch, and the source of the sixth switch is connected to the midpoint of the second power bridge arm.
[0020] The second freewheeling bridge arm includes an eleventh switch and a twelfth switch. The source of the eleventh switch is connected to the midpoint of the third power bridge arm, the drain of the eleventh switch is connected to the drain of the twelfth switch, and the source of the twelfth switch is connected to the midpoint of the fourth power bridge arm.
[0021] Furthermore, the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth switches are all NMOS transistors.
[0022] Furthermore, a capacitor C1 is connected in parallel across the two ends of the first DC bus, and a capacitor C2 is connected in parallel across the two ends of the second DC bus.
[0023] In another aspect, the present invention provides a control method for a resonant dual active bridge DC-DC converter, the control method comprising the following steps:
[0024] Receive power transmission direction commands and voltage gain requirement commands;
[0025] When the power transmission direction is forward and the voltage gain requirement is greater than or equal to 1, the second freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge.
[0026] When the power transmission direction is forward and the voltage gain requirement is less than 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge.
[0027] When the power transmission direction is reverse and the voltage gain requirement is greater than or equal to 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge.
[0028] When the power transmission direction is reverse and the voltage gain requirement is less than 1, the second freewheeling bridge arm operates and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge.
[0029] Furthermore, the control method further includes the following steps:
[0030] The second freewheeling bridge arm works in conjunction with the second active full-bridge. Specifically, during the first time period of the working cycle, the seventh and tenth switches are off while the eighth and ninth switches are on, the eleventh switch is off, and the twelfth switch is on; during the second time period, the seventh, eighth, ninth, and tenth switches are off, and the eleventh and twelfth switches are on; during the third time period, the seventh and tenth switches are on while the eighth and ninth switches are off, the eleventh switch is on, and the twelfth switch is off; during the fourth time period, the seventh, eighth, ninth, and tenth switches are off, and the eleventh and twelfth switches are on; the voltage gain range is adjusted by controlling the on-time of the eleventh and twelfth switches.
[0031] The first freewheeling bridge arm works in conjunction with the first active full-bridge. Specifically, during the first time period of the working cycle, the first and fourth switches are off while the second and third switches are on, the fifth switch is off, and the sixth switch is on; during the second time period, the first, second, third, and fourth switches are off, and the fifth and sixth switches are on; during the third time period, the first and fourth switches are on while the second and third switches are off, the fifth switch is on, and the sixth switch is off; during the fourth time period, the first, second, third, and fourth switches are off, and the fifth and sixth switches are on; the voltage gain range is adjusted by controlling the on-time of the fifth and sixth switches.
[0032] The beneficial effects of the present invention are as follows: The resonant dual active bridge DC-DC converter provided by the present invention increases the voltage gain adjustment range of the converter by adding a first freewheeling arm between the midpoints of the first power bridge arm and the second power bridge arm, and adding a second freewheeling arm between the midpoints of the third power bridge arm and the fourth power bridge arm, so that when the power flows in the forward or reverse direction, the conduction time and operating sequence of the first freewheeling arm and the second freewheeling arm can be controlled, and the common-mode voltage noise can be effectively reduced, thereby improving the EMC characteristics of the converter. Attached Figure Description
[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 This is a schematic diagram of the structure of a resonant dual active bridge DC-DC converter in related technologies.
[0035] Figure 2a for Figure 1 The diagram shows the operating waveforms of the converter when power is transmitted in the forward direction and a large voltage gain is required.
[0036] Figure 2b for Figure 1 The diagram shows the operating waveforms of the converter when power is transmitted in the forward direction and the required voltage gain is relatively small.
[0037] Figure 3 This is a schematic diagram of the resonant dual active bridge DC-DC converter of the present invention.
[0038] Figure 4 This is a schematic diagram of the working waveforms of the converter of the present invention when power is transmitted in the forward direction and a large voltage gain is required. From top to bottom, the waveforms are: voltage VH1 at the midpoint H1 of the bridge arm, voltage VH2 at the midpoint H2 of the bridge arm, voltage VH3 at the midpoint H3 of the bridge arm, voltage VH4 at the midpoint H4 of the bridge arm, Vgs of the eleventh switch Q11, Vgs of the twelfth switch Q12, the waveform of the resonant cavity current iLr, and the waveform of half the sum of the voltages at the midpoints H3 and H4 of the bridge arm (VH3+VH4) / 2.
[0039] Figure 5a This is a schematic diagram of the converter of the present invention operating in mode a;
[0040] Figure 5b This is a schematic diagram of the converter of the present invention in mode b;
[0041] Figure 5c This is a schematic diagram of the converter of the present invention operating in mode c;
[0042] Figure 5d This is a schematic diagram of the converter of the present invention in mode d.
[0043] Figure 5e This is a schematic diagram of the converter of the present invention operating in mode e;
[0044] Figure 5f This is a schematic diagram of the converter of the present invention in mode f;
[0045] Figure 6 This is a schematic diagram of the working waveforms of the converter of the present invention when the power is transmitted in the forward direction and the required voltage gain is small. From top to bottom, the waveforms are: voltage VH1 at the midpoint H1 of the bridge arm, voltage VH2 at the midpoint H2 of the bridge arm, voltage VH3 at the midpoint H3 of the bridge arm, voltage VH4 at the midpoint H4 of the bridge arm, Vgs of the fifth switch Q5, Vgs of the sixth switch Q6, the waveform of the resonant cavity current iLr, and the waveform of half the sum of the voltages at the midpoints H1 and H2 of the bridge arms (VH1+VH2) / 2.
[0046] Figure 7a This is a schematic diagram of the converter of the present invention in mode a'.
[0047] Figure 7b This is a schematic diagram of the converter of the present invention operating in mode b';
[0048] Figure 7c This is a schematic diagram of the converter of the present invention operating in mode c';
[0049] Figure 7dThis is a schematic diagram of the converter of the present invention in mode d'.
[0050] Figure 7e This is a schematic diagram of the converter of the present invention operating in mode e';
[0051] Figure 7f This is a schematic diagram of the converter of the present invention in mode f'. Detailed Implementation
[0052] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0053] like Figure 3 As shown, this invention provides a resonant dual active bridge DC-DC converter, including a first active full-bridge, a second active full-bridge, a high-frequency isolation transformer, a resonant cavity, and a DC blocking capacitor, wherein...
[0054] The first active full-bridge includes a first power bridge arm and a second power bridge arm. A first freewheeling bridge arm is connected between the midpoint of the first power bridge arm and the midpoint of the second power bridge arm. Specifically, the first end of the first power bridge arm and the first end of the second power bridge arm are connected to the first end of the first DC bus V1. The second end of the first power bridge arm and the second end of the second power bridge arm are connected to the second end of the first DC bus V1. The first end of the first freewheeling bridge arm is connected to the midpoint H1 of the first power bridge arm, and the second end of the first freewheeling bridge arm is connected to the midpoint H2 of the second power bridge arm.
[0055] The second active full-bridge includes a third power bridge arm and a fourth power bridge arm. A second freewheeling bridge arm is connected between the midpoint of the third power bridge arm and the midpoint of the fourth power bridge arm. Specifically, the first end of the third power bridge arm and the first end of the fourth power bridge arm are connected to the first end of the second DC bus V2. The second end of the third power bridge arm and the second end of the fourth power bridge arm are connected to the second end of the second DC bus V2. The first end of the second freewheeling bridge arm is connected to the midpoint H3 of the third power bridge arm, and the second end of the second freewheeling bridge arm is connected to the midpoint H4 of the fourth power bridge arm.
[0056] Furthermore, the high-frequency isolation transformer includes a first winding N1 and a second winding N2. The first end of the first winding N1 is connected to the second end of the resonant cavity, and the first end of the resonant cavity is connected to the midpoint H1 of the first power bridge arm. The second end of the first winding N1 is connected to the midpoint H2 of the second power bridge arm. The first end of the second winding N2 is connected to the first end of the DC blocking capacitor, the second end of the DC blocking capacitor is connected to the midpoint H3 of the third power bridge arm, and the second end of the second winding N2 is connected to the midpoint H4 of the fourth power bridge arm.
[0057] Furthermore, the first power bridge arm includes a first switch Q1 and a second switch Q2. The drain of the first switch Q1 is connected to the first end of the first DC bus V1, the source of the first switch Q1 is connected to the drain of the second switch Q2, and the source of the second switch Q2 is connected to the second end of the first DC bus V1.
[0058] The second power bridge arm includes a third switch Q3 and a fourth switch Q4. The drain of the third switch Q3 is connected to the first end of the first DC bus V1, the source of the third switch Q3 is connected to the drain of the fourth switch Q4, and the source of the fourth switch Q4 is connected to the second end of the first DC bus V1.
[0059] The third power bridge arm includes a seventh switch Q7 and an eighth switch Q8. The drain of the seventh switch Q7 is connected to the first end of the second DC bus V2, and the source of the seventh switch Q7 is connected to the drain of the eighth switch Q8. The source of the eighth switch Q8 is connected to the second end of the second DC bus V2.
[0060] The fourth power bridge arm includes a ninth switch Q9 and a tenth switch Q10. The drain of the ninth switch Q9 is connected to the first end of the second DC bus V2, the source of the ninth switch Q9 is connected to the drain of the tenth switch Q10, and the source of the tenth switch Q10 is connected to the second end of the second DC bus V2.
[0061] Furthermore, the first freewheeling bridge arm includes a fifth switch Q5 and a sixth switch Q6. The source of the fifth switch Q5 is connected to the midpoint H1 of the first power bridge arm, the drain of the fifth switch Q5 is connected to the drain of the sixth switch Q6, and the source of the sixth switch Q6 is connected to the midpoint H2 of the second power bridge arm.
[0062] The second freewheeling bridge arm includes an eleventh switch Q11 and a twelfth switch Q12. The source of the eleventh switch Q11 is connected to the midpoint H3 of the third power bridge arm, the drain of the eleventh switch Q11 is connected to the drain of the twelfth switch Q12, and the source of the twelfth switch Q12 is connected to the midpoint H4 of the fourth power bridge arm.
[0063] It should be noted that in this embodiment, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, the tenth switch Q10, the eleventh switch Q11, and the twelfth switch Q12 are all NMOS transistors. Of course, other power devices can be used in other embodiments to achieve the function of the present invention, which will not be described in detail here.
[0064] Furthermore, the resonant cavity includes a resonant capacitor and a resonant inductor. The first end of the resonant capacitor is connected to the midpoint H1 of the first power bridge arm, and the second end of the resonant capacitor is connected to the first end of the resonant inductor. The second end of the resonant inductor is connected to the first end of the first winding N1 of the high-frequency isolation transformer. In this embodiment, the resonant capacitor includes a single capacitor Cr, or it may be composed of multiple capacitors connected in series / parallel. The resonant inductor is an independent resonant inductor Lr, or it may be integrated with the high-frequency isolation transformer; this embodiment does not impose any limitations on this. In addition, in other embodiments, a resonant inductor may also be provided at the rear end of the second winding N2 to form a symmetrical structure on both sides.
[0065] Furthermore, a capacitor C1 is connected in parallel across the two ends of the first DC bus V1, and a capacitor C2 is connected in parallel across the two ends of the second DC bus V2, in order to output a smooth voltage.
[0066] Thus, in this embodiment, the resonant dual active bridge DC-DC converter can increase the voltage gain adjustment range by controlling the conduction time and operating timing of the first freewheeling bridge arm / second freewheeling bridge arm during power conversion. Specifically, and Figure 1 Compared to the converter shown, the first freewheeling bridge arm is controlled to short-circuit the midpoints H1 and H2 of the bridge arm. When short-circuited, the voltage at the midpoint of each bridge arm is half the voltage of the first DC bus V1, so that the voltage change of the midpoints H1 and H2 of the bridge arm changes from two levels of V1 and 0V to three levels of V1, V1 / 2 and 0V. The second freewheeling bridge arm is controlled to short-circuit the midpoints H3 and H4 of the bridge arm. When short-circuited, the voltage at the midpoint of each bridge arm is half the voltage of the second DC bus V2, so that the voltage change of the midpoints H3 and H4 of the bridge arm changes from two levels of V2 and 0V to three levels of V2, V2 / 2 and 0V. This effectively reduces the voltage change rate dv / dt at the midpoint of each bridge arm. Furthermore, during power conversion, the sum of the voltages at the midpoints of the bridge arms of each active full-bridge is a fixed level. For example, the sum of the voltages at the midpoints H1 and H2 of the first active full-bridge is fixed at V1, and the sum of the voltages at the midpoints H3 and H4 of the second active full-bridge is fixed at V2. This provides an effective return path for common-mode noise, effectively reduces common-mode voltage noise, and improves the EMC characteristics of the converter.
[0067] This embodiment also provides a control method for the above-mentioned resonant dual active bridge DC-DC converter, which includes the following steps:
[0068] Receive power transmission direction commands and voltage gain requirement commands;
[0069] The controller sends drive signals to the first to twelfth switches based on the received power transmission direction command and voltage gain demand command to perform power transmission and conversion. Specifically,
[0070] When the power transmission direction is forward and the voltage gain requirement is greater than or equal to 1, the second freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge; the voltage gain requirement here does not include the amplification factor of the high-frequency isolation transformer, that is, the voltage gain requirement here is greater than or equal to 1, i.e., k×V2≥V1, where k is the transformer turns ratio: k=N1 / N2.
[0071] When the power transmission direction is forward and the voltage gain requirement is less than 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge; here the voltage gain requirement does not include the amplification factor of the high-frequency isolation transformer, that is, the voltage gain requirement here is less than 1, i.e., k×V2<V1, where k is the transformer turns ratio: k=N1 / N2.
[0072] When the power transmission direction is reverse and the voltage gain requirement is greater than or equal to 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge; here the voltage gain requirement does not include the amplification factor of the high-frequency isolation transformer, that is, the voltage gain requirement here is greater than or equal to 1, i.e., V1≥k×V2, where k is the transformer turns ratio: k=N1 / N2.
[0073] When the power transmission direction is reverse and the voltage gain requirement is less than 1, the second freewheeling bridge arm works and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge. Here, the voltage gain requirement does not include the amplification factor of the high-frequency isolation transformer, that is, the voltage gain requirement here is less than 1, i.e., V1 < k × V2, where k is the transformer turns ratio: k = N1 / N2.
[0074] Furthermore, the control method also includes the following steps:
[0075] When the second freewheeling bridge arm is working, it works in conjunction with the second active full-bridge circuit. Specifically, during the first time period of the working cycle, the seventh switch Q7 and the tenth switch Q10 are turned off, while the eighth switch Q8 and the ninth switch Q9 are turned on. The eleventh switch Q11 is turned off, and the twelfth switch Q12 is turned on. During the second time period, the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q10 are turned off, while the eleventh switch Q11 and the twelfth switch Q12 are turned on. The eleventh switch Q11 can be soft-turned on. In the third time period, the seventh switch Q7 and the tenth switch Q10 are turned on, while the eighth switch Q8 and the ninth switch Q9 are turned off. The eleventh switch Q11 is turned on, and the twelfth switch Q12 is turned off. In the fourth time period, the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q10 are turned off, while the eleventh switch Q11 and the twelfth switch Q12 are turned on, and the twelfth switch Q12 can be soft-turned on. The voltage gain range can be adjusted by controlling the on-time of the eleventh switch Q11 and the twelfth switch Q12.
[0076] When the first freewheeling bridge arm is working, it works in conjunction with the first active full-bridge circuit. Specifically, during the first time period of the working cycle, the first switch Q1 and the fourth switch Q4 are off, while the second switch Q2 and the third switch Q3 are on. The fifth switch Q5 is off, and the sixth switch Q6 is on. During the second time period, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 are off, while the fifth switch Q5 and the sixth switch Q6 are on. Furthermore, the fifth switch Q5 can achieve soft... In the first time period, the first switch Q1 and the fourth switch Q4 are turned on, while the second switch Q2 and the third switch Q3 are turned off, the fifth switch Q5 is turned on, and the sixth switch Q6 is turned off. In the second time period, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 are turned off, while the fifth switch Q5 and the sixth switch Q6 are turned on, and the sixth switch Q6 can be soft-turned on. The voltage gain range can be adjusted by controlling the on-time of the fifth switch Q5 and the sixth switch Q6.
[0077] The following section uses two operating conditions—voltage gain requirement greater than or equal to 1 and less than 1—when power is transmitted in the forward direction (from the first DC bus V1 to the second DC bus V2) as examples to explain the specific working process and principle in detail. For the sake of simplicity, dead time is not considered.
[0078] When k×V2≥V1, the second freewheeling bridge arm is active, while the first freewheeling bridge arm is inactive. The specific operation details are as follows: Figure 4 and Figures 5a-5f As shown, a single cycle includes six modes:
[0079] Mode a(t0-t1): At time t0, the second switch Q2 and the third switch Q3 are turned off. Since the resonant cavity current does not change abruptly, it naturally switches to the freewheeling current of the body diodes of the first switch Q1 and the fourth switch Q4, achieving soft turn-on for the first switch Q1 and the fourth switch Q4. The seventh switch Q7 and the tenth switch Q10 are turned off, while the eighth switch Q8 and the ninth switch Q9 are turned on. The secondary current is rectified and output to the second DC bus V2 through the eighth switch Q8 and the ninth switch Q9. At this time, the eleventh switch Q11 is turned off, and the twelfth switch Q12 is turned on. See also... Figure 5a As shown.
[0080] Mode b(t1-t2): At time t1, the resonant cavity current drops to zero and begins to increase in the reverse direction. At this time, the secondary current also reverses, naturally switching to freewheeling through the eleventh switch Q11 and the twelfth switch Q12, short-circuiting the secondary output; the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q10 are all turned off; the first DC bus V1 magnetizes the resonant inductor and stores energy through the first switch Q1 and the fourth switch Q4, while the second switch Q2 and the third switch Q3 remain off; see also Figure 5b As shown. In this operating mode, due to the conduction of the second freewheeling bridge arm, the voltage at the midpoint H3 of the third power bridge arm rises from zero to V2 / 2, and the voltage at the midpoint H4 of the fourth power bridge arm drops from V2 to V2 / 2.
[0081] Mode c(t2-t3): At time t2, the twelfth switch Q12 is off, the eleventh switch Q11 is on, and the secondary current naturally switches to the seventh switch Q7 and the tenth switch Q10, while the eighth switch Q8 and the ninth switch Q9 are off; the first switch Q1 and the fourth switch Q4 remain on, and the second switch Q2 and the third switch Q3 remain off. The input energy of the first DC bus V1 and the energy stored in the resonant cavity in operating mode b are transferred to the second DC bus V2; see also Figure 5c As shown. In this operating mode, the voltage at the midpoint H3 of the third power bridge arm rises from V2 / 2 to V2, while the voltage at the midpoint of the fourth power bridge arm drops from V2 / 2 to zero.
[0082] Mode d(t3-t4): At time t3, the first switch Q1 and the fourth switch Q4 are turned off, the resonant cavity current remains unchanged, and the resonant cavity current naturally switches to the freewheeling current of the body diodes of the second switch Q2 and the third switch Q3. The second switch Q2 and the third switch Q3 achieve soft turn-on, and the resonant cavity current quickly drops to zero. This part of the resonant cavity energy is released to the secondary side and continues to be rectified and transmitted to the second DC bus V2 by the seventh switch Q7 and the tenth switch Q10. At this time, the eighth switch Q8 and the ninth switch Q9 remain off, the eleventh switch Q11 remains on, and the twelfth switch Q12 remains off; see also Figure 5d As shown.
[0083] Mode e(t4-t5): At time t4, the resonant cavity current drops to zero and then increases in the reverse direction. At this time, the secondary current also reverses direction, naturally switching to freewheeling via the eleventh switch Q11 and the twelfth switch Q12, short-circuiting the secondary output; the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q10 are all turned off; the first DC bus V1 magnetizes the resonant cavity in the reverse direction and stores energy through the second switch Q2 and the third switch Q3, while the first switch Q1 and the fourth switch Q4 remain off; see also... Figure 5e As shown. In this operating mode, due to the conduction of the second freewheeling bridge arm, the voltage at the midpoint H3 of the third power bridge arm decreases from V2 to V2 / 2, and the voltage at the midpoint H4 of the fourth power bridge arm rises from zero to V2 / 2.
[0084] Mode f(t5-t6): At time t5, the eleventh switch Q11 is turned off, the twelfth switch Q12 is turned on, and the secondary current naturally switches to the eighth switch Q8 and the ninth switch Q9, while the seventh switch Q7 and the tenth switch Q10 remain off; the first switch Q1 and the fourth switch Q4 are turned off, and the second switch Q2 and the third switch Q3 are turned on. The input energy of the first DC bus V1 and the energy stored in the resonant cavity in operating mode e are transferred to the second DC bus V2; see also Figure 5f As shown. In this operating mode, the voltage at the midpoint H3 of the third power bridge arm decreases from V2 / 2 to zero, while the voltage at the midpoint H4 of the fourth power bridge arm increases from V2 / 2 to V2.
[0085] The above operating timing is the entire operating process of the converter in one switching cycle under the condition of forward power transmission and k×V2≥V1.
[0086] When k×V2<V1, the first freewheeling bridge arm is working, and the second freewheeling bridge arm is not working. The specific working process is as follows: Figure 6 and Figures 7a-7f As shown, a single cycle includes six modes:
[0087] Mode a'(t0'-t1'): At time t0', the fifth switch Q5 is turned off, and the sixth switch Q6 is turned on. Since the resonant cavity current cannot change abruptly, the resonant cavity current freewheels through the body diodes of the second switch Q2 and the third switch Q3. The second switch Q2 and the third switch Q3 achieve soft turn-on, while the first switch Q1 and the fourth switch Q4 are turned off. The energy of the inductor in the resonant cavity continues to be transferred to the secondary side, and is rectified and output to the second DC bus V2 by the seventh switch Q7 and the tenth switch Q10. The eighth switch Q8 and the ninth switch Q9 are turned off. See also... Figure 7a As shown. In this operating mode, the voltage at the midpoint H1 of the first power bridge arm drops from V1 / 2 to zero, while the voltage at the midpoint H2 of the second power bridge arm rises from V1 / 2 to V1.
[0088] Mode b'(t1'-t2'): At time t1', the resonant cavity current decreases to zero and then increases in the opposite direction, and the secondary current also reverses. The first switch Q1 and the fourth switch Q4 are turned off, while the second switch Q2 and the third switch Q3 are turned on. The input energy of the first DC bus V1 is rectified and transmitted to the second DC bus V2 through the eighth switch Q8 and the ninth switch Q9. The seventh switch Q7 and the tenth switch Q10 are turned off. At this time, the fifth switch Q5 is turned off, and the sixth switch Q6 is turned on. See also... Figure 7b As shown.
[0089] Mode c'(t2'-t3'): At time t2', the second switch Q2 and the third switch Q3 are turned off, while the first switch Q1 and the fourth switch Q4 remain off; the resonant cavity current naturally switches to the fifth switch Q5 and the sixth switch Q6 for freewheeling; the input voltage to the resonant cavity is zero, the resonant cavity current decreases rapidly, and the released energy continues to be rectified and transferred to the second DC bus V2 by the eighth switch Q8 and the ninth switch Q9, while the seventh switch Q7 and the tenth switch Q10 remain off; see also Figure 7c As shown. In this operating mode, the effective input voltage of the resonant cavity is reduced, thereby reducing the voltage gain. Moreover, the voltage at the midpoint H1 of the first power bridge arm rises from zero to V1 / 2, and the voltage at the midpoint H2 of the second power bridge arm decreases from V1 to V1 / 2.
[0090] Mode d'(t3'-t4'): At time t3', the sixth switch Q6 is turned off, and the fifth switch Q5 is turned on. The resonant cavity current does not change abruptly and naturally switches to the freewheeling current of the body diodes of the first switch Q1 and the fourth switch Q4. The first switch Q1 and the fourth switch Q4 achieve soft turn-on, and the second switch Q2 and the third switch Q3 are turned off. The remaining energy of the resonant cavity continues to be rectified and output to the second DC bus V2 through the eighth switch Q8 and the ninth switch Q9. The seventh switch Q7 and the tenth switch Q10 are turned off. See also Figure 7dAs shown. In this operating mode, the voltage at the midpoint H1 of the first power bridge arm rises from V1 / 2 to V1, and the voltage at the midpoint H2 of the second power bridge arm drops from V1 / 2 to zero.
[0091] Mode e'(t4'-t5'): At time t4', the resonant cavity current drops to zero and then increases in the reverse direction. The secondary current commutates accordingly, switching from the eighth switch Q8 and the ninth switch Q9 to the seventh switch Q7 and the tenth switch Q10. The circuit enters resonant operation. The power input to the first DC bus V1 is rectified and transmitted to the second DC bus V2 by the seventh switch Q7 and the tenth switch Q10. At this time, the first switch Q1 and the fourth switch Q4 are turned on, the second switch Q2 and the third switch Q3 are turned off, the fifth switch Q5 is turned on, and the sixth switch Q6 is turned off. See also... Figure 7e As shown.
[0092] Mode f'(t5'-t6'): At time t5', the first switch Q1 and the fourth switch Q4 are turned off, while the second switch Q2 and the third switch Q3 remain off. The direction of the resonant cavity current remains unchanged, and the resonant cavity current naturally switches to the fifth switch Q5 and the sixth switch Q6 for freewheeling. The input voltage of the resonant cavity is zero, and the resonant cavity current decreases rapidly. The energy released by the resonant cavity continues to be rectified and transferred to the second DC bus V2 by the seventh switch Q7 and the tenth switch Q10. The eighth switch Q8 and the ninth switch Q9 are turned off. See also... Figure 7f As shown. In this operating mode, the effective input voltage of the resonant cavity is reduced, thereby reducing the voltage gain. The voltage at the midpoint H1 of the first power bridge arm decreases from V1 to V1 / 2, and the voltage at the midpoint H2 of the second bridge arm increases from zero to V1 / 2.
[0093] The above operating sequence is the entire operating process of the converter in one switching cycle under the condition of forward power transmission and k×V2<V1.
[0094] In the reverse power transmission mode (flowing from the second DC bus V2 to the first DC bus V1), the operating timing of each bridge arm is similar to that in the forward power transmission mode, except that the outward phase shift angle between the first active full bridge and the second active full bridge is different. For details, please refer to the above embodiment, which will not be repeated here.
[0095] In summary, the resonant dual active bridge DC-DC converter provided in this embodiment can increase the voltage gain adjustment range of the converter and effectively reduce common-mode voltage noise by controlling the conduction time and operating sequence of the first freewheeling bridge arm and the second freewheeling bridge arm when power flows in the forward or reverse direction.
[0096] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.
[0097] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0098] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A resonant dual active bridge DC-DC converter, characterized in that, It includes a first active full-bridge, a second active full-bridge, a high-frequency isolation transformer, a resonant cavity, and a DC blocking capacitor, among which, The first active full bridge includes a first power bridge arm and a second power bridge arm. The two ends of the first power bridge arm and the two ends of the second power bridge arm are respectively connected to the two ends of the first DC bus. The midpoint of the first power bridge arm is connected to the first end of the first winding of the high-frequency isolation transformer through the resonant cavity. The second end of the first winding of the high-frequency isolation transformer is connected to the midpoint of the second power bridge arm. A first freewheeling bridge arm is also connected between the midpoint of the first power bridge arm and the midpoint of the second power bridge arm. The second active full bridge includes a third power bridge arm and a fourth power bridge arm. The two ends of the third power bridge arm and the two ends of the fourth power bridge arm are respectively connected to the two ends of the second DC bus. The midpoint of the third power bridge arm is connected to the first end of the second winding of the high-frequency isolation transformer via the DC blocking capacitor. The second end of the second winding of the high-frequency isolation transformer is connected to the midpoint of the fourth power bridge arm. A second freewheeling bridge arm is also connected between the midpoint of the third power bridge arm and the midpoint of the fourth power bridge arm. When the first freewheeling bridge arm / second freewheeling bridge arm is turned on during power conversion, the midpoint of the two corresponding power bridge arms is short-circuited. The first freewheeling bridge arm includes a fifth switch and a sixth switch. The source of the fifth switch is connected to the midpoint of the first power bridge arm, the drain of the fifth switch is connected to the drain of the sixth switch, and the source of the sixth switch is connected to the midpoint of the second power bridge arm. The second freewheeling bridge arm includes an eleventh switch and a twelfth switch. The source of the eleventh switch is connected to the midpoint of the third power bridge arm, the drain of the eleventh switch is connected to the drain of the twelfth switch, and the source of the twelfth switch is connected to the midpoint of the fourth power bridge arm. The first power bridge arm includes a first switching transistor and a second switching transistor. The drain of the first switching transistor is connected to the first end of the first DC bus, the source of the first switching transistor is connected to the drain of the second switching transistor, and the source of the second switching transistor is connected to the second end of the first DC bus. The second power bridge arm includes a third switch and a fourth switch. The drain of the third switch is connected to the first end of the first DC bus, the source of the third switch is connected to the drain of the fourth switch, and the source of the fourth switch is connected to the second end of the first DC bus. The third power bridge arm includes a seventh switch and an eighth switch. The drain of the seventh switch is connected to the first end of the second DC bus, the source of the seventh switch is connected to the drain of the eighth switch, and the source of the eighth switch is connected to the second end of the second DC bus. The fourth power bridge arm includes a ninth switch and a tenth switch. The drain of the ninth switch is connected to the first end of the second DC bus, the source of the ninth switch is connected to the drain of the tenth switch, and the source of the tenth switch is connected to the second end of the second DC bus.
2. The resonant dual active bridge DC-DC converter according to claim 1, characterized in that, The resonant cavity includes a resonant capacitor and a resonant inductor. The first end of the resonant capacitor is connected to the midpoint of the first power bridge arm, and the second end of the resonant capacitor is connected to the first end of the resonant inductor. The second end of the resonant inductor is connected to the first end of the first winding of the high-frequency isolation transformer.
3. The resonant dual active bridge DC-DC converter according to claim 2, characterized in that, The resonant capacitor may be a single capacitor or a combination of multiple capacitors connected in series or parallel; the resonant inductor may be an independent resonant inductor or integrated onto the high-frequency isolation transformer.
4. The resonant dual active bridge DC-DC converter according to claim 1, characterized in that, The first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh and twelfth switches are all NMOS transistors.
5. The resonant dual active bridge DC-DC converter according to claim 4, characterized in that, A capacitor C1 is connected in parallel across the two ends of the first DC bus, and a capacitor C2 is connected in parallel across the two ends of the second DC bus.
6. A control method for a resonant dual active bridge DC-DC converter, characterized in that, The control method is implemented by the resonant dual active bridge DC-DC converter according to any one of claims 1 to 5, and the control method includes the following steps: Receive power transmission direction commands and voltage gain requirement commands; When the power transmission direction is forward and the voltage gain requirement is greater than or equal to 1, the second freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge. When the power transmission direction is forward and the voltage gain requirement is less than 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge leads the drive signal of the second active full bridge. When the power transmission direction is reverse and the voltage gain requirement is greater than or equal to 1, the first freewheeling bridge arm works and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge. When the power transmission direction is reverse and the voltage gain requirement is less than 1, the second freewheeling bridge arm operates and the drive signal of the first active full bridge lags behind the drive signal of the second active full bridge.
7. The control method according to claim 6, characterized in that, The control method further includes the following steps: The second freewheeling bridge arm works in conjunction with the second active full-bridge. Specifically, during the first time period of the working cycle, the seventh and tenth switches are off while the eighth and ninth switches are on, the eleventh switch is off, and the twelfth switch is on; during the second time period, the seventh, eighth, ninth, and tenth switches are off, and the eleventh and twelfth switches are on; during the third time period, the seventh and tenth switches are on while the eighth and ninth switches are off, the eleventh switch is on, and the twelfth switch is off; during the fourth time period, the seventh, eighth, ninth, and tenth switches are off, and the eleventh and twelfth switches are on; the voltage gain range is adjusted by controlling the on-time of the eleventh and twelfth switches. The first freewheeling bridge arm works in conjunction with the first active full-bridge. Specifically, during the first time period of the working cycle, the first and fourth switches are off while the second and third switches are on, the fifth switch is off, and the sixth switch is on; during the second time period, the first, second, third, and fourth switches are off, and the fifth and sixth switches are on; during the third time period, the first and fourth switches are on while the second and third switches are off, the fifth switch is on, and the sixth switch is off; during the fourth time period, the first, second, third, and fourth switches are off, and the fifth and sixth switches are on; the voltage gain range is adjusted by controlling the on-time of the fifth and sixth switches.