阅读说明：本技术 Cllc双向直流-直流变换器以及控制方法 (C LL C bidirectional DC-DC converter and control method ) 是由 蒋劲松 郑剑锋 汪易强 庄启超 郭水保 于 2020-04-13 设计创作，主要内容包括：本发明实施例公开了一种CLLC双向直流-直流变换器以及控制方法,属于电力电子技术领域。其中所述CLLC双向直流-直流变换器包括：依序连接的原边滤波电容(C1)、原边桥(10)、原边谐振器件(11)、变压装置(12)、副边谐振器件(13)、副边桥(14)以及副边滤波电容(C8),原边桥包括三个原边半桥；原边谐振器件包括三组原边串联谐振器件；变压装置与原边谐振器件和副边谐振器件相连；副边谐振器件包括三组,每一组副边谐振器件包括一个谐振电容,每个谐振电容的一端与一个变压器的一个副边端子相连接,另一端与副边桥中的一个副边半桥相连；副边桥包括三个副边半桥。本发明在硬件上自带均流能力,不需要额外的均流控制电路,极大地降低了成本。(The embodiment of the invention discloses a C LL C bidirectional direct current-direct current converter and a control method, and belongs to the technical field of power electronics, wherein the C LL C bidirectional direct current-direct current converter comprises a primary side filter capacitor (C1), a primary side bridge (10), a primary side resonant device (11), a voltage transformation device (12), a secondary side resonant device (13), a secondary side bridge (14) and a secondary side filter capacitor (C8) which are sequentially connected, the primary side bridge comprises three primary side half bridges, the primary side resonant device comprises three groups of primary side series resonant devices, the voltage transformation device is connected with the primary side resonant device and the secondary side resonant device, the secondary side resonant device comprises three groups, each group of secondary side resonant device comprises one resonant capacitor, one end of each resonant capacitor is connected with one secondary side terminal of one transformer, the other end of each capacitor is connected with one secondary side half bridge of the secondary side bridge, the secondary side bridge comprises three secondary side half bridges, and the current sharing control circuit is not needed on hardware, and the cost is greatly reduced.)

1. A C LL C bidirectional DC-DC converter is characterized by comprising a primary side filter capacitor (C1), a primary side bridge (10), a primary side resonance device (11), a transformation device (12), a secondary side resonance device (13), a secondary side bridge (14) and a secondary side filter capacitor (C8) which are connected in sequence, wherein,

the primary side bridge (10) comprises three primary side half bridges, each primary side half bridge is formed by connecting two switching tubes in series, and each primary side half bridge is connected with a primary side filter capacitor (C1);

the primary side resonance device (11) comprises three groups of primary side series resonance devices, and each group of primary side series resonance devices is connected with one primary side half bridge;

the transformer device (12) is connected with the primary side resonance device (11) and the secondary side resonance device (13);

the secondary side resonance devices (13) comprise three groups, each group of secondary side resonance devices comprises a resonance capacitor, one end of each resonance capacitor is connected with one secondary side terminal of one transformer, and the other end of each resonance capacitor is connected with one secondary side half bridge in the secondary side bridge;

the secondary side bridge (14) comprises three secondary side half bridges, each secondary side half bridge is formed by connecting two switching tubes in series, and each secondary side half bridge is connected with a secondary side filter capacitor (C8).

2. The C LL C bidirectional dc-dc converter according to claim 1, wherein the primary side bridge (10) includes first to sixth switching tubes (S1-S6), a first primary side half bridge is formed by connecting the first switching tube (S1) and the second switching tube (S2) in series, a second primary side half bridge is formed by connecting the third switching tube (S3) and the fourth switching tube (S4) in series, a third primary side half bridge is formed by connecting the fifth switching tube (S5) and the sixth switching tube (S68642) in series, each switching tube has two ends connected in parallel with an inverse diode, the first terminal of the first switching tube (S1) is connected to the first terminal of the third switching tube (S3), the first terminal of the fifth switching tube (S84), the positive terminal of the filter capacitor (C1), the second terminal of the first switching tube (S1) is connected to the first terminal of the second switching tube (S2), the sixth terminal of the fifth switching tube (S3511) is connected to the positive terminal of the resonant capacitor (S5911), and the sixth terminal of the fourth switching tube (S5911) is connected to the fourth switching tube (S5911), the fourth switching tube (S5911).

3. A C LL C bidirectional dc-dc converter as claimed in claim 2, wherein the primary resonant device (11) comprises first to third series resonant devices, the first series resonant device comprises a first capacitor (C2) and a first inductor connected in series with the first capacitor (C2), the first capacitor (C2) is further connected between the first switching transistor (S1) and the second switching transistor (S2), the first inductor (L) is further connected to one end of a transformer in the transforming means (12), the second series resonant device comprises a second capacitor (C3) and a second inductor (L2) connected in series with the second capacitor (C3), the second capacitor (C3) is further connected between the third switching transistor (S3) and the fourth switching transistor (S4), the second capacitor (C636) is further connected to one end of a transformer in the transforming means (12), the third series resonant device comprises a third capacitor (C4) and a sixth switching transistor (S4642), the third series resonant device comprises a sixth capacitor (C4642) and a fifth series capacitor (S463), and the third switching transistor (S4) is further connected between the third switching transistor (S4642), and the fifth series resonant device comprises a sixth switching transistor (4).

4. A C LL C bidirectional dc-dc converter according to claim 3, wherein said transforming means (12) comprises three transformers (L m1, L0 m2, L1 m3), three transformers (L2 m1, L3 m2, L4 m3) are respectively a first to a third transformer, one primary terminal of said first transformer (L5 m1) is connected to the first inductance (L61) of the first set of primary side series resonant devices, the other primary terminal of the first transformer (L7 m1) is connected to one primary terminal of the second transformer (L8 m2), one primary terminal of the third transformer (2 m2), the other primary terminal of the second transformer (2 m2) is connected to the second inductance (3602) of the second set of series resonant devices, the other primary terminal of the third transformer (2 m2) is connected to the secondary terminal of the third set of primary terminals of the third transformer (2 m2), the other secondary terminal of the third transformer (2 m2) is connected to the secondary terminal of the third set of transformers (2 m2), and the secondary terminal of the third transformer (2 m2) is connected to the secondary terminal of the third set of the third transformer (2 m 2).

5. The C LL C bidirectional DC-DC converter according to claim 4, wherein the secondary resonant device (13) comprises a first to a third set of secondary resonant devices, the first set of secondary resonant devices comprises a first resonant capacitor (C5), the second set of secondary resonant devices comprises a second resonant capacitor (C6), the third set of secondary resonant devices comprises a third resonant capacitor (C7), one end of the first resonant capacitor (C5) is connected to the first transformer, the other end of the first resonant capacitor (C5) is connected to one of the secondary half-bridges, one end of the second resonant capacitor (C6) is connected to the second transformer, the other end of the second resonant capacitor (C6) is connected to one of the secondary half-bridges, one end of the third resonant capacitor (C7) is connected to the third transformer, and the other end of the third resonant capacitor (C7) is connected to one of the secondary half-bridges.

6. A C LL C bidirectional dc-dc converter as claimed in claim 3, wherein the secondary bridge (14) includes seventh to twelfth switching tubes, a first secondary half-bridge is formed by connecting the seventh switching tube (S7) and the eighth switching tube (S8) in series, a second secondary half-bridge is formed by connecting the ninth switching tube (S9) and the tenth switching tube (S10) in series, a third secondary half-bridge is formed by connecting the eleventh switching tube (S11) and the twelfth switching tube (S12) in series, two ends of each switching tube are connected in parallel with a reverse diode, a first end of the seventh switching tube (S7) is connected to a first end of the ninth switching tube (S9), a first end of the eleventh switching tube (S11), a positive electrode of the secondary filter capacitor, a second end of the seventh switching tube (S7) is connected to a first end of the eighth switching tube (S8), a negative electrode of the eighth switching tube (S6313), a second end of the seventh switching tube (S6329) is connected to a negative electrode of the eighth switching tube (S638), a second end of the twelfth switching tube (S638), a second switching tube (S3613) is connected to a second switching tube (S638), a negative electrode of the ninth switching tube (S638), a tenth switching tube (S3613) is connected to a second switching tube (S638).

7. The C LL C bidirectional DC-DC converter according to claim 3, wherein the first to sixth switching tubes further include a primary side control terminal, respectively, and the C LL C bidirectional DC-DC converter further includes a control unit connected to each primary side control terminal for controlling the first to sixth switching tubes to turn on and off, and the switching timing of each primary side half-bridge is sequentially shifted by 120 ° in phase from each other.

8. The C LL C bidirectional DC-DC converter according to claim 6, wherein the seventh to twelfth switching transistors further include a secondary control terminal, respectively, the C LL C bidirectional DC-DC converter further includes a control unit connected to each secondary control terminal for controlling the seventh to twelfth switching transistors to be turned on and off, and the switching timing phases of each secondary half-bridge are sequentially shifted by 120 °.

9. A method for controlling a C LL C bidirectional dc-dc converter, the method being used for controlling a C LL C bidirectional dc-dc converter, the method comprising:

when the energy of the C LL C bidirectional direct current-direct current converter is transmitted from a primary side to a secondary side, a secondary side filter capacitor (C8), a secondary side bridge (14), a secondary side resonance device (13) and the secondary side of a transformer device (12) form a star-connected secondary side three-phase resonance circuit, when the synchronous rectification control is performed, the switching period of each half bridge of the secondary side bridge (14) is the same, the switching time sequence phases of each secondary side half bridge are sequentially staggered by 120 degrees, the switching state of each secondary side half bridge of the secondary side bridge (14) is the same as that of the corresponding primary side half bridge, and a control unit judges whether the current output voltage target value is larger than a threshold value;

when the current output voltage target value is judged to be larger than the threshold value, the control unit controls the secondary side bridge (14) to enter a Boost rectification mode from a synchronous rectification mode in a specific time period, and the switching states of the three secondary side half bridges are simultaneously connected to the output positive or the output negative, so that the secondary side resonance device (13) is in an energy storage state.

10. The method of controlling a C LL C bidirectional dc-dc converter according to claim 9, further comprising:

when the energy of the C LL C bidirectional direct current-direct current converter is transmitted from the secondary side to the primary side, a primary side filter capacitor (C1), a primary side bridge (10), a primary side resonance device (11) and the primary side of a transformation device (12) form a primary side three-phase resonance loop in star connection, when the primary side three-phase resonance loop is used for synchronous rectification control, the switching period of each half bridge of the primary side bridge (10) is the same, the switching time sequence phase of each primary side half bridge is sequentially staggered by 120 degrees, the switching state of each primary side half bridge of the primary side bridge (10) is the same as that of the corresponding secondary side half bridge, and the control unit judges whether the current output voltage target value is larger than a threshold;

when the current output voltage target value is judged to be larger than the threshold value, the control unit controls the primary side bridge (10) to enter a Boost rectification mode from a synchronous rectification mode in a specific time period, and the switching states of the three primary side half bridges are simultaneously connected to the output positive or the output negative, so that the primary side resonance device (11) is in an energy storage state.

Technical Field

The invention relates to the technical field of power electronics, in particular to a C LL C bidirectional direct current-direct current converter and a control method.

Background

At present, in the application occasions of a high-voltage high-power isolated bidirectional DC-DC converter, the selection of power devices is limited, a single full-bridge C LL C is difficult to realize, a common circuit topology structure adopts two full-bridges C LL C in parallel, the parallel connection of the two full-bridges C LL C means that the two full-bridges C LL C work in parallel, each full-bridge C LL C shares half of power, the number of power semiconductor devices is 16, each full-bridge C LL C can realize the bidirectional conversion of energy, however, the technical scheme of the parallel connection of the two full-bridges C LL C adopted at present mainly has the following three disadvantages:

(1) the number of power semiconductor devices is large, and the number of corresponding driving circuits is large, so that the size and the cost of the bidirectional direct current-direct current converter are large;

(2) the two full bridges C LL C are connected in parallel or in staggered parallel in control, so that the high-frequency ripple current of the output filter capacitor is large, the effective value of the ripple current can reach 32% of the output current at most, and the required number of the output filter capacitors is large;

(3) the parallel connection of the two full bridges C LL C requires the addition of a current sharing control circuit, which also increases the cost.

Disclosure of Invention

The invention provides a C LL C bidirectional DC-DC converter and a control method thereof, which have self current sharing capability on hardware, do not need an additional current sharing control circuit and greatly reduce the cost.

The technical scheme is as follows:

the embodiment of the invention provides a C LL C bidirectional DC-DC converter which comprises a primary side filter capacitor (C1), a primary side bridge (10), a primary side resonance device (11), a transformation device (12), a secondary side resonance device (13), a secondary side bridge (14) and a secondary side filter capacitor (C8) which are connected in sequence, wherein the primary side bridge (10) comprises three primary side half bridges, each primary side half bridge is formed by connecting two switching tubes in series, each primary side half bridge is connected with the primary side filter capacitor (C1), the primary side resonance device (11) comprises three groups of primary side series resonance devices, each group of primary side series resonance devices is connected with one primary side half bridge, the transformation device (12) is connected with the primary side resonance device (11) and the secondary side resonance device (13), the secondary side resonance devices (13) comprise three groups, each group of secondary side resonance devices comprises one resonance capacitor, one end of each resonance capacitor is connected with one secondary side terminal of one transformer, the other end of each secondary side half bridge is connected with one secondary side half bridge, each secondary side half bridge (14) comprises three secondary side half bridges, each secondary side half bridges are connected with two secondary side half bridges, and each secondary side half bridge is connected with the secondary side filter capacitor (C8).

In a preferred embodiment of the present invention, the primary side bridge (10) includes first to sixth switching tubes (S1-S6), a first primary side half bridge is formed by connecting the first switching tube (S1) and the second switching tube (S2) in series, a second primary side half bridge is formed by connecting the third switching tube (S3) and the fourth switching tube (S4) in series, a third primary side half bridge is formed by connecting the fifth switching tube (S5) and the sixth switching tube (S6) in series, two ends of each switching tube are connected in parallel with a reverse diode, a first end of the first switching tube (S1) is connected to a first end of the third switching tube (S3), a first end of the fifth switching tube (S5), and an anode of a primary side filter capacitor (C1), a second end of the first switching tube (S1) is connected to a first end of the second switching tube (S2), the resonator (11), and a cathode (C1) of the second switching tube (S2) is connected to a cathode (C1) of the filter capacitor (C1), The second end of the fourth switching tube (S4) is connected with the second end of the sixth switching tube (S6), the second end of the third switching tube (S3) is connected with the first end of the fourth switching tube (S4) and the primary side resonance device (11), and the second end of the fifth switching tube (S5) is connected with the first end of the sixth switching tube (S6) and the primary side resonance device (11).

In a preferred embodiment of the present invention, the primary side resonant device (11) includes first to third sets of primary side series resonant devices, the first set of primary side series resonant devices includes a first capacitor (C2) and a first inductor connected in series with a first capacitor (C2), the first capacitor (C2) is further connected between a first switching tube (S1) and a second switching tube (S2), the first inductor (L1) is further connected to one end of a transformer in the transformer apparatus (12), the second set of primary side series resonant devices includes a second capacitor (C3) and a second inductor (L) connected in series with a second capacitor (C3), the second capacitor (C3) is further connected between a third switching tube (S3) and a fourth switching tube (S4), the second inductor (L) is further connected to one end of a transformer in the transformer apparatus (12), the third set of series resonant devices includes a third capacitor (C4) and a third capacitor (C4), the third inductor (S638) is further connected between a sixth switching tube (S633) and a sixth switching tube (S353) of the transformer apparatus (3642), and a sixth switching tube (S633) is further connected between the third switching tube (S633).

In a preferred embodiment of the present invention, the transforming device (12) comprises three transformers (L m1, L m2, L0 m3), three transformers (L1 m1, L2 m2, L3 m3) are respectively a first to a third transformer, one primary terminal of the first transformer (L4 m1) is connected to a first inductance (L51) of the first set of primary side series resonant devices, the other primary terminal of the first transformer (L6 m1) is connected to one primary terminal of the second transformer (L7 m2), one primary terminal of the third transformer (L8 m3), the other primary terminal of the second transformer (L9 m L) is connected to a second inductance (L) of the second set of primary side series resonant devices, the other primary terminal of the third transformer (360 m L) is connected to a third inductance (363) of the third set of series resonant devices, the other secondary terminal of the first transformer (L m L) is connected to the other secondary terminal of the third transformer (L m L), the second transformer (L m L) is connected to the other secondary terminal of the third transformer (L m L, the third transformer (L m L) and the secondary terminal of the third transformer (L m L).

In a preferred embodiment of the present invention, the secondary resonant device (13) includes first to third sets of secondary resonant devices, the first set of secondary resonant devices includes a first resonant capacitor (C5), the second set of secondary resonant devices includes a second resonant capacitor (C6), the third set of secondary resonant devices includes a third resonant capacitor (C7), one end of the first resonant capacitor (C5) is connected to the first transformer, the other end of the first resonant capacitor (C5) is connected to one of the secondary half-bridges, one end of the second resonant capacitor (C6) is connected to the second transformer, the other end of the second resonant capacitor (C6) is connected to one of the secondary half-bridges, one end of the third resonant capacitor (C7) is connected to the third transformer, and the other end of the third resonant capacitor (C7) is connected to one of the secondary half-bridges.

In a preferred embodiment of the present invention, the secondary side bridge (14) includes seventh to twelfth switching tubes, a first secondary side half-bridge is formed by connecting the seventh switching tube (S7) and the eighth switching tube (S8) in series, a second secondary side half-bridge is formed by connecting the ninth switching tube (S9) and the tenth switching tube (S10) in series, a third secondary side half-bridge is formed by connecting the eleventh switching tube (S11) and the twelfth switching tube (S12) in series, two ends of each switching tube are connected in parallel to a reverse diode, a first end of the seventh switching tube (S7) is connected to a first end of the ninth switching tube (S9), a first end of the eleventh switching tube (S11), and an anode of the secondary side filter capacitor, a second end of the seventh switching tube (S7) is connected to a first end of the eighth switching tube (S8), the secondary side resonant device (13), and a second end of the eighth switching tube (S8) is connected to a cathode of the secondary side filter capacitor (S5392), and a cathode of the secondary side filter capacitor (S10), And a second end of the twelfth switching tube (S12) is connected, a second end of the ninth switching tube (S9) is connected with a first end of the tenth switching tube (S10) and the secondary side resonance device (13), and a second end of the eleventh switching tube (S11) is connected with a first end of the twelfth switching tube (S12) and the secondary side resonance device (13), wherein the switching tubes are field effect transistors.

In a preferred embodiment of the present invention, the first to sixth switching tubes further include a primary side control end, and the C LL C bidirectional dc-dc converter further includes a control unit, connected to each primary side control end, for controlling the on and off of the first to sixth switching tubes, and the switching timing phases of each primary side half-bridge are sequentially shifted by 120 °.

In a preferred embodiment of the present invention, the seventh to twelfth switching tubes further include a secondary control end, respectively, the C LL C bidirectional dc-dc converter further includes a control unit, connected to each secondary control end, for controlling the seventh to twelfth switching tubes to be turned on and off, and the switching timing phases of each secondary half-bridge are sequentially staggered by 120 °.

The embodiment of the invention also provides a control method of the C LL C bidirectional DC-DC converter, which is used for controlling the C LL C bidirectional DC-DC converter and comprises the steps that when the energy of the C LL C bidirectional DC-DC converter is transmitted from a primary side to a secondary side, a secondary side filter capacitor (C8), a secondary side bridge (14), a secondary side resonant device (13) and a secondary side of a transformer device (12) form a star-connected secondary side three-phase resonant loop, when the synchronous rectification control is performed, the switching period of each half bridge of the secondary side bridge (14) is the same, the switching timing phase of each secondary side half bridge is staggered by 120 degrees in sequence, the switching state of each secondary side half bridge of the secondary side bridge (14) is the same as the switching state of the corresponding primary side half bridge, a control unit judges whether a current output voltage target value is larger than a threshold value or not, and when the current output voltage target value is judged to be larger than the threshold value, the control unit controls the secondary side bridge (14) to enter a Boost rectification mode from the synchronous rectification mode in a specific time period, the three secondary side resonant states are simultaneously connected to a positive side resonant device or a negative side, and the three secondary side output is connected to the secondary side.

In a preferred embodiment of the invention, the method further comprises the steps that when energy of a C LL C bidirectional direct current-direct current converter is transmitted from a secondary side to a primary side, a primary side filter capacitor (C1), a primary side bridge (10), a primary side resonance device (11) and a primary side of a transformation device (12) form a star-connected primary side three-phase resonant circuit, when the primary side three-phase resonant circuit is used as synchronous rectification control, the switching period of each half bridge of the primary side bridge (10) is the same, the switching time sequence phase of each primary side half bridge is sequentially staggered by 120 degrees, the switching state of each primary side half bridge of the primary side bridge (10) is the same as the switching state of the corresponding secondary side half bridge, a control unit judges whether a current output voltage target value is larger than a threshold value or not, when the current output voltage target value is judged, the control unit controls the primary side bridge (10) to enter a rectification mode from the synchronous rectification mode in a specific time period, the switching states of the three primary side half bridges are simultaneously connected to an.

The technical scheme provided by the embodiment of the invention has the following beneficial effects:

when energy is transmitted from the primary side to the secondary side, the secondary side bridge is used as active control, the primary side bridge is used as rectification control, forward power conversion from the primary side to the secondary side can be achieved, when energy is transmitted from the secondary side to the primary side, the secondary side bridge is used as active control, the primary side bridge is used as rectification control, reverse power conversion from the secondary side to the primary side can be achieved, zero-voltage switching-on soft switching of a secondary side switching tube can be achieved during reverse discharging, and hard switching is not achieved, so that high-frequency current ripples of filter capacitors of the primary side and the secondary side can be reduced, performance of the converter is improved, size and cost of the bidirectional direct current-direct current converter are reduced, the primary side and the secondary side of a transformation device of the three-phase alternating C LL C bidirectional direct current-direct current converter are connected in a star-shaped mode, three-phase currents are mutually looped, current sharing capability is achieved on hardware, an additional current sharing control circuit is not needed, and control cost is not.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings.

Drawings

Fig. 1 is a block diagram of a C LL C bidirectional dc-dc converter according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram of the C LL C bidirectional DC-DC converter of FIG. 1;

FIG. 3a is a current-holding loop diagram of the C LL C bidirectional DC-DC converter in a first operating mode;

FIG. 3b is a current-storing loop diagram of the bidirectional DC-DC converter C LL C in the second operation mode;

FIG. 3C is a current-holding loop diagram of the C LL C bi-directional DC-DC converter in the third operating mode;

FIG. 3d is a current-storing loop diagram of the C LL C bi-directional DC-DC converter in the fourth operating mode;

FIG. 3e is a current-holding loop diagram of the C LL C bi-directional DC-DC converter in the fifth operating mode;

FIG. 3f is a current-holding loop diagram of the C LL C bidirectional DC-DC converter in the sixth operating mode;

FIG. 4 is a graph of the operating waveform, primary current, and secondary current of a typical synchronous rectified output of a C LL C bidirectional DC-DC converter during forward power conversion;

fig. 5 is a flowchart illustrating steps of a method for controlling the C LL C bi-directional dc-dc converter according to a second embodiment of the present invention;

FIG. 6 is a diagram of exemplary operating waveforms of the second embodiment of the present invention with converter energy transferred from the primary side to the secondary side;

FIG. 7a is a schematic diagram of a tank current loop in which three secondary half-bridges are connected to output positive in BOOST rectification mode when converter energy is transferred from the primary side to the secondary side according to the second embodiment of the present invention;

FIG. 7b is a schematic diagram of a tank current loop in which all three secondary half-bridges are connected to the output negative in BOOST rectification mode when converter energy is transferred from the primary side to the secondary side according to the second embodiment of the present invention;

fig. 7c is a schematic diagram of a tank current loop in which all three primary half-bridges are connected to output positive in BOOST rectification mode when converter energy is transferred from the secondary side to the primary side according to the second embodiment of the present invention;

fig. 7d is a tank current loop diagram of the second embodiment of the present invention in which three primary half-bridges are connected to output negative in BOOST rectification mode when the converter energy is transferred from the secondary side to the primary side.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be made on specific embodiments, structures, features and effects of the C LL C bi-directional dc-dc converter and the control method according to the present invention with reference to the accompanying drawings and preferred embodiments.

The foregoing and other technical and scientific aspects, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings. While the present invention has been described in connection with the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications, equivalent arrangements, and specific embodiments thereof.

First embodiment

Fig. 1 is a block diagram of a C LL C bidirectional dc-dc converter according to a first embodiment of the present invention, fig. 2 is a circuit diagram of the C LL C bidirectional dc-dc converter in fig. 1, the C LL C bidirectional dc-dc converter has a current sharing capability in hardware, and an additional current sharing control circuit is not required, so that the cost is greatly reduced, referring to fig. 1 and fig. 2, the C LL C bidirectional dc-dc converter of the present embodiment includes a primary side filter capacitor C1, a primary side bridge 10, a primary side resonant device 11, a voltage transformation device 12, a secondary side resonant device 13, a secondary side bridge 14, and a secondary side filter capacitor C8, which are sequentially connected.

Specifically, the primary bridge 10 includes three primary half bridges, each of which is formed by connecting two switching tubes in series, and each of the primary half bridges is connected to the positive electrode and the negative electrode of the primary filter capacitor C1. Specifically, the primary side bridge 10 includes first to sixth switching tubes S1-S6, a first primary side half bridge is formed by connecting the first and second switching tubes S1 and S2 in series, a second primary side half bridge is formed by connecting the third and fourth switching tubes S3 and S4 in series, a third primary side half bridge is formed by connecting the fifth and sixth switching tubes S5 and S6 in series, and two ends of each switching tube are connected in parallel with a backward diode. A first end of the first switch tube S1 is connected to a first end of the third switch tube S3, a first end of the fifth switch tube S5, and an anode of the primary side filter capacitor C1, a second end of the first switch tube S1 is connected to a first end of the second switch tube S2 and the primary side resonator 11, a second end of the second switch tube S2 is connected to a cathode of the primary side filter capacitor C1, a second end of the fourth switch tube S4, and a second end of the sixth switch tube S6, a second end of the third switch tube S3 is connected to a first end of the fourth switch tube S4 and the primary side resonator 11, and a second end of the fifth switch tube S5 is connected to a first end of the sixth switch tube S6 and the primary side resonator 11.

When energy is required to be transmitted from the primary side to the secondary side, the primary side bridge 10 is required to be used as active control, and the secondary side bridge 14 is used as rectification control, so that forward power conversion from the primary side to the secondary side can be realized; when the required energy is transferred from the secondary side to the primary side, the secondary side bridge 14 is required to be used as active control, and the primary side bridge 10 is used as rectification control, so that reverse power conversion from the secondary side to the primary side can be realized.

Preferably, each of the first to sixth switching tubes S1-S6 is a semiconductor switch, and may be, for example, a field effect transistor, and the first terminal may be a source (S) or a drain (D) of the transistor, and correspondingly, the second terminal may be a drain or a source of the transistor.

Preferably, the first to sixth switching tubes S1-S6 may further include a primary side control terminal (for example, the gate G), and the C LL C bidirectional dc-dc converter further includes a control unit (not shown in the figure), the control unit is connected to each primary side control terminal for controlling the first to sixth switching tubes S1-S6 to be turned on and off, and the switching timing phases of each primary side half bridge are sequentially shifted by 120 °.

Specifically, the primary side resonant device 11 comprises first to third groups of primary side series resonant devices, the first group of primary side series resonant devices comprises a first capacitor C2 and a first inductor L connected in series with the first capacitor C2, the first capacitor C2 is further connected between a first switching tube S1 and a second switching tube S2, the first inductor L is further connected to one end of a transformer in the transformation device 12, the second group of primary side series resonant devices comprises a second capacitor C3 and a second inductor L2 connected in series with the second capacitor C3, the second capacitor C3 is further connected between the third switching tube S3 and a fourth switching tube S4, the second inductor L2 is further connected to one end of a transformer in the transformation device 12, the third group of primary side series resonant devices comprises a third capacitor C4 and a third inductor 463 connected in series with the third capacitor C4, the third inductor is further connected between a third inductor S465 and a sixth switching tube S L connected between the third capacitor C4624 and a fifth switching tube S5.

The transformation device 12 comprises three transformers m, 0m, each transformer comprising a primary side and a secondary side (i.e. the primary side and the secondary side of the transformation device), the primary side of each transformer having two primary side terminals, one of which is connected to a set of primary side series resonant devices and the other of which is connected to the primary side terminals of two other transformers, forming a star connection on the primary side of the transformer, the secondary side of each transformer having two secondary side terminals, one of which is connected to a set of secondary side resonant devices and the other of which is connected to the secondary side terminals of two other transformers, forming a star connection on the secondary side of the transformer, specifically, the three transformers are 1m, 2m, 3m, respectively, one primary side terminal of the first transformer 4m is connected to a first inductance 51 of the first set of primary side series resonant devices, the other primary side terminal of the first transformer 6m is connected to one primary side terminal of the second transformer 7m, one primary side terminal of the third transformer 8m, the other primary side terminal of the second transformer 9m is connected to a second inductance 2 of the second set of primary side series resonant devices, the second transformer, the other secondary side terminal of the third transformer is connected to a third secondary side of the third transformer m, and the third secondary side of the third transformer is connected to the third secondary side resonant devices, and the third secondary side of the third transformer m is connected to the third secondary side of the third transformer, and the third secondary side of the third transformer, the third secondary side of.

The secondary resonant device 13 comprises three sets of secondary resonant devices C5, C6 and C7 in total from the first set to the third set, each set of secondary resonant device comprises a resonant capacitor, one end of each resonant capacitor is connected with a secondary terminal of a transformer, and the other end of each resonant capacitor is connected with a secondary half-bridge in a secondary bridge, specifically, the first set of secondary resonant devices comprises a first resonant capacitor C5, the second set of secondary resonant devices comprises a second resonant capacitor C6, the third set of secondary resonant devices comprises a third resonant capacitor C7, one end of the first resonant capacitor C5 is connected with the first transformer, the other end of the resonant capacitor C5 is connected with a secondary half-bridge in the secondary bridge, one end of the second resonant capacitor C6 is connected with the second transformer, the other end of the second resonant capacitor C6 is connected with a secondary half-bridge in the secondary bridge, one end of the third resonant capacitor C7 is connected with the third transformer, the other end of the third resonant capacitor C7 is connected with a secondary half-bridge in the secondary bridge, and when the secondary resonant switches C5 are connected with a primary switch, the primary switch is switched on-off, and when the secondary switch is switched on, zero, the secondary switch is switched on, the primary switch is switched on, and zero, the secondary switch of the secondary switch, and zero, the secondary switch, and when the secondary switch is switched on secondary switch, the secondary switch is switched on switch, the primary switch is switched on switch, zero, the primary switch.

The secondary side bridge 14 comprises three secondary side half bridges, each of which is formed by two switching tubes connected in series. Specifically, the secondary bridge 10 includes seventh to twelfth switching tubes S7-S12, a first secondary half-bridge is formed by connecting seventh and eighth switching tubes S7, S8 in series, a second secondary half-bridge is formed by connecting ninth and tenth switching tubes S9, S10 in series, a third secondary half-bridge is formed by connecting eleventh and twelfth switching tubes S11, S12 in series, and a reverse diode is connected in parallel at two ends of each switching tube. A first end of the seventh switching tube S7 is connected to a first end of the ninth switching tube S9, a first end of the eleventh switching tube S11 and an anode of the secondary filter capacitor C8, a second end of the seventh switching tube S7 is connected to a first end of the eighth switching tube S8 and the secondary resonant device 13, a second end of the eighth switching tube S8 is connected to a cathode of the secondary filter capacitor C8, a second end of the tenth switching tube S10 and a second end of the twelfth switching tube S12, a second end of the ninth switching tube S9 is connected to a first end of the tenth switching tube S10 and the secondary resonant device 13, and a second end of the eleventh switching tube S11 is connected to a first end of the twelfth switching tube S12 and the secondary resonant device 13.

Preferably, the seventh to twelfth switching tubes S7-S12 are all semiconductor switches, and may be field effect transistors, for example, the first terminal may be a source (S) or a drain (D) of the transistor, and correspondingly, the second terminal may be a drain or a source of the transistor. And the first primary half-bridge, the second primary half-bridge and the third primary half-bridge of the primary bridge respectively correspond to the first secondary half-bridge, the second secondary half-bridge and the third secondary half-bridge of the secondary bridge.

Preferably, the seventh to twelfth switching tubes S7-S12 may further include a secondary control terminal (for example, a gate G), and a control unit is connected to each secondary control terminal for controlling the seventh to twelfth switching tubes S7-S12 to turn on and off, and the switching timing phases of each secondary half-bridge are sequentially shifted by 120 °.

A primary side three-phase resonant circuit in star connection is formed by a primary side bridge, a primary side resonant device and a primary side of a voltage transformation device. When the primary three-phase resonant circuit is used for active control, the switching cycles of each primary half-bridge of the primary bridge are the same (namely the switching cycles of the switching tubes S1-S6 are the same), but the switching time sequence phases of each primary half-bridge are sequentially staggered by 120 degrees, namely the switching time sequences of the first switching tube S1, the third switching tube S3 and the fifth switching tube S5 are sequentially staggered by 120 degrees, so that three-phase staggered resonance of the primary three-phase resonant circuit is realized. When a primary side three-phase resonant circuit (comprising a primary side bridge, a primary side resonant device and a primary side winding of a voltage transformation device) is used for rectification control, a semiconductor switching tube of each half bridge of the primary side bridge can be kept closed, and an anti-parallel diode of the semiconductor switching tube can play a role in rectification; the semiconductor switching tubes of the half-bridge corresponding to the secondary bridge (i.e., the switching tubes S1, S3, S5 correspond to the switching tubes S11, S9, S7, respectively, and the switching tubes S2, S4, S6 correspond to the switching tubes S12, S10, S8, respectively) may be maintained in the same switching state, so that the semiconductor switching tube body may perform the rectifying function.

In addition, a star-connected secondary three-phase resonant circuit is formed by the secondary bridge, the secondary resonant device and the secondary side of the transformer. When the secondary three-phase resonant circuit (comprising a secondary transformer winding, a secondary resonant capacitor and a secondary bridge) in star connection is used for active control, the switching cycles of each half bridge of the secondary bridge are the same (the switching cycles of the switching tubes S7-S12 are the same), but the switching time sequence phases of each secondary half bridge are staggered by 120 degrees in sequence, so that three-phase staggered resonance of the secondary three-phase resonant circuit is realized.

In addition, when the star-connected secondary three-phase resonant circuit is used for rectification control, the semiconductor switch tube of each half bridge of the secondary bridge can be kept closed, and the anti-parallel diode of the semiconductor switch tube can play a role in rectification; the semiconductor switch tube of the half bridge at the position corresponding to the primary side bridge can be kept in the same switch state, and the semiconductor switch tube body can play a role in rectification.

The invention can realize high-voltage high-power bidirectional soft switch DC-DC power conversion, and because the three-phase bridge is in three-phase interleaved control, the invention can reduce the high-frequency current ripple of the filter capacitors of the primary side and the secondary side, namely the capacity of the filter capacitors of the primary side and the secondary side, thereby reducing the volume and the cost of the bidirectional DC-DC converter.

The three-phase alternating C LL C bidirectional DC-DC converter has the following six working modes when energy is transferred from a primary side to a secondary side:

the first working mode is as follows: the switching tube states of the primary side bridge are respectively switching tube S1 closed, switching tube S2 open, switching tube S3 open, switching tube S4 closed, switching tube S5 closed and switching tube S6 open, the switching tube states of the secondary side bridge are respectively switching tube S11 closed, switching tube S12 open, switching tube S9 open, switching tube S10 closed, switching tube S7 closed and switching tube S8 open, and the energy flow loop is shown in FIG. 3 a.

And a second working mode: the switching tube states of the primary side bridge are respectively switching tube S1 closed, switching tube S2 open, switching tube S3 open, switching tube S4 closed, switching tube S5 open and switching tube S6 closed, the switching tube states of the secondary side bridge are respectively switching tube S11 closed, switching tube S12 open, switching tube S9 open, switching tube S10 closed, switching tube S7 open and switching tube S8 closed, and the energy flow loop is shown in FIG. 3 b.

And a third working mode: the switching tube states of the primary side bridge are respectively switching tube S1 closed, switching tube S2 open, switching tube S3 closed, switching tube S4 open, switching tube S5 open and switching tube S6 closed, the switching tube states of the secondary side bridge are respectively switching tube S11 closed, switching tube S12 open, switching tube S9 closed, switching tube S10 open, switching tube S7 open and switching tube S8 closed, and the energy flow loop is shown in FIG. 3 c.

And a fourth working mode: the switching tube states of the primary side bridge are respectively switching tube S1 open, switching tube S2 closed, switching tube S3 closed, switching tube S4 open, switching tube S5 open and switching tube S6 closed, the switching tube states of the secondary side bridge are respectively switching tube S11 open, switching tube S12 closed, switching tube S9 closed, switching tube S10 open, switching tube S7 open and switching tube S8 closed, and the energy flow loop is shown in FIG. 3 d.

And a fifth working mode: the switching tube states of the primary side bridge are respectively switching tube S1 open, switching tube S2 closed, switching tube S3 closed, switching tube S4 open, switching tube S5 closed and switching tube S6 open, the switching tube states of the secondary side bridge are respectively switching tube S11 open, switching tube S12 closed, switching tube S9 closed, switching tube S10 open, switching tube S7 closed and switching tube S8 open, and the energy flow loop is shown in FIG. 3 e.

And a sixth working mode: the switching tube states of the primary side bridge are respectively switching tube S1 open, switching tube S2 closed, switching tube S3 open, switching tube S4 closed, switching tube S5 closed and switching tube S6 open, the switching tube states of the secondary side bridge are respectively switching tube S11 open, switching tube S12 closed, switching tube S9 open, switching tube S10 closed, switching tube S7 closed and switching tube S8 open, and the energy flow loop is shown in FIG. 3 f.

The C LL C bi-directional dc-dc converter also has six operating modes when energy is transferred from the secondary side to the primary side, one for each mode when energy is transferred from the primary side to the secondary side.

In the three-phase interleaved C LL C bidirectional dc-dc converter, the control of power conversion is a frequency modulation control, the driving waveforms of the two switching tubes of each half-bridge are complementary, the duty ratio is close to 50% (considering dead time), and the typical synchronous rectification output working waveform, the primary current and the secondary current are as shown in fig. 4.

In summary, in the C LL C bidirectional dc-dc converter provided in the embodiment of the present invention, when energy is transferred from the primary side to the secondary side, the primary side bridge is used as active control, and the secondary side bridge is used as rectification control, so that forward power conversion from the primary side to the secondary side can be achieved, when energy is transferred from the secondary side to the primary side, the secondary side bridge is used as active control, and the primary side bridge is used as rectification control, so that reverse power conversion from the secondary side to the primary side can be achieved, and during reverse discharge, a zero-voltage-open soft switch of a secondary side switching tube can be achieved instead of a hard switch, so that high-frequency current ripples of filter capacitors of the primary side and the secondary side can be reduced, the performance of the converter is improved, the volume and the cost of the bidirectional dc-dc converter are reduced, and the primary side and the secondary side of a transformation device of a three-phase interleaved C LL C bidirectional dc-dc converter are both in a star connection method, and three-phase currents are in a loop, so that the converter has a current sharing capability, and an additional.

The following are embodiments of the method of the present invention, details of which are not described in detail in the method embodiments, and reference may be made to the corresponding apparatus embodiments described above.

Second embodiment

At present, there are many ways for the rectification output of the three-phase interleaved C LL C bidirectional dc-dc converter, and there are three-phase bridge type synchronous rectification outputs in common, as shown in fig. 4, the driving waveforms of the primary side and the secondary side are the same, but with the adoption of the synchronous rectification output way, the voltage value of the synchronous rectification output of the C LL C bidirectional dc-dc converter is limited by the output voltage gain of the converter, if the output voltage range is further increased, the design turn ratio of the transformer needs to be increased, but the size of the magnetic core and the number of turns of the coil are increased, so that the volume and the cost of the three-phase interleaved C LL C bidirectional dc-dc converter are increased.

In order to solve the problems, the invention provides a novel control mode, when a three-phase interleaved C LL C converter performs power conversion, a control unit of the converter acquires the current output voltage, and if the target value of the current output voltage is judged to be larger than a threshold value, a three-phase bridge on an energy receiving side is enabled to enter a Boost rectification mode from a synchronous rectification mode.

Therefore, it can be seen that when the three-phase bridge on the energy receiving side enters the Boost rectification mode, the upper limit of the output voltage of the three-phase interleaved C LL C bidirectional dc-dc converter can be further increased, and compared with the case of only adopting the synchronous rectification mode, the cost and the volume of the C LL C bidirectional dc-dc converter can be reduced.

When energy is required to be transmitted from the primary side to the secondary side, the primary side bridge is required to be used as an energy transmitting side, and the secondary side bridge is required to be used as an energy receiving side. When energy is required to be transmitted from the secondary side to the primary side, the secondary side bridge is required to be used as an energy transmitting side, and the primary side bridge is required to be used as an energy receiving side. When the output voltage target value is judged to be larger than the threshold value, the three-phase bridge on the energy receiving side enters a Boost rectification mode from a synchronous rectification mode in a specific time period, so that the output voltage can be further improved. A specific time period is in each operating mode.

Fig. 5 is a flowchart of a control method of a C LL C bidirectional dc-dc converter according to a second embodiment of the present invention, the control method of the C LL C bidirectional dc-dc converter according to this embodiment for controlling the C LL C bidirectional dc-dc converter as described above may include the following steps 501-503:

step 501, when energy of a C LL C bidirectional dc-dc converter is transmitted from a primary side to a secondary side, a secondary side filter capacitor C8, a secondary side bridge 14, a secondary side resonance device 13, and a secondary side of a transformer 12 form a star-connected secondary side three-phase resonance circuit, which is used as synchronous rectification control, a switching cycle of each half bridge of the secondary side bridge is the same, a switching timing phase of each secondary side half bridge is sequentially staggered by 120 °, a switching state of each secondary side half bridge of the secondary side bridge is the same as a switching state of a corresponding primary side half bridge, a control unit determines whether a current output voltage target value is greater than a threshold (can be preset), when the current output voltage target value is greater than the threshold, step 403 is performed, and if the current output voltage target value is not greater than the threshold, the method is finished.

In step 503, the control unit controls the three-phase bridge, i.e., the secondary side bridge, on the energy receiving side to enter a Boost rectification mode from a synchronous rectification mode within a specific time period, and the switching states of the three secondary side half bridges are simultaneously connected to the output positive (+) or simultaneously connected to the output negative (-) so that the secondary side resonant device is in an energy storage state.

Preferably, the control method of the C LL C bidirectional dc-dc converter may further include steps 605 and 607.

Step 505, when the energy of the C LL C bidirectional dc-dc converter is transmitted from the secondary side to the primary side, the primary side filter capacitor C1, the primary side bridge 10, the primary side resonance device 11, and the primary side of the transformer 12 form a primary side three-phase resonance circuit connected in a star, and when the primary side three-phase resonance circuit is used as synchronous rectification control, the switching cycles of each half bridge of the primary side bridge are the same, the switching timing phases of each primary side half bridge are sequentially staggered by 120 °, and the switching state of each primary side half bridge of the primary side bridge is the same as the switching state of the corresponding secondary side half bridge, the control unit determines whether the current output voltage target value is greater than a threshold value, when the current output voltage target value is determined to be greater than the threshold value, step 407 is.

In step 507, the control unit controls the three-phase bridge, i.e., the primary bridge, on the energy receiving side to enter a Boost rectification mode from a synchronous rectification mode within a specific time period, and the switching states of the three primary half-bridges are simultaneously connected to the output positive (+) or simultaneously connected to the output negative (-) so that the primary resonant device is in an energy storage state.

Wherein, the steps 501-503 can be interchanged with the steps 505-507.

Taking the example of energy transfer from the primary side to the secondary side, the C LL C bidirectional dc-dc converter has six operating modes, and when the converter enters the Boost rectifying mode from the synchronous rectifying mode in a specific time period, the specific time period is in each operating mode, and its typical operating waveform is shown in fig. 6.

When energy is transferred from the primary side to the secondary side and enters a Boost rectification mode, the switching states of the three half bridges of the secondary side can be simultaneously connected to the output positive, i.e., S11 is closed, S12 is open, S9 is closed, S10 is open, S7 is closed, and S8 is open, and the energy storage current loop is as shown in fig. 7 a.

When energy is transferred from the primary side to the secondary side and enters a Boost rectification mode, the switching states of the three half bridges of the secondary side can be simultaneously connected to the output negative, i.e., S11 open, S12 closed, S9 open, S10 closed, S7 open, S8 closed, and the energy storage current loop is as shown in fig. 7 b.

When energy is transmitted from the secondary side to the primary side and enters a Boost rectification mode, the switching states of the three half bridges on the primary side can be simultaneously connected to the output positive, namely S1 is closed, S2 is opened, S3 is closed, S4 is opened, S5 is closed, S6 is opened, and the energy storage current loop is shown in FIG. 7 c.

When energy is transmitted from the secondary side to the primary side and enters a Boost rectification mode, the switching states of the three half bridges on the primary side can be simultaneously connected to the output positive, i.e., S1 open, S2 closed, S3 open, S4 closed, S5 open, S6 closed, and the energy storage current loop is as shown in fig. 7 d.

In summary, according to the control method of the C LL C bidirectional dc-dc converter provided in the embodiment of the present invention, when the three-phase bridge on the energy receiving side enters the Boost rectification mode from the synchronous rectification mode, the upper limit of the output voltage of the three-phase interleaved C LL C bidirectional dc-dc converter may be further increased, and compared with the case of only adopting the synchronous rectification mode, the cost and the volume of the C LL C bidirectional dc-dc converter may be further reduced.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.