CN112751474B

CN112751474B - Three-phase LLC resonant DC converter

Info

Publication number: CN112751474B
Application number: CN202011400396.0A
Authority: CN
Inventors: 王涵宇; 庄加才; 徐君; 刘威
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2020-12-02
Filing date: 2020-12-02
Publication date: 2022-02-25
Anticipated expiration: 2040-12-02
Also published as: CN112751474A

Abstract

The invention provides a three-phase LLC resonant direct-current converter, which is a three-phase three-port topology, namely a primary side circuit and two secondary side circuits are arranged, each circuit is a three-phase conversion circuit, and the three-phase conversion circuits are output in a staggered manner, so that the phase angles of the three-phase conversion circuits in the three-phase LLC resonant direct-current converter are staggered by 120 degrees, and ripple current at the side of a bus is greatly offset; and energy circulation modes are different between the primary side circuit and the first secondary side circuit and between the primary side circuit and the second secondary side circuit, so that independent regulation of voltage of each port of the three-phase LLC resonant direct-current converter is realized, the frequency and amplitude of ripple current on the output side of each port can be controlled respectively, and the ripple current on the bus side of the three-phase LLC resonant direct-current converter is improved remarkably.

Description

Three-phase LLC resonant DC converter

Technical Field

The invention relates to the technical field of power electronics, in particular to a three-phase LLC resonant direct-current converter.

Background

An LLC resonant converter, which is a kind of high-frequency soft switching converter, has many advantages over a converter operating in a hard switching state, such as a wider operating range, a small switching loss of its MOS transistor, an excellent EMI (Electromagnetic Interference) performance, and a high-frequency high efficiency, and is widely used.

However, the structure schematic diagram of the single-phase LLC resonant converter in the prior art is shown in fig. 1, when the single-phase LLC resonant converter is designed as a high-power converter, the output current ripple is large, which causes the output filter capacitor to generate heat seriously, resulting in capacitor failure, thereby shortening the service life of the power supply.

Therefore, the prior art proposes a two-phase LLC resonant converter, as shown in fig. 2 to fig. 4, fig. 2 discloses a two-port (as shown by Vin +, Vin-, and Vo +, Vo-in fig. 2) converter, fig. 3 and fig. 4 disclose a three-port (as shown by V1, V2, and V3 in fig. 3 and fig. 4) isolation converter, taking fig. 2 as an example, which achieves the purposes of reducing the circulating current loss and reducing the output current ripple by a two-way output interleaved series structure. However, the two-port or three-port LLC resonant converter can only reduce the power of each converter to half of the original power, i.e. the effect of reducing the output current ripple is not ideal.

Disclosure of Invention

In view of this, embodiments of the present invention provide a three-phase LLC resonant dc converter to realize independent regulation of voltage at each port, so as to significantly improve ripple current at a bus side.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

the invention provides a three-phase LLC resonant DC converter, which is characterized by comprising: the transformer comprises a primary side circuit, a first secondary side circuit, a second secondary side circuit and a transformer; wherein:

the primary side circuit, the first secondary side circuit and the second secondary side circuit are all three-phase conversion circuits;

the three phases at the alternating current side of the primary side circuit are directly or indirectly connected with the three-phase primary side winding of the transformer correspondingly;

the three-phase first secondary winding of the transformer is correspondingly connected with the alternating current side III of the first secondary circuit;

the three-phase second secondary winding of the transformer is directly or indirectly connected with the three phases at the alternating current side of the second secondary circuit correspondingly;

and energy circulation modes between the primary side circuit and the first secondary side circuit and between the primary side circuit and the second secondary side circuit are different, so that independent regulation of the voltage of each port of the three-phase LLC resonant direct-current converter is realized.

Preferably, at least one of the synonym terminals of the three phases at the alternating current side of the primary circuit, the three-phase primary winding of the transformer and the three-phase secondary winding of the transformer has at least two groups of adjacent phases, and at least one interphase circuit is arranged between two phases of each group of adjacent phases, so as to realize corresponding function multiplexing during power transmission.

Preferably, at least two groups of adjacent phases exist in the three phases on the alternating current side of the primary side circuit, and the inter-phase circuit arranged between two phases of each group of adjacent phases is a first inter-phase circuit.

Preferably, the first inter-phase circuit includes: a first inductor.

Preferably, the first inter-phase circuit further includes: a switch connected in series with the first inductor.

Preferably, the method further comprises the following steps: and the three resonant circuits are respectively arranged on corresponding branches between the primary side circuit and the midpoint of the primary side of the transformer.

Preferably, the resonance circuit includes: at least one first capacitor and at least one second inductor;

each first capacitor, each second inductor and the corresponding primary winding in the transformer are connected in series, one end of each series is connected with the corresponding phase of the alternating current side of the primary circuit, and the other end of each series is connected with the middle point of the primary side of the transformer.

Preferably, each primary winding of the transformer is connected in parallel with a corresponding excitation inductor.

Preferably, the secondary side circuit is an alternating current/direct current bidirectional conversion circuit.

Preferably, at least two groups of adjacent phases at different name ends of the three-phase primary winding of the transformer are provided, and an interphase circuit arranged between two phases of each group of adjacent phases is a second interphase circuit.

Preferably, only two groups of adjacent phases exist in the different-name ends of the three-phase primary windings of the transformer, and the second inter-phase circuit is arranged between two phases of each group of adjacent phases.

Preferably, the second phase-to-phase circuit includes: at least one second capacitor and at least one third inductor connected in series.

Preferably, at least two groups of adjacent phases exist in the different-name ends of the three-phase second secondary winding of the transformer, and an interphase circuit arranged between two phases of each group of adjacent phases is a third interphase circuit, so that multiplexing of phase shifting functions in a forward working mode when energy is transmitted from the primary side to the corresponding secondary side is realized.

Preferably, only two groups of adjacent phases exist in the different name ends of the three-phase second secondary winding of the transformer, and one third inter-phase circuit is arranged between two phases of each group of adjacent phases.

Preferably, the third phase-to-phase circuit includes: and a third inductor.

Preferably, when there is no inter-phase circuit in the three phases on the ac side of the primary side circuit, the method further includes: three resonance circuits respectively arranged on corresponding phase branches between the primary circuit and the transformer;

the resonance circuit includes: the first branch circuit is formed by connecting at least one second capacitor and at least one fourth inductor in series;

when the number of the fifth inductors is more than 1, all the fifth inductors are connected in series to form a second branch circuit;

one end of the first branch circuit and one end of the second branch circuit are connected with the AC side of the primary side circuit correspondingly;

the other end of the first branch circuit is connected with the homonymous end of the corresponding primary winding of the transformer;

the other end of the second branch circuit is connected with a synonym end of a corresponding primary winding of the transformer;

and the different-name ends of the primary windings of the transformer are connected.

Preferably, the excitation inductor is integrated in the transformer.

Preferably, only two groups of adjacent phases exist in the same-name ends of the three-phase primary winding of the transformer, and an interphase circuit arranged between two phases of each group of adjacent phases is an excitation inductor.

Preferably, the first secondary circuit and the second secondary circuit are a unidirectional rectifying circuit or an ac/dc bidirectional converting circuit.

Preferably, when no phase circuit exists in the different name end of the three-phase second secondary winding of the transformer, the three-phase second secondary winding of the transformer is correspondingly connected with the three phases on the alternating current side of the second secondary circuit through corresponding sixth inductors respectively.

Preferably, energy circulation is realized between the primary side circuit and the first secondary side circuit in a resonant frequency modulation mode.

Preferably, energy circulation is realized between the primary side circuit and the second secondary side circuit in a frequency modulation phase shift mode.

Preferably, the method further comprises the following steps: at least one third secondary side circuit;

and the three-phase third secondary winding of the transformer is directly or indirectly correspondingly connected with the three phases at the alternating current side of the third secondary circuit.

Preferably, the primary side circuit, the first secondary side circuit and the second secondary side circuit are all three-phase half-bridge conversion circuits.

Preferably, the method further comprises the following steps: the secondary side circuit comprises an input capacitor module arranged on the direct current side of the primary side circuit, a first output capacitor module arranged on the direct current side of the first secondary side circuit, and a second output capacitor module arranged on the direct current side of the second secondary side circuit.

Based on the three-phase LLC resonant direct-current converter provided by the embodiment of the invention, the three ports are provided, namely the primary circuit and the two secondary circuits are provided, wherein the primary circuit and the secondary circuits are both three-phase conversion circuits, and the three-phase conversion circuits are output in a staggered manner, so that the phase angle of a driving waveform of the three-phase conversion circuit in the three-phase LLC resonant direct-current converter is staggered by 120 degrees, and compared with the two-phase converter provided by the prior art, the ripple current on the bus side of the three-phase LLC resonant direct-current converter can be greatly offset; and energy circulation modes are different between the primary side circuit and the first secondary side circuit and between the primary side circuit and the second secondary side circuit, so that independent regulation of voltages of all ports of the three-phase LLC resonant direct-current converter is realized, that is, the frequency and amplitude of ripple current on the output side of each port can be respectively controlled, and the ripple current on the bus side of the three-phase LLC resonant direct-current converter is remarkably improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a single-phase LLC resonant converter in the prior art;

fig. 2 is a schematic structural diagram of a two-phase two-port LLC resonant converter in the prior art;

fig. 3 is a schematic structural diagram of a two-phase half-bridge three-port LLC resonant converter in the prior art;

fig. 4 is a schematic structural diagram of a two-phase full-bridge three-port LLC resonant converter in the prior art;

FIG. 5 is a graph of ripple current at the output side of a two-phase LLC resonant converter in the prior art;

fig. 6 is a schematic structural diagram of a three-phase LLC resonant dc-dc converter according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of another three-phase LLC resonant dc converter according to the embodiment of the present invention;

fig. 8 is a comparison curve diagram of the ripple current on the bus side of the three-phase LLC resonant dc converter according to the embodiment of the present invention and the ripple current on the output side of the two-phase LLC resonant converter in the prior art;

fig. 9a and 9b are schematic structural diagrams of two other three-phase LLC resonant dc converters according to another embodiment of the present invention;

fig. 10-13 are schematic structural diagrams of four other three-phase LLC resonant dc converters according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

In the prior art, as shown in fig. 1, a single-phase LLC resonant converter has a primary circuit including a bridge arm (shown as power switching transistors Q1 and Q2 in fig. 1) receiving an input dc bus voltage Vin, the primary circuit is connected to a primary side of a transformer T1 after being connected to a series resonant element (shown as Cr and Lr in fig. 1) through a bridge arm midpoint, and a secondary circuit includes diodes D1 and D2. Because the output filter circuit only has the filter capacitor Co, if the input dc bus voltage Vin is large, the output ripple is too large, and the service life of the battery is further reduced.

However, the structural schematic diagrams of the two-phase LLC resonant converter in the prior art are shown in fig. 2 to fig. 4, and the two-phase two-port converter in fig. 2 is taken as an example for explanation, it can be seen that, by adopting a series structure in which two LLC resonant converters output in staggered ways, under the same output power, the power converted in each way is only half of the original power, and the ripple current on the output side can be reduced, and the graph thereof is shown in fig. 5. It can be seen that the two-phase LLC resonant converter in the prior art can reduce the ripple current on the output side, but the effect is not ideal.

Therefore, the embodiment of the invention provides a three-phase LLC resonant dc converter to realize independent regulation of the voltage at each port, thereby significantly improving the ripple current at the bus side.

Fig. 6 shows a schematic structural diagram of the three-phase LLC resonant dc-dc converter, which includes: a primary side circuit 110, a first secondary side circuit 120, a second secondary side circuit 130, and a transformer 140; wherein:

the primary side circuit 110, the first secondary side circuit 120 and the second secondary side circuit 130 are all three-phase conversion circuits; the three phases at the ac side of the primary circuit 110 are directly or indirectly connected to the three-phase primary windings of the transformer 140; the three-phase first secondary winding of the transformer 140 is correspondingly connected with the third alternating current side of the first secondary circuit 120; the three-phase second secondary winding of the transformer 140 is directly or indirectly connected with the alternating current side three-phase of the second secondary circuit 130; energy circulation modes between the primary side circuit 110 and the first secondary side circuit 120 and between the primary side circuit 110 and the second secondary side circuit 130 are different, so that independent regulation of voltages at all ports of the three-phase LLC resonant direct current converter is realized; for example, one is a frequency modulation mode, and the other is a frequency modulation and equivalent duty ratio adjustment mode, that is, energy circulation is realized between the primary side circuit 110 and the first secondary side circuit 120 by adopting a resonance frequency modulation mode, and energy circulation is realized between the primary side circuit 110 and the second secondary side circuit 130 by adopting a frequency modulation phase shift mode.

As shown in fig. 6, the three-phase LLC resonant dc converter provided in the embodiment of the present invention is a three-phase three-port topology, where the primary side circuit 110 is provided with a first port V1, the first secondary side circuit 120 is provided with a second port V2, and the second secondary side circuit is provided with a third port V3, and in practical application, the topology with more than three ports can be expanded by providing at least one third secondary side circuit and a third secondary side winding of a transformer correspondingly connected thereto, and as long as the corresponding number of secondary side windings and secondary side circuits of the transformer are provided, the connection structure thereof can be analogized, and details are not repeated. Furthermore, the energy flow mode between the primary and secondary ports can be selected according to the specific application environment, and is not limited herein and is within the protection scope of the present application.

It should be noted that each primary winding of the transformer 130 is connected in parallel with a corresponding excitation inductor (e.g. L in fig. 6)_mA、L_mBAnd L_mCAs shown), and preferably, these excitation inductors may be integrated within the transformer 130. Primary side circuit 110 and first secondary side circuit120 and the second secondary side circuit 130 can all be three-phase half-bridge conversion circuits to, each circuit port both sides all have the capacitance module in parallel, that is, this three-phase LLC resonant dc converter still includes: an input capacitor module (shown as C1 in fig. 6) disposed on the dc side of the primary circuit 110, a first output capacitor module (shown as C2 in fig. 6) disposed on the dc side of the first secondary circuit 120, and a second output capacitor module (shown as C3 in fig. 6) disposed on the dc side of the second secondary circuit 130.

Specifically, the primary circuit 110 includes a plurality of switching tubes (as shown in S1-S6 in fig. 6), each of the arms in the primary circuit 110 is formed by connecting the switching tubes in series, for example, a first arm is formed by connecting a first switching tube S1 and a second switching tube S2 in series and connected in parallel with the input power V1, a drain of the first switching tube S1 is connected to an anode of the input power V1, and a source of the second switching tube S2 is connected to a cathode of the input power V1; a second bridge arm which is connected with the input power supply V1 in parallel and is formed by connecting a third switching tube S3 and a fourth switching tube S4 in series, wherein the drain electrode of the third switching tube S3 is connected with the anode of the input power supply V1, and the source electrode of the fourth switching tube S4 is connected with the cathode of the input power supply V1; and the third bridge arm is connected with the input power supply V1 in parallel and consists of a fifth switching tube S5 and a sixth switching tube S6 in series, wherein the drain electrode of the fifth switching tube S5 is connected with the anode of the input power supply V1, and the source electrode of the sixth switching tube S6 is connected with the cathode of the input power supply V1. Similarly, the first secondary circuit 120 includes three arms (as shown in S7-S12 in fig. 6) respectively connected in parallel with the second port V2, and the second secondary circuit 130 includes three arms (as shown in S13-S18) respectively connected in parallel with the third port V3, and the connection relationship of the switching tubes is the same as that of the switching tubes in the primary circuit 110, which is not described again. In practical application, each switch tube in the three-phase LLC resonant DC converter is connected with a parasitic diode in parallel.

In general, three phases on the ac side of the primary circuit 110 are indirectly connected to three-phase primary windings of the transformer 140, and a second three-phase secondary winding of the transformer 140 is also indirectly connected to an ac side of the second secondary circuit 130; at this time:

as shown in FIG. 6, the three-phase LLC resonant DC converterThe converter further comprises three resonant circuits 150, each arranged on a respective phase leg between the primary circuit 110 and the transformer 140. Specifically, as shown in fig. 6, the three resonant circuits 150 respectively disposed on the corresponding phase branches between the primary circuit 110 and the transformer 140 each include: at least one fifth inductor (L in FIG. 6)_m2A、L_m2BAnd L_m2CShown) and by at least one second capacitor (e.g., C in fig. 6)_r1A、C_r1BAnd C_r1C) And at least one fourth inductor (e.g. L in FIG. 6)_r1A、L_r1BAnd L_r1CShown) a first branch formed in series; when the number of the fifth inductors is more than 1, all the fifth inductors are connected in series to form a second branch circuit; one end of the first branch circuit and one end of the second branch circuit are connected with the corresponding phase of the alternating current side of the primary side circuit 110; the other end of the first branch is connected with the dotted end of the corresponding primary winding of the transformer 140; the other end of the second branch is connected to the synonym end of the corresponding primary winding of the transformer 140; the synonym terminals of the primary windings of the transformer 140 are connected. It should be noted that fig. 6 only illustrates one of all the inductors, and in fact, the number of the fifth inductor, the second capacitor, and the fourth inductor in each resonant circuit 150 is determined by a skilled person according to practical applications and is within the protection scope of the embodiments of the present invention.

Meanwhile, the three-phase second secondary winding of the transformer 140 passes through the corresponding sixth inductor (e.g. L in fig. 6 or 7)_2A、L_2BAnd L_2CShown) and correspondingly connected to the three phases of the ac side of the second secondary circuit 130 to match the on/off of each switching tube in the second secondary circuit 130, so as to realize that the energy circulation between the primary circuit 110 and the second secondary circuit 130 is completed by frequency modulation and phase shift.

Therefore, the three-phase LLC resonant dc converter provided in the embodiments of the present invention exhibits a three-phase three-port topology, that is, the primary circuit 110, the first secondary circuit 120, and the second secondary circuit 130 are all three-phase conversion circuits, and the three-phase conversion circuits output in a staggered manner, so that the waveform phase angle of the three-phase conversion circuit driving in the three-phase LLC resonant dc converter is staggered by 120 degrees, and compared with the two-phase converter provided in the prior art, the ripple current on the bus side of the three-phase LLC resonant dc converter can be greatly offset; and between the original side circuit and the first secondary side circuit and between the primary side circuit and the second secondary side circuit, energy circulation modes are different, so that independent adjustment of voltage of each port of the three-phase LLC resonant direct-current converter is achieved, the frequency and amplitude of ripple current of the output side of each port can be controlled respectively, and ripple current of the bus side is improved remarkably.

The ripple current ratio between the two is shown in fig. 8, where Y2(t), i.e. the solid line, represents the output side ripple current of the two-phase converter in the prior art, and Y3(t), i.e. the dotted line, represents the bus side ripple current of the three-phase LLC resonant dc converter provided in the embodiment of the present invention.

Compared with the converter provided by the prior art, the three-phase LLC resonant direct-current converter provided by the embodiment of the invention is provided with the first interphase circuit 210, and the bidirectional boosting can be realized by adding fewer resonant elements in a reverse working mode in which the secondary side transmits energy to the primary side, so that the system volume and the cost are reduced.

On the basis of the above embodiments, in order to further reduce the system volume and cost, at least one of the three phases on the ac side of the primary circuit, the different name ends of the three-phase primary winding of the transformer and the three-phase secondary winding of the transformer may be provided, at least two groups of adjacent phases exist, and at least one interphase circuit is provided between two phases of each group of adjacent phases to realize corresponding function multiplexing during power transmission. The concrete conditions are divided into the following cases:

(1) at least two groups of adjacent phases exist in the three phases on the alternating current side of the primary side circuit, an interphase circuit is arranged between two phases of each group of adjacent phases, and the interphase circuit is a first interphase circuit.

Under the condition that the three phases at the ac side of the primary side circuit 110 are correspondingly connected to the primary side of the transformer 140 through the corresponding resonant circuits, three fifth inductors in the three resonant circuits in fig. 6 may be modified to reduce the system size and cost, and at this time, the three fifth inductors are connected to the primary side of the transformer 140 through the corresponding resonant circuitsThe resonant circuits 150 are respectively disposed on corresponding branches between the primary circuit 110 and a primary midpoint of the transformer 140, where the primary midpoint refers to a connection point (e.g., N1 shown in fig. 7) of the different name end of each primary winding; that is, a resonant circuit 150 and a corresponding primary winding are connected in series on each phase branch between the ac side of the primary circuit 110 and the primary midpoint of the transformer 140; when all or part of the components in the resonant circuit 150 are disposed between the ac side of the primary circuit 110 and the corresponding primary winding of the transformer 140, the ac side of the primary circuit 110 is indirectly connected to the primary side of the transformer 140; when all of the components of the resonant circuit 150 are disposed between the synonym terminal of the corresponding primary winding of the transformer 140 and the primary midpoint N1, the ac side of the primary circuit 110 is directly connected to the primary side of the transformer 140. In the embodiment of the present invention, the ac side of the primary side circuit 110 is indirectly connected to the primary side of the transformer 140, and meanwhile, at least two groups of adjacent phases in the three phases of the ac side of the primary side circuit 110 are provided with the first inter-phase circuit 210 between two phases of each group of adjacent phases, and the schematic structural diagram is shown in fig. 7; and, each of the resonance circuits 150 thereof is modified to include: at least one first capacitor and at least one second inductor; the first capacitors, the second inductors and the corresponding primary windings in the transformer 140 are connected in series, the series connection sequence is not limited, one end of the series connection is connected with the corresponding phase of the alternating current side of the primary circuit, and the other end of the series connection is connected with the middle point of the primary side of the transformer. FIG. 7 shows a first capacitor and a second inductor (L in FIG. 7)_r1AAnd C_r1A、 L_r1BAnd C_r1BAnd L_r1CAnd C_r1CShown) are shown as an example, and the structures of the first capacitors and the second inductors in series with other numbers are similar to this and are not described again. The setting method of the resonant circuits 150 may be selected according to specific situations, and it is only necessary to realize that each resonant circuit 150 is connected in series with the primary winding of the transformer 140, which is within the protection scope of the embodiments of the present invention.

In practice, each first inter-phase circuit 210 includes: first inductor (e.g. L in FIG. 7)_m2AShown) having a first secondary circuit 120 and a second secondary circuitThe circuit 130 is an ac/dc bidirectional conversion circuit (as shown in fig. 7), and in this case, the three-phase LLC resonant dc converter is a bidirectional converter (as shown in fig. 7), so that the three-phase LLC resonant dc converter can not only operate in a forward operation mode when energy is transmitted from the primary side to the secondary side, but also implement corresponding function multiplexing during power transmission, that is: the multiplexing of the resonance function can be realized in a reverse working mode when energy is transmitted from the secondary side to the primary side, that is, when energy is transmitted from the first secondary side circuit 120 and the second secondary side circuit 130 to the primary side circuit 110; specifically, when the excitation inductance in transformer 140 does not participate in resonance, the second inductance and the first capacitance connected in series in three resonant circuits 150 and the first inductance in first inter-phase circuit 210 are used together as resonant elements, so as to avoid that the circuit is in an LC resonance state and reverse boosting cannot be performed. It should be noted that fig. 7 is only one arrangement manner of the first inter-phase circuit 210, and it may be arranged between two phases of any two sets of adjacent phases, or three sets of adjacent phases are all provided with the first inter-phase circuit 210, and it is determined by a skilled person according to practical application situations and is within the protection scope of the embodiment of the present invention.

In this case, in the three-phase LLC resonant dc-dc converter, the three-phase second secondary windings of the transformer 140 may be indirectly connected to the ac-side three-phase of the second secondary circuit 130 through corresponding inductors, as shown in fig. 7.

(2) At least two groups of adjacent phases in different name ends of a three-phase primary winding of the transformer are provided, an interphase circuit is arranged between two phases of each group of adjacent phases, and the interphase circuit is a second interphase circuit.

In this case, the three-phase LLC resonant dc converter may be a bidirectional converter (as shown in fig. 9 a) or a unidirectional converter (as shown in fig. 12), that is, the first secondary circuit 120 and the second secondary circuit 130 may be ac/dc bidirectional conversion circuits (as shown in fig. 9 a) or may be unidirectional rectifier circuits such as diode rectifier bridges (as shown in 120 and 130 in fig. 12).

In addition, the three-phase LLC resonant dc converter does not add any element, but only improves the original three resonant circuits in fig. 6, and multiplexes the inductors and capacitors in the resonant circuits, i.e., two or three second phase-to-phase circuits are respectively utilized to realize the power transmission of the unidirectional converter and the forward working mode or the reverse working mode of the bidirectional converter, and when the bidirectional converter is in the reverse working mode, the effect of realizing the reverse boost as described above can be achieved, and the circuit volume and the cost are significantly reduced. At this time, the three phases on the ac side of the primary circuit 110 are directly connected to the three-phase primary windings of the transformer 140.

Preferably, only two sets of adjacent phases exist in the different-name terminals of the three-phase primary windings of the transformer 140, and the second interphase circuit 310 is arranged between two phases of each set of adjacent phases. It can be seen that, as shown in fig. 9a or fig. 12, the three-phase LLC resonant dc converter does not add any component, but improves the original three resonant circuits, and its adjacent phases multiplex the inductance and capacitance in the resonant circuit, thereby reducing one resonant circuit, and the circuit size and cost are lower.

As shown in fig. 9a or fig. 12, the second phase circuit 310 includes: at least one second capacitor (C in FIG. 9a or FIG. 12) connected in series_r1AAnd C_r1BShown) and at least one third inductor (e.g., L in fig. 9a or 12)_r1AAnd L_r1BShown). The second inter-phase circuit 310 may be formed by connecting a plurality of third inductors in series with a plurality of second capacitors, and the series connection sequence may be set arbitrarily, which is within the protection scope of the embodiments of the present invention and will not be described again.

In this case, in the three-phase LLC resonant dc-dc converter, the three-phase second secondary windings of the transformer 140 can be indirectly connected to the ac side three-phase of the second secondary circuit 130 via corresponding inductors, as shown in fig. 9 a.

(3) At least two groups of adjacent phases exist in the three phases at the alternating current side of the primary side circuit, and a first interphase circuit is arranged between two phases of each group of adjacent phases; and at least two groups of adjacent phases in different name ends of the three-phase primary winding of the transformer, wherein a second inter-phase circuit is arranged between two phases of each group of adjacent phases.

At this time, the three phases on the ac side of the primary circuit 110 are directly connected to the three-phase primary windings of the transformer 140. The specific structure of the method can be seen in fig. 9b, which can be regarded as the combined application of the cases (1) and (2), and the description thereof is omitted here for brevity.

In this case, in the three-phase LLC resonant dc-dc converter, the three-phase second secondary windings of the transformer 140 can be indirectly connected to the ac-side three-phase of the second secondary circuit 130 via corresponding inductors, as shown in fig. 9 b.

(4) At least two groups of adjacent phases exist in the different name ends of the three-phase second secondary winding of the transformer, an interphase circuit is arranged between two phases of each group of adjacent phases, and the interphase circuit is a third interphase circuit.

Similarly, as described in the case (2), the three-phase LLC resonant dc converter may be a bidirectional converter (as shown in fig. 10) or a unidirectional converter (not shown), that is, the first secondary circuit 120 and the second secondary circuit 130 may be ac/dc bidirectional conversion circuits (as shown in fig. 10) or unidirectional rectifier circuits, such as diode rectifier bridges (similar to 120 and 130 in fig. 12).

Preferably, to further save cost, three phase-shifting inductors (i.e., L in fig. 6) in the above-described embodiment can be multiplexed_2A、L_2BAnd L_2C) The three phase-shifting inductors are changed into two phase-shifting inductors, and the structural schematic diagram of the phase-shifting inductors is shown in fig. 10, specifically:

at this time, three groups of adjacent phases exist in the different name ends of the three-phase second secondary winding of the transformer 140, two groups (as shown in fig. 10) or three groups (not shown) of adjacent phases are arbitrarily selected from the three groups of adjacent phases, a third inter-phase circuit 410 is disposed between two phases of each group of adjacent phases, and the third inter-phase circuit 410 includes a third inductor (as L in fig. 10)_2AAnd L_2BAs shown), preferably, as shown in fig. 10, only two sets of adjacent phases exist in the different-name ends of the three-phase second secondary winding of the transformer 140, and a third inter-phase circuit 410 is disposed between two phases of each set of adjacent phases, and the function of the third inter-phase circuit is the same as that of the three phase-shifting inductors of the above-mentioned embodiment, that is, the multiplexing of the phase-shifting function in the forward operation mode when energy is transmitted from the primary side to the corresponding secondary side is realized.

At this time, the three-phase LLC resonant dc converter multiplexes the three phase-shift inductors in the above-described embodiment, and can realize independent regulation of the voltage of each port in the above-described embodiment as well, and simultaneously, the ripple current on the bus side of the three-phase LLC resonant dc converter is largely cancelled out, so that the purpose of significant improvement is achieved, and the system cost and volume are reduced.

In this case, the resonant circuit between the ac side of the primary side circuit and the primary side of the transformer may be set as shown in fig. 10, that is, an indirect connection manner is adopted, or the above three cases may be referred to, that is, the case (4) may be applied in combination with any one of the cases (1) to (3), which is referred to in the above description, and details are not repeated.

In general, in the above cases, the primary windings of the transformer 130 are respectively connected in parallel with corresponding excitation inductors (e.g. L in fig. 6)_mA、L_mBAnd L_mCAs shown), and preferably, these excitation inductors may be integrated within the transformer 130. In contrast, the following case (5) is also a case.

(5) In the same-name end of the three-phase primary winding of the transformer, only two groups of adjacent phases exist, and an interphase circuit arranged between two phases of each group of adjacent phases is an excitation inductor.

That is, in the case where the transformer 140 does not integrate the exciting inductance, an external exciting inductance (L as shown in fig. 13) may be used_mABAnd L_mBC) Multiplexing, as shown in fig. 13, also enables reduction in components, size and cost of the unidirectional converter or the bidirectional converter.

In practical application, the case (5) of multiplexing the excitation inductance may be applied in combination with any one of the cases (1) to (4) or fig. 6 provided in the above embodiments, and will not be described again.

It should be noted that, in the topologies provided in the above cases (1) and (3), since the first inter-phase circuit 210 is provided, when the three-phase LLC resonant dc-dc converter is in the forward operation mode, the first inductor in the first inter-phase circuit 210 still flows current although not participating in resonance, and further generates loss. Therefore, the primary circuit 110 and the secondary circuit 120 of the three-phase LLC resonant dc converter are both ac/dc bidirectional conversion circuits, i.e., the three-phase LLC resonant dc converter is a bidirectional converter, and can be applied to energy bidirectional flow occasions such as high-power charging piles, energy storage and the like, so as to realize the improvement of voltage gain of the three-phase LLC resonant dc converter in a reverse working mode and enhance the gain adjustment function. Other topologies, in which the first interphase circuit 210 is not provided, may be applied to a unidirectional converter or a bidirectional converter.

The rest of the principle is the same as the above embodiments, and is not described in detail here.

On the basis of the foregoing embodiments, in a topology in which the first inter-phase circuit 210 is disposed, that is, in case (1) or case (3) in the foregoing embodiments, in order to further reduce loss and improve system efficiency, an embodiment of the present invention further provides the following topology, a schematic structural diagram of which is shown in fig. 11 (which is shown as an example on the basis of fig. 7), where:

the first inter-phase circuit 210 further includes: a switch connected in series with the first inductor (as shown at S19 in fig. 11).

According to the three-phase LLC resonant direct-current converter provided by the embodiment of the invention, the switches are arranged in the first inter-phase circuit 210, the switches are controlled to be turned on and off when the energy of the three-phase LLC resonant direct-current converter is transmitted from the primary side to the secondary side, and the switches are controlled to be turned on when the energy of the three-phase LLC resonant direct-current converter is transmitted from the secondary side to the primary side, so that the loss is avoided, and the system efficiency is improved.

It should be noted that the first interphase circuit 210, the resonant circuit 150, the multiplexing of the excitation inductor, and the arrangement of the second interphase circuit 310 or the third interphase circuit 410 according to the embodiment of the present invention may be freely combined according to actual needs, and are not limited to the above ones, and are not listed.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on different points from other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only schematic, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the elements and algorithm steps of the various embodiments described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various example components and steps have been described above generally in terms of their functionality in order to clearly illustrate their interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-phase LLC resonant dc converter, comprising: the transformer comprises a primary side circuit, a first secondary side circuit, a second secondary side circuit and a transformer; wherein:

the three phases at the alternating current side of the primary side circuit are directly or indirectly connected with the three-phase primary side windings of the transformer correspondingly;

the three-phase first secondary winding of the transformer is correspondingly connected with the three phases at the alternating current side of the first secondary circuit;

2. The three-phase LLC resonant dc converter according to claim 1, wherein at least one of the synonyms of the three-phase ac side of the primary circuit, the three-phase primary winding of the transformer, and the second secondary winding of the three-phase of the transformer has at least two sets of adjacent phases, and at least one interphase circuit is provided between two phases of each set of adjacent phases, so as to implement corresponding function multiplexing during power transmission.

3. The three-phase LLC resonant dc converter according to claim 2, wherein at least two sets of adjacent phases exist in the three phases on the ac side of the primary circuit, and the inter-phase circuit provided between two phases of each set of adjacent phases is the first inter-phase circuit.

4. A three-phase LLC resonant dc-to-dc converter according to claim 3, wherein said first phase-to-phase circuit comprises: a first inductor.

5. The three-phase LLC resonant DC converter according to claim 4, wherein said first phase-to-phase circuit further comprises: a switch connected in series with the first inductor.

6. The three-phase LLC resonant DC converter according to claim 3, further comprising: and the three resonant circuits are respectively arranged on corresponding phase branches between the primary side circuit and the midpoint of the primary side of the transformer.

7. The three-phase LLC resonant DC converter according to claim 6, wherein said resonant circuit comprises: at least one first capacitor and at least one second inductor;

8. A three-phase LLC resonant dc converter as claimed in claim 3, wherein the primary windings of the transformers are connected in parallel with respective exciting inductances.

9. A three-phase LLC resonant DC converter according to any one of claims 3 to 8, wherein said first and second secondary circuits are AC/DC bidirectional conversion circuits.

10. The three-phase LLC resonant dc converter according to claim 2, wherein at least two sets of adjacent phases of the synonym terminals of the three-phase primary windings of the transformer are provided, and the inter-phase circuit provided between two phases of each set of adjacent phases is a second inter-phase circuit.

11. The three-phase LLC resonant dc converter according to claim 10, wherein there are only two sets of adjacent phases in the synonym terminals of the three-phase primary windings of the transformer, and the second inter-phase circuit is provided between two phases of each set of adjacent phases.

12. The three-phase LLC resonant dc converter of claim 10, wherein said second phase-to-phase circuit comprises: at least one second capacitor and at least one third inductor connected in series.

13. The three-phase LLC resonant dc converter as claimed in claim 10, wherein each primary winding of the transformer is connected in parallel with a corresponding magnetizing inductor.

14. The three-phase LLC resonant dc converter according to claim 2, wherein there are at least two sets of adjacent phases at different ends of the three-phase second secondary winding of the transformer, and an inter-phase circuit provided between two phases of each set of adjacent phases is a third inter-phase circuit, so as to implement multiplexing of phase-shifting function in a forward operating mode when energy is transmitted from the primary side to the corresponding secondary side.

15. The three-phase LLC resonant dc converter according to claim 14, wherein there are only two sets of adjacent phases in the synonym terminals of the second secondary windings of the three phases of the transformer, and one said third inter-phase circuit is provided between two phases of each set of adjacent phases.

16. The three-phase LLC resonant dc converter of claim 14, wherein said third inter-phase circuit comprises: and a third inductor.

17. The three-phase LLC resonant dc converter of claim 14, wherein, in the absence of an inter-phase circuit in three phases on the ac side of the primary circuit, further comprising: three resonance circuits respectively arranged on corresponding phase branches between the primary circuit and the transformer;

18. The three-phase LLC resonant dc converter as claimed in claim 14, wherein each primary winding of the transformer is connected in parallel with a corresponding magnetizing inductance.

19. A three-phase LLC resonant dc-to-dc converter according to claim 8, 13 or 18, characterized in that the excitation inductance is integrated in the transformer.

20. The three-phase LLC resonant dc converter according to claim 1, wherein only two sets of adjacent phases exist in the same-name ends of the three-phase primary windings of the transformer, and an inter-phase circuit provided between two phases of each set of adjacent phases is an excitation inductor.

21. A three-phase LLC resonant dc converter according to any of claims 10-18 and 20, wherein the first secondary circuit and the second secondary circuit are unidirectional rectifying circuits or ac/dc bidirectional converting circuits.

22. A three-phase LLC resonant dc-to-dc converter according to any of claims 1-8, 10-18 and 20, characterized in that, when there is no phase-to-phase circuit in the different ends of the three-phase second secondary windings of the transformer, the three-phase second secondary windings of the transformer are correspondingly connected to the three phases on the ac side of the second secondary circuit through respective sixth inductors.

23. A three-phase LLC resonant dc-to-dc converter as claimed in any one of claims 1-8, 10-18 and 20, characterized in that energy flow between said primary and said first secondary circuit is achieved by means of resonant frequency modulation.

24. A three-phase LLC resonant dc-to-dc converter according to any of claims 1-8, 10-18 and 20, characterized in that energy is circulated between the primary circuit and the second secondary circuit by means of frequency modulation and phase shift.

25. A three-phase LLC resonant dc-to-dc converter according to any of claims 1-8, 10-18, 20, further comprising: at least one third secondary side circuit;

26. A three-phase LLC resonant dc-to-dc converter according to any of claims 1-8, 10-18, 20, characterized in that the primary circuit, the first secondary circuit and the second secondary circuit are three-phase half-bridge converter circuits.

27. A three-phase LLC resonant dc-to-dc converter according to any of claims 1-8, 10-18, 20, further comprising: the secondary side circuit comprises an input capacitor module arranged on the direct current side of the primary side circuit, a first output capacitor module arranged on the direct current side of the first secondary side circuit, and a second output capacitor module arranged on the direct current side of the second secondary side circuit.