A three-phase resonant converter

Abstract

The application discloses a three-phase resonant converter, which comprises a three-phase transformer, a three-phase inverter circuit and a two-phase resonant branch, wherein the three-phase transformer comprises first to third primary windings and first to third secondary windings; the three-phase inverter circuit comprises first to third bridge arms, and each bridge arm is connected between a first input end and a second input end; the connection point of two switch tubes of the second bridge arm is connected with one end of the second primary winding; the two-phase resonant branch comprises first and second resonant branches, and each resonant branch is connected between the connection point of two switch tubes of the first bridge arm and one end of the first primary winding or between the connection point of two switch tubes of the third bridge arm and one end of the third primary winding; and the three-phase resonant converter further comprises a secondary rectifier circuit; wherein one end of the first, second and third primary windings and one end of the first, second and third secondary windings are homonymous ends; and the other end of the first, second and third primary windings and the other end of the first, second and third secondary windings are heteronymous ends. The three-phase resonant converter adopts the two-phase resonant branch, thereby reducing the complexity of the topology, reducing resonant components and lowering the design cost.

Description

Technical Field

[0001] This invention relates to three-phase converters, and more particularly to a three-phase resonant converter. Background Technology

[0002] With the development of new energy technologies, the corresponding power level converters have also developed rapidly. In particular, in applications such as photovoltaics, wind power, and electric vehicle on-board chargers, the required power level of power level converters is gradually increasing, and the design requirements for power electronic converters are becoming more and more stringent.

[0003] Resonant DC-DC converters are popular in the new energy field due to their soft-switching, high efficiency, and high power density. Typical resonant converters are single-phase half-bridge resonant converters and single-phase full-bridge resonant converters. These types of converters have large output current ripple and limited power transmission capability, making them unsuitable for medium and high power applications.

[0004] To reduce output current ripple and improve the power transmission capability of power stage converters, scholars Chao Fei, Fred C. Lee, and others studied three-phase LLC resonant converters with star (Y)-star (Y) connections, three-phase LLC resonant converters with delta (△)-delta (△) connections, three-phase LLC resonant converters with capacitor delta (△)-star (Y)-star (Y) connections, and other three-phase interleaved LLC resonant converter topologies with delta (△) / star (Y) combinations in their published paper, *High-Frequency Three-Phase Interleaved LLC Resonant Converter With GaN Devices and Integrated Planar Magnetics*.

[0005] However, the three-phase resonant converters studied by the aforementioned scholars have complex topologies, all of which include three-phase inverter circuits, three-phase resonant branches, three-phase transformers, and three-phase rectifier circuits. The three-phase resonant converter topologies have a large number of switching devices and magnetic devices, which increases the circuit design cost, reduces the power density, and makes the overall design complex. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a three-phase resonant converter that reduces the complexity and design cost of the three-phase resonant topology and improves the power density.

[0007] To solve the above-mentioned technical problems, the present invention provides the following embodiment of a three-phase resonant converter:

[0008] A three-phase resonant converter, comprising:

[0009] First input terminal, second input terminal, first output terminal, and second output terminal;

[0010] A three-phase transformer includes a first primary winding, a second primary winding, a third primary winding, a first secondary winding, a second secondary winding, and a third secondary winding;

[0011] The three-phase inverter circuit includes a first bridge arm, a second bridge arm, and a third bridge arm, all of which are connected between the first input terminal and the second input terminal. Each bridge arm includes two series-connected switching transistors. The connection point of the two switching transistors in the second bridge arm is connected to one end of the second primary winding.

[0012] The two-phase resonant branch includes a first resonant branch and a second resonant branch. The first resonant branch is connected between the connection point of the two switching transistors of the first bridge arm and one end of the first primary winding. The second resonant branch is connected between the connection point of the two switching transistors of the third bridge arm and one end of the third primary winding. Each resonant branch includes two resonant capacitors and resonant inductors connected in series.

[0013] The secondary rectifier circuit is used to convert the AC voltage transmitted by the first secondary winding, the second secondary winding and the third secondary winding into DC voltage and output it through the first output terminal and the second output terminal;

[0014] Wherein, one end of the first primary winding, one end of the second primary winding, one end of the third primary winding, one end of the first secondary winding, one end of the second secondary winding, and one end of the third secondary winding are all the same name; the other ends of the first primary winding, the second primary winding, the third primary winding, the first secondary winding, the second secondary winding, and the third secondary winding are all different name.

[0015] Preferably, the secondary circuit is a three-phase rectifier circuit, including a first rectifier circuit, a second rectifier circuit, and a third rectifier circuit, all connected between the first output terminal and the second output terminal of the three-phase resonant converter. Each rectifier circuit includes two rectifier tubes connected in series. The connection point of the two rectifier tubes in the first rectifier circuit is connected to one end of the first primary winding. The connection point of the two rectifier tubes in the second rectifier circuit is connected to one end of the second primary winding. The connection point of the two rectifier tubes in the third rectifier circuit is connected to one end of the third primary winding.

[0016] Furthermore, the other ends of the first primary winding, the second primary winding, and the third primary winding are connected together, thereby forming a star connection structure for each primary winding of the three-phase transformer; the other ends of the first secondary winding, the second secondary winding, and the third secondary winding are connected together, thereby forming a star connection structure for each secondary winding of the three-phase transformer.

[0017] Furthermore, the other ends of the first primary winding, the second primary winding, and the third primary winding are connected together, thereby forming a star connection structure among the primary windings of the three-phase transformer; the other end of the first secondary winding is connected to one end of the second secondary winding, the other end of the second secondary winding is connected to one end of the third secondary winding, and the other end of the third secondary winding is connected to one end of the first secondary winding, thereby forming a delta connection structure among the secondary windings of the three-phase transformer.

[0018] Furthermore, the other end of the first primary winding is connected to one end of the second primary winding, the other end of the second primary winding is connected to one end of the third primary winding, and the other end of the third primary winding is connected to one end of the first primary winding, thereby forming a delta connection structure among the primary windings of the three-phase transformer; the other end of the first secondary winding is connected to one end of the second secondary winding, the other end of the second secondary winding is connected to one end of the third secondary winding, and the other end of the third secondary winding is connected to one end of the first secondary winding, thereby forming a delta connection structure among the secondary windings of the three-phase transformer.

[0019] Furthermore, the other end of the first primary winding is connected to one end of the second primary winding, the other end of the second primary winding is connected to one end of the third primary winding, and the other end of the third primary winding is connected to one end of the first primary winding, thereby forming a delta connection structure among the primary windings of the three-phase transformer; the other ends of the first secondary winding, the second secondary winding, and the third secondary winding are connected together, thereby forming a star connection structure among the secondary windings of the three-phase transformer.

[0020] Preferably, the secondary circuit is a three-phase full-bridge parallel rectifier circuit, including a first rectifier bridge circuit, a second rectifier bridge circuit, and a third rectifier bridge circuit. The first AC input terminal of the first rectifier bridge circuit is connected to one end of the first secondary winding, and the second AC input terminal of the first rectifier bridge circuit is connected to the other end of the first secondary winding. The first AC input terminal of the second rectifier bridge circuit is connected to one end of the second secondary winding, and the second AC input terminal of the second rectifier bridge circuit is connected to the other end of the second secondary winding. The first AC input terminal of the third rectifier bridge circuit is connected to one end of the third secondary winding, and the second AC input terminal of the third rectifier bridge circuit is connected to the other end of the third secondary winding. The positive output terminals of the first, second, and third rectifier bridge circuits are simultaneously connected to the first output terminal of the three-phase resonant converter. The negative output terminals of the first, second, and third rectifier bridge circuits are simultaneously connected to the second output terminal of the three-phase resonant converter.

[0021] Furthermore, the drive pulses of the two switches in the first bridge arm are complementary, and their duty cycles are both 50% after ignoring the dead time; the drive pulses of the two switches in the second bridge arm are complementary, and their duty cycles are both 50% after ignoring the dead time; the drive pulses of the two switches in the third bridge arm are complementary, and their duty cycles are both 50% after ignoring the dead time; and the phases of the drive pulses of the upper switches in the first bridge arm, the second bridge arm, and the third bridge arm are sequentially 120° apart; the phases of the drive pulses of the lower switches in the first bridge arm, the second bridge arm, and the third bridge arm are sequentially 120° apart.

[0022] Furthermore, the resonant frequencies of the first resonant branch and the second resonant branch are the same, and the operating frequency of the three-phase resonant converter is the resonant frequency of the first resonant branch or the resonant frequency of the second resonant branch.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. Compared with the three-phase resonant converter topology disclosed in the existing literature High-Frequency Three-Phase Interleaved LLC Resonant Converter With GaN Devices and Integrated PlanarMagnetics, the three-phase resonant converter of the present invention reduces one resonant branch, thereby reducing the complexity and design cost of the three-phase circuit;

[0025] 2. The three-phase resonant converter of the present invention retains the advantage that the traditional resonant converter operates in the inductive operating region and the input voltage of the resonant cavity leads the resonant current, thus possessing soft-switching characteristics and improving conversion efficiency.

[0026] 3. Some embodiments of the three-phase resonant converter of the present invention employ 120° phase-shifted interleaved control, which can reduce output current ripple, optimize the design of filter capacitors, and reduce the number and size of filter capacitors;

[0027] 4. Some embodiments of the three-phase resonant converter of the present invention: The three-phase transformer is configured in a star or delta connection, which has the characteristic of natural current sharing between phases, and can improve the stability of the whole machine operation. Attached Figure Description

[0028] Figure 1 This refers to the three-phase resonant converter with a star (Y)-star (Y) connection as disclosed in the literature;

[0029] Figure 2 This invention discloses a specific circuit for a three-phase resonant converter.

[0030] Figure 3 for Figure 2 The soft-switching waveform of the three-phase resonant converter after adopting the interleaved control method with a phase difference of 120°;

[0031] Figure 4 for Figure 2 Output current waveform of a three-phase resonant converter using an interleaved control method with a phase difference of 120°;

[0032] Figure 5 for Figure 2 The output current waveforms of each phase under resonance parameter deviation after the three-phase resonant converter adopts the interleaved control method with a phase difference of 120°;

[0033] Figure 6 This is a topology diagram of the three-phase transformers of the three-phase resonant converter described in this invention, configured as a star (Y)-delta (△) connection.

[0034] Figure 7 This is a topological diagram showing the three-phase transformers of a three-phase resonant converter according to the present invention forming a triangle (△)-triangle (△) connection.

[0035] Figure 8 The diagram shows the topology of the three-phase transformers of the three-phase resonant converter described in this invention, which are configured as a delta (△) to a star (Y) connection.

[0036] Figure 9 This is another specific circuit of a three-phase resonant converter disclosed in this invention. Detailed Implementation

[0037] The technical solution of the present invention will now be described with reference to the accompanying drawings and embodiments to enable those skilled in the art to better understand the invention. However, the specific implementation of the technical solution of the present invention is not limited thereto.

[0038] like Figure 1 The diagram shows the topology of a three-phase LLC resonant converter with a star (Y)-star (Y) connection, as disclosed in the paper "High-Frequency Three-Phase Interleaved LLC Resonant Converter With GaN Devices and Integrated Planar Magnetics". This three-phase resonant converter has a complex topology, including a three-phase inverter circuit, a three-phase resonant branch, a three-phase transformer, a three-phase rectifier circuit, and an output filter circuit. The primary and secondary sides of the three-phase transformer form a star (Y)-star (Y) connection. The complex structure of this three-phase resonant converter, with its numerous switching devices, resonant devices, and magnetic devices, results in a complex and bulky overall structure, which is detrimental to improving the power density of medium- and high-power power supply products.

[0039] The three-phase resonant converter provided in this embodiment of the invention includes:

[0040] First input terminal, second input terminal, first output terminal, and second output terminal;

[0041] A three-phase transformer includes a first primary winding, a second primary winding, a third primary winding, a first secondary winding, a second secondary winding, and a third secondary winding;

[0042] The three-phase inverter circuit includes a first bridge arm, a second bridge arm, and a third bridge arm, all of which are connected between the first input terminal and the second input terminal. Each bridge arm includes two series-connected switching transistors. The connection point of the two switching transistors in the second bridge arm is connected to one end of the second primary winding.

[0043] The two-phase resonant branch includes a first resonant branch and a second resonant branch. The first resonant branch is connected between the connection point of the two switching transistors of the first bridge arm and one end of the first primary winding. The second resonant branch is connected between the connection point of the two switching transistors of the third bridge arm and one end of the third primary winding. Each resonant branch includes two resonant capacitors and resonant inductors connected in series.

[0044] The secondary rectifier circuit is used to convert the AC voltage transmitted by the first secondary winding, the second secondary winding and the third secondary winding into DC voltage and then output it through the first output terminal and the second output terminal.

[0045] Among them, one end of the first primary winding, one end of the second primary winding, one end of the third primary winding, one end of the first secondary winding, one end of the second secondary winding, and one end of the third secondary winding are the same name ends; the other ends of the first primary winding, the second primary winding, the third primary winding, the first secondary winding, the second secondary winding, and the third secondary winding are different name ends.

[0046] like Figure 2 The diagram shows a specific circuit of a three-phase resonant converter disclosed in this invention. Figure 2 The three-phase resonant converter only requires two resonant branches to realize a three-phase resonant converter. Compared with the existing star (Y)-star (Y) connected three-phase resonant converter in Figure (1), Figure 2 The three-phase resonant converter simplifies the three-phase LLC resonant topology of star (Y)-star (Y) connection, reduces one resonant branch, can reduce the circuit design cost of the power system, and improve power density;

[0047] like Figure 2 As shown, the three-phase resonant converter includes: a first input terminal, a second input terminal, a first output terminal, and a second output terminal; as well as a DC input source I, a three-phase inverter circuit II, a two-phase resonant branch III, a three-phase transformer IV, a three-phase rectifier circuit V, and an output filter circuit VI;

[0048] In practical implementation, its structure is as follows:

[0049] The three-phase inverter circuit II includes a first bridge arm, a second bridge arm and a third bridge arm, wherein the first bridge arm includes a first switch S1 and a second switch S2, the second bridge arm includes a third switch S3 and a fourth switch S4, and the third bridge arm includes a fifth switch S5 and a sixth switch S6.

[0050] Two-phase resonant branch III includes a first resonant branch and a second resonant branch, wherein the first resonant branch includes a first resonant capacitor C. r1 First resonant inductor L r1 and the first magnetizing inductor L m1 The second resonant branch includes the third resonant capacitor C. r3 The third resonant inductor L r3 and the third magnetizing inductor L m3 ;

[0051] The three-phase transformer IV includes a first transformer T1, a second transformer T2, and a third transformer T3. The first transformer T1 includes a first primary winding, a first secondary winding, and a first magnetizing inductor L. m1 The second transformer T2 includes a second primary winding, a second secondary winding, and a second magnetizing inductor L. m2The third transformer T3 includes a third primary winding, a third secondary winding, and a third magnetizing inductor L. m3 ;

[0052] The three-phase rectifier circuit V includes a first rectifier circuit, a second rectifier circuit, and a third rectifier circuit. The first rectifier circuit includes a first rectifier diode D1 and a second rectifier diode D2. The second rectifier circuit includes a third rectifier diode D3 and a fourth rectifier diode D4. The third rectifier circuit includes a fifth rectifier diode D5 and a sixth rectifier diode D6.

[0053] Output filter circuit VI includes output filter capacitor C o ;

[0054] The circuit connection is as follows:

[0055] The drains of the first switch S1, the third switch S3, and the fifth switch S5 in the three-phase inverter circuit II are the first input terminals of the three-phase resonant converter, electrically connected to the positive terminal of DC input source I; the sources of the second switch S2, the fourth switch S4, and the sixth switch S6 in the three-phase inverter circuit II are the second input terminals of the three-phase resonant converter, electrically connected to the negative terminal of DC input source I; the source of the first switch S1 is connected to the drain of the second switch S2 and the first resonant capacitor C. r1 One end of the circuit is connected at point A; the source of the third switch S3 is connected to the drain of the fourth switch S4 and the same-name terminal of the second primary winding of the second transformer T2, at point B; the source of the fifth switch S5 is connected to the drain of the sixth switch S6 and the third resonant capacitor C. r3 One end of the connection is C;

[0056] The first resonant capacitor C of the two-phase resonant branch III r1 The other end is connected to the first resonant inductor L r1 One end forms the A-phase resonant branch, i.e., the first resonant branch, with the first resonant inductor L. r1 The other end is connected to the same-name terminal of the first primary winding of the first transformer T1; the third resonant capacitor C r3 The other end is connected to the third resonant inductor L r3 One end forms the C-phase resonant branch, i.e., the second resonant branch, and the third resonant inductor L r3 The other end is connected to the same-name terminal of the third primary winding of the third transformer T3; the first magnetizing inductor L m1 Second excitation inductor L m2 and the third magnetizing inductor L m3 These are the equivalent magnetizing inductances on the primary side of the first transformer T1, the second transformer T2, and the third transformer T3, respectively.

[0057] The first magnetizing inductance L of the three-phase transformer IVm1 One end is connected to the same-name terminal of the first primary winding of the first transformer T1, and the first magnetizing inductor L m1 One end is connected to the non-same-name terminal (also called the opposite-name terminal) of the first primary winding of the first transformer T1; the second magnetizing inductor L m2 One end is connected to the same-name terminal of the second primary winding of the second transformer T2, and the second magnetizing inductor L m2 The other end is connected to the non-identical terminal of the second primary winding of the second transformer T2; the third magnetizing inductor L m3 One end is connected to the same-name terminal of the third primary winding of the third transformer T3, and the third magnetizing inductor L m3 The other end is connected to the non-same-name terminal of the third primary winding of the third transformer T3; the non-same-name terminal of the first primary winding of the first transformer T1 is electrically connected to the non-same-name terminal of the second primary winding of the second transformer T2 and the non-same-name terminal of the third primary winding of the third transformer T3, with the connection point being N. The primary windings of the three-phase transformer IV form a star Y connection.

[0058] The first secondary winding of the first transformer T1 is connected to the anode of the first rectifier diode D1 and the cathode of the second rectifier diode D2 at connection point X; the second secondary winding of the second transformer T2 is connected to the anode of the third rectifier diode D3 and the cathode of the fourth rectifier diode D4 at connection point Y; the third secondary winding of the third transformer T3 is connected to the anode of the fifth rectifier diode D5 and the cathode of the sixth rectifier diode D6 at connection point Z; the non-corresponding terminals of the first secondary winding of the first transformer T1 are electrically connected to the non-corresponding terminals of the second secondary winding of the second transformer T2 and the third secondary winding of the third transformer T3 at connection point O; the secondary windings of the three-phase transformer IV form a star Y connection.

[0059] In the three-phase rectifier circuit V, the cathode of the first rectifier diode D1 is electrically connected to the cathode of the third rectifier diode D3 and the cathode of the fifth rectifier diode D5; the anode of the second rectifier diode D2 is electrically connected to the anode of the fourth rectifier diode D4 and the anode of the sixth rectifier diode D6; the anode of the first rectifier diode D1 is electrically connected to the cathode of the second rectifier diode D2, the anode of the third rectifier diode D3 is electrically connected to the cathode of the fourth rectifier diode D4, and the anode of the fifth rectifier diode D5 is electrically connected to the cathode of the sixth rectifier diode D6.

[0060] Output capacitor C in output filter circuit VI o One end is connected to the cathode of the fifth rectifier diode D5 as the first output terminal of the three-phase resonant converter, and the output load R. o One end is connected; output capacitor C o The other end is connected to the anode of the sixth rectifier diode D6 as the second output terminal of the three-phase resonant converter, and to the output load R. oThe other end is connected;

[0061] It should be noted that, Figure 2 The connection point B of the two switching transistors S3 and S4 is directly connected to one end of the primary winding of transformer T2, without a resonant branch. Since the circuit structure of each bridge arm is the same, Figure 2 Alternatively, the connection point A of the two switching transistors S1 and S2 can be directly connected to one end of the primary winding of transformer T1. In this case, the switching transistors S1 and S2 can be regarded as the second bridge arm in the claim, and the primary winding of transformer T1 can be regarded as the second primary winding in the claim. Or, the connection point C of the two switching transistors S5 and S6 can be directly connected to one end of the primary winding of transformer T3. In this case, the switching transistors S5 and S6 can be regarded as the second bridge arm in the claim, and the primary winding of transformer T3 can be regarded as the second primary winding in the claim.

[0062] In addition, the positions of the resonant capacitor and resonant inductor connected in series in the first and second resonant branches can be interchanged, as long as the purpose of circuit resonance can be achieved.

[0063] In practice, Figure 2 The following is an example of the circuit parameter design:

[0064] The input voltage of the three-phase resonant converter is V in 400V, output voltage V o The voltage is 48V, the rated output power is 3000W, the switching frequency is 100kHz, the dead time between the switches in the same bridge arm on the primary side is 350ns, and the resonant capacitor C... r =C r1 =C r3 = 98.25nF, resonant inductance L r =L r1 =L r3 =25.78uH, magnetizing inductance L m =L m1 =L m2 =L m3 =250uH, the relationship between the turns ratio (i.e., the ratio of primary voltage to secondary voltage) n of the three-phase transformer, the turns ratio n1 of the first transformer, the turns ratio n2 of the second transformer, and the turns ratio n3 of the third transformer is n = n1 = n2 = n3 = 25:3, and the output filter capacitor C o The size is 30uF, and the output load R o It is 0.768Ω. The turns ratio n of the three-phase transformer is determined by the input voltage V. in and output voltage V o It is confirmed that the relation is n = V in V o .

[0065] It should be noted that the specific circuit parameters in the above embodiments are only for the purpose of enabling engineers in the art to better understand the technical solution of the present invention, and the parameter design method in the specific implementation of the present invention is not limited to this.

[0066] As those skilled in the art will know, resonant circuits operate in the inductive region, and the input voltage of the resonant cavity leads the resonant current, thus possessing soft-switching characteristics. Prior to this application, those skilled in the art believed that three-phase resonant converters required three resonant branches to achieve soft-switching technology. The inventors of this application made a bold assumption and carefully sought solutions. To simplify the circuit design, one resonant branch was removed. Through simulation and prototype testing, it was verified that such a three-phase resonant converter can still achieve soft switching. Furthermore, by adopting an interleaved control method with a 120° phase difference or by using a star / delta connection for the primary and secondary windings of the transformer, other additional beneficial effects can also be maintained. The specific test verification results are as follows.

[0067] Figure 3 for Figure 2 The driving pulses and soft-switching (ZVS) waveforms of the upper arm switching transistors of the primary side three-phase inverter circuit are shown. The three-phase resonant converter adopts an interleaved control method with a phase difference of 120°. The driving pulses of the three-phase bridge arm switching transistors of the primary side three-phase inverter circuit II are sequentially 120° out of phase. Figure 3 In the middle, V gs1 V gs3 V gs5 These represent the drive pulses for the first switch S1, the third switch S3, and the fifth switch S5, respectively; V DS1 V DS3 V DS5 These represent the drain-source voltages of the first switch S1, the third switch S3, and the fifth switch S5, respectively; from Figure 3 As can be seen from the diagram, the driving pulses of the first switch S1, the third switch S3, and the fifth switch S5 are sequentially 120° out of phase. When the driving pulse V of the first switch S1... gs1 Before triggering, the drain-source voltage V of the first switching transistor S1 DS1 When the voltage drops to 0, the first switch S1 achieves zero-voltage conduction; when the driving pulse V of the third switch S3... gs3 Before triggering, the drain-source voltage V of the third switch S3 DS3 When the voltage drops to 0, the third switch S3 achieves zero-voltage conduction; when the driving pulse V of the fifth switch S5... gs5 Before triggering, the drain-source voltage V of the fifth switch S5 DS5 The voltage drops to 0, and the fifth switch S5 achieves zero-voltage conduction. Similarly, the second switch S2, the fourth switch S4, and the sixth switch S6 can all achieve zero-voltage conduction. This verifies that... Figure 2Although one resonant branch has been removed from the circuit, the soft-switching characteristics are still retained. The turn-on loss of the three-phase inverter circuit on the primary side can be ignored, which is conducive to improving the conversion efficiency. This can improve the overall conversion efficiency and power density of the switching power supply, making it suitable for medium and high power applications.

[0068] Figure 4 As shown Figure 2 The current waveform and output current waveform of the secondary side three-phase rectifier circuit after the three-phase resonant converter adopts the above-mentioned interleaved control method with a phase difference of 120°; Figure 4 In the diagram, iD1, iD2, iD3, iD4, iD5, and iD6 represent the current waveforms flowing through the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3, the fourth rectifier diode D4, the fifth rectifier diode D5, and the sixth rectifier diode D6, respectively. o Indicates the input to the output filter capacitor C o Previous current; Figure 4 Output current I o The current ripple is This verifies Figure 2 By employing an interleaved control method with a 120° phase difference, the circuit also achieves the beneficial effect of reducing output current ripple. This allows for further optimization of the filter capacitor design and a reduction in the output filter capacitor C. o The size and volume of the converter increase the power density and reduce the circuit design cost.

[0069] Figure 5 for Figure 2 The output current waveform of the three-phase transformer when the resonant parameters deviate after the three-phase resonant converter adopts an interleaved control method with a phase difference of 120°. At this time, the first resonant inductor L r1 Deviation 10%, first resonant inductor L r1 Sensitivity L r1 =28.358uH, third resonant inductor L r3 The third resonant inductor L remains unchanged. r3 Sensitivity L r3 =25.78uH. Figure 4 in,i S1 i S2 i S3 These represent the output current waveforms of the first transformer T1, the second transformer T2, and the third transformer T3 in a three-phase transformer system, respectively. The output current i of the first transformer T1 is... S1 The effective value of the current is 45.7A, and the output current i of the second transformer T2 is... S2 The effective value of the current is 43.6A, and the output current i of the third transformer T3 is... S3The effective current value is 49.5A, and the calculated maximum phase-to-phase current imbalance is 12.75%, indicating a significant automatic current sharing effect, thus verifying the... Figure 2 Although one resonant branch is removed from the circuit, when the primary and secondary windings of the three-phase transformer form a star (Y)-star (Y) connection, the beneficial effect of natural current sharing can be maintained, which is conducive to the stable operation of the power supply system. It should be noted that, in specific implementations, the three-phase resonant converter of this invention, in addition to... Figure 2 In addition to the standard topology connection method, there are also various extended topologies.

[0070] Preferably, when the primary and secondary windings of a three-phase transformer form a star (Y)-delta (△) connection, the topology is as follows: Figure 6 As shown;

[0071] Preferably, when the primary and secondary windings of a three-phase transformer form a delta (△)-delta (△) connection, the topology is as follows: Figure 7 As shown;

[0072] Preferably, when the primary and secondary windings of a three-phase transformer form a delta (△) to star (Y) connection, the topology is as follows: Figure 8 As shown;

[0073] Furthermore, to improve conversion efficiency, the diodes in the secondary side three-phase rectifier circuit of the three-phase resonant converter of this invention can be replaced with active switching transistors to achieve synchronous rectification and reduce rectification losses.

[0074] Furthermore, the three-phase resonant converter of the present invention can be used as a DC transformer (DCX), thereby reducing power supply design costs and size, and improving power density and conversion efficiency.

[0075] Furthermore, the resonant frequencies of the first and second resonant branches are the same (without considering the parameter differences of the resonant capacitor and resonant inductor). The operating frequency of the three-phase resonant converter is the resonant frequency of the first or second resonant branch, thereby reducing the circulating current loss on the primary side of the transformer. Moreover, the resonant converter operates at the optimal efficiency point, which can improve the conversion efficiency.

[0076] As Figure 2 An equivalent replacement for the secondary rectifier circuit in the circuit, such as Figure 9The diagram shows another specific circuit of a three-phase resonant converter disclosed in this invention, wherein the secondary circuit is replaced by a three-phase full-bridge parallel rectifier circuit, including a first rectifier bridge circuit, a second rectifier bridge circuit, and a third rectifier bridge circuit. The first AC input terminal of the first rectifier bridge circuit is connected to one end of the first secondary winding, and the second AC input terminal of the first rectifier bridge circuit is connected to the other end of the first secondary winding. The first AC input terminal of the second rectifier bridge circuit is connected to one end of the second secondary winding, and the second AC input terminal of the third rectifier bridge circuit is connected to the other end of the second secondary winding. The first AC input terminal of the third rectifier bridge circuit is connected to one end of the third secondary winding, and the second AC input terminal of the third rectifier bridge circuit is connected to the other end of the third secondary winding. The positive output terminals of the first, second, and third rectifier bridge circuits are simultaneously connected to the first output terminal of the three-phase resonant converter, and the negative output terminals of the first, second, and third rectifier bridge circuits are simultaneously connected to the second output terminal of the three-phase resonant converter. Figure 9 The three-phase full-bridge parallel rectifier circuit in the circuit can reduce the copper loss of the transformer and improve the conversion efficiency.

[0077] The embodiments described above are merely illustrative examples of the technical solutions and content of the present invention. It should be noted that the above embodiments should not be considered as limitations on the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, but these will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims, and should also be considered within the protection scope of the present invention.

Claims

1. A three-phase resonant converter, characterized by, The application relates to a three-phase resonant converter, which comprises a first input end, a second input end, a first output end and a second output end. The three-phase transformer comprises a first primary winding, a second primary winding, a third primary winding, a first secondary winding, a second secondary winding and a third secondary winding. The three-phase resonant converter comprises a first bridge arm, a second bridge arm and a third bridge arm, which are connected between the first input end and the second input end, and each of the bridge arms comprises two series-connected switch tubes. The two-phase resonant branches comprise a first resonant branch and a second resonant branch, the first resonant branch is connected between the connection point of the two switch tubes of the first bridge arm and one end of the first primary winding, and the second resonant branch is connected between the connection point of the two switch tubes of the third bridge arm and one end of the third primary winding. Each of the resonant branches comprises two series-connected resonant capacitors and resonant inductors. The secondary rectifier circuit is used for converting the alternating voltage transmitted by the first secondary winding, the second secondary winding and the third secondary winding into direct current voltage and then outputting the direct current voltage through the first output end and the second output end. The one end of the first primary winding, the one end of the second primary winding, the one end of the third primary winding, the one end of the first secondary winding, the one end of the second secondary winding and the one end of the third secondary winding are homonymous ends. The other end of the first primary winding, the other end of the second primary winding, the other end of the third primary winding, the other end of the first secondary winding, the other end of the second secondary winding and the other end of the third secondary winding are heteronymous ends.

2. The three-phase resonant converter of claim 1, characterized in that: The secondary circuit of the three-phase transformer is a three-phase rectifier circuit, which comprises a first rectifier circuit, a second rectifier circuit and a third rectifier circuit, and each of the rectifier circuits comprises two series-connected rectifier tubes.

3. The three-phase resonant converter of claim 2, characterized in that: The connection point of the two rectifier tubes of the first rectifier circuit is connected with one end of the first primary winding, the connection point of the two rectifier tubes of the second rectifier circuit is connected with one end of the second primary winding, and the connection point of the two rectifier tubes of the third rectifier circuit is connected with one end of the third primary winding. The other end of the first primary winding, the other end of the second primary winding and the other end of the third primary winding are connected together so that the primary windings of the three-phase transformer form a star connection structure. The other end of the first secondary winding, the other end of the second secondary winding and the other end of the third secondary winding are connected together so that the secondary windings of the three-phase transformer form a star connection structure.

4. The three-phase resonant converter of claim 2, wherein: The other end of the first primary winding, the other end of the second primary winding and the other end of the third primary winding are connected together so that the primary windings of the three-phase transformer form a star connection structure; the other end of the first secondary winding is connected to one end of the second secondary winding, the other end of the second secondary winding is connected to one end of the third secondary winding, and the other end of the third secondary winding is connected to one end of the first secondary winding, so that the secondary windings of the three-phase transformer form a delta connection structure.

5. The three-phase resonant converter of claim 2, wherein: The other end of the first primary winding is connected to one end of the second primary winding, the other end of the second primary winding is connected to one end of the third primary winding, and the other end of the third primary winding is connected to one end of the first primary winding, so that the primary windings of the three-phase transformer form a delta connection structure; the other end of the first secondary winding is connected to one end of the second secondary winding, the other end of the second secondary winding is connected to one end of the third secondary winding, and the other end of the third secondary winding is connected to one end of the first secondary winding, so that the secondary windings of the three-phase transformer form a delta connection structure.

6. The three-phase resonant converter of claim 2, wherein: The other end of the first primary winding is connected to one end of the second primary winding, the other end of the second primary winding is connected to one end of the third primary winding, and the other end of the third primary winding is connected to one end of the first primary winding, so that the primary windings of the three-phase transformer form a delta connection structure; the other end of the first secondary winding, the other end of the second secondary winding and the other end of the third secondary winding are connected together so that the secondary windings of the three-phase transformer form a star connection structure.

7. The three-phase resonant converter of claim 1, wherein: The secondary circuit of the three-phase transformer is a three-phase full-bridge parallel rectifier circuit, comprising a first rectifier bridge circuit, a second rectifier bridge circuit and a third rectifier bridge circuit, one end of the first secondary winding is connected to the first AC input end of the first rectifier bridge circuit, the other end of the first secondary winding is connected to the second AC input end of the first rectifier bridge circuit, one end of the second secondary winding is connected to the first AC input end of the second rectifier bridge circuit, the other end of the second secondary winding is connected to the second AC input end of the second rectifier bridge circuit, one end of the third secondary winding is connected to the first AC input end of the third rectifier bridge circuit, the other end of the third secondary winding is connected to the second AC input end of the third rectifier bridge circuit, the positive output end of the first rectifier bridge circuit, the positive output end of the second rectifier bridge circuit and the positive output end of the third rectifier bridge circuit are simultaneously connected to the first output end of the three-phase resonant converter, and the negative output end of the first rectifier bridge circuit, the negative output end of the second rectifier bridge circuit and the negative output end of the third rectifier bridge circuit are simultaneously connected to the second output end of the three-phase resonant converter.

8. The three-phase resonant converter of any of claims 1 to 7, characterized by: The drive pulses of the two switch tubes in the first bridge arm are complementary, and the duty cycles are both 50% after ignoring the dead time; the drive pulses of the two switch tubes in the second bridge arm are complementary, and the duty cycles are both 50% after ignoring the dead time; the drive pulses of the two switch tubes in the third bridge arm are complementary, and the duty cycles are both 50% after ignoring the dead time; and the phase difference of the drive pulses of the upper switch tube in the first bridge arm, the upper switch tube in the second bridge arm and the upper switch tube in the third bridge arm is 120°; the phase difference of the drive pulses of the lower switch tube in the first bridge arm, the lower switch tube in the second bridge arm and the lower switch tube in the third bridge arm is 120°.

9. The three-phase resonant converter according to any one of claims 1 to 7, characterized in that: The resonant frequencies of the first resonant branch and the second resonant branch are consistent, and the working frequency of the three-phase resonant converter is the resonant frequency of the first resonant branch or the resonant frequency of the second resonant branch.

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