A three-phase single-stage resonant converter and a control method thereof

Abstract

The application discloses a three-phase single-stage resonant converter and a control method thereof. The converter comprises a three-phase high-frequency power conversion switch group, a first bus P, a resonant inductor Lr, an isolation transformer, a second bus N, a three-phase resonant capacitor group and a controller connected in sequence. The controller controls the power in the three-phase high-frequency power conversion switch group to conduct in turns, generates alternating current through the three-phase high-frequency power conversion switch group, the resonant inductor Lr, a primary winding Lm and the three-phase resonant capacitor group, and outputs direct current through electromagnetic induction from a secondary winding and a direct current side rectification module. The application solves the problem that the prior art must adopt a two-stage structure. All high-frequency switch tubes can realize soft switching in a wide load range, thereby reducing the loss of the converter, improving the overall efficiency, reducing the use of materials and lowering the generation cost. In addition, the three-phase power supply side current has good sinusoidal degree, high power factor and efficient electric energy transmission.

Description

Technical Field

[0001] This invention relates to power converters, and more particularly to a fully resonant single-stage converter that converts three-phase AC power into DC output. Background Technology

[0002] Modern electrical equipment relies heavily on power supplies. In communication power applications, converters must meet requirements such as total harmonic distortion (THD), harmonic current limiting, isolation, and high conversion efficiency. Higher-power converters employ a three-phase, two-stage design. The first stage uses PFC-controlled boost to achieve power factor correction, while the second stage handles transformer / isolation and output voltage / current control. This stage typically uses resonant switching technology to maximize conversion efficiency and minimize the size and heat dissipation requirements of the power supply design (and thus minimize cost). The problem with this two-stage converter is that the total conversion loss is the sum of the losses of each stage. Even with a typical conversion efficiency of around 96% per stage, the total conversion efficiency can only reach a maximum of 92%.

[0003] The advantages of high efficiency and low cost have attracted many power supply designers to try to develop an effective single-stage AC / DC converter. Figure 1 This diagram illustrates a prior art single-stage AC / DC full-bridge converter, consisting of a three-phase AC input, A-phase power switches (SWA1-SWA4), B-phase power switches (SWB1-SWB4), C-phase power switches (SWC1-SWC4), an output transformer Tr, and full-wave rectifiers (D1, D2) located at the transformer output. The converter is hard-switched PWM controlled; to achieve the desired output voltage, the switching sequence needs to be offset by a certain phase angle. The degree of offset determines the short-circuit period of the output transformer and the current circulation period within the converter. This circulating current (which is entirely different from the current delivered to the full-wave rectifier) ​​causes losses as it passes through the bidirectional switches. Therefore, this converter has low conversion efficiency and, due to the losses, requires a large heatsink and a large number of power devices, resulting in a bulky and costly converter.

[0004] Therefore, people desire isolated converters that are suitable for a wide input voltage range, characterized by high conversion efficiency, a small number of power devices, low electrical stress on power devices, no large inductors or energy storage components, and low harmonic distortion. Summary of the Invention

[0005] To address the aforementioned deficiencies in the existing technology, this invention proposes a three-phase single-stage resonant converter and its control method.

[0006] The technical solution adopted in this invention is to design a three-phase single-stage resonant converter, including a three-phase high-frequency power conversion switch group, a three-phase resonant capacitor group, a resonant inductor Lr, a first bus P, a second bus N, an isolation transformer, a DC-side rectifier module, and a controller. The three-phase high-frequency power conversion switch group is connected between the three-phase power supply and the first bus P. The three-phase resonant capacitor group is connected between the three-phase power supply and the second bus N. The resonant inductor Lr is connected in series with the primary winding Lm of the isolation transformer and then connected between the first bus P and the second bus N. The secondary winding of the isolation transformer is connected to the DC-side rectifier module. The controller controls the power in the three-phase high-frequency power conversion switch group to conduct alternately. Alternating current is generated through the resonance of the three-phase high-frequency power conversion switch group, the resonant inductor Lr, the primary winding Lm, and the three-phase resonant capacitor group. DC power is then output from the secondary winding and the DC-side rectifier module through electromagnetic induction.

[0007] The three-phase single-stage resonant converter also includes a three-phase input filter capacitor bank, which includes a first filter capacitor C1, a second filter capacitor C2, and a third filter capacitor C3. The first filter capacitor C1 is connected between the A-phase input terminal and the B-phase input terminal of the three-phase power supply, the second filter capacitor C2 is connected between the B-phase input terminal and the C-phase input terminal of the three-phase power supply, and the third filter capacitor C3 is connected between the C-phase input terminal and the A-phase input terminal of the three-phase power supply.

[0008] The three-phase high-frequency power conversion switch group includes three switch groups: A-phase switch group (SWAu, SWAd), B-phase switch group (SWBu, SWBd), and C-phase switch group (SWCu, SWCd). The A-phase switch group is connected in series between the A-phase input terminal of the three-phase power supply and the first bus P. The B-phase switch group is connected in series between the B-phase input terminal of the three-phase power supply and the first bus P. The C-phase switch group is connected in series between the C-phase input terminal of the three-phase power supply and the first bus P.

[0009] Each switch group includes an upper switch and a lower switch connected in series. Both the upper and lower switches are transistors with built-in freewheeling diodes and are connected back-to-back in series. The A-phase switch group includes the A-phase upper switch SWAu and the A-phase lower switch SWAd. The B-phase switch group includes the B-phase upper switch SWBu and the B-phase lower switch SWBd. The C-phase switch group includes the C-phase upper switch SWCu and the C-phase lower switch SWCd.

[0010] The three-phase resonant capacitor bank includes three resonant capacitors, which are connected one-to-one between the A-phase input terminal, the B-phase input terminal, the C-phase input terminal and the second bus N.

[0011] The three-phase resonant capacitor bank includes a resonant capacitor connected between the input terminal of phase A and the second bus N, or between the input terminal of phase B and the second bus N, or between the input terminal of phase C and the second bus N.

[0012] The three-phase resonant capacitor bank includes two resonant capacitors, which are connected one-to-one between the A-phase input terminal, the B-phase input terminal and the second bus N, or one-to-one between the A-phase input terminal, the C-phase input terminal and the second bus N, or one-to-one between the B-phase input terminal, the C-phase input terminal and the second bus N.

[0013] This invention also designs a control method for a three-phase single-stage resonant converter. The converter adopts the above-mentioned three-phase single-stage resonant converter. The control method includes collecting the voltage parameters of the three-phase power supply, dividing the three-phase power supply into twelve sectors within one power frequency cycle, with the zero point of the phase voltage and the intersection point of the two-phase voltage waveforms as the dividing points. Each sector occupies 30°. In each sector, the phase with the largest absolute voltage value is denoted as phase H, the phase with a relatively large absolute voltage value is denoted as phase M, and the phase with the smallest absolute voltage value is denoted as phase S. The controller controls the operation of the switching groups in the three-phase high-frequency power conversion switching group, cyclically turning on the corresponding connected switching groups in the order of phase H, phase M, and phase S.

[0014] In the three-phase power supply, near the zero-crossing point of the AC phase voltage, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, M phase, while the corresponding connected switch group of the S phase remains closed.

[0015] In the three-phase power supply, near the intersection of the voltage curves of two phases, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, S phase, H phase, M phase, H phase, S phase.

[0016] The beneficial effects of the technical solution provided by this invention are:

[0017] This invention solves the problem that existing three-phase AC / DC converters must use a two-stage structure to convert three-phase 380V AC voltage to low-voltage DC voltage, achieving electrical isolation with only a single-stage power conversion circuit. All high-frequency switching transistors in this invention can achieve soft switching over a wide load range, thereby reducing converter losses, improving overall efficiency, reducing material usage, and lowering production costs. In addition, it also has the advantages of good sinusoidal current on the three-phase power supply side, high power factor, and high energy transmission efficiency. Attached Figure Description

[0018] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0019] Figure 1 It is a three-phase single-stage converter based on existing technology;

[0020] Figure 2 This invention relates to a converter with three resonant capacitors;

[0021] Figure 3 This invention is a converter in which only the A-phase input terminal is connected to a resonant capacitor;

[0022] Figure 4 This invention is a converter in which only the B-phase input terminal is connected to a resonant capacitor;

[0023] Figure 5 This invention is a converter in which only the C-phase input terminal is connected to a resonant capacitor;

[0024] Figure 6 This invention is a converter in which only the A and B phase input terminals are connected to resonant capacitors;

[0025] Figure 7 This invention is a converter in which only the A and C phase input terminals are connected to resonant capacitors;

[0026] Figure 8 This invention is a converter in which only the B and C phase input terminals are connected to resonant capacitors;

[0027] Figure 9 This is a diagram showing the three-phase AC voltage waveform and sector comparison;

[0028] Figure 10 It is a switching sequence table of the three-phase high-frequency switches for each sector;

[0029] Figure 11 This is a switching sequence table of the upper and lower switches of the three-phase high-frequency power conversion switch group;

[0030] Figure 12a This is the first mode diagram of one switching cycle in the third sector;

[0031] Figure 12b This is the second mode diagram of one switching cycle in the third sector;

[0032] Figure 12c It is the third mode diagram of one switching cycle of the third sector;

[0033] Figure 12d It is the fourth mode diagram of one switching cycle of the third sector;

[0034] Figure 12e It is the fifth mode diagram of one switching cycle in the third sector;

[0035] Figure 12f It is the sixth mode diagram of one switching cycle of the third sector;

[0036] Figure 13 This is the basic circuit diagram of the converter of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0038] This invention discloses a three-phase single-stage resonant converter, see below. Figure 13 The circuit diagram shown includes a three-phase high-frequency power conversion switch group, a three-phase resonant capacitor group, a resonant inductor Lr, a first bus P, a second bus N, an isolation transformer, a DC-side rectifier module, and a controller. The three-phase high-frequency power conversion switch group (SWAu, SWAd, SWBu, SWBd, SWCu, SWCd) is connected between the three-phase power supply and the first bus P. The three-phase resonant capacitor group (CrA, CrB, CrC) is connected between the three-phase power supply and the second bus N. The resonant inductor Lr is connected in series with the primary winding Lm of the isolation transformer and then connected between the first bus P and the second bus N. The secondary winding of the isolation transformer is connected to the DC-side rectifier module. The controller controls the power in the three-phase high-frequency power conversion switch group to conduct alternately. Alternating current is generated through the resonance of the three-phase high-frequency power conversion switch group, the resonant inductor Lr, the primary winding Lm, and the three-phase resonant capacitor group. DC power is then output from the secondary winding and the DC-side rectifier module through electromagnetic induction.

[0039] In a preferred embodiment, the three-phase single-stage resonant converter further includes a three-phase input filter capacitor bank, comprising a first filter capacitor C1, a second filter capacitor C2, and a third filter capacitor C3. The first filter capacitor C1 is connected between the A-phase input terminal and the B-phase input terminal of the three-phase power supply, the second filter capacitor C2 is connected between the B-phase input terminal and the C-phase input terminal of the three-phase power supply, and the third filter capacitor C3 is connected between the C-phase input terminal and the A-phase input terminal of the three-phase power supply. Installing the three-phase input filter capacitor bank between the phase lines of the three-phase power supply provides a high-frequency path for the resonant current.

[0040] In a preferred embodiment, the three-phase high-frequency power conversion switch group includes three switch groups: an A-phase switch group (SWAu, SWAd), a B-phase switch group (SWBu, SWBd), and a C-phase switch group (SWCu, SWCd). The A-phase switch group is connected in series between the A-phase input terminal of the three-phase power supply and the first bus P. The B-phase switch group is connected in series between the B-phase input terminal of the three-phase power supply and the first bus P. The C-phase switch group is connected in series between the C-phase input terminal of the three-phase power supply and the first bus P.

[0041] In a preferred embodiment, each switch group includes an upper switch and a lower switch connected in series. Both the upper and lower switches are transistors with built-in freewheeling diodes, and are connected back-to-back in series. See also... Figures 2 to 8 In any of the attached figures, the A-phase switch group includes the A-phase upper switch SWAu and the A-phase lower switch SWAd, the B-phase switch group includes the B-phase upper switch SWBu and the B-phase lower switch SWBd, and the C-phase switch group includes the C-phase upper switch SWCu and the C-phase lower switch SWCd.

[0042] See Figure 2 In the illustrated embodiment, the three-phase resonant capacitor bank includes three resonant capacitors: phase A resonant capacitor (CrA), phase B resonant capacitor (CrB), and phase C resonant capacitor (CrC). The three resonant capacitors are connected one-to-one between the phase A input terminal, phase B input terminal, phase C input terminal, and the second bus N.

[0043] In some embodiments, the three-phase resonant capacitor bank includes a resonant capacitor connected between the A-phase input terminal and the second bus N, or between the B-phase input terminal and the second bus N, or between the C-phase input terminal and the second bus N.

[0044] exist Figure 3 In the illustrated embodiment, a resonant capacitor CrA is included, which is connected between the input terminal of phase A and the second bus N.

[0045] exist Figure 4 In the illustrated embodiment, a resonant capacitor CrB is included, which is connected between the B-phase input terminal and the second bus N.

[0046] exist Figure 5 In the illustrated embodiment, a resonant capacitor (CrC) is included, which is connected between the C-phase input terminal and the second bus N.

[0047] In other embodiments, the three-phase resonant capacitor bank includes two resonant capacitors, which are connected one-to-one between the A-phase input terminal, the B-phase input terminal and the second bus N, or one-to-one between the A-phase input terminal, the C-phase input terminal and the second bus N, or one-to-one between the B-phase input terminal, the C-phase input terminal and the second bus N.

[0048] exist Figure 6 In the illustrated embodiment, two resonant capacitors, CrA and CrB, are included. CrA is connected between the input terminal of phase A and the second bus N, and CrB is connected between the input terminal of phase B and the second bus N.

[0049] exist Figure 7In the illustrated embodiment, two resonant capacitors, CrA and CrC, are included. CrA is connected between the input terminal of phase A and the second bus N, and CrC is connected between the input terminal of phase C and the second bus N.

[0050] exist Figure 8 In the illustrated embodiment, two resonant capacitors, CrB and CrC, are included. CrB is connected between the input terminal of phase B and the second bus N, and CrC is connected between the input terminal of phase C and the second bus N.

[0051] The DC-side rectifier module employs one of the following: a full-bridge rectifier circuit, a voltage doubler rectifier circuit, or a full-wave rectifier circuit, to provide DC power to the load.

[0052] This invention also proposes a control method for a three-phase single-stage resonant converter, wherein the converter employs the aforementioned three-phase single-stage resonant converter. See also... Figure 9 The diagram showing the three-phase AC voltage waveforms and sector comparison illustrates the control method, which includes acquiring the voltage parameters of the three-phase power supply and dividing the three-phase power supply into twelve sectors within one power frequency cycle, using the zero-point of the phase voltage and the intersection point of the two-phase voltage waveforms as boundaries. Each sector occupies 30°. (See also...) Figure 10 The table shows the switching sequence of the three-phase high-frequency switches for each sector. In each sector, the phase with the largest absolute voltage value is denoted as phase H, the phase with a relatively large absolute voltage value is denoted as phase M, and the phase with the smallest absolute voltage value is denoted as phase S. The controller controls the operation of the switching groups in the three-phase high-frequency power conversion switch group. First, it controls the switching group corresponding to phase H to conduct, then it controls the switching group corresponding to phase M to conduct, and then it controls the switching group corresponding to phase S to conduct. In each sector, the corresponding connected switching groups are cyclically conducted in the order of phase H, phase M, and phase S.

[0053] This switching sequence allows sinusoidal current to flow through the transistors and output rectifier diodes, with the current returning to almost zero as each switching transition occurs, reducing switching losses in the transistors and output diodes.

[0054] Figure 11 This table shows the switching sequence of the upper and lower switches of a phase high-frequency power conversion switch group, which represents the sequence in each 30-degree sector. Figure 2 The functions of the six transistors in the circuit shown are as follows:

[0055] "H" indicates that the switch of the AC input phase with the largest absolute voltage in the current sector is turned on, ultimately controlling the output of the converter.

[0056] "M" indicates that the switch of the AC input phase with a large absolute voltage in the current sector is turned on, ultimately controlling the output of the converter.

[0057] "S" indicates that the switch of the AC input phase with the smallest absolute voltage in the current sector is turned on, ultimately controlling the output of the converter.

[0058] "h" indicates that the resonant voltage generated by the resonant circuit is clamped to the AC input phase with the maximum absolute voltage. This switch (transistor) is turned on throughout the entire 30° sector.

[0059] "m" indicates that the resonant voltage generated by the resonant circuit is clamped to the AC input phase with a larger absolute value voltage.

[0060] "S" indicates that the resonant voltage generated by the resonant circuit is clamped to the AC input phase with the smallest absolute voltage. This switch (transistor) is turned on throughout the entire 30° sector.

[0061] The following reference Figure 2 and Figure 11 The switching sequence of the up and down switches in the third sector (60°-90°):

[0062] 1. Turn on the upper switch connected to phase H throughout the entire sector, and simultaneously turn on the lower switch connected to phase S throughout the entire sector. Then turn on the lower switch connected to phase H.

[0063] In the third sector, the absolute value of the phase B voltage is the largest, followed by the phase C voltage, and the absolute value of the phase A voltage is the smallest. Since the actual value of the phase B voltage is the largest and positive, the upper switch SWBu of the phase B switch group can be turned on throughout the entire sector, labeled h. Since the actual value of the phase C voltage is the smallest and negative, the lower switch SWCd of the phase C switch group can be turned on throughout the entire sector, labeled m. At this time, the lower switch SWBd of the phase B switch group is turned on, labeled H. The converter operating modes are as follows: Figure 12a As shown;

[0064] 2. Then, turn off the lower switch connected to phase H;

[0065] When the lower switch SWBd of phase B switch group is turned off, the converter's operating mode is as follows: Figure 12b As shown, the resonant current freewheels through the C-phase switch group. Before the resonant current decreases to 0, the upper switch SWCu of the C-phase switch group is turned on, which can realize the soft switching of the upper switch SWCu of the C-phase switch group.

[0066] 3. The switch group connected to phase M conducts through the resonant current, and before the resonant current decreases to 0, the upper switch connected to phase M is turned on, and at the same time, the upper switch connected to phase S is turned on.

[0067] The C-phase switch group is connected, with switch SWCu labeled M. The converter's operating mode is as follows: Figure 12c As shown, the switch on phase A is turned on at this time, labeled s, which can clamp the resonant voltage to the phase A voltage.

[0068] 4. Then turn off the upper switch connected to phase M;

[0069] When the switch SWCu on phase C is turned off, the converter's operating mode is as follows: Figure 12d As shown, the resonant current freewheels through the A-phase switch group.

[0070] 5. Then turn on the lower switch connected to phase S;

[0071] When the A-phase switch group's lower switch SWAd is turned on, labeled S, the converter's operating mode is as follows: Figure 12e As shown, soft switching of phase A switch SWAd can be achieved.

[0072] 6. Then, the upper and lower switches connected to phase S are turned off simultaneously. The switch group connected to phase H is connected to the lower switch connected to phase H by the resonant current. Before the resonant current decreases to 0, the lower switch connected to phase H is turned on.

[0073] When both the upper switch SWAu and the lower switch SWAd of phase A switch group are turned off simultaneously, the converter's operating mode is as follows: Figure 12f As shown, the resonant current freewheels through the B-phase switch group, and the lower switch SWBd of the B-phase switch group is turned on before the current decreases to 0, which can realize the soft switching of the lower switch SWBd of the B-phase switch group.

[0074] The above switching sequence cycles repeatedly within a sector.

[0075] In order to achieve the correct AC input current PFC function, the S-phase switch conduction time is close to zero at each phase zero-crossing point, and the converter needs to collect zero current from the AC phase at the voltage zero-crossing point.

[0076] Since attempting to turn the switches on and off again within a very short time period is impractical, the converter can operate in two-phase mode for a period of a few degrees plus or minus each phase zero-crossing point. This mode is called "zero-crossing mode." During this operating mode, the high-frequency switching sequence is simply H, M, H, M, H, M..., with only switches H and M turned on and switch S remaining off. During this period, the on-time of switches H and M is equal. From the perspective of PFC function, the voltage of phase H is equal to that of phase M (but with opposite polarities) at each voltage zero-crossing point, thus requiring equal (but opposite) currents to be drawn from phases H and M. The equal on-time of switches with equal phase voltages will result in equal currents in both phases.

[0077] Therefore, in a preferred embodiment, in the three-phase power supply, near the zero-crossing point of the AC phase voltage, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, M phase, while the corresponding connected switch group of the S phase remains closed.

[0078] For a time interval of plus or minus a few degrees between each pair of phase crossover points, the converter can operate in interleaved mode. In this mode, the corresponding connected switch groups in the sector are cyclically turned on in the order of H phase, M phase, H phase, S phase, H phase, M phase, H phase, S phase... The switch group connecting M phase and S phase is alternately turned on between each H phase opening and closing. From the perspective of PFC function implementation, at each AC phase crossover point, the voltages of M phase and S phase are equal (opposite polarity to H phase), and the current drawn from H phase needs to return to M phase and S phase in the same amount.

[0079] Therefore, in a preferred embodiment, near the intersection of the voltage curves of two phases in the three-phase power supply, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, S phase, H phase, M phase, H phase, S phase.

[0080] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0081] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-phase single-stage resonant converter, characterized in that, It includes a three-phase high-frequency power conversion switch group, a three-phase resonant capacitor group, a resonant inductor Lr, a first bus P, a second bus N, an isolation transformer, a DC-side rectifier module, and a controller, among which... The three-phase high-frequency power conversion switch group is connected between the three-phase power supply and the first bus P, the three-phase resonant capacitor group is connected between the three-phase power supply and the second bus N, the resonant inductor Lr is connected in series with the primary winding Lm of the isolation transformer and then connected between the first bus P and the second bus N, and the secondary winding of the isolation transformer is connected to the DC side rectifier module. The controller controls the power in the three-phase high-frequency power conversion switch group to be turned on in turn. The alternating current is generated by the resonance of the three-phase high-frequency power conversion switch group, resonant inductor Lr, primary winding Lm and three-phase resonant capacitor group. The DC current is output by the secondary winding and DC rectifier module through electromagnetic induction. It also includes a three-phase input filter capacitor bank, which includes a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first filter capacitor C1 is connected between the A-phase input terminal and the B-phase input terminal of the three-phase power supply, the second filter capacitor C2 is connected between the B-phase input terminal and the C-phase input terminal of the three-phase power supply, and the third filter capacitor C3 is connected between the C-phase input terminal and the A-phase input terminal of the three-phase power supply. The three-phase input filter capacitor bank provides a high-frequency path for the resonant current. The three-phase resonant capacitor bank includes three resonant capacitors, which are connected one-to-one between the A-phase input terminal, the B-phase input terminal, the C-phase input terminal and the second bus N; Alternatively, the three-phase resonant capacitor bank may include a resonant capacitor connected between the input terminal of phase A and the second bus N, or between the input terminal of phase B and the second bus N, or between the input terminal of phase C and the second bus N; Alternatively, the three-phase resonant capacitor bank may include two resonant capacitors, which are connected one-to-one between the A-phase input terminal, the B-phase input terminal and the second bus N, or one-to-one between the A-phase input terminal, the C-phase input terminal and the second bus N, or one-to-one between the B-phase input terminal, the C-phase input terminal and the second bus N.

2. The three-phase single-stage resonant converter as described in claim 1, characterized in that, The three-phase high-frequency power conversion switch group includes three switch groups: A-phase switch group (SWAu, SWAd), B-phase switch group (SWBu, SWBd), and C-phase switch group (SWCu, SWCd). The A-phase switch group is connected in series between the A-phase input terminal of the three-phase power supply and the first bus P. The B-phase switch group is connected in series between the B-phase input terminal of the three-phase power supply and the first bus P. The C-phase switch group is connected in series between the C-phase input terminal of the three-phase power supply and the first bus P.

3. The three-phase single-stage resonant converter as described in claim 2, characterized in that, Each switch group includes an upper switch and a lower switch connected in series. Both the upper and lower switches are transistors with built-in freewheeling diodes and are connected back-to-back in series. The A-phase switch group includes the A-phase upper switch SWAu and the A-phase lower switch SWAd. The B-phase switch group includes the B-phase upper switch SWBu and the B-phase lower switch SWBd. The C-phase switch group includes the C-phase upper switch SWCu and the C-phase lower switch SWCd.

4. A control method for a three-phase single-stage resonant converter, characterized in that, The converter adopts the three-phase single-stage resonant converter according to any one of claims 1 to 3. The control method includes collecting the voltage parameters of the three-phase power supply, dividing the three-phase power supply into twelve sectors within one power frequency cycle, with the zero point of the phase voltage and the intersection point of the two-phase voltage waveform as the dividing points, each sector occupying 30°. In each sector, the phase with the largest absolute voltage value of the three-phase power supply is denoted as phase H, the phase with a relatively large absolute voltage value is denoted as phase M, and the phase with the smallest absolute voltage value is denoted as phase S. The controller controls the operation of the switching groups in the three-phase high-frequency power conversion switching group, cyclically turning on the corresponding connected switching groups in the order of phase H, phase M, and phase S.

5. The control method for a three-phase single-stage resonant converter as described in claim 4, characterized in that, In the three-phase power supply, near the zero-crossing point of the AC phase voltage, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, M phase, while the corresponding connected switch group of the S phase remains closed.

6. The control method for a three-phase single-stage resonant converter as described in claim 5, characterized in that, In the three-phase power supply, near the intersection of the voltage curves of two phases, the corresponding connected switch groups are cyclically turned on in the order of H phase, M phase, H phase, S phase, H phase, M phase, H phase, S phase.

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