Converter and control method and apparatus therefor

Abstract

A converter and a control method and apparatus therefor. A controller in the converter is configured to, in response to an alternating current voltage of an alternating current end of the converter being within a preset zero-crossing range, control an outer switching transistor in an upper bidirectional switching transistor of a first alternating current side bridge arm and an inner switching transistor in a lower bidirectional switching transistor to be complementarily turned on, and an inner switching transistor in the upper bidirectional switching transistor of the first alternating current side bridge arm and an outer switching transistor in the lower bidirectional switching transistor to be complementarily turned on, and control two switching transistors in an upper bidirectional switching transistor of a second alternating current side bridge arm to be complementarily turned on, and two switching transistors in a lower bidirectional switching transistor of the second alternating current side bridge arm to be complementarily turned on. The two switching transistors in the upper bidirectional switching transistor of the first alternating current side bridge arm are in phase with the two outer switching transistors in the second alternating current side bridge arm.

Description

Converter and control method and device thereof

[0001] The present disclosure claims priority to the Chinese patent application No. 202510244464.5, filed on February 28, 2025, and entitled "Converter and control method and device thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to a converter and a control method and device thereof. BACKGROUND

[0003] Compared with a two-stage structure, a single-stage AC / DC (alternating current / direct current) converter cancels the use of an AC bus capacitor, and has the advantages of fewer devices, high efficiency, high power density, and low cost.

[0004] The single-stage AC / DC converter includes an AC side conversion circuit, a transformer, and a DC side conversion circuit. The on-off control strategy of each switch tube of the AC side bridge arm in the AC side conversion circuit in the positive half cycle of the AC voltage is different from the on-off control strategy of each switch tube in the negative half cycle of the AC voltage.

[0005] In the related art, near the zero-crossing point of the AC voltage, the on-off control strategy applied to each switch tube is easily inconsistent with the actual on-off control strategy required by each switch tube due to the influence of many factors such as AC voltage disturbance, distortion, polarity jump, and polarity misjudgment, which causes the AC side bridge arm in the AC side conversion circuit to be short-circuited, the AC current to be distorted, and thus the current quality of the AC / DC converter is affected, resulting in low operation reliability. SUMMARY

[0006] The following is a summary of the detailed description of the present disclosure. This summary is not intended to limit the protection scope of the claims.

[0007] In a first aspect, an embodiment of the present disclosure provides a converter, including a controller, a transformer, and a first AC side bridge arm and a second AC side bridge arm connected in parallel at an AC end of the converter, two ends of a first winding of the transformer being connected to a bridge arm midpoint of the first AC side bridge arm and a bridge arm midpoint of the second AC side bridge arm respectively; each AC side bridge arm includes a series connection of an upper bidirectional switch tube and a lower bidirectional switch tube, and a connection point of the series connection of the upper bidirectional switch tube and the lower bidirectional switch tube serving as a bridge arm midpoint of the AC side bridge arm; the topology of each bidirectional switch tube is the same, and the topology of each bidirectional switch tube includes two switch tubes connected in series, and a switch tube directly connected to the AC end is an outer switch tube, and a switch tube directly connected to the bridge arm midpoint of the AC side bridge arm is an inner switch tube;

[0008] The controller is configured to, in response to the AC voltage at the AC end being within a preset range of a zero-crossing point, control the outer switch tube in the upper bidirectional switch tube of the first AC side bridge arm and the inner switch tube in the lower bidirectional switch tube to be complementary conduction, and the inner switch tube in the upper bidirectional switch tube of the first AC side bridge arm and the outer switch tube in the lower bidirectional switch tube to be complementary conduction, and control the two switch tubes in the upper bidirectional switch tube of the second AC side bridge arm to be complementary conduction, and the two switch tubes in the lower bidirectional switch tube of the second AC side bridge arm to be complementary conduction;

[0009] The two switch tubes in the upper bidirectional switch tube of the first AC side bridge arm are in phase, the two switch tubes in the lower bidirectional switch tube of the first AC side bridge arm are in phase, the two outer switch tubes in the second AC side bridge arm are in phase, and the two inner switch tubes in the second AC side bridge arm are in phase.

[0010] The two switch tubes in the upper bidirectional switch tube of the first AC side bridge arm are in phase with the two outer switch tubes in the second AC side bridge arm, or the two switch tubes in the upper bidirectional switch tube of the first AC side bridge arm are in phase with the two inner switch tubes in the second AC side bridge arm.

[0011] In a second aspect, the embodiments of the present disclosure provide a control method of a converter, the converter comprising a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel at an AC end of the converter, two ends of a first winding of the transformer being connected to a bridge arm midpoint of the first AC side bridge arm and a bridge arm midpoint of the second AC side bridge arm respectively; each AC side bridge arm comprises an upper bidirectional switch tube and a lower bidirectional switch tube connected in series, and a connection point of the upper bidirectional switch tube and the lower bidirectional switch tube connected in series serving as a bridge arm midpoint of the AC side bridge arm; the topological structure of each bidirectional switch tube is the same, and the topological structure of each bidirectional switch tube comprises two switch tubes connected in series, and a switch tube directly connected to the AC end serving as an outer switch tube and a switch tube directly connected to the bridge arm midpoint of the AC side bridge arm serving as an inner switch tube;

[0012] The control method comprises:

[0013] In response to the AC voltage at the AC end being within a preset range of a zero-crossing point, the outer switch tube in the upper bidirectional switch tube of the first AC side bridge arm and the inner switch tube in the lower bidirectional switch tube are controlled to be complementary conduction, and the inner switch tube in the upper bidirectional switch tube of the first AC side bridge arm and the outer switch tube in the lower bidirectional switch tube are controlled to be complementary conduction, and the two switch tubes in the upper bidirectional switch tube of the second AC side bridge arm are controlled to be complementary conduction, and the two switch tubes in the lower bidirectional switch tube of the second AC side bridge arm are controlled to be complementary conduction.

[0014] Among them, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase.

[0015] Furthermore, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two outer switches in the second AC side bridge arm, or the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two inner switches in the second AC side bridge arm.

[0016] Thirdly, embodiments of this disclosure provide a control device for a converter. The converter includes a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter. The two ends of the first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm. Each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm. The topology of each bidirectional switch is the same, and the topology of each bidirectional switch includes two switches connected in series. The switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch.

[0017] The control device includes:

[0018] The zero-crossing identification module is configured to determine that the AC voltage at the AC terminal is within a preset zero-crossing range;

[0019] The drive control module is configured to, in response to the AC voltage being within a preset range of zero crossing, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct complementaryly, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct complementaryly, and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct complementaryly, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct complementaryly.

[0020] Among them, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase.

[0021] Furthermore, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two outer switches in the second AC side bridge arm, or the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two inner switches in the second AC side bridge arm.

[0022] Brief description of the attached figures

[0023] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments of this disclosure will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 is a schematic diagram of the topology of the AC side bridge arm in one embodiment;

[0025] Figure 2A is a schematic diagram of one of the topologies of a bidirectional switch in one embodiment;

[0026] Figure 2B is a second schematic diagram of the topology of a bidirectional switching transistor in one embodiment;

[0027] Figure 3A is a schematic diagram of the topology of a single-stage AC / DC converter in one embodiment;

[0028] Figure 3B is one of the state diagrams of the AC side full-bridge circuit in Figure 3A;

[0029] Figure 3C is the second schematic diagram of the AC side full-bridge circuit in Figure 3A;

[0030] Figure 4A is a schematic diagram of the ideal AC voltage and current waveforms in one embodiment;

[0031] Figure 4B is a schematic diagram of AC voltage and current distortion waveforms in one embodiment;

[0032] Figure 4C is the third schematic diagram of the AC side full-bridge circuit in Figure 3A;

[0033] Figure 5 is a schematic diagram of the converter topology in one embodiment;

[0034] Figure 6 is a schematic diagram of the AC voltage region division in one embodiment;

[0035] Figure 7A is one of the schematic diagrams of the driving logic of the AC side full-bridge circuit in Figure 5;

[0036] Figure 7B is the second schematic diagram of the driving logic of the AC side full-bridge circuit in Figure 5;

[0037] Figure 8A shows one of the freewheeling paths of the resonant current within the preset range of the zero-crossing point of the AC voltage in Figure 5.

[0038] Figure 8B shows the second freewheeling path of the resonant current within the preset range of the zero-crossing point of the AC voltage in Figure 5.

[0039] Figure 8C shows the third freewheeling path of the resonant current within the preset range of the zero-crossing point of the AC voltage in Figure 5.

[0040] Figure 8D shows the fourth freewheeling path of the resonant current within the preset range of the zero-crossing point of the AC voltage in Figure 5.

[0041] Figure 9 is the third schematic diagram of the driving logic of the AC side full-bridge circuit in Figure 5. Embodiments of the present invention

[0042] To facilitate understanding of this disclosure, a more complete description will now be given with reference to the accompanying drawings, which illustrate embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure.

[0044] It is understood that the terms "first," "second," etc., as used herein may be configured to describe various elements, but these elements are not limited by these terms. These terms are only configured to distinguish one element from another. For example, without departing from the scope of this disclosure, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0045] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0046] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0047] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0048] A single-stage AC / DC converter includes an AC-side conversion circuit, a transformer, and a DC-side conversion circuit. The AC-side conversion circuit is connected between the AC terminal of the converter and the transformer, while the DC-side conversion circuit is connected between the transformer and the DC terminal of the converter. The AC-side conversion circuit includes two AC-side arms and can convert single-phase power in multi-phase AC power (e.g., three-phase AC power).

[0049] An AC-side bridge arm typically consists of two bidirectional switching transistors, located in the upper and lower halves of the AC-side bridge arm, respectively. The bidirectional switching transistor in the upper half of the bridge arm is called the upper bidirectional switching transistor, and the bidirectional switching transistor in the lower half of the bridge arm is called the lower bidirectional switching transistor. The upper and lower bidirectional switching transistors are connected in series, and the connection point of the upper and lower bidirectional switching transistors in series is the midpoint of the bridge arm. Referring to Figure 1, which exemplarily illustrates an AC-side bridge arm, each AC-side bridge arm includes an upper half and a lower half. The bidirectional switching transistor in the upper half of the bridge arm is marked with S, and the bidirectional switching transistor in the lower half of the bridge arm is marked with S'.

[0050] A bidirectional switching transistor comprises two switching transistors connected in series. These switching transistors can be controllable, such as any one of the following: Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), Gallium Nitride (GaN), Silicon Carbide (SiC), Bipolar Junction Transistor (BJT), or Insulated-Gate Bipolar Transistor (IGBT). There are various topologies for bidirectional switching transistors. Referring to Figure 2A, one exemplary topology consists of two switching transistors connected in series with their common source terminals; referring to Figure 2B, another exemplary topology consists of two switching transistors connected in series with their common drain terminals.

[0051] Referring to Figure 3A, which illustrates an exemplary single-stage AC / DC converter, it includes two AC-side bridge arms, namely AC-side bridge arm A and AC-side bridge arm B.

[0052] The single-stage AC / DC converter also includes an AC-side filter inductor L1, an AC-side filter capacitor C1, an impedance network Z1, a transformer Tr, two DC-side bridge arms (DC-side bridge arm C and DC-side bridge arm D, respectively), and a DC-side capacitor C2. The filter capacitor C1 can be a small-capacity film capacitor, avoiding the use of large-capacity electrolytic capacitors. The impedance network Z1 includes an inductor, or the impedance network Z1 includes a capacitor, or the impedance network Z1 includes both an inductor and a capacitor. That is, the impedance network Z1 includes at least one of an inductor and a capacitor. The location of the impedance network Z1 is not limited to that shown in Figure 3A, and it can also be located in other positions in the converter topology; this disclosure does not limit this. Vac is the single-phase AC voltage at the AC end, ir1 is the current in the first winding of transformer Tr, and Vdc is the DC voltage at the DC end. The winding of transformer Tr closer to the AC end is the first winding of transformer Tr, and the winding of transformer Tr closer to the DC end is the second winding of transformer Tr. The second winding and the first winding of transformer Tr are the primary and secondary windings of transformer Tr, respectively.

[0053] On the AC side, the midpoint of AC side bridge arm A is connected to the first end of the first winding of transformer Tr through impedance network Z1, and the midpoint of AC side bridge arm B is connected to the second end of the first winding of transformer Tr. On the DC side, the two ends of the second winding of transformer Tr are connected to the midpoints of DC side bridge arm C and DC side bridge arm D, respectively.

[0054] Referring to Figure 3A, the bidirectional switching transistors of the upper half of AC side bridge arm A include a first switch S1 and a second switch S2 connected in series, and the bidirectional switching transistors of the lower half of AC side bridge arm A include a third switch S3 and a fourth switch S4 connected in series; or, the bidirectional switching transistors of the upper half of AC side bridge arm A include a third switch S3 and a fourth switch S4 connected in series, and the bidirectional switching transistors of the lower half of AC side bridge arm A include a first switch S1 and a second switch S2 connected in series. The bidirectional switching transistors of the upper half of AC side bridge arm B include a fifth switch S5 and a sixth switch S6 connected in series, and the bidirectional switching transistors of the lower half of AC side bridge arm B include a seventh switch S7 and an eighth switch S8 connected in series; or, the bidirectional switching transistors of the upper half of AC side bridge arm B include a seventh switch S7 and an eighth switch S8 connected in series, and the bidirectional switching transistors of the lower half of AC side bridge arm B include a fifth switch S5 and a sixth switch S6 connected in series. DC-side bridge arm C and DC-side bridge arm D constitute a full-bridge circuit of the DC-side converter circuit. DC-side bridge arm C includes a ninth switch S9 and a tenth switch S10 connected in series, and DC-side bridge arm D includes an eleventh switch S11 and a twelfth switch S12 connected in series.

[0055] The following examples illustrate the technical solutions of the embodiments of this disclosure by using the following examples: the bidirectional switching transistors of the upper half of AC bridge arm A include a first switching transistor S1 and a second switching transistor S2 connected in series; the bidirectional switching transistors of the lower half of AC bridge arm A include a third switching transistor S3 and a fourth switching transistor S4 connected in series; and the bidirectional switching transistors of the upper half of AC bridge arm B include a fifth switching transistor S5 and a sixth switching transistor S6 connected in series, and the bidirectional switching transistors of the lower half of AC bridge arm B include a seventh switching transistor S7 and an eighth switching transistor S8 connected in series.

[0056] Referring to Figure 3A, in the related technology, during the positive half-cycle of the AC voltage, switching transistors S2, S4, S6, and S8 are all normally conducting, while switching transistors S1, S3, S5, and S7 operate at high frequency. The corresponding circuit diagram is shown in Figure 3B, where "&" represents the meaning of "AND". During the negative half-cycle of the AC voltage, switching transistors S1, S3, S5, and S7 are all normally conducting, while switching transistors S2, S4, S6, and S8 operate at high frequency. The corresponding circuit diagram is shown in Figure 3C.

[0057] For example, the high-frequency switching operation of switches S1, S3, S5, and S7 can be, but is not limited to, the high-frequency complementary conduction of the first switch S1 and the third switch S3, and the high-frequency complementary conduction of the fifth switch S5 and the seventh switch S7. The high-frequency switching operation of switches S2, S4, S6, and S8 can be, but is not limited to, the high-frequency complementary conduction of the second switch S2 and the fourth switch S4, and the high-frequency complementary conduction of the sixth switch S6 and the eighth switch S8. Regardless of whether the AC voltage is in the positive or negative half-cycle, the DC-side bridge arm can perform high-frequency switching operation. The switching frequency of the DC-side bridge arm can be the same as or different from the switching frequency of the AC-side bridge arm. For example, the switching frequency of the high-frequency switching operation is greater than or equal to 1 kHz.

[0058] In related technologies, near the zero-crossing point of the AC voltage, affected by AC voltage disturbances and the sampling delay of the controller, the controller cannot accurately and timely determine the change in AC voltage polarity based on the sampled AC voltage polarity. The misjudgment of AC voltage polarity will cause all the switches of the AC side bridge arm to turn on, resulting in a short circuit in the AC side bridge arm and distortion of AC current.

[0059] For example, referring to Figure 4A, we see the ideal waveforms of AC voltage Vac and AC current iac. Referring to Figure 4B, taking the time period t1~t2 as an example, during this time period, the AC voltage should still be in the positive half-cycle. However, the AC voltage is disturbed, resulting in a negative voltage. Based on the voltage polarity, it might be mistakenly assumed that the AC voltage has entered the negative half-cycle, thus implementing a switching control strategy where switches S1, S3, S5, and S7 are all normally conducting and switches S2, S4, S6, and S8 operate at high frequency. However, the AC current is still in the positive half-cycle. Referring to Figure 4C, since the AC current is positive, it will flow directly through the body diodes of switches S2, S4, S6, and S8, causing a short circuit in the AC side bridge arm. At the same time, referring to Figure 4B, the AC current is distorted.

[0060] In view of this, embodiments of the present disclosure provide a converter and its control method and apparatus that can avoid short circuits in the AC side bridge arm and improve AC current distortion near the zero-crossing point of the AC voltage.

[0061] The converter provided in this embodiment may be, but is not limited to, a single-stage AC / DC converter. Referring to FIG5, the converter in this embodiment includes a controller, a transformer, and two AC-side bridge arms connected in parallel at the AC terminal of the converter, namely AC-side bridge arm A and AC-side bridge arm B. AC-side bridge arm A is the first AC-side bridge arm and AC-side bridge arm B is the second AC-side bridge arm, or AC-side bridge arm A is the second AC-side bridge arm and AC-side bridge arm B is the first AC-side bridge arm.

[0062] The following examples use AC side bridge arm A as the first AC side bridge arm and AC side bridge arm B as the second AC side bridge arm to explain the technical solutions of the embodiments of this disclosure.

[0063] Each AC-side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series. The topology of each bidirectional switch in each AC-side bridge arm of the converter is the same. For example, each bidirectional switch in each AC-side bridge arm of the converter adopts the topology shown in Figure 2A or the topology shown in Figure 2B. Among the two bidirectional switches connected in series, the switch directly connected to the AC terminal of the converter is the outer switch, and the switch directly connected to the midpoint of the bridge arm is the inner switch. The connection point where the upper and lower bidirectional switches are connected in series is the midpoint of the bridge arm.

[0064] Referring to Figure 5, in the upper bidirectional switch tube of AC side bridge arm A, the outer switch tube is the first switch tube S1 and the inner switch tube is the second switch tube S2; in the lower bidirectional switch tube of AC side bridge arm A, the inner switch tube is the third switch tube S3 and the outer switch tube is the fourth switch tube S4; or, in the upper bidirectional switch tube of AC side bridge arm A, the outer switch tube is the fourth switch tube S4 and the inner switch tube is the third switch tube S3; in the lower bidirectional switch tube of AC side bridge arm A, the outer switch tube is the first switch tube S1 and the inner switch tube is the second switch tube S2. In the upper bidirectional switch of AC side bridge arm B, the outer switch is the fifth switch S5 and the inner switch is the sixth switch S6; in the lower bidirectional switch of AC side bridge arm B, the inner switch is the seventh switch S7 and the outer switch is the eighth switch S8; or, in the upper bidirectional switch of AC side bridge arm B, the outer switch is the eighth switch S8 and the inner switch is the seventh switch S7; in the lower bidirectional switch of AC side bridge arm B, the outer switch is the fifth switch S5 and the inner switch is the sixth switch S6.

[0065] The following examples illustrate the technical solutions of the embodiments of this disclosure by using the following examples: the outer switch of the upper bidirectional switch of AC side bridge arm A is the first switch S1 and the inner switch is the second switch S2; the inner switch of the lower bidirectional switch of AC side bridge arm A is the third switch S3 and the outer switch is the fourth switch S4; the outer switch of the upper bidirectional switch of AC side bridge arm B is the fifth switch S5 and the inner switch is the sixth switch S6; and the inner switch of the lower bidirectional switch of AC side bridge arm B is the seventh switch S7 and the outer switch is the eighth switch S8.

[0066] The controller can detect the AC voltage at the AC terminal of the converter in real time and determine whether the AC voltage is within the preset zero-crossing range. For example, during the operation of the converter, the controller can acquire the AC voltage in real time and then determine whether the AC voltage is within the preset zero-crossing range. For example, the AC voltage may be the grid voltage. The controller compares the acquired AC voltage with the preset zero-crossing range to determine whether the AC voltage is within the preset zero-crossing range.

[0067] The zero-crossing preset range includes at least the zero-crossing point of the AC voltage. The zero-crossing preset range represents a voltage range of the AC voltage near the zero-crossing point, where the AC voltage passes through the preset range from the positive half-wave region into the negative half-wave region, or vice versa. Referring to Figure 6, in one implementation, a first preset voltage threshold Vth1 is positive, and a second preset voltage threshold Vth2 is negative. If the current AC voltage is greater than the first preset voltage threshold Vth1, it is determined that the current AC voltage is within the positive half-wave region, i.e., region 1. If the current AC voltage is equal to or less than the first preset voltage threshold Vth1 and greater than or equal to the second preset voltage threshold Vth2, it is determined that the current AC voltage is within the zero-crossing preset range, i.e., region 3. If the current AC voltage is less than the second preset voltage threshold Vth2, it is determined that the current AC voltage is within the negative half-wave region, i.e., region 2. The specific values ​​of the first preset voltage threshold Vth1 and the second preset voltage threshold Vth2 can be configured as needed according to the actual application. Referring to Figure 6, in one implementation, the AC voltage can also be divided into regions according to the phase angle θ of the AC voltage. Dividing the AC voltage region according to the preset phase angle and dividing the AC voltage region according to the preset voltage threshold are corresponding. For example, assuming the phase angle θ1=0, then the phase angle θ2=90°±Δθ can be divided into region 3. The phase angle Δθ can be configured as needed according to the actual application.

[0068] Referring to Figures 5, 6, 7A, and 7B, the controller is configured to perform the following control in response to the AC voltage being within a preset zero-crossing range: controlling the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct complementaryly, and controlling the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct complementaryly; and controlling the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct complementaryly, and controlling the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct complementaryly. Specifically, the two switches in the upper bidirectional switching transistors of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switching transistors of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase; and the two switches in the upper bidirectional switching transistors of the first AC side bridge arm are in phase with the two outer switches in the second AC side bridge arm, or the two switches in the upper bidirectional switching transistors of the first AC side bridge arm are in phase with the two inner switches in the second AC side bridge arm.

[0069] The switching frequency for complementary conduction of the AC side bridge arm switches is not limited. For example, the switching period for complementary conduction can be much shorter than the duration of the zero-crossing preset range. Relatively speaking, the more times complementary conduction occurs within the zero-crossing preset range, i.e., the higher the switching frequency, the longer the freewheeling path can be provided for the current in the first winding, which is more beneficial for reducing the tube stress of the AC side bridge arm switches. For example, the switching frequency can be as high as several thousand to several hundred kilohertz, or as low as an order of magnitude smaller than the AC mains frequency, such as a few hertz, tens of hertz, or hundreds of hertz.

[0070] Furthermore, in the AC side bridge arm, a reasonable dead time can be set between any two complementary conducting switches to avoid bridge arm shoot-through. The accompanying drawings illustrate the dead time by showing that the on and off times of the two complementary conducting switches are different. Also, within the switching cycle of the AC side bridge arm, the duty cycle of each switch in the AC side bridge arm can be, but is not limited to, 50%.

[0071] For example, referring to Figures 5, 6, 7A and 7B, in response to the AC voltage being within a preset zero-crossing range, the controller controls the first switch S1 and the third switch S3 to conduct complementaryly within the preset zero-crossing range, and the second switch S2 and the fourth switch S4 to conduct complementaryly within the preset zero-crossing range, and the fifth switch S5 and the sixth switch S6 to conduct complementaryly within the preset zero-crossing range, and the seventh switch S7 and the eighth switch S8 to conduct complementaryly within the preset zero-crossing range. In this configuration, the first switch S1 is in phase with the second switch S2, the third switch S3 is in phase with the fourth switch S4, the fifth switch S5 is in phase with the eighth switch S8, and the sixth switch S6 is in phase with the seventh switch S7. Also, referring to Figure 7A, the phases of the first switch S1 and the second switch S2 and the phases of the sixth switch S6 and the seventh switch S7 are the same. Alternatively, referring to Figure 7B, the phases of the first switch S1 and the second switch S2 and the phases of the fifth switch S5 and the eighth switch S8 are the same.

[0072] Furthermore, referring to Figure 7A, it can be seen that when the phases of the first switch S1 and the second switch S2 and the phases of the sixth switch S6 and the seventh switch S7 are the same, the phases of the third switch S3 and the fourth switch S4 and the phases of the fifth switch S5 and the eighth switch S8 are the same. Referring to Figure 7B, it can be seen that when the phases of the first switch S1 and the second switch S2 and the phases of the fifth switch S5 and the eighth switch S8 are the same, the phases of the third switch S3 and the fourth switch S4 and the phases of the sixth switch S6 and the seventh switch S7 are the same.

[0073] Referring again to Figures 5, 6, 7A, and 7B, in this embodiment of the present disclosure, when the current AC voltage is in the positive half-wave region, i.e., region 1, switches S2, S4, S6, and S8 are all normally conducting, and switches S1, S3, S5, and S7 operate at high frequency; when the current AC voltage is in the negative half-wave region, i.e., region 2, switches S1, S3, S5, and S7 are all normally conducting, and switches S2, S4, S6, and S8 operate at high frequency.

[0074] Thus, within the preset range of the zero-crossing point, i.e., within region 3 in Figures 6, 7A, and 7B, each AC-side bridge arm always has two off switching transistors, thereby avoiding short circuits in each AC-side bridge arm, improving AC current distortion, and thus enhancing the current quality and operational reliability of the converter. Furthermore, it can provide a freewheeling path for the current of the first winding of the transformer Tr during at least a portion of the time period within the preset range of the zero-crossing point, thereby reducing the tube voltage stress of the AC-side bridge arm switching transistors. In the freewheeling circuit, the current of the first winding flows through the body diode of the corresponding switching transistor, thereby achieving zero-voltage turn-on of the switching transistor and reducing the turn-on loss of the switching transistor.

[0075] In an exemplary embodiment, referring to Figures 5, 6, 7A, and 7B, the controller is configured to, in response to the AC voltage being within a preset zero-crossing range, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct in a high-frequency complementary manner, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch of the first AC side bridge arm to conduct in a high-frequency complementary manner; and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct in a high-frequency complementary manner, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct in a high-frequency complementary manner. The switching frequency of the high-frequency complementary conduction is greater than or equal to 1 kHz.

[0076] In an exemplary embodiment, referring to Figures 5, 6, 7A, and 7B, each bidirectional switch in each AC-side bridge arm of the converter is a common-source series topology. The controller is also configured to, in response to the AC voltage being within a preset zero-crossing range and the current ir1 of the first winding of the transformer Tr flowing into the first winding from the midpoint of the first AC-side bridge arm, as shown in Figure 8A, control the two switches in the upper bidirectional switch of the first AC-side bridge arm and the two inner switches in the second AC-side bridge arm to conduct, or, as shown in Figure 8B, control the two switches in the lower bidirectional switch of the first AC-side bridge arm and the two inner switches in the second AC-side bridge arm to conduct.

[0077] As shown in Figure 8A, when switches S1, S2, S6, and S7 are on and switches S3, S4, S5, and S8 are off, the turn-off of the third switch S3, the fourth switch S4, the fifth switch S5, and the eighth switch S8 can prevent short circuits in AC side bridge arms A and B, improve AC current distortion, and thus enhance the current quality and operational reliability of the converter. Simultaneously, the current ir1 of the first winding can flow sequentially through the impedance network Z1 and the first winding, then into the midpoint of AC side bridge arm B, and then... After flowing through the body diodes of the fifth switch S5 and the eighth switch S8, the current flows into the midpoint of the AC side bridge arm A. This provides a freewheeling path for the current ir1 of the first winding of the transformer Tr, thereby reducing the voltage stress on the AC side bridge arm switches. Furthermore, in the freewheeling circuit, the current of the first winding flows through the body diode of the corresponding switch, achieving zero-voltage turn-on and reducing turn-on losses. Additionally, the current of the first winding can also flow through at least one of the filter capacitor C1 and the AC terminal of the converter. In the accompanying drawings, an "×" is used to indicate that the switch is turned off.

[0078] As shown in Figure 8B, when switches S3, S4, S6, and S7 are on and switches S1, S2, S5, and S8 are off, the turn-off of the first switch S1, the second switch S2, the fifth switch S5, and the eighth switch S8 can prevent short circuits in AC side bridge arms A and B, improve AC current distortion, and thus enhance the current quality and operational reliability of the converter. Simultaneously, the current ir1 of the first winding can flow sequentially through the impedance network Z1 and the first winding, then into the midpoint of the AC side bridge arm B, and then through the body diodes of the fifth switch S5 and the eighth switch S8, before flowing into the midpoint of the AC side bridge arm A. This provides a freewheeling path for the current ir1 of the first winding of the transformer Tr, thereby reducing the voltage stress on the AC side bridge arm switches. Furthermore, in the freewheeling circuit, the current of the first winding flows through the body diodes of the corresponding switches, achieving zero-voltage turn-on and reducing the turn-on losses of the switches.

[0079] In an exemplary embodiment, referring to Figures 5, 6, 7A, and 7B, each bidirectional switch in each AC-side bridge arm of the converter is a common-source series topology. The controller is also configured to, in response to the AC voltage being within a preset zero-crossing range and the current ir1 of the first winding of the transformer Tr flowing from the first winding into the midpoint of the first AC-side bridge arm, as shown in Figure 8C, control the two switches in the upper bidirectional switch of the first AC-side bridge arm and the two external switches in the second AC-side bridge arm to conduct, or, as shown in Figure 8D, control the two switches in the lower bidirectional switch of the first AC-side bridge arm and the two external switches in the second AC-side bridge arm to conduct.

[0080] As shown in Figure 8C, with switches S1, S2, S5, and S8 on and switches S3, S4, S6, and S7 off, the turn-off of the third switch S3, the fourth switch S4, the sixth switch S6, and the seventh switch S7 prevents short circuits in AC side bridge arms A and B, improves AC current distortion, and thus enhances the current quality and operational reliability of the converter. Simultaneously, the current ir1 of the first winding flows sequentially through the first winding and the impedance network Z1, then into the midpoint of AC side bridge arm A, and then... After flowing through the body diodes of the sixth switch S6 and the seventh switch S7, the current flows into the midpoint of the bridge arm B on the AC side. This provides a freewheeling path for the current ir1 of the first winding of the transformer Tr, thereby reducing the voltage stress on the AC side bridge arm switches. In the freewheeling circuit, the current of the first winding flows through the body diode of the corresponding switch, thereby achieving zero-voltage turn-on of the switch and reducing the turn-on loss of the switch. In the freewheeling circuit, the current of the first winding can also flow through at least one of the filter capacitor C1 and the AC terminal of the converter.

[0081] As shown in Figure 8D, when switches S3, S4, S5, and S8 are turned on and switches S1, S2, S6, and S7 are turned off, the turn-off of the first switch S1, the second switch S2, the sixth switch S6, and the seventh switch S7 can prevent short circuits in AC side bridge arms A and B, improve AC current distortion, and thus enhance the current quality and operational reliability of the converter. Simultaneously, the current ir1 of the first winding can flow sequentially through the first winding and the impedance network Z1, then into the midpoint of AC side bridge arm A, and then through the body diodes of the sixth switch S6 and the seventh switch S7, before flowing into the midpoint of AC side bridge arm B. This provides a freewheeling path for the current ir1 of the first winding of the transformer Tr, thereby reducing the voltage stress on the AC side bridge arm switches. Furthermore, in the freewheeling circuit, the current of the first winding flows through the body diodes of the corresponding switches, achieving zero-voltage turn-on and reducing the turn-on losses of the switches.

[0082] In an exemplary embodiment, referring to Figures 6, 7A, and 7B, each bidirectional switch in each AC-side bridge arm of the converter is a common-drain series-connected topology. The controller is further configured to, in response to the AC voltage being within a preset zero-crossing range and the current in the first winding flowing into the first winding from the midpoint of the first AC-side bridge arm, control the two switches in the upper bidirectional switch of the first AC-side bridge arm and the two external switches in the second AC-side bridge arm to conduct, or control the two switches in the lower bidirectional switch of the first AC-side bridge arm and the two external switches in the second AC-side bridge arm to conduct. Thus, while avoiding short circuits between AC-side bridge arms A and B, a freewheeling path is provided for the current ir1 in the first winding of the transformer Tr, thereby reducing the voltage stress on the AC-side bridge arm switches. Furthermore, in the freewheeling loop, the current in the first winding flows through the body diode of the corresponding switch, thereby achieving zero-voltage turn-on of the switch and reducing the turn-on losses of the switch.

[0083] In an exemplary embodiment, referring to Figures 6, 7A, and 7B, each bidirectional switch in each AC-side bridge arm of the converter is a common-drain series topology. The controller is further configured to, in response to the AC voltage being within a preset zero-crossing range and the current in the first winding flowing from the first winding into the midpoint of the first AC-side bridge arm, control the two switches in the upper bidirectional switch of the first AC-side bridge arm and the two inner switches in the second AC-side bridge arm to conduct, or control the two switches in the lower bidirectional switch of the first AC-side bridge arm and the two inner switches in the second AC-side bridge arm to conduct. Thus, while avoiding short circuits between AC-side bridge arms A and B, a freewheeling path is provided for the current ir1 in the first winding of the transformer Tr, thereby reducing the voltage stress on the AC-side bridge arm switches. Furthermore, in the freewheeling loop, the current in the first winding flows through the body diode of the corresponding switch, thereby achieving zero-voltage turn-on of the switch and reducing the turn-on loss of the switch.

[0084] In an exemplary embodiment, the switching cycles of the first AC side bridge arm and the second AC side bridge arm can be the same or different. When the switching cycles of the first AC side bridge arm and the second AC side bridge arm are the same, as shown in Figures 7A and 7B. When the switching cycles of the first AC side bridge arm and the second AC side bridge arm are different, referring to Figure 9, the switching cycle of the first AC side bridge arm is longer than that of the second AC side bridge arm. This allows for ensuring a freewheeling path for the current ir1 in the first winding during at least a portion of the switching cycle of the first AC side bridge arm, even when the first AC side bridge arm is not operating.

[0085] In one exemplary embodiment, continuing to refer to FIG9, the switching cycle of the first AC side bridge arm is an even multiple of the switching cycle of the second AC side bridge arm. This allows for the provision of a freewheeling path for the current ir1 in the first winding during at least a portion of the switching cycle of the first AC side bridge arm, even when the first AC side bridge arm remains stationary. Furthermore, the control method for the AC side bridge arms of the converter is simplified. For example, continuing to refer to FIG9, the switching cycle of the first AC side bridge arm is twice the switching cycle of the second AC side bridge arm.

[0086] In an exemplary embodiment, referring to Figures 7A, 7B and 9, for any two complementary conducting switches, each AC side bridge arm is configured with a dead time period during the complementary conduction process of the two switches to avoid bridge arm shoot-through during the complementary conduction process. The size of the dead time period can be a fixed value or a variable value, and there is no specific limitation here.

[0087] In an exemplary embodiment, referring to Figures 7A, 7B, and 9, during the switching cycle of the first AC side bridge arm, the duty cycle of each switch in the first AC side bridge arm is 50%; during the switching cycle of the second AC side bridge arm, the duty cycle of each switch in the second AC side bridge arm is 50%. This not only avoids short circuits between the first and second AC side bridge arms and improves AC current distortion, but also makes the control method for the AC side bridge arms simple, easy to implement, and low-cost.

[0088] In an exemplary embodiment, referring to FIG6, when the AC voltage enters region 3 from region 1, the control method shown in FIG7A or FIG7B can be used in region 3, without limitation; when the AC voltage enters region 3 from region 2, the control method shown in FIG7A or FIG7B can be used in region 3, without limitation; furthermore, the control method in region 3 when the AC voltage enters region 3 from region 1 can be the same as or different from the control method in region 3 when the AC voltage enters region 3 from region 2, without limitation.

[0089] In an exemplary embodiment, a control method for a converter is provided. The converter includes a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter. The two ends of the first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm. Each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm. The topology of each bidirectional switch is the same, and the topology of each bidirectional switch includes two switches connected in series. The switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch.

[0090] The control method includes:

[0091] In response to the AC voltage at the AC terminal being within the zero-crossing preset range, the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch are controlled to conduct complementaryly, and the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch are controlled to conduct complementaryly; and the two switches in the upper bidirectional switch of the second AC side bridge arm are controlled to conduct complementaryly, and the two switches in the lower bidirectional switch of the second AC side bridge arm are controlled to conduct complementaryly.

[0092] Specifically, the two bidirectional switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two bidirectional switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase.

[0093] Furthermore, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two outer switches in the second AC side bridge arm, or the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two inner switches in the second AC side bridge arm.

[0094] The control method of the converter provided in this embodiment belongs to the same inventive concept as the converter in any of the above embodiments, and can solve the same technical problems and achieve the same technical effects. Repeated problems will not be repeated here.

[0095] Based on the same inventive concept, this disclosure also provides a control device for a converter configured to implement the control method of the converter described above. The solution provided by this device is similar to the implementation described in the above method; therefore, specific limitations in one or more converter control device embodiments provided below can be found in the limitations of the converter control method described above, and will not be repeated here.

[0096] In an exemplary embodiment, a control device for a converter is provided. The converter includes a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter. The two ends of the first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm. Each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm. The topology of each bidirectional switch is the same, and the topology of each bidirectional switch includes two switches connected in series. The switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch.

[0097] The control device includes:

[0098] The zero-crossing identification module is configured to determine that the AC voltage at the AC terminal is within a preset zero-crossing range;

[0099] The drive control module is configured to, in response to the AC voltage at the AC terminal being within a preset zero-crossing range, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct complementaryly, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct complementaryly, and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct complementaryly, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct complementaryly.

[0100] Among them, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase.

[0101] Furthermore, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two outer switches in the second AC side bridge arm, or the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase with the two inner switches in the second AC side bridge arm.

[0102] Each module in the control device of the aforementioned converter can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware within or independently of the processor in a computer device, or stored in software within the memory of the computer device, so that the processor can call and execute the operations corresponding to each module.

[0103] In one exemplary embodiment, a controller is provided, including a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the control method of the converter of any of the above embodiments.

[0104] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the control method of the converter of any of the above embodiments.

[0105] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the control method of the converter in any of the above embodiments.

[0106] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the control method of the converter in any of the above embodiments.

[0107] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this disclosure can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this disclosure may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this disclosure may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0108] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this disclosure.

[0109] The above embodiments merely illustrate several implementation methods of this disclosure, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be determined by the appended claims.

Claims

1. A converter, comprising a controller, a transformer, and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter, wherein the two ends of a first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm; each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm; each bidirectional switch has the same topology, and each bidirectional switch has two switches connected in series, wherein the switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch; The controller is configured to, in response to the AC voltage at the AC terminal being within a preset zero-crossing range, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct complementaryly, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct complementaryly, and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct complementaryly, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct complementaryly. in, The two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase. Furthermore, two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the outer switching transistors in the second AC side bridge arm, or two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the inner switching transistors in the second AC side bridge arm.

2. The converter according to claim 1, wherein, The two switching transistors in the bidirectional switching transistor are connected in series with a common source. The controller is also configured to, in response to the AC voltage being within the zero-crossing preset range and the current in the first winding flowing into the first winding from the midpoint of the first AC side bridge arm, control two switches in the upper bidirectional switch of the first AC side bridge arm and two inner switches in the second AC side bridge arm to turn on, or control two switches in the lower bidirectional switch of the first AC side bridge arm and two inner switches in the second AC side bridge arm to turn on.

3. The converter according to claim 2, wherein, The controller is further configured to, in response to the AC voltage being within the zero-crossing preset range and the current of the first winding flowing from the first winding into the midpoint of the first AC side bridge arm, control two switches in the upper bidirectional switch of the first AC side bridge arm and two external switches in the second AC side bridge arm to conduct, or control two switches in the lower bidirectional switch of the first AC side bridge arm and two external switches in the second AC side bridge arm to conduct.

4. The converter according to claim 1, wherein, The two switching transistors in the bidirectional switching transistor are connected in series with a common drain. The controller is further configured to, in response to the AC voltage being within the zero-crossing preset range and the current in the first winding flowing into the first winding from the midpoint of the first AC side bridge arm, control two switches in the upper bidirectional switch of the first AC side bridge arm and two external switches in the second AC side bridge arm to conduct, or control two switches in the lower bidirectional switch of the first AC side bridge arm and two external switches in the second AC side bridge arm to conduct.

5. The converter according to claim 4, wherein, The controller is further configured to, in response to the AC voltage being within the zero-crossing preset range and the current of the first winding flowing from the first winding into the midpoint of the first AC side bridge arm, control two switches in the upper bidirectional switch of the first AC side bridge arm and two inner switches in the second AC side bridge arm to conduct, or control two switches in the lower bidirectional switch of the first AC side bridge arm and two inner switches in the second AC side bridge arm to conduct.

6. The converter according to claim 1, wherein, The controller is further configured to, in response to the AC voltage being within the zero-crossing preset range, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct in a high-frequency complementary manner, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct in a high-frequency complementary manner, and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct in a high-frequency complementary manner, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct in a high-frequency complementary manner. Wherein, the switching frequency of the high-frequency complementary conduction is greater than or equal to 1kHz.

7. The converter according to any one of claims 1-5, wherein, The switching cycle of the first AC side bridge arm is greater than or equal to the switching cycle of the second AC side bridge arm.

8. The converter according to claim 7, wherein, The switching cycle of the first AC side bridge arm is an even multiple of the switching cycle of the second AC side bridge arm.

9. The converter according to claim 7, wherein, During the switching cycle of the first AC side bridge arm, the duty cycle of each switch in the first AC side bridge arm is 50%; During the switching cycle of the second AC side bridge arm, the duty cycle of each switch in the second AC side bridge arm is 50%.

10. The converter according to claim 7, wherein, A dead time period is configured during the complementary conduction of the two switching transistors.

11. A control method for a converter, the converter comprising a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter, wherein the two ends of a first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm; each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm; each bidirectional switch has the same topology, and the topology of each bidirectional switch includes two switches connected in series, wherein the switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch; The control method includes: In response to the AC voltage at the AC terminal being within a preset range of zero crossing, the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch are controlled to conduct complementaryly, and the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch are controlled to conduct complementaryly; and the two switches in the upper bidirectional switch of the second AC side bridge arm are controlled to conduct complementaryly, and the two switches in the lower bidirectional switch of the second AC side bridge arm are controlled to conduct complementaryly. Wherein, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase. Furthermore, two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the outer switching transistors in the second AC side bridge arm, or two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the inner switching transistors in the second AC side bridge arm.

12. The control method according to claim 11, wherein, The two switching transistors in the bidirectional switching transistor are connected in series with a common source. The control method further includes: In response to the AC voltage being within the preset range of the zero crossing point, and the current in the first winding flowing into the first winding from the midpoint of the first AC side bridge arm, the two switches in the upper bidirectional switch of the first AC side bridge arm and the two inner switches in the second AC side bridge arm are controlled to be turned on, or the two switches in the lower bidirectional switch of the first AC side bridge arm and the two inner switches in the second AC side bridge arm are controlled to be turned on.

13. The control method according to claim 12, wherein, The control method further includes: In response to the AC voltage being within the preset range of the zero crossing point, and the current of the first winding flowing from the first winding into the midpoint of the first AC side bridge arm, the two switches in the upper bidirectional switch of the first AC side bridge arm and the two external switches in the second AC side bridge arm are controlled to be turned on, or the two switches in the lower bidirectional switch of the first AC side bridge arm and the two external switches in the second AC side bridge arm are controlled to be turned on.

14. The control method according to claim 11, wherein, The two switching transistors in the bidirectional switching transistor are connected in series with a common drain. The control method further includes: In response to the AC voltage being within the zero-crossing preset range, and the current of the first winding flowing into the first winding from the midpoint of the first AC side bridge arm, the two switches in the upper bidirectional switch of the first AC side bridge arm and the two external switches in the second AC side bridge arm are controlled to be turned on, or the two switches in the lower bidirectional switch of the first AC side bridge arm and the two external switches in the second AC side bridge arm are controlled to be turned on. In response to the AC voltage being within the zero-crossing preset range, and the current of the first winding flowing from the first winding into the midpoint of the first AC side bridge arm, the two switches in the upper bidirectional switch of the first AC side bridge arm and the two inner switches in the second AC side bridge arm are controlled to turn on, or the two switches in the lower bidirectional switch of the first AC side bridge arm and the two inner switches in the second AC side bridge arm are controlled to turn on.

15. A control device for a converter, the converter comprising a transformer and a first AC side bridge arm and a second AC side bridge arm connected in parallel to the AC terminal of the converter, wherein the two ends of a first winding of the transformer are respectively connected to the midpoint of the bridge arm of the first AC side bridge arm and the midpoint of the bridge arm of the second AC side bridge arm; each AC side bridge arm includes an upper bidirectional switch and a lower bidirectional switch connected in series, and the connection point of the upper bidirectional switch and the lower bidirectional switch connected in series is the midpoint of the bridge arm of the AC side bridge arm; each bidirectional switch has the same topology, and the topology of each bidirectional switch includes two switches connected in series, wherein the switch directly connected to the AC terminal is the outer switch, and the switch directly connected to the midpoint of the bridge arm of the AC side bridge arm is the inner switch; The device includes: The zero-crossing identification module is configured to determine that the AC voltage at the AC terminal is within a preset zero-crossing range; The drive control module is configured to, in response to the AC voltage being within the zero-crossing preset range, control the outer switch in the upper bidirectional switch of the first AC side bridge arm and the inner switch in the lower bidirectional switch to conduct complementaryly, and control the inner switch in the upper bidirectional switch of the first AC side bridge arm and the outer switch in the lower bidirectional switch to conduct complementaryly, and control the two switches in the upper bidirectional switch of the second AC side bridge arm to conduct complementaryly, and control the two switches in the lower bidirectional switch of the second AC side bridge arm to conduct complementaryly. Wherein, the two switches in the upper bidirectional switch of the first AC side bridge arm are in phase, the two switches in the lower bidirectional switch of the first AC side bridge arm are in phase, the two outer switches in the second AC side bridge arm are in phase, and the two inner switches in the second AC side bridge arm are in phase. Furthermore, two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the outer switching transistors in the second AC side bridge arm, or two of the upper bidirectional switching transistors in the first AC side bridge arm are in phase with two of the inner switching transistors in the second AC side bridge arm.

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