A direct current-direct current (DC-DC) converter and a control method thereof

Abstract

The application provides a DC-DC converter and a control method thereof. The DC-DC converter comprises at least one DC-DC conversion module and a controller. Each DC-DC conversion module comprises two bidirectional isolation DC-DC units connected in parallel. Each bidirectional isolation DC-DC unit comprises a resonant circuit and a non-isolation step-down / step-up circuit. The resonant circuit and the non-isolation step-down / step-up circuit are connected in cascade. The working frequency of each resonant circuit is fixed. If the number of DC-DC conversion modules is greater than or equal to 2, each DC-DC conversion module is connected in parallel. The controller is electrically connected with each bidirectional isolation DC-DC unit. The controller is used for controlling the current sharing of each non-isolation step-down / step-up circuit. The method is used for the DC-DC converter. The DC-DC converter and the control method thereof provided by the application reduce the manufacturing cost of the DC-DC converter.

Description

Technical Field

[0001] This application relates to the field of power electronic equipment technology, specifically to a DC-DC converter and its control method. Background Technology

[0002] With the increasing popularity of new energy vehicles, the demand for home DC charging piles is growing, and the power requirements for charging piles are also increasing.

[0003] Bidirectional converters can be configured in charging piles. These converters not only charge electric vehicles but also allow the electric vehicle batteries to be used as emergency power. When electricity prices are low, electric vehicles can be charged; during power outages caused by earthquakes, typhoons, or other disasters, the electric vehicle batteries can be used as emergency power to supply household appliances; and during periods of high electricity prices, they can be connected to the grid for power generation. The bidirectional converter is a crucial component of bidirectional charging equipment, significantly impacting the overall performance of the system. Current technologies, to increase the power of the bidirectional converter, connect multiple transformer windings in series, leading to complex transformer manufacturing, implementation difficulties, and high production costs. Summary of the Invention

[0004] To address the issue that higher power bidirectional converters lead to higher transformer manufacturing costs, this application provides a bidirectional isolated DC-DC converter and its control method, which can at least partially solve the above-mentioned problem.

[0005] On the one hand, this application proposes a DC-to-DC DC-DC converter, including at least one DC-DC conversion module and a controller, wherein:

[0006] Each DC-DC converter module includes two parallel bidirectional isolated DC-DC units, and each bidirectional isolated DC-DC unit includes a resonant circuit and a non-isolated buck / boost circuit, wherein the resonant circuit and the non-isolated buck / boost circuit are cascaded; wherein the operating frequency of each resonant circuit is fixed; if the number of DC-DC converter modules is greater than or equal to 2, the DC-DC converter modules are connected in parallel.

[0007] The controller is electrically connected to each of the bidirectional isolated DC-DC units, and the controller is used to control the current sharing of each of the non-isolated buck / boost circuits.

[0008] Furthermore, the resonant circuit includes a three-phase LLC circuit or an LLC extension circuit.

[0009] Furthermore, the three-phase LLC circuit includes a first three-phase circuit, a second three-phase circuit, and three transformers, wherein:

[0010] The first three-phase circuit is connected to the primary side of the three transformers, and the second three-phase circuit is connected to the secondary side of the three transformers.

[0011] Further, the first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, and a third capacitor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the first inductor is connected between the first switch and the second switch, the first terminal of the second inductor is connected between the third switch and the fourth switch, and the first terminal of the third inductor is connected to the first switch. Between the fifth switching transistor and the sixth switching transistor; the second terminal of the first inductor is connected to the first terminal of the primary side of the first transformer, the second terminal of the primary side of the first transformer is connected to the first terminal of the first capacitor, the second terminal of the second inductor is connected to the first terminal of the primary side of the second transformer, the second terminal of the primary side of the second transformer is connected to the first terminal of the second capacitor, the second terminal of the third inductor is connected to the first terminal of the primary side of the third transformer, the second terminal of the primary side of the third transformer is connected to the first terminal of the third capacitor, and the second terminals of the first capacitor, the second capacitor, and the third capacitor are connected; or,

[0012] The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first capacitor, a second capacitor, and a third capacitor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the primary side of the first transformer is connected between the first switch and the second switch, the first terminal of the primary side of the second transformer is connected between the third switch and the fourth switch, and the first terminal of the primary side of the third transformer is connected between the fifth switch and the sixth switch; the second terminal of the primary side of the first transformer is connected to the first terminal of the first capacitor, the second terminal of the primary side of the second transformer is connected to the first terminal of the second capacitor, and the second terminal of the primary side of the third transformer is connected to the first terminal of the third capacitor; the second terminals of the first capacitor, the second capacitor, and the third capacitor are connected together; or,

[0013] The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first inductor, a second inductor, and a third inductor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the first inductor is connected between the first switch and the second switch, the first terminal of the second inductor is connected between the third switch and the fourth switch, and the first terminal of the third inductor is connected between the fifth switch and the sixth switch; the second terminal of the first inductor is connected to the first terminal of the primary winding of the first transformer, the second terminal of the second inductor is connected to the first terminal of the primary winding of the second transformer, and the second terminal of the third inductor is connected to the first terminal of the primary winding of the third transformer; the second terminals of the primary windings of the first transformer, the second terminals of the primary windings of the second transformer, and the second terminals of the primary windings of the third transformer are connected; or,

[0014] The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, and a sixth switch; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first end of the primary side of the first transformer is connected between the first switch and the second switch, the first end of the primary side of the second transformer is connected between the third switch and the fourth switch, and the first end of the third transformer is connected between the fifth switch and the sixth switch; the second ends of the primary sides of the first transformer, the second ends of the primary sides of the second transformer, and the second ends of the primary sides of the third transformer are connected together.

[0015] Further, the second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth inductor, a fifth inductor, a sixth inductor, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected to the first terminal of the fourth inductor, and the second terminal of the fourth inductor is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected to the fifth inductor... The first terminal is connected, and the second terminal of the fifth inductor is connected between the ninth and tenth switching transistors; the first terminal of the secondary side of the third transformer is connected to the first terminal of the sixth inductor, and the second terminal of the sixth inductor is connected between the eleventh and twelfth switching transistors; the second terminal of the secondary side of the first transformer is connected to the first terminal of the fourth capacitor, the second terminal of the secondary side of the second transformer is connected to the first terminal of the fifth capacitor, the second terminal of the secondary side of the third transformer is connected to the first terminal of the sixth capacitor, and the second terminals of the fourth, fifth, and sixth capacitors are connected together; or,

[0016] The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected between the ninth and tenth switches; the first terminal of the secondary side of the third transformer is connected between the eleventh and twelfth switches; the second terminal of the secondary side of the first transformer is connected to the first terminal of the fourth capacitor, the second terminal of the secondary side of the second transformer is connected to the first terminal of the fifth capacitor, the second terminal of the secondary side of the third transformer is connected to the first terminal of the sixth capacitor, and the second terminals of the fourth, fifth, and sixth capacitors are connected together; or,

[0017] The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth inductor, a fifth inductor, and a sixth inductor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected to the first terminal of the fourth inductor, and the second terminal of the fourth inductor is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected to the first terminal of the fifth inductor, and the second terminal of the fifth inductor is connected between the ninth and tenth switches; the first terminal of the secondary side of the third transformer is connected to the first terminal of the sixth inductor, and the second terminal of the sixth inductor is connected between the eleventh and twelfth switches; the second terminals of the secondary sides of the first transformer, the second terminals of the secondary sides of the second transformer, and the second terminals of the secondary sides of the third transformer are connected; or,

[0018] The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, and a twelfth switch. The seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series. The first end of the secondary side of the first transformer is connected between the seventh and eighth switches, the first end of the secondary side of the second transformer is connected between the ninth and tenth switches, and the first end of the secondary side of the third transformer is connected between the eleventh and twelfth switches. The second ends of the secondary sides of the first transformer, the second ends of the secondary sides of the second transformer, and the second ends of the secondary sides of the third transformer are connected together.

[0019] Furthermore, the non-isolated buck / boost circuit adopts an interleaved boost / buck circuit or a single-stage boost / buck circuit.

[0020] Furthermore, the non-isolated buck / boost circuit includes a first branch, a second branch, a seventh inductor, and an eighth inductor, wherein:

[0021] The first branch and the second branch are connected in parallel. The first branch includes a thirteenth switch and a fourteenth switch connected in series, and the second branch includes a fifteenth switch and a sixteenth switch connected in series. The first end of the seventh inductor is connected to the second end of the fifteenth switch and the first end of the sixteenth switch. The first end of the eighth inductor is connected to the second end of the thirteenth switch and the first end of the fourteenth switch. The second end of the seventh inductor and the second end of the eighth inductor are connected.

[0022] On the other hand, this application provides a bidirectional charging and discharging device, including the DC-to-DC converter described in any of the above embodiments.

[0023] Furthermore, this application provides a control method for a DC-to-DC converter using any of the above embodiments, comprising:

[0024] When running in the first direction, the corresponding positions of the two resonant circuits included in each DC-DC converter module are driven in opposite directions, and each non-isolated buck / boost circuit is controlled to operate in buck mode and make the output current of each non-isolated buck / boost circuit equal.

[0025] When operating in the second direction, the driving positions of the corresponding positions of the two resonant circuits included in each DC-DC converter module are reversed, and each non-isolated buck / boost circuit is controlled to operate in a DC boost state and make the output current of each non-isolated buck / boost circuit equal; the operation in the first direction is the opposite of the operation in the second direction.

[0026] Furthermore, controlling each non-isolated buck / boost circuit to operate in buck mode and ensuring that the output currents of each non-isolated buck / boost circuit are equal includes:

[0027] A first current reference value is generated based on a preset voltage reference value and an output voltage sampling value. The duty cycle of each non-isolated buck / boost circuit is adjusted based on the first current reference value and the output current sampling value of each non-isolated buck / boost circuit so that the output current of each non-isolated buck / boost circuit is equal.

[0028] Furthermore, controlling each non-isolated buck / boost circuit to operate in a DC boost state and ensuring that the output currents of each non-isolated buck / boost circuit are equal includes:

[0029] Each non-isolated buck / boost circuit is controlled to generate the intermediate bus voltage of each bidirectional isolated DC-DC unit, and a second current reference value is obtained based on the intermediate bus voltage reference value and the sampled intermediate bus voltage value of each bidirectional isolated DC-DC unit.

[0030] The duty cycle of each non-isolated buck / boost circuit is adjusted based on the second current reference value and the input current sampling value of each non-isolated buck / boost circuit so that the input current of each non-isolated buck / boost circuit is equal.

[0031] The DC-to-DC converter and its control method provided in this application include at least one DC-DC converter module and a controller. Each DC-DC converter module includes two parallel bidirectional isolated DC-DC units. Each bidirectional isolated DC-DC unit includes a resonant circuit and a non-isolated buck / boost circuit. The resonant circuit and the non-isolated buck / boost circuit are cascaded. The controller is electrically connected to each bidirectional isolated DC-DC unit and is used to control the current sharing of each non-isolated buck / boost circuit. The power requirements of the DC-to-DC converter are met by at least one DC-DC converter module, thereby reducing the manufacturing cost of the DC-to-DC converter. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0033] Figure 1 This is a schematic diagram of the DC-to-DC converter provided in the first embodiment of this application.

[0034] Figure 2 This is a schematic diagram of the DC-to-DC converter provided in the second embodiment of this application.

[0035] Figure 3 This is a schematic diagram of the DC-to-DC converter provided in the third embodiment of this application.

[0036] Figure 4 This is a schematic diagram of the structure of the first three-phase circuit provided in the fourth embodiment of this application.

[0037] Figure 5 This is a schematic diagram of the structure of the first three-phase circuit provided in the fifth embodiment of this application.

[0038] Figure 6 This is a schematic diagram of the structure of the first three-phase circuit provided in the sixth embodiment of this application.

[0039] Figure 7 This is a schematic diagram of the structure of the first three-phase circuit provided in the seventh embodiment of this application.

[0040] Figure 8 This is a schematic diagram of the structure of the second three-phase circuit provided in the eighth embodiment of this application.

[0041] Figure 9 This is a schematic diagram of the structure of the second three-phase circuit provided in the ninth embodiment of this application.

[0042] Figure 10 This is a schematic diagram of the structure of the second three-phase circuit provided in the tenth embodiment of this application.

[0043] Figure 11 This is a schematic diagram of the structure of the second three-phase circuit provided in the eleventh embodiment of this application.

[0044] Figure 12 This is a schematic diagram of the non-isolated buck / boost circuit provided in the twelfth embodiment of this application.

[0045] Figure 13 This is a schematic diagram of the DC-to-DC converter provided in the thirteenth embodiment of this application.

[0046] Figure 14 This is a flowchart illustrating the control method for a DC-to-DC converter provided in the fourth embodiment of this application.

[0047] Figure 15 This is a control diagram of the first direction of operation provided in the fifteenth embodiment of this application.

[0048] Figure 16 This is a control diagram of second-direction operation provided in the sixteenth embodiment of this application.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. DC-DC converter module; 11. Bidirectional isolated DC-DC unit;

[0051] 111. Resonant circuit; 112. Non-isolated buck / boost circuit;

[0052] 310. First three-phase circuit; 320. Second three-phase circuit;

[0053] 330, First Branch Road; 340, Second Branch Road. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain this application, but are not intended to limit this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0055] Figure 1 This is a schematic diagram of the DC-to-DC converter provided in the first embodiment of this application, as shown below. Figure 1As shown, the DC-DC converter provided in this application includes at least one DC-DC conversion module 1 and a controller, wherein:

[0056] Each DC-DC converter module 1 includes two bidirectional isolated DC-DC units 11, which are connected in parallel. Each bidirectional isolated DC-DC unit includes a resonant circuit 111 and a non-isolated buck / boost circuit 112, which are cascaded. The operating frequency of each resonant circuit 111 is fixed. If the number of DC-DC converter modules 1 is greater than or equal to 2, the DC-DC converter modules 1 are connected in parallel.

[0057] The controller is electrically connected to each bidirectional isolated DC-DC unit 11 and is used to control the current sharing of each non-isolated buck / boost circuit 112.

[0058] Specifically, the DC-to-DC converter provided in this application embodiment can achieve bidirectional power flow. That is, the DC-to-DC converter can charge a connected charging object (operating in charging mode) and can output the stored electrical energy of the charging object to the outside (operating in power supply mode). When operating in charging mode, external current flows from the resonant circuit 111 to the non-isolated buck / boost circuit 112 to charge the charging object. The resonant circuit 111 is used for boosting the voltage, and the non-isolated buck / boost circuit 112 is used for bucking the voltage. The DC-to-DC converter operates in the first direction. When operating in power supply mode, the current supplied by the charging object flows from the non-isolated buck / boost circuit 112 to the resonant circuit 111 and is then output to the outside. In this case, the non-isolated buck / boost circuit 112 is used for boosting the voltage, and the resonant circuit 111 is used for bucking the voltage. The DC-to-DC converter operates in the second direction. In practical use, the current can be connected to a power factor correction (PFC) circuit via the resonant circuit 111, and a rechargeable battery via the non-isolated buck / boost circuit 112.

[0059] The controller is used to drive each bidirectional isolated DC-DC unit and each non-isolated buck / boost circuit 112. The controller reduces electromagnetic interference (EMI) noise in the DC-to-DC converter by controlling the driving of corresponding positions of the two resonant circuits included in each DC-DC conversion module to be opposite. The controller controls the output current of each non-isolated buck / boost circuit to be equal, achieving current sharing among the non-isolated buck / boost circuits 112. Voltage isolation of each resonant circuit 111 is achieved by fixing the operating frequency of each resonant circuit 111. The controller can be a microcontroller unit (MCU) or a digital signal processing (DSP) chip.

[0060] The power of the DC-DC converter can be expanded by increasing the number of DC-DC converter modules 1. The more DC-DC converter modules 1 there are, the greater the power that can be supported. The number of DC-DC converter modules 1 is set according to the actual power requirements, such as setting 2-10 DC-DC converter modules 1. This is only an example for illustration, and the embodiments of this application do not impose too much limitation on the number of DC-DC converter modules 1.

[0061] like Figure 2 As shown, the DC-to-DC converter provided in this application includes two DC-DC conversion modules 1, which are connected in parallel. Figure 1 The structure shown includes one DC-DC converter module 1, which improves the power of the DC-DC converter.

[0062] The DC-to-DC converter provided in this application includes at least one DC-DC converter module and a controller. Each DC-DC converter module includes two parallel bidirectional isolated DC-DC units. Each bidirectional isolated DC-DC unit includes a resonant circuit and a non-isolated buck / boost circuit. The resonant circuit and the non-isolated buck / boost circuit are cascaded. The controller is electrically connected to each bidirectional isolated DC-DC unit and is used to control the current sharing of each non-isolated buck / boost circuit. The power requirements of the DC-to-DC converter are met by at least one DC-DC converter module, avoiding the use of complex transformer structures and reducing the manufacturing cost of the DC-to-DC converter.

[0063] Based on the above embodiments, the resonant circuit 111 further includes a three-phase LLC circuit or an LLC extension circuit. The input-output ripple of the three-phase LLC circuit is relatively small. The LLC extension circuit is a three-phase resonant circuit that is modified or improved based on the above three-phase LLC circuit.

[0064] Figure 3 This is a schematic diagram of the DC-to-DC converter provided in the third embodiment of this application, as shown below. Figure 3 As shown, based on the above embodiments, the three-phase LLC circuit further includes a first three-phase circuit 310, a second three-phase circuit 320, and three transformers, wherein:

[0065] The first three-phase circuit 310 is connected to the primary side of the three transformers, and the second three-phase circuit 320 is connected to the secondary side of the three transformers. The second three-phase circuit 320 is connected to the non-isolated buck / boost circuit 112.

[0066] The first three-phase circuit 310 can be adopted Figure 3 , Figure 4 , Figure 5 or Figure 6 The circuit structure shown, or other three-phase circuits that add or remove electronic components such as inductors, capacitors, resistors, and switching transistors based on the first three-phase circuit described above, are not subject to further restrictions here. The second three-phase circuit 320 can adopt... Figure 7 , Figure 8 , Figure 9 or Figure 10 The circuit structure shown, or other three-phase circuits that add or remove electronic components such as inductors, capacitors, resistors, and switching transistors based on the second and three-phase circuits in the above figures, are not subject to further restrictions here.

[0067] Figure 4 This is a schematic diagram of the structure of the first three-phase circuit provided in the fourth embodiment of this application, as shown below. Figure 4As shown, based on the above embodiments, the first three-phase circuit 310 further includes a first switch M1, a second switch M2, a third switch M3, a fourth switch M4, a fifth switch M5, a sixth switch M6, a first inductor L1, a second inductor L2, a third inductor L3, a first capacitor C1, a second capacitor C2, and a third capacitor C3; the first switch M1 and the second switch M2 are connected in series, the third switch M3 and the fourth switch M4 are connected in series, and the fifth switch M5 and the sixth switch M6 are connected in series; the first end of the first inductor L1 is connected between the first switch M1 and the second switch M2, the first end of the second inductor L2 is connected between the third switch M3 and the fourth switch M4, and the first end of the third inductor L3 is connected between the fifth switch M5 and the sixth switch M6; the first inductor L1... The second terminal of inductor L1 is connected to the first terminal of the primary winding of transformer T1. The second terminal of the primary winding of transformer T1 is connected to the first terminal of capacitor C1. The second terminal of inductor L2 is connected to the first terminal of the primary winding of transformer T2. The second terminal of the primary winding of transformer T2 is connected to the first terminal of capacitor C2. The second terminal of inductor L3 is connected to the first terminal of the primary winding of transformer T3. The second terminal of the primary winding of transformer T3 is connected to the first terminal of capacitor C3. The second terminals of capacitors C1, C2, and C3 are connected. The first terminals of switching transistors M1, M3, and M5 are connected. The second terminals of switching transistors M2, M4, and M6 are connected.

[0068] Figure 5 This is a schematic diagram of the structure of the first three-phase circuit provided in the fifth embodiment of this application, as shown below. Figure 5As shown, based on the above embodiments, the first three-phase 210 circuit further includes a first switch M1, a second switch M2, a third switch M3, a fourth switch M4, a fifth switch M5, a sixth switch M6, a first capacitor C1, a second capacitor C2, and a third capacitor C3; the first switch M1 and the second switch M2 are connected in series, the third switch M3 and the fourth switch M4 are connected in series, and the fifth switch M5 and the sixth switch M6 are connected in series; the first end of the primary side of the first transformer T1 is connected between the first switch M1 and the second switch M2. The first end of the primary side of the second transformer T2 is connected between the third switch M3 and the fourth switch M4, and the first end of the primary side of the third transformer T3 is connected between the fifth switch M5 and the sixth switch M6; the second end of the primary side of the first transformer T1 is connected to the first end of the first capacitor C1, the second end of the primary side of the second transformer T2 is connected to the first end of the second capacitor C2, the second end of the primary side of the third transformer T3 is connected to the first end of the third capacitor C3, and the second ends of the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected together.

[0069] Figure 6 This is a schematic diagram of the structure of the first three-phase circuit provided in the sixth embodiment of this application, as shown below. Figure 6 As shown, based on the above embodiments, the first three-phase circuit 310 further includes a first switch M1, a second switch M2, a third switch M3, a fourth switch M4, a fifth switch M5, a sixth switch M6, a first inductor L1, a second inductor L2, and a third inductor L3; the first switch M1 and the second switch M2 are connected in series, the third switch M3 and the fourth switch M4 are connected in series, and the fifth switch M5 and the sixth switch M6 are connected in series; the first end of the first inductor L1 is connected between the first switch M1 and the second switch M2, and the second inductor L3... The first end of L2 is connected between the third switch M3 and the fourth switch M4, and the first end of the third inductor L3 is connected between the fifth switch M5 and the sixth switch M6; the second end of the first inductor L1 is connected to the first end of the primary side of the first transformer T1, the second end of the second inductor L2 is connected to the first end of the primary side of the second transformer T2, and the second end of the third inductor L3 is connected to the first end of the primary side of the third transformer T3; the second ends of the primary sides of the first transformer T1, the second ends of the primary sides of the second transformer T2, and the second ends of the primary sides of the third transformer T3 are connected together.

[0070] Figure 7 This is a schematic diagram of the structure of the first three-phase circuit provided in the seventh embodiment of this application, as shown below. Figure 7As shown, based on the above embodiments, the first three-phase circuit further includes a first switch M1, a second switch M2, a third switch M3, a fourth switch M4, a fifth switch M5, and a sixth switch M6; the first switch M1 and the second switch M2 are connected in series, the third switch M3 and the fourth switch M4 are connected in series, and the fifth switch M5 and the sixth switch M6 are connected in series; the first end of the primary side of the first transformer T1 is connected between the first switch M1 and the second switch M2, the first end of the primary side of the second transformer T2 is connected between the third switch M3 and the fourth switch M4, and the first end of the third transformer T3 is connected between the fifth switch M5 and the sixth switch M6; the second ends of the primary sides of the first transformer T1, the second ends of the primary sides of the second transformer T2, and the second ends of the primary sides of the third transformer T3 are connected.

[0071] Figure 8 This is a schematic diagram of the second three-phase circuit provided in the eighth embodiment of this application, as shown below. Figure 8 As shown, based on the above embodiments, the second three-phase circuit 320 further includes a seventh switch M7, an eighth switch M8, a ninth switch M9, a tenth switch M10, an eleventh switch M11, a twelfth switch M12, a fourth inductor L4, a fifth inductor L5, a sixth inductor L6, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6; the seventh switch M7 and the eighth switch M8 are connected in series, the ninth switch M9 and the tenth switch M10 are connected in series, and the eleventh switch M11 and the twelfth switch M12 are connected in series; the first terminal of the secondary side of the first transformer T1 is connected to the first terminal of the fourth inductor L4, and the second terminal of the fourth inductor L4 is connected between the seventh switch M7 and the eighth switch M8. The first terminal of the secondary side of the second transformer T2 is connected to the first terminal of the fifth inductor L5, and the first terminal of the fifth inductor L5 is connected between the ninth switch M9 and the tenth switch M10; the first terminal of the secondary side of the third transformer T3 is connected to the first terminal of the sixth inductor L6, and the second terminal of the sixth inductor L6 is connected between the eleventh switch M11 and the twelfth switch M12; the second terminal of the secondary side of the first transformer T1 is connected to the first terminal of the fourth capacitor C4; the second terminal of the secondary side of the second transformer T2 is connected to the first terminal of the fifth capacitor C5; the second terminal of the secondary side of the third transformer T3 is connected to the first terminal of the sixth capacitor C6; and the second terminals of the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 are connected together.

[0072] Figure 9 This is a schematic diagram of the structure of the second three-phase circuit provided in the ninth embodiment of this application, as shown below. Figure 9As shown, based on the above embodiments, the second three-phase circuit 320 further includes a seventh switch M7, an eighth switch M8, a ninth switch M9, a tenth switch M10, an eleventh switch M11, a twelfth switch M12, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6; the seventh switch M7 and the eighth switch M8 are connected in series, the ninth switch M9 and the tenth switch M10 are connected in series, and the eleventh switch M11 and the twelfth switch M12 are connected in series; the first terminal of the secondary side of the first transformer T1 is connected to the seventh switch M7 and the eighth switch M8. Between; the first end of the secondary side of the second transformer T2 is connected between the ninth switch M9 and the tenth switch M10; the first end of the secondary side of the third transformer T3 is connected between the eleventh switch M11 and the twelfth switch M12; the second end of the secondary side of the first transformer T1 is connected to the first end of the fourth capacitor C4; the second end of the secondary side of the second transformer T2 is connected to the first end of the fifth capacitor C5; the second end of the secondary side of the third transformer T3 is connected to the first end of the sixth capacitor C6; the second ends of the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 are connected together.

[0073] Figure 10 This is a schematic diagram of the structure of the second three-phase circuit provided in the tenth embodiment of this application, as shown below. Figure 10 As shown, based on the above embodiments, the second three-phase circuit 320 further includes a seventh switch M7, an eighth switch M8, a ninth switch M9, a tenth switch M10, an eleventh switch M11, a twelfth switch M12, a fourth inductor L4, a fifth inductor L5, and a sixth inductor L6; the seventh switch M7 and the eighth switch M8 are connected in series, the ninth switch M9 and the tenth switch M10 are connected in series, and the eleventh switch M11 and the twelfth switch M12 are connected in series; the first terminal of the secondary side of the first transformer T1 is connected to the first terminal of the fourth inductor L4, and the fourth inductor... The second terminal of L4 is connected between the seventh switch M7 and the eighth switch M8; the first terminal of the secondary side of the second transformer T2 is connected to the first terminal of the fifth inductor L5, and the first terminal of the fifth inductor L5 is connected between the ninth switch M9 and the tenth switch M10; the first terminal of the secondary side of the third transformer T3 is connected to the first terminal of the sixth inductor L6, and the second terminal of the sixth inductor L6 is connected between the eleventh switch M11 and the twelfth switch M12; the second terminals of the secondary sides of the first transformer T1, the second terminals of the secondary sides of the second transformer T1, and the second terminals of the secondary sides of the third transformer T3 are connected.

[0074] Figure 11 This is a schematic diagram of the structure of the second three-phase circuit provided in the eleventh embodiment of this application, as shown below. Figure 11As shown, based on the above embodiments, the second three-phase circuit 320 further includes a seventh switch M7, an eighth switch M8, a ninth switch M9, a tenth switch M10, an eleventh switch M11, and a twelfth switch M12. The seventh switch M7 and the eighth switch M8 are connected in series, the ninth switch M9 and the tenth switch M10 are connected in series, and the eleventh switch M11 and the twelfth switch M12 are connected in series. The first end of the secondary side of the first transformer T1 is connected between the seventh switch M7 and the eighth switch M8, the first end of the secondary side of the second transformer T2 is connected between the ninth switch M9 and the tenth switch M10, and the first end of the secondary side of the third transformer T3 is connected between the eleventh switch M11 and the twelfth switch M12. The second ends of the secondary sides of the first transformer T1, the second ends of the secondary sides of the second transformer T2, and the second ends of the secondary sides of the third transformer T3 are connected together.

[0075] Based on the above embodiments, the non-isolated buck / boost circuit 112 further adopts an interleaved boost / buck circuit or a single-stage boost / buck circuit.

[0076] Based on the above embodiments, further, such as Figure 12 As shown, the non-isolated buck / boost circuit 112 includes a first branch 330, a second branch 340, a seventh inductor L7, and an eighth inductor L8, wherein:

[0077] The first branch 330 and the second branch 340 are connected in parallel. The first branch 330 includes a thirteenth switch M13 and a fourteenth switch M14 connected in series. The second branch 340 includes a fifteenth switch M15 and a sixteenth switch M16 connected in series. The first terminal of the seventh inductor L7 is connected to the second terminal of the fifteenth switch M15 and the first terminal of the sixteenth switch M16. The first terminal of the eighth inductor L8 is connected to the second terminal of the thirteenth switch M13 and the first terminal of the fourteenth switch M14. The second terminal of the seventh inductor L7 and the second terminal of the eighth inductor are connected together. The first branch 330 and the second branch 340 are respectively connected to the resonant circuit 111.

[0078] like Figure 3 As shown, the first three-phase circuit 310 adopts... Figure 3 The circuit structure shown uses the second three-phase circuit 320. Figure 11 The circuit structure shown employs a non-isolated buck / boost circuit 112. Figure 12 The circuit structure shown is shown.

[0079] A first filter capacitor C7 and a second filter capacitor C8 can be installed at the external port of the first three-phase circuit 310. The first filter capacitor C7 and the second filter capacitor C8 are connected in series. The first end of the first filter capacitor C7 is connected to the first end of the external port of the first three-phase circuit 310, and the second end of the first filter capacitor C7 is connected to the first end of the second filter capacitor C8. The second end of the second filter capacitor C8 is connected to the second end of the external port of the first three-phase circuit 310. The first ends of the first switch M1, the third switch M3, and the fifth switch M5 are connected to the first end of the external port of the first three-phase circuit 310. The second ends of the second switch M2, the fourth switch M4, and the sixth switch M6 are connected to the external port of the first three-phase circuit 310.

[0080] The drives of the first switch M1 and the second switch M2 are complementary, the drives of the third switch M3 and the fourth switch M4 are complementary, the drives of the fifth switch M5 and the sixth switch M6 are complementary, and the drives of the first bridge arm to which the first switch M1 and the second switch M2 belong, the second bridge arm to which the third switch M3 and the fourth switch M4 belong, and the third bridge arm to which the fifth switch M5 and the sixth switch M6 belong, are 120 degrees apart.

[0081] The drives of the seventh switch M7 and the eighth switch M8 are complementary; the drives of the ninth switch M9 and the tenth switch M10 are complementary; the drives of the eleventh switch M11 and the twelfth switch M12 are complementary; the drives of the same position of the fourth bridge arm to which the seventh switch M7 and the eighth switch M8 belong, the fifth bridge arm to which the ninth switch M9 and the tenth switch M10 belong, and the sixth bridge arm to which the eleventh switch M11 and the twelfth switch M12 belong, are 120 degrees apart.

[0082] In this circuit, a third filter capacitor C9 can be installed at the external port of the non-isolated buck / boost circuit 112. The first terminal of the third filter capacitor C9 is connected to the second terminals of the seventh inductor L7 and the eighth inductor L8, respectively. The second terminal of the third filter capacitor C9 is connected to the second terminals of the fourteenth switch M14 and the sixteenth switch M16, respectively. The second terminal of the external port of the non-isolated buck / boost circuit 112 is connected to the second terminal of the third filter capacitor C9, the second terminal of the seventh inductor L7, and the second terminal of the eighth inductor L8, respectively. Figure 3 The non-isolated buck / boost circuit 112 is an interleaved boost / buck circuit.

[0083] A first bus capacitor C10 is provided between the second three-phase circuit 320 and the non-isolated buck / boost circuit 112. The voltage across the first bus capacitor can be called the intermediate bus voltage. When operating in the first direction, the intermediate bus voltage is the output voltage of the resonant circuit 111. When operating in the second direction, the intermediate bus voltage is the output voltage of the non-isolated buck / boost circuit 112. The first bus capacitor C10 is connected in parallel with the second three-phase circuit 320. The first terminal of the first bus capacitor C10 is connected to the first terminal of the seventh switch M7, the first terminal of the ninth switch M9, and the first terminal of the eleventh switch M11, respectively. The second terminal of the first bus capacitor C10 is connected to the second terminal of the eighth switch M8, the second terminal of the tenth switch M10, and the second terminal of the twelfth switch M12, respectively.

[0084] like Figure 13 As shown, the first three-phase circuit 310 adopts... Figure 5 The circuit structure shown uses the second three-phase circuit 320. Figure 11 The circuit structure shown is shown.

[0085] The non-isolated buck / boost circuit 112 includes a seventeenth switch M17, an eighteenth switch M18, and a ninth inductor L9, wherein:

[0086] The seventeenth switch M17 and the eighteenth switch M18 are connected in series. The second terminal of the seventeenth switch M17 is connected to the first terminal of the eighteenth switch M18. The first terminal of the ninth inductor L9 is connected to the second terminal of the seventeenth switch M17 and the first terminal of the eighteenth switch M18. The first terminals of the seventeenth switch M17 and the eighteenth switch M18 are connected to the second three-phase circuit 320.

[0087] A fourth filter capacitor C10 can be installed at the external port of the non-isolated buck / boost circuit 112. The first terminal of the fourth filter capacitor C10 is connected to the second terminal of the ninth inductor L9, and the second terminal of the fourth filter capacitor C10 is connected to the second terminal of the eighteenth switch M18. The first terminal of the external port of the non-isolated buck / boost circuit 112 is connected to the second terminal of the ninth inductor L9 and the first terminal of the fourth filter capacitor C10, respectively. The second terminal of the external port of the non-isolated buck / boost circuit 112 is connected to the second terminal of the fourth filter capacitor C10 and the second terminal of the eighteenth switch M18, respectively. Figure 13 The Sino-African isolated buck / boost circuit 112 is a single-stage boost / buck circuit.

[0088] like Figure 13As shown, a second bus capacitor C11 is provided between the second three-phase circuit 320 and the non-isolated buck / boost circuit 112. The voltage across the second bus capacitor C11 can be called the intermediate bus voltage. The second bus capacitor C11 is connected in parallel with the second three-phase circuit 320. The first terminal of the second bus capacitor C11 is connected to the first terminal of the seventh switch M7, the first terminal of the ninth switch M9, and the first terminal of the eleventh switch M11, respectively. The second terminal of the second bus capacitor C11 is connected to the second terminal of the eighth switch M8, the second terminal of the tenth switch M10, and the second terminal of the twelfth switch M12, respectively.

[0089] This application provides a bidirectional charging and discharging device, including the DC-to-DC converter described in any of the above embodiments. The bidirectional charging and discharging device can be applied to charging piles.

[0090] Figure 14 This is a flowchart illustrating the control method for a DC-to-DC converter provided in the fourteenth embodiment of this application, as shown below. Figure 14 As shown, the control method for the DC-to-DC converter provided in this application embodiment can be applied to the DC-to-DC converter described in any of the above embodiments, including:

[0091] S1401. When running in the first direction, the driving positions of the corresponding positions of the two resonant circuits included in each DC-DC converter module are reversed, and each non-isolated buck / boost circuit is controlled to work in buck mode and the output current of each non-isolated buck / boost circuit is equal.

[0092] Specifically, when the DC-to-DC converter operates in charging mode, i.e., in the first direction, current flows from each resonant circuit to the cascaded non-isolated buck / boost circuits. The controller drives each resonant circuit to step down the input voltage to obtain the intermediate bus voltage. Simultaneously, it controls the corresponding positions of the two resonant circuits in each DC-DC converter module to drive in opposite directions to reduce EMI noise. The controller also drives each non-isolated buck / boost circuit to operate in buck mode, reducing the intermediate bus voltage output. Furthermore, it controls the output current of each non-isolated buck / boost circuit to be equal, achieving current sharing among the circuits.

[0093] S1402, when running in the second direction, the driving positions of the corresponding positions of the two resonant circuits included in each DC-DC converter module are reversed, and each non-isolated buck / boost circuit is controlled to operate in a DC boost state and the output current of each non-isolated buck / boost circuit is equal; wherein, the first direction is opposite to the second direction.

[0094] Specifically, when the DC-to-DC converter operates in power supply mode, i.e., in the second direction, current flows from each non-isolated buck / boost circuit to the cascaded resonant circuit. The controller drives each non-isolated buck / boost circuit to operate in buck mode, reducing the input voltage to obtain the intermediate bus voltage. Simultaneously, it controls the output current of each non-isolated buck / boost circuit to be equal, achieving current sharing among them. The controller drives each resonant circuit to output the intermediate bus voltage while simultaneously controlling the driving positions of the corresponding positions of the two resonant circuits in each DC-DC converter module to be opposite, thereby reducing EMI noise of the DC-to-DC converter. The first direction is opposite to the second direction. It is understood that steps S401 and S402 are not sequential.

[0095] The control method for a DC-to-DC DC-DC converter provided in this application embodiment controls the driving positions of corresponding positions of the two resonant circuits included in each DC-DC converter module to be opposite during operation in the first direction, and controls each non-isolated buck / boost circuit to operate in buck mode and make the output current of each non-isolated buck / boost circuit equal. During operation in the second direction, the driving positions of corresponding positions of the two resonant circuits included in each DC-DC converter module are controlled to be opposite, and each non-isolated buck / boost circuit is controlled to operate in DC boost mode and make the output current of each non-isolated buck / boost circuit equal. This achieves current sharing among the non-isolated buck / boost circuits, reduces capacitance ripple between the resonant circuits and non-isolated buck / boost circuits, and improves the reliability of the DC-to-DC DC-DC converter.

[0096] Based on the above embodiments, further, controlling each non-isolated buck / boost circuit to operate in buck mode and ensuring that the output current of each non-isolated buck / boost circuit is equal includes:

[0097] A first current reference value is generated based on a preset voltage reference value and an output voltage sampling value. The duty cycle of each non-isolated buck / boost circuit is adjusted based on the first current reference value and the output current sampling value of each non-isolated buck / boost circuit so that the output current of each non-isolated buck / boost circuit is equal.

[0098] Specifically, during operation in the first direction, the output voltage at the output terminal of the DC-to-DC DCDC converter is sampled to obtain an output voltage sample value. The controller compares a preset voltage reference value with the output voltage sample value to generate a first current reference value. The output current of each non-isolated buck / boost circuit is sampled to obtain an output current sample value for each non-isolated buck / boost circuit. The controller uses the first current reference value as a common current reference for each non-isolated buck / boost circuit. By comparing the first current reference value with the output current sample value of each non-isolated buck / boost circuit, the duty cycle of each non-isolated buck / boost circuit is adjusted to make the output current of each non-isolated buck / boost circuit equal. The preset voltage reference value is set according to actual needs, and this embodiment does not limit it.

[0099] For example, Figure 15 This is a control diagram of the first direction of operation provided in the fifteenth embodiment of this application, as shown below. Figure 15 As shown, a preset voltage reference value is compared with the output voltage sample value, and the output voltage regulator generates a first current reference value based on the comparison result. The output current adjustment of each non-isolated buck / boost circuit adjusts the duty cycle of each non-isolated buck / boost circuit based on the comparison result between the first current reference value and the output current sample value of each non-isolated buck / boost circuit, thereby adjusting the output current of each non-isolated buck / boost circuit to make the output current of all non-isolated buck / boost circuits equal.

[0100] Based on the above embodiments, further, controlling each non-isolated buck / boost circuit to operate in a DC boost state and ensuring that the output current of each non-isolated buck / boost circuit is equal includes:

[0101] Each non-isolated buck / boost circuit is controlled to generate the intermediate bus voltage of each bidirectional isolated DC-DC unit, and a second current reference value is obtained based on the intermediate bus voltage reference value and the sampled intermediate bus voltage value of each bidirectional isolated DC-DC unit.

[0102] The duty cycle of each non-isolated buck / boost circuit is adjusted based on the second current reference value and the input current sampling value of each non-isolated buck / boost circuit so that the input current of each non-isolated buck / boost circuit is equal.

[0103] Specifically, during second-direction operation, the controller controls each non-isolated buck / boost circuit to boost the external input voltage to generate the intermediate bus voltage of each bidirectional isolated DC-DC unit, i.e., the output voltage of each bidirectional isolated DC-DC unit. By sampling the intermediate bus voltage of each bidirectional isolated DC-DC unit, a sampled value of the intermediate bus voltage for each unit can be obtained. The controller can calculate the average value of the sampled intermediate bus voltages of each bidirectional isolated DC-DC unit and use this average value as the intermediate bus voltage comparison value, or obtain the maximum value of the sampled intermediate bus voltages of each unit as the intermediate bus voltage comparison value. The controller compares the intermediate bus voltage reference value with the intermediate bus voltage comparison value to generate a second current reference value, which serves as the common current reference for each non-isolated buck / boost circuit.

[0104] By sampling the input current of each non-isolated buck / boost circuit, the sampled input current value of each non-isolated buck / boost circuit can be obtained. The controller adjusts the duty cycle of each non-isolated buck / boost circuit by comparing the second current reference value with the sampled input current value of each non-isolated buck / boost circuit, so that the output current of each non-isolated buck / boost circuit is equal. The intermediate bus voltage reference value is set according to actual needs, and this embodiment does not limit it.

[0105] For example, Figure 16 This is a control diagram of second-direction operation provided in the sixteenth embodiment of this application, as shown below. Figure 16 As shown, the intermediate bus voltage sampling values ​​of each bidirectional isolated DC-DC unit are acquired, and then averaged to obtain the intermediate bus voltage comparison value. The intermediate bus voltage reference value is then compared with the intermediate bus voltage comparison value, and the intermediate bus voltage regulator generates a second current reference value based on the comparison result. The input current adjustment of each non-isolated buck / boost circuit is based on the comparison result between the second current reference value and the input current sampling value of each non-isolated buck / boost circuit. This adjusts the duty cycle of each non-isolated buck / boost circuit to adjust its output current, ensuring that the output currents of all non-isolated buck / boost circuits are equal.

[0106] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0107] When a circuit or electronic component is referred to as "connected" or "connected" to other circuits or electronic components, it should be understood that the circuit or electronic component is not only directly connected to or connected to other circuits or electronic components, but also that another circuit or electronic component may exist between the circuit or electronic component and other circuits or electronic components.

[0108] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A DC-to-DC converter, characterized in that, Includes at least one DC-DC conversion module and a controller, wherein: Each DC-DC converter module includes two parallel bidirectional isolated DC-DC units, and each bidirectional isolated DC-DC unit includes a resonant circuit and a non-isolated buck / boost circuit, wherein the resonant circuit and the non-isolated buck / boost circuit are cascaded; wherein the operating frequency of each resonant circuit is fixed; if the number of DC-DC converter modules is greater than or equal to 2, the DC-DC converter modules are connected in parallel. The controller is electrically connected to each of the bidirectional isolated DC-DC units. The controller is used to adjust the duty cycle of each non-isolated buck / boost circuit according to a first current reference value and the output current sampling value of each non-isolated buck / boost circuit, thereby controlling the current sharing of each non-isolated buck / boost circuit. The controller is also used to adjust the duty cycle of each non-isolated buck / boost circuit according to a second current reference value and the input current sampling value of each non-isolated buck / boost circuit. The second current reference value is obtained based on the intermediate bus voltage reference value and the intermediate bus voltage sampling value of each bidirectional isolated DC-DC unit. The controller is used to control the driving of corresponding positions of the two resonant circuits included in each DC-DC converter module to be opposite.

2. The DC-to-DC converter according to claim 1, characterized in that, The resonant circuit includes a three-phase LLC circuit or an LLC extension circuit.

3. The DC-to-DC converter according to claim 2, characterized in that, The three-phase LLC circuit includes a first three-phase circuit, a second three-phase circuit, and three transformers, wherein: The first three-phase circuit is connected to the primary side of the three transformers, and the second three-phase circuit is connected to the secondary side of the three transformers.

4. The DC-to-DC converter according to claim 3, characterized in that, The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, and a third capacitor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the first inductor is connected between the first switch and the second switch, the first terminal of the second inductor is connected between the third switch and the fourth switch, and the first terminal of the third inductor is connected between the fifth switch and the sixth switch; the second terminal of the first inductor is connected to the first terminal of the primary winding of the first transformer, the second terminal of the primary winding of the first transformer is connected to the first terminal of the first capacitor, the second terminal of the second inductor is connected to the first terminal of the primary winding of the second transformer, the second terminal of the primary winding of the second transformer is connected to the first terminal of the second capacitor, the second terminal of the third inductor is connected to the first terminal of the primary winding of the third transformer, and the second terminal of the primary winding of the third transformer is connected to the first terminal of the third capacitor; the second terminals of the first capacitor, the second capacitor, and the third capacitor are connected together; or, The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first capacitor, a second capacitor, and a third capacitor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the primary side of the first transformer is connected between the first switch and the second switch, the first terminal of the primary side of the second transformer is connected between the third switch and the fourth switch, and the first terminal of the primary side of the third transformer is connected between the fifth switch and the sixth switch; the second terminal of the primary side of the first transformer is connected to the first terminal of the first capacitor, the second terminal of the primary side of the second transformer is connected to the first terminal of the second capacitor, and the second terminal of the primary side of the third transformer is connected to the first terminal of the third capacitor; the second terminals of the first capacitor, the second capacitor, and the third capacitor are connected together; or, The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first inductor, a second inductor, and a third inductor; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first terminal of the first inductor is connected between the first switch and the second switch, the first terminal of the second inductor is connected between the third switch and the fourth switch, and the first terminal of the third inductor is connected between the fifth switch and the sixth switch; the second terminal of the first inductor is connected to the first terminal of the primary winding of the first transformer, the second terminal of the second inductor is connected to the first terminal of the primary winding of the second transformer, and the second terminal of the third inductor is connected to the first terminal of the primary winding of the third transformer; the second terminals of the primary windings of the first transformer, the second terminals of the primary windings of the second transformer, and the second terminals of the primary windings of the third transformer are connected; or, The first three-phase circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, and a sixth switch; the first switch and the second switch are connected in series, the third switch and the fourth switch are connected in series, and the fifth switch and the sixth switch are connected in series; the first end of the primary side of the first transformer is connected between the first switch and the second switch, the first end of the primary side of the second transformer is connected between the third switch and the fourth switch, and the first end of the third transformer is connected between the fifth switch and the sixth switch; the second ends of the primary sides of the first transformer, the second ends of the primary sides of the second transformer, and the second ends of the primary sides of the third transformer are connected together.

5. The DC-to-DC converter according to claim 3, characterized in that, The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth inductor, a fifth inductor, a sixth inductor, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected to the first terminal of the fourth inductor, and the second terminal of the fourth inductor is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected to the first terminal of the fifth inductor. The second terminal of the fifth inductor is connected between the ninth and tenth switching transistors; the first terminal of the secondary side of the third transformer is connected to the first terminal of the sixth inductor, and the second terminal of the sixth inductor is connected between the eleventh and twelfth switching transistors; the second terminal of the secondary side of the first transformer is connected to the first terminal of the fourth capacitor, the second terminal of the secondary side of the second transformer is connected to the first terminal of the fifth capacitor, the second terminal of the secondary side of the third transformer is connected to the first terminal of the sixth capacitor, and the second terminals of the fourth, fifth, and sixth capacitors are connected together; or, The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected between the ninth and tenth switches; the first terminal of the secondary side of the third transformer is connected between the eleventh and twelfth switches; the second terminal of the secondary side of the first transformer is connected to the first terminal of the fourth capacitor, the second terminal of the secondary side of the second transformer is connected to the first terminal of the fifth capacitor, the second terminal of the secondary side of the third transformer is connected to the first terminal of the sixth capacitor, and the second terminals of the fourth, fifth, and sixth capacitors are connected together; or, The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a fourth inductor, a fifth inductor, and a sixth inductor; the seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series; the first terminal of the secondary side of the first transformer is connected to the first terminal of the fourth inductor, and the second terminal of the fourth inductor is connected between the seventh and eighth switches; the first terminal of the secondary side of the second transformer is connected to the first terminal of the fifth inductor, and the second terminal of the fifth inductor is connected between the ninth and tenth switches; the first terminal of the secondary side of the third transformer is connected to the first terminal of the sixth inductor, and the second terminal of the sixth inductor is connected between the eleventh and twelfth switches; the second terminals of the secondary sides of the first transformer, the second terminals of the secondary sides of the second transformer, and the second terminals of the secondary sides of the third transformer are connected; or, The second three-phase circuit includes a seventh switch, an eighth switch, a ninth switch, a tenth switch, an eleventh switch, and a twelfth switch. The seventh and eighth switches are connected in series, the ninth and tenth switches are connected in series, and the eleventh and twelfth switches are connected in series. The first end of the secondary side of the first transformer is connected between the seventh and eighth switches, the first end of the secondary side of the second transformer is connected between the ninth and tenth switches, and the first end of the secondary side of the third transformer is connected between the eleventh and twelfth switches. The second ends of the secondary sides of the first transformer, the second ends of the secondary sides of the second transformer, and the second ends of the secondary sides of the third transformer are connected together.

6. The DC-to-DC converter according to claim 1, characterized in that, The non-isolated buck / boost circuit adopts an interleaved boost / buck circuit or a single-stage boost / buck circuit.

7. The DC-to-DC converter according to claim 6, characterized in that, The non-isolated buck / boost circuit includes a first branch, a second branch, a seventh inductor, and an eighth inductor, wherein: The first branch and the second branch are connected in parallel. The first branch includes a thirteenth switch and a fourteenth switch connected in series, and the second branch includes a fifteenth switch and a sixteenth switch connected in series. The first end of the seventh inductor is connected to the second end of the fifteenth switch and the first end of the sixteenth switch. The first end of the eighth inductor is connected to the second end of the thirteenth switch and the first end of the fourteenth switch. The second end of the seventh inductor and the second end of the eighth inductor are connected.

8. A bidirectional charging and discharging device, characterized in that, Includes the DC-to-DC converter as described in any one of claims 1 to 7.

9. A control method for a DC-to-DC converter according to any one of claims 1 to 7, characterized in that, include: When running in the first direction, the corresponding positions of the two resonant circuits included in each DC-DC converter module are driven in opposite directions, and each non-isolated buck / boost circuit is controlled to operate in buck mode and make the output current of each non-isolated buck / boost circuit equal. When operating in the second direction, the driving positions of the corresponding positions of the two resonant circuits included in each DC-DC converter module are reversed, and each non-isolated buck / boost circuit is controlled to operate in a DC boost state and make the output current of each non-isolated buck / boost circuit equal; the operation in the first direction is the opposite of the operation in the second direction.

10. The method according to claim 9, characterized in that, The control of each non-isolated buck / boost circuit to operate in buck mode and to make the output current of each non-isolated buck / boost circuit equal includes: The first current reference value is generated based on the preset voltage reference value and the output voltage sampling value. The duty cycle of each non-isolated buck / boost circuit is adjusted based on the first current reference value and the output current sampling value of each non-isolated buck / boost circuit so that the output current of each non-isolated buck / boost circuit is equal.

11. The method according to claim 9, characterized in that, The control of each non-isolated buck / boost circuit to operate in DC boost mode and to make the output current of each non-isolated buck / boost circuit equal includes: Each non-isolated buck / boost circuit is controlled to generate the intermediate bus voltage of each bidirectional isolated DC-DC unit, and a second current reference value is obtained based on the intermediate bus voltage reference value and the sampled intermediate bus voltage value of each bidirectional isolated DC-DC unit. The duty cycle of each non-isolated buck / boost circuit is adjusted based on the second current reference value and the input current sampling value of each non-isolated buck / boost circuit so that the input current of each non-isolated buck / boost circuit is equal.

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