A three-phase single-stage ac / dc converter

Abstract

The application discloses a three-phase single-stage AC / DC converter, and belongs to the technical field of electric energy conversion. The three-phase single-stage AC / DC converter comprises an AC / DC rectifying circuit and a DC / DC resonant circuit. The input of the AC / DC rectifying circuit is connected with three-phase alternating voltage. The AC / DC rectifying circuit outputs direct current to the input of the DC / DC resonant circuit. The DC / DC resonant circuit outputs direct current voltage. The DC / DC resonant circuit comprises a hybrid multi-level switching unit, a resonant conversion unit and a rectifying unit. The hybrid multi-level switching unit, the resonant conversion unit and the rectifying unit are connected in parallel in sequence. The three-phase single-stage AC / DC converter can increase the level number of the input voltage of the resonant cavity, obtain resonant current with smaller conduction loss, and reduce the stress of each high-frequency switch by introducing the multi-level switch.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric energy conversion, and particularly to a three-phase single-stage AC / DC converter. BACKGROUND

[0002] With the explosive growth of distributed energy storage, microgrid and electric vehicle and grid (V2G) applications, isolated AC / DC converters as the key power electronic devices for converting grid AC power to DC power have attracted extensive attention. With the continuous updating and development of power electronic technology, AC / DC converter structures with higher energy transmission efficiency, more compact structure and lower cost are the research focus.

[0003] Current isolated AC / DC converters usually adopt a two-stage structure, the front stage adopts a three-phase PFC converter structure to complete three-phase current control, cope with various grid distortion problems and ensure grid power quality, and the rear stage adopts an isolated DC / DC structure to realize electrical isolation between the power supply side and the power consumption side and realize output voltage stability under different load conditions. However, due to the two-stage power conversion, this structure has the disadvantages of low conversion efficiency and high cost. In addition, the two-stage structure also needs a bulky bus capacitor (usually an inexpensive and short-life electrolytic capacitor) to buffer the energy of the front and rear stage converters, which reduces the reliability of the converter and limits the optimization of its power density.

[0004] Compared with the two-stage structure, the single-stage AC / DC converter can improve the overall efficiency and power density of the converter by reducing the energy conversion level and removing the intermediate DC bus capacitor, which is more in line with the design requirements of current AC / DC power supply equipment. SUMMARY

[0005] The present application aims to provide a three-phase single-stage AC / DC converter with a hybrid multi-level switching unit.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A three-phase single-stage AC / DC converter, comprising an AC / DC rectifier circuit and a DC / DC resonant circuit, the input of the AC / DC rectifier circuit is connected to a three-phase AC voltage, the AC / DC rectifier circuit outputs DC to the input of the DC / DC resonant circuit, the DC / DC resonant circuit outputs a DC voltage, the DC / DC resonant circuit comprises a hybrid multi-level switching unit, a resonant conversion unit and a rectifier unit, the hybrid multi-level switching unit, the resonant conversion unit and the rectifier unit are connected in parallel in sequence.

[0008] In one embodiment, the hybrid multi-level switching unit comprises two first multi-level modules, inputs of the two first multi-level modules are connected in parallel and connected to outputs of the AC / DC rectifier circuit, outputs of the two first multi-level modules are connected to two inputs of the resonant inverter unit respectively, the first multi-level module comprises a plurality of switches and a plurality of capacitors, a drain of a first switch is connected to a first output of the AC / DC rectifier circuit, a source of the first switch is connected to a drain of a second switch, a source of the second switch is connected to a second output of the AC / DC rectifier circuit, a source of the second switch is connected to a drain of a third switch, a source of the third switch is connected to a drain of a fourth switch, a source of the fourth switch is connected to a third output of the AC / DC rectifier circuit, a drain of a fifth switch is connected to a source of the first switch, a source of the third switch is connected to a source of a sixth switch, a source of the fifth switch is connected to a first terminal of a first capacitor, a second terminal of the first capacitor is connected to a drain of the sixth switch, a source of the fifth switch is connected to a drain of a seventh switch, a drain of the sixth switch is connected to a source of an eighth switch, a source of the seventh switch is connected to a drain of the eighth switch, and the drain of the eighth switch is an output of the first multi-level module.

[0009] In one embodiment, the hybrid multi-level switching unit comprises two second multi-level modules, inputs of the two second multi-level modules are connected in parallel and connected to outputs of the AC / DC rectifier circuit, outputs of the two second multi-level modules are connected to two inputs of the resonant inverter unit respectively, the second multi-level module comprises a plurality of switches and a plurality of capacitors, a drain of a ninth switch is connected to a first output of the AC / DC rectifier circuit, a source of the ninth switch is connected to a drain of a tenth switch, a source of the tenth switch is connected to a drain of an eleventh switch, a source of the eleventh switch is connected to a drain of a twelfth switch, a source of the twelfth switch is connected to a third output of the AC / DC rectifier circuit, a source of the ninth switch is connected to a drain of a thirteenth switch, a source of the thirteenth switch is connected to a source of a fourteenth switch, a drain of the fourteenth switch is connected to a second output of the AC / DC rectifier circuit, a first terminal of a second capacitor is connected to a drain of the thirteenth switch, a second terminal of the second capacitor is connected to a drain of a fifteenth switch, a source of the tenth switch is an output of the second multi-level module.

[0010] In a specific embodiment, the hybrid multi-level switching unit comprises two third multi-level modules, inputs of the two third multi-level modules are connected in parallel and connected to outputs of the AC / DC rectifier circuit, outputs of the two third multi-level modules are connected to two inputs of the resonant conversion unit respectively, the third multi-level module comprises a plurality of switches and a plurality of capacitors, a drain of a seventeenth switch is connected to a first output of the AC / DC rectifier circuit, a source of the seventeenth switch is connected to a first terminal of a third capacitor, a second terminal of the third capacitor is connected to a drain of an eighteenth switch, a source of the eighteenth switch is connected to a second output of the AC / DC rectifier circuit, the second output of the AC / DC rectifier circuit is connected to a drain of a nineteenth switch, a source of the nineteenth switch is connected to a first terminal of a fourth capacitor, a second terminal of the fourth capacitor is connected to a drain of a twentieth switch, a source of the twentieth switch is connected to a third output of the AC / DC rectifier circuit, the source of the seventeenth switch is connected to a drain of a twenty-first switch, the drain of the eighteenth switch is connected to a source of a twenty-second switch, the source of the twenty-first switch and the drain of the twenty-second switch are connected to a drain of a twenty-third switch, the source of the nineteenth switch is connected to a drain of a twenty-fourth switch, the drain of the twentieth switch is connected to a source of a twenty-fifth switch, the source of the twenty-fourth switch and the drain of the twenty-fifth switch are connected to a source of a twenty-sixth switch, the source of the twenty-third switch and the drain of the twenty-sixth switch are connected to the output of the third multi-level module.

[0011] In one embodiment, the hybrid multi-level switching unit includes a plurality of switches and a plurality of capacitors, a drain of the twenty-seventh switch is connected to a first output of the AC / DC rectifier circuit, a source of the twenty-seventh switch is connected to a first terminal of a fifth capacitor, a second terminal of the fifth capacitor is connected to a drain of a twenty-eighth switch, a source of the twenty-eighth switch is connected to a second output of the AC / DC rectifier circuit, the second output of the AC / DC rectifier circuit is connected to a drain of a twenty-ninth switch, a source of the twenty-ninth switch is connected to a first terminal of a sixth capacitor, a second terminal of the sixth capacitor is connected to a drain of a thirtieth switch, a source of the thirtieth switch is connected to a third output of the AC / DC rectifier circuit, the source of the twenty-seventh switch is connected to a drain of a thirty-first switch, the drain of the twenty-eighth switch is connected to a source of a thirty-second switch, the source of the thirty-first switch and the drain of the thirty-second switch are connected to a drain of a thirty-fifth switch, the source of the twenty-ninth switch is connected to a drain of a thirty-third switch, the drain of the thirtieth switch is connected to a source of a thirty-fourth switch, the source of the thirty-third switch and the drain of the thirty-fourth switch are connected to a source of a thirty-sixth switch, the source of the thirty-fifth switch is connected to a drain of the thirty-sixth switch, a drain of a thirty-seventh switch is connected to the drain of the thirty-fifth switch, a source of a thirty-eighth switch is connected to the source of the thirty-sixth switch, the source of the thirty-fifth switch and the source of the thirty-seventh switch are outputs of the hybrid multi-level switching unit.

[0012] In one embodiment, the first multi-level module further includes a thirty-ninth switch, a fortieth switch and a seventh capacitor, a source of the thirty-ninth switch is connected to a drain of the seventh switch, a drain of the thirty-ninth switch is connected to a source of the fifth switch, a source of the fortieth switch is connected to a drain of the sixth switch, a drain of the fortieth switch is connected to a source of the eighth switch, a first terminal of the seventh capacitor is connected to the drain of the thirty-ninth switch, a second terminal of the seventh capacitor is connected to the source of the fortieth switch.

[0013] In one embodiment, the second multi-level module further includes a plurality of switches and an eighth capacitor, a drain of a forty-first switch is connected to a source of a ninth switch, a source of a forty-second switch is connected to a source of the forty-first switch, a drain of the forty-second switch is connected to a drain of the thirteenth switch, a drain of a forty-third switch is connected to a source of the eleventh switch, a source of a forty-fourth switch is connected to a source of the forty-third switch, a drain of the forty-fourth switch is connected to a drain of the fifteenth switch, a first terminal of the eighth capacitor is connected to the drain of the forty-first switch, a second terminal of the eighth capacitor is connected to the drain of the forty-third switch.

[0014] In a specific embodiment, the third multi-level module further comprises a plurality of switches and a plurality of capacitors, a drain of the forty-fifth switch is connected to a source of the seventeenth switch, a source of the forty-fifth switch is connected to a first terminal of a ninth capacitor, a second terminal of the ninth capacitor is connected to a drain of a forty-sixth switch, a source of the forty-sixth switch is connected to a drain of a forty-seventh switch, a source of the forty-seventh switch is connected to a first terminal of a tenth capacitor, a second terminal of the tenth capacitor is connected to a drain of a forty-eighth switch, a source of the forty-eighth switch is connected to a drain of the twentieth switch, the drain of the forty-seventh switch is connected to a drain of the eighteenth switch and a source of the nineteenth switch, the source of the forty-fifth switch is connected to a drain of the twenty-first switch, the drain of the forty-sixth switch is connected to a source of the twenty-second switch, the source of the forty-seventh switch is connected to a drain of the twenty-fourth switch, and the drain of the forty-eighth switch is connected to a source of the twenty-fifth switch.

[0015] In a specific embodiment, the first multi-level module further comprises a plurality of forty-ninth switches, a plurality of fiftieth switches and a plurality of eleventh capacitors, the plurality of forty-ninth switches are connected in series between the seventh switch and the thirty-ninth switch in the same direction, the plurality of fiftieth switches are connected in series between the eighth switch and the fortieth switch in the same direction, and the eleventh capacitors are connected in series between a drain of each of the forty-ninth switches and a source of each of the fiftieth switches.

[0016] The beneficial effects are that the three-phase single-stage AC / DC converter can increase the number of levels of the input voltage of the resonant cavity, obtain a resonant current with smaller conduction loss, and the introduction of the multi-level switch can reduce the stress of each high-frequency switch.

[0017] In order to make the above features and advantages of the application more obvious and easy to understand, the following specific embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a structural block diagram of the three-phase single-stage AC / DC converter of the application.

[0019] Figure 2 The figure is a structural block diagram of the three-phase single-stage AC / DC converter of the application. Figure 1 The figure is a schematic diagram of a specific embodiment of the three-phase single-stage AC / DC converter.

[0020] Figure 3 The figure is a schematic diagram of a specific embodiment of the three-phase single-stage AC / DC converter. Figure 2 The figure is a voltage and current waveform diagram of the AC / DC rectifier circuit.

[0021] Figure 4(a) is an input voltage waveform diagram of the LLC resonant cavity when the voltage u PY is greater than the voltage u NY . LLC The figure is a voltage and current waveform diagram of the AC / DC rectifier circuit.

[0022] Figure 4(b) is a plot of the voltage u PY less than the voltage u NY input voltage u of the LLC resonant tank LLC waveform.

[0023] Figure 5(a) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the 0-t1 phase.

[0024] Figure 5(b) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t1-t2 phase.

[0025] Figure 5(c) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t2-t3 phase.

[0026] Figure 5(d) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t3-T s / 2 phase.

[0027] Figure 5(e) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the T s / 2-t4 phase.

[0028] Figure 5(f) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t4-t5 phase.

[0029] Figure 5(g) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t5-t6 phase.

[0030] Figure 5(h) is a schematic diagram of the switching logic of the hybrid multi-level switching cell 221 during the t6-T s phase.

[0031] Figure 6(a) is a second embodiment of the hybrid multi-level switching cell 221 employing a hybrid five-level switching network.

[0032] Figure 6(b) is a third embodiment of the hybrid multi-level switching cell 221 employing a hybrid five-level switching network.

[0033] Figure 6(c) is a fourth embodiment of the hybrid multi-level switching cell 221 employing a hybrid five-level switching network.

[0034] Figure 7(a) is a first embodiment of a hybrid seven-level switching network.

[0035] Figure 7(b) is a second embodiment of a hybrid seven-level switching network.

[0036] Figure 7(c) is a third embodiment of a hybrid seven-level switching network.

[0037] Figure 8for the extended multi-level switching network. DETAILED DESCRIPTION

[0038] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present application.

[0039] Figure 1 is a structure block diagram of a three-phase single-stage AC / DC converter of the present application. More specifically, three-phase alternating voltages u A , u B , u C are filtered and input to an AC / DC rectifier circuit 11 through inductors L A , L B , L C respectively, the AC / DC rectifier circuit 11 outputs direct current to a PYN three-terminal, a DC / DC resonant circuit 12 converts the electric energy of the PYN three-terminal and outputs a voltage V o to a load R o . The DC / DC resonant circuit 12 adjusts the output voltage V o and three-phase alternating currents i A , i B , i C , or adjusts an output current I o and three-phase alternating currents i A , i B , i C .

[0040] Further, the DC / DC resonant circuit 12 comprises a hybrid multi-level switching unit 121, a resonant conversion unit 122 and a rectifier unit 123, which are connected in parallel in sequence.

[0041] Figure 2 is a schematic diagram of a specific embodiment of the three-phase single-stage AC / DC converter in Figure 1 . As shown in Figure 2 , the AC / DC rectifier circuit 21 is a Swiss rectifier circuit, which comprises bidirectional switches S ay , S by , S cy , S ay , S by , S cyThe low-frequency switch is turned on at the moment when two-phase voltages intersect. The bidirectional switch of the phase with larger absolute value of voltage amplitude in the intersecting two-phase is turned off, and the bidirectional switch of the phase with smaller amplitude is turned on. In this way, the phase with larger amplitude in the forward voltage passes through the upper diode D u connected to the P terminal, the phase with larger amplitude in the negative voltage passes through the lower diode D d connected to the N terminal, and the remaining phase passes through the turned-on bidirectional switch S y connected to the Y terminal, and the combination Figure 3 of the three phases is the three-phase alternating voltage A , u B , u C . P , u N , u Y , three forward line voltages PN , u PY and u YN are obtained, in which u PN is always the largest one, and the other two voltages u PY and u YN alternately change.

[0042] Further, the three-phase single-stage AC / DC converter further comprises a capacitor circuit 23 connected in parallel between the AC / DC rectifier circuit 21 and the DC / DC resonant circuit 22. The capacitor circuit 23 comprises capacitors C PY , C YN and C PN , the capacitor C PY is connected in parallel between the P terminal and the Y terminal, the capacitor C YN is connected in parallel between the Y terminal and the N terminal, and the capacitor C PN is connected in parallel between the P terminal and the N terminal.

[0043] The DC / DC resonant circuit 22 comprises a hybrid multi-level switching unit 221, a resonant conversion unit 222 and a rectifier unit 223, which are connected in parallel in sequence.

[0044] It should be noted that the hybrid multi-level switching unit 221 cannot adopt ordinary multi-level topologies such as flying capacitor type multi-level topology and midpoint clamped type multi-level topology, because the Swiss rectifier circuit functions as low-frequency rectification and does not perform power conversion, and the capacitors C PY , C YN , C PNOnly responsible for filtering high-frequency components in the input current, only small capacitance thin film capacitors can be used, and large capacitance electrolytic capacitors cannot be selected. Because electrolytic capacitors cannot be used, common multi-level topologies such as flying capacitor type multi-level topology and midpoint clamping type multi-level topology cannot create multi-level, therefore, the capacitors can only be moved to the DC / DC resonant circuit 22 to build a hybrid multi-level switching topology.

[0045] In the specific embodiment, the hybrid multi-level switching unit 221 adopts a hybrid five-level switching network. The hybrid multi-level switching unit 221 includes a multi-level module 2211 and a multi-level module 2212, the inputs of the multi-level module 2211 and the multi-level module 2212 are connected in parallel to the output of the AC / DC rectifier circuit 21, the output of the multi-level module 2211 is an output terminal a, and the output of the multi-level module 2212 is an output terminal b. Further, the drain of the switch S1 is connected to the P terminal, the source of the switch S1 is connected to the drain of the switch S2, the source of the switch S2 is connected to the Y terminal, the source of the switch S2 is connected to the drain of the switch S3, the source of the switch S3 is connected to the drain of the switch S4, the source of the switch S4 is connected to the N terminal, the drain of the switch S m1 the source of the switch S3 is connected to the source of the switch S m3 the source of the switch S m1 the first end of the capacitor C f1 the second end of the capacitor C f1 the drain of the switch S m3 the source of the switch S m1 the drain of the switch S m2 the source of the switch S m3 the drain of the switch S m4 the source of the switch S m2 the source of the switch S m4 the drain of the switch S m5 the source of the switch S7 is connected to the source of the switch S m7 the source of the switch S m5 the first end of the capacitor C f2 the second end of the capacitor C f2 the drain of the switch S m7 the source of the switch S m6 the drain of the switch S m5 the source of the switch S m7 the drain of the switch S m8 the source of the switch S m6 the source of the switch Sm8 The drain is the output terminal b.

[0046] The output terminal b is connected to the first terminal of the primary winding of the transformer T1. The primary winding of the transformer T passes through the inductor L r , capacitor C r Connect output terminal a, inductor L m The secondary winding of the transformer T1 is connected in parallel to the rectifier unit 223. In this embodiment, the rectifier unit 223 includes a rectifier bridge composed of a diode D1, a diode D2, a diode D3 and a diode D4.

[0047] in, Figure 2 The resonant conversion unit 222 in the embodiment is of LLC topology. It should be noted that the resonant conversion unit 222 may also be of LC topology or DAB topology.

[0048] The input voltage of the DC / DC resonant circuit 22 is three line voltages u PN 、u PY and u YN , high frequency switching of the switches in the hybrid multilevel switch unit 221, the voltage u PN 、u PY 、u YN Or 0 level is fed into the LLC resonant cavity, and the LLC resonant cavity is used to provide soft switching for high frequency switching, and the voltage u PY Greater than voltage u NY The input voltage u of the LLC resonant cavity is LLC As shown in Figure 4(a), the voltage u PY Less than voltage u NY The input voltage u of the LLC resonant cavity is LLC As shown in Figure 4(b). The switching logic diagram of different stages in Figure 4(a) is shown in Figure 5, where the input voltage u of the LLC resonant cavity is LLC is the voltage between output terminals a and b.

[0049] FIG5(a) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the 0-t1 period. As shown in FIG5(a), switches S8 and S m7 , switch S m8 , switch S m2 , switch S m1 , switch S1 is turned on to form a loop, and the current flows from the P terminal to the N terminal. At this time, the input voltage u LLC is the voltage u PN .

[0050] FIG5(b) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the t1-t2 period. As shown in FIG5(b), switches S1 and S2 are connected.m1 , switch S m2 , switch S m8 , switch S m7 , switch S8 is turned on to form a loop, and the current flows from the N terminal to the P terminal. At this time, the input voltage u LLC of the LLC resonant cavity is the voltage u PN .

[0051] Fig. 5(c) is a schematic diagram of the switch logic of the hybrid multi-level switching unit 221 in the t2-t3 stage. As shown in Fig. 5(c), the switch S1, the switch S m1 , the switch S m2 , the switch S m6 , the switch S m7 , and the switch S8 are turned on to form a loop, and the current flows from the P terminal to the N terminal. At this time, the input voltage u LLC of the LLC resonant cavity is the voltage u PN -u cf , wherein the voltage u cf is the voltage across the capacitor C f2 , and t3 is the D PN T s .

[0052] Fig. 5(d) is a schematic diagram of the switch logic of the hybrid multi-level switching unit 221 in the t3-T s / 2 stage. As shown in Fig. 5(d), the switch S1, the switch S m1 , the switch S m2 , the switch S m6 , the switch S m7 , and the switch S7 are turned on to form a loop, and the current flows from the Y terminal to the P terminal. At this time, the input voltage u LLC of the LLC resonant cavity is the voltage u PY -u cf , wherein the voltage u cf is the voltage across the capacitor C f2 .

[0053] Fig. 5(e) is a schematic diagram of the switch logic of the hybrid multi-level switching unit 221 in the T s / 2-t4 stage. As shown in Fig. 5(e), the switch S4, the switch S m3 , the switch S m4 , the switch S m6 , the switch S m5 , and the switch S5 are turned on to form a loop, and the current flows from the P terminal to the N terminal. At this time, the input voltage u LLC of the LLC resonant cavity is the voltage u PN .

[0054] Fig. 5(f) is a switch logic diagram of the hybrid multi-level switching cell 221 in the t4-t5 stage, as shown in Fig. 5(f), the switch S4, the switch S m3 , the switch S m4 , the switch S m6 , the switch S m5 , and the switch S5 are turned on to form a loop, and the current flows from the N terminal to the P terminal, at this time, the input voltage u LLC of the LLC resonant cavity is the voltage -u PN .

[0055] Fig. 5(g) is a switch logic diagram of the hybrid multi-level switching cell 221 in the t5-t6 stage, as shown in Fig. 5(g), the switch S5, the switch S m5 , the switch S m8 , the switch S m4 , the switch S m3 , and the switch S4 are turned on to form a loop, and the current flows from the N terminal to the P terminal, at this time, the input voltage u LLC of the LLC resonant cavity is the voltage -u PN +u cf , wherein the voltage u cf is the voltage across the capacitor C f2 , and t6 is T s / 2+D PN T s .

[0056] Fig. 5(h) is a switch logic diagram of the hybrid multi-level switching cell 221 in the t6-T s stage, as shown in Fig. 5(h), the switch S5, the switch S m5 , the switch S m8 , the switch S m4 , the switch S m3 , and the switch S3 are turned on to form a loop, and the current flows from the Y terminal to the P terminal, at this time, the input voltage u LLC of the LLC resonant cavity is the voltage -u PY +u cf , wherein the voltage u cf is the voltage across the capacitor C f2 .

[0057] Figures 6(a) to 6(c) is another specific embodiment of the hybrid multi-level switching cell 221 using a hybrid five-level switching network.

[0058] In the hybrid multi-level switching unit 621a of Fig. 6(a), the input of the multi-level module 6211a and the input of the multi-level module 6212a are connected in parallel to the output of the AC / DC rectifying circuit 21, the output of the multi-level module 6211a is the output terminal a, the output of the multi-level module 6212a is the output terminal b, the drain of the switch S9 is connected to the P terminal, the source of the switch S9 is connected to the drain of the switch S 10 , the source of the switch S 10 is connected to the drain of the switch S 11 , the source of the switch S 11 is connected to the drain of the switch S 12 , the source of the switch S 12 is connected to the N terminal, the source of the switch S9 is connected to the drain of the switch S m10 , the source of the switch S m10 is connected to the drain of the switch S m9 , the source of the switch S m9 is connected to the Y terminal, the source of the switch S 11 is connected to the drain of the switch S m12 , the source of the switch S m12 is connected to the drain of the switch S m11 , the source of the switch S m11 is connected to the Y terminal, one end of the capacitor C f3 is connected to the drain of the switch S m10 , the other end of the capacitor C f3 is connected to the drain of the switch S m12 . The drain of the switch S 13 is connected to the P terminal, the source of the switch S 13 is connected to the drain of the switch S 14 , the source of the switch S 14 is connected to S 15 , the source of the switch S 15 is connected to the drain of the switch S 16 , the source of the switch S 16 is connected to the N terminal, the source of the switch S 13 is connected to the drain of the switch S m14 , the source of the switch S m14 is connected to the drain of the switch S m13 , the source of the switch S m13 is connected to the Y terminal, the source of the switch S 15 is connected to the drain of the switch S m16 , the source of the switch S m16 is connected to the drain of the switch S m15 , the source of the switch S m15 is connected to the Y terminal, one end of the capacitor C f4 is connected to the drain of the switch S m14 , the other end of the capacitor C f4 is connected to the drain of the switch S m16of switch S 10 of switch S 14 of switch S

[0059] In the hybrid multi-level switching unit 621b of Fig. 6(b), the input of the multi-level module 6211b and the input of the multi-level module 6212b are connected in parallel to the output of the AC / DC rectifier circuit 21, the output of the multi-level module 6211b is the output terminal a, the output of the multi-level module 6212b is the output terminal b, the drain of switch S 17 of switch S 17 of switch S f5 of switch S f5 of switch S 18 of switch S 18 of switch S 19 of switch S 19 of switch S f6 of switch S f6 of switch S 20 of switch S 20 of switch S 17 of switch S m17 of switch S 18 of switch S m18 of switch S m17 of switch S m18 of switch S m21 of switch S 19 of switch S m19 of switch S 20 of switch S m20 of switch S m19 of switch S m20 of switch S m22 of switch S m21 of switch S m22 of switch S 21 of switch S 21 of switch S f7 of switch S f7 of switch S 22 of switch S 22 of switch S 23 of switch S f8 of switch S f8 of switch S24 The drain of the switch S 24 The source of the switch is connected to the N terminal, and the switch S 21 The source of the connected switch S m23 The drain of the switch S 22 The drain of the switch S m24 The source of the switch S m23 The source and switch S m24 The drain of the switch S m27 The drain of switch S 23 The source of the connected switch S m25 The drain of the switch S 24 The drain of the switch S m26 The source of the switch S m25 The source and switch S m26 The drain of the switch S m28 The source of the switch S m27 The source and switch S m28 The drains are connected together to form the output terminal b.

[0060] In the hybrid multi-level switch unit 621c of FIG6(c), the switch S 25 The drain of the switch is connected to the P terminal, and the switch S 25 The source connection capacitance C f9 The first end of the capacitor C f9 The second end of the switch S 26 The drain of the switch S 26 The source is connected to the Y terminal, and the Y terminal is connected to the switch S 27 The drain of the switch S 27 The source connection capacitance C f10 The first end of the capacitor C f10 The second end of the switch S 28 The drain of the switch S 28 The source of the switch is connected to the N terminal, and the switch S 25 The source of the connected switch S m29 The drain of the switch S 26 The drain of the switch S m30 The source of the switch S m29 The source and switch S m30 The drain of the switch S m33 The drain of the switch S 27 The source of the connected switch S m31 The drain of the switch S 28 The drain of the switch S m32 The source of the switch S m31 The source and switch S m32 The drain of the switch S m34 The source of the switch S m33 The source of the connected switch Sm34 The drain of the switch S m35 The drain of the switch S m33 The drain of the switch S m36 The source of the connected switch S m34 The source of the switch S m33 The source is the output terminal a, and the switch S m35 The source is output terminal b.

[0061] Flying electrolytic capacitor C in hybrid multilevel switch unit f It has the following functions. First, it helps some or all high-frequency switches to withstand certain voltage stress. Normal voltage-resistant switches can be used to cope with high input voltage situations. As shown in Figure 6(b), part of the voltage between ports PY will bear the voltage at C f5 The remaining will be allocated to switch S 17 and switch S 18 At high input voltage, the switch S 17 and switch S 18 The voltage stress on the switch is low, which can reduce the cost of the switch tube. Secondly, by controlling the duration of each duty cycle, it helps to fly across the electrolytic capacitor C f Charging, thus obtaining different capacitor voltages u cf .

[0062] The hybrid multi-level switch unit controls the resonant current by switching frequency modulation and distributes the three-phase current by duty cycle. Compared with the three-level switch network, the five-level switch network has an input voltage u of the LLC resonant cavity in the positive and negative half cycles. LLC The number of levels changes, adding two symmetrical levels; and the amplitude changes to the level voltage minus the flying capacitance C f The voltage at both ends can change the form and size of the resonant current by changing the working time of this level, thereby changing the transmission energy of the LLC resonant cavity.

[0063] Furthermore, the five-level switch network can be further expanded. Continuing to add multi-level switch networks can bring the following benefits: increasing the number of levels can expand the gain range of the converter; increasing the number of series devices will reduce the voltage stress of each switch device; changing the turn-off current value and the resonant current peak value can reduce the turn-off loss and conduction loss of each switch tube.

[0064] Figures 7(a) to 7(c) Schematic diagram of the circuit for expanding the hybrid five-level switching network into a hybrid seven-level switching network.

[0065] In FIG7 (a), the hybrid multilevel switch unit 721a, the inputs of the multilevel module 7211a and the multilevel module 7212a are all connected in parallel with the output of the AC / DC rectifier circuit 21, the output of the multilevel module 7211a is the output terminal a, and the output of the multilevel module 7212a is the output terminal b. Figure 2 The hybrid multi-level switch unit 221 is based on the addition of switch S m37 , switch S m38 , capacitor C f11 , switch S m39 , switch S m40 With capacitor C f12 , the drain of switch S1 is connected to the P terminal, the source of switch S1 is connected to the drain of switch S2, the source of switch S2 is connected to the Y terminal, the source of switch S2 is connected to the drain of switch S3, the source of switch S3 is connected to the drain of switch S4, the source of switch S4 is connected to the N terminal, and switch S m1 The drain of switch S1 is connected to the source of switch S3, and the source of switch S m3 The source of the switch S m1 The source connection capacitance C f11 The first end of the capacitor C f11 The second end of the switch S m3 The drain of the switch S m1 The source of the connected switch S m37 The drain of the switch S m3 The drain of the switch S m38 The source of the switch S m37 The source connection capacitance C f1 The first end of the capacitor C f1 The second end of the switch S m38 The drain of the switch S m37 The source of the connected switch S m2 The drain of the switch S m38 The drain of the switch S m4 The source of the switch S m2 The source of the connected switch S m4 The drain of switch S5 is connected to the P terminal, the source of switch S5 is connected to the drain of switch S6, the source of switch S6 is connected to the Y terminal, the source of switch S6 is connected to the drain of switch S7, the source of switch S7 is connected to the drain of switch S8, the source of switch S8 is connected to the N terminal, and switch S m5 The drain of switch S5 is connected to the source of switch S7, and the source of switch S m7 The source of the switch S m5 The source connection capacitance C f12 The first end of the capacitor C f12 The second end of the switch S m7 The drain of the switch Sm39 The drain of the switch S m5 The source of the switch S m7 The drain of the switch S m40 The source of the switch S m39 The source connection capacitance C f2 The first end of the capacitor C f2 The second end of the switch S m40 The drain of the switch S m39 The source of the connected switch S m6 The drain of the switch S m40 The drain of the switch S m8 The source of the switch S m6 The source of the connected switch S m8 The drain is the output terminal b.

[0066] In the hybrid multilevel switch unit 721b in FIG7(b), the inputs of the multilevel module 7211b and the multilevel module 7212b are connected in parallel with the output of the AC / DC rectifier circuit 21. The output of the multilevel module 7211b is the output terminal a, and the output of the multilevel module 7212b is the output terminal b. A switch S is added to the hybrid multilevel switch unit 621a in FIG6(a). m41 , switch S m42 , switch S m43 , switch S m44 , capacitor C f13 , switch S m45 , switch S m46 , switch S m47 , switch S m48 , capacitor C f14 , the drain of switch S9 is connected to the P terminal, and the source of switch S9 is connected to the switch S 10 The drain of the switch S 10 The source connection S 11 The drain of the switch S 11 The source of the connected switch S 12 The drain of the switch S 12 The source of switch S9 is connected to the N terminal, and the source of switch S m42 The drain of the switch S m42 The source of the connected switch S m41 The source of the switch S m41 The drain of the switch S m10 The drain of the switch S m10 The source of the connected switch S m9 The source of the switch S m9 The drain of the switch is connected to the Y terminal, and the switch S 11 The source of the connected switch S m44 The drain of the switch S m44source of the source-connected switch S m43 source of the source-connected switch S m43 drain of the drain-connected switch S m12 drain of the drain-connected switch S m12 source of the source-connected switch S m11 source of the source-connected switch S m11 drain-connected Y terminal of the capacitor C f3 one end of the capacitor C m10 drain of the capacitor C f3 other end of the capacitor C m12 drain of the drain-connected switch S m42 drain-connected capacitor C f13 first end of the capacitor C f13 second end of the capacitor C m44 drain of the drain-connected switch S 13 drain-connected P terminal of the switch S 13 source of the source-connected switch S 14 drain of the drain-connected switch S 14 source-connected S 15 drain of the drain-connected switch S 15 source of the source-connected switch S 16 drain of the drain-connected switch S 16 source-connected N terminal of the switch S 13 source of the source-connected switch S m46 drain of the drain-connected switch S m46 source of the source-connected switch S m45 source of the source-connected switch S m45 drain-connected switch S m14 drain of the drain-connected switch S m14 source of the source-connected switch S m13 source of the source-connected switch S m13 drain-connected Y terminal of the switch S 15 source of the source-connected switch S m48 drain of the drain-connected switch S m48 source of the source-connected switch S m47 source of the source-connected switch S m47 drain-connected switch S m16 drain of the drain-connected switch S m16 source of the source-connected switch S m15 source of the source-connected switch S m15 drain-connected Y terminal of the capacitor C f4 one end of the capacitor C m14 drain of the capacitor C f4 other end of the capacitor C m16 drain of the capacitor C f14 one end of the capacitor C m46 drain of the capacitor C f14 other end of the capacitor Cm48 The drain of the switch S 10 The source is the output terminal a, and the switch S 14 The source is the output terminal b.

[0067] In the hybrid multilevel switch unit 721c in FIG7(c), the inputs of the multilevel module 7211c and the multilevel module 7212c are both connected in parallel with the output of the AC / DC rectifier circuit 21. The output of the multilevel module 7211c is the output terminal a, and the output of the multilevel module 7212c is the output terminal b. A switch S is added to the hybrid multilevel switch unit 621b in FIG6(b). 29 , switch S 30 , switch S 31 , switch S 32 , capacitor C f15 , capacitor C f16 , switch S 33 , switch S 34 , switch S 35 , switch S 36 , capacitor C f17 , capacitor C f18 , switch S 17 The drain of the switch is connected to the P terminal, and the switch S 17 The source connection capacitance C f5 The first end of the capacitor C f5 The second end of the switch S 18 The drain of the switch S 18 The source is connected to the Y terminal, and the Y terminal is connected to the switch S 19 The drain of the switch S 19 The source connection capacitance C f6 The first end of the capacitor C f6 The second end of the switch S 20 The drain of the switch S 20 The source of the switch is connected to the N terminal, and the switch S 17 The source of the connected switch S 29 The drain of the switch S 29 The source connection capacitance C f15 The first end of the capacitor C f15 The second end of the switch S 30 The drain of the switch S 30 The source of the connected switch S 31 The drain of the switch S 31 The source connection capacitance C f16 The first end of the capacitor C f16 The second end of the switch S 32 The drain of the switch S 32 The source of the connected switch S 20 The drain of the switch S 31the drain of the switch S 18 the drain of the switch S 19 the source of the switch S 29 the source of the switch S m17 the drain of the switch S 30 the drain of the switch S m18 the source of the switch S m17 the source of the switch S m18 the drain of the switch S m21 the drain of the switch S 31 the source of the switch S m19 the drain of the switch S 32 the drain of the switch S m20 the source of the switch S m19 the source of the switch S m20 the drain of the switch S m22 the source of the switch S m21 the source of the switch S m22 the drain of the switch S 21 the drain of the switch S 21 the source of the switch S f7 the first terminal of the capacitor C f7 the second terminal of the capacitor C 22 the drain of the switch S 22 the source of the switch S 23 the drain of the switch S 23 the first terminal of the capacitor C f8 the second terminal of the capacitor C f8 the drain of the switch S 24 the source of the switch S 24 the source of the switch S 21 the source of the switch S 33 the drain of the switch S 33 the first terminal of the capacitor C f17 the second terminal of the capacitor C f17 the drain of the switch S 34 the source of the switch S 34 the source of the switch S 22 the source of the switch S 23 the source of the switch S 34 the source of the switch S 35 the drain of the switch S 35 the first terminal of the capacitor C f18 the second terminal of the capacitor C f18 the drain of the switch S 36 the source of the switch S 36 the source of the switch S 24 the drain of the switch S33 The source of the connected switch S m23 The drain of the switch S 34 The drain of the switch S m24 The source of the switch S m23 The source and switch S m24 The drain of the switch S m27 The drain of switch S 35 The source of the connected switch S m25 The drain of the switch S 36 The drain of the switch S m26 The source of the switch S m25 The source and switch S m26 The drain of the switch S m28 The source of the switch S m27 The source and switch S m28 The drains are connected together to form the output terminal b.

[0068] Furthermore, the hybrid seven-level switch network can be expanded into a multi-level switch network. Taking the topology in FIG7(a) as an example, the expanded multi-level switch network is as follows: Figure 8 As shown, the switch S m37 With switch S m2 Multiple switches S are connected in series in the same direction mx , in switch S m38 With switch S m4 Multiple switches S are connected in series in the same direction my , at each switch S mx The drain of each switch S my The capacitor C is connected in series between the source fz . In switch S m39 With switch S m6 Multiple switches S are connected in series in the same direction mp , in switch S m40 With switch S m8 Multiple switches S are connected in series in the same direction mq , at each switch S mp The drain of each switch S mq The capacitor C is connected in series between the source fn .

[0069] Although the present invention has been disclosed above with reference to the embodiments, they are not intended to limit the present invention. Anyone with ordinary skill in the art may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the appended patent applications.

Claims

1. A three-phase single-stage AC / DC converter, characterized in that: The AC / DC rectifier circuit includes an AC / DC rectifier circuit and a DC / DC resonant circuit, wherein the input of the AC / DC rectifier circuit is connected to a three-phase AC voltage, the AC / DC rectifier circuit outputs DC power to the input of the DC / DC resonant circuit, and the DC / DC resonant circuit outputs a DC voltage. The DC / DC resonant circuit includes a hybrid multi-level switch unit, a resonant conversion unit, and a rectifier unit, wherein the hybrid multi-level switch unit, the resonant conversion unit, and the rectifier unit are sequentially connected in parallel. The hybrid multi-level switch unit includes two first multi-level modules. The inputs of the two first multi-level modules are connected in parallel and connected to the output of the AC / DC rectifier circuit. The outputs of the two first multi-level modules are respectively connected to the two input terminals of the resonant conversion unit. The first multi-level module includes multiple switches and multiple capacitors. The drain of the first switch is connected to the first output terminal of the AC / DC rectifier circuit, the source of the first switch is connected to the drain of the second switch, the source of the second switch is connected to the second output terminal of the AC / DC rectifier circuit, the source of the second switch is connected to the drain of the third switch, the source of the third switch is connected to the drain of the fourth switch, and the source of the fourth switch is connected to the third output terminal of the AC / DC rectifier circuit. The drain of the fifth switch is connected to the source of the first switch, the source of the third switch is connected to the source of the sixth switch, the source of the fifth switch is connected to the first terminal of the first capacitor, the second terminal of the first capacitor is connected to the drain of the sixth switch, the source of the fifth switch is connected to the drain of the seventh switch, the drain of the sixth switch is connected to the source of the eighth switch, and the source of the seventh switch is connected to the drain of the eighth switch to become the output of the first multi-level module. In the first phase of the positive half cycle, the fourth switch, the sixth switch, and the eighth switch of the first multi-level module connected to the second input terminal of the resonant conversion unit, and the seventh switch, the fifth switch, and the first switch of the first multi-level module connected to the first input terminal of the resonant conversion unit are turned on to form a loop; In the second phase of the positive half cycle, the first switch, the fifth switch, and the seventh switch of the first multi-level module connected to the first input terminal of the resonant conversion unit, and the eighth switch, the sixth switch, and the fourth switch of the first multi-level module connected to the second input terminal of the resonant conversion unit are turned on to form a loop; In the third phase of the positive half cycle, the first switch, the fifth switch, and the seventh switch of the first multi-level module connected to the first input terminal of the resonant conversion unit, and the seventh switch, the sixth switch, and the fourth switch of the first multi-level module connected to the second input terminal of the resonant conversion unit are turned on to form a loop; In the fourth phase of the positive half cycle, the first switch, the fifth switch, and the seventh switch of the first multi-level module connected to the first input terminal of the resonant conversion unit, and the seventh switch, the sixth switch, and the third switch of the first multi-level module connected to the second input terminal of the resonant conversion unit are turned on to form a loop; The on-state of the switch in the negative half cycle is symmetrical with that in the positive half cycle.

2. A three-phase single-stage AC / DC converter as claimed in claim 1, characterized in that: The first multi-level module further includes a thirty-ninth switch, a fortieth switch, and a seventh capacitor. The source of the thirty-ninth switch is connected to the drain of the seventh switch, the drain of the thirty-ninth switch is connected to the source of the fifth switch, the source of the fortieth switch is connected to the drain of the sixth switch, the drain of the fortieth switch is connected to the source of the eighth switch, a first end of the seventh capacitor is connected to the drain of the thirty-ninth switch, and a second end of the seventh capacitor is connected to the source of the fortieth switch.

3. A three-phase single-stage AC / DC converter as claimed in claim 2, characterized in that: The first multi-level module further includes a plurality of 49th switches, a plurality of 50th switches, and a plurality of 11th capacitors. The plurality of 49th switches are connected in series in the same direction between the seventh switch and the 39th switch, the plurality of 50th switches are connected in the same direction in series between the eighth switch and the 40th switch, and the 11th capacitor is connected in series between the drain of each 49th switch and the source of each 50th switch.

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