Three-phase single-stage AC / DC converter

Abstract

The invention 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 rectification circuit and a DC / DC resonance circuit, the input of the AC / DC rectification circuit is connected with a three-phase AC voltage, the AC / DC rectification circuit outputs a DC to the input of the DC / DC resonance circuit, the DC / DC resonance circuit outputs a DC voltage, and the DC voltage is connected with the AC / DC rectification circuit. The DC / DC resonant circuit comprises a hybrid multi-level switch unit, a resonant conversion unit and a rectification unit, and the hybrid multi-level switch unit, the resonant conversion unit and the rectification unit are sequentially connected in parallel. According to the three-phase single-stage AC / DC converter, the level number of the input voltage of the resonant cavity can be increased, resonant current with smaller conduction loss can be obtained, and meanwhile, the stress of each high-frequency switch can be reduced through introduction of the multi-level switch.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to a three-phase single-stage AC / DC converter. Background Art

[0002] With the explosive growth of distributed energy storage, microgrids and vehicle-to-grid (V2G) applications, isolated AC / DC converters, as key power electronic devices that convert grid AC power into DC power, have received extensive attention. With the continuous updating and development of power electronics technology, AC / DC converter structures with higher energy transmission efficiency, more compact structure and lower cost have become a hot topic of research.

[0003] The current isolated AC / DC converter usually adopts a two-stage structure. The front stage adopts a three-phase PFC converter structure to complete the three-phase current control, deal with various grid distortion problems, and ensure the quality of grid power. The back stage adopts an isolated DC / DC structure to achieve electrical isolation between the power supply side and the power consumption side, and achieve 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 requires a bulky bus capacitor (usually a cheap and short-life electrolytic capacitor) to buffer the energy of the front and rear converters, which will reduce the reliability of the converter and limit 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 of the invention

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

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A three-phase single-stage AC / DC converter comprises 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, the DC / DC resonant circuit outputs a DC voltage, and the DC / DC resonant circuit comprises 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.

[0008] In a specific embodiment, 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 ends of the resonant conversion unit, the first multi-level module includes a plurality of switches and a plurality of capacitors, the drain of the first switch is connected to the first output end 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 end of the AC / DC rectifier circuit, and the source of the second switch is connected to the The drain of the third switch is connected to the drain of the fourth switch, 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 end of the first capacitor, the second end 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 be the output of the first multi-level module.

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

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

[0011] In a specific embodiment, the hybrid multi-level switch unit includes a plurality of switches and a plurality of capacitors, the drain of the twenty-seventh switch is connected to the first output end of the AC / DC rectifier circuit, the source of the twenty-seventh switch is connected to the first end of the fifth capacitor, the second end of the fifth capacitor is connected to the drain of the twenty-eighth switch, the source of the twenty-eighth switch is connected to the second output end of the AC / DC rectifier circuit, the second output end of the AC / DC rectifier circuit is connected to the drain of the twenty-ninth switch, the source of the twenty-ninth switch is connected to the first end of the sixth capacitor, the second end of the sixth capacitor is connected to the drain of the thirtieth switch, the source of the thirtieth switch is connected to the third output end of the AC / DC rectifier circuit, and the source of the twenty-seventh switch is connected to the thirtieth switch. The drain of the twenty-eighth switch is connected to the source of the thirty-second switch, the source of the thirty-first switch and the drain of the thirty-second switch are connected to the drain of the thirty-fifth switch, the source of the twenty-ninth switch is connected to the drain of the thirty-third switch, the drain of the 30th switch is connected to the source of the thirty-fourth switch, the source of the thirty-third switch and the drain of the thirty-fourth switch are connected to the source of the thirty-sixth switch, the source of the thirty-fifth switch is connected to the drain of the thirty-sixth switch, the drain of the thirty-seventh switch is connected to the drain of the thirty-fifth switch, the source of the thirty-eighth switch is connected to the source of the thirty-sixth switch, and the source of the thirty-fifth switch and the source of the thirty-seventh switch are the output of the hybrid multi-level switch unit.

[0012] In a specific embodiment, 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, the first end of the seventh capacitor is connected to the drain of the thirty-ninth switch, and the second end of the seventh capacitor is connected to the source of the fortieth switch.

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

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

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

[0016] Beneficial effect: A three-phase single-stage AC / DC converter of the present invention can increase the number of levels of the input voltage of the resonant cavity and obtain a resonant current with smaller conduction loss. At the same time, the introduction of multi-level switches can reduce the stress of each high-frequency switch.

[0017] In order to make the above features and advantages of the invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The structure diagram of a three-phase single-stage AC / DC converter of the present invention is shown in FIG.

[0019] Figure 2 for Figure 1 A schematic diagram of a specific embodiment of a three-phase single-stage AC / DC converter.

[0020] Figure 3 for Figure 2 Voltage and current waveforms of the AC / DC rectifier circuit.

[0021] Figure 4(a) shows the voltage u PY Greater than voltage u NY The input voltage u of the LLC resonant cavity is LLC Waveform graph.

[0022] Figure 4(b) shows the voltage u PY Less than voltage u NY The input voltage u of the LLC resonant cavity is LLC Waveform graph.

[0023] FIG5( a ) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 in the 0-t1 phase.

[0024] FIG5( b ) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the period t1 - t2 .

[0025] FIG5( c ) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the period t2 - t3 .

[0026] Figure 5(d) shows t3-T s Schematic diagram of the switching logic of the 2-stage hybrid multi-level switch unit 221.

[0027] Figure 5(e) shows T s Schematic diagram of the switching logic of the hybrid multi-level switch unit 221 during the period t / 2–t4.

[0028] FIG5( f ) is a schematic diagram of the switching logic of the hybrid multi-level switch unit 221 during the period t4 - t5 .

[0029] FIG5( g ) is a schematic diagram of the switching logic of the hybrid multi-level switch unit 221 during the period t5 - t6 .

[0030] Figure 5(h) shows the relationship between t6 and T s Schematic diagram of the switching logic of the stage hybrid multi-level switch unit 221.

[0031] FIG6( a ) shows a second specific implementation of the hybrid multi-level switch unit 221 using a hybrid five-level switch network.

[0032] FIG6( b ) shows a third specific implementation manner in which the hybrid multi-level switch unit 221 adopts a hybrid five-level switch network.

[0033] FIG6( c ) shows a fourth specific implementation in which the hybrid multi-level switch unit 221 adopts a hybrid five-level switch network.

[0034] FIG. 7( a ) is a first specific implementation of a hybrid seven-level switch network.

[0035] FIG. 7( b ) is a second specific implementation of a hybrid seven-level switch network.

[0036] FIG. 7( c ) is a third specific implementation of a hybrid seven-level switch network.

[0037] Figure 8This is a specific implementation of the expanded multi-level switch network. DETAILED DESCRIPTION

[0038] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Figure 1 The structure diagram of a three-phase single-stage AC / DC converter of the present invention is shown in FIG. A 、u B 、u C Through the inductor L A 、Inductance L B 、Inductance L C The filter input is sent to the AC / DC rectifier circuit 11, the AC / DC rectifier circuit 11 outputs direct current to the three terminals PYN, and the DC / DC resonant circuit 12 converts the electric energy of the three terminals PYN to output the voltage V o To load R o The DC / DC resonant circuit 12 adjusts the output voltage V o and the three-phase alternating current i A 、i B 、i C , or adjust the output current I o and the three-phase alternating current i A 、i B 、i C .

[0040] Furthermore, the DC / DC resonant circuit 12 includes a hybrid multi-level switch unit 121 , a resonant conversion unit 122 and a rectifier unit 123 , and the hybrid multi-level switch unit 121 , the resonant conversion unit 122 and the rectifier unit 123 are sequentially connected in parallel.

[0041] Figure 2 for Figure 1 A schematic diagram of a specific embodiment of a three-phase single-stage AC / DC converter. Figure 2 As shown, the AC / DC rectifier circuit 21 is a Swiss rectifier circuit, and the AC / DC rectifier circuit 21 includes a bidirectional switch S ay , S by , S cy , bidirectional switch S ay , S by , S cyAt the moment when the two phase voltages intersect, the low-frequency switch is turned on. The bidirectional switch of the phase with the larger absolute value of the voltage amplitude of the two intersecting phases is turned off, and the bidirectional switch of the phase with the smaller amplitude is turned on. In this way, the phase with the larger amplitude of the forward voltage passes through the upper diode D u Connect to the P terminal, and the phase with the larger negative voltage amplitude passes through the lower diode D d Connect to the N terminal, and the remaining phase is connected through the conducting bidirectional switch S y Connect to the Y terminal, combined with Figure 3 , the three-phase AC voltage u A 、u B 、u C becomes voltage u P 、u N 、u Y , we get three positive line voltages u PN 、u PY and u YN , where u PN Always the largest one, the other two voltages u PY and u YN Alternate changes.

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

[0043] The DC / DC resonant circuit 22 includes a hybrid multi-level switch unit 221 , a resonant conversion unit 222 and a rectifier unit 223 , and the hybrid multi-level switch unit 221 , the resonant conversion unit 222 and the rectifier unit 223 are sequentially connected in parallel.

[0044] It should be noted that the hybrid multilevel switch unit 221 cannot adopt a common multilevel topology, such as a flying capacitor type multilevel topology or a midpoint clamp type multilevel topology. This is because the Swiss rectifier circuit is used for low-frequency rectification and does not perform power conversion. The capacitor C connected between the output terminals P, N, and Y PY , C YN , C PNIt is only responsible for filtering out the high-frequency components in the input current, and can only use film capacitors with small capacitance, and cannot use electrolytic capacitors with large capacitance. Since electrolytic capacitors cannot be used, ordinary multi-level topologies, such as flying capacitor multi-level topologies and mid-point clamped multi-level topologies, cannot create multi-levels. Therefore, the capacitors can only be moved to the DC / DC resonant circuit 22 to construct a hybrid multi-level switch topology.

[0045] In this specific embodiment, the hybrid multi-level switch unit 221 adopts a hybrid five-level switch network. The hybrid multi-level switch 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 both connected in parallel with the output of the AC / DC rectifier circuit 21. The output of the multi-level module 2211 is the output terminal a, and the output of the multi-level module 2212 is the 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, and the 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 capacitor C f1 The first end of the capacitor C f1 The second end of the switch S m3 The drain of the switch S m1 The source connection switch S m2 The drain of the switch S m3 The drain of the switch S m4 The source of the switch S m2 The source connection 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 the 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 capacitor C f2 The first end of the capacitor C f2 The second end of the switch S m7 The drain 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 connection 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 specific 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. 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 terminal a and output terminal 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 of the LLC resonant cavity is 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 arem1 , 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 of the LLC resonant cavity is LLC is the voltage u PN .

[0051] FIG5(c) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the t2-t3 period. As shown in FIG5(c), switches S1 and S2 are m1 , switch S m2 , switch S m6 , switch S m7 , switch S8 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 of the LLC resonant cavity is LLC is the voltage u PN -u cf , where voltage u cf is the capacitance C f2 The voltage across the two ends, t3 is D PN T s .

[0052] Figure 5(d) shows t3-T s The switch logic diagram of the hybrid multi-level switch unit 221 of the / 2 stage is shown in FIG5(d), where switch S1, switch S m1 , switch S m2 , switch S m6 , switch S m7 , switch S7 is turned on to form a loop, and the current flows from the Y end to the P end. At this time, the input voltage u of the LLC resonant cavity is LLC is the voltage u PY -u cf , where voltage u cf is the capacitance C f2 The voltage across both ends.

[0053] Figure 5(e) shows T s The switch logic diagram of the hybrid multi-level switch unit 221 during the period of / 2–t4 is shown in FIG5(e), where switch S4, switch S m3 , switch S m4 , switch S m6 , switch S m5 , switch S5 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 of the LLC resonant cavity is LLC is the voltage-u PN .

[0054] FIG5(f) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the t4-t5 period. As shown in FIG5(f), switches S4 and S m3 , switch S m4 , switch S m6 , switch S m5 , switch S5 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 of the LLC resonant cavity is LLC is the voltage-u PN .

[0055] FIG5(g) is a schematic diagram of the switch logic of the hybrid multi-level switch unit 221 during the period t5-t6. As shown in FIG5(g), switches S5 and S m5 , switch S m8 , switch S m4 , switch S m3 , switch S4 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 of the LLC resonant cavity is LLC is the voltage-u PN +u cf , where voltage u cf is the capacitance C f2 The voltage across the two ends, t6 is T s / 2+D PN T s .

[0056] Figure 5(h) shows the relationship between t6 and T s The switch logic diagram of the hybrid multi-level switch unit 221 is shown in FIG5(h), where switch S5, switch S m5 , switch S m8 , switch S m4 , switch S m3 , switch S3 is turned on to form a loop, and the current flows from the Y end to the P end. At this time, the input voltage u of the LLC resonant cavity is LLC is the voltage-u PY +u cf , where voltage u cf is the capacitance C f2 The voltage across both ends.

[0057] Figure 6(a) to Figure 6(c) Other specific implementations of the hybrid multi-level switch unit 221 using a hybrid five-level switch network.

[0058] In the hybrid multi-level switch unit 621a of FIG6(a), the inputs of the multi-level module 6211a and the multi-level module 6212a are connected in parallel with the output of the AC / DC rectifier 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, and the source of the switch S9 is connected to the switch S 10 The drain of the switch S 10 The source connection switch S 11 The drain of the switch S 11 The source connection 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 m10 The drain of the switch S m10 The source connection switch S m9 The source of the switch S m9 The drain of the switch is connected to the Y terminal. 11 The source connection switch S m12 The drain of the switch S m12 The source connection switch S m11 The source of the switch S m11 The drain of the capacitor is connected to the Y terminal, and the capacitor C f3 One end of the switch S m10 The drain capacitor C f3 The other end is connected to the switch S m12 The drain of switch S 13 The drain of the switch is connected to the P terminal, and the switch S 13 The source connection switch S 14 The drain of the switch S 14 The source connection S 15 The drain of the switch S 15 The source connection switch S 16 The drain of the switch S 16 The source of the switch S is connected to the N terminal. 13 The source connection switch S m14 The drain of the switch S m14 The source connection switch S m13 The source of the switch S m13 The drain of the switch is connected to the Y terminal. 15 The source connection switch S m16 The drain of the switch S m16 The source connection switch S m15 The source of the switch S m15 The drain of the capacitor is connected to the Y terminal, and the capacitor C f4 One end of the switch S m14 The drain capacitor C f4 The other end is connected to the switch S m16The drain of switch S 10 The source of is the output terminal a, and the switch S 14 The source of is the output terminal b.

[0059] In the hybrid multi-level switch unit 621b of FIG6(b), the inputs of the multi-level module 6211b and the multi-level module 6212b are connected in parallel with 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, and the switch S 17 The drain of the switch is connected to the P terminal, and the switch S 17 The source connection capacitor 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 of 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 capacitor 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 S is connected to the N terminal. 17 The source connection switch S m17 The drain of the switch S 18 The drain of the switch S m18 The source of the switch S m17 The source and switch S m18 The drain of the switch S m21 The drain of switch S 19 The source connection switch S m19 The drain of the switch S 20 The drain of the switch S m20 The source of the switch S m19 The source and switch S m20 The drain of the switch S m22 The source of the switch S m21 The source and switch S m22 The drains of the switches S are connected together to form the output terminal a. 21 The drain of the switch is connected to the P terminal, and the switch S 21 The source connection capacitor C f7 The first end of the capacitor C f7 The second end of the switch S 22 The drain of the switch S 22 The source of is connected to the Y terminal, and the Y terminal is connected to the switch S 23 The drain of switch S23 is connected to the capacitor C f8 The first end of the capacitor C f8 The second end of the switch S24 The drain of the switch S 24 The source of the switch S is connected to the N terminal. 21 The source connection 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 connection 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 multilevel switch unit 621c of FIG. 6( c ), the switch S 25 The drain of the switch is connected to the P terminal, and the switch S 25 The source connection capacitor 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 of 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 capacitor 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 S is connected to the N terminal. 25 The source connection 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 connection 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 connection 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 connection switch S m34 The source of the switch S m33 The source of is the output terminal a, and the switch S m35 The source of is the output terminal b.

[0061] Flying electrolytic capacitor C in hybrid multilevel switch cell f It has the following functions. First, it helps some or all high-frequency switches to withstand certain voltage stress. Normal withstand voltage 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. Second, 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 capacitor 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, and continuing to increase the multi-level switch network can bring the following benefits: increasing the number of levels can expand the gain range of the converter; the increase 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] Figure 7(a) to Figure 7(c) The schematic diagram of a circuit for expanding a hybrid five-level switch network into a hybrid seven-level switch network.

[0065] In the hybrid multi-level switch unit 721a in FIG7(a), the inputs of the multi-level module 7211a and the multi-level module 7212a are connected in parallel with the output of the AC / DC rectifier circuit 21, the output of the multi-level module 7211a is the output terminal a, and the output of the multi-level module 7212a is the output terminal b. Figure 2 The hybrid multi-level switch unit 221 is based on the additional 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 capacitor 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 connection 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 capacitor 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 connection 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 connection 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 the 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 capacitor 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 capacitor 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 connection 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 connection 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 connection 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 connection 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 connection switch S m9 The source of the switch S m9 The drain of the switch is connected to the Y terminal. 11 The source connection switch S m44 The drain of the switch S m44The source connection switch S m43 The source of the switch S m43 The drain of the switch S m12 The drain of the switch S m12 The source connection switch S m11 The source of the switch S m11 The drain of the capacitor is connected to the Y terminal, and the capacitor C f3 One end of the switch S m10 The drain capacitor C f3 The other end is connected to the switch S m12 The drain of the switch S m42 The drain connection capacitance C f13 The first end of the capacitor C f13 The second end of the switch S m44 The drain of switch S 13 The drain of the switch is connected to the P terminal, and the switch S 13 The source connection switch S 14 The drain of the switch S 14 The source connection S 15 The drain of the switch S 15 The source connection switch S 16 The drain of the switch S 16 The source of the switch S is connected to the N terminal. 13 The source connection switch S m46 The drain of the switch S m46 The source connection switch S m45 The source of the switch S m45 The drain of the switch S m14 The drain of the switch S m14 The source connection switch S m13 The source of the switch S m13 The drain of the switch is connected to the Y terminal. 15 The source connection switch S m48 The drain of the switch S m48 The source connection switch S m47 The source of the switch S m47 The drain of the switch S m16 The drain of the switch S m16 The source connection switch S m15 The source of the switch S m15 The drain of the capacitor is connected to the Y terminal, and the capacitor C f4 One end of the switch S m14 The drain capacitor C f4 The other end is connected to the switch S m16 The drain capacitor C f14 One end of the switch S m46 The drain capacitor C f14 The other end is connected to the switch Sm48 The drain of the switch S 10 The source of is the output terminal a, and the switch S 14 The source of 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 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 on the basis of 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 capacitor 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 of 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 capacitor 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 S is connected to the N terminal. 17 The source connection switch S 29 The drain of the switch S 29 The source connection capacitor 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 connection switch S 31 The drain of the switch S 31 The source connection capacitor 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 connection 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 connection 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 and switch S m18 The drain of the switch S m21 The drain of switch S 31 The source connection 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 and switch S m20 The drain of the switch S m22 The source of the switch S m21 The source and switch S m22 The drains of the switches S are connected together to form the output terminal a. 21 The drain of the switch is connected to the P terminal, and the switch S 21 The source connection capacitor C f7 The first end of the capacitor C f7 The second end of the switch S 22 The drain of the switch S 22 The source of is connected to the Y terminal, and the Y terminal is connected to the switch S 23 The drain of the switch S 23 The source connection capacitor C f8 The first end of the capacitor C f8 The second end of the switch S 24 The drain of the switch S 24 The source of the switch S is connected to the N terminal. 21 The source connection switch S 33 The drain of the switch S 33 The source connection capacitor C f17 The first end of the capacitor C f17 The second end of the switch S 34 The drain of the switch S 34 The source connection switch S 22 The drain of the switch S 23 The source of the switch S 34 The source connection switch S 35 The drain of the switch S 35 The source connection capacitor C f18 The first end of the capacitor C f18 The second end of the switch S 36 The drain of the switch S 36 The source connection switch S 24 The drain of switch S33 The source connection 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 connection 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 FIG. 7( a ) as an example, the expanded multi-level switch network is as follows: Figure 8 As shown, in 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 as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims

1. A three-phase single-stage AC / DC converter, characterized in that: It includes 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 power to the input of the DC / DC resonant circuit, the DC / DC resonant circuit outputs a DC voltage, and the DC / DC resonant circuit includes a hybrid multi-level switch unit, a resonant conversion unit and a rectifier unit, and the hybrid multi-level switch unit, the resonant conversion unit and the rectifier unit are sequentially connected in parallel.

2. A three-phase single-stage AC / DC converter as claimed in claim 1, characterized in that: 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 ends 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 end 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 end 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, the source of the fourth switch is connected to the third output end 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 end of the first capacitor, the second end 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 be the output of the first multi-level module.

3. A three-phase single-stage AC / DC converter as claimed in claim 1, characterized in that: The hybrid multi-level switch unit includes two second multi-level modules, the inputs of the two second multi-level modules are connected in parallel and connected to the output of the AC / DC rectifier circuit, the outputs of the two second multi-level modules are respectively connected to the two input ends of the resonant conversion unit, the second multi-level module includes a plurality of switches and a plurality of capacitors, the drain of the ninth switch is connected to the first output end of the AC / DC rectifier circuit, the source of the ninth switch is connected to the drain of the tenth switch, the source of the tenth switch is connected to the drain of the eleventh switch, the source of the eleventh switch is connected to the drain of the twelfth switch, the source of the twelfth switch is connected to the AC / DC rectifier circuit, and the drain of the twelfth switch is connected to the drain of the twelfth switch. The third output terminal of the AC / DC rectifier circuit is connected to the third output terminal of the AC / DC rectifier circuit, the source of the ninth switch is connected to the drain of the thirteenth switch, the source of the thirteenth switch is connected to the source of the fourteenth switch, the drain of the fourteenth switch is connected to the second output terminal of the AC / DC rectifier circuit, the source of the eleventh switch is connected to the drain of the fifteenth switch, the source of the fifteenth switch is connected to the source of the sixteenth switch, the drain of the sixteenth switch is connected to the second output terminal of the AC / DC rectifier circuit, the first end of the second capacitor is connected to the drain of the thirteenth switch, the second end of the second capacitor is connected to the drain of the fifteenth switch, and the source of the tenth switch is the output of the second multi-level module.

4. A three-phase single-stage AC / DC converter as claimed in claim 1, characterized in that: The hybrid multi-level switch unit comprises two third multi-level modules, the inputs of the two third multi-level modules are connected in parallel and connected to the output of the AC / DC rectifier circuit, the outputs of the two third multi-level modules are respectively connected to the two input ends of the resonant conversion unit, the third multi-level module comprises a plurality of switches and a plurality of capacitors, the drain of a seventeenth switch is connected to the first output end of the AC / DC rectifier circuit, the source of the seventeenth switch is connected to the first end of the third capacitor, the second end of the third capacitor is connected to the drain of an eighteenth switch, the source of the eighteenth switch is connected to the second output end of the AC / DC rectifier circuit, the second output end of the AC / DC rectifier circuit is connected to the drain of a nineteenth switch, the source of the nineteenth switch is connected to the fourth capacitor, The first end of the fourth capacitor is connected to the drain of the twentieth switch, the second end of the fourth capacitor is connected to the drain of the twentieth switch, the source of the twentieth switch is connected to the third output end of the AC / DC rectifier circuit, the source of the seventeenth switch is connected to the drain of the twenty-first switch, the drain of the eighteenth switch is connected to the source of the twenty-second switch, the source of the twenty-first switch and the drain of the twenty-second switch are connected to the drain of the twenty-third switch, the source of the nineteenth switch is connected to the drain of the twenty-fourth switch, the drain of the twentieth switch is connected to the source of the twenty-fifth switch, the source of the twenty-fourth switch and the drain of the twenty-fifth switch are connected to the source of the twenty-sixth switch, and the source of the twenty-third switch and the drain of the twenty-sixth switch are connected to form the output of the third multi-level module.

5. A three-phase single-stage AC / DC converter as claimed in claim 1, characterized in that: The hybrid multi-level switch unit includes a plurality of switches and a plurality of capacitors, the drain of a twenty-seventh switch is connected to the first output terminal of the AC / DC rectifier circuit, the source of the twenty-seventh switch is connected to the first end of a fifth capacitor, the second end of the fifth capacitor is connected to the drain of a twenty-eighth switch, the source of the twenty-eighth switch is connected to the second output terminal of the AC / DC rectifier circuit, the second output terminal of the AC / DC rectifier circuit is connected to the drain of a twenty-ninth switch, the source of the twenty-ninth switch is connected to the first end of a sixth capacitor, the second end of the sixth capacitor is connected to the drain of a thirtieth switch, the source of the thirtieth switch is connected to the third output terminal of the AC / DC rectifier circuit, the source of the twenty-seventh switch is connected to the drain of a thirty-first switch, and the third output terminal of the AC / DC rectifier circuit is connected to the drain of a thirty-first switch. The drain of the twenty-eighth switch is connected to the source of the thirty-second switch, the source of the thirty-first switch and the drain of the thirty-second switch are connected to the drain of the thirty-fifth switch, the source of the twenty-ninth switch is connected to the drain of the thirty-third switch, the drain of the 30th switch is connected to the source of the thirty-fourth switch, the source of the thirty-third switch and the drain of the thirty-fourth switch are connected to the source of the thirty-sixth switch, the source of the thirty-fifth switch is connected to the drain of the thirty-sixth switch, the drain of the thirty-seventh switch is connected to the drain of the thirty-fifth switch, the source of the thirty-eighth switch is connected to the source of the thirty-sixth switch, and the source of the thirty-fifth switch and the source of the thirty-seventh switch are the output of the hybrid multi-level switch unit.

6. A three-phase single-stage AC / DC converter as claimed in claim 2, 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, the first end of the seventh capacitor is connected to the drain of the thirty-ninth switch, and the second end of the seventh capacitor is connected to the source of the fortieth switch.

7. A three-phase single-stage AC / DC converter as claimed in claim 3, characterized in that: 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 the 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 the 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 end of the eighth capacitor is connected to a drain of the forty-first switch, and a second end of the eighth switch is connected to a drain of the forty-third switch.

8. A three-phase single-stage AC / DC converter as claimed in claim 4, characterized in that: The third multi-level module further includes a plurality of switches and a plurality of capacitors, a drain of a 45th switch is connected to a source of a 17th switch, a source of the 45th switch is connected to a first end of a 9th capacitor, a second end of the 9th capacitor is connected to a drain of a 46th switch, a source of the 46th switch is connected to a drain of a 47th switch, a source of the 47th switch is connected to a first end of a 10th capacitor, a second end of the 10th capacitor is connected to a drain of a 48th switch, a source of the 48th switch is connected to a drain of the 20th switch, a drain of the 47th switch is connected to a drain of the 18th switch and a source of the 19th switch, a source of the 45th switch is connected to a drain of the 21st switch, a drain of the 46th switch is connected to a source of the 22nd switch, a source of the 47th switch is connected to a drain of the 24th switch, and a drain of the 48th switch is connected to a source of the 25th switch.

9. A three-phase single-stage AC / DC converter as claimed in claim 6, characterized in that: The first multi-level module further includes a plurality of forty-ninth switches, a plurality of fiftieth switches and a plurality of eleventh capacitors, wherein the plurality of forty-ninth switches are connected in series in the same direction between the seventh switch and the thirty-ninth switch, the plurality of fiftieth switches are connected in series in the same direction between the eighth switch and the fortieth switch, and the eleventh capacitor is connected in series between the drain of each forty-ninth switch and the source of each fiftieth switch.

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