Two-stage multi-level conversion circuit

Abstract

The utility model discloses a two-stage multi-level conversion circuit, which comprises a pre-stage circuit and a post-stage circuit which are connected through a direct current bus comprising a positive bus and a negative bus, the pre-stage circuit comprises one or more DC / DC conversion circuits of which the output ends are connected in parallel, and the post-stage circuit comprises one or more DC / AC conversion circuits of which the input ends are connected in parallel. The DC / DC conversion circuit is connected with the DC / AC conversion circuit through a DC bus, a first capacitor branch and a second capacitor branch which are connected in parallel and respectively comprise a plurality of capacitors connected in series are arranged between the positive bus and the negative bus, and the midpoint of the output end of the DC / DC conversion circuit and the midpoint of the input end of the DC / AC conversion circuit are respectively connected with the midpoints of the corresponding capacitor branches. The DC / DC conversion circuit is a multi-level DC / DC conversion circuit topology of which the level number is not less than 3, and the DC / AC conversion circuit is a multi-level DC / AC conversion circuit topology of which the level number is not less than 3.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to a two-stage multilevel conversion circuit. Background Technology

[0002] With the rise of new energy power generation technologies such as photovoltaic power generation, the application scope of DC power conversion and inversion is becoming increasingly wide. In existing conversion circuits, mutual interference is easily generated between DC / DC conversion circuits and DC / AC conversion circuits. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a two-stage multilevel conversion circuit to reduce interference between DC / DC conversion circuits and DC / AC conversion circuits.

[0004] To solve the above-mentioned technical problems, this utility model provides a two-stage multilevel converter circuit, including a front-end circuit and a rear-end circuit, which are connected by a DC bus. The front-end circuit includes a DC / DC converter circuit or multiple DC / DC converter circuits with their output terminals connected in parallel. The rear-end circuit includes a DC / AC converter circuit or multiple DC / AC converter circuits with their input terminals connected in parallel. The DC / DC converter circuit and the DC / AC converter circuit are connected by the DC bus, which includes a positive bus and a negative bus. A first capacitor branch and a second capacitor branch are connected in parallel between the negative busbars. The first capacitor branch and the second capacitor branch each include multiple capacitors connected in series in sequence. The midpoint of the output terminal of the DC / DC converter circuit is connected to the midpoint of the first capacitor branch, and the midpoint of the input terminal of the DC / AC converter circuit is connected to the midpoint of the second capacitor branch. The DC / DC converter circuit adopts a multi-level DC / DC converter circuit topology with a level number of not less than 3; the DC / AC converter circuit adopts a multi-level DC / AC converter circuit topology with a level number of not less than 3.

[0005] The further technical solution is that the DC / DC conversion circuit is a boost circuit, a buck circuit, or a buck-boost circuit.

[0006] The further technical solution is that the DC / AC conversion circuit is a single-phase circuit or a three-phase circuit.

[0007] The further technical solution is that the three-phase circuit is a three-phase three-wire circuit or a three-phase four-wire circuit.

[0008] The further technical solution is as follows: the DC / DC conversion circuit includes at least one inductor, at least two controllable semiconductor switches and at least two diodes.

[0009] A further technical solution is as follows: the DC / DC conversion circuit can be a flying capacitor type BOOST circuit, including a first inductor, a first controllable semiconductor switch, a second controllable semiconductor switch, a first diode, a second diode, a third diode, a fourth diode, and a flying capacitor. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch and the anode of the first diode through the first inductor. The power output terminal of the first controllable semiconductor switch is connected to the power input terminal of the second controllable semiconductor switch and the anode of the third diode. The power output terminal of the second controllable semiconductor switch is connected to the negative terminal of the voltage input and the negative bus. The cathode of the first diode is connected to the anode of the flying capacitor, the cathode of the fourth diode, and the anode of the second diode. The cathode of the flying capacitor is connected to the power output terminal of the first controllable semiconductor switch, the power input terminal of the second controllable semiconductor switch, and the anode of the third diode. The cathode of the third diode is connected to the anode of the fourth diode and the midpoint of the first capacitor branch. The cathode of the second diode is connected to the positive bus.

[0010] A further technical solution is as follows: the DC / DC conversion circuit can be a three-level BOOST circuit, including a first inductor, a first controllable semiconductor switch, a second controllable semiconductor switch, a fifth diode, and a sixth diode. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch and the anode of the fifth diode through the first inductor. The cathode of the fifth diode is connected to the positive bus. The power output terminal of the first controllable semiconductor switch is connected to the power input terminal of the second controllable semiconductor switch and the midpoint of the first capacitor branch. The power output terminal of the second controllable semiconductor switch is connected to the negative terminal of the voltage input and the cathode of the sixth diode. The anode of the sixth diode is connected to the negative bus.

[0011] The further technical solution is as follows: the DC / AC conversion circuit includes at least one inductor and at least two controllable semiconductor switches.

[0012] The beneficial technical effects of this utility model are as follows: The two-stage multilevel converter circuit of this utility model is configured with a front-end circuit including at least one DC / DC converter circuit, a rear-end circuit including at least one DC / AC converter circuit, and a DC bus connecting the front-end circuit and the rear-end circuit. The output terminals of multiple DC / DC converter circuits are connected in parallel, and the input terminals of multiple DC / AC converter circuits are connected in parallel. The DC / DC converter circuit and the DC / AC converter circuit are connected through the DC bus. A first capacitor branch and a second capacitor branch are connected in parallel between the positive and negative buses of the DC bus. The first capacitor branch and the second capacitor branch each include multiple capacitors connected in series in sequence. The output of the DC / DC converter circuit... The midpoint of the output terminal is connected to the midpoint of the first capacitor branch, and the midpoint of the input terminal of the DC / AC converter circuit is connected to the midpoint of the second capacitor branch. However, the midpoint of the first capacitor branch is not connected to the midpoint of the second capacitor branch. This allows for separate control of the midpoint voltage of the DC / DC converter circuit and the midpoint voltage of the DC / AC converter circuit, while ensuring the DC bus voltage is supplied. This reduces coupling and prevents mutual influence and interference between the DC / DC converter circuit and the DC / AC converter circuit. The midpoint voltage of the DC / DC converter circuit is stabilized at half the bus voltage, which prevents voltage fluctuations that could affect the circuit and helps reduce the fluctuation of the inductor ripple current in the DC / DC converter circuit. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A schematic diagram of the topology of an embodiment of the two-stage multilevel converter circuit provided by this utility model;

[0015] Figure 2 for Figure 1 A schematic diagram of the topology of a first specific embodiment of the two-stage multilevel converter circuit shown.

[0016] Figure 3 for Figure 1 A schematic diagram of the topology of a second specific embodiment of the two-stage multilevel converter circuit shown;

[0017] Figure 4 for Figure 1 A schematic diagram of the topology of the third specific embodiment of the two-stage multilevel converter circuit shown;

[0018] Figure 5 for Figure 1The topology diagram of the fourth specific embodiment of the two-stage multilevel converter circuit shown is as follows;

[0019] Figure 6 A schematic diagram of the topology of another embodiment of the two-stage multilevel converter circuit provided by this utility model. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0021] Please see Figure 1 , Figure 1 This is a schematic diagram of the topology of an embodiment of the two-stage multilevel converter circuit provided by this utility model. The two-stage multilevel converter circuit includes a front-end circuit 11 and a rear-end circuit 12, which are connected by a DC bus. The front-end circuit 11 includes a DC / DC converter circuit 111, and the rear-end circuit 12 includes a DC / AC converter circuit 121. The DC / DC converter circuit 111 and the DC / AC converter circuit 121 are connected by the DC bus, which includes a positive bus BUS+ and a negative bus BUS-. A phase connection is provided between the positive bus BUS+ and the negative bus BUS-. The first capacitor branch 101 and the second capacitor branch 102 are connected in parallel. The first capacitor branch 101 and the second capacitor branch 102 each include a plurality of capacitors connected in series in sequence. The midpoint of the output terminal of the DC / DC converter circuit 111 is connected to the midpoint N' of the first capacitor branch 101. The midpoint of the input terminal of the DC / AC converter circuit 121 is connected to the midpoint N of the second capacitor branch 102. The DC / DC converter circuit 111 adopts a multi-level DC / DC converter circuit 111 topology with a level number of not less than 3. The DC / AC converter circuit 121 adopts a multi-level DC / AC converter circuit 121 topology with a level number of not less than 3.

[0022] The two-stage multilevel converter circuit comprises a front-end circuit 11 including at least one DC / DC converter 111, a rear-end circuit 12 including at least one DC / AC converter 121, and a DC bus connecting the front-end circuit 11 and the rear-end circuit 12. The outputs of multiple DC / DC converters 111 are connected in parallel, and the inputs of multiple DC / AC converters 121 are connected in parallel. The DC / DC converters 111 and 121 are connected via the DC bus. A first capacitor branch 101 and a second capacitor branch 102 are connected in parallel between the positive bus BUS+ and the negative bus BUS- of the DC bus. The first capacitor branch 101 and the second capacitor branch 102 each include multiple capacitors connected in series. The output of the DC / DC converter 111... The midpoint is connected to the midpoint N' of the first capacitor branch 101, and the midpoint of the input terminal of the DC / AC converter circuit 121 is connected to the midpoint N of the second capacitor branch 102. However, the midpoint N' of the first capacitor branch 101 is not connected to the midpoint N of the second capacitor branch 102. This allows for separate control of the bus midpoint voltage of the DC / DC converter circuit 111 and the bus midpoint voltage of the DC / AC converter circuit 121, while ensuring the DC bus voltage is supplied. This reduces coupling and prevents mutual influence and interference between the DC / DC converter circuit 111 and the DC / AC converter circuit 121. The midpoint voltage of the DC / DC converter circuit 111 is stabilized at half the bus voltage, which can prevent voltage fluctuations that affect the circuit and help reduce the fluctuation of the inductor ripple current of the DC / DC converter circuit 111.

[0023] Of course, in some embodiments, the front-end circuit 11 includes a plurality of DC / DC conversion circuits 111, and the output terminals of the plurality of DC / DC conversion circuits 111 are connected in parallel, and the rear-end circuit 12 includes a plurality of DC / AC conversion circuits 121, and the input terminals of the plurality of DC / AC conversion circuits 121 are connected in parallel. Figure 6 Another embodiment of a two-stage multilevel converter circuit is shown, such as... Figure 6 As shown, the front-end circuit 11 includes two DC / DC converter circuits 111, and the output terminals of the two DC / DC converter circuits 111 are connected in parallel. The rear-end circuit 12 includes two DC / AC converter circuits 121, and the input terminals of the two DC / AC converter circuits 121 are connected in parallel. The DC / DC converter circuits 111 and 121 are connected through a DC bus. The midpoint of the output terminal of each DC / DC converter circuit 111 is connected to the midpoint N' of the first capacitor branch 101, and the midpoint of the input terminal of each DC / AC converter circuit 121 is connected to the midpoint N of the second capacitor branch 102.

[0024] Preferably, the first capacitor branch 101 includes a first capacitor C1 and a second capacitor C2 connected in series. The first terminal of the first capacitor C1 is connected to the positive busbar BUS+, the second terminal of the first capacitor C1 is connected to the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the negative busbar BUS-. The midpoint N' of the first capacitor branch 101 is located between the first capacitor C1 and the second capacitor C2. The second capacitor branch 102 includes a third capacitor C3 and a fourth capacitor C4 connected in series. The first terminal of the third capacitor C3 is connected to the positive busbar BUS+, the second terminal of the third capacitor C3 is connected to the first terminal of the fourth capacitor C4, and the second terminal of the fourth capacitor C4 is connected to the negative busbar BUS-. The midpoint N of the second capacitor branch 102 is located between the third capacitor C3 and the fourth capacitor C4. The first capacitor branch 101 and the second capacitor branch 102 each include multiple capacitors connected in series, allowing for the use of smaller capacitors while maintaining the original equivalent capacitance value, thus reducing costs.

[0025] Specifically, in terms of power flow direction, the DC / DC converter circuit 111 can be a boost circuit, a buck circuit, or a buck-boost circuit.

[0026] Specifically, the DC / DC converter circuit 111 includes at least one inductor, at least two controllable semiconductor switches, and at least two diodes.

[0027] Preferably, Figure 2 The topology of a first specific embodiment of a two-stage multilevel converter circuit is shown, such as... Figure 2As shown, the DC / DC converter circuit 111 is a flying capacitor type BOOST circuit, including a first inductor L, a first controllable semiconductor switch Q1, a second controllable semiconductor switch Q2, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, and a flying capacitor Cfly. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch Q1 and the anode of the first diode D1 through the first inductor L. The power output terminal of the first controllable semiconductor switch Q1 is connected to the power input terminal of the second controllable semiconductor switch Q2 and the anode of the third diode D3. The second controllable semiconductor switch Q2... The power output terminal of the first diode D1 is connected to the negative terminal of the voltage input and the negative bus BUS-. The cathode of the first diode D1 is connected to the anode of the flying capacitor Cfly, the cathode of the fourth diode D4, and the anode of the second diode D2. The cathode of the flying capacitor Cfly is connected to the power output terminal of the first controllable semiconductor switch Q1, the power input terminal of the second controllable semiconductor switch Q2, and the anode of the third diode D3. The cathode of the third diode D3 is connected to the anode of the fourth diode D4 and the midpoint N' of the first capacitor branch 101. The cathode of the second diode D2 is connected to the positive bus BUS+. The cathode of the second diode D2 is connected to the first terminal of the first capacitor C1, the cathode of the third diode D3 is connected to the second terminal of the first capacitor C1 and the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the negative bus BUS-, thus connecting to the negative terminal of the voltage input. During the transient process of the voltage rise of the flying capacitor Cfly, when both the first controllable semiconductor switch Q1 and the second controllable semiconductor switch Q2 are in the off mode, the voltage of the flying capacitor Cfly is less than the voltage across the first capacitor C1 in the first capacitor branch 101. The current flow path is the first inductor L, the first diode D1, the flying capacitor Cfly, the third diode D3, and the second capacitor C2. The charging voltages of the flying capacitor Cfly and the second capacitor C2 rise simultaneously. Since the midpoint N' of the first capacitor branch 101 is not connected to the midpoint N of the second capacitor branch 102, the sum of the voltages across the first capacitor C1 and the second capacitor C2 is the bus voltage. As the voltage across the second capacitor C2 rises, the voltage across the first capacitor C1 falls. At this time, the voltage of the flying capacitor Cfly can rise to a level higher than the voltage across the first capacitor C1 more quickly, without being clamped by the bus midpoint voltage. This reduces the time for the third diode D3 to carry current, avoids overheating and damage to the third diode D3, and increases the reliability of the circuit.

[0028] Specifically, Figure 3 The topology of a second specific embodiment of a two-stage multilevel converter circuit is shown, such as... Figure 3As shown, the DC / DC converter circuit 111 is a three-level BOOST circuit, including a first inductor L, a first controllable semiconductor switch Q1, a second controllable semiconductor switch Q2, a fifth diode D5, and a sixth diode D6. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch Q1 and the anode of the fifth diode D5 through the first inductor L. The cathode of the fifth diode D5 is connected to the positive bus BUS+. The power output terminal of the first controllable semiconductor switch Q1 is connected to the power input terminal of the second controllable semiconductor switch Q2 and the midpoint N' of the first capacitor branch 101. The power output terminal of the second controllable semiconductor switch Q2 is connected to the negative terminal of the voltage input and the cathode of the sixth diode D6. The anode of the sixth diode D6 is connected to the negative bus BUS-. In this configuration, the cathode of the fifth diode D5 is connected to the first terminal of the first capacitor C1, the power output terminal of the first controllable semiconductor switch Q1 is connected to the second terminal of the first capacitor C1 and the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the negative bus BUS- and the anode of the sixth diode D6, so that the anode of the sixth diode D6 is connected to the negative voltage input terminal.

[0029] Specifically, in terms of the number of phases, the DC / AC conversion circuit 121 can be a single-phase circuit or a three-phase circuit.

[0030] Preferably, the three-phase circuit can be a three-phase three-wire circuit or a three-phase four-wire circuit.

[0031] Specifically, the DC / AC conversion circuit 121 includes at least one inductor and at least two controllable semiconductor switches.

[0032] Preferably, Figure 4 The topology of a third specific embodiment of a two-stage multilevel converter circuit is shown, such as... Figure 4As shown, the DC / AC conversion circuit 121 can be a single-phase type I inverter bridge circuit. The DC / AC conversion circuit 121 includes an eleventh inductor L11, an eleventh diode D11, a twelfth diode D12, and a switch branch 122 composed of four sequentially connected controllable semiconductor switches. One end of the eleventh inductor L11 serves as the output terminal of the DC / AC conversion circuit 121, and the other end of the eleventh inductor L11 is connected to the midpoint of the switch branch 122. The power input terminal of the first controllable semiconductor switch serves as the input terminal of the switch branch 122 and is connected to the positive bus BUS+ and the first terminal of the third capacitor C3. The power output terminal of the last controllable semiconductor switch is connected to the negative bus BUS- and the second terminal of the fourth capacitor C4. The cathode of the eleventh diode D11 is connected to the power output terminal of the first controllable semiconductor switch and the power input terminal of the second controllable semiconductor switch. The anode of the eleventh diode D11 is connected to the cathode of the twelfth diode D12. The anode of the twelfth diode D12 is connected to the power output terminal of the second controllable semiconductor switch and the power input terminal of the third controllable semiconductor switch. The eleventh diode D11 and the twelfth diode D12 form a diode branch. The midpoint of the diode branch serves as the midpoint of the input terminal of the DC / AC converter circuit 121 and is connected to the second terminal of the third capacitor C3 and the first terminal of the fourth capacitor C4.

[0033] Preferably, Figure 5 The topology of a fourth specific embodiment of a two-stage multilevel converter circuit is shown, such as... Figure 5As shown, the DC / AC conversion circuit 121 can be a three-phase T-type inverter bridge circuit. The DC / AC conversion circuit 121 includes three inductors, three reverse switch branches 123, and three non-inverting switch branches 124. The reverse switch branches 123 and non-inverting switch branches 124 are connected in a one-to-one correspondence. The output terminal of the reverse switch branch 123 is connected to the midpoint of the corresponding non-inverting switch branch. The inductors are connected in a one-to-one correspondence with the non-inverting switch branches 124. One end of the inductor serves as the output terminal of the DC / AC conversion circuit 121, and the other end of the inductor is connected to the midpoint of the corresponding non-inverting switch branch 124. The other end of the inductor is then connected to the output terminal of the corresponding reverse switch branch 123. The input terminal of the reverse switch branch 123 is connected to the midpoint N of the second capacitor branch 102. Therefore, the input terminal of the reverse switch circuit is connected to the second terminal of the third capacitor C3 and the first terminal of the fourth capacitor C4. The reverse switch branch 123 includes two controllable semiconductor switches with their power output terminals connected. The power input terminal of one controllable semiconductor switch serves as the input terminal of the reverse switch branch 123, and the power input terminal of the other controllable semiconductor switch serves as the output terminal of the reverse switch branch 123. The same-direction switch branch 124 includes two controllable semiconductor switches. The power input terminal of one controllable semiconductor switch is connected to the positive bus BUS+, and the power output terminal of this controllable semiconductor switch is connected to the power input terminal of the other controllable semiconductor switch. The power output terminal of the other controllable semiconductor switch is connected to the negative bus BUS-. The midpoint of the same-direction switch branch 124 is between the power output terminal of the controllable semiconductor switch and the power input terminal of the other controllable semiconductor switch.

[0034] Preferably, the controllable semiconductor switch in the two-stage multilevel conversion circuit is an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a GaN (Gallium Nitride) device, but is not limited thereto.

[0035] When the controllable semiconductor switch is an IGBT, the power input terminal of the controllable semiconductor switch is the collector of the IGBT, and the power output terminal of the controllable semiconductor switch is the emitter of the IGBT; when the controllable semiconductor switch is a MOSFET, the power input terminal of the controllable semiconductor switch is the drain of the MOSFET, and the power output terminal of the controllable semiconductor switch is the source of the MOSFET; when the controllable semiconductor switch is a GaN, the power input terminal of the controllable semiconductor switch is the drain of the GaN, and the power output terminal of the controllable semiconductor switch is the source of the GaN.

[0036] In summary, the two-stage multilevel converter circuit of this utility model comprises a pre-stage circuit including at least one DC / DC converter, a post-stage circuit including at least one DC / AC converter, and a DC bus connecting the pre-stage and post-stage circuits. The outputs of multiple DC / DC converters are connected in parallel, and the inputs of multiple DC / AC converters are connected in parallel. The DC / DC converters and DC / AC converters are connected via the DC bus. A first capacitor branch and a second capacitor branch are connected in parallel between the positive and negative DC bus. Each of the first and second capacitor branches includes multiple capacitors connected in series. The midpoint of the output of the DC / DC converter is... The input terminal of the DC / AC converter circuit is connected to the midpoint of the first capacitor branch, and the midpoint of the input terminal is connected to the midpoint of the second capacitor branch. However, the midpoint of the first capacitor branch is not connected to the midpoint of the second capacitor branch. This allows for separate control of the midpoint voltage of the DC / DC converter circuit and the midpoint voltage of the DC / AC converter circuit, while ensuring the DC bus voltage is supplied. This reduces coupling and prevents mutual influence and interference between the DC / DC converter circuit and the DC / AC converter circuit. The midpoint voltage of the DC / DC converter circuit is stabilized at half the bus voltage, which prevents voltage fluctuations that could affect the circuit and helps reduce the fluctuation of the inductor ripple current in the DC / DC converter circuit.

[0037] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A two-stage multilevel conversion circuit, characterized in that, The system includes a pre-stage circuit and a post-stage circuit, which are connected via a DC bus. The pre-stage circuit includes a DC / DC converter or multiple DC / DC converters with their outputs connected in parallel. The post-stage circuit includes a DC / AC converter or multiple DC / AC converters with their inputs connected in parallel. The DC / DC converter and the DC / AC converter are connected via the DC bus, which includes a positive bus and a negative bus. A first capacitor branch and a second capacitor branch are connected in parallel between the positive bus and the negative bus. The first capacitor branch and the second capacitor branch each include multiple capacitors connected in series in sequence. The midpoint of the output of the DC / DC converter is connected to the midpoint of the first capacitor branch, and the midpoint of the input of the DC / AC converter is connected to the midpoint of the second capacitor branch. The DC / DC converter and the DC / AC converter both employ a multi-level DC / DC converter topology with at least three voltage levels.

2. The two-stage multilevel conversion circuit according to claim 1, characterized in that, The DC / DC converter circuit is a boost circuit, a buck circuit, or a buck-boost circuit.

3. The two-stage multilevel conversion circuit according to claim 1, characterized in that, The DC / AC conversion circuit is a single-phase circuit or a three-phase circuit.

4. The two-stage multilevel conversion circuit according to claim 3, characterized in that, The three-phase circuit is either a three-phase three-wire circuit or a three-phase four-wire circuit.

5. The two-stage multilevel conversion circuit according to claim 1, characterized in that, The DC / DC converter circuit includes at least one inductor, at least two controllable semiconductor switches, and at least two diodes.

6. The two-stage multilevel conversion circuit according to claim 5, characterized in that, The DC / DC converter circuit can be a flying capacitor type BOOST circuit, including a first inductor, a first controllable semiconductor switch, a second controllable semiconductor switch, a first diode, a second diode, a third diode, a fourth diode, and a flying capacitor. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch and the anode of the first diode through the first inductor. The power output terminal of the first controllable semiconductor switch is connected to the power input terminal of the second controllable semiconductor switch and the anode of the third diode. The power output terminal of the second controllable semiconductor switch is connected to the negative terminal of the voltage input and the negative bus. The cathode of the first diode is connected to the anode of the flying capacitor, the cathode of the fourth diode, and the anode of the second diode. The cathode of the flying capacitor is connected to the power output terminal of the first controllable semiconductor switch, the power input terminal of the second controllable semiconductor switch, and the anode of the third diode. The cathode of the third diode is connected to the anode of the fourth diode and the midpoint of the first capacitor branch. The cathode of the second diode is connected to the positive bus.

7. The two-stage multilevel conversion circuit according to claim 5, characterized in that, The DC / DC converter circuit can be a three-level BOOST circuit, including a first inductor, a first controllable semiconductor switch, a second controllable semiconductor switch, a fifth diode, and a sixth diode. The positive terminal of the voltage input is connected to the power input terminal of the first controllable semiconductor switch and the anode of the fifth diode through the first inductor. The cathode of the fifth diode is connected to the positive bus. The power output terminal of the first controllable semiconductor switch is connected to the power input terminal of the second controllable semiconductor switch and the midpoint of the first capacitor branch. The power output terminal of the second controllable semiconductor switch is connected to the negative terminal of the voltage input and the cathode of the sixth diode. The anode of the sixth diode is connected to the negative bus.

8. The two-stage multilevel conversion circuit according to claim 1, characterized in that, The DC / AC conversion circuit includes at least one inductor and at least two controllable semiconductor switches.

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