COMMUTING CELL, FLYING CAPACITOR MODULE AND MULTILEVEL CONVERTER

Description

[0001] The invention relates to a commutation cell, a flying capacitor module with the commutation cell and a multilevel converter with the flying capacitor module.

[0002] Multilevel converters are used particularly in the industrial environment of drive technology but also in the area of ​​energy supply when, in addition to a required high output AC voltage for the converters, a high quality of the sinusoidal output AC voltages is also required with a low expenditure on filters.

[0003] In particular, a modular multilevel converter (MMC) with a flying capacitor (FC) converter structure addresses the limited blocking voltage capability of commercially available semiconductors or power semiconductors, thus enabling their cost-effective use in converters meeting the aforementioned requirements. Semiconductors with a high blocking voltage are known to cause high on-state losses in addition to high procurement costs and potential supply problems, which often makes these semiconductors electrically inefficient to operate.

[0004] The flying capacitor topology therefore has the potential to reduce the total volume of components required for the converter and the filter with respect to the requirements mentioned.

[0005] Commutation capacitors, which are also referred to as decoupling capacitors, can support semiconductors, in particular power semiconductors, in conjunction with a commutation path of a commutation cell, in current commutation, i.e. the current transfer, for example, from an upper semiconductor switch to a lower semiconductor switch of a bridge branch of a bridge circuit in a flying capacitor module of a multilevel converter.

[0006] The commutation or decoupling capacitors are intended to decouple, in particular, high frequency components such as those inherent in flying capacitors, also known as intermediate circuit capacitors.

[0007] High commutation inductances, which are often accepted through a rather generous layout when designing, for example, conductor tracks on a circuit board of the commutation cell or the commutation path, often generate high switching overvoltages on the semiconductors.

[0008] Powerful series resistors at the gate of the semiconductors can limit this switching overvoltage. However, this also increases switching losses, and the advantages offered by fast-switching semiconductors, for example, for use in converters, cannot be fully utilized.

[0009] A low-inductance commutation path for electrically connecting the commutation capacitors to the semiconductors is implemented either laterally on one side of the circuit board, across its surface, or through the circuit board, primarily vertically. The resulting large voltage gaps and the high PCB footprint insufficiently meet the requirements for a low-inductance design of the commutation path or commutation cell.

[0010] The non-patent literature by CHOU DEREK ET AL "An lnterleaved 6-Level GaN Bidirectional Converter for Level II Electric Vehicle Charging", 2019 IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC), IEEE, March 17, 2019, pages 594-600, XP033556088, DOI: 10.1109 / APEC.2019.8721971 discloses the structure and function of an interleaved 6-level GaN bidirectional converter for charging electric vehicles, wherein flying capacitors are used on the DC voltage circuit of the 6-level GaN converter.

[0011] Furthermore, a circuit board design of GaN switching cells of the 6-level GaN converter with an electrical and spatial arrangement of the flying capacitors in conjunction with decoupling capacitors on the DC voltage circuit is shown.

[0012] The non-patent literature by BARTH CHRISTOPHER B ET AL "Design and Control of a GaN-Based, 13-Level, Flying Capacitor Multilevel Inverter", IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS, IEEE, PISCATAWAY, NJ, USA, Vol. 8, No. 3, November 28, 2019, pages 2179-2191, XP011801790, ISSN: 2168-6777, DOI: 10.1109 / JESTPE.2019.2956166 discloses the design and function of a GaN-based 13-level multilevel inverter with flying capacitors on the DC voltage circuit of the multilevel inverter for its use in mobile or stationary systems. Furthermore, a circuit board design shows GaN switching cells with an electrical and spatial arrangement of the flying capacitors and decoupling capacitors.

[0013] Furthermore, a circuit board design of GaN switching cells of the 13-level GaN multilevel inverter with an electrical and spatial arrangement of the flying capacitors in conjunction with decoupling capacitors on the DC voltage circuit of the multilevel inverter is shown.

[0014] The non-patent literature by PALLO NATHAN ET AL "Modular heat sink for chip-scale GaN transistors in multilevel converters", 2018 IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC), IEEE, March 4, 2018, pages 2798-2805, XP033347633, DOI: 10.1109 / APEC.2018.8341414 discloses the structure and function of a modular heat sink for chip-based GaN power semiconductors in multilevel converters.

[0015] Furthermore, a circuit board design of GaN switching cells of the multilevel converter with an electrical and spatial arrangement of flying capacitors on the DC voltage circuit is shown.

[0016] The non-patent literature by MODEER TOMAS ET AL "Design of a GaN-Based lnterleaved Nine-Level Flying Capacitor Multilevel Inverter for Electric Aircraft Applications", IEEE TRANSACTIONS ON POWER ELECTRONICS, INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, USA, Vol. 35, No. 11, April 21, 2020, pages 12153-12165, XP011801421, ISSN: 0885-8993, DOI: 10.1109 / TPEL.2020.2989329 discloses the design and implementation of an interleaved, GaN-based 9-level GaN flying capacitor multilevel inverter.

[0017] Furthermore, a circuit board design of GaN switching cells of the multilevel inverter with an electrical and spatial arrangement of the flying capacitors in conjunction with decoupling capacitors on the DC voltage circuit is shown.

[0018] The invention is based on the object of providing a commutation cell, a flying capacitor module with the commutation cell and a multilevel converter with the flying capacitor module, which reduces the switching losses occurring during commutation processes between semiconductors by means of a low-inductance structure of the commutation cell that is improved compared to the prior art.

[0019] The object is achieved by a commutation cell having the features specified in claim 1, by a flying capacitor module having the features specified in claim 8 and by a multilevel converter having the features specified in claim 10.

[0020] To achieve the object, a commutation cell for a flying capacitor module is proposed, comprising a first semiconductor with a first and second terminal and a second semiconductor with a third and fourth terminal, a first, second, third and fourth capacitor and a printed circuit board, wherein the first semiconductor is connected in a first DC voltage phase and the second semiconductor in a second DC voltage phase, wherein the first and second capacitors are each connected in parallel between the first and third terminals and the third and fourth capacitors are each connected in parallel between the second and fourth terminals, wherein the first and third capacitors are arranged on a first side of the printed circuit board and the second and fourth capacitors are arranged on a second side of the printed circuit board facing away from the first side,wherein the capacitors on the first side are interconnected with the capacitors on the second side by means of vias at the terminals, and wherein a first commutation path is formed on the first side and a second, third and fourth commutation path is formed along the vias and on the first and second side by means of interconnection and arrangement of the capacitors.

[0021] The resulting design of the capacitor pairs of the commutation paths, arranged very closely next to each other or opposite each other, using lateral commutation via the limited areas of the first and second sides of the circuit board, combined with commutation through the circuit board, enables a very advantageous, low-inductance electrical connection of the semiconductors to the capacitors of the commutation path. This design significantly reduces the voltage gap across the semiconductors than across the capacitors.

[0022] In the commutation cell, the first commutation path has the first and third capacitors, the second commutation path has the second and fourth capacitors, the third commutation path has the second and third capacitors, and the fourth commutation path has the first and fourth capacitors as adjacent capacitors for the commutation processes.

[0023] The adjacent capacitors are thus advantageously arranged spatially, generally parallel to one another. This significantly reduces the line resistance of the adjacent capacitors and helps to reduce parasitic inductances.

[0024] In the commutation cell, the capacitors are designed as commutation capacitors.

[0025] Commutation capacitors have a very low inductance, which contributes to an overall reduction of parasitic inductances in the commutation paths.

[0026] Furthermore, commutation capacitors have a high peak current carrying capacity.

[0027] Parasitic commutation inductance and associated switching losses can now be significantly reduced.

[0028] Advantageous embodiments of the commutation cell are specified in the dependent claims.

[0029] In a first advantageous embodiment of the commutation cell, the two semiconductors are arranged on one of the two sides of the circuit board.

[0030] In a further advantageous embodiment of the commutation cell, the first semiconductor is arranged on the first side and the second semiconductor is arranged on the second side of the circuit board.

[0031] Both arrangement options of the semiconductors on one of the two sides of the circuit board offer further advantageous combination options for connecting the semiconductors to the capacitor pairs of the individual commutation paths.

[0032] In a further advantageous embodiment of the commutation cell, the connections of the two semiconductors are formed in several parts.

[0033] The formation of multi-part connections, in particular for the power connections drain and source when using MOSFETs or the power connections collector and emitter when using IGBTs, advantageously enables a low-effort parallel connection of one or more pairs of capacitors.

[0034] In a further advantageous embodiment of the commutation cell, the two semiconductors are GaN semiconductors.

[0035] For example, GaN semiconductor switches can achieve high switching frequencies compared to Si semiconductors. The very low-inductance design supports this feature by eliminating the need for high-power series resistors at the gate of the GaN semiconductors to avoid high switching overvoltages caused by parasitic commutation inductances. High switching overvoltages generally require a reduction in the switching frequency of GaN semiconductors as well.

[0036] In a further advantageous embodiment of the commutation cell, the arrangement of the adjacent capacitors of the commutation paths is designed such that during the commutation processes a current flows through the adjacent capacitors in opposite directions.

[0037] By flowing current in opposite directions to and through adjacent capacitors, coupling inductances or parasitic inductances can be advantageously compensated. Reducing these inductances reduces the switching losses of the semiconductors.

[0038] In a further advantageous embodiment of the commutation cell, first sections of the commutation paths, which are guided along the vias through the circuit board, are arranged substantially orthogonally to second sections of the commutation paths, which are guided along the first or second side of the circuit board.

[0039] The resulting, essentially orthogonal alignment of the vias in relation to the surfaces of the two sides advantageously ensures that the commutation path takes the shortest possible route through the circuit board, so that the affected sections can also be designed with particularly low inductance.

[0040] To achieve the object, a flying capacitor module with a commutation cell according to the invention is further proposed, wherein a first flying capacitor is connected between the first and second DC voltage phases in parallel with the first and second capacitors on an input side of the commutation cell, wherein a second flying capacitor is connected between the first and second DC voltage phases in parallel with the third and fourth capacitors on an output side of the commutation cell, wherein a third and a fourth semiconductor are connected in series between the first and second DC voltage phases in parallel with the second flying capacitor, facing away from the second flying capacitor and the output side of the commutation cell, and wherein a center tap for a first AC voltage phase is formed between the third and fourth semiconductors.

[0041] In an advantageous embodiment of the flying capacitor module, the flying capacitor module has at least one further commutation cell which is designed as a commutation cell, wherein the further commutation cell is connected in parallel to the first flying capacitor and analogously to the commutation cell on the first and second DC voltage phases, wherein the first flying capacitor is arranged between the further commutation cell and the commutation cell and wherein a further flying capacitor is connected in parallel and on the input side to the further commutation cell between the first and second DC voltage phases.

[0042] To achieve the object, a multilevel converter with a flying capacitor module according to the invention is also proposed, wherein the DC voltage phases of the flying capacitor module are connected to a DC voltage intermediate circuit of the multilevel converter, wherein the first AC voltage phase is connectable to an AC voltage line, and wherein the flying capacitor module is connectable to a supply network via the DC voltage intermediate circuit and a supply line and to an energy consumer or an energy generator via the AC voltage line.

[0043] In an advantageous embodiment of the multilevel converter, the multilevel converter has an additional second and third flying capacitor module, each designed as a flying capacitor module, wherein the second and third flying capacitor modules are each connected to the DC intermediate circuit of the multilevel converter via their first and second DC voltage phases, wherein the second flying capacitor module has a second AC voltage phase and the third flying capacitor module has a third AC voltage phase, wherein the second and third AC voltage phases are each connectable to the AC voltage line and wherein the second and third flying capacitor modules are each connectable to the supply network via the DC intermediate circuit and the supply line and to the energy consumer or the energy generator via the AC voltage line.

[0044] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the figures. It shows: FIG 1 a schematic representation of a circuit of a flying capacitor module with a known commutation cell, FIG 2 a first schematic representation of the commutation cell according to FIG 1 with a single commutation path, FIG 3 a second schematic representation of the commutation cell according to FIG 1 with a further individual commutation path, FIG 4 a schematic partial representation of a commutation cell according to the invention, FIG 5 a first supplementary schematic partial representation of the commutation cell according to the invention for FIG 4, FIG 6 a second supplementary schematic partial representation of the commutation cell according to the invention for FIG 4 and FIG 5 , FIG 7 a third supplementary schematic partial representation of the commutation cell according to the invention for FIG 4 and FIG 5 , FIG 8 a schematic representation of a circuit of a flying capacitor module according to the invention with the commutation cell according to the invention according to FIG 4 to FIG 7 and FIG 9 a schematic representation of a multilevel converter according to the invention with a flying capacitor module according to the invention and the commutation cell according to the invention of the flying capacitor module for operating an energy generator or energy consumer by means of the multilevel converter on a supply network.

[0045] The FIG 1shows a schematic representation of a circuit of a flying capacitor module 102 with a known commutation cell 101. This flying capacitor module 102 can generate three voltage levels and is therefore referred to as a 3-level flying capacitor module 102.

[0046] The commutation cell 101 comprises here in the circuit of the FIG 1 a first semiconductor 103 with a first and second terminal 104, 105, and a second semiconductor 106 with a third and fourth terminal 107, 108. Furthermore, the commutation cell 101 in this circuit also has a first and second capacitor 109, 110.

[0047] The first semiconductor 103 is connected in a first DC voltage phase 114 and the second semiconductor 106 is connected in a second DC voltage phase 115.

[0048] The first capacitor 109 is connected between the first and third terminals 104,107 and the second capacitor 110 is connected between the second and fourth terminals 105,108.

[0049] On an input side 128 of the commutation cell 101, and parallel to the first capacitor 109 of the commutation cell 101, a first flying capacitor 126 is connected between the first DC voltage phase 114 and the second DC voltage phase 115.

[0050] On an output side 129 of the commutation cell 101, and parallel to the second capacitor 110 of the commutation cell 101, a second flying capacitor 127 is connected between the first DC voltage phase 114 and the second DC voltage phase 115.

[0051] Parallel to the second flying capacitor 127, facing away from the output side of the commutation cell 101 and the second flying capacitor 127, a third and a fourth semiconductor 130,131 are connected in series between the first and the second DC voltage phase 114,115.

[0052] A center tap 132 for connection to a first AC voltage phase 133 is formed between the third and fourth semiconductors 130, 131.

[0053] With the FIG 2 a first schematic representation of the commutation cell 101 according to FIG 1 with a commutation path 122. The connection of the commutation cell 1 with the FIG 2 shown components, which are arranged here on a first side 116 of a printed circuit board 113, is analogous to the FIG 1 can be found.

[0054] The commutation path 122 is formed laterally along the first side 116 of the circuit board 113 and furthermore shows two opposite directions I 1 , I 2 of a current I flowing along the commutation path 122.

[0055] The FIG 3 discloses a second schematic representation of the commutation cell according to FIG 1 with a further commutation path 123. The connection of the commutation cell 1 with the FIG 3 shown components, which are arranged here on a first and second side 116,117 of a printed circuit board 113, is analogous to the FIG 1 can be found.

[0056] In this exemplary embodiment, the first and second semiconductors 103, 105 and the second capacitor 110 are arranged on the first side 116 of the circuit board 113. The first capacitor 109 is arranged on a second side 117 of the circuit board 113. The components are interconnected via a first and second via 118, 119.

[0057] The commutation path 123 is formed laterally along the first and second sides 116, 117 of the circuit board 113 and orthogonally thereto via the first and second vias 118, 119 and furthermore shows two opposite directions I 1 , I 2 of a current I flowing along the commutation path 123.

[0058] By means of the FIG 4 a schematic partial representation of a commutation cell 1 according to the invention is shown.

[0059] The overall representation of the commutation cell 1 according to the invention includes the Figures 4 to 7. The circuit diagram of the commutation cell 1 to the Figures 4 to 7 can the FIG 8 be taken.

[0060] On the first side 16 of a printed circuit board 13, a first and a second semiconductor 3,6 and a first and a third capacitor 9,11 are arranged and electrically connected.

[0061] The first semiconductor 3 is connected in the first DC voltage phase 14, and the second semiconductor 6 is connected in the second DC voltage phase 15. The first capacitor 9 is connected between the first terminal 4 of the first semiconductor 3 and the third terminal 7 of the second semiconductor 6. The third capacitor 11 is connected between the second terminal 5 of the first semiconductor 3 and the fourth terminal 8 of the second semiconductor 6.

[0062] A first commutation path 24 is in FIG 4with its second sections 43 formed completely laterally along the first side 16 of the printed circuit board 13 and, in the first commutation path 22, furthermore shows two opposite directions I 1 , I 2 of the current I flowing in the capacitors 9, 11.

[0063] A second commutation path 23 is in FIG 4 with its second sections 43 at least partially laterally along the first side 16 of the circuit board 13. Via through-holes 18, 19, 20, 21, the second commutation path 23 is connected to a second side of the circuit board 13 facing away from the first side 16 of the circuit board 13 (in FIG 4 not shown) which is the FIG 5 can be seen.

[0064] The FIG 5 discloses a first supplementary schematic partial representation of the commutation cell 1 according to the invention for FIG 4 .

[0065] Shown in FIG 5the second side 17 of the circuit board 13, which is connected to the FIG 4 shown circuit board 13. The FIG 5 is to be viewed from the same perspective (from above) as the FIG 4 , as if the circuit board 13 were transparent.

[0066] A second capacitor 10 and a fourth capacitor 12 are electrically connected to the components arranged on the first side 16 of the printed circuit board 13 via the vias 18, 19, 20, 21.

[0067] The second and fourth capacitors 10, 12 are connected in parallel between the first DC voltage phase 14 and the second DC voltage phase 15.

[0068] The second commutation path 23 is in FIG 5with its second sections 43 laterally along the second side 17 of the circuit board 13 and furthermore shows in the second commutation path 23 two opposite directions I 1 , I 2 of the current I flowing in the capacitors 10, 12.

[0069] The second commutation path 23 is connected to the first side 16 of the printed circuit board 13 (in FIG 4 ) not shown) which of the FIG 4 can be seen.

[0070] In the Figures 4 and 5 a first and a second section line 44,45 is shown, wherein the first section line 44 is provided with a section view in FIG 6 and the second section line 45 with a sectional view in FIG 7 corresponds.

[0071] With the FIG 6 a second supplementary schematic partial representation of the commutation cell 1 according to the invention is shown for FIG 4 and FIG 5 shown.

[0072] FIG 6corresponds to a sectional view at the first section line 44 from FIG 4 and FIG 5 .

[0073] The electrical connection of the two semiconductors 3 and 6 as well as the two capacitors 10,11 can also be FIG 8 shown circuit.

[0074] Only the second capacitor 10 is arranged on the second side 17 of the circuit board 13.

[0075] You can see in FIG 6 a third commutation path 24, which runs through the vias 19,21, the two semiconductors 3,6 and the second and third capacitors 10,11.

[0076] The third commutation path 24, with its second sections 43, is laterally formed along the first and second sides 16, 17 of the circuit board 13, but with its first sections 42, is also orthogonal by means of the vias 19, 21 through the circuit board 13. Furthermore, the third commutation path 24 exhibits two opposite directions I 1 , I 2 of the current I flowing in the capacitors 10, 11.

[0077] The FIG 7 shows a third supplementary schematic partial representation of the commutation cell according to the invention for FIG 4 and FIG 5 .

[0078] FIG 7 corresponds to a sectional view at the second section line 45 from FIG 4 and FIG 5 .

[0079] The electrical connection of the two semiconductors 3 and 6 as well as the two capacitors 9 and 10 can also be FIG 8 shown circuit.

[0080] You can see in FIG 7a fourth commutation path 25, which runs through the vias 18,20, the two semiconductors 3,6 and the first and fourth capacitors 9,12.

[0081] Only the fourth capacitor 12 is arranged on the second side 17 of the circuit board 13.

[0082] The fourth commutation path 25, with its second sections 43, is laterally formed along the first and second sides 16, 17 of the circuit board 13, but with its first sections 42, is also orthogonal by means of the vias 18, 20 through the circuit board 13. Furthermore, the fourth commutation path 25 exhibits two opposite directions I 1 , I 2 of the current I flowing in the capacitors 9, 12.

[0083] In the FIG 8 is a schematic representation of a circuit of a flying capacitor module 2 according to the invention with the commutation cell 1 according to the invention according to FIG 4 to FIG 7 shown.

[0084] The commutation cell 101 comprises here in the circuit of the FIG 8 a first semiconductor 3 with a first and second terminal 4, 5, and a second semiconductor 6 with a third and fourth terminal 7, 8. Furthermore, the commutation cell 101 in this circuit also has a first, second, third, and fourth capacitor 9, 10, 11, 12.

[0085] The first semiconductor 3 is connected in a first DC voltage phase 14 and the second semiconductor 6 in a second DC voltage phase 15.

[0086] The first and second capacitors 9,10 are connected in parallel between the first and third terminals 4,7 and the third and fourth capacitors 11,12 are connected in parallel between the second and fourth terminals 5,8.

[0087] On an input side 28 of the commutation cell 1, and parallel to the first capacitor 9 of the commutation cell 1, a first flying capacitor 26 is connected between the first DC voltage phase 14 and the second DC voltage phase 15.

[0088] On an output side 29 of the commutation cell 1, and parallel to the fourth capacitor 12 of the commutation cell 1, a second flying capacitor 27 is connected between the first DC voltage phase 14 and the second DC voltage phase 15.

[0089] Parallel to the second flying capacitor 27, facing away from the output side of the commutation cell 1 and the second flying capacitor 27, a third and a fourth semiconductor 30, 31 are connected in series between the first and the second DC voltage phase 14, 15.

[0090] A center tap 32 for connection to a first AC voltage phase 33 is formed between the third and fourth semiconductors 30, 31.

[0091] The FIG 9 discloses a schematic representation of a multilevel converter 35 according to the invention with a flying capacitor module 2 according to the invention and the commutation cell 1 according to the invention of the flying capacitor module 2 for operating an energy consumer 39 or energy generator 40 by means of the multilevel converter 35 on a supply network 38.

[0092] In this exemplary embodiment, the multilevel converter 35 has a flying capacitor module 2 for single-phase operation, wherein the flying capacitor module 2 has at least one commutation cell 1, such as is required for 3-level operation, for example. The commutation cell 1 is connected to the DC intermediate circuit 36 ​​on or in the flying capacitor module 2 via the first and second DC voltage phases 14, 15.

[0093] Whether a DC voltage is provided from the supply network 38 via the supply line 41 to the multilevel converter 35 and thus also to the flying capacitor module 2, which can ideally be fed into the DC link 35 without conversion, or whether the electrical energy must first be converted from an AC voltage from the supply network 38 into a DC voltage for the DC link, remains open here. Both are possible.

[0094] Via an AC voltage phase 33 of the flying capacitor module 2, which has the commutation cell 1, the energy consumer 39 or the energy generator 40 can be operated on the supply network 38 by means of the AC voltage line 37 connected to the multilevel converter 35 and the flying capacitor module 2.

Claims

1. Commutation cell (1) for a flying capacitor module (2), having - a first semiconductor (3) with a first and second terminal (4,5) and a second semiconductor (6) with a third and fourth terminal (7,8), - a first, second, third and fourth capacitor (9,10,11,12) and - a circuit board (13), wherein - the first semiconductor (3) is connected in a first d.c. voltage phase (14) and the second semiconductor (6) is connected in a second d.c. voltage phase (15), - the first and the second capacitor (9,10) are each connected in parallel with one another between the first and third terminal (4,7) and the third and the fourth capacitor (11,12) are each connected in parallel with one another between the second and fourth terminal (5,8), - the second and fourth capacitors (10,12) are arranged on a first side (16) of the circuit board (13) of the first and third capacitor (9,11) and on a second side (17) of the circuit board (13) facing away from the first side (16), - the capacitors (9,11) on the first side (16) are connected to the capacitors (10,12) on the second side (17) by means of vias (18,19,20,21) at the terminals (4,5,7,8), - by means of connection and arrangement of the capacitors (9,10,11,12) a first commutation path (22) is formed on the first side (16) and a second, third and fourth commutation path (23,24,25) are formed along the vias (18,19,20,21) and on the first and second side (16,17), - the first commutation path (22) has the first and third capacitor (9,11), the second commutation path (23) has the second and the fourth capacitor (10,12), the third commutation path (24) has the second and the third capacitor (10,11) and the fourth commutation path (25) has the first and the fourth capacitor (9,12) as respectively adjacent capacitors for the commutation operations, - the capacitors (9,10,11,12) in the commutation paths (22,23,24,25) are formed as commutation capacitors, - the commutation capacitors have a very low inductance for an overall reduction in the parasitic inductances and - the commutation cell (1) is embodied such that - a first flying capacitor (26) is connected between the first and the second d.c. voltage phase (14,15) in parallel with the first and second capacitor (9,10) on an input side (28) of the commutation cell (1) and - a second flying capacitor (27) is connected between the first and the second d.c. voltage circuit (14,15) in parallel with the third and fourth capacitor (11,12) on an output side (29) of the commutation cell (1).

2. Commutation cell (1) according to claim 1, wherein both semiconductors (3,6) are arranged on one of the two sides (16,17) of the circuit board (13).

3. Commutation cell (1) according to claim 1, wherein the first semiconductor (3) is arranged on the first side (16) of the circuit board (13) and the second semiconductor (6) is arranged on the second side (17) of the circuit board (13).

4. Commutation cell (1) according to one of the preceding claims, wherein the terminals (4,5,7,8) of both the semiconductors (3,6) are formed in multiple parts.

5. Commutation cell (1) according to one of the preceding claims, wherein both the semiconductors (3,6) are GaN semiconductors.

6. Commutation cell (1) according to one of the preceding claims, wherein the arrangement of the respectively adjacent capacitors of the commutation paths (22,23,24,25) is formed such that during the commutation operations a current (I) flows through the adjacent capacitors in opposing directions (I1,I2).

7. Commutation cell (1) according to one of the preceding claims, wherein first sections (42) of the commutation paths (23,24,25) which are routed along the vias (18,19,20,21) through the circuit board (13) are arranged orthogonally to second sections (43) of the commutation paths (22,23,24,25) which are routed along the first or second side (16,17) of the circuit board (13).

8. Flying capacitor module (2) with a commutation cell (1) according to one of claims 1 to 7, wherein - a first flying capacitor (26) is connected between the first and the second d.c. voltage phase (14,15) in parallel with the first and second capacitor (9,10) at an input side (28) of the commutation cell (1), - a second flying capacitor (27) is connected between the first and the second d.c. voltage phase (14,15) in parallel with the third and fourth capacitor (11,12) at an output side (29) of the commutation cell (1), - a third and a fourth semiconductor (30,31) are connected in series in parallel with the second flying capacitor (27), facing away from the second flying capacitor (27) and the output side (29) of the commutation cell (1), between the first and the second d.c. voltage phase (14,15) and - a centre tap (32) for a first a.c. voltage phase (33) is formed between the third and fourth semiconductor (30,31).

9. Flying capacitor module (2) according to claim 8, with at least one further commutation cell, which is formed as a commutation cell (1), wherein - the further commutation cell is connected in parallel with the first flying capacitor (26) and analogously to the commutation cell (1) at the first and the second d.c. voltage phase (14,15), - the first flying capacitor (26) is arranged between the further commutation cell and the commutation cell (1) and - a further flying capacitor is connected in parallel with and on the input side to the further commutation cell between the first and the second d.c. voltage phase (14,15).

10. Multilevel converter (35) with a flying capacitor module (2) according to one of claims 8 or 9, wherein the d.c. voltage phases (14,15) of the flying capacitor module (2) are connected to a d.c. voltage intermediate circuit (36) of the multilevel converter (35), wherein the first a.c. voltage phase (33) can be connected to an a.c. voltage line (37) and wherein the flying capacitor module (2) can be connected to a supply grid (38) by way of the d.c. voltage intermediate circuit (36) and a supply line (41) and can be connected to an energy consumer (39) or an energy generator (40) by way of the a.c. voltage line (37).

11. Multilevel converter (35) according to claim 10 with an additional second and third flying capacitor module respectively formed as a flying capacitor module (2), wherein - the second and third flying capacitor module are each connected to the d.c. voltage intermediate circuit (36) of the multilevel converter (35) by way of their first and second d.c. voltage phase, - the second flying capacitor module has a second a.c. voltage phase and the third flying capacitor module has a third a.c. voltage phase, - the second and third a.c. voltage phase can each be connected to the a.c. voltage line (37) and - the second and third flying capacitor module can each be connected to the supply grid (38) by way of the d.c. voltage intermediate circuit (36) and the supply line (41) and to the energy consumer (39) or the energy generator (40) by way of the a.c. voltage line (37).