Cell assembly and converter comprising a plurality of arms each having such a cell assembly

Abstract

The present invention relates to a cell assembly comprising a plurality of cells 9, each of which includes a first terminal 15, a second terminal 17, a plurality of switching elements 19, and a capacitance 21. The plurality of switching elements 19 are adapted to connect the capacitance 21 to the first terminal 15 and the second terminal 17 and to bypass the capacitance 21. Each cell 9 includes a bypass unit 27, which is connected to the first terminal 15 and the second terminal 17 and is adapted to bypass at least one switching element 19 in a short-circuit configuration and not to bypass the at least one switching element 19 in an open-circuit configuration. Each cell 9 includes a cell control unit 29, which is adapted to provide control signals to the plurality of switching elements 19 so that the plurality of switching elements 19 connect the capacitance 21 to the first terminal 15 and the second terminal 17 or so that the plurality of switching elements 19 bypass the capacitance 21. The cell control unit 29 is adapted to supply a control signal to the cell control unit 29 of at least one of the adjacent cells 9 so that the bypass unit 27 changes its configuration from a short circuit configuration to an open circuit configuration or from an open circuit configuration to a short circuit configuration. Furthermore, the present invention relates to a converter 1 consisting of a plurality of arms 3, each arm 5 having such a cell assembly 5.

Description

[Technical Field]

[0001] The present invention relates to a cell assembly and a converter consisting of a number of arms each having such a cell assembly.

[0002] Converters consisting of multiple arms, each having a cell assembly, are known. [Background technology]

[0003] Power transmission systems use converters, also known as power converters. The converters often include multiple arms, also known as phase arms. Each arm includes a cell assembly, and each cell assembly includes multiple cells. Each cell includes a first terminal, a second terminal, multiple switching elements, and a capacitance. The switching elements are adapted to connect the capacitance to the first terminal and the second terminal and bypass the capacitance so that a voltage provided by the capacitance can be selectively supplied by the first terminal and the second terminal. The multiple cells are connected in series such that, for each pair of adjacent cells, the first terminal of a first cell in the pair is connected to the second terminal of a second cell in the pair.

[0004] Although the cells of the cell assemblies known from the prior art are generally robust in design, at least partial failure of one cell, ie single cell failure, is possible.

[0005] Generally, multiple cells can be adapted to ensure converter availability in a specific failure mode, such that when a specific switching element fails, the cell is bypassed because the failed switching element shorts out the cell. In this invention, a failure mode is a mode in which a cell is tempting to fail and a cell may fail. However, a cell is bypassed only when the switching element fails. However, it is not possible to reliably bypass a cell in different cell failure modes. Furthermore, multiple switching elements that fail to provide a bypass when a failed switching element does so are often inefficient and expensive, especially due to high switching losses. Particularly in high-voltage applications where multiple switching elements perform multiple switching operations, switching losses must be kept to a minimum.

[0006] In a further attempt to ensure converter availability in the event of a cell failure, each cell may have a bypass unit adapted to continue operating in a multiple cell failure mode, ensuring that a cell can be bypassed without causing the converter to fail. In many cases, each cell has a cell control unit adapted to provide control signals to the switching elements of that cell and to the bypass unit of that cell. Furthermore, the converter has a main control unit adapted to provide control signals to multiple cell control units of multiple cells. If a cell control unit fails or if the cell failure is severe, such that communication between the cell control unit and the bypass unit of a cell or between the main control unit of the converter and the cell control unit is impaired or no longer possible, control signals can no longer be provided—or at least reliably provided—by the cell control unit to the bypass unit of that cell and / or can no longer be provided—or at least reliably provided—by the main control unit of the converter to the cell control unit. In such cases, the controllability of the cell, and in particular the bypass part of the cell, and the reliable functioning of the converter are therefore impaired, which is particularly disadvantageous when a cell fails during start-up of the converter.

[0007] Generally, a converter that functions reliably is desirable. Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the reliable functioning of converters. [Means for solving the problem]

[0009] According to a first aspect of the invention, this problem is solved by a cell assembly having the features of claim 1.

[0010] The cell assembly comprises a plurality of cells, each of which includes a first terminal, a second terminal, a plurality of switching elements, and a capacitance. The plurality of switching elements are adapted to connect the capacitance to the first terminal and the second terminal and to bypass the capacitance. For each pair of adjacent cells, a plurality of cells of the plurality of cells are connected in series such that the first terminal of a first cell of the pair of adjacent cells is connected to the second terminal of a second cell of the pair of adjacent cells. Each cell further comprises a bypass unit. The bypass unit of each cell is connected to the first terminal and the second terminal of the cell and is adapted to bypass at least one switching element of the plurality of switching elements of the cell in a short-circuit configuration and not bypass the at least one switching element in an open-circuit configuration. Each cell further comprises a cell control unit. The cell controller of each cell is adapted to supply a control signal to the switching elements of the cell, so that the switching elements connect the capacitance to the first terminal and the second terminal or so that the switching elements bypass the capacitance, and the cell controller of each cell is further adapted to supply a control signal to the bypass unit of at least one of the adjacent cells, so that each bypass unit changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration.

[0011] The cell assembly comprises a plurality of cells. Each cell may have a half-bridge circuit configuration. When a cell has a half-bridge circuit configuration, the cell can block voltage in one direction. In particular, when a cell has a half-bridge circuit configuration, the cell forms a two-level converter cell in which the capacitance is connected to a first terminal and a second terminal, and the voltage of the capacitance is supplied to the first terminal and the second terminal through the connection, or the capacitance is bypassed, and the voltage of the capacitance is not supplied to the first terminal and the second terminal through the bypass. The half-bridge circuit configuration is particularly useful when the number of switching elements and switching losses occurring during the switching operation of the switching elements must be kept low. Furthermore, each cell may have a full-bridge circuit configuration. When a cell has a full-bridge circuit configuration, the cell can block voltage in two directions. In particular, when one cell has a full-bridge circuit configuration, the cell forms a three-level converter cell in which the capacitance is connected to the first terminal and the second terminal with both polarities, thereby supplying the voltage of the capacitance to the first terminal and the second terminal with both polarities, or the capacitance is bypassed, thereby not supplying the voltage of the capacitance to the first terminal and the second terminal with both polarities. The full-bridge circuit configuration is particularly useful when the capacitance must be connected to the first terminal and the second terminal with both polarities. Connecting the capacitance to the first terminal and the second terminal with both polarities improves the controllability of the converter according to the second aspect of the present invention.

[0012] Each cell of the plurality of cells has a first terminal and a second terminal. The first terminal and the second terminal are each adapted to be connected to a terminal of an adjacent cell so that the plurality of cells can be connected in series. Furthermore, each cell has a plurality of switching elements. Preferably, each switching element of the plurality of switching elements is adapted to assume a closed circuit configuration in which an operating current can be passed through the switching element and an open circuit configuration in which the operating current cannot be passed through the switching element. Furthermore, each switching element is adapted to switch between the closed circuit configuration and the open circuit configuration during a switching operation, i.e., to switch from the closed circuit configuration to the open circuit configuration and vice versa. Furthermore, each cell of the plurality of cells has a capacitance. Preferably, the capacitance of each cell of the plurality of cells is provided by a capacitor or a plurality of capacitors.

[0013] The plurality of switching elements are adapted to connect the capacitance to the first terminal and the second terminal and to bypass the capacitance. Preferably, the plurality of switching elements are adapted such that a voltage of the capacitance is alternately supplied to the first terminal and the second terminal and not supplied to the first terminal and the second terminal, so that the plurality of switching elements can alternately connect the capacitance to the first terminal and the second terminal and bypass the capacitance by performing switching operations of the plurality of switching elements.

[0014] A plurality of the cells are connected in series such that, for each pair of adjacent cells, the first terminal of a first cell of the pair of adjacent cells is connected to the second terminal of a second cell of the pair of adjacent cells. The series connection of the cells allows coordinated switching action of the switching elements to selectively connect capacitances of the cells to the first and second terminals of the cells. This connection allows for the provision of a stepped waveform that closely approximates a sinusoidal waveform with minimal harmonic distortion at each arm of the converter, i.e., at each AC terminal of the converter.

[0015] Each cell further includes a bypass unit. The bypass unit of each cell is connected to the first and second terminals of the cell and is adapted to bypass at least one of the cell's switching elements in a short-circuit configuration and not bypass the at least one switching element in an open-circuit configuration. Depending on the cell configuration, such as a half-bridge or full-bridge configuration, the bypass unit may be adapted to bypass one switching element or multiple switching elements. In one embodiment of a cell assembly in which a cell has a half-bridge configuration, the bypass unit may be adapted to bypass one switching element. Furthermore, in one embodiment of a cell assembly in which a cell has a full-bridge configuration, the bypass unit may be adapted to bypass two switching elements. Thus, the bypass unit may be adapted to selectively bypass at least one switching element, thereby bypassing the cell in the event of a cell failure. Note that in this paragraph, the terminology used with respect to bypassing at least one switching element refers to the bypass unit being connected to the first and second terminals. Therefore, when the bypass unit is in a short-circuit configuration, the bypass unit directly connects the first terminal and the second terminal to each other in a manner substantially similar to a short circuit. When one switching element is connected to the first terminal and the second terminal, the bypass unit is considered to be adapted to this switching element. When two switching elements are connected to the first terminal and the second terminal, for example, in series with each other, the bypass unit is considered to be adapted to bypass the two switching elements. Thus, the bypass unit provides a means for bypassing the cell when the bypass unit is in a short-circuit configuration. In the present invention, when it is said that the bypass unit bypasses the cell, it mainly means that the bypass unit is in a short-circuit configuration. That is, the direct connection between the first terminal and the second terminal is provided by the bypass unit in a manner substantially similar to a short circuit.

[0016] Each cell further includes a cell controller adapted to supply control signals to the switching elements of the cell such that the switching elements connect the capacitance to the first and second terminals or bypass the capacitance, and the cell controller adapted to supply control signals to the switching elements of the cell such that the voltage of the capacitance can be selectively supplied to the first and second terminals but cannot be supplied to the first and second terminals in the control mode.

[0017] The cell controller of each cell is adapted to supply a control signal to the bypass section of at least one of the adjacent cells. Since the cell controller of each cell is adapted to supply a control signal to the bypass section of at least one of the adjacent cells, the cell controller of each cell can control the bypass section of at least one of the adjacent cells. Preferably, the cell controller of each cell is adapted to supply a control signal to the bypass section of at least one of the adjacent cells. Furthermore, it is particularly preferred that the cell controller of each cell is adapted to supply a control signal to two of the adjacent cells. The cell controller of each cell is adapted to supply a control signal to the cell controller of at least one of the adjacent cells so that each bypass section changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. The cell controller of each cell is adapted to provide a control signal to the cell controller of at least one of its neighboring cells so that each bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration, thereby allowing the cell controller of each cell to control the bypass unit of at least one of its neighboring cells. For example, if a cell controller fails or if the failure of a cell is serious enough that communication between the cell controller and the bypass unit of that cell or between the converter's main control unit and the cell controller is impaired or no longer possible, a control signal can be provided to the bypass unit of the failed cell by the cell controller of a cell adjacent to the failed cell. This further improves the availability of the failed cell, particularly the bypass unit of the failed cell, and thus the reliable functioning of the converter. This is particularly beneficial when a cell fails during converter startup.

[0018] Preferably, the bypass unit may include at least one thyristor. When the bypass unit consists of at least one thyristor, it is particularly preferred that the cell control unit of each cell is adapted to supply control signals to two of the adjacent cells. At least one thyristor of the cell control unit of each cell may be adapted to supply a control signal to the cell control unit of at least one of the adjacent cells so that each bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. In particular, when the cell control unit of each cell is adapted to supply a control signal to the at least one thyristor of the bypass unit, the configuration of the at least one thyristor may be changed from a short-circuit configuration of the at least one thyristor to an open-circuit configuration of the at least one thyristor, or from an open-circuit configuration of the at least one thyristor to a short-circuit configuration of the at least one thyristor, based on a control signal received by the at least one thyristor from the cell control unit.

[0019] In particular, because the bypass section of one cell can be controlled by a cell controller of an adjacent cell, the reliability of the converter is improved. Furthermore, problems that occur during converter startup when a cell is faulty or communication with a cell is impossible are significantly reduced. This also improves converter reliability. Furthermore, because the bypass section of one cell can be controlled by a cell controller of an adjacent cell, the configuration of the bypass section can be changed by the cell controller of the adjacent cell during converter startup. This also enables testing of multiple cells during converter startup. Testing multiple cells during startup allows for the identification and disabling of failed cells so that the failed cells can be disabled during converter operation, for example, allowing the failed cells to be bypassed during startup.

[0020] In summary, the reliable functioning of the converter is further improved.

[0021] Preferably, the cell controller of each cell is adapted to supply a control signal to the bypass unit of that cell, so that the bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. When the cell controller of each cell is adapted to supply a control signal to the bypass unit of that cell, so that the bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration, the configuration of the bypass unit of that cell can be changed by the cell controller of the same cell.

[0022] According to a preferred embodiment of the cell assembly, each cell further comprises a power supply. In this case, the power supply of each cell is adapted to supply power to the bypass section of at least one of the adjacent cells. Since the power supply of each cell is adapted to supply power to the bypass section of at least one of the adjacent cells, the power supply of the bypass section of at least one of the adjacent cells is ensured even if the power supply of at least one of the adjacent cells is not possible in the event of a failure of one cell. Preferably, each power supply is adapted to supply power to the bypass section of the cell. Furthermore, it is preferable that each power supply is adapted to supply power to the control section of the cell. In particular, each power supply is adapted to supply power to the capacitance of the cell.

[0023] According to a preferred embodiment of the cell assembly, the bypass unit of each cell has a memory unit. Preferably, the memory unit is adapted to store information about the configuration of the bypass unit, such as state information of the bypass unit, so that the configuration of the bypass unit can be inferred, for example, by accessing the memory unit from the cell control unit of the cell, from a cell control unit of an adjacent cell, or from the main control unit of the converter. Preferably, the memory unit is adapted to provide information about the configuration of the bypass unit even after power has not been supplied to the bypass unit of the cell by the power supply unit of the cell for a certain period of time. Thus, the memory unit makes it possible to infer the configuration of the bypass unit before the period in which power was not supplied to the bypass unit of the cell by the power supply unit of the cell. Moreover, after this period, the bypass unit can be restored to or maintained in the configuration of the bypass unit before the period. In a particularly preferred embodiment of the cell assembly, the memory unit of the bypass unit of each cell may store its configuration from before the period so that the bypass unit maintains its configuration from before the period during and after the period. This can be achieved, for example, if the memory portion comprises a latching relay, as will be explained further below.

[0024] According to a preferred embodiment of the cell assembly, the memory unit of each cell is connected to the cell controller of the cell such that state information of the bypass unit, indicating a configuration of the bypass unit, can be written to the memory unit by the cell controller of the cell. A control signal received by the bypass unit of a cell from the cell controller may indicate state information that can be written to the memory unit by the cell controller of the cell. The state information may indicate a configuration of the bypass unit, in particular a current configuration of the bypass unit and / or a desired configuration of the bypass unit. When the state information indicates a configuration of the bypass unit, the state information may be referred to as state information of the bypass unit. Preferably, the current configuration of the bypass unit is a configuration in which the bypass unit currently exists. Similarly, the desired configuration of the bypass unit is preferably a configuration required by the bypass unit, in which at least one switching element of the plurality of switching elements is bypassed or not bypassed depending on its status.

[0025] According to a preferred embodiment of the cell assembly, the memory unit comprises a data storage unit, preferably adapted to store digital data, in particular status information of the bypass unit.

[0026] According to a preferred embodiment of the cell assembly, the data store is a non-volatile data store, which is particularly desirable if the bypass state information must be restored each time the memory portion of the cell is periodically powered up.

[0027] According to a preferred embodiment of the cell assembly, the memory unit comprises a latching relay. A latching relay is particularly useful if the memory unit of each cell's bypass unit can store the configuration of the bypass unit of the cell from a previous period, so that during and after a period when power is not supplied to the bypass unit of the cell by the power supply unit of the cell, the bypass unit maintains its configuration from the previous period. The latching relay may have multiple input terminals for receiving control signals from the cell controller, and normally open contact terminals adapted to an open configuration and a closed configuration, so that the configuration of a thyristor can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration, and change from the open configuration to the closed configuration and from the closed configuration to the open configuration depending on the control signal received from the cell controller.

[0028] According to a preferred embodiment of the cell assembly, the cell controller of each cell is adapted to supply a control signal to the bypass unit of one of the adjacent cells, so that each bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Since the cell controller of each cell is adapted to supply a control signal to the bypass unit of one of the adjacent cells, so that each bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration, the cell controller of each cell can control the bypass unit of one of its adjacent cells. It is particularly advantageous that a control signal is supplied from the cell controller of each cell to its bypass unit, and that a further control signal is supplied from the cell controller of an adjacent cell to its bypass unit. Thus, if the cell controller of a cell fails or if communication between the cell controller of this cell and the bypass unit or between the main control of the converter and the cell controller of this cell is impaired or no longer possible, a control signal can be supplied to the bypass unit of this failed cell by the cell controller of a cell adjacent to the failed cell. Advantageously, the power supply of each cell is adapted to supply power to the bypass unit of one of the neighboring cells when the cell controller of each cell is adapted to supply a control signal to the bypass unit of one of the neighboring cells so that the respective bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration.

[0029] According to a preferred embodiment of the cell assembly, the cell controller of each cell is adapted to supply control signals to the bypass sections of two adjacent cells, so that each bypass section changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Since the cell controller of each cell is adapted to supply control signals to the bypass sections of two adjacent cells, so that each bypass section changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration, the cell controller of each cell can control the bypass sections of two adjacent cells of that cell. It is particularly advantageous that a control signal is supplied from the cell controller of each cell to the bypass section of that cell, and further control signals are supplied from the cell controllers of two adjacent cells to the bypass sections of that cell. Thus, if the cell controller of a cell fails or if communication between the cell controller of this cell and the bypass unit or between the main control device of the converter and the cell controller of this cell is impaired or no longer possible, control signals can be supplied to the bypass units of this failed cell by the cell controllers of the two cells adjacent to the failed cell. Advantageously, the power supply of each cell is adapted to supply power to the bypass units of two of the neighboring cells, when the cell controller of each cell is adapted to supply a control signal to the bypass unit of one of the neighboring cells, so that the respective bypass unit changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration.

[0030] According to a preferred embodiment of the cell assembly, the bypass unit of each cell is adapted to bypass one of the switching elements of the cell in a short-circuit configuration and not to bypass the one switching element in an open-circuit configuration. Advantageously, if the cell has a half-bridge circuit configuration, the bypass unit of each cell is adapted to bypass one of the switching elements of the cell in a short-circuit configuration and not to bypass the one switching element in an open-circuit configuration.

[0031] According to a preferred embodiment of the cell assembly, the bypass unit of each cell is adapted to bypass two switching elements of the plurality of switching elements of the cell in a short-circuit configuration and not to bypass the two switching elements in an open-circuit configuration. Advantageously, when the cells have a full-bridge topology, the bypass unit of each cell is adapted to bypass two switching elements of the plurality of switching elements of the cell in a short-circuit configuration and not to bypass the two switching elements in an open-circuit configuration.

[0032] According to a preferred embodiment of the cell assembly, the plurality of switching elements of each cell comprises two switching elements connected to each other at a first connection point connected to the first terminal of the cell. In this case, a first switching element of the two switching elements is connected to a first terminal of a capacitance, and a second switching element of the two switching elements is connected to a second terminal of the capacitance at a second connection point connected to the second terminal of the cell. When the plurality of switching elements of each cell comprises two switching elements connected to each other at a first connection point connected to the first terminal of the cell, a half-bridge circuit configuration of the cells can be provided. In this case, a first switching element of the two switching elements is connected to the first terminal of a capacitance, and a second switching element of the two switching elements is connected to the second terminal of the capacitance at a second connection point connected to the second terminal of the cell.

[0033] According to a preferred embodiment of the cell assembly, the plurality of switching elements of each cell consists of four switching elements. In this case, a first switching element of the four switching elements and a second switching element of the four switching elements are connected to each other at a first connection point connected to the first terminal of the cell. In this case, a third switching element of the four switching elements and a fourth switching element of the four switching elements are connected to each other at a second connection point connected to the second terminal of the cell. In this case, the first switching element and the third switching element are connected to each other at a third connection point connected to the first terminal of the capacitance of the cell, and the second switching element and the fourth switching element are connected to each other at a fourth connection point connected to the second terminal of the capacitance of the cell. When the plurality of switching elements of each cell consists of four switching elements, a full-bridge circuit configuration can be provided. In this case, a first switching element of the four switching elements and a second switching element of the four switching elements are connected to each other at a first connection point connected to the first terminal of the cell. In this case, a third switching element of the four switching elements and a fourth switching element of the four switching elements are connected to a second connection point connected to the second terminal of the cell, the first switching element and the third switching element are connected to a third connection point connected to the first terminal of the capacitance of the cell, and the second switching element and the fourth switching element are connected to a fourth connection point connected to the second terminal of the capacitance of the cell.

[0034] According to a preferred embodiment of the cell assembly, each of the at least one switching element of each cell comprises a transistor. Furthermore, each of the at least one switching element of each cell may comprise an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a high electron mobility transistor (HEMT) and / or a thyristor. Preferably, each of the at least one switching element of each cell comprises silicon (Si), silicon carbide (SiC) and / or gallium arsenide (GAN).

[0035] According to a second aspect of the invention, the problem is also solved by a converter having the features of claim 15. The converter comprises a plurality of arms, each arm comprising a cell assembly according to the first aspect of the invention.

[0036] The converter comprises a plurality of arms. Preferably, the converter comprises three arms. However, it is also advantageous for the converter to comprise six arms. In any case, the number of arms of the converter can be selected depending on the application of the converter. Furthermore, the converter can have one arm per phase of the converter. Alternatively, the converter can have two or more arms per phase of the converter. Preferably, a predetermined number of arms, i.e., one arm or two or more arms, can be selected per phase depending on the application of the converter. Each arm of the plurality of arms comprises a cell assembly according to the first aspect of the present invention.

[0037] Preferably, the converter according to the second aspect of the invention is a multilevel converter, preferably a modular multilevel converter (MMC). It is particularly preferred that the converter is a three-phase modular multilevel converter. Preferably, the converter according to the second aspect of the invention is adapted to convert power from high voltage AC power to high voltage DC power. Advantageously, the converter according to the second aspect of the invention is further adapted to convert power from high voltage DC power to high voltage AC power. Furthermore, the converter according to the second aspect of the invention may be adapted to convert power from high voltage AC power to high voltage DC power, and from high voltage DC power to high voltage AC power. When the converter is adapted to convert power from high voltage DC power to high voltage AC power, or from high voltage AC power to high voltage DC power, or from high voltage AC power to high voltage DC power, or from high voltage DC power to high voltage AC power, the converter may be referred to as a high voltage direct current (HVDC) converter. In particular, in embodiments in which each switching element of at least one switching element of each cell comprises one transistor, the converter according to the second aspect of the invention may be referred to as a voltage source converter (VSC). Advantageously, the converter according to the second aspect of the invention is adapted for use in medium voltage (MV) drives. In particularly preferred embodiments of the converter according to the second aspect of the invention, the converter constitutes a static var compensator (STATCOM) converter. When the converter constitutes a static var compensator converter, it is particularly advantageous for the static var compensator to form part of a total power flow controller (UPFC). In preferred embodiments, the converter is a single-phase modular multilevel converter. In further preferred embodiments, the converter is a matrix converter.

[0038] The features, technical effects and / or advantages described with respect to the first aspect of the present invention apply at least equally to the second aspect of the present invention, and therefore will not be repeated here. Although method steps are described in a particular order, the present invention is not limited to this order. Rather, the individual method steps may be performed in any effective order.

[0039] Further features, advantages and application possibilities of the present invention are explained below on the basis of exemplary embodiments and / or drawings. Therefore, all the individual features and / or any combination of features described and / or shown may constitute beneficial objects and / or features of the present invention, regardless of the individual claim combinations or these claims. Furthermore, in the drawings, the same reference numerals may indicate the same or similar objects. [Brief explanation of the drawings]

[0040] [Figure 1] 1 shows a schematic representation of a part of a first embodiment of a converter consisting of multiple arms. [Figure 2] 2 shows a first embodiment of a cell of a cell assembly of one arm of the converter, a portion of which is shown in FIG. 1; [Figure 3] 2 shows a schematic diagram of a second embodiment of a cell of a cell assembly of one arm of the converter, a portion of which is shown in FIG. 1; [Figure 4] 2 shows a schematic diagram of a third embodiment of a cell of a cell assembly of one arm of the converter, a portion of which is shown in FIG. 1; [Figure 5] 1 shows a schematic representation of part of a second embodiment of a converter consisting of multiple arms;

[0041] [Figure 6] 10 shows a schematic representation of part of a third embodiment of a converter consisting of multiple arms; [Figure 7]6 shows a schematic diagram of a fourth embodiment of a cell of a cell assembly of one arm of the converter, a portion of which is shown in FIG. 5; [Figure 8] 6 shows a schematic diagram of a fifth embodiment of a cell of a cell assembly of one arm of the converter, a portion of which is shown in FIG. 5; [Figure 9] 6 shows a schematic diagram of a sixth embodiment of a cell of a cell assembly of one arm of the converter, part of which is shown in FIG. 5; [Figure 10] 10A and 10B are schematic diagrams illustrating a part of a first embodiment of a bypass portion of the first to sixth embodiments of the cell shown in FIGS. 2 to 4 and 7 to 9. [Figure 11] 10A and 10B show schematic views of a part of a second embodiment of the bypass section of the first to sixth embodiments of the cell shown in FIGS. 2 to 4 and 7 to 9. [Figure 12] 10A and 10B show schematic views of parts of a third embodiment of the bypass sections of the first to sixth embodiments of the cells shown in FIGS. 2 to 4 and 7 to 9. [Figure 13] 10A and 10B show schematic views of a part of a fourth embodiment of the bypass section of the first to sixth embodiments of the cell shown in FIGS. 2 to 4 and 7 to 9. [Figure 14] 10A and 10B show schematic views of a part of a fifth embodiment of the bypass section of the first to sixth embodiments of the cells shown in FIGS. 2 to 4 and 7 to 9. DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 shows a part of a first embodiment of a converter 1, which is composed of six arms 3. Each arm 3 is composed of one cell assembly 5 and one inductance 7. Each cell assembly 5 is composed of a plurality of cells 9. Each arm 3 is connected to one of two DC (direct current) terminals 11 and one of three AC (alternating current) terminals 13. These arms 3 form three arm pairs. In this case, each arm pair of these arm pairs consists of a first arm 3 and a second arm 3. In this case, the first arm 3 and the second arm 3 are connected to the same AC terminal 13 and different DC terminals 11. Furthermore, each arm pair is connected to one different AC terminal 13.

[0043] Figure 2 shows a first embodiment of a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in Figure 1. The cell 9 has a first terminal 15 and a second terminal 17. The cells 9 of each cell assembly 5 shown in Figure 1 are connected in series such that, for each pair of adjacent cells 9, the first terminal 15 of the first cell 9 of the pair is connected to the second terminal 17 of the second cell 9 of the pair.

[0044] Furthermore, the cell 9 has two switching elements 19 and one capacitance 21. These switching elements 19 are adapted to connect the capacitance 21 to the first terminal 15 and the second terminal 17 and bypass the capacitance 21 so that the voltage Vc provided by the capacitance can be selectively supplied by the first terminal 15 and the second terminal 17 as the cell output voltage Vo. Each switching element 19 shown in FIG. 2 comprises an insulated gate bipolar transistor (IGBT) 23 and a diode 25. The two switching elements 19 are connected to each other at a first connection point, which is connected to the first terminal 15 of the cell 9. The first switching element 19 of the two switching elements 19 is connected to the first terminal of the capacitance 21, and the second switching element 19 of the two switching elements 19 is connected to the second terminal of the capacitance 21 at a second connection point, which is connected to the second terminal 17 of the cell 9.

[0045] The cell 9 further includes a bypass section 27. The bypass section 27 is connected to the first terminal 15 and the second terminal 17. The bypass section 27 can be adapted to a short-circuit configuration and an open-circuit configuration. The bypass section 27 is adapted to switch back and forth between these two configurations. In the short-circuit configuration, the bypass section 27 bypasses the switching element 19 below the two switching elements 19 shown in FIG. 2. In the open-circuit configuration, the bypass section 27 does not bypass the switching element 19 below the two switching elements 19 shown in FIG. 2.

[0046] Furthermore, the cell 9 has a cell control unit 29. The cell control unit 29 of the cell 9 is adapted to supply control signals to the switching elements 19 of the cell 9 such that the switching elements 19 connect the capacitance 21 to the first terminal 15 and the second terminal 17 or such that the switching elements 19 bypass the capacitance 21. Furthermore, the cell control unit 29 of the cell 9 is adapted to supply a control signal to the bypass unit 27 of the cell 9 such that the bypass unit 27 of the cell 9 changes the configuration of the bypass unit 27 from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Furthermore, the cell control unit 29 of the cell 9 is adapted to supply a control signal to the bypass unit 27 of at least one of the adjacent cells 9 such that the bypass unit 27 of each of the adjacent cells 9 changes the configuration of the bypass unit 27 from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. In particular, the cell control unit 29 of each adjacent cell 9 may be adapted to supply a control signal to the bypass unit 27 of at least one of the adjacent cells 9, so that the bypass unit 27 of each adjacent cell 9 changes the configuration of the bypass unit 27 from a short-circuit configuration to an open-circuit configuration, or from an open-circuit configuration to a short-circuit configuration. Furthermore, the cell control unit 29 of each adjacent cell 9 may be adapted to supply control signals to the bypass units 27 of two of the adjacent cells 9, so that the bypass unit 27 of each adjacent cell 9 changes the configuration of the bypass unit 27 from a short-circuit configuration to an open-circuit configuration, or from an open-circuit configuration to a short-circuit configuration.

[0047] The cell 9 further comprises one power supply 31 adapted to supply power to the bypass part 27 of the cell 9, the control part 29 of the cell 9 and the capacitance 21 of the cell 9. Furthermore, the power supply 31 is adapted to supply power to the bypass part 27 of at least one of the adjacent cells 9.

[0048] 3 shows a second embodiment of a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 1. The second embodiment of the cell 9 shown in FIG. 3 is essentially identical to the first embodiment of the cell 9 shown in FIG. 2. However, the bypass section 27 of the second embodiment of the cell 9 comprises two thyristors 33. Both thyristors 33 are connected to the first terminal 15 and the second terminal 17. The anode of the first thyristor 33 is connected to the first terminal 15, and the cathode is connected to the second terminal 17. The cathode of the second thyristor 33 is connected to the first terminal 15, and the anode is connected to the second terminal 17.

[0049] Each of the two thyristors 33 is adapted to bypass the lower switching element 19 of the two switching elements 19 shown in FIG. 3 in a short-circuit configuration and not bypass the lower switching element 19 in an open-circuit configuration. Each of the two thyristors 33 is adapted to switch back and forth between these two configurations. Due to the two thyristors 33, the bypass section 27 is adapted to be in a first short-circuit configuration, a second short-circuit configuration, and an open-circuit configuration. In the first short-circuit configuration of the bypass section 27, the left thyristor 33 in FIG. 3 is in a short-circuit configuration and bypasses the lower switching element 19, and the right thyristor 33 in FIG. 3 is in an open-circuit configuration and does not bypass the lower switching element 19. Furthermore, in the second short-circuit configuration of the bypass unit 27, the right thyristor 33 in FIG. 3 is in a short-circuit configuration and bypasses the lower switching element 19, and the left thyristor 33 in FIG. 3 is in an open-circuit configuration and does not bypass the lower switching element 19. Furthermore, in the open-circuit configuration of the bypass unit 27, both the left thyristor 33 and the right thyristor 33 in FIG. 3 are in an open-circuit configuration and do not bypass the lower switching element 19. Due to the two thyristors 33, the bypass unit 27 can selectively bypass the lower switching element 19 in both directions, i.e., from the first terminal 15 to the second terminal 17 and from the second terminal 17 to the first terminal 15.

[0050] Furthermore, the cell control unit 29 is connected to the gates of the two thyristors 33 and is adapted to supply control signals to the two thyristors 33 so that the configuration of each of the two thyristors 33 can be changed from a short-circuit configuration to an open-circuit configuration and from the open-circuit configuration to a short-circuit configuration. Thus, the configuration of the bypass unit 27 can be changed from the first short-circuit configuration to the second short-circuit configuration, from the second short-circuit configuration to the first short-circuit configuration, from the first short-circuit configuration to the open-circuit configuration, from the open-circuit configuration to the first short-circuit configuration, from the second short-circuit configuration to the open-circuit configuration, and from the open-circuit configuration to the second short-circuit configuration. Thus, the direction in which the bypass unit 27 bypasses the lower switching element 19 can be controlled.

[0051] FIG. 4 shows a third embodiment of a cell 9 of one of the cell groups 5 of one of the arms 3 of the converter 1, part of which is shown in FIG. 1. The third embodiment of the cell 9 shown in FIG. 4 is essentially identical to the first embodiment of the cell 9 shown in FIG. 2. However, the cell 9 has a first terminal 15, a second terminal 17, and a third terminal 35 connected to the first terminal of the capacitance 21. The first terminal 15 and the second terminal 17 are adapted as described above in relation to the other embodiments. For example, the voltage Vc provided by the capacitance can be provided by the first terminal 15 and the second terminal 17 as the cell output voltage Vo. Furthermore, the bypass section 27 of the third embodiment of the cell 9 is composed of three thyristors 33. A first thyristor 33 of the three thyristors 33 is connected to the first terminal 15 of the cell 9 and the second terminal 17 of the cell 9, a second thyristor 33 of the three thyristors 33 is connected to the first terminal 15 of the cell 9 and the third terminal 35 of the cell 9, and a third thyristor 33 of the three thyristors 33 is connected to the second terminal 17 of the cell 9 and the third terminal 35 of the cell 9. The anode of the first thyristor 33 is connected to the second terminal 17 and the cathode is connected to the first terminal 15. The anode of the second thyristor 33 of the three thyristors 33 is connected to the first terminal 15 and the cathode is connected to the third terminal 35. The anode of the third thyristor 33 of the three thyristors 33 is connected to the third terminal 35 and the cathode is connected to the second terminal 17.

[0052] Furthermore, the first thyristor 33 and the second and third thyristors 33 are adapted to bypass the lower switching element 19 of the two switching elements 19 shown in FIG. 4 in a short-circuit configuration and not bypass the lower switching element 19 in an open-circuit configuration. These thyristors 33 are adapted to switch back and forth between these configurations. Due to the three thyristors 33, the bypass section 27 is adapted to be in a first short-circuit configuration, a second short-circuit configuration, and an open-circuit configuration. In the first short-circuit configuration of the bypass section 27, the first thyristor 33 of FIG. 4 is in a short-circuit configuration and bypasses the lower switching element 19, and the second and third thyristors 33 of FIG. 4 are in an open-circuit configuration and do not bypass the lower switching element 19. 4 are in an open-circuit configuration and do not bypass the lower switching element 19. Furthermore, in the open-circuit configuration of the bypass unit 27, the first thyristor 33 and the second and third thyristors 33 are in an open-circuit configuration and do not bypass the lower switching element 19. Due to the three thyristors 33, the bypass unit 27 can selectively bypass the lower switching element 19 in both directions, i.e., from the first terminal 15 to the second terminal 17 and from the second terminal 17 to the first terminal 15.

[0053] Furthermore, the cell control unit 29 is connected to the gates of the three thyristors 33 and is adapted to supply control signals to the three thyristors 33 so that the configuration of each of the three thyristors 33 can be changed from a short-circuit configuration to an open-circuit configuration and from the open-circuit configuration to a short-circuit configuration. Thus, the configuration of the bypass unit 27 can be changed from a first short-circuit configuration to a second short-circuit configuration, from the second short-circuit configuration to the first short-circuit configuration, from the first short-circuit configuration to an open-circuit configuration, from the open-circuit configuration to the first short-circuit configuration, from the second short-circuit configuration to the open-circuit configuration, and from the open-circuit configuration to the second short-circuit configuration. Thus, the direction in which the bypass unit 27 bypasses the lower switching element 19 can be controlled.

[0054] FIG. 5 shows a part of a second embodiment of a converter 1, which is composed of three arms 3. Each arm 3 is composed of one cell assembly 5 and one inductance 7. Each cell assembly 5 is composed of a plurality of cells 9. Each arm 3 is connected to two of three AC terminals 13. These arms 3 form three arm pairs. In this case, each arm pair is composed of one first arm 3 and one second arm 3. In this case, the first arm 3 and the second arm 3 are connected to the same AC terminal 13. Furthermore, each arm pair is connected to a different but identical AC terminal 13.

[0055] FIG. 6 shows part of a third embodiment of the converter 1. This converter consists of three sub-converters 2. Each sub-converter consists of three arms 3. Therefore, this converter 1 can be considered to consist of nine arms 3. Each arm 3 consists of one cell assembly 5 and one inductance 7. Each cell assembly 5 consists of multiple cells 9. Each arm 3 is connected to one of three first AC terminals 13 via one inductance 7 and to one of three second AC terminals 13 via one inductance 7. These arms 3 form three groups of arms. In this case, each group of arms consists of three arms 3 and can be considered to form part of one sub-converter 2 of the three sub-converters 1. The arms 3 of each group of arms are connected to the same AC terminal 13 but to different second AC terminals 13.

[0056] Although the two cells 9 of a cell pair 9 consisting of a first cell 9 of a first cell assembly 5 of a first arm 3 and a second cell 9 of a second cell assembly 5 of a second arm 3 are not connected in series to each other within the same cell assembly 5, the first cell 9 and the second cell 9 may be connected to each other and / or interact with each other in the same way as the cells 9 of a cell pair consisting of adjacent cells 9 are connected to each other and / or interact with each other in accordance with the present invention. For example, the cell control unit 29 of the first cell 9 may be adapted to provide a control signal to the bypass unit 27 of the second cell 9 so that each bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration, or from an open-circuit configuration to a short-circuit configuration. The above embodiment may be applied to each cell pair of cells 9 consisting of multiple cells 9 that do not belong to the same cell assembly 5, and may also be applied to each cell pair of cells 9 consisting of multiple cells 9 that belong to the same cell assembly 5 but are not adjacent cells 9. Furthermore, the above embodiments may be applied to each feature and combination of features, individually, in combination, in relation to two adjacent cells, and particularly to each embodiment of the present invention.

[0057] FIG. 7 illustrates a fourth embodiment of a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 5. The fourth embodiment of the cell 9 illustrated in FIG. 7 may also constitute a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 6. The cell 9 has a first terminal 15 and a second terminal 17. The cells 9 of each cell assembly 5 illustrated in FIGS. 5 and 6 are connected in series such that, for each pair of adjacent cells 9, the first terminal 15 of the first cell 9 of the pair of adjacent cells 9 is connected to the second terminal 17 of the second cell 9 of the pair of adjacent cells 9.

[0058] This cell 9 has four switching elements 19 and one capacitance 21. The switching elements 19 are adapted to connect the capacitance 21 to the first terminal 15 and the second terminal 17 and to bypass the capacitance 21 so that the voltage Vc provided by this capacitance can be selectively supplied by the first terminal 15 and the second terminal 17 as the cell output voltage Vo. Compared to the first embodiment of the cell 9 shown in Fig. 2, the four switching elements 19 are adapted to connect the capacitance 21 to the first terminal 15 and the second terminal 17 so that the voltage provided by this capacitance can be selectively supplied by the first terminal 15 and the second terminal 17 as the cell output voltage Vo, in particular with alternating polarity. For example, Vo can be alternately equal to Vc and -Vc.

[0059] Each switching element 19 shown in FIG. 7 includes one IGBT 23 and one diode 25. A first switching element 19 of the four switching elements 19 and a second switching element 19 of the four switching elements 19 are connected to each other at a first connection point. This first connection point is connected to a first terminal 15 of the cell 9. The first switching element 19 is connected to a first terminal of a capacitance 21, and the second switching element 19 is connected to a second terminal of the capacitance 21. A third switching element 19 of the four switching elements 19 and a fourth switching element 19 of the four switching elements 19 are connected to each other at a second connection point. This second connection point is connected to a second terminal 17 of the cell 9. The third switching element 19 is connected to a first terminal of the capacitance 21, and the fourth switching element 19 is connected to a second terminal of the capacitance 21. The first switching element 19 and the third switching element 19 are connected to each other at a third connection point. The second switching element 19 and the fourth switching element 19 are connected to a fourth connection point which is connected to the second terminal of the capacitance 21 .

[0060] The cell 9 further includes a bypass section 27. The bypass section 27 is connected to the first terminal 15 and the second terminal 17. The bypass section 27 is further adapted to be in a short-circuit configuration and an open-circuit configuration. The bypass section 27 is adapted to switch back and forth between these two configurations. In the short-circuit configuration, the bypass section 27 bypasses the first switching element 19 and the third switching element 19 shown in FIG. 7, as well as the second switching element 19 and the fourth switching element 19. In the open-circuit configuration, the bypass section 27 does not bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19.

[0061] Furthermore, the cell 9 further includes one cell control unit 29. The cell control unit 29 of the cell 9 is adapted to supply signals to the switching elements 19 of the cell 9 so that the switching elements 19 connect the capacitance 21 to the first terminal 15 and the second terminal 17 or so that the switching elements 19 bypass the capacitance 21. Furthermore, the cell control unit 29 of the cell 9 is adapted to supply a control signal to the bypass unit 27 of the cell 9 so that the bypass unit 27 of the cell 9 changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Furthermore, the cell control unit 29 of the cell 9 is adapted to supply a control signal to the bypass unit 27 of at least one of the adjacent cells 9 so that each bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. In particular, the cell control unit 29 of a cell 9 may be adapted to supply a control signal to the bypass unit 27 of at least one cell 9 of adjacent cells 9, such that each bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration, or from an open-circuit configuration to a short-circuit configuration. Furthermore, alternatively, the cell control unit 29 of a cell 9 may be adapted to supply a control signal to the bypass units 27 of two cells 9 of adjacent cells 9, such that each bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration, or from an open-circuit configuration to a short-circuit configuration.

[0062] The cell 9 further comprises one power supply 31. The power supply 31 is adapted to supply power to the bypass part 27 of the cell 9, to the control part 29 of the cell 9 and to the capacitance 21 of the cell 9. Furthermore, the power supply 31 is adapted to supply power to at least one of the adjacent cells 9.

[0063] FIG. 8 shows a fifth embodiment of a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 5 . The fifth embodiment of the cell 9 shown in FIG. 8 can also constitute a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 6 . The fifth embodiment of the cell 9 shown in FIG. 8 is essentially identical to the fourth embodiment of the cell 9 shown in FIG. 7 . However, the bypass section 27 of the fifth embodiment of the cell 9 comprises two thyristors 33. Both thyristors 33 are connected to the first terminal 15 and the second terminal 17. The anode of the first thyristor 33 is connected to the first terminal 15, and the cathode is connected to the second terminal 17. The cathode of the second thyristor 33 is connected to the first terminal 15, and the anode is connected to the second terminal 17.

[0064] Each thyristor 33 is adapted to be in a short-circuit configuration, with one thyristor 33 bypassing the first switching element 19 and the third switching element 19, and similarly bypassing the second switching element 19 and the fourth switching element 19. Additionally, each thyristor 33 is adapted to be in an open-circuit configuration, with one thyristor 33 not bypassing the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19. Each thyristor 33 is adapted to switch back and forth between the short-circuit configuration and the open-circuit configuration.

[0065] The bypass unit 27 is configured to be in a first short-circuit configuration state, a second short-circuit configuration state, and an open-circuit configuration state due to the two thyristors 33. In the first short-circuit configuration of the bypass unit 27, the first thyristor 33 in Fig. 8 is in the short-circuit configuration state and bypasses the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19, and the second thyristor 33 in Fig. 8 is in the open-circuit configuration state and does not bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19. Furthermore, in the second short-circuit configuration of the bypass unit 27, the second thyristor 33 in Fig. 8 is in a short-circuit configuration state and bypasses the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19, and the first thyristor 33 in Fig. 8 is in an open-circuit configuration state and does not bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19. Furthermore, in the open-circuit configuration of the bypass unit 27, both the first thyristor 33 and the second thyristor 33 in Fig. 8 are in an open-circuit configuration state and both thyristors 33 do not bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19. Due to the two thyristors 33, the bypass section 27 can selectively bypass the first switching element 19, the second switching element 19, the third switching element 19 and the fourth switching element 19 in two directions, i.e., from the first terminal 15 to the second terminal 17, and from the second terminal 17 to the first terminal 15.

[0066] 8 , the cell control unit 29 is connected to the gates of the two thyristors 33 and is adapted to supply control signals to the two thyristors 33 so that the configuration of each of the two thyristors 33 can be changed from a short-circuit configuration to an open-circuit configuration and from the open-circuit configuration to the short-circuit configuration. Thus, the configuration of the bypass unit 27 can be changed from the first short-circuit configuration to the second short-circuit configuration, from the second short-circuit configuration to the first short-circuit configuration, from the first short-circuit configuration to the open-circuit configuration, from the open-circuit configuration to the first short-circuit configuration, from the second short-circuit configuration to the open-circuit configuration, and from the open-circuit configuration to the second short-circuit configuration. Thus, the direction in which the bypass unit 27 bypasses the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19 can be controlled.

[0067] FIG. 9 schematically illustrates a sixth embodiment of a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 5 . The fifth embodiment of the cell 9 illustrated in FIG. 9 can also constitute a cell 9 of a cell assembly 5 of one of the arms 3 of the converter 1, a portion of which is shown in FIG. 6 . The sixth embodiment of the cell 9 illustrated in FIG. 9 is essentially identical to the fifth embodiment of the cell 9 illustrated in FIG. 8 . However, the bypass section 27 of the sixth embodiment of the cell 9 comprises one thyristor 33 and four diodes 25. A first diode 25 of the four diodes 25 and a second diode 25 of the four diodes 25 are connected to the first terminal 15 and are connected to the thyristor 33 on the other side. A third diode 25 of the four diodes 25 and a fourth diode 25 of the four diodes 25 are connected to the second terminal 17 and are connected to the thyristor 33 on the other side. The anode of the first diode 25 is connected to the first terminal 15, and the cathode is connected to the anode of the thyristor 33. The cathode of the second diode 25 is connected to the first terminal 15, and the anode is connected to the cathode of the thyristor 33. The cathode of the third diode 25 is connected to the second terminal 17, and the anode is connected to the cathode of the thyristor 33. The anode of the fourth diode 25 is connected to the second terminal 17, and the cathode is connected to the anode of the thyristor 33.

[0068] The thyristor 33 is adapted to be in a short-circuit configuration and an open-circuit configuration and is adapted to switch back and forth between the short-circuit configuration and the open-circuit configuration. When the thyristor 33 is in the short-circuit configuration, the bypass unit 27 is also in the short-circuit configuration and bypasses the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19. In particular, due to the arrangement of the four diodes 25 and one thyristor 33, when the bypass unit 27 is in the short-circuit configuration, the bypass unit 27 can bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19 in two directions, i.e., from the first terminal 15 to the second terminal 17, and from the second terminal 17 to the first terminal 15. Preferably, the bypass direction depends on the voltage applied to the first terminal 15 and the second terminal 17. When the thyristor 33 is in an open circuit configuration, the bypass unit 27 is also in an open circuit configuration and does not bypass the first switching element 19, the second switching element 19, the third switching element 19, and the fourth switching element 19.

[0069] Furthermore, the cell control unit 29 is connected to the gate of one thyristor 33 and is adapted to supply a control signal to the thyristor 33 so that the configuration of the thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration. This allows the configuration of the bypass unit 27 to be changed from a short-circuit configuration to a short-circuit configuration. Therefore, the configuration of the bypass unit 27 can be controlled by only controlling the thyristor 33. Therefore, the bypass unit 27 shown in FIG. 9 provides a bypass unit 27 that is easy to control and energy-efficient. Furthermore, the bypass unit 27 shown in FIG. 9 requires only one thyristor 33.

[0070] FIG. 10 shows a portion of a first embodiment of the bypass unit 27 of the first to sixth embodiments of the cell 9 shown in FIGS. 2 to 4 and 7 to 9. The thyristor 33 shown in FIG. 10 may be any of the thyristors 33 shown in FIGS. 3, 4, 8, and 9. A cell control unit 29, not shown in FIG. 10, is connected to the gate of the thyristor 33 via a latching relay 37. This latching relay 37 may constitute a memory unit or a part of a memory unit. This latching relay 37 comprises an input terminal 39 adapted to receive a control signal from the cell control unit 29 and a normally open contact terminal 41 adapted to be in an open configuration and a closed configuration. Just as the configuration of the thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration, this latching relay 37 is changed from an open configuration to a closed configuration and from a closed configuration to an open configuration depending on the control signal received from the cell control unit 29.

[0071] FIG. 11 shows a portion of a second embodiment of the bypass unit 27 of the first to sixth embodiments of the cell 9 shown in FIGS. 2 to 4 and 7 to 9. The thyristor 33 shown in FIG. 11 may be any of the thyristors 33 shown in FIGS. 3, 4, 8, and 9. A diode 25 is connected to the thyristor 33. In this case, the anode of the diode 25 is connected to the anode of the thyristor 33, and the cathode of the diode 25 is connected to the gate of the thyristor 33. Due to this configuration, when the bypass unit 27 needs to be short-circuited, for example, when a bonding wire of the diode 25 of one of the switching elements 19 fails, the thyristor 33 can operate as a diode.

[0072] FIG. 12 shows a portion of a third embodiment of the bypass unit 27 of the first to sixth embodiments of the cell 9 shown in FIGS. 2 to 4 and 7 to 9. The thyristor 33 shown in FIG. 12 may be any of the thyristors 33 shown in FIGS. 3, 4, 8, and 9. The cell control unit 29, not shown in FIG. 12, is connected to the gate of the thyristor 33 via a latching relay 37. This latching relay 37 includes a memory unit or part of a memory unit, a resistor 43, and an N-channel metal oxide semiconductor field effect transistor (N-channel MOSFET) 45. This latching relay 37 includes an input terminal 39 adapted to receive a control signal from the cell control unit 29 and a normally open contact terminal 41 adapted to be in an open configuration and a closed configuration. Just as the configuration of the thyristor 33 can be changed from a short circuit configuration to an open circuit configuration and from an open circuit configuration to a short circuit configuration, the latching relay 37 is adapted to be changed from an open configuration to a closed configuration and from a closed configuration to an open configuration depending on a control signal received from the cell control unit 29.

[0073] To change the configuration of the thyristor 33, the latching relay 37 is connected to the thyristor 33 via a resistor 43 and an N-channel MOSFET 45. A first contact terminal of the contact terminal 41 is connected to the cathode of the thyristor 33. A second contact terminal of the contact terminal 41 is connected to a first terminal of the resistor 43 and a gate of the N-channel MOSFET 45. A second terminal of the resistor 43 is connected to a drain of the N-channel MOSFET 45 and an anode of the thyristor 33. Furthermore, a source of the N-channel MOSFET 45 is connected to the gate of the thyristor 33 so that the configuration of the thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration based on a control signal received by the latching relay 37 from the cell control unit 29.

[0074] FIG. 13 shows a part of a fourth embodiment of the bypass unit 27 of the first to sixth embodiments of the cell 9 shown in FIGS. 2 to 4 and 7 to 9. The thyristor 33 shown in FIG. 13 may be any of the thyristors 33 shown in FIGS. 3, 4, 8, and 9. A cell control unit 29, not shown in FIG. 13, is connected to the gate of the thyristor 33 via a memory unit. The gate includes a data storage unit 47, a resistor 43, which may be a resistor, and two N-channel MOSFETs 45. To change the thyristor 33 from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration, the memory unit is connected to the thyristor 33 via the resistor 43 and the two N-channel MOSFETs 45. A first terminal of the memory unit is connected to the first N-channel MOSFET 45 of the two N-channel MOSFETs 45 and to the cathode of the thyristor 33. A second terminal of the memory unit is connected to the gate of the first N-channel MOSFET 45. A drain of the first N-channel MOSFET 45 is connected to a first terminal of a resistor 43 and to a gate of a second N-channel MOSFET 45 of the two N-channel MOSFETs 45. A second terminal of the resistor 43 is connected to a drain of the second N-channel MOSFET 45 and an anode of the thyristor 33. Furthermore, a source of the second N-channel MOSFET 45 is connected to the gate of the thyristor 33 such that the configuration of the thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and vice versa based on a control signal received by the memory unit from the cell control unit 29.

[0075] The control signal received from the cell control unit 29 may indicate state information that may be written by the cell control unit 29 of the cell 9 to the data storage unit 47 of the memory unit. Preferably, the data storage unit 47 is a non-volatile data storage unit. The state information may indicate a configuration of the bypass unit 27, in particular the current configuration of the bypass unit 27, and / or a desired configuration of the bypass unit 27, and / or a configuration of the thyristor 33, in particular the current configuration of the thyristor 33, and / or a desired configuration of the thyristor 33. When the state information may indicate a configuration of the bypass unit 27, the state information may also be referred to as state information of the bypass unit 27. When the state information may indicate a configuration of the thyristor 33, the state information may also be referred to as state information of the thyristor 33. The current configuration of the bypass unit 27 is the configuration in which the bypass unit 27 is currently located. Similarly, the current configuration of the thyristor 33 is the configuration in which the thyristor 33 is currently located. The desired configuration of bypass section 27 may be the configuration required by bypass section 27, such that at least one switching element 19 of multiple switching elements 19 is bypassed or not bypassed. The desired configuration of thyristor 33 may be the configuration required by thyristor 33, such that bypass section 27 is in its desired configuration.

[0076] Figure 14 shows part of a fifth embodiment of the bypass section 27 of the first to sixth embodiments of the cell 9 shown in Figures 2 to 4 and 7 to 9. The fifth embodiment of the bypass section 27 shown in Figure 14 is essentially equivalent to the third embodiment of the bypass section 27 shown in Figure 12.

[0077] The first thyristor 33 shown on the left side of FIG. 12 may be any of the thyristors 33 shown in FIGS. 3, 4, 8, and 9. A cell control unit 29, not shown in FIG. 14, is connected to the gate of the first thyristor 33 via a latching relay 37. This latching relay 37 may comprise a data storage unit or part of a memory unit, a resistor 43, which may be a resistor, and an N-channel MOSFET 45. The latching relay 37 comprises an input terminal 39 adapted to receive a control signal from the cell control unit 29 so that the configuration of the first thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from the open-circuit configuration to a short-circuit configuration, and a normally open contact terminal 41 adapted to be in an open configuration and a closed configuration and adapted to be changed from the open configuration to the closed configuration and from the closed configuration to the open configuration depending on the control signal received from the cell control unit 29. To change the configuration of the first thyristor 33, the latching relay 37 is connected to the first thyristor 33 via a resistor 43 and an N-channel MOSFET 45. A first contact terminal of the contact terminal 41 is connected to the cathode of the first thyristor 33. A second contact terminal of the contact terminal 41 is connected to a first terminal of the resistor 43 and a gate of the N-channel MOSFET 45. A second terminal of the resistor 43 is connected to the drain of the N-channel MOSFET 45 and an anode of the first thyristor 33. Furthermore, a source of the N-channel MOSFET 45 is connected to the gate of the first thyristor 33 so that the configuration of the first thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from the open-circuit configuration to a short-circuit configuration based on a control signal received by the latching relay 37 from the cell control unit 29.

[0078] The bypass unit 27 further includes a second thyristor 33 shown on the right side of FIG. 14 . The anode of the second thyristor 33 is connected to the cathode of the first thyristor 33, and the cathode of the second thyristor 33 is connected to the anode of the first thyristor 33. The bypass unit 27 also includes one diode 25 connected to the second thyristor 33. The anode of the diode 25 is connected to the cathode of the first thyristor 33 and the anode of the second thyristor 33. The cathode of the diode 25 is connected to the gate of the second thyristor 33. Due to this configuration, when the bypass unit 27 needs to be short-circuited, for example, when a bonding wire of the diode 25 of one of the multiple switching elements 19 fails, the second thyristor 33 can operate as a diode.

[0079] 14 also shows a first transformer 49 and a second transformer 49. The first transformer 49 and the second transformer 49 are each connected to a power and data recovery block 51 of the bypass unit 27. The first transformer 49 is connected to a first cell 9 adjacent to the cell 9, and the bypass unit 27 is a part of this cell 9. The second transformer 49 is connected to a cell 9 adjacent to the cell 9, and the bypass unit 27 is a part of this cell 9. The cell 9 and the adjacent first cell 9 form a cell pair consisting of adjacent cells 9. Similarly, the cell 9 and the adjacent second cell 9 form a cell pair consisting of adjacent cells 9. The power and data recovery block 51 has an output terminal connected to the input terminal 39 of the latching relay 37.

[0080] The adjacent first cell 9 has a cell control unit 29 adapted to supply a control signal via a first transformer 49 to the bypass unit 27, a portion of which is shown in Figure 14. A power and data recovery block 51 has an input terminal adapted to receive a control signal from the cell control unit 29 of the adjacent first cell 9 via the first transformer 49. Depending on the control signal that the power and data recovery block 51 receives from the cell control unit 29 of the adjacent first cell 9, the latching relay 37 receives a control signal from the power and data recovery block 51 so that the configuration of the first thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration. Thus, the cell control unit 29 of the adjacent first cell 9 is adapted to provide a control signal to the bypass unit 27, a portion of which is shown in Figure 14, so that the bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Furthermore, the adjacent first cell 9 has a power supply unit 31. The power supply unit 31 of the adjacent first cell 9 is adapted to provide power to the bypass unit 27 via a first transformer 49.

[0081] The adjacent second cell 9 has a cell control unit 29 adapted to supply a control signal via a second transformer 49 to the bypass unit 27, a portion of which is shown in Figure 14. An input terminal of the power and data recovery block 51 is also adapted to receive a control signal from the cell control unit 29 of the adjacent second cell 9 via the second transformer 49. Depending on the control signal that the power and data recovery block 51 receives from the cell control unit 29 of the adjacent second cell 9, the latching relay 37 receives a control signal from the power and data recovery block 51 so that the configuration of the first thyristor 33 can be changed from a short-circuit configuration to an open-circuit configuration and from an open-circuit configuration to a short-circuit configuration. Thus, the cell control unit 29 of the adjacent second cell 9 is adapted to provide a control signal to the bypass unit 27, a portion of which is shown in Figure 14, so that the bypass unit 27 changes its configuration from a short-circuit configuration to an open-circuit configuration or from an open-circuit configuration to a short-circuit configuration. Furthermore, the adjacent second cell 9 has a power supply unit 31. The power supply unit 31 of the adjacent second cell 9 is adapted to provide power to the bypass unit 27 via a second transformer 49.

[0082] In summary, the bypass section 27, part of which is shown in FIG. The bypass unit 27 can be controlled by the cell control unit 29 of the adjacent first cell 9 and the cell control unit 29 of the adjacent second cell. Furthermore, both the power supply unit 31 of the adjacent first cell 9 and the power supply unit 31 of the adjacent second cell are adapted to supply power to the bypass unit 27, a part of which is shown in Figure 14. Thus, even if the cell control unit 29 and / or the power supply unit 31 of a cell 9 of which the bypass unit 27 is part fail in the event of a cell failure, the control of the bypass unit 27 and the power supply of the bypass unit 27 are guaranteed. Furthermore, even if the cell control unit 29 and / or the power supply of a cell 9 of which the bypass unit 27 is part fail in the event of a cell failure, the control of the bypass unit 27 and the power supply of the bypass unit 27 are still guaranteed. Similarly, even if the cell control unit 29 and / or power supply unit 31 of the adjacent first cell 9 or the adjacent second cell fails when one of the adjacent first cell 9 or the adjacent second cell is faulty, control of the bypass unit 27 and power supply to the bypass unit 27 are still guaranteed.

[0083] Furthermore, it is pointed out that the terms "comprising," "having," and "including" do not exclude other elements, and "a" does not exclude a plurality. It is also pointed out that a feature described with reference to one of the above representative embodiments may be considered to be described in combination with another feature of the other of the above representative embodiments. Reference signs in the claims should not be considered limiting. The present application relates to the invention described in the claims, but may also include the following configurations as other aspects. 1. A cell assembly (5) consisting of a plurality of cells (9), Each cell (9) of the plurality of cells (9) includes one first terminal (15), one second terminal (17), a plurality of switching elements (19), and one capacitance (21), the plurality of switching elements (19) being adapted to connect the capacitance (21) to the first terminal (15) and the second terminal (17) and to bypass the capacitance (21); a plurality of cells (9) of the plurality of cells (9) are connected in series such that, for each pair of adjacent cells (9), the first terminal (15) of one first cell (9) of the pair of adjacent cells (9) is connected to the second terminal (17) of one second cell (9) of the pair of adjacent cells (9); Each cell (9) further includes a bypass section (27), the bypass section (27) of each cell (9) being connected to the first terminal (15) and the second terminal (17) of the cell (9) and adapted to bypass at least one switching element (19) of the plurality of switching elements (19) of the cell (9) in a short-circuit configuration and not to bypass the at least one switching element (19) in an open-circuit configuration; Each cell (9) further comprises a cell control unit (29), and the cell control unit (29) of each cell (9) is adapted to supply control signals to the plurality of switching elements (19) of the cell (9) so that the plurality of switching elements (19) connect the capacitance (21) to the first terminal (15) and the second terminal (17) or so that the plurality of switching elements (19) bypass the capacitance (21); The cell assembly (5) is adapted such that the cell control unit (29) of each cell (9) is adapted to supply a control signal to the bypass unit (27) of at least one cell (9) among adjacent cells (9) so that each bypass unit (27) changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration. 2. Each cell (9) further comprises a power supply (31); The cell assembly (5) according to claim 1, wherein the power supply section (31) of each cell (9) is adapted to supply power to the bypass section (27) of at least one cell (9) among the adjacent cells (9). 3. 3. The cell assembly (5) according to the above 1 or 2, wherein the bypass section (27) of each cell (9) has one storage section. 4. The cell assembly (5) according to claim 3, wherein the memory unit of each cell (9) is connected to the cell control unit (29) of the cell (9) so that state information of the bypass unit (27), which indicates the configuration of the bypass unit (27), can be written to the memory unit by the cell control unit (29) of the cell (9). 5. 5. The cell assembly (5) according to any one of 3 and 4 above, wherein the storage section comprises a data storage section (47). 6. 6. The cell assembly (5) according to 5 above, wherein the data storage unit (47) is a non-volatile data storage unit. 7. 7. The cell assembly (5) according to any one of the above 3 to 6, wherein the memory section has a latching relay (37). 8. 8. The cell assembly (5) according to any one of claims 1 to 7, wherein the cell control unit (29) of each cell (9) is adapted to supply a control signal to the bypass unit (27) of one of the adjacent cells (9) so that each of the bypass units (27) changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration. 9. 8. The cell assembly (5) according to any one of 1 to 7 above, wherein the cell control unit (29) of each cell (9) is adapted to supply a control signal to the bypass units (27) of two adjacent cells (9) so that each of the bypass units (27) changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration. 10. The cell assembly (5) according to any one of 1 to 9 above, wherein the bypass section (27) of each cell (9) is adapted to bypass one switching element (19) of the plurality of switching elements (19) of the cell (9) in the short circuit configuration state, and not to bypass one of the switching elements (19) in the open circuit configuration state. 11. The cell assembly (5) according to any one of 1 to 9 above, wherein the bypass section (27) of each cell (9) is adapted to bypass two switching elements (19) of the plurality of switching elements (19) of the cell (9) in the short circuit configuration state, and not to bypass the two switching elements (19) in the open circuit configuration state. 12. The plurality of switching elements (19) of each cell (9) comprises two switching elements (19) connected to each other at a first connection point connected to the first terminal (15) of the cell (9); 12. The cell assembly (5) according to any one of 1 to 11 above, wherein a first switching element (19) of the two switching elements (19) is connected to a first terminal of the capacitance (21), and a second switching element (19) of the two switching elements (19) is connected to a second terminal of the capacitance (21) at a second connection point connected to the second terminal (17) of the cell (9). 13. The switching elements (19) of each cell (9) consist of four switching elements (19), a first switching element (19) of the four switching elements (19) and a second switching element (19) of the four switching elements (19) are connected to each other at a first connection point connected to the first terminal (15) of the cell (9); a third switching element (19) of the four switching elements (19) and a fourth switching element (19) of the four switching elements (19) are connected to each other at a second connection point connected to the second terminal (17) of the cell (9); The cell assembly (5) according to any one of 1 to 11 above, wherein the first switching element (19) and the third switching element (19) are connected to each other at a third connection point connected to a first terminal of the capacitance (21) of the cell (9), and the second switching element (19) and the fourth switching element (19) are connected to each other at a fourth connection point connected to a second terminal of the capacitance (21) of the cell (9). 14. 14. The cell assembly (5) according to any one of the above 1 to 13, wherein each of the at least one switching elements (19) of each cell (9) has one transistor. 15. A converter (1) having a plurality of arms (3), each of which is made of the cell assembly (5) described in any one of 1 to 14 above. [Explanation of symbols]

[0084] 1 converter 3 Arm 5. Cell Assembly 7 Inductance 9 cells 11 DC (direct current) terminal 13 AC (alternating current) terminal 15 Cell 1st terminal 17 Cell 2nd terminal 19 Switching element 21 Cell capacitance 23 Insulated Gate Bipolar Transistor (IGBT) 25 Diode 27 Bypass section 29 Cell control unit 31 Power supply section 33 Thyristor 35 Cell third terminal 37 Latching Relay 39 Input terminal 41 Contact terminal 43 Resistance 45 N-channel MOSFET 47 Data storage unit 49 Transformer 51 Power and Data Recovery Block

Claims

1. A cell assembly (5) consisting of a plurality of cells (9), Each cell (9) of the plurality of cells (9) includes a first terminal (15), a second terminal (17), a plurality of switching elements (19), and a capacitance (21), the plurality of switching elements (19) being adapted to connect the capacitance (21) to the first terminal (15) and the second terminal (17) and to bypass the capacitance (21); a plurality of cells (9) of the plurality of cells (9) are connected in series such that for each pair of adjacent cells (9), the first terminal (15) of a first cell (9) of the pair of adjacent cells (9) is connected to the second terminal (17) of a second cell (9) of the pair of adjacent cells (9); Each cell (9) further includes a bypass portion (27), the bypass portion (27) of each cell (9) being connected to the first terminal (15) and the second terminal (17) of the cell (9) and adapted to bypass at least one switching element (19) of the plurality of switching elements (19) of the cell (9) in a short-circuit configuration and not to bypass the at least one switching element (19) in an open-circuit configuration; Each cell (9) further comprises a cell control unit (29), and the cell control unit (29) of each cell (9) is adapted to supply control signals to the plurality of switching elements (19) of the cell (9) so that the plurality of switching elements (19) connect the capacitance (21) to the first terminal (15) and the second terminal (17) or so that the plurality of switching elements (19) bypass the capacitance (21); In the cell assembly (5), the cell control unit (29) of each cell (9) is adapted to provide a control signal to the bypass unit (27) of at least one of the adjacent cells (9) so that each bypass unit (27) changes its configuration from the short-circuit configuration to the open-circuit configuration or from the open-circuit configuration to the short-circuit configuration when the cell control unit (29) fails or when communication between the cell control unit (29) and the bypass unit (27) of that cell (9) or communication between the main control unit of the converter (1) and the cell control unit (29) is impaired, The bypass section (27) of each cell (9) has at least one thyristor (33); Each cell (9) further comprises a power supply (31), the power supply (31) of each cell (9) being adapted to supply power to the bypass section (27) of at least one cell (9) of the adjacent cells (9); The cell control unit (29) of each cell (9) supplies a control signal to the gate of the thyristor (33) of at least one of the adjacent cells via an n-channel MOSFET (45) of the cell assembly (5).

2. 2. The cell assembly (5) of claim 1, wherein the bypass portion (27) of each cell (9) comprises a memory portion.

3. 3. The cell assembly (5) according to claim 2, wherein the memory unit of each cell (9) is connected to the cell control unit (29) of the cell (9) so that status information of the bypass unit (27) indicating the configuration of the bypass unit (27) can be written to the memory unit by the cell control unit (29) of the cell (9).

4. The cell assembly (5) according to any one of claims 2 and 3, wherein the storage unit comprises a data storage unit (47).

5. The cell assembly (5) according to claim 4, wherein the data storage unit (47) is a non-volatile data storage unit.

6. The cell assembly (5) according to any one of claims 2 to 5, wherein the memory unit has a latching relay (37).

7. 7. The cell assembly (5) according to any one of claims 1 to 6, wherein the cell control unit (29) of each cell (9) is adapted to supply a control signal to the bypass unit (27) of one of the adjacent cells (9) so that each of the bypass units (27) changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration.

8. The cell assembly (5) according to any one of claims 1 to 6, wherein the cell control unit (29) of each cell (9) is adapted to supply control signals to the bypass units (27) of two adjacent cells (9) so that each of the bypass units (27) changes its configuration from the short circuit configuration to the open circuit configuration or from the open circuit configuration to the short circuit configuration.

9. The cell assembly (5) according to any one of claims 1 to 8, wherein the bypass portion (27) of each cell (9) is adapted to bypass one switching element (19) of the plurality of switching elements (19) of the cell (9) in the short-circuit configuration, and not to bypass the switching element (19) in the open-circuit configuration.

10. The cell assembly (5) according to any one of claims 1 to 8, wherein the bypass portion (27) of each cell (9) is adapted to bypass two switching elements (19) of the plurality of switching elements (19) of the cell (9) in the short-circuit configuration, and not to bypass the two switching elements (19) in the open-circuit configuration.

11. The plurality of switching elements (19) of each cell (9) consists of two switching elements (19) connected to each other at a first connection point connected to the first terminal (15) of the cell (9), The cell assembly (5) according to any one of claims 1 to 10, wherein a first switching element (19) of the two switching elements (19) is connected to a first terminal of the capacitance (21), and a second switching element (19) of the two switching elements (19) is connected to a second terminal of the capacitance (21) at a second connection point connected to the second terminal (17) of the cell (9).

12. The switching elements (19) of each cell (9) consist of four switching elements (19), a first switching element (19) of the four switching elements (19) and a second switching element (19) of the four switching elements (19) are connected to each other at a first connection point connected to the first terminal (15) of the cell (9); a third switching element (19) of the four switching elements (19) and a fourth switching element (19) of the four switching elements (19) are connected to each other at a second connection point connected to the second terminal (17) of the cell (9); The cell assembly (5) according to any one of claims 1 to 10, wherein the first switching element (19) and the third switching element (19) are connected to each other at a third connection point connected to a first terminal of the capacitance (21) of the cell (9), and the second switching element (19) and the fourth switching element (19) are connected to each other at a fourth connection point connected to a second terminal of the capacitance (21) of the cell (9).

13. The cell assembly (5) according to any one of the preceding claims, wherein each switching element (19) of at least one of the switching elements (19) of each cell (9) comprises a transistor.

14. A converter (1) having a plurality of arms (3), each of said arms (3) consisting of a cell assembly (5) according to any one of claims 1 to 13.

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