Method and circuit for a semi-switching state in a modular multilevel converter

Abstract

The present invention relates to a method and a circuit for a semi-switching state in a modular battery, wherein the modular battery comprises a central controller and several battery modules (10) arranged in at least one string, the switching states of which are controlled by the central controller. Each battery module is connected by four half-bridges (1, 2, 3, 4, 5, 6, 7, 8) and an energy storage device (9), the four half-bridges being connected in parallel with the energy storage device. In each battery module, a two-wire input connection (91, 92) is formed by a center tap on the first and second half-bridges, respectively, and a two-wire output connection (93, 94) is formed by a center tap on the third and fourth half-bridges, respectively. A phase in a high-voltage system is formed at the two-wire output connection of the last battery module in the at least one string.The central controller sends a signal to the respective battery module to enter a semi-switching state, whereby the semi-switching state is formed by a semi-bypass switching state (21, 22) or a semi-serial switching state. Upon receiving the signal for the semi-switching state, a current path (23) is formed in the respective battery module between only a single wire of the two-wire input terminal and only a single wire of the two-wire output terminal.

Description

[0001] The present invention relates to a method and a circuit for a semi-switching state in a modular multilevel converter with serial and parallel connectivity.

[0002] In a modular multilevel converter with serial and parallel connectivity, a short circuit in an energy storage device can occur if a first module is connected to a bypass or in series using all half-bridges, and the adjacent module is in the parallel switching state to the first module. Such a short circuit would be particularly possible in a parallel connection between two adjacent battery modules immediately before it, if one of the two battery modules changes its switching state, but the adjacent battery module continues to maintain the parallel switching state due to an error, e.g., a transmission error in the switching signal from the central controller. Such an error can also occur, for example, if adjacent battery modules are not switched completely synchronously or do not switch completely synchronously.Even deviations in switching behavior of just a few microseconds can be enough to cause a short-circuit current to flow at a current intensity that can damage components in the battery module, even leading to heat development beyond a flash point.

[0003] A modular multilevel converter system in which such illegal switching combinations can occur is described, for example, in "Goetz, SM; Peterchev, AV; Weyh, T., "Modular Multilevel Converter With Series and Parallel Module Connectivity: Topology and Control," Power Electronics, IEEE Transactions on, vol. 30, no. 1, pp. 203, 215, 2015. doi: 10.1109 / TPEL.2014.2310225. In this system, voltage differences between two connection terminals, e.g. of a power grid or a traction system of an electric car, are generated by configuring an electrical interconnection of energy storage devices in battery modules and by switching modulation between switching states to form arbitrary intermediate states.

[0004] Considerations regarding switching behavior and switching options are also discussed in the publication DE 20 2014 004 749 U1. This document particularly examines the estimation of module voltages based on the module states assumed.

[0005] A method for selecting specific switching states with which the battery modules are controlled is discussed in document DE 10 2018 125 728 B3. By dividing the switching states into an online and an offline part, a scheduler always has optimized switching tables available for selecting the switching states.

[0006] Against this background, it is an object of the present invention to provide a method that establishes a series or bypass switching state in a battery module of a modular multilevel converter that can be carried out safely, i.e., without short circuits, between adjacent battery modules. Furthermore, a circuit is to be provided that implements the method on a battery module of a modular multilevel converter.

[0007] To achieve the above-mentioned object, a method for a semi-switching state in a modular battery is proposed, wherein the modular battery has a central controller and a plurality of battery modules arranged in at least one string, the respective switching states of which are controlled by the central controller. Each battery module is formed by a first half-bridge, a second half-bridge, a third half-bridge, a fourth half-bridge and an energy storage device, wherein the four half-bridges are connected in parallel to the energy storage device. In the respective battery module, a two-wire input connection is formed by a respective center tap on the first half-bridge and the second half-bridge, and a two-wire output connection is formed by a respective center tap on the third half-bridge and the fourth half-bridge.A respective phase in a high-voltage system is formed at the two-wire output terminal of the last battery module in the at least one string. The central controller sends a signal to the respective battery module to enter a semi-switching state, whereby the semi-switching state is formed by a semi-bypass switching state or a semi-serial switching state. Upon receipt of the signal for the semi-switching state, a current path is formed in the respective battery module between only a single wire of the two-wire input terminal and only a single wire of the two-wire output terminal.

[0008] A respective low-side semi-bypass switching state is also called a semi-bypass minus switching state, as it bypasses the respective energy storage device on its negative pole. A respective high-side semi-bypass switching state is also called a semi-bypass plus switching state, as it bypasses the respective energy storage device on its positive pole. A respective controllable switch in the half-bridge is formed, for example, by a MOSFET. A respective semi-serial switching state connects the respective energy storage device either with a voltage increase as series plus or with a voltage decrease as series minus, via only one half-bridge connected to the respective input or output terminal.

[0009] The method according to the invention thus advantageously uses only one wire of the two-wire input connection and only one wire of the two-wire output connection to form the current path. This ensures that no short circuit can occur, regardless of the switching state of a respective adjacent battery module. The semi-bypass switching state thus advantageously provides a passive and robust solution for the given task, since in terms of control technology, for example, it does not aim to increase the synchronicity of a switching control, but rather excludes the possibility of a short circuit solely through the type of wiring, regardless of the switching state of a respective adjacent battery module. Furthermore, the semi-bypass can be implemented using two current paths in the battery module, so that, for example, a faulty semiconductor switch in one of the two current paths can be advantageously bypassed and the entire system can continue to operate.

[0010] In one embodiment of the method according to the invention, the semi-bypass switching state is selected from a group of the following switching states: low-side X1-X4 semi-bypass, low-side X2-X3 semi-bypass, low-side X1-X3 semi-bypass, low-side X2-X4 semi-bypass, high-side X1-X4 semi-bypass, high-side X2-X3 semi-bypass, high-side X1-X3 semi-bypass, high-side X2-X4 semi-bypass. X1, X2, X3, and X4 are designations for connections to the respective wires of the two-wire input connections (X1 to center tap of the first half-bridge, X2 to center tap of the second half-bridge) and the respective wires of the two-wire output connections (X3 to center tap of the third half-bridge, X4 to center tap of the fourth half-bridge).

[0011] In another embodiment of the method according to the invention, the semi-serial switching state is selected from a group of the following switching states: X1-X4-semi-serial-plus, X2-X3-semi-serial-plus, X1-X3-semi-serial-plus, X2-X4-semi-serial, X1-X4-semi-serial-minus, X2-X3-semi-serial-minus, X1-X3-semi-serial-minus, X2-X4-semi-serial-minus.

[0012] In a further embodiment of the method according to the invention, a switching state corresponding to the current path conducted only on one of the two input terminals or only on one of the two output terminals is assumed on a respective adjacent battery module.

[0013] In another embodiment of the method according to the invention, the semi-switching state on the respective battery module is assumed independently of a respective switching state on a respective adjacent battery module.

[0014] Furthermore, a circuit for a semi-switching state in a modular battery is claimed, wherein the circuit comprises a central controller and a plurality of battery modules of the modular battery arranged in at least one string, the switching states of which are controlled by the central controller. Each battery module is formed by a first half-bridge, a second half-bridge, a third half-bridge, a fourth half-bridge and an energy storage device, wherein the four half-bridges are connected in parallel to the energy storage device. In each battery module, a two-wire input connection is formed by a respective center tap on the first half-bridge and the second half-bridge and a two-wire output connection is formed by a respective center tap on the third half-bridge and the fourth half-bridge, wherein a respective phase in a high-voltage system is formed at the two-wire output connection of the last battery module in the at least one string.The central controller is configured to send a signal to the respective battery module to enter a semi-switching state, wherein the semi-switching state is formed by a semi-bypass switching state or a semi-serial switching state. Upon receiving the signal for the semi-switching state, the respective battery module is designed to form a current path between only a single wire of the two-wire input connection and only a single wire of the two-wire output connection. Thus, the current path to the respective input or output connection is realized via only one switch.

[0015] In one embodiment of the circuit according to the invention, the semi-bypass switching state is selected from a group of the following switching states: low-side X1-X4 semi-bypass, low-side X2-X3 semi-bypass, low-side X1-X3 semi-bypass, low-side X2-X4 semi-bypass, high-side X1-X4 semi-bypass, high-side X2-X3 semi-bypass, high-side X1-X3 semi-bypass, high-side X2-X4 semi-bypass.

[0016] In another embodiment of the circuit according to the invention, the semi-serial switching state is selected from a group of the following switching states: X1-X4-semi-serial-plus, X2-X3-semi-serial-plus, X1-X3-semi-serial-plus, X2-X4-semi-serial, X1-X4-semi-serial-minus, X2-X3-semi-serial-minus, X1-X3-semi-serial-minus, X2-X4-semi-serial-minus.

[0017] In a further embodiment of the circuit according to the invention, the central controller is configured to control a switching state on a respective adjacent battery module corresponding to the current path passed through only on one of the two input terminals or only on one of the two output terminals.

[0018] In another embodiment of the circuit according to the invention, the central controller is configured to control the semi-switching state on the respective battery module independently of a respective switching state on a respective adjacent battery module.

[0019] Furthermore, a modular multilevel converter is claimed which has a circuit according to the invention and on which a method according to the invention is carried out.

[0020] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0021] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0022] The figures are described coherently and comprehensively; the same components are assigned the same reference symbols. Fig. 1 shows a schematic diagram of a bypass circuit on a battery module from the prior art. Fig. 2 schematically shows a first semi-bypass circuit in an embodiment of the method according to the invention. Fig. 3 schematically shows a second semi-bypass circuit in a further embodiment of the method according to the invention. Fig. 4 schematically shows a third semi-bypass circuit in a further embodiment of the method according to the invention. Fig. 5 schematically shows a fourth semi-bypass circuit in a further embodiment of the method according to the invention. Fig. 6 shows schematically a circuit with serial switching state on the battery module from the prior art. Fig. 7 schematically shows a first semi-serial circuit in another embodiment of the method according to the invention. Fig. 8 schematically shows a second semi-serial circuit in yet another embodiment of the method according to the invention. Fig. 9 schematically shows a third semi-serial circuit in a further different embodiment of the method according to the invention. Fig. 10 schematically shows a fourth semi-serial circuit in a still further different embodiment of the method according to the invention.

[0023] In Fig. 1 schematically shows a bypass circuit 11, 12 on a battery module 10 from the prior art. The battery module 10 comprises a first half-bridge with an upper (high) semiconductor switch 1 and a lower (low) semiconductor switch 2, a second half-bridge with an upper semiconductor switch 3 and a lower semiconductor switch 4, a third half-bridge with an upper semiconductor switch 5 and a lower semiconductor switch 6, a fourth half-bridge with an upper semiconductor switch 7 and a lower semiconductor switch 8, and an energy storage device 9. The respective semiconductor switches 1, 2, 3, 4, 5, 6, 7, 8 are formed, for example, by MOSFETs. The energy storage device 9 can be any form of DC voltage source, such as a battery cell or capacitor.At the first half-bridge, a first wire of a two-wire input terminal 91 is formed by center tapping, and at the second half-bridge, a second wire of a two-wire input terminal 92 is formed by center tapping. At the third half-bridge, a first wire of a two-wire output terminal 93 is formed by center tapping, and at the fourth half-bridge, a second wire of a two-wire output terminal 94 is formed by center tapping. A circuit diagram 11 and a circuit diagram 12 each show a low-side bypass switching state and a high-side bypass switching state, also referred to as a bypass minus switching state and a bypass plus switching state, respectively, from the prior art. These switching states, which apply to both wires (X1, X2) of the two-wire input connection 91, 92 and both wires (X3, X4) of the two-wire output connection 93, 94, lead to a current path 13 on a line with a negative pole ora positive pole of the energy storage device 9 in contact with the low-side or high-side of the battery module 10 (bypass). However, if an immediately adjacent battery module is connected in parallel, for example, to the energy storage device 9 of the battery module 10, perhaps from a previous switching cycle, and has not yet switched over due to a fault, this would result in a short-circuit-like discharge of the energy storage device in the adjacent battery module that has not yet switched over due to a fault.

[0024] In Fig. 2 schematically shows a first semi-bypass circuit in an embodiment of the method according to the invention, which according to the invention avoids the double loading of the respective two-wire input and output terminals and directs a current path 23 only to a single wire X1 of the two-wire input terminal 91 and a single wire X4 of the two-wire output terminal 94. Depending on which pole of the energy storage device 9 is bypassed by the current path 23, a low-side X1-X4 semi-bypass switching state (also X1-X4 semi-bypass minus switching state) 21 or a high-side X1-X4 semi-bypass switching state (also X1-X4 semi-bypass plus switching state) 22 is obtained. Such a logical switching state can be combined with other logical switching states in adjacent battery modules, whereby, in contrast to the bypass switching state from the prior art, non-permitted combinations cannot cause a short circuit of the respective energy storage devices.If, in addition, a local control of a battery module 10 detects one of the eight semiconductor switches 1, 2, 3, 4, 5, 6, 7, 8 as malfunctioning, this can be switched to a different connection (see .) using the method according to the invention by selecting either between low-side and high-side or by selecting another half-bridge. Fig. 3 to 5) can be bypassed.

[0025] In Fig. 3 schematically shows a second semi-bypass circuit in a further embodiment of the method according to the invention, which conducts a current path 33 only to a single wire X2 of the two-wire input terminal 92 and a single wire X3 of the two-wire output terminal 93. Depending on which pole of the energy storage device 9 is bypassed by the current path 33, a low-side X2-X3 semi-bypass switching state (also X2-X3 semi-bypass minus switching state) 31 or a high-side X2-X3 semi-bypass switching state (also X2-X3 semi-bypass plus switching state) 32 is obtained.

[0026] In Fig. 4 schematically shows a third semi-bypass circuit in yet another embodiment of the method according to the invention, which conducts a current path 43 only to a single wire X1 of the two-wire input terminal 91 and a single wire X3 of the two-wire output terminal 93. Depending on which pole of the energy storage device 9 is bypassed by the current path 43, a low-side X1-X3 semi-bypass switching state (also X1-X3 semi-bypass minus switching state) 41 or a high-side X1-X3 semi-bypass switching state (also X1-X3 semi-bypass plus switching state) 42 is obtained.

[0027] In Fig. Figure 5 schematically shows a fourth semi-bypass circuit in a further embodiment of the method according to the invention, which conducts a current path 53 only to a single wire X2 of the two-wire input terminal 92 and a single wire X4 of the two-wire output terminal 94. Depending on which pole of the energy storage device 9 is bypassed by the current path 53, a low-side X2-X4 semi-bypass switching state (also X2-X4 semi-bypass minus switching state) 51 or a high-side X2-X4 semi-bypass switching state (also X2-X4 semi-bypass plus switching state) 52 is obtained.

[0028] In Fig. Figure 6 schematically shows a circuit with a serial switching state 111, 112 on the battery module 10 from the prior art. Thus, circuit diagram 111 shows a serial plus switching state, and circuit diagram 112 shows a serial minus switching state. These switching states, which apply to both wires (X1, X2) of the two-wire input connection 91, 92 and both wires (X3, X4) of the two-wire output connection 93, 94, lead on the input side to a current path 113 on a low side or high side of the battery module 10 which is in contact with a negative pole or a positive pole of the energy storage device 9. However, if an immediately adjacent battery module is in, for example, a parallel circuit to the energy storage device 9 of the battery module 10, for example from a previous switching cycle, and has not yet switched over due to an error, this would lead to a short-circuit-like discharge of the energy storage device in the adjacent battery module which has not yet switched over due to an error.

[0029] In Fig. Figure 7 schematically shows a first semi-serial circuit in another embodiment of the method according to the invention, which according to the invention avoids the double loading of the respective two-wire input and output terminals and conducts a current path 123 only to a single wire X1 of the two-wire input terminal 91 and a single wire X4 of the two-wire output terminal 94. Depending on which pole of the energy storage device 9 is contacted by the current path 123 in the current direction, an X1-X4 semi-serial plus switching state 121 or an X1-X4 semi-serial minus switching state 122 is obtained. Such a logical switching state can be combined with other logical switching states in respectively adjacent battery modules, whereby, in contrast to the serial switching state of the prior art, prohibited combinations cannot cause a short circuit of the respective energy storage devices.If, in addition, a local control of a battery module 10 detects that one of the eight semiconductor switches 1, 2, 3, 4, 5, 6, 7, 8 is malfunctioning, this can be advantageously rectified using the method according to the invention by selecting the contacting of the respective pole of the energy storage device 9 in the current direction from the low side or the high side or by selecting a different half bridge to a different connection (see . Fig. 8 to 10) can be bypassed.

[0030] In Fig. Figure 8 schematically shows a second semi-serial circuit in yet another embodiment of the method according to the invention, which conducts a current path 133 only to a single wire X2 of the two-wire input terminal 92 and a single wire X3 of the two-wire output terminal 93. Depending on which pole of the energy storage device 9 is contacted by the current path 133 in the current direction, an X2-X3 semi-serial plus switching state 131 or an X2-X3 semi-serial minus switching state 132 is obtained.

[0031] In Fig. Figure 9 schematically shows a third semi-serial circuit in a further different embodiment of the method according to the invention, which conducts a current path 143 only to a single wire X1 of the two-wire input terminal 91 and a single wire X3 of the two-wire output terminal 93. Depending on which pole of the energy storage device 9 is contacted by the current path 143 in the current direction, an X1-X3 semi-serial plus switching state 141 or an X1-X3 semi-serial minus switching state 142 is obtained.

[0032] In Fig.Figure 10 schematically shows a fourth semi-serial circuit in yet another embodiment of the method according to the invention, which conducts a current path 153 only to a single wire X2 of the two-wire input terminal 92 and a single wire X4 of the two-wire output terminal 94. Depending on which pole of the energy storage device 9 is contacted by the current path 153 in the current direction, an X2-X4 serial plus switching state 151 or an X2-X4 serial minus switching state 152 is obtained. List of reference symbols 1 Upper semiconductor switch first half bridge 2 Lower semiconductor switch first half bridge 3 Upper semiconductor switch second half bridge 4 Lower semiconductor switch second half bridge 5 Upper semiconductor switch third half bridge 6 Lower semiconductor switch third half bridge 7 Upper semiconductor switch fourth half bridge 8 Lower semiconductor switch fourth half bridge 9 Energy storage 10 Battery module 11 Low-side bypass, bypass minus 12 high-side bypass, bypass plus 13 Current path 21 Low-Side X1-X4 Semi-Bypass 22 high side X1-X4 semi-bypass 23 Current path 31 Low-Side-X2-X3-Semi-Bypass 32 high side X2-X3 semi-bypass 33 current path 41 Low Side X1-X3 Sem i Bypass 42 high side X1-X3 semi-bypass 43 current path 51 Low-Side-X2-X4-Semi-Bypass 52 high side X2-X4 semi-bypass 53 current path 91 First wire two-wire input connection 92 Second wire two-wire input connection 93 Third wire two-wire output connection 94 Fourth wire two-wire output connection 111 Serial-plus switching state 112 Serial minus switching state 113 Current path 121 X1-X4-Semi-Serial-plus 122 X1-X4-Semi-Serial-minus 123 current path 131 X2-X3-Semi-Serial-plus 132 X2-X3-Semi-Serial-minus 133 current path 141 X1-X3-Semi-Serial-plus 142 X1-X3-Semi-Serial-minus 143 current path 151 X2-X4-Semi-Serial-plus 152 X2-X4-Semi-Serial-minus 153 current path QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 20 2014 004 749 U1

[0004] DE 10 2018 125 728 B3

[0005] Zitierte Nicht-Patentliteratur

[0000] Goetz, S.M.; Peterchev, A.V.; Weyh, T., „Modular Multilevel Converter With Series and Parallel Module Connectivity: Topology and Control,“ Power Electronics, IEEE Transactions on, vol.30, no.1, pp.203,215, 2015. doi: 10.1109 / TPEL.2014.2310225

[0003]

Claims

[1] Method for a semi-switching state in a modular battery, wherein the modular battery has a central controller and a plurality of battery modules (10) controlled by the central controller in their respective switching states and arranged in at least one string, wherein a respective battery module (10) is formed by a first half-bridge (1, 2), a second half-bridge (3, 4), a third half-bridge (5, 6), a fourth half-bridge (7, 8) and an energy store (9), wherein the four half-bridges are connected in parallel to the energy store (9), wherein in the respective battery module (10) a two-wire input connection (91, 92) is formed by a respective center tap on the first half-bridge (1, 2) and the second half-bridge and a two-wire output connection (93, 94) is formed by a respective center tap on the third half-bridge (5, 6) and the fourth half-bridge (7, 8), wherein at the two-wire output connection (93,94) of the last battery module (10) in which at least one strand forms a respective phase in a high-voltage system, wherein a signal for assuming a semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152) is sent from the central controller to the respective battery module (10), wherein the semi-switching state is formed by a semi-bypass switching state (21, 22, 31, 32, 41, 42, 51, 52) or a semi-serial switching state (121, 122, 131, 132, 141, 142, 151, 152), wherein in the respective battery module (10) after receiving the Signal for the semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152) a current path (23, 33, 43, 53, 123, 133, 143, 153) is formed between only a single wire of the two-wire input terminal (91, 92) and only a single wire of the two-wire output terminal (93, 94)., [2] Method according to claim 1, wherein the semi-bypass switching state (21, 22, 31, 32, 41, 42, 51, 52) is selected from a group of the following switching states: low-side X1-X4 semi-bypass (21), low-side X2-X3 semi-bypass (31), low-side X1-X3 semi-bypass (41), low-side X2-X4 semi-bypass (51), high-side X1-X4 semi-bypass (22), high-side X2-X3 semi-bypass (32), high-side X1-X3 semi-bypass (42), high-side X2-X4 semi-bypass (52). [3] Method according to claim 1, wherein the semi-serial switching state (121, 122, 131, 132, 141, 142, 151, 152) is selected from a group of the following switching states: X1-X4-semi-serial-plus (121), X2-X3-semi-serial-plus (131), X1-X3-semi-serial-plus (141), X2-X4-semi-serial (151), X1-X4-semi-serial-minus (122), X2-X3-semi-serial-minus (132), X1-X3-semi-serial-minus (142), X2-X4-semi-serial-minus (152). [4] Method according to one of the preceding claims, wherein on a respective adjacent battery module (10) a switching state corresponding to the current path (23, 33, 43, 53, 122, 133, 143, 153) conducted only on one of the two input terminals (91, 92) or only on one of the two output terminals (93, 93) is assumed. [5] Method according to one of claims 1 to 3, wherein the semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152) on the respective battery module (10) is assumed independently of a respective switching state on a respective adjacent battery module (10). [6] Circuit for a semi-switching state in a modular battery, wherein the circuit comprises a central controller and a plurality of battery modules (10) of the modular battery, which are controlled in their switching states by the central controller and are arranged in at least one string, wherein a respective battery module (10) is formed by a first half-bridge (1, 2), a second half-bridge (3, 4), a third half-bridge (5, 6), a fourth half-bridge (7, 8) and an energy store (9), wherein the four half-bridges are connected in parallel to the energy store (9), wherein in the respective battery module (10) a two-wire input terminal (91, 92) is formed by respective center taps on the first half-bridge (1, 2) and the second half-bridge (3, 4) and a two-wire output terminal (93, 94) is formed by respective center taps on the third half-bridge (5, 6) and the fourth half-bridge (7, 8), wherein on the two-wire Output connector (93,94) of the last battery module (10) in which at least one strand forms a respective phase in a high-voltage system, wherein the central controller is configured to send a signal to the respective battery module (10) to assume a semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152), wherein the semi-switching state is formed by a semi-bypass switching state (21, 22, 31, 32, 41, 42, 51, 52) or a semi-serial switching state (121, 122, 131, 132, 141, 142, 151, 152), wherein the respective battery module (10) is designed to form a current path (23, 33, 43, 53, 123, 133, 143, 153) between only a single wire of the two-wire input terminal (91, 92) and only a single wire of the two-wire output terminal (93, 94) after receiving the signal for the semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152). [7] Circuit according to claim 6, wherein the semi-bypass switching state (21, 22, 31, 32, 41, 42, 51, 52) is selected from a group of the following switching states: low-side X1-X4 semi-bypass (21), low-side X2-X3 semi-bypass (31), low-side X1-X3 semi-bypass (41), low-side X2-X4 semi-bypass (51), high-side X1-X4 semi-bypass (22), high-side X2-X3 semi-bypass (32), high-side X1-X3 semi-bypass (42), high-side X2-X4 semi-bypass (52). [8] Circuit according to claim 6, wherein the semi-serial switching state (121, 122, 131, 132, 141, 142, 151, 152) is selected from a group of the following switching states: X1-X4-semi-serial-plus (121), X2-X3-semi-serial-plus (131), X1-X3-semi-serial-plus (141), X2-X4-semi-serial (151), X1-X4-semi-serial-minus (122), X2-X3-semi-serial-minus (132), X1-X3-semi-serial-minus (142), X2-X4-semi-serial-minus (152). [9] Circuit according to one of claims 6 to 8, wherein the central controller is configured to control a switching state on a respective adjacent battery module (10) corresponding to the current path (23, 33, 43, 53, 123, 133, 143, 153) conducted only on one of the two input terminals (91, 92) or only on one of the two output terminals (93, 94). [10] Circuit according to one of claims 6 to 8, wherein the central controller is configured to control the semi-switching state (21, 22, 31, 32, 41, 42, 51, 52, 121, 122, 131, 132, 141, 142, 151, 152) on the respective battery module (10) independently of a respective switching state on a respective adjacent battery module (10). [11] Modular multilevel converter comprising a circuit according to any one of claims 6 to 10 and on which a method according to any one of claims 1 to 5 is carried out.

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