Method and communication system for synchronous switching changes in a modular battery

Abstract

The present invention relates to a method for synchronous switching in a modular battery, wherein the modular battery comprises a central controller and a high-speed bus (101) arranged between the central controller and the battery modules, wherein the central controller selects a respective switching state from predetermined switching states for each battery module at each switching cycle, wherein module state information for the respective battery module is generated with a respective module state and switching state, wherein a broadcast message (105) consisting of coded module state information with a transition command (113) and a termination error bit (112) is sent via the high-speed bus at each switching cycle per string, and wherein synchronous switching is implemented in all battery modules.by triggering a transition between module states and / or, within a module state, a transition between switching states using the transition command. Furthermore, a communication system on which the procedure is executed is presented.

Description

[0001] The present invention relates to a method for synchronous switching in a modular battery. Furthermore, a communication system on which the method is carried out is presented.

[0002] A modular battery is used in electric vehicles to supply power to a traction system. Each battery module contains an energy storage device or a DC voltage source, and by continuously switching the connection of the battery modules, one or more phases are generated to supply AC power to a traction motor. Such a modular battery can be implemented using a modular multilevel converter system, as 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.

[0003] The energy storage device in each battery module is connected via half-bridges with their respective input and output terminals. Depending on the configuration, the battery module can assume various switching states such as "serial," "parallel," or "bypass," each indicating how the energy storage device is connected within the string of battery modules. Each switching state corresponds to a configuration of the semiconductor switch positions in the half-bridges.

[0004] However, a switching fault in the battery modules can also lead to short circuits if the fault creates a circuit between energy storage devices in adjacent battery modules, or if the energy storage device in one battery module is short-circuited via half-bridges in the adjacent module. Short circuits can also occur, particularly in module architectures where more than one half-bridge is used for connection to the neighboring module, due to non-simultaneous or synchronous switching operations. The currents generated by such short circuits quickly reach a level where thermal degradation of the affected battery modules is imminent.

[0005] German patent application DE 10 2020 129 128 A1 describes a distributed real-time system on a modular multilevel converter. The switching states to be assumed for each switching cycle are communicated to the modules via a high-speed bus.

[0006] German patent application DE 10 2020 129 130 B3 discloses a safety concept for a modular multilevel converter. In the event of a termination error, the modular multilevel converter is put into a safe state.

[0007] The publication DE 10 2020 129 135 B3 discusses the use of a high-speed bus in a modular multilevel converter. A state machine implemented as a control program on a central controller interacts via the high-speed bus with state machines implemented on the individual modules.

[0008] Against this background, an object of the present invention is to provide a method for safe switching operations in a modular battery, which enables the switching operations to be triggered simultaneously in all battery modules. Furthermore, switching states should be assumed which, as far as possible, prevent short circuits in the event of a switching operation not performed simultaneously by neighboring modules. Finally, a control unit should be provided that implements the method.

[0009] To solve the aforementioned problem, a method for synchronous switching in a modular battery is proposed. In this method, the modular battery, connected to at least one traction motor, comprises a central controller, a plurality of battery modules arranged in at least one string, each module having a plurality of semiconductor switches, at least one energy storage device, and a module control unit. A high-speed bus runs between the central controller and along the respective battery modules of the at least one string. The respective switching positions of the plurality of semiconductor switches in each battery module correspond to a respective switching state. Each battery module has a plurality of module states, with at least one switching state being implemented for each module state.A module state machine is executed on the module control unit as a control program for assuming module states and the corresponding switching states to be implemented. The central controller selects a specific switching state from predefined states for each battery module at each switching cycle. Module state information is generated for each battery module, including its current module state and switching state. At each switching cycle, a broadcast message containing coded module state information, a transition command, and a termination error bit is sent over the high-speed bus for each string. Synchronous switching changes are implemented in all battery modules by triggering a transition between module states and / or, within a module state, a transition between switching states using the transition command.

[0010] The high-speed bus operates unidirectionally according to RS-485, for example, to ensure high transmission rates and short transmission times in the microsecond range for broadcast messages. More precisely, such a transmission channel enables differential data transmission due to a "physical layer" described in the ISO / OSI standard RS-485. For DC-free data transmission, 8b10b encoding is used, in which a number of zeros and ones are balanced on average and which, with only a 20% increase in bandwidth, is advantageous compared to, for example, Manchester encoding. The payload of the broadcast message is thus transmitted in encoded form and secured by cyclic redundancy checking (CRC).

[0011] A termination error bit, set by the central controller within the broadcast message, reaches all battery modules in all strings or phases via the high-speed bus, thus providing all components in the entire system with a synchronous termination error signal. This triggers, for example, an active short circuit as a safe motor state. Synchronous operation relies on the time-synchronized transmission of the broadcast message on the respective phase and synchronization with this broadcast message at the receiving end.

[0012] The transition command according to the invention controls synchronously executed transitions or changes between states in all battery modules. A transition to a fault state is also advantageously carried out synchronously.

[0013] In one embodiment of the method according to the invention, the predetermined switching states are selected from the following list: Semi-Bypass-plus, Semi-Bypass-minus, Semi-Serial-plus, Semi-Serial-minus, Parallel, Serial-plus, Serial-minus, Passive.

[0014] In a further embodiment of the method according to the invention, each battery module has at least one energy storage device and four half-bridges connected in parallel. A two-wire input connection is formed by a center tap on each of the first two half-bridges, and a two-wire output connection is formed by a center tap on each of the second two half-bridges. In such a topology, two adjacent battery modules each control a connection or interconnection between the two battery modules, i.e., those half-bridges or semiconductor switches arranged within them that connect both battery modules to each other by a center tap. During switching, both battery modules must therefore exhibit a high degree of synchronicity in their respective module control.

[0015] In general, in the method according to the invention, the number of bits to be transmitted within the broadcast message depends on the number of battery modules (and thus the interconnections, which are, for example, the number of battery modules per string plus one), as well as on the number of semiconductor switches (and thus half-bridges). For example: Number of bits per interconnection = log(number of switching states to be encoded, 2).

[0016] The aforementioned semi-bypass switching states according to the invention relate to the implementation of interconnection via only a half-bridge path in the respective battery module. Such semi-bypass switching states have the advantage that, in the event of an active short circuit, an energy storage short circuit via an adjacent battery module cannot occur even if synchronicity is not maintained or the adjacent battery module is in the switching state serial-plus, serial-minus, parallel, or passive.

[0017] In a further embodiment of the method according to the invention, an error loop is arranged in addition to the high-speed bus between the central controller and the respective battery modules of at least one string.

[0018] In a further embodiment of the method according to the invention, if a termination error bit of the broadcast message is set, a termination error is reported by the respective battery module via the error loop.

[0019] Furthermore, a communication system for a modular battery is claimed, in which the modular battery, connected to at least one traction motor, comprises the communication system, a central controller, a plurality of battery modules arranged in at least one string, each of which has a plurality of semiconductor switches, at least one energy storage device, and a module control unit, and a high-speed bus running between the central controller and along the respective battery modules of the at least one string. The respective switching positions of the plurality of semiconductor switches of each battery module correspond to a respective switching state. The respective battery module has a plurality of module states, with at least one switching state being realizable or realized for each module state.The module control unit is configured to execute a module state machine as a control program for assuming module states and implementing the corresponding switching states. The central controller is configured to select a specific switching state from predefined switching states for each battery module at each switching cycle. The communication system is designed to generate module state information for each battery module, including the respective module state and switching state. At each switching cycle per string, it sends a broadcast message containing coded module state information, a transition command, and an abort error bit via the high-speed bus. Synchronous switching changes are implemented in all battery modules by triggering a transition between module states and / or, within a module state, a transition between switching states using the transition command.

[0020] In one embodiment of the communication system according to the invention, the specified switching states are selected from the following list: Semi-Bypass-plus, Semi-Bypass-minus, Semi-Serial-plus, Semi-Serial-minus, Parallel, Serial-plus, Serial-minus, Passive.

[0021] In a further embodiment of the communication system according to the invention, each battery module has at least one energy storage device and four half-bridges connected in parallel. A two-wire input connection is formed by a center tap on each of the first two half-bridges, and a two-wire output connection is formed by a center tap on each of the second two half-bridges.

[0022] In a further embodiment of the communication system according to the invention, in addition to the high-speed bus between the central controller and the respective battery modules of at least one string, a respective error loop is arranged.

[0023] In a further embodiment of the communication system according to the invention, it is configured to report a termination error via the error loop through the respective battery module when a termination error bit is set within the broadcast message.

[0024] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0025] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention. Fig. Figure 1 schematically shows a format structure of a broadcast message in one embodiment of the method according to the invention. Fig. Figure 2 schematically shows a module state machine running on a control unit of a battery module in an embodiment of the method according to the invention.

[0026] In Fig. Figure 1 schematically illustrates the structure 100 of a broadcast message 105 in one embodiment of the method according to the invention. On the transmitting side 110, the broadcast message 105 is composed of 24 bits 113 consisting of a transition instruction and encoded module state information 111, which comprises the switching states of battery modules connected in a respective string of a modular battery, plus two bits 112 containing a termination error bit, to form a 26-bit payload 115. For transmission control by means of cyclic redundancy checking (CRC) 114, a further 14 information bits 117 follow, resulting in a message packet with a total of 40 information bits (5 bytes) 118. This achieves a minimum Hamming distance of six to reliably detect individual bit and packet errors with a high probability.Through an 8b10b encoding 119 performed on each byte, the 40 information bits 118 are transformed into the broadcast message 105 with 50 transmission characters 107. The broadcast message 105 is positioned in the high-speed bus 101 between inter-packet intervals or inter-packet gaps 102, 103, and with a 10-character lead 104, resulting in a message packet of 60 characters 108. All battery modules can synchronize to this pattern upon receiving a broadcast message. With a message length of 60 characters 108, a transmission frequency of 100 MHz and a data rate of 20 MSPS result in a transmission time of three microseconds.These transmission times, advantageous for a rapid shutdown of the modular battery in the event of a termination error, are achieved according to the invention by the arrangement of the unidirectional high-speed bus and by limiting the transmission to pure switching states (and not individual switching positions of semiconductor switches). In the respective battery module connected to the high-speed bus 101, the broadcast message 105 is unpacked again via an 8b10b decoding 129 120, and the payload 126 with 26 bits is received as transmitted information 125, while the 14 information bits 127 are supplied to the cyclic redundancy check. It is conceivable that further bits are appended after the cyclic redundancy check, e.g., for the implementation of Reed-Solomon codes in order to not only detect corrupted bits by means of CRC, but also to correct them.

[0027] In Fig.Figure 2 schematically shows a module state machine 200 operating on a control unit of a battery module of a modular battery in an embodiment of the method according to the invention. In an accompanying legend 299, a diagonally hatched circle 291 corresponds to a state hard-coupled with respective semiconductor switches. A circle 292 corresponds to a state or intermediate state that is triggered or arranged synchronously in all battery modules by a central controller via a high-speed bus message. A checkered circle 293 corresponds to a respective termination fault state. A dashed arrow 294 corresponds to a direct transition to a respective termination fault state 231, 232, while a solid arrow 295 represents a transition arranged via the high-speed bus message (abbreviated HSB). The module state machine 200 begins after a "PowerOnReset" (POR) or...“DesignReset” 210 with a passive module state 211 as the POR input state 201, i.e., a switching state is executed “passively”, which corresponds to an open switching position of all semiconductor switches in the battery module. Due to the necessity of switching adjacent battery modules synchronously in their switching positions of the respective semiconductor switches, since any two adjacent battery modules control a connection or “interconnection” between them – and in particular between their respective energy storage devices – this passive module state 211 is “hard-coded” 261, i.e., directly connected to the respective gate controls of the semiconductor switches of the battery module. An HSB command 251 contained in the HSB message switches to a synchronization module state 212 in order to synchronize a module control unit with a command clock in the HSB 202.The synchronization module state 212 is also hard-coded as a "passive" switching state 261. Both the safe passive module state 211 and the synchronization module state 212 transition to a passive end module state 213 based on an HSB command ShutDown 250 or 252, respectively, with the passive end module state 213 also being hard-coded 263. From the synchronization module state 212, an HSB command 253 leads to an area 262 with HSB commands 203 executed synchronously by all modules. The semiconductor switches, e.g., formed by MOSFETs, are not hard-coded, but rather, due to the prior synchronization of the respective module control to the high-speed bus, more precisely to a clocking of broadcast messages on the high-speed bus, HSB commands transmitted by the high-speed bus are now converted into switching states (e.g., (serial, parallel, semi-bypass, etc.). First, a control module state 221 is reached, in which, for example,A charging process can be performed. A transition to the passive end module state 213 can also occur from control module state 221 with an HSB command 254, such as ShutDown. While the passive end module state 213 ultimately means that the traction system is forced to perform a restart, it is conceivable to replace the passive end module state 213 with a state initiating a recovery. Furthermore, a transition to an engine preparation module state 222 is possible with an HSB command 255. If an abort error occurs, depending on the assumed module state 221 or 222, a direct transition 241, 242 takes place – i.e., executed immediately by the respective battery module without waiting for an HSB command – to a control abort error state 231, which is assigned to the switching state "passive". The control abort error state 231 is, in turn, hard-coded as the switching state "passive" 263.The motor preparation module state 222 is an intermediate state from which a transition to motor module state 223 occurs upon HSB command 256. In motor module state 223, for example, motor operation takes place, during which the modular battery is discharged. From motor module state 223, a transition to control preparation module state 224 is performed upon HSB command 257. If an abort fault occurs, depending on the assumed module state 223 or 224, a direct transition 243, 244 to a motor abort fault state 232, which is associated with the switching state "Semi-Bypass", takes place. The motor shutdown fault condition 232 is also hard-coded as the switching state "Semi-Bypass" 263. Providing two different shutdown fault conditions 231, 232 as fail-safe conditions 204 is advantageous, since the safe switching condition during motor operation is the switching condition "Semi-Bypass", while during charging, for example, the switching condition is "passive".In the respective intermediate states 222, 224, all modules are switched to the switching state (semi-bypass or passive) corresponding to the respective abort fault state 231, 232, in preparation for the motor module state 223 or control module state 221, so that the previously occurring operation is no longer carried out, but if an abort fault 241, 242, 243, 244 occurs, it is ensured that all battery modules from the module state 221, 223 assigned to the respective operating state (motor or charging) reach the same abort fault state 231 or 232. Finally, from the two abort fault states 231, 232, a transition to the passive end module state 213 occurs via an HSB command 259, e.g., ShutDown. Reference symbol list 100 Format scheme of a broadcast message 101 High-speed bus 102 Interpacket distance 103 Interpacket distance 104 Message Header 105 Broadcast message 106 10 characters or transmission characters 107 50 characters or transmission characters 108 60 characters or transmission characters 110 Broadcaster-side compilation of the broadcast message 111 Input data 112 Two information bits, one of which is the termination error bit 113 24 information bits with transition command and switching states 114 on cyclic redundancy testing 115 Total 26 bits 116 Information to be transmitted 26 bits (payload) 117 14 Information bits for cyclic redundancy checking (CRC) 118 40 information bits (5 bytes) 119 Five times 8b10b encoding 120 Receiving-side decomposition of the broadcast message 124 On cyclic redundancy testing 125 pieces of information transmitted 126 Received Information 26 Bits (payload) 127 14 Information bits for cyclic redundancy checking (CRC) 129 Five times 8b10b decoding 200 module state machines for module control 201 POR Input state 202 FPGA synchronized with HSB-CMD state 203 HSB-CMD controlled states 204 fail-safe states 210 Entry action after POR or design reset 211 Passive State Passive (PSV) 212 Passive State Synchronization (SYNC) 213 Passive State Passive Final (PSVF) 221 HSB-CMD State Control (CTRL) 222 HSB-CMD condition Prepare for Motor (PMOT) 223 HSB-CMD Engine Status (MOT) 224 HSB-CMD state Prepare for Control (PCTRL) 231 Passive State Error Control (ERRCT) 232 Half-Bypass State Error Motor (ERRM) 241 In case of termination error 242 In case of termination error 243 In case of termination error 244 In case of termination error 250 HSBD-Cmd 251 HSBD-Cmd 252 HSBD-Cmd 253 HSBC Passiv 254 HSBC & Passive or HSBD-Cmd 255 HSBC Passiv 256 HSBC & Half-Bypass 257 HSBC & Half-Bypass 258 HSBC & Passiv 259 HSBC & Passive or HSBD-Cmd (Shut-down) 261 MOSFETs hardcoded 262 HSBC-controlled MOSFETs 263 MOSFETs hardcoded 291 States coupled to respective semiconductor switches 292 states synchronously switched over high-speed bus 293 Termination error states 294 Direct transition to abort error state 295 High-speed bus ordered crossing 299 Legend QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2020 129 128 A1

[0005] DE 10 2020 129 130 B3

[0006] DE 10 2020 129 135 B3

[0007] Cited non-patent literature

[0000] 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

[0002]

Claims

[1] Method for synchronous switching changes in a modular battery, in which the modular battery connected to at least one traction machine comprises a central controller, a plurality of battery modules arranged in at least one string, each of which has a plurality of semiconductor switches, at least one energy storage device and a module control unit, and for the at least one string between the central controller and along the respective battery modules of the at least one string, a respective high-speed bus (101), wherein respective switching positions of the plurality of semiconductor switches of a respective battery module correspond to a respective switching state, wherein the respective battery module has a plurality of module states (211, 212, 213, 221, 222, 223, 224, 231, 232), wherein for each module state (211, 212, 213, 221, 222, 223, 224, 231, 232) at least one switching state is realized,wherein a module state machine (200) is executed on the module control unit as a control program for assuming module states (211, 212, 213, 221, 222, 223, 224, 231, 232) and the respective switching states to be realized, wherein a respective switching state is selected from predetermined switching states by the central controller for each switching cycle for each battery module, wherein module state information is formed for the respective battery module with the respective module state and switching state, wherein a broadcast message (105) comprising coded module state information with a transition command (113) and an abort error bit (112) is sent via the high-speed bus (101) for each switching cycle per strand, and wherein synchronous switching changes are realized in all battery modules by a transition between module states (211, 212, 213, 221, 222, 223, 224, 231,232) and / or in a module state a transition between switching states is triggered by the transition command. [2] Method according to claim 1, in which the predetermined switching states are selected from the following list: semi-bypass plus, semi-bypass minus, semi-serial plus, semi-serial minus, parallel, serial plus, serial minus, passive. [3] Method according to one of the preceding claims, in which the respective battery module has at least one energy storage device and four half-bridges connected in parallel, wherein a two-wire input connection is formed by a respective center tap on two first half-bridges and a two-wire output connection is formed by a respective center tap on two second half-bridges. [4] Method according to one of the preceding claims, in which, in addition to the high-speed bus (101), a respective fault loop is arranged between the central controller and the respective battery modules of the at least one string. [5] Method according to claim 4, wherein, if an abort error bit of the broadcast message (105) is set, an abort error is reported by the respective battery module via the error loop. [6] Communication system of a modular battery, in which the modular battery connected to at least one traction machine comprises the communication system, a central controller, a plurality of battery modules arranged in at least one string, each of which has a plurality of semiconductor switches, at least one energy storage device and a module control unit, and for the at least one string between the central controller and along the respective battery modules of the at least one string, a respective high-speed bus (101), wherein respective switching positions of the plurality of semiconductor switches of a respective battery module correspond to a respective switching state, wherein the respective battery module has a plurality of module states (211, 212, 213, 221, 222, 223, 224, 231, 232), wherein for each module state (211, 212, 213, 221, 222, 223, 224, 231, 232) at least one switching state realizable or realized,wherein the module control unit is configured to execute a module state machine (200) on the module control unit as a control program for assuming module states (211, 212, 213, 221, 222, 223, 224, 231, 232) and to implement respective switching states, wherein the central controller is configured to select a respective switching state from predetermined switching states for each switching cycle for each battery module, wherein the communication system is designed to form module state information for the respective battery module with the respective module state and switching state, to send a broadcast message (105) comprising coded module state information with a transition command (113) and an abort error bit (112) via the high-speed bus (101) for each switching cycle per strand, and to implement synchronous switching changes in all battery modules by a transition between module states (211, 212, 213, 221, 222, 223, 224, 231,232) and / or in a module state a transition between switching states is triggered by the transition command. [7] Communication system according to claim 6, wherein the predetermined switching states are selected from the following list: semi-bypass plus, semi-bypass minus, semi-serial plus, semi-serial minus, parallel, serial plus, serial minus, passive. [8] Communication system according to one of claims 6 or 7, wherein the respective battery module has at least one energy storage device and four half-bridges connected in parallel, wherein a two-wire input terminal is formed by a respective center tap on two first half-bridges and a two-wire output terminal is formed by a respective center tap on two second half-bridges. [9] Communication system according to one of claims 6 to 8, wherein in addition to the high-speed bus (101) a respective fault loop is arranged between the central controller and the respective battery modules of the at least one string. [10] Communication system according to claim 9, which is configured to report an abort error via the error loop when an abort error bit of the broadcast message (105) is set by the respective battery module.

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