Welding method

Abstract

The invention relates to a method for welding at least one contact of at least one energy storage module, preferably of an electric vehicle, using a multi-level converter system, in which a plurality of energy storage modules and transistors are provided, wherein each energy storage module can be connected in parallel and / or in series to the respective neighbouring energy storage module, and the energy storage modules, preferably the transistors, are connected in such a way that a welding temperature is provided at the contact.

Description

[0001] Welding process

[0002] The invention relates to a method for welding at least one contact of at least one energy storage module.

[0003] Currently, contacts are welded using methods such as laser welding, bonding, and / or friction welding. Copper material, for example, can be attached to the contacts during this process. Screwing, clamping, and / or gluing are also fundamentally possible.

[0004] A disadvantage of this method is its relatively high cost, as it requires, for example, a welding robot—a movable arm through which an electric current flows. Laser welding also has the problem of requiring a lot of energy. The thickness of the materials can also be a limiting factor.

[0005] It is therefore an object of the invention to provide a method by which welding of a contact of at least one energy storage module is made possible in a simple manner.

[0006] This problem is solved by the independent claim procedure.

[0007] According to the invention, the method serves to weld at least one contact of at least one energy storage module and / or can be used for this purpose.

[0008] The energy storage module can be a storage device for an electrical source, preferably frequency-dependent, such as a battery, accumulator, fuel cell, solar cell, and / or (super)capacitor. The energy storage module can be used, for example, in electric vehicles, such as electric cars, electric trucks, and / or electric buses. Furthermore, the method can be applied to stationary energy storage systems and / or other inverter systems that are connected to the power grid and / or operated by an AC motor.

[0009] The method according to the invention uses a, preferably modular, multi-level converter system (MMC system).

[0010] A multilevel converter system describes a type of arrangement or circuit of several energy storage modules or transistors, e.g. MOSFETs.

[0011] According to the invention, a large number of energy storage modules and transistors are provided.

[0012] Each energy storage module can contain at least or exactly one battery, e.g. an accumulator, and / or at least or exactly one capacitor.

[0013] The transistors serve, for example, as switches by which current and / or voltage paths can be selected. This allows the energy storage modules to be integrated into a desired configuration or excluded from it.

[0014] Preferably, each energy storage module is assigned at least or exactly two, three, four, five, six, seven, eight, nine, ten or more transistors.

[0015] The transistor can be designed, for example, for a voltage of less than 500 V, 400 V, 300 V, 200 V, 100 V, 50 V, 40 V, 30 V, 20 V, or 10 V. Preferably, the transistor can be designed for a voltage between 2 V and 8 V, e.g.

[0016] The system can be designed for 3 V, 4 V, 5 V, 6 V, or 7 V. Each energy storage module can be connected in parallel and / or in series with its adjacent module. Preferably, each energy storage module can be connected in series with its adjacent module. Parallel connection is advantageous but not necessary.

[0017] Preferably, the adjacent energy storage modules are connected to each other via two current and / or voltage paths. Each path can be assigned a transistor.

[0018] For example, three transistors are provided between two adjacent energy storage modules. This allows the energy storage modules to be connected in parallel or in series, for example.

[0019] Multilevel converter systems are significantly more versatile than two-level converters. This allows for the creation of virtually any configuration. For example, the energy storage modules can be connected to each other in any configuration, such as in parallel or series. Individual energy storage modules can also be integrated into or excluded from a desired configuration.

[0020] Electromobility is crucial for reducing CO2 emissions in the transport sector. Multilevel technologies, for example, play a significant role in improving the performance and / or efficiency of electric vehicles. The following study illustrates the importance of multilevel approaches and their applications in the field of electromobility. The total emissions of commercially available passenger cars were analyzed, highlighting electromobility as an important strategy for reducing CO2 emissions (see Johannes Buberger, Anton Kersten, Manuel Kuder, Richard Eckerle, Thomas Weyh, Torbjörn Thiringer, “Total CO2-equivalent life-cycle emissions from commercially available passenger cars”, Renewable and Sustainable Energy Reviews, Volume 159, 2022, 112158, ISSN 1364-0321, https: / / www.sciencedirect.com / science / article / pii / S1364032122000867).

[0021] Furthermore, a study demonstrates the efficiency of battery modular multilevel management at the cell level for electric vehicles and energy storage systems (see A. Kersten et al., “Inverter and Battery Drive Cycle Efficiency Comparisons of CHB and MMSP Traction Inverters for Electric Vehicles”, 2019, 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe), Genova, Italy, 2019, pp. P.1 - P.12).

[0022] Another study deals with the modeling and parameter extraction for the evaluation of losses in modular battery systems based on a staged H-bridge multilevel inverter (see M. Kuder, J. Schneider, A. Kersten, T. Thiringer, R. Eckerle and T. Weyh, “Battery Modular Multilevel Management (BM3) Converter applied at Battery Cell Level for Electric Vehicles and Energy Storages”, PCIM Europe digital days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Germany, 2020, pp. 1-8).

[0023] Furthermore, a study addresses the estimation of battery impedance of cells, modules or packs in reconfigurable battery systems or multilevel inverters, thereby utilizing multilevel technologies to generate and effectively use more battery data (see Theliander, A.

[0024] Kersten, M. Kuder, W. Han, EA Grunditz and T. Thiringer, “Battery Modeling and Parameter Extraction for Drive Cycle Loss Evaluation of a Modular Battery System for Vehicles Based on a Cascaded H-Bridge Multilevel Inverter,” in IEEE Transactions on Industry Applications, vol. 56, no. 6, pp. 6968-6977, Nov.-Dec. 2020).

[0025] There are also other studies on impedance estimation, see e.g. A. Kersten et al., “Online and On-Board Battery Impedance Estimation of Battery Cells, Modules or Packs in a Reconfigurable Battery System or Multilevel Inverter”, IECON 2020, The 46th Annual Conference of the IEEE Industrial Electronics Society, Singapore, 2020, pp. 1884-1891.

[0026] These findings underline the relevance of multilevel technologies for electromobility and highlight their potential to increase efficiency and performance in vehicle and energy storage systems.

[0027] Regarding a possible design of a multilevel converter system and / or a method for operating the multilevel converter system, reference is made to DE 10 2022 110 426 A1, the content of which is fully incorporated into this application.

[0028] The energy storage modules, preferably the transistors, are switched in such a way that a welding temperature is provided at the contact.

[0029] For example, a short circuit can be created. The resulting heat can weld the contact together.

[0030] The contacts can be welded together, for example, by arc welding. A shielding gas can be used to facilitate the generation of a plasma.

[0031] Alternatively or additionally, the contacts can be welded by ultrasonic welding.

[0032] The transistors can switch at frequencies up to 1.2 MHz, for example. Rapid switching of the current on and off can generate vibrations at the contacts.

[0033] This allows additional energy to be introduced.

[0034] For example, this method can improve weld quality. A lower current with a high frequency can be used initially to contact a large area. Then, a higher current and lower frequency can be used to create a durable joint.

[0035] It was surprising that the system could virtually weld its own contacts together.

[0036] The contacts can be provided, for example, on the energy storage modules and / or the transistors / switches, i.e., the energy storage modules and / or the transistors / switches, which preferably connect the energy storage modules, can be welded together.

[0037] This significantly reduces the welding effort. Furthermore, a welding robot is not required.

[0038] Further developments of the invention can also be found in the dependent claims, the description and the accompanying drawings.

[0039] According to one embodiment, the welding temperature corresponds to the welding temperature of copper, nickel or aluminium.

[0040] Therefore, materials such as copper, nickel and / or aluminium can be welded together.

[0041] According to another embodiment, the welding temperature is provided for a welding duration between 1 s and 10 s, preferably between 2 s and 3 s.

[0042] Welding is therefore quick.

[0043] The aim is, for example, to keep the current as constant as possible. This can be achieved, for instance, using pulse-width modulation. This can result in a "welding profile." Alternatively or in addition to pulse-width modulation, the current can be adjusted, for example, by varying the switching strength of the transistors / switches. In this case, the transistor can, for example, act as the current source.

[0044] The welding time is preferably sufficient to enable safe and / or permanent welding.

[0045] According to another embodiment, mechanical pressure is applied to the contact during welding.

[0046] For example, a sheet of metal, e.g. made of copper, nickel and / or aluminium material, can be pressed onto the contact.

[0047] Pressure can preferably be applied during the welding process.

[0048] For example, the pressure during welding can be kept constant or varied.

[0049] After welding, the pressure can preferably be released again.

[0050] In another embodiment, when welding several contacts, the contacts are welded at different times.

[0051] It is preferable to weld one contact at a time.

[0052] This makes, for example, the control easier,

[0053] According to another embodiment, when welding multiple contacts, at least two contacts are welded simultaneously. This saves time and therefore costs during the welding process.

[0054] In another embodiment, welding is carried out using a printed circuit board.

[0055] Preferably, the circuit board is arranged outside the energy storage module.

[0056] According to another embodiment, the circuit board creates a short circuit in the energy storage module.

[0057] The short circuit is preferably created directly.

[0058] The current can be precisely adjusted in this way, for example.

[0059] In another embodiment, welding is carried out using power electronics within the energy storage module.

[0060] For example, no direct short circuit is created.

[0061] For example, a current pulse can be generated, for instance via a motor.

[0062] According to another embodiment, a sweat pulse is measured.

[0063] The sweat pulse can preferably be used for monitoring.

[0064] The weld point can, for example, provide information about whether the welding was successful. Alternatively or additionally, an optimal weld point can be determined and / or diagnosed. The optimal weld point can be characterized, for example, by the current and / or voltage. An advantage of this approach is that the current and / or voltage values ​​of the energy storage modules are typically measured anyway. An optimal weld point can exhibit a specific resistance. If this deviates from a target value, the welding process can be repeated.

[0065] The invention also relates to a multilevel converter system. The multilevel converter system according to the invention comprises a plurality of energy storage modules and transistors, wherein each energy storage module can be connected in series and / or parallel to the respective adjacent energy storage module, wherein the multilevel converter system is configured such that the energy storage modules, preferably the transistors, can be switched such that a welding temperature is provided at one contact for welding the at least one contact.

[0066] The descriptions of the method according to the invention are also relevant for the multilevel converter system according to the invention. Accordingly, preferred embodiments are described below.

[0067] In one embodiment of the multilevel converter system according to the invention, adjacent energy storage modules are connected to each other via two current and / or voltage paths, preferably with a transistor assigned to each current and / or voltage path.

[0068] In one embodiment of the multilevel converter system according to the invention, three transistors are provided between two adjacent energy storage modules.

[0069] In one embodiment of the multilevel converter system according to the invention, the transistors are switchable in such a way that a short circuit is generated. In another embodiment of the multilevel converter system according to the invention, the transistors are switchable up to 1.2 MHz, which can generate a vibration at the contacts.

[0070] In one embodiment of the multilevel converter system according to the invention, the transistors are MOSFETs.

[0071] In one embodiment of the multilevel converter system according to the invention, the provided welding temperature corresponds to the welding temperature of copper, nickel and / or aluminium materials.

[0072] In one embodiment of the multilevel converter system according to the invention, the multilevel converter system comprises a printed circuit board arranged outside the energy storage modules, wherein the printed circuit board is configured such that the welding of the at least one contact is carried out by the printed circuit board.

[0073] In one embodiment of the multilevel converter system according to the invention, the energy storage module comprises power electronics, wherein the power electronics are configured such that the welding of the at least one contact is carried out by the power electronics.

[0074] In one embodiment of the multilevel converter system according to the invention, the energy storage module comprises at least or exactly one battery, in particular an accumulator, and / or at least or exactly one capacitor.

[0075] The invention also relates to an electric vehicle, wherein the electric vehicle comprises a multilevel converter system according to the invention.

[0076] The invention also relates to the use of a multilevel converter system, preferably a multilevel converter system according to the invention, for welding at least one contact of at least one energy storage module, preferably for welding at least one contact of at least one energy storage module of an electric vehicle.

[0077] All aspects, embodiments, and features of the invention described herein can be combined with one another, preferably also independently of the specific embodiment in which they are mentioned. Preferably, all process steps of the dependent claims can be combined with each other and with the process of the independent claim.

[0078] It is generally noted that terms like "ein" (a) and "eine" (a / an) do not necessarily mean "exactly one" or "exactly one," although this is also possible. The terms "ein" and "eine" can therefore be understood as "at least one" or "exactly one." The use of the singular preferably includes the possibility of the components being plural, and vice versa.

[0079] It is noted that "vorzugsweise" and "bevorzugt" can be translated as "preferably" in English. A feature introduced by "vorzugsweise" or "bevorzugt" is purely optional, can be omitted, and does not constitute a limitation, for example, of claims.

[0080] The invention is described below by way of example with reference to the drawings. The drawings show:

[0081] Fig. 1 shows an embodiment of a device according to the invention.

[0082] MMC system,

[0083] Fig. 2 shows a partially cutaway perspective view of an embodiment of an MMC system for carrying out a method according to the invention, and Fig. 3 shows a partially cutaway perspective view of a further embodiment of an MMC system for carrying out a method according to the invention.

[0084] Fig. 1 shows a multilevel converter system for welding at least one contact 24 to at least one energy storage module 10, 12, 14, 16.

[0085] Adjacent energy storage modules 10, 12, 14, 16 are each connected to each other via several paths.

[0086] Each path includes a switch designed as a transistor 18.

[0087] The adjacent energy storage modules 10, 12, 14, 16 can thus be connected in series or in parallel. Individual energy storage modules 10, 12, 14, 16 can also be bypassed if necessary, e.g., by closing the upper switch 18, and thus excluded from a configuration.

[0088] The paths can be switched in such a way that a short circuit occurs. Due to the contact resistance, temperatures can develop that cause the contacts to weld together.

[0089] Figure 2 shows an MMC system.

[0090] The energy storage modules 10, 12 each have a negative pole 20 and a positive pole 22 (although the poles can also be reversed).

[0091] Contacts 24 or welding points can be welded together using a printed circuit board 26.

[0092] A direct short circuit can be created via the circuit board 26. During the welding process, pressure is preferably applied mechanically to the contacts 24.

[0093] In Fig. 3, no external circuit board is shown. The power electronics are located within the energy storage modules 10, 12.

[0094] Since a direct short circuit is not possible in this case, a current pulse must be generated, for example by means of a motor.

[0095] Reference symbol list

[0096] 10, 12, 14, 16 Energy storage module

[0097] 18 Transistor 20 Negative terminal

[0098] 22 Positive terminal

[0099] 24 contact, welding point

[0100] 26 circuit board

Claims

Claims 1. Method for welding at least one contact (24) of at least one energy storage module (10, 12, 14, 16), preferably one energy storage module (10, 12, 14, 16) of an electric vehicle, using a multilevel converter system in which a plurality of energy storage modules (10, 12, 14, 16) and transistors (18) are provided, wherein each energy storage module (10, 12, 14, 16) can be connected in parallel and / or in series with the respective adjacent energy storage module (10, 12, 14, 16), and the energy storage modules (10, 12, 14, 16), preferably the transistors (18), are connected such that a welding temperature is provided at the contact (24).

2. Method according to claim 1, characterized in that the welding temperature corresponds to the welding temperature of copper, nickel or aluminium.

3. Method according to claim 1 or 2, characterized in that the welding temperature is provided for a welding duration between 1 s and 10 s, preferably between 2 s and 3 s.

4. Method according to one of the preceding claims, characterized in that mechanical pressure is exerted on the contact (24) during welding.

5. Method according to one of the preceding claims, characterized in that when welding several contacts (24), the contacts (24) are welded at different times.

6. Method according to one of claims 1 to 4, characterized in that when welding several contacts (24), at least two contacts (24) are welded simultaneously.

7. Method according to one of the preceding claims, characterized in that the welding is carried out using a printed circuit board (26).

8. Method according to claim 7, characterized in that the circuit board (26) generates a short circuit in the energy storage module (10, 12, 14, 16).

9. Method according to any one of claims 1 to 6, characterized in that the welding is carried out by means of power electronics within the energy storage module (10, 12, 14, 16).

10. Method according to one of the preceding claims, characterized in that a welding pulse is measured.

11. Multilevel converter system comprising a variety of energy storage modules (10, 12, 14, 16) and transistors wherein each energy storage module (10, 12, 14, 16) can be connected in series and / or parallel to the respective adjacent energy storage module (10, 12, 14, 16), wherein the multilevel converter system is configured such that the energy storage modules (10, 12, 14, 16), preferably the transistors, can be switched such that a welding temperature for welding the at least one contact (24) is provided at a contact (24).

12. Multilevel converter system according to claim 11, characterized in that adjacent energy storage modules (10, 12, 14, 16) are connected to each other via two current and / or voltage paths, wherein preferably a transistor (18) is assigned to each current and / or voltage path.

13. Multilevel converter system according to claim 11 or 12, characterized in that three transistors are provided between two adjacent energy storage modules (10, 12, 14, 16).

14. Electric vehicle, characterized in that the electric vehicle comprises a multilevel converter system according to one of the preceding claims 11-13.

15. Use of a multilevel converter system, preferably according to one of the preceding claims 11-13, for welding at least one contact (24) of at least one energy storage module (10, 12, 14, 16), preferably for welding at least one contact (24) of at least one energy storage module (10, 12, 14, 16) of an electric vehicle.

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