Battery with a plurality of battery modules and a method for generating a stepwise adjustable battery voltage

Abstract

Battery with a plurality of battery modules (50, 60) arranged in a battery module string, each module comprising several battery cells (23), a first battery module terminal (31), a second battery module terminal (32), and a coupling circuit (51) having several switches (61, 62, 63, 64), wherein each battery module (50, 60) can be selectively connected to the battery module string by controlling one or more switches (61, 62, 63, 64) of its respective coupling circuit (51), so that it is connected in series in the battery module string via its battery module terminals (31, 32), or can be decoupled from the battery module string so that it is conductively bridged via its battery module terminals (31, 32), wherein at least one of the battery modules (50, 60) is a multi-stage battery module (50, 60) with a coupling circuit (51) is designed to switch to a fraction of the full battery module voltage,characterized in that the battery module string consists of a mixture of battery modules (60) of a first subset, a second subset and a third subset, wherein the subsets have different coupling circuits, wherein the first subset comprises a battery module (60) with a coupling circuit (51) which is configured according to a multilevel converter topology, in particular a diode-clamped multilevel converter topology, wherein the second subset comprises a battery module with a coupling circuit which is configured as a half-bridge and wherein the third subset comprises a battery module with a coupling circuit which is configured as a full-bridge.

Description

[0001] The present invention relates to a battery with a plurality of battery modules arranged in a battery module string, each module comprising several battery cells, a first battery module terminal, a second battery module terminal, and a coupling circuit with several switches. In particular, the invention relates to a battery in which each battery module can be selectively connected to the battery module string by controlling one or more switches of its respective coupling circuit, so that it is connected in series with the battery module string via its battery module terminals, or can be decoupled from the battery module string so that it is conductively bridged via its battery module terminals. The invention also relates to a corresponding method for generating a stepwise adjustable battery voltage. State of the art

[0002] It is becoming clear that battery systems will be increasingly used in the future, both in stationary applications and in vehicles such as hybrid and electric vehicles. To meet the voltage and available power requirements of a given application, a large number of battery cells are connected in series. Since the current supplied by such a battery must flow through all battery cells, and each battery cell can only conduct a limited current, additional battery cells are often connected in parallel to increase the maximum current.

[0003] The basic circuit diagram of a typical electric drive system, as used, for example, in electric and hybrid vehicles or in stationary applications such as the rotor blade adjustment of wind turbines, is shown in Fig. Figure 1 shows a battery 10 connected to a DC link formed by a capacitor 11. A pulse inverter 12 is connected to the DC link and provides phase-shifted sinusoidal voltages for operating an electric drive motor 13 via two switchable semiconductor valves and two diodes at three outputs.

[0004] Batteries are known from previous patent applications of the applicant in which the battery modules are modified and have a coupling circuit with which the battery modules can be selectively connected to or disconnected from the battery module string, as for example in DE 10 2010 064 311 A1. Fig. Figure 2 shows an example of such a coupling circuit of a battery module, which is designed as a half-bridge. The battery cells 23 can be connected to or disconnected from the outputs of the battery module by means of the different switch positions of switches 21 and 22.

[0005] EP 2 650 999 A2 discloses a battery module string in which battery modules with two battery cells and 3-stage coupling circuits are provided. JP 2000-341 964 A and JP 2009-17 622 A disclose topologies for inverter circuits.

[0006] In the Fig. Figure 3 shows an alternative embodiment of the coupling circuit, designed as a full bridge, which connects a series connection of battery cells 23 to a first battery module terminal 31 and a second battery module terminal 32. The coupling circuit has four switches 33 to 36, of which one pair of switches 33, 34 can couple a first battery module terminal 31 to either the negative or the positive output of the series connection of battery cells 23, depending on the switch position, while another pair of switches 35, 36 can couple the second battery module terminal conversely to the remaining positive or negative output, respectively. When all switches 33 to 36 are opened, the battery module is decoupled from a battery module string at both ends.

[0007] Typically, several such battery modules are connected in series. The modular design of batteries allows for adjustable output voltages to be achieved through the use of switched battery modules with half-bridges and / or full bridges. In the Fig. Figure 4 shows a battery 40 in which the battery cells 23 are arranged in battery modules 41, each of which has a coupling circuit according to Fig. 2.

[0008] Further developing a modular battery, whose battery modules are equipped with coupling circuits, into a battery direct inverter with several modular battery strings makes it possible to generate several phase-shifted alternating voltages even without an additional inverter circuit, for example to supply a three-phase electric motor.

[0009] However, the discretization of the battery voltage depends on the level of the battery module voltage. On the one hand, it is desirable to keep the discretization levels as small as possible; on the other hand, small battery module voltages for a given maximum battery voltage also mean a higher number of battery modules, which is associated with correspondingly higher costs, for example, regarding communication, cooling, connector arrangement, etc. Disclosure of the invention

[0010] According to the invention, a battery is provided with a plurality of battery modules arranged in a battery module string according to claim 1.

[0011] Furthermore, a method for generating a stepwise adjustable battery voltage according to claim 7 is provided.

[0012] An advantage of the invention is that it enables finer adjustment of the battery voltage or smaller discretization levels. A single battery module modified according to the invention, with appropriate control, allows for the discretization of the entire battery voltage. The battery modules are equipped with conventional coupling circuits according to the Fig. 2 and Fig. 3 and battery modules according to the invention are mixed together. In the invention, at least one battery module in a battery module string is designed as a multi-stage battery module according to the invention.

[0013] According to one embodiment of the invention, the coupling circuits of the multi-stage battery modules each comprise a first output coupled to the first battery module terminal, a second output coupled to the second battery module terminal, and three or more inputs. The multi-stage battery modules each have a number of battery cells arranged in series, with each input of a coupling circuit being connected to a different battery cell terminal or pair of battery cell terminals such that the number of battery cells arranged in series forms an even distribution into several subsets of battery cells, each connected between a different pair of inputs.

[0014] In a particularly advantageous embodiment of the invention, the coupling circuits of the multi-stage battery modules are each configured to selectively connect one or more of the fractions of the respective series-arranged battery cells between the first battery module terminal and the second battery module terminal by controlling their respective switches, and to decouple the remaining battery cells of the series-connected battery cells from the first battery module terminal and / or the second battery module terminal.

[0015] This results in particularly high flexibility, especially when each battery cell group or subset of battery cells can be addressed separately, and ensures a uniform discharge or charge of all battery cells in a simple manner. This is preferably monitored by a suitable battery monitoring unit or control circuit.

[0016] According to another advantageous embodiment of the invention, at least one of the coupling circuits is configured to selectively connect at least one of the battery cell subsets with either positive or negative polarity between the first battery module terminal and the second battery module terminal. This allows for the generation of a higher amplitude of the adjustable battery output voltage, or an amplitude increased up to twice the voltage.

[0017] Coupling circuits are arranged according to a multilevel converter topology. A diode-clamped multilevel converter topology is particularly preferred.

[0018] One advantage of this is that it allows for particularly robust voltage generation in the battery modules. The diodes also prevent unwanted current flows, especially in cases of incorrect polarity.

[0019] According to a particularly simple embodiment of the invention, at least one of the coupling circuits has a topology similar to that of a three-stage converter. The coupling circuit comprises a series connection of four switches, the first two of which are connected in parallel to the respective series connection of battery cells, and the last two of which are connected in series to the series connection of battery cells between the first battery module terminal and the second battery module terminal.Furthermore, in this embodiment, the coupling circuit comprises a first diode, the cathode of which is connected to a terminal arranged between the first two switches and the anode of which is connected to a central input of the coupling circuit, and a second diode, the anode of which is connected to a terminal arranged between the last two switches and the cathode of which is connected to the central input of the coupling circuit.

[0020] This provides a particularly simple way to create a three-stage battery module that can be switched to half the battery module voltage using an intermediate stage.

[0021] In an advantageous further development of the battery, several battery strings are provided within the battery, for example three battery strings that can be connected to the terminals of a three-phase electric motor. Each of the battery module strings has at least one multi-stage battery module according to the invention.

[0022] In a further development of the inventive method, the battery is operated as a battery direct inverter, so that the battery strings generate alternating voltages that are phase-shifted relative to each other and have voltage levels whose precision is adjusted by appropriate control of the multi-stage battery modules.

[0023] The battery according to the invention is preferably a lithium-ion battery.

[0024] According to the invention, a motor vehicle, in particular an electric or hybrid vehicle, is also provided which has the battery according to the invention, wherein the battery is connected to a drive system of the motor vehicle.

[0025] Advantageous embodiments of the invention are specified in the dependent claims and described in the description. Drawings

[0026] Exemplary embodiments of the invention are explained in more detail with reference to the drawings and the following description. The drawings show: Fig. 1. A schematic diagram of a typical electric drive system with a state-of-the-art battery connected to a DC link. Fig. 2 a coupling circuit for a battery module according to the state of the art, which is designed as a half-bridge, Fig. 3 a coupling circuit for a battery module according to the state of the art, which is designed as a full bridge, Fig. 4 a battery with a battery module string of connectable battery modules according to the state of the art, Fig. 5 a schematic diagram of a battery module in which a coupling circuit is arranged between the battery cells and the battery module terminals, according to a first embodiment of the invention, and Fig. 6 a schematic diagram of a battery module in which a coupling circuit is arranged between the battery cells and the battery module terminals, wherein the coupling circuit has a three-stage converter topology, according to a second embodiment of the invention. Embodiments of the invention

[0027] In the Fig. Figure 5 shows a schematic diagram of a battery module 50 according to a first embodiment of the invention, in which a coupling circuit 51 is arranged between the battery cells 23 and the battery module terminals 31, 32. The coupling circuit 51 is configured such that the battery module 50 forms a multi-stage battery module that has a battery module voltage that can be switched to a fraction of the full battery module voltage. The coupling circuit 51 has switches (not shown) and preferably also diodes (not shown) with which either a subset of the battery cells 23, all battery cells 23, or no battery cells 23 can be addressed. As shown in the Fig. As shown in Figure 5, the total number of battery cells 23 is divided into groups by contacting inputs 52 of the coupling circuit 51. Each input 52 of the coupling circuit 51 is connected to a different battery cell terminal 55, or, in the case of the middle inputs, to different battery cell terminals 55 in the battery module 50. By controlling the coupling circuit 51, either one, several, or all groups or subsets of battery cells are addressed, depending on the required battery voltage increment. For this purpose, the control circuit (not shown) of the coupling circuit 51 is clocked sufficiently quickly. This allows a smaller step size for the battery output voltage to be set than would correspond to a full battery module voltage, at which all battery cells 23 are switched on.The battery module may also contain other components, such as a cooling system or a voltage sensor, which are not shown in the drawing for the sake of clarity.

[0028] In the Fig. Figure 6 shows a schematic diagram of a battery module 60 according to a second embodiment of the invention, in which a coupling circuit is arranged between the battery cells and the battery module terminals. According to the Fig. In the exemplary embodiment shown in Figure 6, the coupling circuit has a three-stage converter topology. This provides a simple yet robust implementation of the coupling unit according to the invention with three battery module voltage stages. According to the three-stage converter topology shown, the coupling unit of the battery module 60 has a series connection of four switches 61, 62, 63, 64, the first two switches 61, 62 of which are connected in series with the respective series connection of battery cells, and the last two switches 63, 64 of which are connected in parallel with the series connection of battery cells 23 between the first battery module terminal 31 and the second battery module terminal 32.

[0029] Furthermore, the coupling circuit includes according to Fig. 6 a first diode 65, whose cathode is connected to a terminal arranged between the first two switches 61, 62 and whose anode is connected to a middle input of the coupling circuit 51, and a second diode 66, whose anode is connected to a terminal arranged between the last two switches 63, 64 and whose cathode is connected to the middle input of the coupling circuit 51.

[0030] By closing switches 63 and 64, the battery cells 23 can be conductively bridged via the battery module terminals 31 and 32, so that the battery module currently supplies no voltage. By opening switches 63 and 64 and closing switches 61 and 62, all battery modules 23 are switched on. By opening switches 61 and 64 and closing switch 62, the battery module is switched such that it nominally supplies half the battery module voltage.

[0031] A person skilled in the art recognizes that the invention does not relate to the invention as described above. Fig. The multilevel converter topology discussed in section 6 is limited. Instead, another suitable circuit within a battery module can be chosen that fulfills the same purpose. For example, the... Fig. 5 and Fig. Figure 6 serves only to illustrate the principle of the invention. In a battery in which the invention is used, at least one of the multi-stage battery modules is employed per battery string, resulting, in conjunction with the corresponding control sequence, in a refined gradation of the battery voltage for each voltage level. To further refine the discretization, other embodiments of the invention feature battery modules with more complex coupling circuits, such as fifth-order or higher multi-level converter structures.

Claims

[1] Battery with a plurality of battery modules (50, 60) arranged in a battery module string, each module comprising several battery cells (23), a first battery module terminal (31), a second battery module terminal (32) and a coupling circuit (51) having several switches (61, 62, 63, 64), wherein each battery module (50, 60) can be selectively connected to the battery module string by actuating one or more switches (61, 62, 63, 64) of its respective coupling circuit (51), so that it is connected in series in the battery module string via its battery module terminals (31, 32) or can be decoupled from the battery module string so that it is conductively bridged via its battery module terminals (31, 32), wherein at least one of the battery modules (50, 60) is a multi-stage battery module (50, 60) with a coupling circuit (51) is designed to switch to a fraction of the full battery module voltage,characterized by , that the battery module string consists of a mixture of battery modules (60) of a first subset, a second subset and a third subset, wherein the subsets have different coupling circuits, wherein the first subset comprises a battery module (60) with a coupling circuit (51) which is configured according to a multilevel converter topology, in particular a diode-clamped multilevel converter topology, wherein the second subset comprises a battery module with a coupling circuit which is configured as a half-bridge and wherein the third subset comprises a battery module with a coupling circuit which is configured as a full-bridge. [2] Battery according to claim 1, wherein the coupling circuits (51) of the multi-stage battery modules (50, 60) each comprise a first output (53) coupled to the first battery module terminal (31), a second output (54) coupled to the second battery module terminal (32), and three or more inputs (52), and wherein the multi-stage battery modules (50, 60) each comprise a number of battery cells (23) arranged in series, wherein each input (52) of a coupling circuit (51) is connected to a different battery cell terminal (55) or pair of battery cell terminals (55) such that the number of battery cells (23) arranged in series forms an even distribution into several subsets of battery cells (23) connected between different pairs of inputs (52). [3] Battery according to claim 1 or 2, wherein the coupling circuits (51) of the multi-stage battery modules (50, 60) are each configured to selectively connect one or more of the fractions of the respective series-arranged battery cells (23) between the first battery module terminal (31) and the second battery module terminal (32) by controlling their respective switches (61, 62, 63, 64) and to decouple the remaining battery cells (23) of the series-connected battery cells (23) from the first battery module terminal (31) and / or the second battery module terminal (32). [4] Battery according to claim 3, wherein at least one of the coupling circuits (51) is further configured to connect at least one of the subsets of the battery cells (23) selectively with positive polarity or negative polarity between the first battery module terminal (31) and the second battery module terminal (32). [5] Battery according to any one of the preceding claims 1 to 4, wherein at least one of the coupling circuits (51) comprises a series connection of four switches (61, 62, 63, 64), the first two switches (61, 62) of which are connected in series with the series connection of battery cells (23) and the last two switches (63, 64) of which are connected in parallel with the series connection of battery cells (23) between the first battery module terminal (31) and the second battery module terminal (32), and wherein the at least one of the coupling circuits (51) further comprises, for the implementation of a three-stage converter topology, a first diode (65) of which the cathode is connected to a terminal arranged between the first two switches (61, 62) and whose anode is connected to a central input of the coupling circuit (51), and a second diode (66) of which the anode is connected to a terminal arranged between the last two switches (63,64) is connected to the terminal arranged and its cathode is connected to the central input of the coupling circuit (51). [6] Battery according to one of the preceding claims, wherein the battery has several battery strings, for example three battery strings, which can be connected to the terminals of a three-phase electric motor, wherein each battery module string has one or more multi-stage battery modules (50, 60). [7] A method for generating a stepwise adjustable battery voltage, in which a battery is used which has a plurality of battery modules (50, 60) arranged in a battery module string, each of which comprises several battery cells (23), a first battery module terminal (31), a second battery module terminal (32), and a coupling circuit (51) having several switches (61, 62, 63, 64), wherein each battery module (50, 60) can be selectively connected to the battery module string by actuating one or more switches (61, 62, 63, 64) of the respective coupling circuit (51), so that it is connected in series in the battery module string via its battery module terminals (31, 32), or can be decoupled from the battery module string so that it is conductively bridged via its battery module terminals (31, 32), wherein at least one is a multi-stage battery module (50, 60) designed battery module (50, 60) is controlled for this purpose,to supply an output voltage that corresponds to a fraction of the full battery module voltage of the multi-stage battery module (50, 60), , characterized by , that the battery module string consists of a mixture of battery modules (60) of a first subset, a second subset and a third subset, wherein the subsets have different coupling circuits, wherein the first subset comprises a battery module (60) with a coupling circuit (51) which is configured according to a multilevel converter topology, in particular a diode-clamped multilevel converter topology, wherein the second subset comprises a battery module with a coupling circuit which is configured as a half-bridge and wherein the third subset comprises a battery module with a coupling circuit which is configured as a full-bridge. [8] Method according to claim 7, which is carried out with a battery with multiple battery strings according to claim 6, wherein the battery is operated as a battery direct inverter, so that the battery strings generate alternating voltages that are phase-shifted relative to each other and have voltage levels, the fineness of which is adjusted by a corresponding control of the multi-stage battery modules (50, 60). [9] Motor vehicle, in particular electric or hybrid vehicle, comprising a battery according to any one of claims 1 to 6, wherein the battery is connected to a drive system of the motor vehicle.

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