HV battery system and HV system arrangement for an electrically driven vehicle

Abstract

The invention relates to an HV battery system (1) for an electrically driven vehicle, having a battery (3) with a plurality of battery modules (4) which each have at least one battery cell, wherein each battery module (4) is coupled to a primary side (6) of its own galvanically isolated DC-DC converter (5). According to the invention, the battery (3) can be coupled or is coupled to first output connections (A1+, A1-) via switching elements (S1, S2), wherein at least one of the switching elements (S1, S2) is a galvanically isolating switching element (S1, S2). In addition, according to the invention, an electrical series circuit of secondary sides (7) of the DC-DC converters (5) is coupled to second output connections (A2+, A2-). The invention also relates to an HV system arrangement (2) for an electrically driven vehicle.

Description

[0001] HV battery system and HV system arrangement for an electrically powered vehicle

[0002] The invention relates to an HV battery system for an electrically powered vehicle according to the features of the preamble of claim 1 and an HV system arrangement for an electrically powered vehicle.

[0003] From the prior art, as described in DE 10 2016 010 990 A1, a method and a circuit arrangement for a motor vehicle for supplying a consumer by means of an HV storage arrangement are known. The circuit arrangement comprises the consumer and the HV storage arrangement, which has a plurality of cell groups, each of the cell groups comprising at least one battery cell. The circuit arrangement has a plurality of converter devices. Each of the cell groups is assigned to one of the converter devices. The circuit arrangement is designed such that the cell groups can be coupled to and decoupled from the consumer for supplying energy independently of one another via the assigned converter device. Furthermore, the consumer represents at least one battery-integrated component of an HV battery having the HV storage arrangement.

[0004] DE 102019210793 A1 describes an electrical energy storage system and a method for operating it. The electrical energy storage system comprises a plurality of electrochemical energy storage devices that can be electrically connected to first terminals of the electrical energy storage system by means of first switches for providing a first electrical voltage, at least one second terminal for providing a second electrical voltage, at least one sensor for detecting a voltage variable representing an electrical voltage of one or more electrochemical energy storage devices and / or a temperature variable representing a temperature of one or more electrochemical energy storage devices, and at least one second switch that is electrically connected to at least one of the electrochemical energy storage devices.By means of the second switch, one pole of the at least one electrochemical energy storage device can be electrically connected to the second connection pole for providing the second electrical voltage, which is equal to or lower than the first electrical voltage, depending on the detected voltage variable and / or temperature variable.

[0005] DE 102011 075 091 A1 discloses an electrochemical energy storage device for a vehicle and a use of an electrochemical energy storage device for a vehicle. The electrochemical energy storage device comprises a battery housing and a battery cell arrangement accommodated therein for providing a battery voltage to a pair of battery terminals arranged on the outside of the battery housing and electrically connected to the battery cell arrangement. Furthermore, at least one DC / DC converter electrically connected to the battery cell arrangement is accommodated in the battery housing for providing at least one additional voltage to a pair of battery terminals arranged on the outside of the battery housing.

[0006] DE 102015 120285 A1 describes a battery, a vehicle with such a battery, and a use of such a battery. The battery has a first battery terminal and a second battery terminal, wherein, when the battery is charged, a first nominal voltage can be tapped between the second and first battery terminals. The battery has a third battery terminal, wherein, when the battery is charged, a second nominal voltage can be tapped between the third and first battery terminals, which differs in magnitude from the first nominal voltage.

[0007] DE 102017218252 A1 discloses an energy storage arrangement for a motor vehicle, comprising a plurality of cell units with at least one battery cell and a respective converter device. The converter devices can be connected in parallel on the output side and are designed to convert a first voltage of the cell unit into a second voltage. The energy storage arrangement has a first supply path and a second supply path, wherein the converter devices can be coupled independently of one another to the first supply path and / or the second supply path via a switching device.

[0008] The invention is based on the object of providing an HV battery system for an electrically powered vehicle that is improved compared to the prior art and an HV system arrangement for an electrically powered vehicle that is improved compared to the prior art.

[0009] The object is achieved according to the invention by an HV battery system for an electrically powered vehicle having the features of claim 1 and an HV system arrangement for an electrically powered vehicle having the features of claim 8.

[0010] Advantageous embodiments of the invention are the subject of the subclaims.

[0011] An HV (high-voltage) battery system for an electrically powered vehicle comprises a battery with a plurality of battery modules, each of which has at least one battery cell, in particular a plurality of battery cells. Each battery module is coupled to a primary side of its own galvanically isolated DC / DC converter. DC / DC converters are also referred to as DC / DC converters.

[0012] According to the invention, the battery is or can be coupled to first output terminals via switching elements, wherein at least one of the switching elements is a galvanically isolating switching element, in particular a contactor. For example, both switching elements are galvanically isolating switching elements, or one of the switching elements is a semiconductor switch.

[0013] In addition, according to the invention, an electrical series circuit of secondary sides of the DC-DC converters is coupled to second output terminals.

[0014] An inventive HV system arrangement for an electrically powered vehicle comprises the HV battery system, a first HV system coupled to the first output terminals of the HV battery system, and a second HV system coupled to the second output terminals of the HV battery system. The respective HV system is, for example, an HV on-board electrical system or HV sub-on-board electrical system of the vehicle.

[0015] In particular, it is provided that the battery modules are electrically connected in series. In one embodiment, the DC-DC converters are each designed such that they transfer a voltage of the battery module to which they are coupled to the secondary side at a fixed ratio.

[0016] The respective DC-DC converter is designed, for example, as a unidirectional or bidirectional DC-DC converter. This depends, for example, on the specific application.

[0017] In one embodiment, the battery cells and the DC-DC converters are thermally coupled with a common cooling device. This is advantageous because both the battery cells and the DC-DC converters require cooling, so this cooling can be shared. However, it is not absolutely necessary for the functioning of the battery system.

[0018] In one embodiment, a fuse is arranged between the battery and one of the first output terminals.

[0019] In particular, it is provided that all components of the second HV system are designed to operate with a standardized supply voltage, in particular standard voltage.

[0020] In particular, it is provided that each component of the second HV system has a lower power consumption than each component of the first HV system.

[0021] In the described solution, the first HV system can be supplied with a battery voltage via the switching elements and the first output terminals of the HV battery system, i.e., in particular, with a sum voltage of the battery modules, which are electrically connected in series, and the second HV system can be supplied with an adapted voltage of the DC-DC converters, whose secondary sides are electrically connected in series, via the second output terminals of the HV battery system. This supply to the second HV system is independent of the switching position of the switching elements.

[0022] This solution makes it possible, in particular, to provide an HV connection to the HV battery system independent of the battery voltage via the DC-DC converters, which can be designed to be smaller and less powerful for this purpose, namely at the second output terminals. This can be used, for example, to provide certain required voltages and / or as a safety system and / or redundant system and / or for balancing, i.e., in particular, voltage equalization, of the voltage of the battery cells and / or battery modules.

[0023] By connecting the secondary sides of the DC-DC converters in series, it is possible to provide higher voltages, especially HV voltages, at the second output terminals and, for example, to convert a lower battery voltage into a higher standard voltage to supply the second HV system, especially the components in the second HV system. This achieves a very high level of flexibility. Furthermore, the described solution achieves very high voltage stability at the second output terminals, since the DC-DC converters can implement this in a specific application.

[0024] The DC-DC converters are designed as galvanically isolated DC-DC converters, also referred to as isolated DC-DC converters, in particular for safety reasons, because it is particularly provided that no galvanically isolating switching elements are provided between the battery and the primary sides of the DC-DC converters and between the secondary sides of the DC-DC converters, in particular the electrical series connection of the secondary sides of the DC-DC converters, and the second output terminals.

[0025] The first output terminals of the battery system supply the total battery voltage to high-performance functions / components, i.e., these high-performance functions / components are located in the first HV system. Such high-performance functions / components include, for example, one or more inverters, particularly for one or more electric motors for driving the vehicle, and / or a DC charging function (DC charging = charging the battery from a DC energy source external to the vehicle, e.g., a DC charging column / DC charging station).

[0026] The second HV system is supplied via the second output terminals of the battery system and thus via the DC-DC converters, whose secondary sides are electrically connected in series. A uniform voltage level can be generated in this second HV system through voltage-dependent activation / deactivation of the DC-DC converters. The respective DC-DC converter is advantageously designed to transfer the voltage of the battery module to which it is coupled to the secondary side at a fixed ratio of, for example, 1:1. This allows technologies for increasing efficiency, such as resonant switching, to be implemented in an optimized manner for this transformation ratio. Fluctuations in the voltage of the battery module on the primary side of the DC-DC converter are thus transferred to the secondary side and thus to the second output terminals of the battery system.

[0027] The described solution makes it possible to standardize the components in the second HV system, especially with regard to their supply voltage.

[0028] The described solution significantly limits the operating voltage range of the components in the second HV system. This enables a cost-effective and efficiency-optimized design of these components.

[0029] The solution described enables the balancing of the battery cells and / or battery modules.

[0030] The solution described enables a so-called limp-home function in the vehicle. In the event of a high-resistance defect in a battery module, the vehicle can continue driving at a reduced current.

[0031] The described solution enables EMC attenuation during DC charging. The components in the second HV system are attenuated by the filtering effect of the DC-DC converters. EMC filters for these components can thus be designed smaller.

[0032] The described solution achieves a reduction in the visible, i.e., particularly the Y-capacitances that must be taken into account, during DC charging. Due to the galvanic isolation of the DC-DC converters, all Y-capacitances of the components located in the second HV system have no impact on a DC connection circuit for DC charging.

[0033] The described solution enables the use of DC-DC converters for AC charging (AC charging = charging the battery from an AC power source external to the vehicle, such as a building services connection or AC charging station). To implement the galvanically isolated AC charging function, only a PFC (power factor correction filter) is required, meaning the required size of an on-board charger for AC charging is significantly reduced.

[0034] Embodiments of the invention are explained in more detail below with reference to drawings.

[0035] Showing:

[0036] Fig. 1 schematically shows a battery module with a galvanically isolated DC-DC converter,

[0037] Fig. 2 shows a schematic example of a galvanically isolated DC-DC converter,

[0038] Fig. 3 shows schematically an example of a HV system arrangement,

[0039] Fig. 4 schematically shows a battery module with a galvanically isolated

[0040] DC-DC converter as well as currents and an output voltage of the DC-DC converter,

[0041] Fig. 5 shows schematically a DC-DC converter which is inactive for positive currents on the secondary side,

[0042] Fig. 6 shows schematically a DC-DC converter which is inactive for negative currents on the secondary side,

[0043] Fig. 7 shows a schematic diagram of a HV battery system with a battery with four battery modules and active DC-DC converters,

[0044] Fig. 8 shows a schematic diagram of an HV battery system with a battery with five battery modules and only four active DC-DC converters, Fig. 9 shows a schematic diagram of another HV battery system with a battery with five battery modules and only four active DC-DC converters,

[0045] Fig. 10 shows a schematic diagram of an HV battery system in which the input voltage is very low and all DC-DC converters are active,

[0046] Fig. 11 shows a schematic diagram of an HV battery system in which the input voltage is medium and one of the DC-DC converters is not active,

[0047] Fig. 12 shows a schematic diagram of an HV battery system in which the input voltage is high and two of the DC-DC converters are not active,

[0048] Fig. 13 schematically shows an example of an HV system arrangement for realizing an AC charging function,

[0049] Fig. 14 schematically shows another example of a HV system arrangement,

[0050] Fig. 15 schematically shows an HV battery system with a high-resistance battery module or with an interruption, and

[0051] Fig. 16 schematically shows a DC-DC converter connected to bridge the high-resistance battery module or the interruption in the HV battery system according to Figure 15.

[0052] Corresponding parts are provided with the same reference numerals in all figures.

[0053] In the following, an HV battery system 1 for an electrically powered vehicle, an HV system arrangement 2 comprising this HV battery system 1 for an electrically powered vehicle and possible uses and / or modes of operation of the HV battery system 1 and the HV system arrangement 2, ie in particular embodiments of methods for operating the HV battery system 1 and the HV system arrangement 2, are described with reference to Figures 1 to 16.

[0054] The solution described here is based on the following challenges: The aim is to achieve independence of HV components from HV battery variance. It can be assumed that a greater variety of electrically powered vehicles in a vehicle fleet will lead to the development of a large number of different batteries 3. The differences arise from different voltage levels, for example from a different number of battery cells connected in series, from a variation in cell types, in particular with differences in cell chemistry, and / or from the aging of some battery cells during vehicle operation. For example, two to three different batteries 3 with different characteristics are offered for each vehicle series. These batteries differ, for example, in cell number, cell chemistry and thus characteristic curve and / or internal resistance.In a model update of the vehicle series, for example, the batteries 3 are also updated.

[0055] One possible goal of the solution described here is to avoid adapting the HV components to the differences in the batteries 3 in the interest of a uniform design of the HV components. For components such as a drive or a DC charging function, the power varies with the performance of the battery 3. This can be an argument for selecting a larger battery 3. For components, especially HV components with transformers, such as an AC on-board charger or an LV DC / DC converter (LV = low voltage), a variation in the voltage level leads to adaptation development or oversizing of the components. This can be avoided using the solution described here.

[0056] Further challenges include the fact that a single battery cell failure currently leads to the entire battery failure, resulting in the vehicle breaking down. This can be avoided using the solution described here.

[0057] A further challenge is EMC filtering of HV components that are active during DC charging (EMC = electromagnetic compatibility). Until now, HV components have been designed for high voltage ripple requirements, usually caused by an inverter. The solution described here advantageously eliminates such a design requirement.

[0058] Further challenges include observing a maximum permissible Y-capacitance during DC charging and driving, and reducing the dimensions of the HV components. Figure 1 shows a schematic representation of a battery module 4 with a galvanically isolated DC-DC converter 5, also referred to as an isolating DC-DC converter 5. The battery module 4 consists of at least one battery cell, advantageously several battery cells, for example, twelve or thirteen battery cells. The DC-DC converter 5 has a primary side 6 and a secondary side 7. The primary side 6 is coupled to the battery module 4.

[0059] Figure 2 shows a schematic representation of an example of such a galvanically isolated DC-DC converter 5. The illustrated topology of the DC-DC converter 5 is only an example.

[0060] Battery module 4 has a positive module terminal M+ and a negative module terminal M-. A voltage from battery module 4 can be tapped via these two module terminals M+ and M-. Furthermore, the battery cells of module 4 can be charged and discharged via these module terminals M+ and M- with a current, particularly a relatively high current. The maximum current is limited by a power busbar, a connection technology, and / or the battery cells of battery module 4.

[0061] Parallel to the module terminals M+, M- of the positive and negative poles of the battery module 4, there is another voltage tap for the battery module 4. This voltage tap supplies the galvanically isolated DC-DC converter 5, i.e., its primary side 6. The current through these taps is determined by the design of the DC-DC converter 5 and by the design of the busbars, the connection technology, and / or the battery cells.

[0062] On the secondary side 7 of the DC-DC converter 5 there are converter terminals W+, W-.

[0063] The DC-DC converter 5 is advantageously designed to transfer the voltage of the battery module 4 to the secondary side 7 at a fixed ratio of, for example, 1:1. Thus, technologies for increasing efficiency, such as resonant switching, can be implemented in an optimized manner for this transmission ratio. Fluctuations in the voltage of the battery module 4 are thus transferred to the secondary side 7 and thus to the converter terminals W+, W-. The DC-DC converter 5 can be designed unidirectionally or bidirectionally, particularly depending on the intended use. Since both the battery cells and the DC-DC converter 5 require cooling, this cooling can be shared. However, it is not absolutely necessary for the function.

[0064] Figure 3 shows a schematic representation of the HV system arrangement 2. The HV system arrangement 2 comprises the HV battery system 1, a first HV system HVS1, and a second HV system HVS2. In the example shown, the HV battery system 1 has four battery modules 4 and DC-DC converters 5 assigned to them, i.e., each battery module 4 is assigned its own galvanically isolated DC-DC converter 5 in the manner described above for Figure 1. The number of battery modules 4 and DC-DC converters 5 can be higher or lower in other exemplary embodiments. Furthermore, the number of battery cells per battery module 4 can also be freely selected.

[0065] The HV battery system 1 thus comprises the battery 3 with a plurality of battery modules 4, each of which has at least one battery cell, in particular a plurality of battery cells electrically interconnected. The battery modules 4 are electrically connected in series. Each battery module 4 is coupled to the primary side 6 of its own galvanically isolated DC-DC converter 5.

[0066] The HV battery system 1 has first output terminals A1+, A1- and second output terminals A2+, A2-.

[0067] The battery 3 is or can be coupled to the first output terminals A1+, A1- via switching elements S1, S2. At least one of the switching elements S1, S2 is a galvanically isolating switching element S1, S2, in particular a contactor. In the example shown, both switching elements S1, S2 are designed as such a galvanically isolating switching element S1, S2, in particular a contactor. In other examples, one of the switching elements S2, S1 can be a semiconductor switch.

[0068] The secondary sides 7 of the DC-DC converters 5 are electrically connected in series. This electrical series connection of the secondary sides 7 of the DC-DC converters 5 is coupled to the second output terminals A2+, A2-. The first HV system HVS1 is coupled to the first output terminals A1+, A1- of the HV battery system 1. The second HV system HVS2 is coupled to the second output terminals A2+, A2- of the HV battery system 1.

[0069] The DC-DC converters 5 are each designed, for example, such that they transmit a voltage of the battery module 4, to which they are coupled, to the secondary side 7 in a fixed ratio.

[0070] The respective DC-DC converter 5 is designed as a unidirectional or bidirectional DC-DC converter 5, in particular depending on a respective intended use.

[0071] The battery cells and the DC-DC converters 5 can be thermally coupled with a common cooling device.

[0072] In particular, it is provided that a fuse 8 is arranged between the battery 3 and one of the first output terminals A1+, A1-, in the example shown between the battery 3 and the positive first output terminal A1+.

[0073] In particular, it is intended that all components of the second HV system HVS2 are designed to operate with a standardized supply voltage, in particular standard voltage.

[0074] In particular, it is provided that each component of the second HV system HVS2 has a lower power consumption than each component of the first HV system HVS1.

[0075] Due to the illustrated and described design, in particular due to the electrical series connection of the secondary sides 7 of the DC-DC converters 5, an output is created at the second output terminals A2+, A2- which has the sum voltage of all DC-DC converters 5. The second HV system HVS2 is connected to these second output terminals A2+, A2-. It consists of components which are operated with a standardized supply voltage if possible. Since the second HV system HVS2 is supplied via the series connection of the secondary sides 7 of the DC-DC converters 5, it is advantageous to only locate consumers, i.e. only components, in the second HV system HVS2 which require lower power consumption. This also allows the galvanically isolated DC-DC converters 5 to be kept small in their dimensions.Examples of such components are auxiliary consumers, such as air conditioning components, LV-DCDC converters, but also the function of the galvanically isolated AC on-board charger.

[0076] Since the DC-DC converters 5 are to be regarded as components of the battery modules 4, the connection via the second output connections A2+, A2-, i.e. the connection for the second HV system HVS2, has galvanic isolation. Therefore, no further switch is required between the battery modules 4 and the secondary side 7 of the DC-DC converters 5. By deactivating / activating the individual DC-DC converters 5 on the primary side 6, e.g. by interrupting the clocking of the semiconductors of the DC-DC converter 5, the supply voltage in the second HV system HVS2 can be limited to a previously defined maximum value. In addition, the battery modules 4 assigned to the DC-DC converters 5 can be specifically discharged or charged, so that the battery modules 4 can be balanced.

[0077] The first HV system HVS1 is supplied via the first output terminals A1+, A1-. These first output terminals A1+, A1- are routed via the two switching elements S1, S2. Furthermore, the fuse 8 is located in the connection circuit for the first HV system HVS1. Components that convert very high power can thus be supplied via the first output terminals A1+, A1-, for example, an inverter 9, in particular a drive inverter, for an electric machine 10 for driving the vehicle, or several such inverters 9 for several electric machines 10, and a DC charging connection 11.

[0078] The current is limited by a current busbar of the battery 3, the switching elements S1, S2 and the battery modules 4, in particular their cell chemistry. The supply voltage at this connection for the first HV system HVS1, i.e. at the first output connections A1+, A1-, is however dependent on the voltage of the series connection of all battery modules 4. The supply voltage is therefore affected by the charge state of the battery modules 4, in particular of the battery cells, the number of battery modules 4, a current current from or into the battery 3, in particular a voltage drop across the internal resistance. The performance of the components located in the first HV system HVS1 therefore depends on the number of battery modules 4, their charge state, their internal resistance, their temperature and / or their age and / or on other factors.

[0079] Using Figures 4 to 9, the following describes how voltage adjustment and battery balancing work by varying the number of battery modules 4.

[0080] Figure 4 shows a schematic representation of a battery module 4 with DC-DC converter 5 as well as currents I1, I2 in the battery module 4 and an output voltage Usek of the DC-DC converter 5.

[0081] Figure 5 shows a schematic representation of a DC-DC converter 5 that is inactive for positive currents on the secondary side 7. The primary side 6 and secondary side 7 are inactive. There is no clocking on the primary side 6; all switches at the top and / or bottom are open. Any switch position on the secondary side 7 is possible.

[0082] Figure 6 shows a schematic representation of a DC-DC converter 5 that is inactive for negative currents on the secondary side 7. The primary side 6 and secondary side 7 are inactive. There is no clocking on the primary side 6; all switches at the top and / or bottom are open. At least one switch in the upper row of the secondary side 7 and at least one switch in the lower row of the secondary side 7 are closed.

[0083] The optimum efficiency is achieved when all switches on the secondary side 7 are closed.

[0084] Figure 7 shows a schematic representation of an HV battery system 1 with a battery 3 and four battery modules 4. All DC-DC converters 5 are active. All battery modules 4 are loaded equally.

[0085] Figure 8 shows a schematic representation of a battery 3 with five battery modules 4. Four DC-DC converters 5 are active. The bottommost battery module 4 is loaded only by the current of the second HV system HVS2. Figure 9 shows a schematic representation of a battery 3 with five battery modules 4. Four DC-DC converters 5 are active. The middle battery module 4 is loaded only by the current of the second HV system HVS2.

[0086] The current of the battery cells can be conceptually divided into two partial currents, as shown in Figure 4 using a battery module 4 and a DC-DC converter 5 as an example. One partial current represents a supply current 11 of the first HV system HVS1. The other partial current supplies only the

[0087] DC-DC converter 5 of its associated battery module 4 is thus its supply current I2. The supply currents I1, I2 can be selected independently of each other and can also have opposite signs.

[0088] During operation, a DC-DC converter 5 can individually adjust its supply current I2. The output voltage llsec of the DC-DC converter 5 can thus be adjusted via the transformer ratio and the duty cycle. If the DC-DC converter 5 is used as a so-called DC transformer (DC voltage transformer), i.e., it always operates with a constant ratio between input voltage U and output voltage llsec, this means that the output voltage llsec of the DC-DC converter 5 is always proportional to the input voltage U. Therefore, the following applies:

[0089] Usek=k*U (1)

[0090] Where k is the factor that represents the gear ratio.

[0091] The output voltage UsekHV of the HV battery system 1 for the second HV system HVS2 is therefore the product of the output voltages Usek of the DC-DC converters 5 and the number of active DC-DC converters 5, as shown by way of example in Figures 7 to 9. In Figure 7, all DC-DC converters 5 are active, in Figure 8 the lowest DC-DC converter 5 is not active, and in Figure 9 the middle DC-DC converter 5 is not active.

[0092] If a DC-DC converter 5 is inactive, its output voltage is Usek 0V. In this case, no supply current I2 is drawn from its associated battery module 4. The DC-DC converter 5 remains conductive for a positive current flow via the diodes, particularly body diodes, of the secondary side 7, i.e., it does not represent an interruption of the current flow, as shown by way of example in Figure 5. To minimize losses, the semiconductor switches of the secondary side 7 can also be closed.

[0093] However, in the case of negative currents, for example during AC charging, it is necessary to short-circuit passive DC-DC converters 5 on the secondary side 7, ie either one half-bridge or both half-bridges are switched to low resistance, as shown as an example in Figure 6.

[0094] Figure 7 shows a battery 3 with four battery modules 4. All DC-DC converters 5 are active. The output voltage UsekHV of the HV battery system 1 between the second output terminals A2+, A2- is thus:

[0095] UsekHV=4*k*U (2)

[0096] Figures 8 and 9 show a battery 3 with a total of five battery modules 4. However, only four of the DC-DC converters 5 are active at a time. The output voltage UsekHV of the HV battery system 1 between the second output terminals A2+, A2- is therefore also:

[0097] UsekHV=4*k*U (2)

[0098] Therefore, identical components can be used on the secondary side 7, which enables standardization of these components, for example, with regard to a module strategy and / or blocking. The inactive DC-DC converter 5 can be selected at any time from among the battery modules 4 and can also be changed over time. In the example shown in Figure 8, the bottom DC-DC converter 5 is inactive, and in the example shown in Figure 9, the middle DC-DC converter 5 is inactive.

[0099] In this way, balancing of the battery modules 4 can occur during operation of the HV battery system 1, in particular of the HV system arrangement 2. If more battery modules 4 are present, several DC-DC converters 5 are also inactive in order to provide a uniform output voltage UsekHV of the HV battery system 1. With reference to Figures 10 to 12, the following describes the functionality of the voltage adjustment and battery balancing by varying the input voltage U due to a change in the state of charge (SOC), the load, the temperature, and / or other influences.

[0100] Figure 10 shows a schematic representation of an HV battery system 1 in which the input voltage II, i.e., the voltage of the battery modules 4, is very low. All DC-DC converters 5 are active, and all battery modules 4 are equally loaded.

[0101] Figure 11 shows a schematic representation of an HV battery system 1 in which the input voltage II, i.e., the voltage of the battery modules 4, is medium. One of the DC-DC converters 5 is inactive. The DC-DC converter 5 that should be inactive can be freely selected. For example, the DC-DC converters 5 can be alternated over time with respect to their inactivity.

[0102] Figure 12 shows a schematic representation of an HV battery system 1 in which the input voltage II, i.e., the voltage of the battery modules 4, is high. Two of the DC-DC converters 5 are inactive. The DC-DC converters 5 that should be inactive can be freely selected. For example, the DC-DC converters 5 can be rotated over time depending on their inactivity.

[0103] During vehicle operation, the battery voltage level can gradually change. Causes for this include, for example, a changing load on battery 3, for example due to load changes while driving, recuperation, DC charging and / or other influences, a change in the temperature of battery 3 and / or a change in the charge level of battery 3. The cell voltage of the battery cells can experience changes of, for example, approximately 2.5V to 4.2V. The voltage of each battery module 4 changes proportionally to this, i.e., the input voltage U applied to the primary side 6 of the DC-DC converter 5. The voltage across the first output terminals A1+, A1- for the first HV system HVS1 also varies.

[0104] If operation with a constant transformation ratio is selected at the DC-DC converters 5, the voltage change is passed from the primary side 6 to the secondary side 7. To ensure a stable output voltage UsekHV of the HV battery system 1 during operation, the number of active DC-DC converters 5 can be adjusted during operation. For example, at very high module voltages, i.e., at medium, high, or very high input voltage II, one or more of the DC-DC converters 5 can be inactive, i.e., advantageously deactivated, as shown by way of example in Figures 11 and 12.

[0105] In the example shown in Figure 11, one of the DC-DC converters 5, in this example the lowest DC-DC converter 5, is inactive due to the medium input voltage U. In the example shown in Figure 12, two of the DC-DC converters 5, in this example the second and third DC-DC converters 5 from the top, are inactive due to the high input voltage U. The number of inactive DC-DC converters 5 depends on the level of the input voltage II.

[0106] With a reduction in the battery voltage, i.e., the input voltage II, for example, due to a lower or decreasing state of charge while driving, the number of active DC-DC converters 5 in the series circuit supplying the second HV system HVS2 increases, i.e., previously inactive DC-DC converters 5 are advantageously activated successively. For example, at a very low input voltage U, all DC-DC converters 5 are active, as shown by way of example in Figure 10.

[0107] The described solution enables, for example, the blanking of disturbances in the first HV system HVS1. Typically, the clock frequency of the DC-DC converters 5 is many times higher than the typical clock frequency of the drive inverter, for example, 10 kHz, which is the main cause of generated on-board power system ripple. The clock frequency of the DC-DC converters 5 is, for example, 100 kHz. This makes it possible for one or more DC-DC converters 5 to react to the voltage ripple with the clocking on the primary side 6, so that the supply voltage of the second HV system HVS2 experiences this ripple only in a very weakened form.

[0108] Using Figure 13, a galvanically isolated, single-phase or multi-phase implementation of the AC charging function is described below. Figure 13 shows an example of the HV system arrangement 2 with an HV battery system 1 with four battery modules 4 and their associated DC-DC converters 5. To implement the AC charging function, only a single-phase or multi-phase power factor correction filter 12 is required. The power factor correction filter 12 is also referred to as PFC (Power Factor Correction). If a three-phase AC charging function is to be implemented, a three-phase power factor correction filter 12 is required.

[0109] A state-of-the-art galvanically isolating AC charger for charging the battery 3 from the AC source of the building's technology or AC charging station consists of two main components: the power factor correction filter 12 and a galvanically isolating DC-DC converter. The power factor correction filter 12 rectifies the AC voltage and boosts it, i.e., increases it, to a predetermined value, for example, to 450V for single-phase charging and 650V for three-phase charging in a 230V AC network. Furthermore, an AC charging current is set that is in phase with the AC voltage. The galvanically isolating DC-DC converter provides galvanic isolation between the AC side of the building's technology and the vehicle's high-voltage system. The transformer's transformation ratio can be used to adjust the internal output voltage of the power factor correction filter 12 to the voltage of the battery 3, for example, 800V.In addition, galvanic isolation prevents AC leakage currents through the Y capacitances of the vehicle's high-voltage system. Overvoltages in the AC network can also be mitigated.

[0110] In Figure 13, the power factor correction filter 12 is part of the second HV system HVS2. Typical three-phase power factor correction filters 12, such as a Vienna rectifier or a B6 bridge module, can be used as the power factor correction filter 12. The DC output current of the power factor correction filter 12 is transmitted to the battery modules 4 via a suitable number of DC-DC converters 5.

[0111] If the output voltage of the power factor correction filter 12 is low, for example, during single-phase AC charging and / or at a low AC voltage, only a small number of the DC-DC converters 5 are active. The active DC-DC converters 5 alternate over time, so that all battery modules 4 are in a balanced state of charge at the end of AC charging, comparable to the balancing described above.

[0112] If the output voltage of the power factor correction filter 12 is higher, for example, during three-phase AC charging, then a higher number of DC-DC converters 5 are active. Since the power flow during charging is reversed compared to the previously described states, the inactive DC-DC converters 5 are switched to passive mode in the operating state described here by switching on at least one semiconductor switch in the upper row and at least one semiconductor switch in the lower row on the secondary side 7. For optimal efficiency, all semiconductor switches are switched on.

[0113] Based on Figure 14, which shows an example of the HV system arrangement 2, particularly during DC charging at a DC charging station 14, a reduction in the Y capacitance through the galvanic isolation of both HV systems HVS1, HVS2 and a dampening of the EMC emissions between the first HV system HVS1 and the second HV system HVS2 are described below. The galvanic isolation of the two HV systems HVS1, HVS2 is illustrated in Figure 14 by a dashed line through the DC-DC converters 5, because this galvanic isolation is achieved in particular by the galvanic isolation of the primary side 6 from the secondary side 7 of the DC-DC converters 5.

[0114] Due to the galvanic isolation of the DC-DC converters 5, the second HV system HVS2 with its Y-capacitances is not visible at the DC connection circuit 13, meaning that its Y-capacitances are not relevant. This allows for more effective, and in particular, smaller, EMC filtering for the components in the DC connection circuit 13 by increasing the values ​​of the Y-capacitances there. Furthermore, larger stray capacitances can be accepted.

[0115] Stray capacitances are formed by adjacent surfaces of HV potentials to PE / PA (PE = ground potential, PA = potential equalization), such as in a cooling connection in power electronics, the electric machine 10 or the battery 3. In addition, stray capacitances are caused by the cell structure of the battery 3.

[0116] The described solution also enables the attenuation of EMC emissions between the first HV system HVS1 and the second HV system HVS2. During DC charging, increased EMC requirements must be met. The emissions are measured at the DC charging connection 11. During DC charging, mainly components in the second HV system HVS2 are active, for example, a cooling and / or heating system and / or an LV DC / DC converter. Since the DC-DC converters 5 in the respective battery module 4 represent a filter due to their design, in particular due to their transformer and their capacitances and inductances, the interference suppression of the components in the second HV system HVS2 can be made smaller. This reduces the size of the filters in these components. However, this requires good EMC suppression of the DC-DC converters 5 of the battery modules 4 on the primary side 6.

[0117] With reference to Figures 15 and 16, a so-called limp-home function is described below in the event of a defect in one of the battery modules 4 or in the event of an interruption, in particular in the area of ​​the battery 3, in particular in the area of ​​one of the battery modules 4. Figure 15 shows a schematic representation of the HV battery system 1 with a battery module 4 which has the interruption or is high-resistance. In the example shown, this is the middle battery module 4. In order to bridge this interrupted or high-resistance battery module 4, the supply current 11 for the first HV system HVS1 is passed via the DC-DC converter 5 coupled to this battery module 4, in the example shown thus via the middle DC-DC converter 5. The supply voltage for the first HV system HVS1, i.e. the input voltage U, is reduced by the failure of one of the battery modules 4, i.e. by its voltage.However, with this reduced supply voltage for the first HV system HVS1, the limp-home function is still possible, i.e. a type of emergency driving mode of the vehicle to enable continued driving, for example, to home or to a workshop or to the nearest parking lot.

[0118] To enable this, i.e., in particular, to bridge the interrupted or high-impedance battery module 4 using its DC-DC converter 5, this DC-DC converter 5 is operated with a bridge short circuit on the primary side 6 and the secondary side 7, as schematically shown in Figure 16. The currents on the primary side 6 and the secondary side 7 are indicated here by arrows. The primary side 6 is inactive; there is no clocking, and advantageously all switches are closed. The secondary side 7 is inactive; here, the switch position is arbitrary; however, advantageously all switches are closed.

[0119] The other DC-DC converters 5 are active to supply the second HV system HVS2.

[0120] The limp-home function is required in the event of a defect in one of the battery modules 4, i.e. in particular if it becomes high-resistance or an interruption occurs. If this occurs during vehicle operation, i.e. if one of the battery modules 4 fails, this would lead to a complete failure of the supply to the first HV system HVS1 without the described procedure for the limp-home function. However, since in the solution described here each battery module 4 is assigned its own DC-DC converter 5, in particular connected in parallel, it is possible to supply the first HV system HVS1 with a reduced supply current 11. The level of this supply current 11 for the first HV system HVS1 is determined by the selection of the components of the DC-DC converter 5.In addition, other components can be connected in parallel to bridge the battery module 4, for example MOSFETs, IGBTs or diodes (MOSFET = metal oxide semiconductor field effect transistor and IGBT = insulated gate bipolar transistor).

[0121] The DC-DC converter 5 of the affected, i.e., defective, battery module 4 can conduct a current via the body diodes of the MOSFETs on the primary side 6 from the moment the battery module 4 fails. To reduce losses, the MOSFETs are advantageously switched on afterwards, particularly shortly thereafter, in order to minimize waste heat generated by the semiconductors. This DC-DC converter 5 is therefore no longer able to generate voltage for the second HV system HVS2. Here, too, it is possible on the secondary side 7 of this DC-DC converter 5 to conduct the supply current via the semiconductors of the secondary side 7. During DC charging or recuperation, it is necessary to permanently control at least one semiconductor switch in the upper row and at least one semiconductor switch in the lower row on the primary side 6 of this DC-DC converter 5. Advantageously, all semiconductor switches are switched on.

[0122] The solution described above using the exemplary figures 1 to 16 can achieve the following advantages:

[0123] - The components in the second HV system HVS2 can be standardized.

[0124] - The operating voltage range of the components in the second HV system, HVS2, is significantly limited. This enables a cost-effective and efficiency-optimized design of these components.

[0125] - Battery module balancing is enabled.

[0126] - The limp-home function is enabled. In the event of a high-resistance defect in battery module 4, driving can continue at reduced current.

[0127] - EMC attenuation during DC charging is enabled. The HV components in the second HV system HVS2, or more precisely, the EMC interference caused by them, are attenuated by the filtering effect of the DC-DC converters 5. The EMC filters for these components can thus be designed smaller. - A reduction in the visible Y-capacitances during DC charging is enabled. Due to the galvanic isolation of the DC-DC converters 5, all Y-capacitances of the components located in the second HV system HVS2 have no effect on the DC connection circuit 13.

[0128] - The DC-DC converters 5 can be used for AC charging. To implement the galvanically isolated AC charging function, only one power factor correction filter 12 is required, significantly reducing the size of the on-board charger.

[0129] List of reference symbols

[0130] 1 HV battery system 2 HV system arrangement

[0131] 3 Battery 4 Battery module

[0132] 5 DC-DC converter 6 Primary side

[0133] 7 Secondary side 8 Fuse

[0134] 9 Inverter 10 Machine

[0135] 11 DC charging port 12 Power factor correction filter

[0136] 13 DC connection circuit 14 DC charging station

[0137] A1+, A1- first output connection A2+, A2- second output connection HVS1 first HV system HVS2 second HV system 11 supply current first HV system I2 supply current DC-DC converter M+, M- module connection S1, S2 switching element U input voltage Usek output voltage DC-DC converter UsekHV output voltage HV battery system

[0138] W+, W- converter connection

Claims

Patent claims 1. HV battery system (1) for an electrically powered vehicle, comprising a battery (3) with a plurality of battery modules (4), each having at least one battery cell, wherein each battery module (4) is coupled to a primary side (6) of its own galvanically isolated DC-DC converter (5), characterized in that - the battery (3) via switching elements (S1, S2) with first Output terminals (A1+, A1-) can be coupled or is coupled, wherein at least one of the switching elements (S1, S2) is a galvanically isolating switching element (S1, S2), and - an electrical series circuit of secondary sides (7) of the DC-DC converters (5) is coupled to second output terminals (A2+, A2-).

2. HV battery system (1) according to claim 1, characterized in that the battery modules (4) are electrically connected in series.

3. HV battery system (1) according to one of the preceding claims, characterized in that the DC-DC converters (5) are each designed such that they transmit a voltage of the battery module (4) to which they are coupled to the secondary side (7) in a fixed ratio.

4. HV battery system (1) according to one of the preceding claims, characterized in that the respective DC-DC converter (5) is designed as a unidirectional or as a bidirectional DC-DC converter (5).

5. HV battery system (1) according to one of the preceding claims, characterized in that the battery cells and the DC-DC converters (5) are thermally coupled to a common cooling device.

6. HV battery system (1) according to one of the preceding claims, characterized in that one of the switching elements (S2, S1) is a semiconductor switch.

7. HV battery system (1) according to one of the preceding claims, characterized in that a fuse (8) is arranged between the battery (3) and one of the first output terminals (A1+, A1-).

8. HV system arrangement (2) for an electrically powered vehicle, comprising an HV battery system (1) according to one of the preceding claims, a first HV system (HVS1) coupled to the first output terminals (A1+, A1-) of the HV battery system (1), and a second HV system (HVS2) coupled to the second output terminals (A2+, A2-) of the HV battery system (1), characterized in that each component of the second HV system (HVS2) has a lower power consumption than each component of the first HV system (HVS1).

9. HV system arrangement (2) according to claim 8, characterized in that all components of the second HV system (HVS2) are designed for operation with a standardized supply voltage.

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