Method for operating a voltage equalization device for a high-voltage energy storage device of an at least partially electrically powered motor vehicle, computer program product and voltage equalization device

Abstract

The invention relates to a device and method for operating a voltage equalization device (20) for a high-voltage energy storage device (12), comprising the steps of: providing an electrical isolation device (14) for separating the high-voltage energy storage device (12) into at least two partial storage devices (16, 18); providing a first DC-DC converter (26) for a first partial storage device (16); providing a second DC-DC converter (28) for a second partial storage device (18); detecting a first partial voltage of the first partial storage device (16); detecting a second partial voltage of the second partial storage device (18); comparing the first partial voltage with the second partial voltage; predicting a power demand (60) in a low-voltage network (34) of the motor vehicle (10);Determining a first efficiency (44) of the first DC-DC converter (26) and a second efficiency (44) of the second DC-DC converter (28) as a function of the determined power requirement (60) and operating the DC-DC converters (26, 28) as a function of the comparison and as a function of the determined efficiency (44). The invention further relates to a computer program product and a voltage equalization device 20.

Description

[0001] The invention relates to a method for operating a voltage equalization device for a high-voltage energy storage device of an at least partially electrically powered motor vehicle according to the applicable claim 1. Furthermore, the invention relates to a computer program product and a voltage equalization device.

[0002] Battery-electric vehicles can, for example, have a so-called 800-volt system. However, there is still a relatively large number of charging stations that can only provide a low maximum charging voltage. These charging stations are therefore insufficient to fully charge the corresponding vehicles. For this reason, it is already known from the prior art that, for example, a 400-volt backward-compatible charging function is provided in the vehicle. In this state, the high-voltage energy storage system is divided into two halves, which can be charged in series at 800-volt charging stations. At charging stations with a lower voltage, they are charged in parallel.

[0003] In the case of 400-volt backward-compatible charging, the two storage halves can be connected in parallel without damaging the hardware, provided the voltage difference between them is less than a hardware-dependent threshold. Otherwise, uncontrolled equalizing currents between the two storage halves can occur, potentially leading to hardware damage and, for example, a vehicle breakdown.

[0004] German patent application DE 10 2019 120 882 A1 provides a system and method for selecting converters to operate with non-zero current in a distributed converter system. A vehicle includes a traction battery comprising a plurality of cells. The vehicle also includes a plurality of power converters, each electrically coupled between a corresponding group of cells and an electric bus. A controller is programmed to meet the current demand of the electric bus by operating a subset of the power converters to draw a current exceeding a threshold corresponding to a power converter efficiency exceeding a predetermined level. Power converters not assigned to this subset operate at zero current.

[0005] German patent DE 10 2019 121 918 A1 provides a DC power conversion system for electrified vehicles with battery state balancing. A high-voltage battery pack comprises a series of connected battery units, each of which separately supplies power to its own DC / DC converter. The converter outputs are connected in parallel to supply a low-voltage DC bus. A central module includes an external circuit controller that generates a target current to regulate the bus voltage and an assigner that distributes the target current to the respective converters via commands regarding the allocated current. Local controllers regulate the output current of each individual converter.The assigner identifies battery units with a predefined deviation from a reference metric that characterizes the battery pack, assigns reverse currents to the respective converters for the identified battery units, and increases the target current assigned to the DC / DC converters that have not been assigned a reverse current. Battery units with extremely low and high states compared to the other units are quickly balanced, thereby improving the overall performance of the battery pack.

[0006] DE 10 2016 213070 B4 relates to a method and a vehicle electrical system comprising an inverter, an electrical energy storage device, an electric machine, and an AC transmission connection, wherein the inverter has a first side and a second side and is configured to transfer power between these sides, wherein on the first side of the inverter two output terminals of the inverter are connected or connectable to the energy storage device, wherein on the second side of the inverter at least two phase current terminals of the inverter are connected or connectable to the electric machine, wherein at least one of the charging inputs of the vehicle electrical system can be switched to an inner motor phase of the electric machine by means of a switching device controlled by a control unit, and wherein the vehicle electrical system is configured to first charge the electrical energy storage device with a first voltage.and then to charge the electrical energy storage device with a second voltage, where the second voltage is greater than the first voltage.

[0007] The object of the present invention is to provide a method, a computer program product and a voltage equalization device by means of which voltages within the high-voltage energy storage device can be reliably equalized.

[0008] This problem is solved by a method, a computer program product, and a voltage equalization device according to the independent claims. Advantageous embodiments are specified in the dependent claims.

[0009] One aspect of the invention relates to a method for operating a voltage equalization device for a high-voltage energy storage system of an at least partially electrically powered motor vehicle. The voltage equalization device includes an electrical isolation device for dividing the high-voltage energy storage system into at least two sub-storage units. A first DC-DC converter is provided for the first sub-storage unit of the high-voltage energy storage system. A second DC-DC converter is provided for the second sub-storage unit of the high-voltage energy storage system. A first detection device of the voltage equalization device measures the voltage of the first sub-storage unit, and a second detection device of the voltage equalization device measures the voltage of the second sub-storage unit.The first partial voltage is compared with the second partial voltage using an electronic processing unit in the voltage equalization device. The power requirement of a low-voltage motor vehicle network is predicted using this electronic processing unit. A first efficiency of the first DC-DC converter and a second efficiency of the second DC-DC converter are determined as a function of the predicted power requirement. The operation of the first DC-DC converter and the second DC-DC converter is then carried out based on the comparison and the determined efficiency using the electronic processing unit.

[0010] In particular, to treat the voltage delta or voltage difference between the two battery halves equally, a suitable operating strategy is necessary to ensure that no excessively large voltage differences occur between them. This functionality can also be described as pack balancing.

[0011] In other words, the system is designed so that, depending on the voltage levels within the two storage units, the DC-DC converters will employ different operating strategies. For example, one DC-DC converter can be subjected to a heavier load than the other, resulting in a greater power draw from the storage units assigned to that DC-DC converter. This increased load can then be maintained until the voltage levels are essentially balanced.

[0012] It goes without saying that at other voltage levels, the energy storage system can also be divided into, for example, three or four sub-storage units. Each sub-storage unit is then assigned its own DC-DC converter. Depending on how the individual sub-voltages relate to each other, a specific operating strategy can be set for the DC-DC converters.

[0013] In addition, it is now planned that, due to the poor efficiency of the DC-DC converters in low-load operation, an energy-optimized method will be provided to optimize this technical problem, so that the efficiency of the energy supply of the high-voltage energy storage is maximized, and at the same time the task of pack symmetry is ensured.

[0014] The basic principle of this method, particularly within a regulated power context, is to transition to a time-dependent energy control task. In a first step, the underlying efficiencies of the predicted operating points are determined and planned using a corresponding energy management algorithm. The result of this charging plan, especially for covering the low-voltage energy demand, is predicted time-based load distributions that cover both the required energy of the low-voltage storage system and the energy load distribution of the high-voltage system, in accordance with the pack balancing task.

[0015] In other words, a predictive pulse width modulation operation is established between the two DC-DC converters, the aim of which is to keep the energy load of the high-voltage pack at a level communicated by the battery management system.

[0016] For this purpose, the low-voltage battery management system determines a predictive energy demand and distributes the required energy based on the efficiency of the DC-DC converters. This distribution also takes into account the pack balancing of the high-voltage battery.

[0017] In particular, it is possible that a battery management system is provided as an electronic computing unit for the high-voltage energy system, and a second electronic computing unit is provided for the low-voltage system. Alternatively, the battery management system for both the high-voltage energy storage system and the low-voltage electrical system can be provided by a single electronic computing unit.

[0018] In particular, this takes into account that DC-DC converters exhibit lower efficiencies at low power outputs than at higher power outputs. Specifically, very poor efficiency is observed at low power levels, while higher efficiency is seen at higher power levels. Therefore, it is essential that DC-DC converters are operated only at high power levels to achieve correspondingly high efficiencies.

[0019] According to an advantageous embodiment, depending on the comparison, more electrical energy is supplied by one of the two DC-DC converters than by the other. For example, a corresponding coupling can be provided on the low-voltage side of the two DC-DC converters. If, for instance, the first partial voltage is higher than the second partial voltage, electrical energy can be supplied from the first DC-DC converter to the second DC-DC converter, so that essentially the second partial storage unit can be charged via the first DC-DC converter and thus via the first partial storage unit. In particular, charge equalization and voltage equalization can thus be carried out.In other words, the first DC-DC converter and the second DC-DC converter can supply electrical energy from the high-voltage range, particularly for a low-voltage electrical system, such as a 12-volt system. It can then be configured so that, depending on the comparison, more electrical energy is supplied by one of the two DC-DC converters than by the other. For example, if the first partial voltage in the first sub-converter is higher than the second partial voltage in the second sub-converter, the electrical energy for the low-voltage electrical system can be supplied by the first DC-DC converter. This results in a higher load on the first sub-converter, thereby enabling an adjustment of the partial voltages.This ensures, particularly during a charging process, that both storage units have a similar voltage value.

[0020] Another advantageous design involves covering the power demand based on an individual, time-based load distribution across the DC-DC converters. For example, the power demand can be converted into a corresponding unit of time. Based on the efficiencies, the load distribution can then follow a time-based load distribution plan. For instance, a longer period can be allocated to the load for the low-voltage electrical system for the first DC-DC converter than for the second, so that more power is supplied by the first DC-DC converter than by the second. This allows for reliable pack balancing and simultaneous consideration of the respective efficiencies.

[0021] It is also advantageous to compare the predicted power demand with the actual power demand and adjust the load distribution in the DC-DC converter accordingly. This allows for adjustments, particularly if the predicted power demand deviates from the actual power demand. This ensures a highly reliable process.

[0022] It is also advantageous to operate the DC-DC converters under high load. In particular, DC-DC converters exhibit higher efficiency under high load than under low load. Therefore, operating the DC-DC converters under high load is beneficial. Accordingly, a suitable load distribution across the DC-DC converters is implemented to maximize efficiency.

[0023] It is also advantageous if the high-voltage energy storage system is provided with a voltage of essentially 800 volts and / or the first and / or the second partial voltage is provided with essentially 400 volts. In other words, it is intended that the high-voltage energy storage system is provided with 800 volts and a separation is implemented such that the first and second partial storage systems each have 400 volts. This makes it possible, for example, to charge at 400-volt charging stations.

[0024] It is also advantageous if the procedure is carried out during a discharge and / or charging process of the high-voltage energy storage system. For example, the procedure can be performed during a discharge process so that the voltage level of the two storage units remains essentially constant. Furthermore, the voltage level can also be equalized during the charging process; for example, each storage unit can be charged at 400 volts, and then, should voltage differences arise, the higher-voltage unit can additionally charge the lower-voltage unit. Thus, voltage equalization can also be achieved during the charging process itself.

[0025] Furthermore, it has proven advantageous if the respective partial voltages of the storage units are essentially equalized using this method. In particular, they are at least equalized or balanced such that the voltage difference is below a predetermined threshold. This prevents corresponding unwanted equalizing currents between the two storage units, or battery cells of the storage units.

[0026] The presented method is, in particular, a computer-implemented method. Therefore, a further aspect of the invention relates to a computer program product with program code means which, when the program code means are executed by the electronic computing unit, cause an electronic computing device to carry out a method according to the preceding aspect.

[0027] A further aspect of the invention therefore also relates to a computer-readable storage medium containing the computer program product according to the preceding aspect.

[0028] The invention also relates to a voltage equalization device for a high-voltage energy storage device of an at least partially electrically powered motor vehicle, comprising at least one electrical isolating device, a first detection device, a second detection device, a first DC-DC converter, a second DC-DC converter, and an electronic computing device, wherein the voltage equalization device is configured to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the voltage equalization device.

[0029] Furthermore, the invention also relates to a high-voltage energy storage device with a voltage equalization device according to the preceding aspect. The high-voltage energy storage device is provided, in particular, with, for example, 800 volts.

[0030] Furthermore, the invention also relates to a motor vehicle, at least electrically powered, with a high-voltage energy storage device as described above. The motor vehicle can also be fully electric.

[0031] Advantageous embodiments of the method are to be regarded as advantageous embodiments of the voltage equalization device, the high-voltage energy storage device, and the at least partially electrically powered motor vehicle. The voltage equalization device, the high-voltage energy storage device, and the at least partially electrically powered motor vehicle possess specific features to enable the corresponding process steps to be carried out.

[0032] A computing unit / electronic computing device can be understood, in particular, as a data processing device containing a processing circuit. The computing unit can therefore process data to perform arithmetic operations. This may also include operations to perform indexed access to a data structure, such as a lookup table (LUT).

[0033] The computing unit may, in particular, contain one or more computers, one or more microcontrollers, and / or one or more integrated circuits, for example, one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and / or one or more systems on a chip (SoCs). The computing unit may also contain one or more processors, for example, one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs), and / or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit may also include a physical or virtual array of computers or other units of the aforementioned type.

[0034] In various embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more storage units.

[0035] A storage unit can be volatile data storage, for example as dynamic random access memory (DRAM) or static random access memory (SRAM), or as non-volatile data storage, for example as read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or flash EEPROM, ferroelectric random access memory (FRAM), or magnetoresistive random access memory.It can be designed as MRAM (magnetoresistive random access memory) or as phase-change random access memory, PCRAM (phase-change random access memory).

[0036] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0037] The invention will now be explained in more detail with reference to a preferred embodiment and the drawings. The drawings show: Fig. 1 a schematic side view of an embodiment of a motor vehicle with an embodiment of a high-voltage energy storage device with an embodiment of a voltage equalization device; Fig. 2 a schematic block diagram according to an embodiment of a voltage equalization device; Fig. 3 a schematic flowchart according to one embodiment of the method; and Fig. 4 a time-performance diagram according to an embodiment of the method.

[0038] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0039] Fig. Figure 1 shows a schematic side view of an embodiment of a motor vehicle 10. The motor vehicle 10 is, in particular, at least partially or fully electrically powered. For this purpose, the motor vehicle 10 has a high-voltage energy storage device 12. The high-voltage energy storage device 12 can, for example, be operated at 800 volts. In order to achieve backward compatibility of the high-voltage energy storage device 12 for charging at a voltage of, for example, 400 volts, it is provided that the high-voltage storage device 12 has a disconnecting device 14, which is, in particular, essentially a switching device that electrically disconnects a first partial storage unit 16 from a second partial storage unit 18. In particular, corresponding switching elements can be provided for this purpose, which can essentially connect the first partial storage unit 16 and the second partial storage unit 18 in parallel or in series, depending on the selected circuit.In a series circuit, 800 volts can be provided, while in a parallel circuit, 400 volts are provided at each end.

[0040] To prevent damage to the hardware used in parallel-connected sub-memories 16 and 18, it is necessary to keep voltage differences between the two sub-memories 16 and 18 low. In particular, this prevents uncontrolled equalizing currents between the two sub-memories 16 and 18.

[0041] In order to keep the corresponding voltage delta small, appropriate operating strategies are necessary to ensure that there are no excessively large voltage differences between the two sub-storage units 16, 18.

[0042] For this purpose, a voltage equalization device 20 is provided in particular. The voltage equalization device 20 comprises, in particular, at least the electrical isolating device 14, a first detection device 22, a second detection device 24, a first DC-DC converter 26, a second DC-DC converter 28 and an electronic computing device 30.

[0043] The first detection device 22 and the second detection device 24 are specifically designed to detect the respective partial voltages.

[0044] The Fig. Figure 1 further shows that, for example, electrical energy for an electric drive unit 32 can be provided by the high-voltage energy storage device 12. Furthermore, the motor vehicle 10 can have a low-voltage electrical system 34.

[0045] In particular, it is thus provided that a first partial voltage of the first partial storage 16 is detected by the first detection device 22 and a second partial voltage of the second partial storage 18 is detected by the second detection device 24. The first partial voltage is compared with the second partial voltage by the electronic processing unit 30. Depending on the comparison, the first DC-DC converter 26 and the second DC-DC converter 28 are operated by the electronic processing unit 30. In particular, the electronic processing unit 30 can, for example, transmit corresponding control signals to the first DC-DC converter 26 and the second DC-DC converter 28.

[0046] Fig. Figure 2 shows a schematic block diagram according to an embodiment of the voltage equalization device 20. In the present embodiment, it is shown in particular that high-voltage energy consumers 36 can also be connected to the high-voltage energy storage device 12. Furthermore, the Fig. 2, that the low-voltage electrical system 34 may, for example, be equipped with a low-voltage power source 38. Furthermore, it may be provided, in particular, that the low-voltage electrical system 34 may also have its own electronic computing device 40, for example in the form of a battery management system.

[0047] Fig. Figure 3 shows a schematic flowchart according to one embodiment of the method. In particular, it is provided that, for example, the electronic computing unit 30 determines the corresponding balancing requirement 42. The low-voltage management system, in particular the electronic computing unit 40, determines an efficiency optimization 44 for the DC-DC converters 26, 28. A charging plan 46 is then created. A correction 48 of the charging plan 46 can then be made. In this context, it can be provided, for example, that the charging plan 46 is subsequently implemented via a conversion 50. Based on a corresponding update of the balancing requirement, which is indicated by the reference numeral 52, a corresponding deviation 54 between the predicted power requirement and the actual power requirement can again be determined.This can in turn be carried out via a return operation 56 and a loading plan correction 58, which then results in the correction 48 being carried out again.

[0048] Fig. Figure 4 shows a schematic time-power diagram. The upper part shows the total power requirement 60, specifically over the period from time t0 to t1. It can be provided, for example, that the first DC-DC converter 26 supplies power from time t0 to t2. The corresponding power can then be supplied by the second DC-DC converter 28 from time t2 to t1. In particular, it is thus provided that, in addition to the pack symmetry, a corresponding efficiency 44 of the DC-DC converters 26 and 28 is determined. It is then provided that the DC-DC converters 26 and 28 are operated depending on the comparison of the respective partial voltages of the partial storage units 16 and 18 and depending on the efficiency 44.

[0049] Here, as in the Fig.4 shown, in particular it is provided that the power requirement 60 is covered on the basis of the respective individual load distributions 62, 64 on the DC voltage transformers 26, 28. Reference symbol list 10 motor vehicle 12 high-voltage energy storage units 14 Separating device 16 first sub-memory 18 second sub-memory 20 Voltage equalization device 22 first recording device 24 second recording device 26 first DC-DC converter 28 second DC-DC converter 30 electronic computing devices 32 Drive unit 34 Low-voltage electrical system 36 high-voltage consumers 38 Low-voltage source 40 additional electronic computing devices 42 Pack symmetry requirements 44 Efficiency 46 Loading plan 48 Correction 50 Implementation 52 Update 54 deviation 56 Repatriation 58 Loading plan correction 60 Power requirement 62 first load distribution 64 second load distribution QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2019 120 882 A1

[0004] DE 10 2019 121 918 A1

[0005] DE 10 2016 213070 B4

[0006]

Claims

[1] Method for operating a voltage compensation device (20) for a high-voltage energy storage device (12) of an at least partially electrically operated motor vehicle (10), comprising the steps: - Providing an electrical separating device (14) of the voltage compensation device (20) for separating the high-voltage energy storage device (12) into at least two partial storage devices (16, 18); - Providing a first DC-DC converter (26) of the voltage compensation device (20) for a first partial storage device (16) of the high-voltage energy storage device (12); - Providing a second DC-DC converter (28) of the voltage compensation device (20) for a second partial storage device (18) of the high-voltage energy storage device (12); - detecting a first partial voltage of the first partial storage (16) by means of a first detection device (22) of the voltage compensation device (20); - detecting a second partial voltage of the second partial storage (18) by means of a second detection device (24) of the voltage compensation device (20); - comparing the first partial voltage with the second partial voltage by means of an electronic computing device (30) of the voltage compensation device (20); - predicting a power requirement (60) in a low-voltage network (34) of the motor vehicle (10) by means of the electronic computing device (30); - determining a first efficiency (44) of the first DC-DC converter (26) and a second efficiency (44) of the second DC-DC converter (28) as a function of the determined power requirement (60); and - Operating the first DC-DC converter (26) and the second DC-DC converter (28) as a function of the comparison and as a function of the determined efficiency (44) by means of the electronic computing device (30). [2] Method according to claim 1, characterized by that, depending on the comparison, more electrical energy is provided by one of the two DC-DC converters (26, 28) than by the other of the two DC-DC converters (26, 28). [3] Method according to claim 1 or 2, characterized by that the power requirement (60) is covered on the basis of a respective individual temporal load distribution (62, 64) on the DC-DC converters (26, 28). [4] Method according to one of the preceding claims, characterized by that the predicted power requirement (60) is compared with an actual power requirement (60) and a load distribution (62, 64) in the DC-DC converters (26, 28) is adjusted depending on the comparison. [5] Method according to one of the preceding claims, characterized by that the DC-DC converters (26, 28) are operated in high-load mode. [6] Method according to one of the preceding claims, characterized by that the high-voltage energy storage device (12) is provided with a voltage of substantially 800V and / or the first partial voltage and / or the second partial voltage is provided with substantially 400V. [7] Method according to one of the preceding claims, characterized by that the method is carried out during a discharging process and / or during a charging process of the high-voltage energy storage device (12). [8] Method according to one of the preceding claims, characterized by that respective partial voltages of the partial accumulators (16, 18) are substantially equalized by means of the method. [9] Computer program product with program code means which cause an electronic computing device (30) to carry out a method according to one of claims 1 to 8 when the program code means are processed by the electronic computing device (30). [10] Voltage compensation device (20) for a high-voltage energy storage device (12) of an at least partially electrically operated motor vehicle (10), with at least one electrical isolating device (14), a first detection device (22), a second detection device (24), a first DC-DC converter (26), a second DC-DC converter (28) and an electronic computing device (30), wherein the voltage compensation device (20) is designed to carry out a method according to one of claims 1 to 8.

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