Method and device for transmitting information concerning cell voltages of cells of an energy storage device and / or energy converter.

Abstract

In a method for transmitting information regarding the cell voltages of cells in an energy storage device and / or energy converter, a single-cell voltage is determined for each cell. Based on these single-cell voltages, at least one reference single-cell voltage of the energy storage device and / or energy converter is determined. Depending on this reference single-cell voltage, the limits of a predetermined number of voltage sections are determined, with each voltage section being representative of a voltage range relative to the reference single-cell voltage. The cells of the energy storage device and / or energy converter are then assigned to these voltage sections based on their individual cell voltages. Data is transmitted containing information about this assignment of voltage sections.

Description

[0001] The invention relates to a method for transmitting information concerning the cell voltages of cells in an energy storage device and / or energy converter. The invention further relates to a corresponding device for transmitting information concerning the cell voltages of cells in an energy storage device and / or energy converter.

[0002] Energy storage and / or energy converter systems can be used in many applications, such as in vehicles. These systems include, for example, a fuel cell stack, which consists of many individual cells. To prevent permanent damage, it is important to monitor the voltages of the individual cells. However, since the energy storage and / or energy converter system may contain a very large number of cells, a significant amount of data must be sent to a control unit for this purpose.

[0003] The object underlying the invention is to enable very fast and efficient monitoring of an energy storage device and / or energy converter.

[0004] The problem is solved by the features of the independent patent claim. Advantageous embodiments are characterized in the dependent claims.

[0005] The invention is characterized by a method for transmitting information concerning the cell voltages of cells in an energy storage device and / or energy converter. The invention is further characterized by a corresponding device for transmitting information concerning the cell voltages of cells in an energy storage device and / or energy converter.

[0006] In the process for transmitting information regarding the cell voltages of cells in an energy storage device and / or energy converter, a single-cell voltage is determined for each cell. Based on these individual cell voltages, at least one reference single-cell voltage of the energy storage device and / or energy converter is determined. Depending on this reference single-cell voltage, the limits of a predetermined number of voltage sections are determined, with each voltage section being representative of a voltage range relative to the reference single-cell voltage. The cells of the energy storage device and / or energy converter are then assigned to these voltage sections based on their individual cell voltages. Data is transmitted containing information about this assignment of voltage sections.

[0007] The information regarding the assignment of voltage sections includes, for example, a number that is representative of the assignment of voltage sections for individual selected cells or the assignment of voltage sections for all cells.

[0008] Each voltage section comprises a lower and an upper limit that define its boundaries. These limits are determined based on at least one reference single-cell voltage, ensuring that each voltage section is representative of a voltage range relative to that reference single-cell voltage.

[0009] The energy storage device and / or energy converter is in particular a fuel cell stack or a battery with multiple cells.

[0010] The process is carried out, for example, by a so-called Cell Voltage Monitor, whereby the data is sent to a control unit that is designed to monitor the energy storage device and / or energy converter.

[0011] By transmitting information about the assignment of voltage sections instead of individual cell voltages, the amount of data to be transmitted can be drastically reduced. Thus, the data required for monitoring the energy storage system and / or energy converter can be transmitted very efficiently using the method described above, enabling highly efficient and rapid monitoring of the energy storage system and / or energy converter.

[0012] According to an optional configuration, a minimum single-cell voltage of the energy storage device and / or energy converter is determined as a reference single-cell voltage. A maximum single-cell voltage of the energy storage device and / or energy converter is determined as a further reference single-cell voltage. Depending on the minimum and maximum single-cell voltages, the limits of the specified number of voltage sections are determined, with each voltage section being representative of a voltage range between the minimum and maximum single-cell voltages.

[0013] The minimum and maximum single-cell voltages are particularly well-suited together as reference single-cell voltages. Since the voltage ranges are always divided between the minimum and maximum single-cell voltages, no significant information loss is expected, as the minimum and maximum single-cell voltages should not differ too greatly. This allows for the highly efficient transmission of the data required for monitoring the energy storage system and / or energy converter, enabling very efficient, comprehensive, and rapid monitoring of the energy storage system and / or energy converter.

[0014] According to a further optional configuration, an average single-cell voltage is determined as a reference single-cell voltage, and the limits of the specified number of voltage sections are determined based on the minimum single-cell voltage, the maximum single-cell voltage, and the average single-cell voltage. This allows for an even more precise distribution of the voltage sections, as it also provides a reference to the average single-cell voltage.

[0015] According to a further optional embodiment, the voltage range of at least one of the voltage sections is relative to the minimum single-cell voltage or the maximum single-cell voltage or the average single-cell voltage.

[0016] This allows the voltage ranges to be distributed very dynamically. For example, a voltage section has a lower limit of a first percentage of the maximum single-cell voltage, the minimum single-cell voltage, or the average single-cell voltage, and an upper limit of a second percentage of the maximum single-cell voltage, the minimum single-cell voltage, or the average single-cell voltage.

[0017] According to another optional embodiment, the voltage range of at least one of the voltage sections is absolute.

[0018] For certain voltage ranges, it can be advantageous for them to meet a specified accuracy. Since the specified accuracy cannot always be guaranteed with a relative distribution, it is advantageous to assign such a voltage range an absolute voltage value, such as 2 mV, 10 mV, 30 mV, or 50 mV.

[0019] A combination of absolute and relative stress ranges is particularly advantageous. For example, some stress sections can have a relative stress range, while the remaining section has an absolute stress range. It is also possible, for instance, to determine both a relative and an absolute stress range for each stress section and then select the stress range with higher accuracy from these two.

[0020] According to a further optional embodiment, at least two of the voltage sections have voltage ranges of different sizes; in particular, the voltage range of the voltage section adjacent to the minimum single-cell voltage is smaller than the voltage range of at least one of the remaining voltage sections.

[0021] Cells with a single-cell voltage close to the minimum single-cell voltage require particularly close monitoring. Therefore, it is advantageous to choose a very small voltage range adjacent to the minimum single-cell voltage.

[0022] According to another optional configuration, the specified number of voltage sections is 4, 8 or 16.

[0023] The number 4 can be encoded with 2 bits, making it advantageous for a very large number of cells. The number 8 can be encoded with three bits, and the number 16 with four bits. This number of voltage sections allows for very efficient transmission. The number 8 is particularly suitable for large fuel cell stacks with, for example, 350-400 cells. The number 16 is suitable for significantly smaller fuel cell stacks or other energy storage and / or energy converters, such as those with up to 200 cells, as this increases both accuracy and the amount of data.

[0024] According to another optional configuration, the data is transmitted via a CAN bus. A CAN bus connection is frequently used in vehicles.

[0025] According to a further optional configuration, the data is divided into several CAN messages. The first CAN message contains the minimum and maximum single-cell voltages, and the remaining CAN messages contain information on the assignment of the voltage sections in the sequence of the cells of the energy storage device and / or energy converter.

[0026] This enables highly efficient data transmission. The receiver first requires the minimum and maximum individual cell voltages to determine the voltage ranges of the voltage sections. The data is then transmitted sequentially, following the order of the cells in the energy storage device and / or energy converter. This eliminates the need to transmit cell numbers, thus saving additional data.

[0027] According to another optional configuration, the first CAN message additionally includes the number of the cell with the minimum single-cell voltage and the number of the cell with the maximum single-cell voltage. These two cells are particularly important for monitoring. Therefore, it is advantageous to transmit this information explicitly.

[0028] According to another optional configuration, the first CAN message includes the average cell voltage. If the voltage ranges are determined based on the average cell voltage, the receiver first needs the minimum individual cell voltage, the maximum individual cell voltage, and the average cell voltage in order to determine the voltage ranges of the voltage sections. Therefore, it is advantageous to also transmit the average cell voltage explicitly.

[0029] According to another optional configuration, at least one, or in particular the first or every, of the CAN messages includes a checksum and a message counter. This protects the CAN messages against transmission errors and similar issues.

[0030] Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawings. These show: Fig. 1 a fuel cell stack, Fig. 2. A flowchart for sending information concerning cell voltages of cells of an energy storage device and / or energy converter and Fig. 3 an exemplary distribution of voltage sections.

[0031] The Fig. Figure 1 shows a fuel cell stack 10 as an example of an energy converter. A so-called Cell Voltage Monitor 15 is assigned to the fuel cell stack 10. The Cell Voltage Monitor 15 is configured to record the individual cell voltages of the cells in the fuel cell stack 10. Furthermore, the Cell Voltage Monitor 15 is configured to communicate with a control device 20, for example, via a CAN bus.

[0032] In automotive applications, the CAN bus with a transmission rate of 500 kbit / s is widely used and established. The transmission rate is limited, for example, to approximately 25 CAN messages with a 10 ms transmission period and 52 data bits each. This would allow, for instance, the transmission of a maximum of 125 individual cell voltages with full accuracy, assuming a range of 1000 mV per cell voltage and a resolution of 1 mV.

[0033] In the automotive sector, however, energy converters with a fuel cell stack containing around 350 to 400 cells, or even more than 400, are possible. One option would be to transmit not only the minimum, average, and possibly maximum cell voltages, but also selected individual cell voltages. However, this approach does not allow for monitoring all cells.

[0034] Another method would be to transmit block voltages, which combine several individual cells, rather than individual cell voltages, or not exclusively. However, this method would also not make it possible to monitor all cells.

[0035] Other measures would include limiting the update rate, for example through multiplexing, meaning that the individual cell voltages are transmitted in blocks and all the information is only fully available after several transmission cycles. While this would make it possible to monitor all cells, it would also make it difficult to react quickly to problems.

[0036] There are limits to reducing accuracy because the significance for assessing the condition of the fuel cell stack is greatly reduced.

[0037] A disadvantage of the above methods is a significantly limited ability to assess the current state of a fuel cell stack within a fuel cell system. Firstly, certain cells that are currently experiencing problems cannot be detected because they are not included in the catalog of measured cells. Secondly, larger buffer zones must be provided, thus restricting the usable power range of the stack, if the signal resolution is reduced too much. Reducing the update rate also limits the dynamics of the fuel cell stack.

[0038] The limitations of the information are significantly exacerbated when cells are grouped together and only the block voltage (= total voltage of the block) is transmitted, as there is a large degree of uncertainty in the calculation back to the individual cell voltages.

[0039] For some approaches, the transmission of the respective cell or block numbers is necessary in addition to the voltage values. This, in turn, consumes transmission capacity on the bus.

[0040] Fig. Figure 2 shows a flowchart of a program for sending information concerning cell voltages of cells of an energy storage device and / or energy converter in order to enable very efficient monitoring of an energy storage device and / or energy converter.

[0041] A device 1 is configured to execute a program for transmitting information concerning the cell voltages of cells in an energy storage device and / or energy converter. For this purpose, the device 1 includes, in particular, a processing unit, a program and data memory, and, for example, one or more communication interfaces. The program and data memory and / or the processing unit and / or the communication interfaces can be integrated into a single module and / or distributed across multiple modules.

[0042] The device 1 can also be referred to as device 1 for sending information concerning cell voltages of cells of an energy storage device and / or energy converter.

[0043] The device 1 is in particular designed in the Cell Voltage Monitor 15.

[0044] The program is stored in particular on the data and program memory of device 1.

[0045] The program is started in step S1, in which variables can be initialized if necessary.

[0046] In step S3, a single-cell voltage is determined for each cell of the energy storage device and / or energy converter.

[0047] In step S5, at least one reference single-cell voltage of the energy storage device and / or energy converter is determined, depending on the individual cell voltages.

[0048] For example, a minimum single-cell voltage of the energy storage device and / or energy converter is determined as a reference single-cell voltage. Alternatively or additionally, a maximum single-cell voltage of the energy storage device and / or energy converter is determined as a further reference single-cell voltage. Alternatively or additionally, an average single-cell voltage is determined as a further reference single-cell voltage.

[0049] In step S7, depending on the at least one reference single-cell voltage for a given number of voltage sections, limits of the given number of voltage sections are determined, whereby the voltage sections are each representative for a voltage range based on the at least one reference single-cell voltage.

[0050] For example, depending on the minimum and maximum single-cell voltages, the limits are determined for a given number of voltage sections, where each voltage section is representative of a voltage range between the minimum and maximum single-cell voltages. The given number of voltage sections might be, for example, 8 or 16.

[0051] Optionally, depending on the individual cell voltages, an average single cell voltage can be determined, and the limits can be determined depending on the minimum single cell voltage, the maximum single cell voltage, and the average single cell voltage.

[0052] The voltage range of the voltage sections can be relative and / or absolute. Furthermore, the voltage ranges can have different magnitudes.

[0053] The following distribution can be chosen as an example, as it appears in Fig. Figure 3 is shown. The initial conditions are, for example, a measuring range of 1000 mV per cell, a maximum resolution of critical cell voltages of 1 mV, and a number of voltage sections of 8.

[0054] The voltage sections are determined as follows, for example: Voltage section 0: Ucell,min ≤ Ucell ≤ UzoneO,max, Voltage section 1: UzoneO,max < Ucell ≤ Uzone1,max, Voltage section 2: Uzone1,max < Ucell ≤ Uzone2,max, Voltage section 3: Uzone2,max < Ucell ≤ Uzone4,min, Spannungsabschnitt 4: Uzone4,min < Ucell ≤ Uzone4,max, Voltage section 5: Uzone4,max < Ucell ≤ Uzone6,min, Spannungsabschnitt 6: Uzone6,min < Ucell ≤ Uzone7,min und Spannungsabschnitt 7: Uzone7,min < Ucell ≤ Ucell,max, where UzoneO,max = Ucell,min + min (2 mV; 1 % dMin), Uzone1,max = Ucell,min + min (10 mV; 5% dMin), Uzone2,max = Ucell,min + min (50 mV; 25% dMin), Uzone4,min = Ucell,ave - min (30 mV; 15% dMin), Uzone4,max = Ucell,ave + min (30 mV; 15% dMin), Uzone6,min = Ucell,max - min (10 mV; 5% dMax) und Uzone7,min = Ucell,max - min (2 mV; 1 % dMax), where dMin = Ucell,ave - Ucell,min and dMax = Ucell,max - Ucell,ave, where Ucell,min is the minimum single-cell voltage, Ucell,max is the maximum single-cell voltage and Ucell,ave is the average single-cell voltage.

[0055] In step S9, the cells of the energy storage device and / or energy converter are assigned to the voltage sections based on their individual cell voltages. This assignment is made, for example, into the voltage sections described above and in... Fig. 3 voltage sections shown, where Ucell is the single-cell voltage of a respective cell.

[0056] In step S11, data is sent that includes information about the assignment of the voltage sections. This data is sent, for example, to the control device 20.

[0057] The data is transmitted, for example, via a CAN bus. Specifically, the data is divided into several CAN messages. The first CAN message contains the minimum and maximum cell voltages, while the remaining CAN messages contain information about the assignment of voltage ranges in the sequence of the cells in the energy storage device and / or energy converter. Optionally, the first CAN message also includes the cell number with the minimum and maximum cell voltages. Optionally, the first CAN message can also include the average cell voltage. Optionally, each CAN message can include a checksum and a message counter.

[0058] For example, the following structure of the CAN messages results.

[0059] If each CAN message is secured with the checksum “Cyclic Redundancy Check”, CRC, (8 bits) and the message counter “Alive Rolling Counter”, ARC, (4 bits), 52 usable bits remain per message.

[0060] The first CAN message includes the mean single-cell voltage (Ucell,ave) (10 bits), the minimum single-cell voltage (Ucell,min) (10 bits), the number of the cell with minimum single-cell voltage (9 bits), the maximum single-cell voltage (Ucell,max) (10 bits), the number of the cell with maximum single-cell voltage (9 bits total) and thus a total of 48 bits.

[0061] With eight voltage sections, 3 data bits are required per cell on the CAN bus, since a number from 0 to 7 must be transmitted for each cell, corresponding to its assignment to a voltage section. The subsequent CAN messages can therefore transmit 17 cell voltages, with one bit remaining unused (17 x 3 + 1 = 52). Thus, together with the first CAN message, information for 408 cells (24 x 17) can be transmitted in 25 CAN messages. Alternatively, if the unused bit and the free space in the first CAN message are included, information for up to 411 cells can be transmitted.

[0062] This allows information on all cells in typical vehicle fuel cell stacks to be transmitted at a rate of 10 ms with a weighted resolution of the signals, ensuring a complete, fast and accurate assessment of the current state of the fuel cell stack.

[0063] In step S13, the program is terminated and can be restarted in step S1 if necessary.

[0064] By transmitting information about the assignment of voltage sections instead of the individual cell voltages, the data required for monitoring the energy storage and / or energy converter can be transmitted very efficiently using the method described above, thus enabling very efficient monitoring of the energy storage and / or energy converter.

[0065] The voltage intervals can be defined arbitrarily (relative, absolute, mixed relative / absolute, etc.). They simply need to be identical and known at both the sender and the receiver. The number of voltage intervals is also, in principle, freely selectable. The division into eight voltage intervals, with their 3 bits, fits well within the available bandwidth of the CAN bus. For stacks with significantly fewer cells, 16 voltage intervals can be represented, for example, with 4 bits each. Furthermore, the method can also be used if information is to be transmitted not for all cells, but only for selected ones. In this case, one would have the freedom to either increase the accuracy by using a higher number of voltage intervals or to use the freed-up capacity for other information.For the evaluation, it can be specified whether a mean value of the voltage sections or, following the worst-case scenario, a critical boundary value is used as the reference single-cell voltage. All zone voltages can be used as a plausibility check for the determined mean single-cell voltage value.

[0066] Instead of the minimum single-cell voltage, the maximum single-cell voltage, or the average single-cell voltage, other parameters can also be defined. In principle, the entire method can also be used for the transmission of battery cell voltages, for example in battery electric vehicles, or for other energy storage devices and / or energy converters with a cell structure.

[0067] The described method, by combining three times the data compression, enables the transmission of information on all cells, for example, of a fuel cell stack installed in a vehicle, via a standard CAN bus (500 kbit / s) without any loss of the required resolution. This allows the fuel cell system to be operated within wider limits and thus with increased power. Reference symbol list S1-S13 steps 1 Device 10 fuel cell stacks 15 Cell Voltage Monitor 20 Control device

Claims

[1] Method for transmitting information concerning cell voltages of cells of an energy storage device and / or energy converter, wherein - a single-cell voltage is determined for each cell of the energy storage device and / or energy converter, - depending on the individual cell voltages, at least one reference single-cell voltage of the energy storage device and / or energy converter is determined, - depending on the at least one reference single-cell voltage for a given number of voltage sections, limits of the given number of voltage sections are determined, whereby the voltage sections are each representative of a voltage range based on the at least one reference single-cell voltage, - the cells of the energy storage device and / or energy converter are assigned to the voltage sections depending on the individual cell voltages, - Data is sent that includes information on the allocation of the voltage sections. [2] The method of claim 1, wherein - a minimum single-cell voltage of the energy storage device and / or energy converter is determined as a reference single-cell voltage, - a maximum single-cell voltage of the energy storage device and / or energy converter is determined as a further reference single-cell voltage and - depending on the minimum single-cell voltage and the maximum single-cell voltage for the specified number of voltage sections, the limits of the specified number of voltage sections are determined, whereby the voltage sections are each representative for a voltage range between the minimum single-cell voltage and the maximum single-cell voltage. [3] Method according to claim 2, wherein an average single-cell voltage is determined as a further reference single-cell voltage and the limits of the predetermined number of voltage sections are determined depending on the minimum single-cell voltage, the maximum single-cell voltage and the average single-cell voltage. [4] Method according to claim 2 or 3, wherein the voltage range of at least one of the voltage sections is relative to the minimum single-cell voltage or the maximum single-cell voltage. [5] Method according to any of the preceding claims, wherein the stress range of at least one of the stress sections is absolute. [6] Method according to any one of claims 2 to 5, wherein at least two of the stress sections have stress areas of different sizes. [7] Method according to any of the preceding claims, wherein the specified number of voltage sections is 4, 8 or 16. [8] Method according to a preceding claim wherein the data are sent via a CAN bus. [9] Method according to claim 8, wherein the data are split into several CAN messages and the first CAN message includes the minimum single-cell voltage and the maximum single-cell voltage and the remaining CAN messages contain the information for the assignment of the voltage sections in the sequence of the cells of the energy storage device and / or energy converter. [10] Method according to claim 9, wherein the first CAN message additionally includes the number of the cell which has the minimum single-cell voltage and the number of the cell which has the maximum single-cell voltage. [11] Method according to claim 9 or 10, in reference to claim 3, wherein the first CAN message comprises the mean cell voltage. [12] Method according to one of claims 9, 10 or 11, wherein at least one of the CAN messages comprises a checksum and a message counter. [13] Device for transmitting information concerning cell voltages of cells of an energy storage device and / or energy converter, wherein the device is configured to perform a method according to one of the preceding claims.

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