Method for thermal monitoring of a battery junction box and battery management control unit

Abstract

The invention relates to a method for thermally monitoring a battery junction box (3) by means of a battery management control unit (4), wherein the battery junction box (3) comprises switching elements (5), at least one fuse (6) and at least one current sensor (7), wherein the battery management control unit (4) comprises at least one reduced 3D CFD model (10) of the battery junction box (3), wherein at least the current (I) is input as an input variable (E) into the reduced 3D CFD model (10), and wherein the output variables are temperature values ​​(T). i ) of the elements of the battery junction box (3) are wherein the battery management control unit (4) the determined temperature values ​​(T i ) for the elements, each with at least one threshold value (T i,s ) compares and, if a threshold value (T) is exceeded, i,s) generates a warning message and / or initiates a countermeasure to reduce the temperature, as well as a battery management control unit (4).

Description

[0001] The invention relates to a method for thermal monitoring of a battery junction box and a battery management control unit for an electric or hybrid vehicle.

[0002] Electric and hybrid vehicles have a high-voltage battery and a battery junction box, also known as a PDU (Power Distribution Unit). The battery junction box is typically a switching box that connects and disconnects the high-voltage connections. For this purpose, the battery junction box contains switching elements such as contactors or semiconductor switches. Additionally, fuses are provided, which are, for example, designed as cartridge fuses and / or pyrolytic fuses. Furthermore, a battery junction box typically has at least one current sensor, which is, for example, designed as a shunt resistor or Hall sensor. The switching elements of the battery junction box are controlled by a battery management system (BMS).

[0003] The traction battery consists of a large number of battery cells or storage cells. The temperature of these storage cells is a critical parameter that must be monitored accordingly.

[0004] From DE 10 2020 203 004 A1 a method for monitoring an electrical energy storage device is known, which has several storage cells and a cooling system assigned to the storage cells and through which a cooling medium flows for the removal of heat from the storage cells, and the following steps: a) Generating a numerical model of the energy storage system to determine the temperature of each storage cell, b) Where the memory cells are represented by a thermal, linear sub-model of the respective memory cell, c) And where the cooling system is represented by a thermal, non-linear sub-model, d) Reducing the linear submodel from step b) by at least one linear model reduction method, e) Reducing the non-linear sub-model from step c) by at least one non-linear reduction method, f) Forming a reduced model from the sub-models generated in steps d) and e) to determine the temperature values ​​of each storage cell, g) Comparing the temperature values ​​determined in step f) with one or more predetermined limit values ​​and initiating a safety measure if one of the determined temperature values ​​deviates from the corresponding limit value beyond a predetermined extent.

[0005] Preferably, in step b), the power loss of each storage cell is determined as waste heat, at least as a function of the temperature of the respective storage cell, its electrical state of charge, and the load current applied to the respective storage cell. By determining the power loss, the heat flows of the respective storage cell can be advantageously determined and taken into account when determining the temperature values ​​of the respective storage cell. Optionally, when determining the power loss, the waste heat flows of other electrical / electronic components of the energy storage system are also considered, such as switching devices, contactors, resistors, fuses, and the battery management control unit, in order to determine the temperature of the storage cells more accurately.

[0006] From DE 10 2014 206 511 A1, a method for monitoring the condition of contactor contacts of a contactor controllable by means of an excitation coil is known. This contactor is operated as part of an isolation unit for the galvanic isolation of a voltage source from an electrical load connected to the voltage source. In this method, a first power loss dissipated via the contactor contacts and a second power loss dissipated via the excitation coil are determined. The first and second power losses are fed as input variables to a thermal model of the contactor. The thermal model determines a contactor temperature as a function of at least one of the input variables and provides this temperature as an output variable.

[0007] From DE 10 2018 210 411 A1 a method for checking a temperature value recorded in a battery system is known, wherein the battery system has at least one temperature sensor, comprising the following steps: - Recording at least one temperature measurement using at least one temperature sensor, - Capturing and / or receiving at least one state value, - Estimating at least one temperature value using a reduced-order model based on the detected and / or received at least one state value, wherein the reduced-order model represents a thermal behavior of the battery system as a function of the at least one state value, - Verification of the recorded at least one temperature measurement based on the associated estimated at least one temperature value and derivation of verification information from the verification result and - Outputting or providing the verification information.

[0008] First, a CAD model of the battery system can be created, followed by several simulations using CFD simulation, with different combinations of state values ​​as boundary conditions for each simulation. The various results are then used to train a reduced-order model.

[0009] The invention is based on the technical problem of improving the thermal monitoring of a battery junction box.

[0010] The solution to the technical problem is achieved by a method having the features of claim 1 and a battery management control unit having the features of claim 5. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0011] The thermal monitoring of a battery junction box is performed using a battery management system (BMS). The BMS comprises switching elements, at least one fuse, and at least one current sensor. The BMS uses a simplified 3D CFD (Computational Fluid Dynamics) model of the BMS, with at least the current being input as an input variable. The output variables are the temperature values ​​of the BMS components. The BMS compares the measured temperature values ​​for each component against at least one threshold value. If a threshold value is exceeded, the BMS generates a warning message and / or initiates a countermeasure to reduce the temperature. For example, the current is reduced and / or the cooling capacity of a cooling system is increased.The invention is based on the understanding that the existing thermal monitoring of the battery junction box is insufficient, particularly when inferring the temperature values ​​of all elements from a single temperature reading. By determining the temperature values ​​for all elements of the battery junction box according to the invention, corrective action can now be taken much faster and more effectively if individual elements reach their thermal limits. A further advantage is that this also allows for better dimensioning of the cooling system's capacity.

[0012] The battery management control unit also contains an observer model that initializes the reduced 3D CFD model and adjusts the input parameters based on a real temperature measurement. This improves the accuracy of the temperature value determination.

[0013] The reduction of the 3D CFD model can be done in various ways.

[0014] One possibility is to reduce the 3d CFD model using reduced-order modeling methods so that it can be run on the battery management control unit.

[0015] Instead of reduced-order modeling methods, a 0d / 1d point mass model can also be built in Matlab / Simulink and then converted into a functional mock-up unit (FMU). This approach can also be used to reduce a non-linear 3D CFD model.

[0016] Another possibility is to generate data using 3D CFD or to use data from measurements of the battery junction box to fit meta-models (e.g., response surface models, Kringing models, etc.) in order to create a suitable reduced model of the battery junction box.

[0017] However, the reduced-order model method is preferably used, since it is not a black-box model but a physical model that also reflects the properties of the original model. Furthermore, estimations of values ​​outside the fitting range are also possible because the model is stably extrapolable.

[0018] In one embodiment, additional input variables such as ambient temperature and / or coolant temperature and / or coolant flow rate are included in the reduced 3d CFD model, thus improving the determination of temperature values.

[0019] In another embodiment, the temperature is measured at an NTC shunt resistor of the battery junction box by assigning the determined resistance to a temperature.

[0020] In another embodiment, the observer model is designed as a Luenberger observer, a Kalman filter, or a sliding-mode observer.

[0021] Regarding the design of the battery management control unit, full reference is made to the preceding statements.

[0022] The invention is explained in more detail below with reference to a preferred embodiment. The figures show: Fig. 1 a highly schematic block diagram of a traction battery unit of an electric or hybrid vehicle and Fig. 2 a highly simplified flowchart of a procedure for generating a reduced 3d CFD model and its use for thermal monitoring of a battery junction box.

[0023] In the Fig. Figure 1 is a highly schematic representation of a traction battery unit 1 of an electric or hybrid vehicle. The traction battery unit 1 comprises the actual traction battery 2, a battery junction box 3, and a battery management control unit 4. The traction battery 2 consists of a multitude of battery cells or storage cells, which may be further grouped into battery modules. The battery cells are monitored by cell controllers (not shown), which are connected to the battery management control unit 4. The cell controllers may also be located in the battery junction box 3, but this is not mandatory. The cell controllers supply voltage and temperature values ​​of the battery cells to the battery management control unit 4. A method such as that described in DE 10 2020 203 004 A1 can be used to monitor the temperature of the battery cells.Not shown is a cooling system for the traction battery 2 and the battery junction box 3.

[0024] Depending on the design, the battery junction box 3 contains various switching elements 5, fuses 6, and at least one current sensor 7, which here is designed as a shunt resistor 8, with an NTC shunt resistor 9 connected in series. The battery junction box 3 can also include a variety of other switching elements 5 (e.g., pre-charging relays, relays for auxiliary units) and fuses 6.

[0025] The battery management control unit 4 includes, among other things, a reduced 3D CFD model 10 of the battery junction box 3 as an FMU or as C code. Furthermore, the battery management control unit 4 includes an observer model 11. Based on input variables such as the current I, the ambient temperature, a coolant temperature, and a coolant flow rate, the reduced 3D CFD model determines the temperature T. i (see Fig. 2) of all elements in the battery junction box 3, where these determined temperature values ​​T i with at least one threshold value T each i,s (see Fig. 2) are compared, whereby if a threshold value T is exceeded i,s Countermeasures such as reducing the current I and / or increasing the cooling capacity (e.g., by increasing the coolant flow rate) can be implemented. A temperature in the battery junction box 3 is measured via the NTC shunt resistor 9 and fed to the observer model 11. The observer model 11 can then perform a plausibility check of the determined temperature values ​​T. i perform the procedure and adjust the input variables if there are deviations, so that the determined temperature values ​​T i are more plausible (for example, an ambient temperature or current I is entered into the reduced 3d CFD model that is smaller or larger than transmitted).

[0026] In the Fig. Figure 2 is a highly simplified flowchart of a procedure for generating a reduced 3D CFD model and its use for thermal monitoring of a battery junction box 3 (see Fig. 1) is shown. In a first step S1, a 3D CFD model of the battery junction box 3 is created, taking into account the specific installation situation of the individual elements. In a second step S2, the 3D CFD model is then calibrated and validated using real measurement data. In a third step S3, a reduced 3D CFD model is derived (e.g., using reduced-order modeling methods) and in a fourth step S4, transferred to the battery management control unit 4 (e.g., into an FMU or as C code).

[0027] The dashed line indicates that the subsequent process steps for the thermal monitoring of a battery junction box 3 in the vehicle take place on the battery management control unit 4. In a fifth step S5, the reduced 3D CFD model reads 10 input variables E such as current I, ambient temperature, coolant temperature, and coolant flow rate and determines temperature values ​​T. i for all elements of the battery junction box 3, which are then validated using an observer model 11 (step S6). In a seventh step S7, the determined temperature values ​​T i with a threshold value T each i,s compared, whereby if a threshold value T is exceeded i,s In an eighth step, S8 countermeasures are initiated. It should be noted that monitoring can be carried out during charging and driving operations. Reference symbol list 1 traction battery unit 2 traction batteries 3 Battery Junction Box 4 Battery management control unit 5 switching element 6 fuse 7 Current sensor 9 NTC shunt resistor 10 3D CFD model 11 Observer Model T i Temperature values ​​of the elements T i,s threshold I Current intensity E Input size

Claims

[1] Method for thermal monitoring of a battery junction box (3) by means of a battery management control unit (4), wherein the battery junction box (3) has switching elements (5), at least one fuse (6) and at least one current sensor (7), wherein the battery management control unit (4) has at least one reduced 3D CFD model (10) of the battery junction box (3), wherein at least the current intensity (I) is input as an input variable (E) into the reduced 3D CFD model (10), wherein the output variables are temperature values ​​(T i ) of the elements of the battery junction box (3), whereby the battery management control unit (4) determines the temperature values ​​(T i ) for the elements each with at least one threshold value (T i,s ) and if a threshold value (T i,s) generates a warning message and / or initiates a countermeasure to reduce the temperature, wherein an observer model (11) is additionally stored in the battery management control unit (4), which observer model (11) initializes the reduced 3d CFD model (10) on the basis of an actually measured temperature and adapts the input variables (E). [2] Method according to claim 1, characterized by that an ambient temperature and / or a coolant temperature and / or a coolant volume flow are included as further input variables (E) in the reduced 3d CFD model (10). [3] Method according to one of the preceding claims, characterized by that the actual measured temperature is measured at an NTC shunt resistor (9) of the battery junction box (3). [4] Method according to one of the preceding claims, characterized by that the observer model (11) is designed as a Luenberger observer, as a Kalman filter or as a sliding mode observer. [5] Battery management control unit (4) for thermal monitoring of a battery junction box (3), wherein the battery management control unit (4) has a reduced 3D CFD model (10) of the battery junction box (3), wherein the battery management control unit (4) is designed to read at least one current intensity (I) into the reduced 3D CFD model (10) as an input variable, wherein temperature values ​​(T i ) of the elements of the battery junction box (3), wherein the battery management control unit (4) is further designed to convert the determined temperature values ​​(T i ) for the elements each with at least one threshold value (T i,s ) and if a threshold value (T i,s) to generate a warning message and / or to initiate a countermeasure to reduce the temperature, wherein an observer model (11) is additionally stored in the battery management control unit (4), which observer model (11) initializes the reduced 3D CFD model (10) on the basis of an actually measured temperature and adapts the input variables. [6] Battery management control device according to claim 5, characterized by that the battery management control unit (4) is further designed to read an ambient temperature and / or a coolant temperature and / or a coolant volume flow into the reduced 3D CFD model (10) as further input variables. [7] Battery management control device according to claim 5 or 6, characterized by that the battery management control unit (4) is designed to read the voltage of an NTC shunt resistor (9). [8] Battery management control device according to one of claims 5 to 7, characterized bythat the observer model (11) is designed as a Luenberger observer, as a Kalman filter or as a sliding-mode observer.

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