JP2015125036A - Battery internal state estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery internal state estimation device that suppresses the increase in calculation load and can accurately estimate the internal state of a battery while reflecting the temperature distribution of cells constituting the battery.SOLUTION: The estimation device creates an equivalent circuit model that uses the temperature distribution of cells 11a constituting the battery 11 as a standard deviation and models the same standard deviation with a smaller number of cells (number of equivalent circuits). Inter-terminal voltage V1 is estimated using the equivalent circuit model, and the inter-terminal voltage of the whole battery is determined on the basis of each obtained estimation value and is applied to the control of a motor 3 and the cooling control of the battery 11.

Description

  The present invention relates to a battery internal state estimation device.

In order to improve the efficiency of an engine vehicle equipped with an engine as a conventional driving power source, a hybrid electric vehicle equipped with a motor as a driving power source in addition to the engine, or an electric vehicle equipped with a motor instead of the engine Etc. (hereinafter may be collectively referred to as an electric vehicle).
In such an electric vehicle, a battery is mounted as a power source of the motor, and the characteristics of the battery, for example, the maximum current that can be input and output are large depending on various conditions such as the state of charge (SOC) of the battery. It is known to fluctuate. Therefore, to prevent excessive input / output to / from the battery and to utilize the limited battery capacity to the maximum extent to drive the motor, it is necessary to consider the internal state of the battery that changes momentarily according to these conditions. There is.

  Therefore, an electrical equivalent circuit is created by replacing the main components of the battery with parameters such as resistance and inductance. Based on this equivalent circuit, the voltage between the terminals of the battery, the SOC, etc. are predicted to control the motor side. The technique to apply is proposed (for example, refer patent document 1). In the technique of Patent Document 1, the inter-terminal voltage, the SOC, and the like are estimated based on the generated equivalent circuit, and the actual inter-terminal voltage and the SOC are detected in parallel therewith. The estimated values are successively applied to the motor-side control while the parameters of the equivalent circuit are sequentially matched and optimized based on the comparison result between the estimated values and the actually measured values.

International Publication No. 2011/118080

  Incidentally, the resistance and inductance of the equivalent circuit change not only with the SOC of the battery but also with the temperature of each cell constituting the battery. However, in the technique of Patent Document 1, the cell temperature is reflected in the equivalent circuit by sequentially matching each parameter of the equivalent circuit based on the comparison result with the actual measurement value, but the temperature variation in the battery is reflected. As a result, there is a problem that an appropriate estimated value in accordance with the internal state of the battery cannot be derived.

  In addition, many cells in the battery pack are cooled by water or air, but all the cells are not evenly cooled, and there is always a temperature difference between the cells. Considering this point, if equivalent circuits are generated for all cells, the calculation load increases due to the calculation processing in those equivalent circuits, and a high calculation capacity and a large capacity memory are required. End up. In order to simplify the calculation process, when an estimated value is derived from an equivalent circuit based on a single representative value obtained by averaging the temperatures of each cell, for example, for a low temperature side cell or a high temperature side cell, There is a problem that the estimated value becomes inappropriate and appropriate motor control cannot be expected.

  The present invention has been made to solve such a problem, and the object of the present invention is to suppress an increase in calculation load and reflect the temperature distribution of each cell constituting the battery. An object of the present invention is to provide a battery internal state estimation device capable of estimating an internal state with high accuracy.

  In order to achieve the above object, an internal battery state estimation device of the present invention is based on the temperature distribution of a plurality of cells constituting a battery, and an equivalent circuit model composed of a plurality of equivalent circuits expressing the temperature distribution with a smaller number of cells. Equivalent circuit model means, and internal state estimation means for estimating the internal state of the entire battery based on each estimated value obtained using the equivalent circuit model of the equivalent circuit model possessing means. .

  According to the present invention, it is possible to estimate the internal state of the battery with high accuracy by reflecting the temperature distribution of each cell constituting the battery while suppressing an increase in calculation load.

1 is an overall configuration diagram showing a hybrid truck on which a battery internal state estimating device of an embodiment is mounted. It is explanatory drawing which shows the temperature distribution (left side) of all the cells of a battery, and the equivalent circuit model (right side) which modeled temperature distribution. It is a schematic diagram which shows an example of an equivalent circuit. It is explanatory drawing which shows the processing flow from the estimation process based on an equivalent circuit model to motor control.

Hereinafter, an embodiment in which the present invention is embodied in a hybrid truck battery internal state estimating device will be described.
FIG. 1 is an overall configuration diagram showing a hybrid truck on which the battery internal state estimating device of this embodiment is mounted.
The hybrid truck 1 is configured as a so-called parallel hybrid vehicle, and may be referred to as a vehicle in the following description. A vehicle 1 is equipped with a diesel engine (hereinafter referred to as an engine) 2 as a driving power source and a motor 3 that can also operate as a generator such as a permanent magnet synchronous motor. A clutch 4 is connected to the output shaft of the engine 2, and an input side of the automatic transmission 5 is connected to the clutch 4 via a rotating shaft of the motor 3. A differential device 7 is connected to the output side of the automatic transmission 5 via a propeller shaft 6, and left and right drive wheels 9 are connected to the differential device 7 via a drive shaft 8.

  The automatic transmission 5 automates the connection / disconnection operation of the clutch 4 and the switching operation of the shift stage based on a general manual transmission. In this embodiment, the automatic transmission 5 has a shift stage of 12 forward speeds and 1 reverse speed. ing. Of course, the configuration of the transmission 5 is not limited to this, and can be arbitrarily changed. For example, the transmission 5 may be embodied as a manual transmission, or a so-called dual clutch automatic transmission having two power transmission systems. It may be embodied as a machine.

  A battery 11 is connected to the motor 3 via an inverter 10. The DC power stored in the battery 11 is converted into AC power by the inverter 10 and supplied to the motor 3 (power running control), and the driving force generated by the motor 3 is transmitted to the drive wheels 9 after being shifted by the automatic transmission 5. The vehicle 1 is made to travel. For example, when the vehicle 1 decelerates or travels on a downhill road, the motor 3 operates as a generator by reverse driving from the drive wheel 9 side (regenerative control). The negative driving force generated by the motor 3 is transmitted to the driving wheel 9 side as a braking force, and the AC power generated by the motor 3 is converted into DC power by the inverter 10 and charged to the battery 11.

  The driving force generated by the motor 3 is transmitted to the driving wheel 9 regardless of the state of connection / disconnection of the clutch 4, and the driving force generated by the engine 2 is driven only when the clutch 4 is connected. 9 side. Therefore, when the clutch 4 is disengaged, the positive or negative driving force generated by the motor 3 as described above is transmitted to the driving wheel 9 side, and the vehicle 1 travels. When the clutch 4 is connected, the driving force of the engine 2 and the motor 3 is transmitted to the driving wheel 9 side, or only the driving force of the engine 2 is transmitted to the driving wheel side, so that the vehicle 1 travels.

The vehicle ECU 13 is a control circuit for integrated control of the entire vehicle. For this purpose, the vehicle ECU 13 includes an accelerator sensor 15 that detects the operation amount θacc of the accelerator pedal 14, a brake switch 17 that detects the depression operation of the brake pedal 16, a vehicle speed sensor 18 that detects the speed V of the vehicle 1, and the rotation of the engine 2. Various sensors and switches such as an engine rotation speed sensor 19 for detecting the speed Ne and a motor rotation speed sensor 20 for detecting the rotation speed Nm of the motor 3 are connected.
The vehicle ECU 13 is connected with an actuator (not shown) for connecting / disconnecting the clutch 4, an actuator for operating the automatic transmission 5 and the like, and an engine ECU 22 for engine control and an inverter ECU 23 for inverter control. And a battery ECU 24 for managing the battery 11 are connected.

  The vehicle ECU 13 calculates a required torque necessary for the vehicle 1 to travel based on the accelerator operation amount θacc by the driver, and selects a travel mode of the vehicle 1 based on the required torque, the SOC of the battery 11, and the like. In this embodiment, an E / G mode that uses only the driving force of the engine 2, an EV mode that uses only the driving force of the motor 3, and an HEV mode that uses both the driving force of the engine 2 and the motor 3 are set as the traveling mode. The vehicle ECU 13 selects one of the travel modes.

  The vehicle ECU 13 converts the required torque into a torque command value to be output by the engine 2 or the motor 3 based on the selected travel mode. For example, in the HEV mode, the required torque is distributed to the engine 2 side and the motor 3 side, and torque command values for the engine 2 and the motor 3 are calculated based on the gear position at that time. In the E / G mode, the required torque is converted into a torque command value for the engine 2 based on the gear position, and in the EV mode, the required torque is converted into a torque command value for the motor 3 based on the gear speed.

  Then, the vehicle ECU 13 disconnects the clutch 4 in the EV mode and connects the clutch 4 in the E / G mode and HEV mode in order to execute the selected travel mode, and then sends a torque command value to the engine ECU 22 and the inverter ECU 23. Output as appropriate. While the vehicle 1 is traveling, the vehicle ECU 13 calculates a target gear position from a shift map (not shown) based on the accelerator operation amount θacc, the vehicle speed V, and the like, and the actuator 4 connects and disconnects the clutch 4 to achieve this target gear position. Executes operation and gear change operation.

  On the other hand, the engine ECU 22 executes injection amount control and injection timing control so as to achieve the travel mode and torque command value input from the vehicle ECU 13. For example, in the E / G mode and the HEV mode, the driving force is generated in the engine 2 with respect to the positive torque command value, and the engine brake is generated with respect to the negative torque command value. In the EV mode, the engine 2 is brought into a stopped holding state or an idle operation state by stopping fuel injection.

  Further, the inverter ECU 23 controls the motor 3 via the inverter 10 so as to achieve the travel mode and the torque command value input from the vehicle ECU 13. For example, in the EV mode or HEV mode, the motor 3 is controlled by powering the positive torque command value to generate a positive driving force, and the motor 3 is regeneratively controlled to the negative torque command value. Generate negative driving force. In the E / G mode, the driving force of the motor 3 is controlled to zero. Further, the battery ECU 24 detects the temperature of the battery 11, the voltage of the battery 11, the current flowing between the inverter 10 and the battery 11, etc., and sequentially calculates the SOC of the battery 11 from these detection results and outputs it to the vehicle ECU 13. To do.

By the way, as described in [Background Art], the maximum current that can be input and output from the battery 11 greatly varies depending on various conditions such as the SOC and the temperature of each cell constituting the battery 11. Excessive input / output exceeding the maximum current causes early deterioration of the battery 11, and conversely limiting the input / output excessively means that a limited battery capacity cannot be effectively used for driving the motor.
For this reason, when the vehicle ECU 13 calculates the torque command value of the motor 3, it is necessary to reflect the battery characteristics that change according to the SOC, the cell temperature, and the like. Therefore, in the present embodiment, as in the technique of Patent Document 1, an electrical equivalent circuit that simulates the internal state of the battery 11 is generated, and the terminal voltage and SOC of the battery 11 are estimated based on the equivalent circuit. This is applied to the calculation process of the torque command value of the motor 3.

  As described in [Problems to be Solved by the Invention], the technique of Patent Document 1 reflects the measured cell temperature in the equivalent circuit even though the temperature distribution exists in the battery pack. Therefore, there is a problem that an appropriate estimated value cannot be derived. Also, if the equivalent circuit is generated corresponding to all cells in consideration of the temperature of each cell constituting the battery 11, the calculation load increases. Conversely, the temperature of each cell is set to simplify the calculation process. If an averaged single representative value is applied to an equivalent circuit, the estimated value becomes inappropriate.

In view of such a problem, the present inventor has found that the calculation process of the estimated value based on the equivalent circuit can be simplified by modeling the temperature distribution of each cell constituting the battery 11.
The left side of FIG. 2 is an explanatory diagram showing the temperature distribution of all cells of the battery 11, and the right side is an explanatory diagram of an equivalent circuit model composed of a plurality of equivalent circuits modeling the temperature distribution. As shown in the figure on the left side, a large number of cells 11a constituting the battery 11 are distributed in a temperature distribution according to the cooling state by the cooling medium (water or air) in the battery pack. In this case, the number of cells There will be a number of equivalent circuits corresponding to. The figure on the right side shows such a model in which the temperature distribution of all the cells 11a is regarded as a standard deviation and the same standard deviation is expressed by a smaller number of cells (number of cells 11b = number of equivalent circuits). It is. As shown in FIG. 2, the number of cells 11b is smaller than the number of all cells 11a.

  In this example, the number of cells is set to 10, and the temperature range is divided into five, and the cells 11a are grouped for each temperature range. As a result, four grouped cells 11b belong to the central temperature range corresponding to the average value, two cells 11b belong to the temperature ranges on both sides, and one to each temperature range. Cell 11b belongs. In the present embodiment, the equivalent circuit model is generated using the standard deviation as an index. However, the present invention is not limited to this as long as it is an index representing the temperature distribution of each cell 11a, and may be arbitrarily changed to another index.

  Since the behavior with respect to the temperature change of each cell 11a belonging to each temperature range is common, a total of five equivalent circuits are generated corresponding to each temperature range. In the present embodiment, the temperature distribution of all the cells 11a of the battery 11 is specified by a prior test, an equivalent circuit model is generated in advance from the temperature distribution and stored in the battery ECU 24, and the battery ECU 24 is based on the equivalent circuit model. An estimation process is performed (equivalent circuit model holding means, internal state estimation means).

FIG. 3 is a schematic diagram showing an example of an equivalent circuit when the element of the steady internal resistance of the battery 11 is replaced with Rs, the element of the transient internal resistance is replaced with R1, C1, and the load is set to zero. The voltage element corresponding to the open circuit is replaced with Vocv. It is assumed that these parameters Rs, R1, C1, and Vocv change according to the SOC of the battery 11 and the cell temperature T, and each parameter is set as a function of the SOC and the cell temperature T. A voltage V1 between terminals of the cell 11a (hereinafter simply referred to as a cell voltage) is sequentially estimated from the circuit.
The contribution of the cell voltage V1 estimated from the equivalent circuit in each temperature range to the inter-terminal voltage of the entire battery (hereinafter simply referred to as the battery voltage) differs depending on the number of cells belonging to that temperature range. For this reason, the battery voltage is calculated from the cell voltage V1 of each equivalent circuit based on the weighting according to the number of cells.

  Also in the present embodiment, as in the technique of Patent Document 1, the voltage V1 and SOC of each cell 11a that are sequentially estimated are compared with actual measurement values, and each parameter of the equivalent circuit is sequentially adjusted based on the comparison result. We are trying to optimize. For this purpose, although not shown, each cell 11a is provided with a voltage sensor in the battery pack, and the measured value of the cell voltage V1 detected by each voltage sensor is sequentially compared with the estimated value of the same cell 11a. It is.

  FIG. 4 is an explanatory diagram showing a processing flow from estimation processing based on an equivalent circuit model to motor control. A battery voltage calculation process based on the above equivalent circuit model is executed by the battery ECU 24, and simultaneously, an SOC calculation process based on the battery voltage and the like is also executed, and these estimated values are input to the vehicle ECU 13. Various information such as a driver's required torque is also input to the vehicle ECU 13, and torque command values on the engine 2 side and the motor 3 side obtained from the information are output to the engine ECU 22 and the inverter ECU 23 and applied to each control. .

  At this time, the maximum current that can be output by the battery 11 is also determined according to the battery voltage estimated by the battery ECU 24, and the torque command value to the motor 3 side is determined within the range of the maximum current. Further, since the change in the maximum current that can be output can be predicted based on the state of change in the battery voltage that is sequentially estimated, for example, the current can be quickly limited to prevent troubles such as excessive heat generation of the battery 11. Note that the division of roles between the vehicle ECU 13 and the battery ECU 24 is not limited to this. For example, the battery ECU 24 and the vehicle ECU 13 may be integrated to form a single control circuit.

  On the other hand, apart from the equivalent circuit model for estimating the cell voltage V1, the equivalent circuit model for estimating the cell temperature T is also generated in advance and stored in the battery ECU 24. Since the contents of the equivalent circuits constituting the equivalent circuit model are the same as those shown in FIG. 3 and are not shown, the battery ECU 24 sequentially estimates the temperature T of each cell 11a based on those equivalent circuits. The same applies to the point that each parameter of the equivalent circuit is sequentially adjusted by comparing the estimated cell temperature T with the actual measurement value of the same cell 11a. For this purpose, each cell 11a is provided with a temperature sensor. ing.

  The cell voltage V1 and the cell temperature T estimated by both equivalent circuits are mutually used for the common cell 11a, and the sequentially estimated cell voltage V1 is the cell temperature T for the same cell 11a. The cell temperature T, which is used for the estimation process and sequentially estimated, is used for the cell voltage V1 estimation process for the same cell 11a. By repeating such mutual use of estimated values, the estimation accuracy is improved.

  As described above, in this embodiment, not only the cell temperature T of the battery 11 is reflected in the equivalent circuit, but also the temperature distribution of all the cells 11a is regarded as a standard deviation, and the same standard deviation is expressed by a smaller number of cells. An equivalent circuit model composed of a plurality of equivalent circuits is generated. For this reason, it is not necessary to generate an equivalent circuit corresponding to all the cells 11a, and the calculation load required for the estimation process of the battery voltage and the like can be significantly reduced as the equivalent circuit decreases.

  Compared with the case where an estimated value such as a battery voltage is derived based on a single representative value obtained by averaging the temperature T of each cell 11a, a much more accurate estimated value can be calculated, and the control on the motor 3 side is further increased. It can be done properly. That is, since the battery voltage is calculated based on the cell voltage V1 estimated from the equivalent circuit in all temperature ranges modeled, the obtained battery voltage is an estimated value reflecting the entire temperature range. And since the torque command value to the motor 3 side is appropriately limited based on the maximum current derived from the battery voltage, the cell 11a belonging to both extreme temperature ranges (low temperature side and high temperature side) under severe temperature conditions. However, the maximum current that can be input and output, in other words, the appropriate current without excess or deficiency can be applied to the motor control.

When an estimated value such as a battery voltage is derived from a single representative value, there is no confirmation that the current value is appropriate for both extreme cells 11a. In addition, the current limit to the motor 3 is started early in anticipation of safety. This is a factor such as deterioration in fuel efficiency because the capabilities of the motor 3 and the battery 11 cannot be utilized to the maximum, but according to the present embodiment, such a situation can be prevented.
Further, as a result, the time during which the battery 11 is exposed to a high temperature is suppressed to a minimum, so that the battery 11 can be extended in life, and the battery capacity that is assumed to be deteriorated can be reduced to reduce the size and weight and reduce the cost. Can be achieved.

  Furthermore, the point at which the accurate cell temperature T can be estimated leads to the cooling control of the battery 11 without waste, and for example, the flow rate control of water or air as a cooling medium can be finely executed. For this reason, energy consumed for cooling, for example, driving power of a pump or a fan, can be saved to the minimum necessary, and as a result, further reduction in fuel consumption can be achieved.

As described above, in the present embodiment, an equivalent circuit model is generated from the temperature distribution of all the cells 11a of the battery 11 and stored in the battery ECU 24 in advance by a preliminary test. However, the present invention is not limited to this.
Since each cell 11a of the battery 11 is provided with a temperature sensor, the temperature distribution of each cell 11a can be specified in real time even during operation of the vehicle based on detection information from these temperature sensors. Therefore, an equivalent circuit model may be sequentially generated during vehicle operation based on the identified temperature distribution of each cell 11a and applied to the cell voltage V1 estimation process. Although the temperature distribution of each cell 11a varies depending on the cooling conditions in the battery pack (for example, the flow state of water or air), the cell temperature T can be estimated based on a corresponding equivalent circuit model. Therefore, in this case, a more accurate estimation process can be realized without being affected by external factors such as cooling conditions.

  Further, when an equivalent circuit model is generated and stored in advance as in the embodiment, the equivalent circuit model may be switched according to different cooling conditions in the battery pack. In this case, a plurality of equivalent circuit models corresponding to the cooling condition may be generated and stored in advance, and an equivalent circuit model corresponding to the cooling condition at that time may be selected and applied to the estimation process.

This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the battery internal state estimation device for a hybrid truck is embodied, but the battery internal state estimation device for an electric vehicle equipped with only a motor as a driving power source may be used. You may embody as an internal state estimation apparatus of the stationary battery with which the electric power generation system was equipped.
Moreover, in the said embodiment, although the estimation process of the cell temperature T was performed in parallel with the estimation process of the cell voltage V1, it is not restricted to this, For example, the estimation process of the cell temperature T may be abbreviate | omitted.

11 battery 11a, 11b cell 24 battery ECU (equivalent circuit model holding means, internal state estimating means)

Claims (1)

Based on the temperature distribution of a plurality of cells constituting the battery, an equivalent circuit model holding means for holding an equivalent circuit model composed of a plurality of equivalent circuits expressing the temperature distribution with a smaller number of cells;
An internal battery state estimation device comprising: internal state estimation means for estimating an internal state of the entire battery based on estimated values obtained using an equivalent circuit model of the equivalent circuit model holding means.

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