JP7264583B2 - Battery controller and battery system - Google Patents

Description

The present invention relates to battery control systems, battery packs, and battery systems.

When a lithium ion secondary battery is continuously subjected to a large load in a short period of time, a "high load resistance increase" in which the resistance rises significantly may occur. In order to suppress this "increase in high load resistance", a battery management system (hereinafter referred to as BMS) always calculates a battery load index indicating the magnitude and continuity of the battery load in the most recent time, and the calculated battery load Appropriately limit the battery load based on the index. However, since a control calculation blank period occurs while the BMS is stopped, it is necessary to appropriately limit the battery load based on the battery load index calculated in consideration of the control calculation blank period, that is, the BMS stop time immediately after the restart. .

As a conventional technology for calculating the BMS stop time, a method using a real time clock (hereinafter referred to as RTC) is generally used. In addition, Patent Document 1 discloses that the battery state index is calculated after the BMS stop period by periodically measuring the battery state during the BMS stop period.

JP 2014-126412 A

In order to suppress the increase in high load resistance, it is necessary to appropriately limit the battery load after starting the BMS, considering the blank period of control calculation while the BMS is stopped. and the technology disclosed in Patent Literature 1, there is a problem that the standby current increases because there are elements that are in operation even when the vehicle is not in operation. In addition, if the RTC is mounted, there is a risk that the component cost will increase, and there is a risk that appropriate current limiting cannot be performed when the RTC fails.

In order to solve the above problems, the battery control device according to the present invention limits the input/output power of the battery cells by using the temperature information of the battery cells and the temperature information different from the temperature information of the battery cells.

According to the present invention, input/output power can be limited even in situations where the BMS downtime cannot be used by the RTC (for example, the situation where the RTC is not installed or the RTC has failed). For another purpose, the battery load index immediately after restarting the BMS can be calculated even when the RTC is not installed or when the RTC is out of order.

FIG. 1 is a diagram showing the battery load index when the initial value at BMS restart is set to 0. FIG. FIG. 2 is a diagram showing changes in the battery load index when the initial value at the time of restarting the BMS is set to the previous value. FIG. 3 is a diagram showing temperature changes of the battery pack due to charging and discharging. FIG. 4 is a diagram showing an outline of the allowable power calculation block. FIG. 5 is a diagram showing BMS stop time estimation results in the first embodiment. FIG. 6 is a diagram showing BMS stop time estimation results in the second embodiment.

<<First Embodiment>>
Embodiments for carrying out the present invention will be described below with reference to the drawings.

A first embodiment will be described.

The vehicle BMS stores the battery load index when the vehicle is stopped (during processing when the vehicle was stopped last time), and when the vehicle is restarted (during processing when the vehicle is restarted), the battery load index is stored as the vehicle idle time ( Attenuation calculation must be performed according to the elapsed time from when the vehicle is stopped until when the vehicle is restarted. However, since the BMS board, which has strict restrictions on cost and standby power, does not have an RTC that acquires time information, it is not possible to acquire the vehicle downtime, and after the vehicle is restarted (the period after the vehicle is restarted) Calculating a correct battery load index is very difficult.

Therefore, it is conceivable to either reset the battery load index when the vehicle is restarted to 0 (FIG. 1) or substitute the battery load index when the vehicle was stopped last time (FIG. 2).

FIGS. 1(a) and 1(b) are diagrams for explaining data processing after resetting the battery load index to zero when the vehicle is restarted. As shown in FIGS. 1(a) and 1(b), the processing in the BMS can be roughly divided into a previous operating period A, a pause period B, and a current operating period C. FIG. In FIGS. 1A and 1B, the true value during the current operating period C is indicated by a solid line, and the battery load index obtained by resetting to 0 is indicated by a two-dot chain as an apparent value. In the case of FIG. 1A, in which the idle period B is long, the battery is in a steady state. Therefore, if the countermeasure is taken by resetting to 0 as in the present method, the true value and the apparent value are almost the same. On the other hand, in the case of FIG. 1B, in which the rest period B is short, the battery does not reach a steady state. will deviate in any direction. For this reason, there is a risk that even when power must be limited in order to suppress an increase in the high load resistance, the limitation will not be applied.

On the other hand, FIGS. 2A and 2B are diagrams for explaining data processing after substituting the battery load index when the vehicle is stopped again. In the case of FIG. 2(b), in which the idle period B is short, the battery does not reach a steady state. becomes. On the other hand, in the case of FIG. 2A, in which the idle period B is long, the battery is in a steady state. It deviates in the direction of increasing significantly. Therefore, if this method is adopted and the vehicle is stopped for a long time as shown in Fig. 2 (a), the apparent value of the battery load indicator after restarting the vehicle will be larger than the true value, so the limit is more than necessary. may be applied too much.

In other words, regardless of whether the battery load index is reset to 0 when the vehicle is restarted or the battery load index is substituted when the vehicle is stopped last time, either method is selected for a short period of rest or a long period of rest. The power cannot be appropriately limited corresponding to both cases.

For the above reasons, in the present invention, it is necessary to consider a new method for both short and long pauses.

Further, when a large load is continuously applied to the battery pack for a short period of time, the temperature at the center of the battery pack becomes higher than the environmental temperature due to heat generation or the like, resulting in a temperature difference. Data showing this temperature difference are shown in FIGS. 3(b) and 3(c). FIG. 3(a) schematically shows the battery pack 100. This battery pack 100 includes a battery pack center temperature sensor 200, a battery pack end side temperature sensor 210, and a battery pack housing internal temperature sensor 220. is placed to measure the temperature. FIG. 3(b) shows the correlation between charging/discharging time and battery temperature, and FIG. 3(c) shows the time dependence of battery pack edge temperature and battery pack center temperature after charging/discharging is stopped after charging/discharging for a predetermined time. It is a diagram. As shown in FIG. 3B, there is a large difference between the temperature at the center of the battery pack and the temperature at the ends of the battery pack. Further, as shown in FIG. 3(c), the temperature at the center of the battery pack and the temperature at the ends of the battery pack exponentially decay over time. In the present invention, these temperature characteristics are used to calculate the BMS stop time based on the temperature information immediately before the BMS is stopped and immediately after the BMS is restarted, thereby preventing an increase in the high load resistance.

FIG. 4 is a diagram for explaining the first embodiment of the battery management system according to the present invention. FIG. 4(a) is a diagram showing the battery system 10. FIG. The battery system 10 includes a battery pack 100 and a BMS 110 connected to the battery pack 100 and controlling the battery pack. This battery system 10 is connected to an inverter 120, and this inverter 120 is connected to a motor 130 to form a vehicle drive system.
FIG. 4B is an enlarged control block diagram of the BMS 110. FIG. Current information, voltage information, temperature information, charging rate information, and resistivity information acquired from the battery cells of the battery pack 100 via a cell controller (not shown) are input to the BMS 110 . The BMS 110 comprises a pre-restriction allowable power calculator 111 , a battery load index calculator 112 , a limit rate calculator 113 , and a post-limit allowable power calculator 114 . The pre-restriction allowable power calculation unit 111 is a block that calculates the allowable power that can be charged and discharged within the range of upper and lower voltage set values of the battery. The battery load index calculator 112 is a block that calculates a battery load index representing the magnitude and continuity of the battery load. The limit rate calculator 113 is a block that calculates the limit rate based on the battery load index. The post-restriction allowable power calculation unit 114 is a block that multiplies the pre-restriction allowable power by the limit rate to calculate the post-restriction allowable power. Current information, voltage information, temperature information, state-of-charge information, and resistivity information acquired via a cell controller (not shown) are input to the pre-restriction allowable power calculation unit 111 and the battery load index calculation unit 112, respectively. Calculate the aforementioned control parameters. The limit rate calculator 113 calculates the limit rate from the battery load index calculated by the battery load index calculator 112, voltage information, temperature information, and charging rate information. Then, the post-restriction allowable power calculation unit 114 calculates the post-control allowable power value from the parameter and the restriction rate calculated by the pre-restriction allowable power calculation unit 111 .

Next, a specific calculation method of the present invention will be described. As shown in FIG. 3(c), the temperature difference (ΔT) between the pack center temperature (T _center ) and the ambient temperature (T _amb ) immediately after the charge/discharge pause (t ₀ ) is exponentially attenuated with a time constant τ. In order to converge, the temperature difference (ΔT( _{t 0 )} = T _center (t ₀ ) - T _amb (t ₀ )) immediately after the charge/discharge pause (t 0 ) and the time point t _rest after the charge/discharge pause (t The relationship of the temperature difference (ΔT(t ₁ )=T _center (t ₁ )−T _amb (t ₁ )) at 1=t ₀ +t _rest ) is represented by _Equation (1).

By transforming equation (1), the elapsed time (t _rest ) can be obtained as in equation (2).

Equation (2) is used as the basic equation for estimating the vehicle down time in the present invention. However, since the estimated value of the vehicle idle time does not become an abnormal value, the temperature input in Equation (2) is the temperature sensor error (drift error, offset error variation between sensors), the resolution of the temperature sensor, and the vehicle idle time. Considering changes in environmental temperature (T _amb ), etc., it is necessary to satisfy the following constraints.
(A) The denominator component in the log function is a positive value (B) The numerator component in the log function is a positive value (C) The numerator component is greater than the denominator component in the log function (D ) Elapsed time (t _rest ) should be 0 or more. Therefore, it is preferable to perform the calculation by satisfying the constraint conditions for the above equation (2).

The result of verifying the accuracy using the present invention, that is, the result of verifying the accuracy of the vehicle idle time estimation algorithm when the BMS 110 can acquire the environmental temperature (T _amb ) will be described. At this time, _t0 was fixed at 0 sec.

From FIG. 5(a), it was confirmed that the estimated value of the vehicle idle time changed substantially on the true value line in the section of 10000 sec or less. From this result, it is possible to quantitatively estimate the vehicle idle time from the temperature information. Next, from FIG. 5(b), it was confirmed that the estimated value ratio of the vehicle down time changes on the reference line in the interval of 1000 seconds or longer where the battery pack temperature difference between time _t0 and time _t1 is large. Furthermore, in the interval of 1000 seconds or less where the temperature difference between the battery packs at time _t0 and time _t1 is small, the fluctuation range of the estimated value ratio of the vehicle stop time greatly exceeded the reference line. This calculation is performed by the battery load index calculator 112 . By using the present invention in this way, it is possible to accurately estimate the elapsed time since the vehicle stopped even when the RTC cannot be used, so that the battery load index can be calculated with high accuracy. Particularly in the region of 1000 seconds or more, the time from the vehicle stop can be estimated with high accuracy, and the battery load index can be calculated particularly with high accuracy.

In this embodiment, the difference between the temperature of the battery cell when the vehicle is stopped and the ambient temperature is used to estimate the time from when the vehicle is stopped, but it is also possible to use another temperature. For example, the battery cell temperature when the vehicle is stopped and the battery cell temperature when the vehicle is started may be used to estimate the elapsed time since the vehicle was stopped. Such a configuration eliminates the need for a temperature sensor for measuring the environmental temperature, so the battery pack can be made simple. As another example, information on the temperature of the battery cells when the vehicle is stopped and the temperature information inside the battery pack housing in which the battery cells are accommodated may be used to estimate the elapsed time since the vehicle was stopped. By adopting such a configuration, it is possible to complete this control as a single battery pack product.

Further, in the case of using the temperature information of the battery cells when the vehicle is started and the temperature information of the inside of the housing in which the battery cells are stored in this embodiment, the temperature information of the battery cells when the vehicle is started and the housing in which the battery cells are stored are used. The input/output power of the battery cell when the difference from the internal temperature information is larger than a predetermined value and the temperature information of the battery cell is higher than the temperature information inside the housing in which the battery cell is stored. limit. With such a configuration, even if there is a large difference between the temperature inside the housing and the temperature of the battery cells, it is possible to reliably limit the allowable power and provide a safe battery pack. becomes.

In addition, the margin for the offset error variation between sensors (ΔT _{offset, margin} ), the vehicle rest time margin (t _{rest, margin} ), and the insensitivity margin for the cell temperature difference before and after the vehicle rest period (ΔT _{drift, margin} ) are expressed by equation (2). can be considered.

The limit rate calculation unit 113 calculates the limit rate with high accuracy from the battery load index, voltage information, temperature information, and charging rate information that are calculated with high accuracy when the RTC cannot be used. Since the post-restriction allowable power calculation unit 114 can calculate the allowable power using this limit rate, it is possible to limit the input/output power with high precision even if the RTC is not used.
The above is a brief summary of the first embodiment. The battery control device according to the present embodiment estimates the elapsed time from the vehicle stop using temperature information of the battery cells and temperature information (for example, environmental temperature) different from the temperature information of the battery cells. It was decided to limit input/output power. By adopting such a configuration, the battery load index can be calculated with high accuracy even in a situation where the RTC cannot be used (for example, a situation in which the RTC is not installed or a situation in which the RTC has failed). Input/output power can be limited even in a situation where an RTC that can limit the output power cannot be used (for example, a situation in which the RTC is not mounted or a situation in which the RTC has failed).

In addition, the battery control device described in this embodiment uses battery cell temperature information when the vehicle is started as the battery cell temperature information. Such a configuration eliminates the need for a temperature sensor for measuring the environmental temperature, so the battery pack can be made simple.

Further, the battery control device described in this embodiment uses the temperature information of the inside of the housing in which the battery cells are accommodated as the temperature information different from the temperature of the battery cells. By adopting such a configuration, it is possible to complete this control as a single battery pack product.

Further, the battery control device according to the present embodiment is provided in the case where the difference between the temperature information of the battery cells when the vehicle is started and the temperature information of the inside of the housing in which the battery cells are accommodated is greater than a predetermined value, and The input/output power of the battery cell is restricted when the temperature information of the battery cell is higher than the temperature information of the inside of the housing in which the battery cell is accommodated. With such a configuration, even if there is a large difference between the temperature inside the housing and the temperature of the battery cells, it is possible to reliably limit the allowable power and provide a safe battery pack. becomes.

In addition, the battery control device described in this embodiment uses the temperature information of the battery cells when the vehicle is stopped as temperature information different from the temperature information of the battery cells. By configuring like this,
Further, the battery control device according to the present embodiment can detect the temperature of the battery cell when the difference between the temperature information of the inside of the housing in which the battery cell is accommodated and the temperature information of the battery cell when the vehicle is stopped is larger than a predetermined value. limit the input and output power of

<<Second embodiment>>
Next, a second embodiment will be described. In the actual BMS 110, it may not be possible to acquire environmental temperature information that is not affected by heat generated by charging and discharging of the battery, so in this embodiment, the environmental temperature information is acquired from the host system. In other words, in this embodiment, the BMS does not acquire the ambient temperature (T _amb ), but instead uses the temperature information of the end of the battery pack instead of the ambient temperature (T _amb ). Calculation conditions were the same as in the first embodiment.

FIG. 6A shows a comparison between the true value and the estimated value of the vehicle downtime estimated using the present embodiment, and FIG. 6B shows the ratio of the estimated vehicle downtime to the true value. From FIG. 6(a), the estimated value of the vehicle down time using the pack end temperature (T _end ) is similar to the estimated value of the vehicle down time using the environmental part temperature (T _amb ). It is transitioning. With such a configuration, it is possible to limit the input/output power with high precision only by providing two temperature sensors in one battery pack.

From the above results, by estimating the vehicle stop time using the battery pack center temperature (T _center ) and the battery pack end temperature (T _end ), even if there is no element that acquires time information such as an RTC, Reliable high load resistance rise suppression can be realized.

Finally, the concept common to each embodiment is summarized. When a large load is continuously applied to the battery pack for a short period of time, the central portion of the battery pack becomes higher than the ambient temperature due to heat generation or the like, resulting in a temperature difference. If the ambient temperature does not change abruptly after the charging/discharging is stopped, this temperature difference exponentially decays over time. In the present invention, using this characteristic, the power is appropriately limited using the BMS stop time calculated based on the temperature information immediately before the BMS is stopped and immediately after the BMS is restarted. With this type of control, when time information cannot be obtained directly from the real-time clock (RTC) due to cost constraints or failures, the battery control system (BMS) stop period can be estimated, and redundancy of the high load resistance rise suppression algorithm can be achieved. It is possible to provide a battery control device that ensures reliability.

As described above, various embodiments have been described, but the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

10 battery system 100 battery pack 110 BMS
111 pre-restriction allowable power calculator 112 battery load index calculator 113 limit rate calculator 114 post-limit allowable power calculator 120 inverter 130 motor 200 battery pack center temperature sensor 210 battery pack edge temperature sensor 220 battery pack housing internal temperature sensor

Claims (3)

In a battery control device that controls charging and discharging of battery cells mounted on a vehicle,
The temperature of the battery cell, the environmental temperature of the battery cell, the temperature inside the housing in which the battery cell is accommodated, or the temperature of the other battery cell at a position where the temperature converges to the environmental temperature faster than the temperature of the battery cell A temperature difference between the temperature and the temperature is obtained at each timing when the vehicle is stopped and when the vehicle is restarted,
In the restart processing, the vehicle stop time of the vehicle is estimated based on the temperature difference at each timing of the stop and the restart, and the battery cell is calculated according to the estimated vehicle stop time. Attenuate the value at the time of suspension of the battery load index representing the magnitude of the load continuously applied to the battery cell and the time the load was continuously applied to the battery cell,
The battery control device limits the input/output power of the battery cell during a period after the restart, based on the battery load index that has been attenuated in the process at the restart. In the battery control device according to claim 1,
During the decay of the battery load indicator during the restart,
At least one of a margin for variations in offset errors between temperature sensors, a margin for the vehicle rest period, and an insensitive margin for the temperature difference before and after the vehicle rest period is provided to determine the battery load index at the time of restart. A battery control device characterized by making it difficult to attenuate. the battery cell;
A battery system comprising the battery control device according to claim 1 or 2.

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