JP6834409B2 - Battery system - Google Patents

Description

The present invention relates to a battery system that estimates the polarization voltage included in a detection voltage in order to obtain the open circuit voltage of a battery mounted on a vehicle.

As one of the driving sources for driving a vehicle, an electric vehicle equipped with a motor (for example, a hybrid vehicle or an electric vehicle) has been widely known. Such electric vehicles are equipped with an in-vehicle battery that supplies electric power to a traveling motor.

The in-vehicle battery is a rechargeable secondary battery. The in-vehicle battery, which is a secondary battery, needs to be charged / discharged and discharged so as not to be over-discharged and over-charged. For such control, it is required to accurately grasp the SOC (State Of Charge) of the in-vehicle battery. Be done.

The SOC of a battery can be obtained from the open circuit voltage (OCV) of the battery. Therefore, many techniques for obtaining the open circuit voltage of the battery have been conventionally proposed. For example, in Patent Document 1, the open circuit voltage is obtained by adding the voltage drop value (drop voltage) due to the internal resistance and the voltage value (polarization voltage) due to the polarization phenomenon to the measured voltage value detected by the voltage sensor. The technology is disclosed. In Patent Document 1, the voltage drop value due to the internal resistance is obtained by multiplying the internal resistance value determined based on the battery temperature by the current value detected by the current sensor. Further, in Patent Document 1, the polarization voltage is calculated from a map with the battery temperature and the charge / discharge current as parameters.

Here, the influence of the internal resistance is instantaneous, and the drop voltage is immediately eliminated after the charge / discharge is stopped. On the other hand, the polarization gradually changes with the passage of time. That is, when charging / discharging, the absolute value of the polarization voltage gradually increases with the passage of time, and when charging / discharging is stopped, the absolute value of the polarization voltage gradually decreases with the passage of time. Therefore, the divided voltage cannot be appropriately obtained from the current battery temperature and battery current alone. Therefore, in order to obtain the polarization voltage, it is necessary to consider the past charge / discharge history.

Therefore, conventionally, it has been proposed to calculate the current polarization voltage based on the past polarization voltage, the current battery current, and the battery temperature. For example, after specifying the update value based on the current battery current and battery temperature, such as "current polarization voltage = A × 1 polarization voltage before sampling + (1-A) × current update value". A technique is known in which the polarization voltage is calculated by sequentially adding the current update value to the past calculated value. According to such a calculation method, a polarization voltage can be obtained in consideration of the past history.

Japanese Unexamined Patent Publication No. 2005-114646

However, in the conventional calculation of the polarization voltage, no consideration is given to the elimination of the polarization during the period when the battery is stopped. That is, since charging / discharging is also stopped during the battery stop period, the polarization is gradually eliminated (the absolute value of the polarization voltage gradually decreases). However, during the battery stop period, the calculation of the polarization voltage is also stopped. As a result, immediately after the battery is switched from the stopped state to the started state, the "polarization voltage before one sampling" is the polarization voltage immediately before the stop, and the "current update value" is the battery temperature immediately after the start. And the value obtained from the battery current. That is, in the conventional calculation method, the behavior of the polarization voltage during the battery stop period is not considered at all.

As a result, immediately after the battery is started, the polarization voltage is calculated so that the elimination amount is not reflected even though the polarization is actually eliminated. In this case, the absolute value of the polarization voltage is overestimated more than it actually is, and the error of the open circuit voltage becomes large. Here, since the polarization voltage inherits the calculated value in the past, the error immediately after the start of the battery will continue to accumulate even after that, and the error of the open circuit voltage will continue to remain.

Therefore, an object of the present application is to provide a battery system capable of obtaining an open circuit voltage more accurately.

The battery system disclosed in the present application is mounted on a vehicle and can be switched between a start state in which charge / discharge is possible and a stop state in which charge / discharge is not possible, and a current detection that detects the charge / discharge current of the battery as a battery current. The unit, the voltage detection unit that detects the battery voltage of the battery as the detection voltage, the temperature detection unit that detects the temperature of the battery as the battery temperature, and the time from when the battery is stopped to when it is started again. a time measuring unit for measuring a certain stop duration, a polarization voltage calculation unit for calculating a polarization voltage is a voltage variation of the battery due to the minute electrode phenomenon, the current battery temperature and battery current, in the past A polarization voltage calculation unit that calculates the current polarization voltage based on the calculated polarization voltage, a polarization voltage correction unit that corrects the polarization voltage calculated by the polarization voltage calculation unit immediately after the battery is started, and the above. A drop voltage estimation unit that estimates a drop voltage that is a voltage change of the battery due to the internal resistance of the battery, the detection voltage, the drop voltage, and the polarization voltage corrected by the polarization voltage correction unit. The polarization voltage correction unit includes an OCV estimation unit that estimates the open circuit voltage of the battery based on the above, and the polarization voltage correction unit includes a battery current immediately before the battery is stopped, a battery temperature immediately before the battery is stopped, and a battery temperature immediately after the battery is started. Based on the stop duration, the polarization voltage eliminated during the stop period of the battery is calculated as the polarization elimination amount, and the polarization elimination amount calculated by the polarization voltage calculation unit is calculated based on the calculated elimination amount. It is characterized by making corrections.

According to the battery system disclosed in the present application, immediately after the start-up, the battery is stopped during the battery stop period based on the battery current immediately before the battery is stopped, the battery temperature immediately before and immediately after the battery is stopped, and the stop duration. The polarization elimination amount of is calculated, and the polarization voltage calculated by the polarization voltage calculation unit is corrected by the polarization elimination amount. As a result, the polarization voltage and, by extension, the open circuit voltage can be obtained more accurately.

It is a figure which shows the schematic structure of the battery system. It is a functional block diagram of a control part. It is a figure which shows an example of the change of a battery voltage. It is a figure which shows an example of the change of a battery voltage. It is a flowchart which shows the flow of the estimation process of SOC. It is a flowchart which shows the flow of the correction process of a polarization voltage.

Hereinafter, the battery system 10 according to the embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a battery system 10. The battery system 10 is mounted on an electric vehicle (for example, an electric vehicle, a hybrid vehicle, or the like) equipped with a rotary electric machine 100 as one of the power sources.

The battery system 10 includes a battery 12 that supplies electric power to the rotating electric machine 100 for traveling. The battery 12 is configured by connecting a plurality of cell cells 14 in series or in parallel (series in the illustrated example). The number of cell cells 14 constituting one battery 12 can be appropriately set based on the required output of the battery 12 and the like. The cell 14 is a rechargeable secondary battery, for example, a lithium ion secondary battery, a nickel hydrogen secondary battery, or the like.

The battery 12 is connected to the inverter 102 via a system main relay (hereinafter referred to as “SMR”) 20. The SMR 20 electrically connects or disconnects the battery 12 and the inverter 102. When the SMR 20 is turned on, charging and discharging of the battery 12 is allowed. When the user starts the vehicle, the start switch mounted on the vehicle is turned on, and the SMR 20 is switched on / off in conjunction with the start switch.

The inverter 102 controls the current between the battery 12 and the rotary electric machine 100 while converting electric power from direct current to alternating current or from alternating current to direct current. The rotary electric machine 100 functions not only as a motor for outputting the traveling power of the vehicle, but also as a generator for converting the power into electric power. The electric power generated by the rotary electric machine 100 is sent to the battery 12 via the inverter 102, whereby the battery 12 is charged. When the rotary electric machine 100 functions as a motor, the rotary electric machine 100 is driven by the electric power sent from the battery 12. Although the number of rotary electric machines 100 is one in FIG. 1, a plurality of rotary electric machines 100 may be provided. For example, a second rotary electric machine that mainly functions as a motor and a first rotary electric machine that mainly functions as a generator may be provided.

The battery 12 can be further connected to an external power source (not shown) via the charging relay 22, the charger 24, and the inlet 26. The inlet 26 is a connector that can be connected to an external power source, for example, a commercial power source. By connecting the inlet 26 to an external power source and turning on the charging relay 22, the battery 12 can be charged by the external power. The charger 24 converts external power, which is AC power, into DC power and outputs it to the battery 12.

Here, if the SMR 20 is turned off and the charging relay 22 is turned off, charging / discharging of the battery 12 becomes impossible. Hereinafter, the state in which both the SMR 20 and the charging relay 22 are turned off and the battery 12 cannot be charged or discharged is referred to as "stopping the battery 12". Further, a state in which at least one of the SMR 20 and the charging relay 22 is turned on and the battery 12 can be charged and discharged is called "starting the battery 12". During the stop period of the battery 12, most of the functions of the control unit 32 are also stopped.

A temperature sensor 28 is provided in the vicinity of the battery 12. The temperature sensor 28 functions as a temperature detection unit that detects the temperature of the battery 12 as the battery temperature Tb. The detected battery temperature Tb is sent to the control unit 32, which will be described later, and temporarily stored in the storage unit 36. The temperature sensor 28 may be a single temperature sensor 28 or a plurality of temperature sensors 28. When there are a plurality of temperature sensors 28 and a plurality of detected temperatures can be obtained at the same time, one representative value obtained by statistically processing the plurality of detected temperatures, for example, the average temperature, the maximum temperature, the minimum temperature, etc., is used as the battery temperature. It may be treated as Tb. Further, instead of providing the temperature sensor 28, the temperature of the battery 12 (battery temperature Tb) may be estimated based on the temperature of the exhaust duct of the battery 12, the outside air temperature, or the like.

Further, a current sensor 30 is connected to the battery 12. The current sensor 30 functions as a current detection unit that detects the input / output power (charge / discharge power) of the battery 12 as the battery current Ib. The detected battery current Ib is sent to the control unit 32 and temporarily stored in the storage unit 36. The battery current Ib has a positive value when discharged and a negative value when charged.

A voltage sensor 31 is further connected to the battery 12 in parallel. The voltage sensor 31 functions as a voltage detection unit that detects the battery of the battery 12 as the battery voltage Vb. The detected battery voltage Vb is sent to the control unit 32 and temporarily stored in the storage unit 36. Here, as described later, the detected battery voltage Vb includes the open circuit voltage (OCV) Vo of the battery 12, the drop voltage Vr which is the voltage change due to the internal resistance of the battery 12, and the voltage change due to the polarization phenomenon. It is the value obtained by subtracting the polarization voltage Vp, which is the minute. In other words, the battery voltage Vb detected by the voltage sensor 31 is Vb = Vo-Vr-Vp, and the open circuit voltage Vo of the battery 12 is Vo = Vb + Vr + Vp.

The detection of various parameters by the temperature sensor 28, the current sensor 30, and the voltage sensor 31 described above is repeated at a predetermined sampling cycle (for example, several tens of msec to several hundred msec) during the startup period of the battery 12. On the other hand, during the stop period of the battery 12, these sensors 28, 30, 31 stop detecting various parameters.

The charging / discharging of the battery 12 is managed and controlled by the control unit 32. The control unit 32 includes a CPU 34 that performs various operations and a storage unit 36 that stores various programs and parameters. Although the control unit 32 is a single unit in FIG. 1, the control unit 32 may be configured by combining a plurality of control units each having a CPU 34 and a storage unit 36. Therefore, the control unit 32 may be configured to have a plurality of CPUs 34 and storage units 36. Further, some functions of the control unit 32 may be provided outside the vehicle and may be realized by an external control unit capable of communicating with the in-vehicle control unit.

As will be described in detail later, the control unit 32 estimates the SOC of the battery 12 based on the detected battery temperature Tb, battery current Ib, battery voltage Vb, and the like. Here, SOC is an abbreviation for System of Charge and indicates the current charge rate with respect to full charge. The control unit 32 controls the charging / discharging of the battery 12 so that the estimated SOC falls within the range of the specified lower limit value or more and the upper limit value or less. Further, the control unit 32 monitors the ON / OFF state of the start switch, the connection state of the inlet 26, and the like, and also switches the SMR 20 and the charging relay 22 ON / OFF according to these monitoring results.

The battery system 10 also has a timer 38. The timer 38 functions as a time measuring unit for measuring the stop duration td, which is the time from when the battery 12 is stopped until the battery 12 is started again. The measured stop duration td is sent to the control unit 32 and temporarily stored in the storage unit 36.

Next, the functional configuration of the control unit 32 will be described with reference to FIG. FIG. 2 is a functional block diagram of the control unit 32. The control unit 32 has various functions such as charge / discharge power control in addition to the SOC estimation, but FIG. 2 shows only the functions related to the SOC estimation. Further, in FIG. 2, the battery temperature Tb, the battery current Ib, the battery voltage Vb, the stop duration td, and the ON / OFF signals are all input to the respective units 40 to 48 from the outside of the control unit 32. Actually, all of these parameters are temporarily stored in the storage unit 36, and are input from the storage unit 36 to each unit 40 to 48.

The control unit 32 has an SOC estimation unit 40. The SOC estimation unit 40 estimates the SOC of the battery 12 based on the open circuit voltage Vo of the battery 12. Here, the SOC of the secondary battery is substantially proportional to the open circuit voltage Vo of the secondary battery. The storage unit 36 stores an OCV-SOC map 50 that records the value of SOC with respect to the open circuit voltage Vo. The SOC estimation unit 40 estimates the SOC of the battery 12 by comparing the open circuit voltage Vo output from the OCV estimation unit 42, which will be described later, with the OCV-SOC map 50.

The OCV estimation unit 42 estimates the open circuit voltage Vo of the battery 12. As described above, the open circuit voltage Vo is the battery voltage Vb detected by the voltage sensor 31, the drop voltage Vr which is the voltage change due to the internal resistance of the battery 12, and the voltage change due to the polarization phenomenon. It is obtained by adding a certain polarization voltage Vp (Vo = Vb + Vr + Vp). Therefore, the OCV estimation unit 42 calculates Vo = Vb + Vr + Vp and calculates the open circuit voltage Vo.

The drop voltage estimation unit 44 estimates the drop voltage Vr and outputs it to the OCV estimation unit 42. The drop voltage Vr is time-independent and can be obtained by multiplying the internal resistance value R of the battery 12 by the battery current Ib. Here, the internal resistance value R fluctuates according to the temperature of the battery 12, and normally, the lower the battery temperature Tb, the higher the internal resistance value R. The storage unit 36 stores an internal resistance map 52 that records the internal resistance value R with respect to the battery temperature Tb. The drop voltage estimation unit 44 identifies the internal resistance value R by comparing the battery temperature Tb detected by the temperature sensor 28 with the internal resistance map 52. Then, the drop voltage estimation unit 44 outputs a value obtained by multiplying the specified internal resistance value R by the battery current Ib detected by the current sensor 30 as the drop voltage Vr.

The polarization voltage calculation unit 46 estimates the polarization voltage Vp and outputs it to the OCV estimation unit 42. It is known that the polarization voltage Vp increases as the absolute value of the battery current Ib increases and as the battery temperature Tb decreases. Further, the absolute value of the polarization voltage Vp gradually increases with the passage of time after the start of charging / discharging, and gradually decreases with the passage of time after the charging / discharging is stopped. The polarization voltage calculation unit 46 calculates the current polarization voltage Vp based on the current battery temperature Tb, the battery current Ib, and the polarization voltage Vp calculated in the past. Specifically, in order to obtain the current polarization voltage Vp, the polarization voltage calculation unit 46 obtains an update value Vud obtained from the polarization voltage Vp [i-1] one sampling before, the current battery current Ib, and the battery temperature Tb. And are weighted and added. That is, the polarization voltage calculation unit 46 calculates the polarization voltage Vp according to the following equation 1. In addition, α is a weighting coefficient exceeding 0 and less than 1.
Vp = α × Vp [i-1] + (1-α) × Vud Equation 1

The storage unit 36 stores the weight coefficient α, and the weight coefficient map 54 and the update value map 56 for specifying the update value Vud. The weighting coefficient map 54 defines that the larger the absolute value of the battery current Ib and the lower the battery temperature Tb, the smaller the weighting coefficient α. The polarization voltage calculation unit 46 specifies the weighting coefficient α by comparing the current battery temperature Tb and the battery current Ib with the weighting coefficient map 54.

Further, in the update value map 56, it is defined that the larger the absolute value of the battery current Ib and the lower the battery temperature Tb, the larger the update value Vud. The polarization voltage calculation unit 46 identifies the update value Vud by comparing the current battery temperature Tb and the battery current Ib with the update value map 56. If the weighting coefficient α and the update value Vud can be specified, the polarization voltage calculation unit 46 calculates the polarization voltage Vp based on these values.

The polarization voltage correction unit 48 corrects the polarization voltage Vp calculated by the polarization voltage calculation unit 46 only immediately after the battery 12 is started. The specific content of this correction will be described in detail later, but the polarization voltage correction unit 48 calculates the polarization voltage eliminated during the shutdown period of the battery 12 as the polarization elimination amount D, and calculates the calculated polarization elimination amount D. , Subtract from the polarization voltage Vp calculated by the polarization voltage calculation unit 46. That is, the calculation of Vp = Vp−D is performed. This correction process is performed only once immediately after the battery 12 is switched from the stopped state to the started state. Further, for this correction, the storage unit 36 stores the maximum elimination amount map 60 and the elimination rate coefficient map 58. Further, for this correction, the polarization voltage correction unit 48 is input with the stop duration td and the ON / OFF signal in addition to the battery current Ib and the battery temperature Tb. As described above, the stop duration td is the time from when the battery 12 is stopped until it is restarted, and is measured by the timer 38. The ON / OFF signal is a signal indicating a start / stop state of the battery 12. By monitoring this ON / OFF signal, the polarization voltage correction unit 48 determines whether or not the current state is immediately after the start-up, that is, whether or not the polarization voltage Vp needs to be corrected.

Next, the calculation of SOC by the battery system 10 will be described in detail. As described above, the SOC of the battery 12 can be specified from the open circuit voltage Vo of the battery 12. Further, the open circuit voltage Vo of the battery 12 can be specified from the drop voltage Vr, the polarization voltage Vp, and the battery voltage Vb (detection voltage). The relationship between these various voltages will be described with reference to FIG. FIG. 3 is a graph showing an example of a change in the battery voltage Vb (detection voltage) due to discharge.

As shown in FIG. 3, it is assumed that charging / discharging is not performed before the time t0, and the battery voltage Vb is stable at a constant value. Subsequently, when the discharge is started at time t0, the battery voltage Vb drops sharply at the same time as the discharge starts. Further, as the battery voltage Vb continues to be discharged, the amount of voltage drop gradually increases. Here, the amount of voltage drop that occurs at the same time as the start of discharge corresponds to the voltage change due to the internal resistance of the battery 12, that is, the drop voltage Vr. Further, the amount of voltage drop that gradually increases with the passage of time corresponds to the voltage change due to the polarization phenomenon, that is, the polarization voltage Vp.

Subsequently, at time t1, the discharge is stopped. In this case, the battery voltage Vb rises sharply by the drop voltage Vr at the same time as the discharge is stopped. On the other hand, since the polarization voltage Vp is gradually eliminated with the passage of time, the battery voltage Vb gradually rises with the passage of time even after the discharge is stopped. Then, at the time t2 when a sufficient time has elapsed, the battery voltage Vb becomes constant. Here, the amount of increase in the battery voltage Vb that occurs after the drop voltage Vr is eliminated is the polarization elimination amount D, which is the elimination amount of the polarization voltage Vp. Further, the maximum value of the polarization elimination amount D, that is, the polarization elimination amount D at time t2 becomes the maximum elimination amount Dmax.

Here, as described above, the open circuit voltage Vo is obtained by adding the drop voltage Vr and the polarization voltage Vp to the battery voltage Vb. Further, since the polarization voltage Vp is time-dependent, the polarization voltage Vp is obtained by weighting and adding the past polarization voltage Vp [i-1] and the update value Vud according to Equation 1. In this way, by sequentially adding the update value Vud to the past polarization voltage Vp [i-1], the polarization voltage Vp that reflects the change over time of the polarization voltage Vp can be obtained.

However, such calculation of the polarization voltage Vp is repeated only during the start-up period of the battery 12. In other words, during the stop period of the battery 12, detection by various sensors 28, 30, 31 is not performed, so that the calculation (update) of the polarization voltage Vp is not performed. As a result, the polarization voltage Vp obtained by the formula 1 reflects the change with time of the polarization voltage Vp during the start-up period of the battery 12, but does not reflect the change with time of the polarization voltage Vp during the start-up period of the battery 12. ..

This will be described with reference to FIG. FIG. 4 is a diagram showing an example of fluctuation of the battery voltage Vb. In FIG. 4, the battery 12 starts at time t0, stops at time t1, and starts again at time t2.

Here, since the update calculation of the polarization voltage Vp is not performed during the stop period of the battery 12, at the restart time t2, the “polarization voltage Vp [i-1] before one sampling” means the polarization immediately before the stop. The voltage Vp, that is, the polarization voltage Vp [t1] at time t1. Therefore, according to Equation 1, the polarization voltage Vp [t2] at time t2 is Vp [t2] = Vp [t1] + Vud.

On the other hand, in reality, the polarization elimination amount D of the polarization voltage Vp [t1] is eliminated during the stop period (between time t1 and time t2). Therefore, the polarization voltage Vp [t2] at time t2 is originally Vp [t2] = Vp [t1] + Vud-D.

That is, when the polarization voltage Vp is calculated based on Equation 1, the time-dependent change (polarization elimination amount D) of the polarization voltage Vp during the stop period is not reflected, so that the absolute value of the calculated polarization voltage Vp is the polarization elimination amount. It becomes excessive by the amount of D. If the absolute value of the polarization voltage Vp is excessive, the estimation accuracy of the open circuit voltage Vo and, by extension, the SOC will decrease accordingly.

Therefore, the polarization voltage correction unit 48 estimates the polarization elimination amount D immediately after the battery 12 is started, and corrects the polarization voltage Vp calculated by the polarization voltage calculation unit 46 with the polarization elimination amount D. Specifically, the polarization voltage correction unit 48 specifies the maximum elimination amount Dmax and the elimination rate coefficient β when the battery 12 is switched from the stopped state to the started state. The maximum elimination amount Dmax is the maximum value of the polarization voltage Vp that can be eliminated. This maximum elimination amount Dmax becomes larger as the battery current Ib immediately before the stop is larger and as the battery temperature during the stop period is lower. However, since the battery temperature during the stop period cannot be obtained, in the present disclosure, the average temperature Tb_ave of the battery temperature Tb immediately after the start and the battery temperature Tb immediately before the start is regarded as the battery temperature during the stop period. In the maximum elimination amount map 60, the maximum elimination amount Dmax with respect to the battery temperature Tb and the battery current Ib is recorded. The polarization voltage correction unit 48 compares the average temperature Tb_ave with the maximum elimination amount map 60 and the battery current Ib immediately before stopping to specify the maximum elimination amount Dmax.

Further, the elimination rate coefficient β is a coefficient indicating the ratio of the amount of elimination actually eliminated to the maximum amount of elimination Dmax, and takes a value of 0 or more and 1 or less. This elimination rate coefficient β becomes larger as the duration td of the stop period is longer and the battery temperature during the stop period is lower. In the present disclosure, the average temperature Tb_ave of the battery temperature Tb immediately before the stop and immediately after the start is regarded as the battery temperature during the stop period. In the elimination rate coefficient map 58, the elimination rate coefficient β with respect to the stop duration td and the battery temperature Tb is recorded. The polarization voltage correction unit 48 identifies the elimination rate coefficient β by comparing the average temperature Tb_ave and the stop duration td with the elimination rate coefficient map 58. Then, the polarization voltage correction unit 48 calculates the multiplication value of the specified maximum elimination amount Dmax and the elimination rate coefficient β as the polarization elimination amount D (D = β × Dmax). Then, the value obtained by subtracting the obtained polarization elimination amount D from the polarization voltage Vp calculated by the polarization voltage calculation unit 46 is output as the corrected polarization voltage Vp (Vp = Vp−D).

Next, the flow of the SOC estimation process in the battery system 10 will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing the flow of SOC estimation processing, and FIG. 6 is a flowchart showing the flow of polarization voltage Vp correction processing.

During the start-up period of the battery 12, the control unit 32 repeats the process shown in FIG. 5 at a predetermined sampling cycle. On the other hand, during the stop period of the battery 12, the process of FIG. 5 and the detection process by the various sensors 28, 30, and 31 are stopped, and only the stop duration td is measured by the timer 38.

In the SOC estimation process, the drop voltage Vr is first estimated (S10, S12). Specifically, the control unit 32 identifies the internal resistance value R of the battery 12 by comparing the battery temperature Tb detected by the temperature sensor 28 with the internal resistance map 52 stored in the storage unit 36 (S10). ). Subsequently, the control unit 32 multiplies the specified internal resistance value R by the battery current Ib detected by the current sensor 30 to calculate the drop voltage Vr = R × Ib (S12).

If the drop voltage Vr can be estimated, then the control unit 32 estimates the polarization voltage Vp (S14 to S18). Specifically, the control unit 32 updates the battery temperature Tb detected by the temperature sensor 28 and the battery current Ib detected by the current sensor 30 by comparing with the update value map 56 stored in the storage unit 36. The value Vud is specified (S14). Subsequently, the control unit 32 identifies the weighting coefficient α by comparing the battery temperature Tb and the battery current Ib with the weighting coefficient map 54 (S16). If the update value Vud and the weighting coefficient α can be specified, the control unit 32 weight-adds the polarization voltage Vp [i-1] before one sampling and the update value Vud according to Equation 1 (S18).

If the polarization voltage Vp can be calculated, the control unit 32 subsequently confirms whether or not the current state is immediately after the start-up (S20). If not immediately after startup, the control unit 32 proceeds to step S24, adds the battery voltage Vb detected by the voltage sensor 31, the estimated drop voltage Vr, and the estimated polarization voltage Vp, and opens voltage Vo = Calculate Vb + Vr + Vp. After that, the control unit 32 identifies the SOC of the battery 12 by comparing the calculated open circuit voltage Vo with the OCV-SOC map stored in the storage unit 36 (S26). If the SOC of the battery 12 can be identified, the process returns to step S10, and the same process is repeated again.

On the other hand, if it is determined in step S20 immediately after the start-up (Yes in step S20), the control unit 32 executes the correction process (S22) of the polarization voltage Vp. Specifically, as shown in FIG. 6, first, the control unit 32 first receives the battery temperature Tb immediately after startup (that is, the current battery temperature Tb [i]) and the battery temperature Tb immediately before stopping (that is, one sampling before). The average value of the battery temperature Tb [i-1]) and the battery temperature Tb [i-1]) is calculated as the average temperature Tb_ave (S30). Subsequently, the control unit 32 compares the calculated average temperature Tb_ave and the current battery temperature Tb with the maximum elimination amount map 60 to specify the maximum elimination amount Dmax of the polarization voltage (S32). Next, the control unit 32 compares the average temperature Tb_ave and the stop duration td measured by the timer 38 with the resolution rate coefficient map 58 to specify the resolution rate coefficient β (S34).

If the maximum elimination amount Dmax and the elimination rate coefficient β can be specified, the control unit 32 multiplies both to calculate the polarization elimination amount D = β × Dmax (S36). Then, the value obtained by subtracting the calculated polarization elimination amount D from the polarization voltage Vp calculated in step 18 is output as a new polarization voltage Vp = Vp−D (S38). After that, the flow returns to FIG. 5, and the open circuit voltage Vo is calculated (S24) and the SOC is specified (S26).

As is clear from the above description, in the battery system 10 of the present disclosure, immediately after the start-up, the elimination amount D of the polarization voltage during the stop period is calculated, and the polarization voltage Vp is corrected by the calculated polarization elimination amount D. ing. As a result, a polarization voltage Vp that reflects the change over time of the polarization voltage during the stop period is obtained, and the estimation accuracy of the open circuit voltage Vo and thus the SOC is improved.

The configuration described so far is an example, and the polarization during the stop period is based on the battery temperature immediately after the start, immediately before the stop and immediately after the start, the battery current Ib immediately after the start, and the stop duration td. If the elimination amount D is calculated and the polarization voltage Vp is corrected by the calculated polarization elimination amount D, other configurations may be changed as appropriate. For example, the polarization elimination amount D is stored as a function D (Tb, Ib, td) having the average temperature Tb_ave, the battery current Ib immediately before the stop, and the stop duration td as variables, and this function D (Tb, Tb, The polarization elimination amount D may be calculated based on Ib, td).

Further, in the above description, the polarization voltage Vp is calculated according to Equation 1, but if the polarization voltage Vp is calculated based on the past polarization voltage Vp, the current battery temperature Tb, and the battery current Ib, , May be calculated by other methods. For example, the polarization voltage Vp may be calculated according to the following equation 2 instead of the equation 1. In Equation 2, Vp [t0] is the polarization voltage at time t = t0, τ is the time constant that changes depending on the battery temperature Tb, and f {Ib [t]} is the current dependence of the polarization voltage obtained in advance. Ib [t] is the battery current at time t.
Vp [t0] = (1 / τ) ∫f {Ib [t]} exp {(t−t0) / τ} dt Equation 2

10 battery system, 12 batteries, 14 single batteries, 18 steps, 22 charging relays, 24 chargers, 26 inlets, 28 temperature sensors, 30 current sensors, 31 voltage sensors, 32 controls, 34 CPUs, 36 storage units, 38 timers. , 40 SOC estimation unit, 42 OCV estimation unit, 44 drop voltage estimation unit, 46 polarization voltage calculation unit, 48 polarization voltage correction unit, 50 OCV-SOC map, 52 internal resistance map, 54 weight coefficient map, 56 update value map, 58 elimination speed coefficient map, 60 maximum elimination amount map, 100 rotating electric machine, 102 inverter.

Claims (1)

A battery that is mounted on the vehicle and can be switched between a start-up state that can be charged and discharged and a stopped state that cannot be charged and discharged.
A current detector that detects the charge / discharge current of the battery as the battery current, and
A voltage detection unit that detects the battery voltage of the battery as a detection voltage,
A temperature detector that detects the temperature of the battery as the battery temperature,
A time measuring unit that measures the duration of stoppage, which is the time from when the battery is stopped until it is started again.
A polarization voltage calculation unit for calculating a polarization voltage is a voltage variation of the battery due to the minute electrode phenomenon, the current battery temperature and battery current, and the polarization voltage calculated in the past, the current based on the A polarization voltage calculation unit that calculates the polarization voltage,
A polarization voltage correction unit that corrects the polarization voltage calculated by the polarization voltage calculation unit immediately after the battery is started,
A drop voltage estimation unit that estimates a drop voltage, which is a voltage change of the battery due to the internal resistance of the battery,
An OCV estimation unit that estimates the open circuit voltage of the battery based on the detection voltage, the drop voltage, and the polarization voltage corrected by the polarization voltage correction unit.
With
The polarization voltage correction unit was eliminated during the battery stop period based on the battery current immediately before the battery was stopped, the battery temperatures immediately before and immediately after the battery was stopped, and the stop duration. The polarization voltage is calculated as the depolarization amount, and the calculated depolarization amount is used to correct the polarization voltage calculated by the polarization voltage calculation unit.
The battery system is characterized by that.

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