JP2011014395A - Capacitor management device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor management device capable of timely estimating an inner temperature of a capacitor with high accuracy.SOLUTION: The capacitor management device for managing the capacitor which has a correlation between a charging state and an open circuit voltage and of which the correlation changes depending on a temperature is provided with a charging state calculation unit for calculating a value showing a charging state of the capacitor, an open circuit voltage calculation unit for calculating an open circuit voltage of the capacitor, and an estimated inner temperature calculation unit for calculating the estimated inner temperature of the capacitor based on the value showing the charging state calculated by the charging state calculation unit, the open circuit voltage calculated by the open circuit voltage calculation unit, and the correlation depending on the temperature of the capacitor.

Description

  The present invention relates to a capacitor management device that estimates an internal temperature of a capacitor.

  Vehicles such as EVs (Electric Vehicles) and HEVs (Hybrid Electrical Vehicles) are equipped with a battery that supplies electric power to an electric motor or the like. In the battery, a plurality of power storage cells connected in series and in parallel are provided in the exterior body. Secondary batteries, such as a nickel metal hydride battery and a lithium ion battery, are used for an electrical storage cell. In order not to impair the reliability and safety of such a capacitor, it is necessary to monitor the internal temperature of the capacitor.

  Conventionally, it has been common to treat the temperature detected by a temperature sensor attached to the outer package of the capacitor as the internal temperature of the capacitor. However, since the temperature sensor is not provided inside the battery, it merely detects the temperature of the exterior body. In addition, due to the time difference until the heat inside the battery is transferred to the exterior body and the heat loss from the inside of the battery to the exterior body, the accurate internal temperature of the battery is timely determined from the detected temperature of the temperature sensor. I can't get it.

JP 2006-101684 A Japanese Patent No. 3175558

  FIG. 5 is a perspective view showing a partial cross section of the sealed storage battery disclosed in Patent Document 1. As shown in FIG. As shown in FIG. 5, in the sealed storage battery of Patent Document 1, a bottomed hollow projecting portion 6 projecting inward in the battery is formed in the vicinity of the pole column portion of the lid 4. The temperature detector inserted into the electrode measures the temperature of the entire pole column including the electrode group 2 and the lead portion. However, the temperature detector measures the temperature at a position closer to the inside of the storage battery, but in principle, measures the temperature from the outside of the storage battery. For this reason, the said temperature detector will receive to the influence of the heat transfer and heat loss which were mentioned above.

In addition, the hybrid ECU (charge / discharge control device) disclosed in Patent Document 2 calculates the estimated battery temperature Tb (K) from the following equation from the battery heat loss caused by the internal resistance of the battery electrolyte. To do.
・ Ploss (K) = R ・ Ib (K) ²
・ DTb (K) / dt = X (K) = {Ploss (K)-(Tb (K-1) -Ta (K)) ・ h ・ S} / Cb
・ Tb (K) = Tb (K-1) + Δt ・ X (K)

  In the above equation, Ploss (K) is the internal heat generation amount of the battery, R is the internal resistance value of the battery, Ib (K) is the current value of the battery, Ta (K) is the outside temperature, h is the heat dissipation coefficient of the battery, and S is The dropped heat radiation area of the battery, Cb, is the heat capacity of the battery. Note that the internal resistance value R of the battery, the heat dissipation coefficient h of the battery, the equivalent heat dissipation area S of the battery, and the heat capacity Cb of the battery depend on the operating state of the cooling fan of the battery, the battery temperature, and the outside air temperature. Corrective calculation is performed as appropriate.

  However, since the above equation is complicated and includes many parameters that cause errors due to external factors or the like, it cannot be said that the accuracy of the estimated battery temperature calculated by the hybrid ECU is high.

  An object of the present invention is to provide a capacitor management device capable of estimating the internal temperature of a capacitor with high accuracy and timely.

  In order to solve the above-mentioned problems and achieve the object, the battery management device of the invention according to claim 1 has a correlation between the charged state and the open circuit voltage, and the correlation depends on the temperature. A storage device management device (for example, the storage device management device 113 in the embodiment) that manages a storage device that changes (for example, the storage device 103 in the embodiment), and calculates a value indicating a charge state of the storage device State calculation unit (for example, initial SOC derivation unit 201, battery capacity calculation unit 203, SOC change amount calculation unit 205, and SOC correction unit 207 in the embodiment), and open circuit voltage calculation for calculating the open circuit voltage of the battery Units (for example, the internal resistance estimation unit 209, the voltage drop amount calculation unit 213, and the voltage correction unit 215 in the embodiment), the value indicating the charge state calculated by the charge state calculation unit, and the open circuit power Based on the open circuit voltage calculated by the calculation unit and the correlation depending on the temperature of the capacitor, an estimated internal temperature deriving unit that derives the estimated internal temperature of the capacitor (for example, the estimated internal temperature in the embodiment) A temperature deriving unit 217).

  Furthermore, in the electric storage device management apparatus according to claim 2, the electric storage device has the change rate of the open circuit voltage with respect to the internal temperature of the electric storage device with respect to the minimum unit of the internal temperature that can be identified by the electric storage device management device. It is characterized by having a characteristic equal to or higher than the ratio of the minimum unit of the open circuit voltage that can be identified by the management device.

  Furthermore, in the electric storage device management apparatus according to claim 3, the electric storage device has a rate of change of a value indicating a charging state with respect to an internal temperature of the electric storage device with respect to a minimum unit of the internal temperature that can be identified by the electric storage device management device. It is characterized in that it has a characteristic equal to or greater than the ratio of the minimum unit of the value indicating the state of charge that can be identified by the storage device management apparatus.

  Furthermore, in the battery management device according to the invention of claim 4, the charge state calculation unit calculates a value indicating the charge state according to a charge / discharge current of the battery, and the open circuit voltage calculation unit includes: The open circuit voltage is calculated according to the charge / discharge current and terminal voltage of the battery.

  Furthermore, in the electric storage device management apparatus according to claim 5, the electric storage device management device cools the electric storage device when the estimated internal temperature derived by the estimated internal temperature deriving unit is equal to or higher than a first threshold value. Means (for example, cooling fan 115 in the embodiment) is driven.

  Furthermore, in the storage battery management device according to claim 6, when the estimated internal temperature derived by the estimated internal temperature deriving unit is equal to or higher than a second threshold value, the storage battery management device is configured to input / output the capacitor. It is characterized by limiting power.

  According to the storage device management apparatus of the inventions described in claims 1 to 6, the internal temperature of the storage device can be estimated in a timely manner with high accuracy.

  According to the capacitor management device of the inventions of the fifth and sixth aspects, the capacitor can be used without impairing the reliability and safety of the capacitor.

Schematic configuration diagram of an EV equipped with the battery management device 113 of one embodiment The graph which shows the correlation of the charging depth (SOC) in the electrical storage device 103, an open circuit voltage (OCV), and internal temperature. The block diagram which shows the internal structure of the electrical storage device management apparatus 113 The graph which shows the variation | change_quantity of the open circuit voltage (OCV) with respect to the internal temperature of the battery 103. The perspective view which shows the partial cross section of the sealed storage battery disclosed by patent document 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An electric storage device management apparatus according to an embodiment described below is a vehicle such as an EV (Electric Vehicle) or an HEV (Hybrid Electric Vehicle) provided with an electric motor driven by electric power supplied from the electric storage device as a drive source. It is mounted on.

  FIG. 1 is a schematic configuration diagram of an EV equipped with a storage battery management device according to an embodiment. 1 (hereinafter simply referred to as “vehicle”) includes an electric motor M, a transmission mechanism T, drive wheels W, a power control device 101, a capacitor 103, a memory 105, a current sensor 107, a voltage, It mainly includes a sensor 109, a temperature sensor 111, a storage battery management device 113, and a cooling fan 115. In the vehicle, the driving force of the electric motor M is transmitted to the drive wheels W via the speed change mechanism T. Further, when the driving force is transmitted from the driving wheel W side to the electric motor M side during deceleration, the electric motor M functions as a generator to generate a so-called regenerative braking force, and the kinetic energy of the vehicle body is collected in the battery 103 as electric energy. To do.

  The power control device 101 controls power supply from the capacitor 103 to the motor M related to driving of the motor M and recovery of regenerative energy from the motor M to the capacitor 103.

  The capacitor 103 is, for example, a lithium ion battery using lithium titanate (Li4Ti5O12) as a negative electrode and a lithium transition metal oxide as a positive electrode, or a Ni-MH (nickel-metal hydride) battery using a metal hydride as a cathode active material. is there. In order to output a high voltage (for example, 100 to 200 V), the battery 103 has a plurality of power storage cells connected in series and in parallel in the exterior body. Therefore, the capacitor 103 is large.

  FIG. 2 is a graph showing the correlation between the charging depth (SOC), the open circuit voltage (OCV), and the internal temperature in the battery 103. As shown in FIG. 2, as a characteristic of the capacitor 103, a curve indicating a relationship between a state of charge (SOC) and an open circuit voltage (OCV) varies depending on the internal temperature of the capacitor 103. That is, the correlation characteristic of these two values depends on the internal temperature of the battery 103. Therefore, the internal temperature of the battery 103 can be obtained from the two values of the charging depth (SOC) and the open circuit voltage (OCV) of the battery 103.

  The memory 105 is a three-dimensional map showing the correlation between the charging depth (SOC) and open circuit voltage (OCV) of the battery 103 and the internal temperature, or the charging depth (SOC) and open circuit voltage (OCV) with temperature as a variable. Store each function. The memory 105 stores the SOC history immediately after the vehicle ignition is turned on for each run. In the present specification, “running” refers to a period from when the vehicle ignition is turned on to when it is turned off again. Further, the memory 105 stores the amount of electricity used by the vehicle during travel for each travel.

  Current sensor 107 detects charging / discharging current I of battery 103. The charging / discharging current I includes a discharging current supplied from the capacitor 103 to the electric motor M and a charging current supplied from the electric motor M that performs a regenerative operation to the electric capacitor 103. The voltage sensor 109 detects the terminal voltage V of the battery 103. The temperature sensor 111 is attached to the outer package of the battery 103 or the periphery thereof. The temperature sensor 111 detects the temperature T of the outer package of the battery 103 or the surrounding area.

  The storage battery management device 113 estimates the charging depth (SOC) and open circuit voltage (OCV) of the storage battery 103, and derives the estimated internal temperature of the storage battery 103 from these two estimated values. FIG. 3 is a block diagram showing an internal configuration of the battery management device 113. As shown in FIG. 3, the battery management device 113 includes an initial SOC derivation unit 201, a battery capacity calculation unit 203, an SOC change amount calculation unit 205, an SOC correction unit 207, an internal resistance estimation unit 209, an LPF ( Low Pass Filter) 211, voltage drop amount calculation unit 213, voltage correction unit 215, and estimated internal temperature deriving unit 217.

  The initial SOC deriving unit 201 operates at the start of traveling, that is, immediately after the ignition of the vehicle is turned on. When the ignition of the vehicle is turned on, it is considered that a sufficient time has elapsed since the end of the previous run. Therefore, the temperature T detected by the temperature sensor 111 at this time can be regarded as the internal temperature of the battery 103. At the start of traveling, the load on the battery 103 is considered to be substantially zero. Therefore, the terminal voltage V detected by the voltage sensor 109 at this time can be regarded as an open circuit voltage (OCV) of the battery 103.

  Therefore, the initial SOC deriving unit 201 has the terminal voltage V detected by the voltage sensor 109 at the start of traveling, the temperature T detected by the temperature sensor 111, the charging depth (SOC) of the battery 103 recorded in the memory 105, and the open circuit. An initial SOC is derived based on a three-dimensional map or function indicating the correlation between voltage (OCV) and internal temperature. The initial SOC deriving unit 201 records the derived initial SOC value in the memory 105.

  The battery capacity calculation unit 203 also operates at the start of traveling. The battery capacity calculation unit 203 calculates the difference between the initial SOC derived by the initial SOC deriving unit 201 and the initial SOC stored in the memory 105 at the start of the previous run. Further, the battery capacity calculation unit 203 divides the amount of electricity used in the previous travel stored in the memory 105 by the difference in the initial SOC. The value obtained by this calculation is the capacity of the battery 103 (hereinafter referred to as “battery capacity”).

  The SOC change amount calculation unit 205 multiplies the charging / discharging current I detected by the current sensor 107 by a calculation unit time to derive an electric amount. The amount of electricity is the amount of electricity consumed or regenerated by the battery 103 during the operation unit time. Further, the SOC change amount calculation unit 205 integrates the amount of electricity for each calculation unit time according to the elapsed time from the start of traveling. Further, the SOC change amount calculation unit 205 divides the integrated value of the amount of electricity by the battery capacity calculated by the battery capacity calculation unit 203. The value obtained by this calculation is the SOC change amount (ΔSOC) of the battery 103 from the start of traveling.

  The SOC correction unit 207 corrects the initial SOC derived by the initial SOC deriving unit 201 with the SOC change amount (ΔSOC) calculated by the SOC change amount calculation unit 205. The SOC correction unit 207 outputs the value obtained by the correction as “estimated SOC”. Note that the SOC correction unit 207 outputs the estimated SOC after the variation in the value obtained by correcting the initial SOC with the SOC change amount (ΔSOC) has converged within a predetermined range.

  The internal resistance estimation unit 209 divides the value (ΔV) obtained by differentiating the terminal voltage V detected by the voltage sensor 109 by the value (ΔI) obtained by differentiating the charge / discharge current I detected by the current sensor 107. The value obtained by this calculation is an estimated value (Rin) of the internal resistance of the battery 103. The LPF 211 smoothes the internal resistance estimated value (Rin) obtained by the internal resistance estimation unit 209 by filtering. The voltage drop amount calculation unit 213 multiplies the smoothed internal resistance estimated value by the charge / discharge current I detected by the current sensor 107. The value obtained by this calculation is the voltage drop amount (ΔVd) due to the internal resistance of the battery 103.

  The voltage correction unit 215 corrects the terminal voltage V detected by the voltage sensor 109 with the voltage drop amount (ΔVd) calculated by the voltage drop amount calculation unit 213. The voltage correction unit 215 outputs the value obtained by the correction as “estimated OCV”. The voltage correction unit 215 outputs the estimated OCV after the variation in the value obtained by correcting the terminal voltage V with the voltage drop amount (ΔVd) converges within a predetermined range.

  The estimated internal temperature deriving unit 217 includes the estimated SOC output from the SOC correcting unit 207, the estimated OCV output from the voltage correcting unit 215, the charging depth (SOC) of the battery 103 recorded in the memory 105, and the open circuit voltage. The estimated internal temperature of the battery 103 is derived based on a three-dimensional map or function indicating the correlation between (OCV) and the internal temperature.

  FIG. 4 is a graph showing the amount of change in the open circuit voltage (OCV) with respect to the internal temperature of the battery 103. Note that the vertical scale “a” divided by the dotted line in the graph shown in FIG. 4 indicates the minimum unit of the open circuit voltage (OCV) that can be identified by the battery management device 113. That is, the resolution of the open circuit voltage (OCV) in the capacitor management device 113 is “a [V / LSB]”. On the other hand, the division “b” on the horizontal axis in the graph shown in FIG. 4 indicates the minimum unit of the internal temperature that can be identified by the battery management device 113. That is, the resolution of the internal temperature in the storage battery management device 113 is “b [° C./LSB]”. Note that LSB is an abbreviation for “Less Significant Bit”.

  Also, FIG. 4 shows three types of absolute values | k | [V / ° C.] of the change rate of the open circuit voltage (OCV) with respect to the internal temperature of the battery 103, that is, | k |> | a / b |, | k. Lines A, B, and C showing the characteristics of | = | a / b | and | k | <| a / b | are shown. According to the line A indicating the characteristic of | k |> | a / b |, the amount of change in the internal temperature when the open circuit voltage (OCV) changes by 1 LSB (a [v]) is 1 LSB (b [° C.]). (Less than half of 1LSB). Further, according to the line B indicating the characteristic of | k | = | a / b |, the amount of change in the internal temperature when the open circuit voltage (OCV) changes by 1 LSB (a [v]) is 1 LSB (b [° C. ]). Further, according to the line C indicating the characteristic of | k | <| a / b |, the amount of change in the internal temperature when the open circuit voltage (OCV) changes by 1 LSB (a [v]) is 2 LSB (2 b [° C. ]).

  Thus, when | k | <| a / b |, the true value of the internal temperature when the open circuit voltage (OCV) changes by 1 LSB (a [v]) is 2 LSB (2 b [° C.]). Although it should be within the range, the true value of the internal temperature of the battery 103 cannot be determined with the resolution of the internal temperature shown in FIG. Therefore, in order for the storage device management device 113 to obtain the internal temperature with respect to the change in the open circuit voltage (OCV) of the battery 103 more accurately by calculation, when the open circuit voltage (OCV) changes by 1 LSB (a [v]) The amount of change in the internal temperature needs to be within 1 LSB (b [° C.]).

  Thus, as a characteristic of the capacitor 103, the amount of change | k | in the open circuit voltage (OCV) with respect to the internal temperature is preferably | a / b | or more (| k | ≧ | a / b |). The capacitor management device 113 can derive the internal temperature of the capacitor 103 with higher accuracy as the change amount | k | is larger.

  Note that, similarly to the above description, the capacitor management device 113 can derive the internal temperature of the capacitor more accurately as the capacitor has a characteristic that the absolute value of the change amount of the charging depth (SOC) with respect to the internal temperature is larger.

  The cooling fan 115 and the power control device 101 shown in FIG. 1 are controlled according to the estimated internal temperature of the battery 103 derived by the battery management device 113. For example, the capacitor management device 113 drives the cooling fan 115 when the estimated internal temperature of the capacitor 103 is equal to or higher than the first threshold value. In addition, the storage device management device 113 controls the power control device 101 to limit the input / output power of the storage device 103 when the estimated internal temperature of the storage device 103 is equal to or higher than the second threshold value. Furthermore, when the estimated internal temperature of the battery 103 is equal to or higher than the third threshold value, the battery management device 113 controls the power control apparatus 101 to cut off the path between the battery 103 and the electric motor M. Therefore, the battery 103 can be used without impairing the reliability and safety of the battery 103. The first threshold value, the second threshold value, and the third threshold value have the relationship of “first threshold value <second threshold value <third threshold value”. Have.

  As described above, the storage battery management device 113 of the present embodiment estimates the charging depth (SOC) and open circuit voltage (OCV) of the storage battery 103 based on information such as the charge / discharge current I and the terminal voltage V of the storage battery 103. In addition, the estimated internal temperature of the battery 103 is derived from these two estimated values. Since the charging / discharging current I and the terminal voltage V of the battery 103 detected by the current sensor 107 and the voltage sensor 109 are information obtained without delay, the battery management device 113 can appropriately estimate the internal temperature of the battery 103. In addition, since the charge / discharge current I and the terminal voltage V have small errors caused by external factors, the battery management device 113 can estimate the internal temperature of the battery 103 with high accuracy and stability.

M motor T speed change mechanism W drive wheel 101 power control device 103 power storage device 105 memory 107 current sensor 109 voltage sensor 111 temperature sensor 113 power storage device management device 115 cooling fan 201 initial SOC deriving unit 203 battery capacity calculation unit 205 SOC change amount calculation unit 207 SOC Correction unit 209 Internal resistance estimation unit 211 LPF
213 Voltage drop amount calculation unit 215 Voltage correction unit 217 Estimated internal temperature deriving unit

Claims (6)

A capacitor management device that manages a capacitor that has a correlation between a charge state and an open circuit voltage, and the correlation changes depending on temperature,
A state-of-charge calculator that calculates a value indicating the state of charge of the battery;
An open circuit voltage calculation unit for calculating an open circuit voltage of the capacitor;
Based on a value indicating the charge state calculated by the charge state calculation unit, the open circuit voltage calculated by the open circuit voltage calculation unit, and the correlation depending on a temperature of the capacitor, the estimated internal state of the capacitor An estimated internal temperature deriving unit for deriving the temperature;
A capacitor management device comprising: The capacitor management device according to claim 1,
The capacitor has a ratio of a change rate of the open circuit voltage with respect to the internal temperature of the capacitor that is a ratio of a minimum unit of the open circuit voltage that can be identified by the capacitor management device to a minimum unit of the internal temperature that can be identified by the capacitor management device. A capacitor management device having the above characteristics. The storage battery management device according to claim 1 or 2,
In the battery, the rate of change of the value indicating the charging state with respect to the internal temperature of the battery is a value indicating the charging state that can be identified by the battery management device with respect to the minimum unit of the internal temperature that can be identified by the battery management device. A capacitor management device characterized by having a characteristic equal to or greater than a ratio of minimum units. It is a storage device management device according to any one of claims 1 to 3,
The charge state calculation unit calculates a value indicating the charge state according to a charge / discharge current of the battery,
The open circuit voltage calculation unit calculates the open circuit voltage according to the charge / discharge current and the terminal voltage of the storage battery. It is a capacitor | condenser management apparatus as described in any one of Claims 1-4,
The storage battery management apparatus is configured to drive means for cooling the storage battery when the estimated internal temperature derived by the estimated internal temperature deriving unit is equal to or higher than a first threshold value. It is a capacitor | condenser management apparatus as described in any one of Claims 1-5,
The storage battery management apparatus limits the input / output power of the storage battery when the estimated internal temperature derived by the estimated internal temperature deriving unit is equal to or higher than a second threshold value.

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