JP2007055450A - Estimating system for deteriorated state of capacitor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the effects of the accumulation of errors resulting from actual environmental conditions, and to grasp the deteriorated state of a capacitor device with a high precision. <P>SOLUTION: When the using environment of a battery is judged to be under a constantly severe environment deviating from a normal range which is predicted in advance from a vehicle position and the data of a driving situation, a deterioration rate SOH' is calculated by using a correction factor which is calculated based on an environment continuing period of time (S15). When a difference between the deterioration rates SOH and SOH' exceeds a reference value, and the deterioration rate SOH needs to be cleared, an operation correcting indication is transmitted to a vehicle system so that the deterioration rate SOH is cleared and the deterioration rate SOH' is used (S19). By the operation correcting indication, the vehicle system clears the deterioration rate SOH which has been calculated by the last operation cycle, and the deterioration operation is resumed with the transmitted deterioration rate SOH' as an initial value. Thus, the effects of the accumulation of errors resulting from the actual environmental conditions are reduced, and the deteriorated state of the capacitor device can be grasped with high precision. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a storage device degradation state estimation system that estimates a degradation state of a storage device mounted on a vehicle.

  In vehicles such as automobiles, it is important to grasp the deterioration state of power storage devices such as batteries. Especially in hybrid cars and electric cars, battery deterioration has a large effect on running performance and fuel consumption. It is required to accurately grasp the degree of deterioration.

  For this reason, various technologies for estimating the deterioration state of the battery have been proposed. For example, Patent Document 1 calculates the internal resistance by measuring the current flowing through the secondary storage battery and the open circuit voltage during the engine start period. And the technique of calculating the remaining life of a secondary storage battery based on this internal resistance is disclosed.

Further, Patent Document 2 obtains an arithmetic expression in which the deterioration state of the storage battery capacity with the passage of time is expressed as a parameter of the time of storage battery temperature in a plurality of temperature ranges, and the prediction of the storage battery with the passage of time is obtained. A technique for predicting the deterioration state of a storage battery by grasping the time of storage battery temperature in each temperature range from the temperature change and applying the time of storage battery temperature in each temperature range to an arithmetic expression is disclosed.
JP 2003-129927 A JP 2003-161768 A

  However, since the technique of Patent Document 1 uses the maximum load terminal voltage and current value at the time of starting the engine, it is expected that the data slightly changes depending on environmental conditions such as the measurement cycle, starter, and engine state. There is a possibility that the internal resistance value that gradually changes in units of several mΩ cannot be captured over the long term.

  In the technique of Patent Document 2, the charge / discharge depth is added based on the calendar life of the storage battery. However, in an automobile in which the environmental temperature and the load change greatly in a short cycle, particularly in a hybrid car or an electric car, errors accumulate. However, depending on actual environmental conditions, the accuracy of deterioration estimation may be reduced.

  The present invention has been made in view of the above circumstances, and provides a degradation state estimation system for an electricity storage device that can reduce the influence of error accumulation due to actual environmental conditions and can accurately grasp the degradation state of the electricity storage device. The purpose is to do.

  In order to achieve the above object, a battery deterioration level estimation system according to the present invention is a storage device deterioration state estimation system that estimates a deterioration state of an electricity storage device mounted on a vehicle, on the premise of preset environmental conditions. A vehicle system that calculates the degree of deterioration of the electricity storage device according to a built-in calculation function and wirelessly transmits an operation history including charge / discharge data of the electricity storage device to the outside, and bidirectionally via the vehicle system and a wireless communication network When the deterioration degree of the electricity storage device is calculated based on the driving history transmitted from the vehicle system and connected so as to be communicable, and the difference between the deterioration degree and the deterioration degree calculated by the vehicle system exceeds a reference value The vehicle system further includes an external calculation system that transmits a correction instruction for deterioration degree calculation.

  At this time, it is desirable that the vehicle system wirelessly transmits the driving history including the position information of the vehicle to the outside, and the external computing system sends the deterioration degree calculated by the vehicle system to the vehicle system. Is preferably transmitted as an instruction to restart the deterioration degree calculation using the deterioration degree calculated by the external calculation system as an initial value.

  The degradation state estimation system for an electricity storage device according to the present invention can reduce the influence of error accumulation due to actual environmental conditions and can grasp the degradation state of the electricity storage device with high accuracy.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 relate to an embodiment of the present invention, FIG. 1 is a configuration diagram of a deterioration state estimation system, FIG. 2 is an explanatory diagram showing a relationship between a resistance increase rate and storage time, and FIG. 3 is a resistance increase rate. 4 is an explanatory diagram showing the relationship between the cycle time and FIG. 4 is an explanatory diagram showing the relationship between the rate of increase in internal resistance and the cycle time in a normal use environment, and FIG. 5 is an increase in internal resistance in an environment that is not assumed. FIG. 6 is a flowchart showing processing on the vehicle system side, and FIG. 7 is a flowchart showing processing on the central management center side.

  FIG. 1 shows an example in which the present invention is applied to a hybrid vehicle (HEV) that travels using both an engine and a motor, and mainly includes a vehicle system 1 of each vehicle and a central management center 100 as an external computing system. Thus, a degradation state estimation system that estimates the degradation state of the electricity storage device in the power supply device of each vehicle is formed. The vehicle system 1 of each individual vehicle and the central management center 100 are connected to each other via a wireless communication network so that bidirectional communication is possible.

  The vehicle system 1 includes a power supply unit 10 that manages in-vehicle power supplies, a HEV control electronic control unit (HEV control ECU) 20 that performs overall control of the entire HEV, and a vehicle that receives radio waves from a GPS (Global Positioning System) satellite. A GPS receiver 50 for acquiring position and time information is provided.

  The power supply unit 10 includes, for example, a battery 11 configured by connecting a plurality of battery packs in which a plurality of cells are sealed in series as an electricity storage device, estimation of a remaining capacity SOC and a deterioration state of the battery 11, cooling of the battery 11, An arithmetic unit (arithmetic ECU) 12 for performing energy management such as charging control, abnormality detection and protection operation at the time of abnormality detection, and a communication module 13 for performing data communication with an external central management center 100 via a wireless communication network These are packaged in one housing. The communication module 13 is controlled by the arithmetic ECU 12.

  In this embodiment, a lithium ion secondary battery will be described as an example of a power storage device, but the present invention can also be applied to other secondary batteries and capacitors such as electric double layer capacitors.

  The arithmetic ECU 12 is composed of a microcomputer or the like, and the terminal voltage V of the battery 11 measured by the voltage sensor 14, the charge / discharge current I of the battery 11 measured by the current sensor 15, and the temperature (cell) of the battery 11 measured by the temperature sensor 16. Based on the temperature (T), the remaining capacity SOC of the battery 11 is calculated at regular intervals, and the deterioration state of the battery 11 is calculated according to a previously incorporated calculation function. The battery information such as the remaining capacity SOC and the deterioration state calculated by the calculation ECU 12 is output to the HEV control ECU 20 via, for example, CAN (Controller Area Network) communication or the like, and is used for basic data for vehicle control, battery remaining amount and warning. It is used as display data for use.

  The HEV control ECU 20 is similarly composed of a microcomputer or the like, and performs HEV operation and other necessary control based on a command from the driver. That is, the HEV control ECU 20 detects the state of the vehicle based on signals from the power supply unit 10 and signals from sensors and switches (not shown), and converts the DC power of the battery 11 into AC power to drive the motor 25. Beginning with the inverter 30, the engine 40, an automatic transmission (not shown), and the like are controlled via a dedicated control unit or directly.

  On the other hand, the central management center 100 is configured with the arithmetic device 101 as a center, and stores the battery information of each vehicle, and stores the vehicle usage environment, the history of driving conditions, and the like, and the wireless communication with the vehicle system 1. A communication device 103 is provided. The computing device 101 monitors the battery charging / discharging usage environment of each individual vehicle. When the computing device 101 determines that it is in an unexpected severe usage environment, the computing device 101 separately computes the deterioration state, and the computing ECU 12 of the vehicle system 1 Compare with the calculated value by. When the difference between the calculated value of the battery deterioration state calculated by the calculation ECU 12 of the vehicle system 1 and the calculated value of the battery deterioration state calculated by the calculation device 101 of the central management center 100 exceeds the reference value. Then, a correction command for deterioration calculation is transmitted from the central management center 100 to the vehicle system 1, and the estimation accuracy of the deterioration state according to the use environment is ensured.

  In other words, the progress of battery deterioration is affected by the number of charge / discharge cycles and the depth of charge / discharge, but greatly depends on the use environment even in the same charge / discharge cycle. In particular, deterioration is promoted when charging / discharging when the battery is at a high temperature or when the battery is used in an environment that is not assumed for a long time. However, the usage environment and driving conditions of the vehicle vary greatly from one vehicle to another, and it is difficult to calculate the deterioration state corresponding to all the conditions. Therefore, as a deterioration calculation function on the vehicle system 1 side, It is necessary to create functions and maps for deterioration calculation on the assumption of a typical use environment, and to incorporate these into the calculation ECU 12. Therefore, when the actual use state of the vehicle is placed in an unexpected severe environment different from the standard, there is a possibility that the deterioration state calculated from the built-in function or map may deviate from the actual deterioration state.

  For this reason, the central management center 100 receives the driving history including charging / discharging data such as GPS position information, voltage, current, temperature, etc. of the battery 11 from the vehicle system 1 via wireless communication, and specifies the usage environment of the vehicle. Whether or not the battery is used continuously and for a long time under severe conditions (unexpected environment) for batteries such as sudden acceleration, sudden stop, and overshooting with intense charging and discharging at high temperatures judge. When it is determined that the vehicle usage state is not assumed, the deterioration progress is calculated by the calculation device 101 outside the vehicle system 1 and compared with the battery deterioration state estimated on the vehicle system 1 side. However, if there is a difference between the two in excess of the reference value, the central control center 100 sends a correction command for the deterioration calculation on the vehicle system 1 side to the vehicle system 1 to ensure the estimation accuracy of the deterioration state. To do.

  Generally, the deterioration state of the battery can be evaluated using a battery health state SOH (State of health) indicated by a ratio of the full charge capacity at the time of deterioration to the initial full charge capacity. Since the change in charge capacity can be estimated with high accuracy by the change in the internal resistance of the battery, in this embodiment, the progress of deterioration is replaced by the rate of increase of the internal resistance at the time of deterioration relative to the initial internal resistance of the battery, and calculated as the deterioration degree SOH. To do.

  In this embodiment, the calculation of the deterioration degree SOH is based on Arrhenius' law representing the relationship between the temperature and the reaction rate in the chemical reaction, and always captures the change in the deterioration state regardless of the load fluctuation of the battery. Is possible. Here, the battery deterioration state estimation process based on Arrhenius' law will be described.

  As is well known, the Arrhenius law is a quantitative description of the temperature dependence of the chemical reaction rate, as shown in the following equation (1). Used for

K = A × e ^{−Ea / RT} (1)
Where K: reaction rate constant
A: Frequency factor
Ea: Activation energy
R: Gas constant (8.314 J / mol-K)
T: temperature (absolute temperature K)
The Arrhenius law can also be applied to the rate constant of the battery's calendar life. If the degree of deterioration of the battery is Yr, the change (deterioration rate) dYr / dTx of the degree of deterioration Yr with respect to time Tx is the reaction rate constant. It can be considered that it corresponds to K. In this case, as can be seen from the following equation (1 ′) in which equation (1) is expressed by a natural logarithm, the deterioration rate needs to consider the influence of frequency factor A in addition to the influence of temperature T. The frequency factor A is a factor irrelevant to the temperature, and can be regarded as a value obtained by replacing the magnitude of stress on the battery due to charging / discharging with a deterioration rate constant.

lnK = (− Ea / R) × (1 / T) + lnA (1 ′)
In the case of deterioration due to temperature, the relationship between the rate of increase in internal resistance and the activation energy differs depending on the type of battery. As an example, with respect to a lithium ion battery, the rate of increase in internal resistance and storage time (square root) at low temperature, normal temperature, and high temperature in a state in which there is no charge / discharge and the stress frequency factor A is A = 1 (standby state). 2 is obtained, the relationship shown in FIG. 2 is obtained. According to this, under a constant temperature condition, it is proved that the linear relationship represented by Yr = aTx is obtained when the internal resistance increase rate (degree of deterioration) of the battery is Yr and the storage time (square root) is Tx. The slope of the straight line a (= dYr / dTx) is related in terms of the activation energy Ea in the equation (1 ′).

  The deterioration due to the temperature is a deterioration in a state where the battery is not charged / discharged, and it is necessary to consider the deterioration due to the charge / discharge stress while the vehicle is operating. The stress frequency factor A constantly changes depending on the magnitude of the stress during use of the battery, and the definition and magnitude of the stress vary depending on the type of battery. As an example, when a lithium ion storage battery is verified, the deterioration of the lithium ion storage battery is caused electrochemically by an inert substance mainly generated in the negative electrode. The generation rate of this inert substance depends on temperature and current density, and when an involuntary reaction is driven by an external power source, the inert substance (precipitation, gas) is generated because no voltage is applied. Only when the current battery potential is exceeded (overvoltage).

  Based on the above, each cycle test by CC (Constant Current) charge / discharge is performed, and the internal resistance increase rate at a certain cycle is measured. As a result, as shown in FIG. 3, for each charging / discharging depth, when the internal resistance increase rate is Yr and the elapsed time (total charging time) is Tx, the linearity indicated by Yr = a′Tx. It is proven to be a relationship. This deterioration rate due to charge / discharge (straight line a ′) can be related to the frequency factor A by the following equation (2).

a ′ = A / dTx (2)
It should be noted that other deterioration factors such as positive electrode deterioration (those having a low weight in the deterioration factors) may be modeled and incorporated into the frequency factor A, and the accuracy can be further improved.

  Specifically, the degree of deterioration SOH based on the above Arrhenius law is calculated by a function or map incorporated in the vehicle system 1 side. That is, as shown in FIG. 4, the calculation ECU 12 of the vehicle system 1 has an internal resistance increase rate and a charge / discharge cycle on the assumption of the temperature and charge / discharge range of the battery 11 assumed in a normal vehicle traveling environment. A function or map of basic characteristics that expresses the relationship with time as a linear relationship with the deterioration rate a as an inclination is incorporated. The arithmetic ECU 12 integrates the rate of increase in internal resistance calculated by correcting this basic characteristic with the deterioration rate a ′ due to the frequency factor A for each set time, and calculates the deterioration degree SOH during vehicle operation. The deterioration rate a 'due to the frequency factor A is a function or map using the battery current I as a parameter.

  On the other hand, the central management center 100 performs rapid acceleration with intense charging / discharging at a high temperature with respect to the internal resistance increase rate under a normal use environment assumed for the vehicle system 1 by a long-term charging / discharging test or the like. We know changes in the rate of increase in internal resistance under severe conditions (unexpected environments) for batteries such as sudden stops and overpasses. As shown in Fig. 5, the internal resistance increases under normal operating conditions. A correction coefficient E for correcting the rate is held as a function or map using the environmental duration as a parameter.

  Then, in the central management center 100, the deterioration degree SOH ′ corrected by the arithmetic unit 101 using the correction coefficient E is compared with the deterioration degree SOH calculated by the arithmetic ECU 12 of the vehicle system 1, and the difference between the two values becomes a reference value. When it exceeds, the central management center 100 transmits a deterioration calculation correction instruction to the vehicle system 1 and transmits the corrected deterioration degree SOH ′. When receiving the calculation correction instruction from the central management center 100, the vehicle system 1 clears the calculated value of the deterioration degree SOH up to the previous time and sets the deterioration degree SOH ′ transmitted from the central management center 100 as an initial value. Resume computation.

  Next, the degradation estimation process by the above system is demonstrated using the flowchart of FIG.6 and FIG.7.

  The processing shown in FIG. 6 shows processing in the arithmetic ECU 12 on the vehicle system 1 side, and is based on data received from the GPS receiver 50 to an external arithmetic device (the arithmetic device 101 of the central management center 100) in the first step S1. The vehicle position and the driving situation based on the voltage V, current I, temperature T, etc. of the battery 11 are transmitted via the communication module 13. Next, the process proceeds to step S <b> 2, and it is checked whether or not there is a correction instruction for the deterioration degree SOH from the external arithmetic device 101 and an instruction to change to the deterioration degree SOH ′ calculated by the external arithmetic device 101 is instructed.

  As a result, if there is no instruction to correct the deterioration level, the process proceeds to step S3, the deterioration level SOH is calculated by the in-vehicle ECU (calculation ECU 12), and the process is exited. If there is a correction instruction from the external arithmetic unit 101, the process proceeds from step S2 to step S4, the degree of degradation SOH calculated up to the previous arithmetic cycle is cleared, and the degree of degradation calculated by the external arithmetic unit 101 is cleared. Replace with SOH '. Thereafter, the deterioration degree calculation in the in-vehicle operation ECU 12 is restarted with the deterioration degree SOH ′ as an initial value.

  On the other hand, the process shown in FIG. 7 shows the flow of the process in the arithmetic unit 101 of the central management center 100. In the first step S11, the data input of the vehicle position and driving situation is input from the arithmetic ECU 12 on the vehicle system 1 side. Check if it exists. As a result, if there is no data input, the process exits and waits until the next data input. If there is data input, the data is stored in the memory in step S12, and the battery usage environment is assumed in advance in step S13. From the input data, it is determined whether the environment is constantly in a severe environment that deviates from the normal range.

  As a result, if the battery usage environment is in the normal range assumed in advance, the process is skipped from step S13, and if the battery usage environment is constantly in a severe environment, the process proceeds from step S13 to step S14. The above-described correction coefficient E is calculated based on the duration, and the degree of deterioration SOH ′ is calculated using the correction coefficient E in step S15.

  Next, the process proceeds to step S16, and the difference between the deterioration degree SOH calculated by the arithmetic ECU 12 on the vehicle system 1 side and the deterioration degree SOH ′ is equal to or less than the reference value, and the calculation of the deterioration degree SOH ′ needs to be continued. (That is, whether or not the severe battery usage environment continues). As a result, when it is determined that the difference between the two deterioration levels SOH and SOH ′ is equal to or less than the reference value and the calculation of the deterioration level SOH ′ needs to be continued, the process proceeds from step S16 to step S17, and the vehicle system 1 side It is checked whether or not there is data input of the vehicle position and driving situation from the arithmetic ECU 12. If there is no data input, the process is terminated. If there is data input, the process returns to step S14 to continue calculating the deterioration degree SOH 'by calculating the correction coefficient E.

  In step S16, if the difference between the two deterioration levels SOH and SOH ′ exceeds the reference value, or if it is determined that the calculation of the deterioration level SOH ′ does not need to be continued, step S16 to step S18. Then, it is checked whether or not the deterioration degree SOH calculated by the arithmetic ECU 12 on the vehicle system 1 side needs to be cleared. If it is determined that the difference between the deterioration levels SOH and SOH ′ exceeds the reference value and is transient and does not affect the progress of the deterioration, it is necessary to clear the deterioration level SOH. If it is determined that there is no need to exit the process from step S18 and clear the degradation degree SOH, the process proceeds from step S18 to step S19.

  In step S19, a calculation correction instruction is transmitted so that the deterioration degree SOH calculated by the calculation ECU 12 on the vehicle system 1 side is cleared and the deterioration degree SOH ′ calculated by the calculation device 101 on the central management center 100 side is used. In response to the calculation correction instruction from the central management center 100, the calculation ECU 12 of the vehicle system 1 clears the deterioration degree SOH calculated up to the previous calculation cycle, and initially sets the deterioration degree SOH ′ transmitted from the central management center 100 side. The deterioration degree calculation is restarted as a value.

  As described above, in this embodiment, when the actual usage state of the vehicle is placed in an unexpected severe environment different from the standard, the deterioration state calculated by the calculation function incorporated on the assumption of the standard usage environment Therefore, it is possible to reduce the effect of error accumulation due to actual environmental conditions and prevent it from deviating from the actual battery deterioration state, and to accurately grasp the deterioration state of the electricity storage device. it can.

Configuration diagram of degradation state estimation system Explanatory diagram showing the relationship between resistance increase rate and storage time Explanatory diagram showing the relationship between resistance increase rate and cycle time Explanatory diagram showing the relationship between internal resistance increase rate and cycle time under normal use environment Explanatory drawing which shows the relationship between the correction coefficient which correct | amends the internal resistance increase rate in the environment where it is not assumed, and environmental duration Flow chart showing processing on the vehicle system side Flow chart showing processing on the central management center side

Explanation of symbols

1 Vehicle system 11 Battery (power storage device)
100 Central management center (external computing system)
SOH degradation level (degradation level calculated by vehicle system)
SOH 'degradation level (degradation level calculated by an external computing system)

Claims (3)

A storage device deterioration state estimation system for estimating a deterioration state of a storage device mounted on a vehicle,
A vehicle system that calculates the degree of deterioration of the power storage device according to a calculation function incorporated on the assumption of a preset environmental condition, and wirelessly transmits an operation history including charge / discharge data of the power storage device to the outside,
The vehicle system is connected to the vehicle system via a wireless communication network so as to be capable of two-way communication. Based on the driving history transmitted from the vehicle system, the deterioration degree of the power storage device is calculated, and the deterioration degree and the vehicle system are calculated. An electrical storage device degradation state estimation system comprising: an external computation system that transmits a degradation degree computation correction instruction to the vehicle system when a difference between the degradation degree exceeds a reference value. The vehicle system is
The deterioration state estimation system for an electricity storage device according to claim 1, wherein the driving history includes the position information of the vehicle and wirelessly transmits the information to the outside. The external computing system is
An instruction to correct the deterioration degree calculation to the vehicle system is transmitted as an instruction to clear the deterioration degree calculated by the vehicle system and restart the deterioration degree calculation using the deterioration degree calculated by the external calculation system as an initial value. The degradation state estimation system of the electrical storage device of Claim 1 or 2 characterized by the above-mentioned.

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