JP4509670B2 - Remaining capacity calculation device for power storage device - Google Patents

Description

  The present invention relates to a remaining capacity calculation device for a power storage device that calculates the remaining capacity of a power storage device such as a secondary battery or an electrochemical capacitor.

  In recent years, energy storage devices such as secondary batteries such as nickel metal hydride batteries and lithium ion batteries, and electrochemical capacitors such as electric double layer capacitors have been reduced in size and weight, and energy density has increased. It is actively used as a power source for automobiles.

  In order to effectively use such an electricity storage device, it is important to accurately grasp its remaining capacity. Conventionally, a technique for calculating the remaining capacity by accumulating the charge / discharge current of the electricity storage device and an open circuit voltage are used. A technique for obtaining the remaining capacity based on this is known.

  For example, in Patent Document 1, the remaining capacity at the time of stoppage is obtained from the open-circuit voltage obtained from the battery voltage at the time of stopping the electric vehicle, and the discharge electric capacity is detected based on the integrated value of the discharge current of the battery. A technique is disclosed in which a full charge capacity is calculated from the electric capacity and the remaining capacity at stop, and the remaining capacity is obtained from the full charge capacity and discharge electric capacity.

  Further, in Patent Document 2, a battery capacity and a battery voltage, such as a lithium ion battery, having a linear proportional relationship, an accumulated amount of current when discharging or charging for an arbitrary time, and discharging or charging. A technique for obtaining a remaining capacity from a previous voltage, a voltage after discharge or a charge is disclosed.

Further, Patent Document 3 discloses a method for calculating the remaining capacity based on the rate of change of the difference between the remaining capacity obtained by integrating the charging / discharging current of the battery and the remaining capacity estimated based on the open terminal voltage of the battery. A technique for correcting the above is disclosed.
JP-A-6-242193 JP-A-8-179018 Japanese Patent Laid-Open No. 11-223665

  However, the technology for calculating the remaining capacity by integrating the charge / discharge current and the technology for determining the remaining capacity based on the estimated open circuit voltage have advantages and disadvantages. The former is resistant to load fluctuations such as inrush current and is stable. Although the remaining capacity can be obtained, there is a drawback that errors are likely to accumulate (especially, the error increases when the load is high), and the latter can obtain an accurate value during normal use. There is a drawback that the calculated value tends to fluctuate when the load fluctuates greatly in a short time.

  Therefore, as in Patent Documents 1, 2, and 3, it is difficult to eliminate error accumulation due to current integration simply by combining both techniques. In particular, in a state where charging / discharging continues as in a hybrid vehicle or the like, there is a possibility that the calculation accuracy of the remaining capacity may decrease or the calculation value of the remaining capacity may change suddenly, thus ensuring stable accuracy. It is difficult.

  The present invention has been made in view of the above circumstances, and reduces the accumulation of errors in the remaining capacity based on current integration, and reduces the influence of load fluctuations in the remaining capacity based on the open circuit voltage, so that the stable and highly accurate remaining It is an object of the present invention to provide a remaining capacity calculation device for a power storage device capable of obtaining a capacity.

  In order to achieve the above object, a storage device remaining capacity calculation device according to the present invention includes a first remaining capacity calculation value based on an open circuit voltage of a storage device and a second value based on an integrated value of charge / discharge currents of the storage device. Based on the capacity difference from the calculated value of the remaining capacity, current error calculation means for calculating the current error of the charge / discharge current of the power storage device, and based on the current error calculated by the current error calculation means, the charge / discharge current A current correction value calculating unit for calculating a current correction value for correcting the measured value of the current and a current correction value calculated by the current correction value calculating unit are used to calculate a current estimated value obtained by correcting the measured value of the charge / discharge current. An open circuit voltage is estimated based on the estimated current value calculating means, the estimated current value calculated by the estimated current value calculation means, and the internal impedance of the power storage device, and is based on the estimated open voltage. The second remaining capacity calculation for calculating the second remaining capacity by integrating the first remaining capacity calculating means for calculating the first remaining capacity and the current estimated value calculated by the current estimated value calculating means. A third remaining capacity for calculating a remaining capacity of the power storage device by weighting and combining the means, the first remaining capacity and the second remaining capacity using a weight set in accordance with the usage state of the power storage device And a capacity calculating means.

  In this case, the current error is estimated from the rate of change of the remaining capacity with respect to the voltage of the power storage device and the impedance, and the current error included in the second remaining capacity is estimated as the current error included in the first remaining capacity. The current correction value can be calculated by filtering the current error.

  The estimated current value is preferably calculated using a current correction value obtained by learning a current error and learning corrected according to the learning result and a learned value of the current error, and is further calculated based on the current correction value. It is desirable to perform failure diagnosis of the sensor that measures the discharge current.

  The remaining capacity calculation device for an electricity storage device of the present invention can reduce the accumulation of errors in the remaining capacity based on current integration, and can reduce the influence of load fluctuations in the remaining capacity based on the open circuit voltage, which is always stable and highly accurate. The remaining capacity can be determined.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 11 relate to an embodiment of the present invention, FIG. 1 is a system configuration diagram showing an application example to a hybrid vehicle, FIG. 2 is a block diagram showing an estimation algorithm of a remaining battery capacity, and FIG. 3 is a battery current. FIG. 4 is a circuit diagram showing an equivalent circuit model, FIG. 5 is an explanatory diagram showing the relationship between remaining capacity and open circuit voltage, and FIG. 6 is a flowchart showing battery remaining capacity calculation processing. 7 is an explanatory diagram of the impedance table, FIG. 8 is an explanatory diagram of the remaining capacity table, FIG. 9 is an explanatory diagram of the weight table, FIG. 10 is an explanatory diagram showing the remaining capacity after current correction, and FIG. It is a flowchart which shows a process.

  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. In the figure, reference numeral 1 denotes a HEV power supply unit. The power supply unit 1 includes, for example, a battery 2 configured by connecting a plurality of battery packs in which a plurality of cells are sealed in series as power storage devices, calculation of the remaining capacity of the battery 2, cooling and charging of the battery 2, and the like. An arithmetic unit (arithmetic ECU) 3 that performs energy management such as control, abnormality detection, and protection operation at the time of abnormality detection is packaged in one casing.

  In this embodiment, a lithium ion secondary battery will be described as an example of an electricity storage device. However, the remaining capacity calculation method according to the present invention can also be applied to an electrochemical capacitor and other secondary batteries.

  The arithmetic ECU 3 is composed of a microcomputer or the like, and the terminal voltage VB of the battery 2 measured by the voltage sensor 4, the charge / discharge current IB of the battery 2 measured by the current sensor 5, and the temperature (cell) of the battery 2 measured by the temperature sensor 6. Temperature) Based on the temperature TB, the state of charge (SOC), that is, the remaining capacity SOC is calculated every predetermined time. This remaining capacity SOC is output from the calculation ECU 3 of the power supply unit 1 to the HEV control electronic control unit (HEV control ECU) 10 via, for example, CAN (Controller Area Network) communication or the like, and the basic data for vehicle control, Used as remaining battery level, warning display data, etc.

  The HEV control ECU 10 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 10 detects the state of the vehicle based on signals from the power supply unit 1 and signals from sensors and switches (not shown), and converts the DC power of the battery 2 into AC power to drive the motor 15. Starting with the inverter 20, an engine, an automatic transmission, and the like (not shown) are controlled via a dedicated control unit or directly.

  The calculation of the remaining capacity SOC in the calculation ECU 3 is executed according to the estimation algorithm shown in the block diagram of FIG. In this SOC estimation algorithm, the most basic parameter for calculating the remaining capacity, that is, the error of the battery current IB measured by the current sensor 5, is corrected, and the current corrected for this error is used for current integration. Based on the remaining capacity SOCI based and the remaining capacity SOCV based on the open circuit voltage estimated from the battery terminal voltage, the battery current, and the internal impedance are calculated in parallel. Then, the remaining capacities SOCI and SOCV are combined by weighting according to the usage state of the battery, and the combined remaining capacity SOC is output as the remaining capacity of the battery 2.

  In general, there are two techniques for calculating the remaining capacity of a battery: a technique for obtaining the remaining capacity based on the integrated value of the battery current and a technique for obtaining the remaining capacity based on the open circuit voltage of the battery. There is. The former is resistant to load fluctuations such as an inrush current and provides a stable remaining capacity, but has a drawback that current errors are likely to accumulate (particularly, the errors increase when a high load is continued). In the latter case, an accurate value can be obtained in a region where the current is stable, but when the load fluctuates greatly in a short time, the impedance for estimating the open circuit voltage of the battery is obtained accurately. This is disadvantageous in that the calculated value of the remaining capacity tends to vibrate.

  Therefore, in this SOC estimation algorithm, the remaining capacity SOCI based on the current integration and the remaining capacity SOCV based on the open circuit voltage are calculated using the current value obtained by correcting the measurement value obtained by the current sensor 5, and in a stable state with little load fluctuation. By increasing the weight of the remaining capacity SOCV based on the open circuit voltage, an accurate remaining capacity SOC is obtained, and in a state where the load fluctuation is relatively large, the weight of the remaining capacity SOCI based on the current integration is increased to obtain the current While preventing the accumulation of errors, a stable remaining capacity SOC is acquired even when the load fluctuates.

  For this reason, the calculation ECU 3 has a first remaining capacity calculation as a first remaining capacity calculation means for calculating a remaining capacity SOCV as a first remaining capacity based on the open circuit voltage as each function forming the SOC estimation algorithm. Unit 3a, second remaining capacity calculating unit 3b as second remaining capacity calculating means for calculating remaining capacity SOCI as the second remaining capacity based on current integration, the calculated value of the first remaining capacity and the second In order to correct the current value IB measured by the current sensor 5 using the current error ID, the current error calculation unit 3c as a current error calculation means for calculating the current error ID based on the difference in capacity from the calculated value of the remaining capacity. The current correction value calculation unit 3d as a current correction value calculation means for calculating the current correction value IDF of the current correction value IDF is used to correct the current value IB measured by the current sensor 5 by using the current correction value IDF, thereby obtaining a measurement error. The estimated current value IS as the excluded current value is calculated and output to the first remaining capacity calculator 3a and the second remaining capacity calculator 3b. The remaining capacity SOCV and the second remaining capacity SOCI are combined by weighting with a weight (weighting factor) w that is changed as needed according to the usage state of the battery 2, and a final remaining capacity SOC is calculated. A third remaining capacity calculating unit 3f is provided as remaining capacity calculating means.

Specifically, the remaining capacity SOCI based on the current integration can be expressed by the following equation (1) based on the battery current I with the initial value SOCI (0) as the base value. Note that the current I, voltage V, and temperature T in the following equations represent theoretical parameters.
SOCI = SOCI (0) −∫ [(100 × η × I / AH) + SD] dt / 3600 (1)
Where η: current efficiency
AH: Current capacity (variable depending on temperature)
SD: Self-discharge rate

The current efficiency η and the self-discharge rate SD can be regarded as constants in the lithium ion battery of this embodiment, and can be practically η = 1 and SD = 0. Therefore, the expression (1) can be expressed by the following expression (1 ′).
SOCI = SOC (0) − (∫Idt) / (AH × 3600) (1 ′)

Here, the remaining capacity SOCI when the error ID is superimposed on the battery current can be expressed by the following equation (2).
SOCI = SOCI (0) − [(∫Idt) / (AH × 3600) + (∫IDdt) / (AH × 3600)] (2)

On the other hand, the open circuit voltage VOC of the battery can be expressed by the following equation (3) by the terminal voltage V, the battery current I, and the impedance Z.
VOC = V + I × Z (3)

The relationship between the open-circuit voltage VOC and the remaining capacity SOCV based on this open-circuit voltage VOC is the well-known Nernst describing the electrochemical relationship in the battery, that is, the relationship between the electrode potential and the ion activity in an equilibrium state. The following expression (4) can be applied.
VOC = E + [(Rg × T / Ne × F) × lnSOCV / (100−SOCV)] + Y (4)
However, E: Standard electrode potential (E = 3.745 in the lithium ion battery of this embodiment)
Rg: Gas constant (8.314 J / mol-K)
T: temperature (absolute temperature K)
Ne: Ion valence (Ne = 1 in the lithium ion battery of this embodiment)
F: Faraday constant (96485 C / mol)

Note that Y in the equation (4) is a correction term and expresses the voltage-SOC characteristic at normal temperature as a function of SOC. If SOCV = X, it can be expressed by a cubic function of SOCV as shown in the following equation (5).
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (5)

From the relationship of the above equation (4), when the remaining capacity SOCV is expressed by the function F of the open circuit voltage VOC, the relationship of the following equation (6) is obtained, and the remaining capacity SOCV when the error ID is superimposed on the battery current. Can be approximated by the following equation (7) using the function F and the function G of the voltage due to the error current.
SOCV = F (VOC) (6)
SOCV = F (V + I × Z) + G (ID × Z) (7)

Here, since the voltage (ID × Z) due to the error current is a smaller value than the terminal voltage V, when considering the rate of change of the remaining capacity with respect to the voltage, the capacity due to the function G is a linear function with respect to the voltage. Can be assumed. Therefore, the equation (7) can be expressed using a coefficient KSC with the remaining capacity SOC as a parameter, as shown in the following equation (8).
SOCV = F (V + I × Z) + KSC × (ID × Z) (8)

From the remaining capacity SOCV expressed by the above expression (8) and the remaining capacity SOCI expressed by the expression (2), the capacity difference ESOC between them is the current error, that is, the change in the remaining capacity with respect to the voltage. It can be considered that the current error estimated from the rate and the impedance Z and the current error estimated based on the current capacity AH are superposed. Therefore, when the capacity component due to the current error ID is expressed using this capacity difference ESOC, it can be expressed by the following expression (9), and further, the following expression (10) expressed in a differential form can be obtained. .
ESOC = (∫IDdt) / (AH × 3600) + KSC × (ID × Z) (9)
d (ESOC) / dt = ID / (AH × 3600) + KSC × Z × d (ID) / dt (10)
However, ESOC = SOCV-SOCI

Further, since the expression (10) expressed in the continuous time system is calculated by a periodic calculation process, it is discretized by the calculation period DLTT for each sample time k, and simplified to the following expression (11) to obtain a current error ID. Express.
ID (k) = [1-DLTT / (KSC × Z × AH × 3600)] × ID (K−1) + [1 / (KSC × Z)] × [(ESOC (k) −ESOC (k−1) )] ... (11)
However, ESOC (k) = SOCV (k-1) -SOCI (k-1)

  As shown in FIG. 3, the battery current capacity AH changes depending on the temperature, and the battery capacity decreases as the temperature becomes lower. For example, a table with the temperature TB as a parameter is prepared. The current capacity AH is calculated with reference to this table.

In this case, as described above, the remaining capacity SOCV based on the open circuit voltage may include a vibration component due to load fluctuation. Therefore, a current correction value IDF for correcting the battery current measured by the current sensor 5 is calculated as shown in the following expression (12) by filtering the current error ID according to the expression (11).
IDF (k) = (1-KA) × IDF (k−1) + KA × ID (k) (12)
KA: filter constant (0 <KA <1)

Then, using the measured value IB of the battery current by the current sensor 5 and the current correction value IDF calculated from the current error ID, a current estimated value IS as a current value excluding the measurement error is obtained by the following equation (13). .
IS (k) = IB (k) −IDF (k) (13)

  Although details will be described later, the current error ID may be learned when the current correction value IDF is calculated. The estimated current value IS is calculated using the current correction value IDF reflecting the learning result and the learned value obtained by learning the current error ID. Further, since the current correction value IDF corrects the actual measured value of the battery current by the current sensor 5, the range that the current correction value IDF can take is limited to a preset range, and exceeds this set range. By investigating whether or not there is a failure diagnosis of the current sensor 5 can be performed.

After obtaining the current estimated value IS, the current estimated value IS is applied to the above-described equation (1) to calculate the remaining capacity SOCI based on the current integration and the remaining capacity SOCV based on the open circuit voltage. The remaining capacity SOCI based on the current integration is calculated by the following equation (14).
SOCI (k) = SOCI (k−1) + IS (k) × DLTT / (AH × 3600) (14)

  The remaining capacity SOCV based on the open circuit voltage is the terminal voltage V and the battery current I measured by the voltage sensor 4 in the above-described equation (3), respectively, and the estimated current value obtained from the equation (13). After applying IS and obtaining the open circuit voltage VOC using the impedance Z, the remaining capacity SOCV is obtained using the open circuit voltage VOC as a parameter.

  Here, the impedance Z of the battery can be obtained using the equivalent circuit model shown in FIG. This equivalent circuit is an equivalent circuit model in which parameters of resistance components R1 to R3 and capacitance components C1, CPE1, and CPE2 (where CPE1 and CPE2 are double layer capacitance components) are combined in series and in parallel. Each parameter is determined by curve fitting a well-known Cole-Cole plot in the method.

  The impedance Z obtained from these parameters varies greatly depending on the temperature of the battery, the electrochemical reaction rate, and the frequency component of the charge / discharge current. Therefore, the current change rate is employed as a frequency component replacement as a parameter for determining the impedance Z. Although the current change rate directly reflects the load change of the battery, the mere current change rate is affected by a sudden change in current that occurs in a spike manner.

  The effects of this spike-like current can be mitigated by processing such as simple averaging, moving average, weighted averaging, etc. of a predetermined number of samplings, but especially when current delay is taken into account, changes in the charge / discharge state of the battery On the other hand, a moving average that can appropriately reflect the past history without being excessive is used. In other words, the moving average of the current becomes a low-pass filter for the high frequency component of the current, and the filtering of the moving average can remove the spike component of the current generated due to the load fluctuation during traveling without promoting the delay component. .

  Specifically, assuming that the moving average value of the battery current is IM, after performing impedance measurement under the condition of the current change rate ΔIM / Δt and the temperature TB at time t of the moving average value IM, Based on the temperature TB and the current change rate ΔIM / Δt, a table of impedance Z (an impedance table in FIG. 7 described later) is created. Then, the impedance Z is obtained using this table, and the open-circuit voltage VOC is obtained by applying the impedance Z, the terminal voltage VB, and the estimated current value IS to the above-described equation (3).

  In detail, the internal impedance Z of the battery increases as the temperature decreases, and the current change rate decreases accordingly. Therefore, as will be described later, the current change rate ΔIM / Δt is directly set to the temperature. Impedance Z is determined using the corrected current change rate TKΔIM / Δt after correction.

  The relationship between the open-circuit voltage VOC and the remaining capacity SOCV can be obtained from the above equation (4) based on the Nernst equation, but the specific correlation varies depending on the type and characteristics of the battery, for example, a lithium ion battery Then, it can be represented by a curve as shown in FIG. The relationship between the open circuit voltage VOC and the reference remaining capacity SOCV shown in FIG. 5 is a correlation represented by a curve that changes monotonically without a change in the reference remaining capacity SOCV being flat with respect to a change in the open circuit voltage VOC. By knowing the value of the open circuit voltage VOC, the value of the reference remaining capacity SOCV can be clearly grasped.

  Further, the remaining capacity SOCV has a strong correlation not only with the open circuit voltage VOC but also with the battery temperature. As shown in FIG. 5, even if the open circuit voltage VOC is the same value, the reference is given when the battery temperature decreases. The remaining capacity SOCV decreases. In this case, it is possible to directly calculate the remaining capacity SOCV using the equation (4) using the open circuit voltage VOC and the temperature TB as parameters. Etc. need to be considered.

  Therefore, when grasping the actual state of the battery from the relationship of the above equation (4), a charge / discharge test or simulation in each temperature range is performed based on the SOCV-VOC characteristics at room temperature, and the measured data is obtained. accumulate. Then, a table of remaining capacity SOCV (remaining capacity table in FIG. 8 described later) that parameters open circuit voltage VOC and temperature TB is created from the accumulated measured data, and the remaining capacity SOCV is obtained using this table.

The above remaining capacities SOCI and SOCV are combined by weighting with a weight (weighting factor) w that is changed as needed according to the usage state of the battery 2, and a final remaining capacity SOC is calculated. The weight w is changed between w = 0 and 1, and the final remaining capacity SOC (k) after synthesis is given by the following equation (15).
SOC (k) = w × SOCI (k) + (1−w) × SOCV (k) (15)

  The weight w needs to be determined using a parameter that can accurately represent the current battery usage. The parameters include the current change rate per unit time and the deviation between the remaining capacities SOCI and SOCV. Etc. can be used. Preferably, the current change rate ΔIM / Δt by the moving average described above can be used as the current change rate per unit time. In this embodiment, the weight w is determined using the current change rate ΔIM / Δt.

  When the current change rate ΔIM / Δt is large, the weight of the remaining capacity SOCI based on the current integration is increased and the weight of the remaining capacity SOCV based on the open circuit voltage is reduced, so that the accuracy by the current integration can be improved regardless of the load fluctuation. In addition, it is possible to obtain a large remaining capacity and to prevent vibration during open circuit voltage estimation. Conversely, when the current change rate ΔIM / Δt is small, the weight of the remaining capacity SOCI based on the current integration is reduced and the weight of the remaining capacity SOCV based on the open circuit voltage is increased, thereby accumulating errors during current integration. The influence can be avoided and an accurate remaining capacity based on the open circuit voltage can be obtained.

  As a result, the accumulation of errors due to current integration is suppressed, and even when a disturbance occurs, a stable and accurate remaining capacity can be obtained, and the disadvantages of both the remaining capacity SOCI and SOCV can be canceled and mutual advantages can be obtained. It is possible to maximize the accuracy of estimation of the remaining capacity.

  Next, the calculation process of the remaining capacity SOC of the battery by the above current correction will be described with reference to the flowchart of FIG. In the remaining capacity calculation process shown in FIG. 6, learning control of the current error ID is taken in.

  The flowchart of FIG. 6 shows a basic process of remaining capacity estimation in the arithmetic ECU 3 of the power supply unit 1 and is executed at predetermined time intervals (for example, every 0.1 sec). When this processing starts, first, in step S1, the battery impedance Z and current capacity AH are read by referring to a table or the like, and the coefficient KSC used for calculating the current error ID is read.

  The terminal voltage VB of the battery 2 is the average value of the plurality of battery packs, and the current IB is the sum of the currents of the plurality of battery packs, and data is acquired, for example, every 0.1 sec. The temperature TB is acquired every 10 sec, for example.

  FIG. 7 is an example of an impedance table in which impedance Z is stored using the corrected current change rate TKΔIM / Δt obtained by temperature correction of the current change rate ΔIM / Δt based on the moving average of the current and the temperature TB as parameters. When the corrected current change rate TKΔIM / Δt is the same, the impedance Z increases as the temperature TB decreases. At the same temperature, the impedance Z increases as the corrected current change rate TKΔIM / Δt decreases. Have a tendency to

  For example, when the current sampling is performed every 0.1 sec and the current integration calculation cycle is performed every 0.5 sec, the moving average of the current is averaged over five data.

  Next, the process proceeds to step S2, and the remaining capacities SOCI (k-1) and SOCV (k-1) one calculation cycle before are read. The remaining capacities SOCI (k-1) and SOCV (k-1) read this time, together with the remaining capacities SOCI (k-2) and SOCV (k-2) read in the previous calculation cycle, the capacity difference ESOC ( k), used when calculating ESOC (k-1). In step S3, the current error ID is calculated according to the above-described equation (11) using the impedance Z, the current capacity AH, the coefficient KSC, the capacity difference ESOC (k), and the capacity difference ESOC (k-1). In step S4, the current error ID is filtered using the filter constant KA according to the above-described equation (12) to calculate the current correction value IDF.

Steps S5 to S11 following step S4 are learning control processes for the current error ID. First, in step S5, as shown in the following equation (16), a filter process is performed on the current correction value IDF. Then, a learning update amount reference value ILB serving as a reference value for updating the current error learning value (current error learning value) IDL is calculated.
ILB (k) = (1-KA) × ILB (k−1) + KB × KL × ID (k) (16)
However, KB: filter constant (0 <KB <1)
KL: learning value constant (0 <KL <1)

Next, the process proceeds to step S6, where the counter CL for determining the learning value update timing is counted up (CL = CL + 1). In step S7, the counter CL is set to a set value TL (for example, a counter value corresponding to about 10 min). Check whether or not. As a result, if CL <TL, the process jumps from step S7 to step S12. If CL = TL, the process proceeds from step S7 to step S8, and is stored in the memory as shown in the following equation (17). The learning update amount reference value ILB (k) is added to the current error learning value IDL (k−1) up to the previous time to calculate a new current error learning value IDL (k). Then, the current error learning value IDL (k−1) stored in the memory is rewritten with the new current error learning value IDL (k), and the learning value is updated.
IDL (k) = IDL (k-1) + ILB (k) (17)

After updating the current error learning value IDL, the process proceeds to step S9, and as shown in the following equation (18), the learning update amount reference value ILB is subtracted from the current correction value IDF previously calculated in step S4 to newly To a correct current correction value IDF. The correction of the current correction value IDF is to eliminate the step when calculating the current estimation value IS using the current correction value IDF in the following step S12, and to ensure continuity in calculation.
IDF = IDF-ILB (18)

Next, in steps S10 and S11, the learning update amount reference value ILB is reset (ILB = 0), the counter CL is cleared (CL = 0), and the process proceeds to step S12. In step S12, the estimated current value is obtained from the following equation (19) using the measured current value IB, the current correction value IDF, and the current error learned value IDL of the battery current and incorporating the current error learned value IDL into the aforementioned equation (13). Calculate IS.
IS = IB- (IDF + IDL) (19)

  When learning control is not performed, the above steps S5 to S11 are omitted, and from the current correction value IDF calculated in step S4 and the measured value IB of the battery current, the above equation (13), that is, (19 ) To calculate the current estimated value IS according to the equation where IDL = 0.

  Thereafter, the process proceeds to step S13, and the remaining capacity SOCI is calculated by integrating the current estimated value IS according to the above-described equation (14). Further, in step S14, the remaining capacity SOCV based on the open circuit voltage is calculated by referring to a table using the battery temperature TB and the open circuit voltage VOC as parameters. FIG. 8 is a remaining capacity table created by grasping the electrochemical state in the battery based on the Nernst equation as described above. In general, the lower the temperature TB and the open circuit voltage VOC, The remaining capacity SOCV tends to increase as the temperature TB and the open circuit voltage VOC increase as the remaining capacity SOCV decreases.

  7 and 8 show data in a range that is used under normal conditions, and data in other ranges is omitted.

  Thereafter, the process proceeds to step S15, and the weight w is calculated with reference to the weight table shown in FIG. The weight table is a one-dimensional table using the corrected current change rate TKΔIM / Δt as a parameter. In general, the smaller the corrected current change rate TKΔIM / Δt, that is, the smaller the battery load fluctuation, There is a tendency that the value of w is reduced to reduce the weight of the remaining capacity SOCI by current integration. Then, according to the above-described equation (15), the remaining capacity SOCI based on the current integration and the remaining capacity SOCV based on the open circuit voltage are weighted and synthesized using the weight w, and the final remaining capacity SOC is calculated to calculate one cycle. This calculation process is terminated.

  The remaining capacity SOC by the above current correction processing is shown in FIG. 10 together with the quasi-remaining capacity without current correction and the theoretical remaining capacity without current error. In the remaining capacity without current correction, the current error accumulates over time, and the deviation from the true remaining capacity increases, but the remaining capacity of this method with corrected current error causes vibration due to load fluctuations. Therefore, accumulation of current error can be effectively suppressed, and an accurate and stable remaining capacity close to the true value can be obtained.

  In parallel with the calculation process of the remaining capacity SOC using the current estimation value IS described above, the fault diagnosis process for the current sensor 5 shown in FIG. 11 is executed.

  In the failure diagnosis process of the current sensor 5, the current correction value IDF is read in the first step S21, and the absolute value | IDF | of the current correction value IDF is compared with the preset diagnosis value IDMAX in step S22. The diagnostic value IDMAX is, for example, the maximum value of the current error that occurs when the measurement value obtained by the current sensor 5 deviates from the normal range.

  If | IDF | ≦ IDMAX, it is determined that the current sensor 5 is normal and the process exits from step S22. If | IDF |> IDMAX, the process proceeds from step S22 to step S23, and the current sensor 5 is abnormal. The failure is determined to be and the process is exited. When this failure determination is made, a fail signal is output from the arithmetic ECU 3 to the HEV control ECU 10, and the process immediately shifts to fail control.

  The remaining capacity SOC when the current sensor is abnormal can be a value estimated using only the remaining capacity SOCV based on the open circuit voltage with the weight w fixed at “0”, for example. In this case, although the estimation accuracy of the open-circuit voltage VOC is lowered, it is possible to ensure safety by enabling a short-time fail control at the time of abnormality.

System configuration diagram showing an example of application to a hybrid vehicle Block diagram showing the remaining battery capacity estimation algorithm Explanatory diagram showing the relationship between battery current capacity and temperature Circuit diagram showing equivalent circuit model Explanatory diagram showing the relationship between remaining capacity and open circuit voltage Flow chart showing battery remaining capacity calculation processing Illustration of impedance table Explanation of remaining capacity table Illustration of weight table Explanatory diagram showing remaining capacity after current correction Flow chart showing fault diagnosis processing of current sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply unit 2 Battery 3 Computation unit 3a 1st remaining capacity calculation part 3b 2nd remaining capacity calculation part 3c Current error calculation part 3d Current correction value calculation part 3e Current estimated value calculation part 3f 3rd remaining capacity calculation part VOC Battery open voltage SOCV remaining capacity (first remaining capacity)
SOCI remaining capacity (second remaining capacity)
SOC remaining capacity (final remaining capacity)
ESOC Capacity Difference IB Battery Current Measurement Value ID Current Error IDL Current Error Learning Value IDF Current Correction Value IS Current Estimated Value
Agent Patent Attorney Susumu Ito

Claims (5)

Based on the capacity difference between the calculated value of the first remaining capacity based on the open circuit voltage of the power storage device and the calculated value of the second remaining capacity based on the integrated value of the charge / discharge current of the power storage device, the charge / discharge of the power storage device Current error calculation means for calculating a current error of the current;
Current correction value calculation means for calculating a current correction value for correcting the measured value of the charge / discharge current based on the current error calculated by the current error calculation means;
Current estimated value calculating means for calculating a current estimated value obtained by correcting the measured value of the charge / discharge current by the current corrected value calculated by the current corrected value calculating means;
A first remaining capacity that estimates an open circuit voltage based on the estimated current value calculated by the current estimated value calculation means and an internal impedance of the power storage device, and calculates the first remaining capacity based on the estimated open circuit voltage A calculation means;
A second remaining capacity calculating means for calculating the second remaining capacity by integrating the current estimated values calculated by the current estimated value calculating means;
Third remaining capacity calculation means for calculating a remaining capacity of the power storage device by weighting and combining the first remaining capacity and the second remaining capacity using a weight set in accordance with a usage state of the power storage device. And a remaining capacity computing device for an electricity storage device. The current error calculation means is
The current error included in the first remaining capacity is estimated from the change rate and impedance of the remaining capacity with respect to the voltage of the power storage device, and the current error included in the second remaining capacity is estimated as the power storage device. The remaining capacity calculation device for an electricity storage device according to claim 1, wherein the current error is calculated based on a current capacity of the storage device. The current correction value calculation means includes:
3. The storage device remaining capacity calculation device according to claim 1, wherein the current correction value is calculated by filtering the current error. The current correction value calculation means includes:
Learning the current error, learning and correcting the current correction value according to the learning result,
The current estimated value calculation means includes:
The remaining capacity calculation apparatus for an electricity storage device according to any one of claims 1 to 3, wherein the current estimation value is calculated using the current correction value subjected to learning correction and the learned value of the current error.   5. The apparatus according to claim 1, further comprising a failure diagnosis unit that performs failure diagnosis of the sensor that measures the charge / discharge current based on the current correction value calculated by the current correction value calculation unit. The remaining capacity calculation device for an electricity storage device according to claim 1.

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