JP4570916B2 - 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.

  In addition, when integrating the charge / discharge current to obtain the remaining capacity, as disclosed in Patent Document 3, the charge / discharge current is sampled at a predetermined time interval to obtain a current time product, and this current time product is obtained. Therefore, if the previous remaining capacity calculation value becomes abnormal due to disturbance or the like, the error increases and adversely affects the control system. There is a risk of affecting.

  The present invention has been made in view of the above circumstances, and the calculation result of the remaining capacity becomes abnormal while obtaining the remaining capacity with high accuracy by taking advantage of both the remaining capacity based on the current integration and the remaining capacity based on the open circuit voltage. It is an object of the present invention to provide a remaining capacity calculation device for an electricity storage device that can quickly converge to a true value even in the case of a failure.

In order to achieve the above object, an apparatus for calculating a remaining capacity of a power storage device according to the present invention comprises: Second computing means for calculating the second remaining capacity based on the open circuit voltage estimated from the internal impedance, and the first remaining capacity and the second remaining capacity are set in accordance with the usage status of the power storage device. A third computing unit that calculates a third remaining capacity weighted and synthesized using the weights as a final remaining capacity of the power storage device, and a terminal of the power storage device when the third remaining capacity is abnormal calculating an approximate value of the third remaining capacity based on the voltage, this approximation a current integrated initial value calculating means to an initial value of the current integration in calculating the first remaining capacity, on Accumulated current initial value calculating means is characterized by determining whether the third remaining capacity of abnormality based on the difference between the terminal voltage and the open-circuit voltage of the storage device.

At this time , it is desirable to distinguish between an abnormality due to a disturbance and an abnormality due to a failure based on the difference between the first remaining capacity and the second remaining capacity. In addition, when the approximate value cannot be calculated in a state where the third remaining capacity is identified as abnormal due to disturbance, it is desirable to calculate an intermediate value of the third remaining capacity as an initial value.

  The remaining capacity calculation device for an electricity storage device according to the present invention obtains the remaining capacity with high accuracy by taking advantage of both the remaining capacity based on the current integration and the remaining capacity based on the open circuit voltage, and the calculation result of the remaining capacity becomes abnormal. Even in this case, it is possible to quickly converge to the true value.

  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 an equivalent circuit. FIG. 4 is an explanatory diagram showing the remaining capacity without current moving average processing, FIG. 5 is an explanatory diagram showing the remaining capacity with current moving average processing, and FIG. FIG. 7 is a flowchart of battery remaining capacity estimation processing, FIG. 8 is an explanatory diagram of a current capacity table, FIG. 9 is an explanatory diagram of an impedance table, and FIG. 10 is an explanatory diagram of a remaining capacity table. FIG. 11 is an explanatory diagram of the weight table.

  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 V of the battery 2 measured by the voltage sensor 4, the charge / discharge current I of the battery 2 measured by the current sensor 5, and the temperature (cell) of the battery 2 measured by the temperature sensor 6. Based on (temperature) T, the state of charge (SOC), that is, the remaining capacity SOC (t) is calculated every predetermined time t. This remaining capacity SOC (t) is output from the arithmetic 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, for vehicle control. Used as basic data, battery remaining amount, display data for warning, and the like. Note that the remaining capacity SOC (t) is also used as data (base value at the time of remaining capacity calculation by current integration, which will be described later) SOC (t−1) in a periodical calculation.

  Further, the calculation ECU 3 always determines whether or not the estimated value (calculated value) of the remaining capacity SOC is normal in the periodic calculation of the remaining capacity SOC. When the SOC value becomes abnormal, a fail signal is output to the HEV control ECU 10 to quickly shift to fail-safe control. When the estimated value of the remaining capacity SOC is greatly deviated from the true value due to a temporary disturbance, the arithmetic ECU 3 obtains an approximate remaining capacity using the terminal voltage of the battery 2, and this approximate remaining capacity. The base value (initial value) is used as the base value (initial value) to continue self-recovery to converge to the true value by continuing the periodic calculation, thereby minimizing the influence on the HEV control system.

  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 FIG. In this SOC estimation algorithm, parameters that can be measured by the battery 2, that is, the terminal voltage V, current I, and temperature T are used as the first remaining capacity based on the current integration by the function as the first to third calculation means. Of the remaining capacity SOCc and the remaining capacity SOCv as the second remaining capacity based on the estimated value of the battery open-circuit voltage are calculated in parallel, and the remaining capacity SOC as the third remaining capacity synthesized by weighting each is calculated. The final remaining capacity of the battery 2 is calculated.

  Further, the arithmetic ECU 3 calculates an approximate value of the remaining capacity SOC based on the terminal voltage of the battery 2 in order to cope with the case where the estimated value (calculated value) of the remaining capacity SOC becomes abnormal. A function is provided as an initial value calculation means for making an initial value when calculating the remaining capacity SOCc of current integration. The function as the initial value calculation means will be described later.

  In general, as a technique for calculating the remaining capacity of a battery, there are a technique for obtaining a remaining capacity based on an integrated value of the battery current and a technique for obtaining a remaining capacity based on an open voltage of the battery. is there. 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. On the other hand, when the load fluctuates greatly in a short time, the impedance for estimating the open-circuit voltage can be obtained accurately. There is a drawback that the calculated value of the remaining capacity cannot be vibrated easily.

Therefore, in the present SOC estimation algorithm, the remaining capacity SOCc (t) obtained by integrating the current I and the remaining capacity SOCv (t) obtained from the estimated value of the battery open voltage are determined according to the usage state of the battery 2. By weighting with a weight (weighting coefficient) w that changes as needed, the disadvantages of both the remaining capacities SOCc and SOCv are canceled out and the mutual advantages are maximized. The weight w is changed between w = 0 and 1, and the final remaining capacity SOC (t) after synthesis is given by the following equation (1).
SOC (t) = w.SOCc (t) + (1-w) .SOCv (t) (1)

  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 SOCc and SOCv. Etc. can be used. The current change rate per unit time directly reflects the load fluctuation of the battery, but the mere current change rate is affected by a sudden change in current that occurs in a spike manner.

  Therefore, in this embodiment, in order to prevent the influence of the spike-like current change, the current change rate subjected to processing such as a simple average, a moving average, a weighted average, etc. of a predetermined sampling number is used. In consideration of the current delay, the weight w is determined using a moving average that can appropriately reflect the past history without excessively changing the charge / discharge state of the battery. .

  By determining the weight w based on the moving average value of the current I, when the moving average value of the current I is large, the weight of the remaining capacity SOCc based on the current integration is increased, and the remaining capacity based on the estimated value of the open circuit voltage. It is possible to reduce the weight of the SOCv, accurately reflect the influence of load fluctuation by current integration, and prevent vibration during open circuit voltage estimation. Conversely, when the moving average value of the current I is small, the weight of the remaining capacity SOCc based on the current integration is lowered and the weight of the remaining capacity SOCv based on the estimated open circuit voltage is increased, thereby accumulating errors during current integration. Thus, the remaining capacity can be accurately calculated by estimating the open circuit voltage.

  That is, the moving average of the current I becomes a low-pass filter with respect to the high frequency component of the current, and the moving average filtering can remove the spike component of the current generated by the load fluctuation during traveling without promoting the delay component. it can. As a result, the battery state can be grasped more accurately, the disadvantages of both the remaining capacities SOCc and SOCv can be canceled, the mutual advantages can be maximized, and the estimation accuracy of the remaining capacities can be greatly improved.

  Further, as a feature of the present SOC estimation algorithm, the internal state of the battery is electrochemically grasped based on the battery theory, and the calculation accuracy of the remaining capacity SOCv based on the battery open voltage is improved. Hereinafter, the calculation of the remaining capacities SOCc and SOCv by this estimation algorithm will be described in detail.

First, as shown in the following equation (2), the remaining capacity SOCc by current integration is obtained by integrating the current I every predetermined time with the remaining capacity SOC synthesized using the weight w as a base value. Note that the calculation of the remaining capacity SOCc (t) by the equation (2) is specifically executed by discrete time processing in the calculation ECU 3, and the combined remaining capacity SOC (t-1) one calculation cycle before is calculated as the current integration. It is input as a base value (delay operator Z ⁻¹ in the block diagram of FIG. 2).
SOCc (t) = SOC (t−1) −∫ [(100ηI / Ah) + SD] dt / 3600 (2)
Where η: current efficiency
Ah: Current capacity (variable depending on temperature)
SD: Self-discharge rate

  Further, the current efficiency η and the self-discharge rate SD in the formula (2) can be regarded as constants (for example, η = 1, SD = 0), but the current capacity Ah changes depending on the temperature. Therefore, when calculating the remaining capacity SOCc by this current integration, the current capacity Ah calculated by functionalizing the variation of the cell capacity with temperature is used.

  On the other hand, in order to obtain the remaining capacity SOCv based on the estimation of the open circuit voltage, first, the internal impedance Z of the battery is 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. Accordingly, the moving average value of the current I per unit time described above is used as a frequency component replacement as a parameter for determining the impedance Z, and impedance measurement is performed on the condition of the moving average value of the current I and the temperature T. After accumulating data, an impedance Z table (an impedance table in FIG. 9 described later) is created based on the temperature T and the moving average value of the current I per unit time. Then, the impedance Z is obtained using this table, and the estimated value of the open circuit voltage Vo is obtained from the impedance Z, the measured terminal voltage V, and the current I using the following equation (3).
V = Vo-I · Z (3)

  As described above, the moving average value of the current I is also used as a parameter for determining the weight w, and the calculation of the weight w and the impedance Z is facilitated. Since the internal impedance increases and the current change rate decreases, as will be described later, the weight w and the impedance Z are directly set to the corrected current change rate kΔI / Δt obtained by temperature-correcting the moving average value of the current I. Use to determine.

After the open circuit voltage Vo is estimated, the remaining capacity SOCv is calculated based on the electrochemical relationship in the battery. Specifically, a well-known Nernst equation describing the relationship between the electrode potential and the ion activity in an equilibrium state is applied, and the relationship between the open circuit voltage Vo and the remaining capacity SOCv is expressed by the following (4). The formula can be obtained.
Vo = 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 SOC as shown in the following equation (5).
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (5)

  From the above equation (4), it can be seen that the remaining capacity SOCv has a strong correlation not only with the open circuit voltage Vo but also with the temperature T. In this case, the remaining capacity SOCv can be calculated directly using the equation (4) using the open-circuit voltage Vo and the temperature T as parameters. Consideration of conditions is necessary.

  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 SOC-Vo characteristics at room temperature, and the measured data is obtained. accumulate. Then, a table of remaining capacity SOCv (remaining capacity table of FIG. 10 described later) using open circuit voltage Vo and temperature T as parameters is created from the accumulated measured data, and the remaining capacity SOCv is obtained using this table. . Then, as shown in the above equation (1), the remaining capacity SOCc based on the current integration and the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo are weighted and synthesized using the weight w, and the final remaining capacity SOC is obtained. Is calculated.

  Here, when the influence of the presence or absence of the current moving average process in the calculation of the remaining capacity is compared, when the remaining capacity SOCv is calculated without performing the current moving average process, as shown in FIG. Under the influence of the components, a rapid change in the local remaining capacity SOCv occurs, which causes a decrease in the accuracy of the final combined remaining capacity SOC. On the other hand, when the remaining capacity SOCv is calculated by performing the current moving average process, the influence of the spike component of the current is removed from the remaining capacity SOCv, as shown in FIG. It is possible to accurately grasp the remaining capacity below.

  The calculation result of the remaining capacity during actual traveling is shown in FIG. 6, and the remaining capacity SOCc obtained by current integration and the remaining capacity SOC after synthesis in the state where the cell temperature is approximately 45 ° C. under relatively up-and-down traveling conditions. Changes are shown. In the state in which the battery is repeatedly charged and discharged until the elapsed time of about 1500 seconds shown in FIG. 6, the calculation result of the remaining capacity SOCc by current integration is reflected well in the combined remaining capacity SOC. Further, after the elapsed time of 1500 seconds, in a state where the charge amount of the battery tends to increase, the increase in the remaining capacity SOCc due to current integration tends to slow down and the error tends to increase, but the remaining capacity SOCv ( (Not shown) is reflected on the combined remaining capacity SOC with an increased weight, and the combined remaining capacity SOC rises as the amount of charge increases, and the change in the remaining capacity is accurately captured.

  As described above, the remaining capacity SOC is synthesized by combining the remaining capacity SOCc based on the current integration and the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo using the weight w that is changed as needed according to the battery usage status. Thus, the calculation accuracy is improved. At this time, as described above, the remaining capacity SOCc (t) of the current integration in the current control cycle is divergent because the combined remaining capacity SOC (t−1) one calculation cycle before is used as the base value. In addition, even if the remaining capacity SOC (t-1) deviates from the true value, it can be converged to the true value after a predetermined time has elapsed (for example, after several minutes).

  However, if a disturbance occurs for some reason, for example, the remaining capacity SOC (t−1) is true due to strong noise on the data communication line between the power supply unit 1 and the HEV control ECU 10. In the case of a large deviation from the value, the remaining capacity SOC (t-1) greatly deviating from the true value is used as it is as the base value for current integration, so it takes a long time to converge to the true value, and HEV control There are concerns about adverse effects on the system.

  Accordingly, when it is determined that the remaining capacity SOC is significantly different from the true value due to disturbance or the like, the arithmetic ECU 3 creates the battery open voltage Vo and temperature T as parameters by the function as the initial value calculation means. The table of the remaining capacity SOCv (remaining capacity table in FIG. 10 described later) is referred to using the terminal voltage V instead of the open circuit voltage Vo, and the remaining capacity SOCv obtained from the table is used as the combined remaining capacity SOC. Use approximately. Thereafter, the approximate remaining capacity SOC is used as a base value (initial value) to calculate the current accumulated remaining capacity SOCc, and by continuing the process of combining with the remaining capacity SOCv based on the open circuit voltage Vo, the HEV control is performed. It is possible to converge to the true value in a time that does not give an adverse effect.

  Next, calculation and synthesis processing of the remaining capacities SOCc and SOCv according to the above SOC estimation algorithm, self-recovery with respect to disturbance, and processing at the time of abnormality will be described using the flowchart of FIG.

  The flowchart of FIG. 7 shows basic processing for estimating the remaining battery capacity in the arithmetic ECU 3 of the power supply unit 1. In FIG. 7, for the convenience of explanation, it is opened following the calculation of the remaining capacity SOCc by current integration. Although the remaining capacity SOCv is calculated based on the estimation of the voltage Vo, the remaining capacity SOCc and SOCv are actually calculated in parallel.

  The battery remaining capacity estimation process in FIG. 7 is executed every predetermined time (for example, every 0.1 sec). First, in step S1, the terminal voltage V, current I, temperature T of the battery 2 and the previous calculation process are performed. The presence or absence of data input of the remaining capacity SOC (t-1) that is sometimes estimated and synthesized is checked. The terminal voltage V is the average value of the plurality of battery packs, and the current I is the sum of the currents of the plurality of battery packs. For example, data is acquired every 0.1 sec. The temperature T is acquired every 10 seconds, for example.

  As a result, if there is no new data input in step S1, this process is left as it is. If there is new data input, the process proceeds from step S1 to step S2, and the remaining capacity SOC (estimated one calculation cycle before) Whether t-1) is normal or not is determined. Whether the remaining capacity SOC (t-1) is normal is, for example, a value that is extremely deviated, such as 15%, while the normal remaining capacity SOC is in the range of 40 to 80%. If the value of the remaining capacity SOC (t−1) is consistent, such as when the original convergence of the SOC estimation algorithm is not satisfied, the battery terminal voltage V and the open-circuit voltage Vo are significantly different, etc. It can be determined by.

  In the present embodiment, the voltage obtained by applying the remaining capacity SOC (t−1) to the table of the remaining capacity SOCv created using the terminal voltage V of the battery 2, the open circuit voltage Vo of the battery, and the temperature T as parameters. If the voltage difference does not shrink below the set value within a certain time, or if the state exceeding the predetermined upper limit value continues for more than the set time, the remaining capacity is determined. It is determined that SOC (t-1) is not normal.

  If the result of determination in step S2 is that the remaining capacity SOC (t-1) is normal, the arithmetic processing from step S2 to step S3 is executed, and the remaining capacity SOC (t-1) is abnormal. In this case, the self-recovery / abnormal process from step S2 to step S10 and thereafter is executed.

  First, the processing after step S3 when the remaining capacity SOC (t-1) is normal will be described. In step S3, the battery current capacity is calculated with reference to the current capacity table shown in FIG. This current capacity table stores a capacity ratio Ah ′ with respect to a rated capacity (for example, a rated current capacity when a predetermined number of cells in one battery pack is used as a reference unit) with the temperature T as a parameter. However, the current capacity decreases as the temperature becomes lower than the capacity ratio Ah ′ (= 1.00) at room temperature (25 ° C.), and therefore the value of the capacity ratio Ah ′ increases. Using the capacity ratio Ah ′ referred to from the current capacity table, the current capacity Ah at the temperature T for each measurement target is calculated.

  Next, the process proceeds to step S4, where the current capacity Ah obtained from the current capacity table, the input value of the current I, and the composite remaining capacity SOC (t-1) before one calculation cycle are used, and the current is The remaining capacity SOCc (t) is calculated by integration. Furthermore, in step S5, the current I is subjected to a moving average to obtain a current change rate ΔI / Δt per unit time. For example, when the current I is sampled every 0.1 sec and the current integration calculation cycle is every 0.5 sec, the moving average is a moving average of five data.

  In subsequent step S6, the impedance Z of the battery equivalent circuit is calculated with reference to the impedance table shown in FIG. 9, and the open circuit voltage Vo of the battery 2 is estimated from the obtained impedance Z. This impedance table stores the impedance Z of the equivalent circuit with the corrected current change rate kΔI / Δt obtained by correcting the temperature of the current change rate ΔI / Δt (moving average value of the current I per unit time) and the temperature T as parameters. In general, when the corrected current change rate kΔI / Δt is the same, the impedance Z increases as the temperature T decreases. At the same temperature, the corrected current change rate kΔI / Δt is The impedance Z tends to increase as it decreases.

  Thereafter, the process proceeds to step S7, the voltage-SOC characteristic is calculated, and the remaining capacity SOCv is calculated. That is, the remaining capacity SOCv is calculated with reference to the remaining capacity table shown in FIG. 10 using the temperature T and the estimated open circuit voltage Vo as parameters. As described above, this remaining capacity table is a table created by grasping the electrochemical state in the battery based on the Nernst equation. In general, the lower the temperature T and the open circuit voltage Vo, the lower the capacity T. The remaining capacity SOCv tends to increase as the temperature T and the open circuit voltage Vo increase.

  In FIGS. 9 and 10, data in a range used under normal conditions is shown, and data in other ranges is omitted.

  Thereafter, the process proceeds to step S8, 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 kΔI / Δt as a parameter. In general, the smaller the corrected current change rate kΔI / Δt, that is, the smaller the battery load fluctuation, There is a tendency that the value of w is decreased to reduce the weight of the remaining capacity SOCc by current integration. In step S9, according to the above-described equation (1), the remaining capacity SOCc obtained by current integration and the remaining capacity SOCv estimated by the open circuit voltage Vo are weighted using the weight w to obtain the final remaining capacity SOC (t). The combined calculation is performed, and one cycle of the calculation process is completed.

  On the other hand, in the self-recovery / abnormal process when it is determined that the remaining capacity SOC (t−1) before one calculation cycle is not normal and the process proceeds from step S2 to step S10, the remaining capacity based on the current integration is determined in step S10. It is determined whether or not the difference between the SOCc and the remaining capacity SOCv based on the open circuit voltage Vo is within a reference value (for example, the difference between the remaining capacities SOCc and SOCv is instantaneously within about 10%). This is a determination for discriminating between a temporary abnormality caused by a disturbance and an irrecoverable abnormality caused by a failure of the voltage sensor 4, the current sensor 5, the temperature sensor 6, etc. If it does not shrink below the value, or if the state exceeding the reference value continues for more than the set time, it is determined that there is an abnormality due to sensor failure or the like, and otherwise, it is determined that there is an abnormality due to disturbance.

  If it is determined that there is an abnormality due to a sensor failure or the like, the process proceeds from step S10 to step S11, and the fail output from the arithmetic ECU 3 is transmitted to the HEV control ECU 10. In the event of a sensor failure, the calculation ECU 3 continues the calculation of the remaining capacity SOC with a certain degree of accuracy as much as possible, and enables traveling such as entering a repair shop and limp home to ensure safety.

  For example, when either one of the voltage sensor 4 and the current sensor 5 fails and the temperature sensor 6 is normal, the sensor is selected from the remaining capacity SOCv based on the open circuit voltage estimation and the remaining capacity SOCc based on the current integration. The calculation of the data that cannot be normally obtained due to a failure is stopped, and the remaining capacity calculated based on normal data with the weight w fixed to “0” or “1” is set as the combined remaining capacity SOC. Thus, a certain degree of accuracy can be ensured.

  Further, when the temperature sensor 6 fails and both the voltage sensor 4 and the current sensor 5 are normal, the internal impedance Z of the battery changes depending on the temperature, and therefore, based on the voltage V and the current I. The internal impedance Z is simply calculated, and the temperature T is estimated using the impedance table (see FIG. 9). Then, by using the estimated temperature as a temperature calculation parameter in each calculation of the remaining capacities SOCv and SOCc, a certain degree of accuracy can be ensured by performing the same calculation as during normal operation.

  If it is determined in step S10 that there is an abnormality due to disturbance, the process proceeds from step S10 to step S12, and whether or not the approximate value of the remaining capacity SOC can be calculated by the terminal voltage V of the battery 2 is determined by the current change rate ΔI. This is determined from / Δt, HEV control information indicating the operation state, and the like. That is, in a state where the load fluctuation of the battery 2 is intense such that an inrush current of the motor 15 is generated, it is difficult to accurately grasp the battery state by the terminal voltage V. The approximate value of the remaining capacity SOC is calculated by avoiding the current change rate ΔI / Δt and HEV control information.

  As a result, when it is determined that the approximate remaining capacity SOC can be calculated based on the terminal voltage V, the process proceeds from step S12 to step S13, and the remaining capacity table of FIG. 10 is changed to the battery temperature T and the open circuit voltage Vo. Instead, referring to the battery temperature T and the terminal voltage V, the remaining capacity SOCv obtained from the table is obtained as an approximate remaining capacity SOC. Then, the process proceeds from step S13 to the calculation process after step S3 described above, and the weight of the remaining capacity SOCc calculated based on the approximate remaining capacity SOC as the base value (initial value) and the remaining capacity SOCv based on the open circuit voltage Vo is weighted. By performing synthesis using w, self-recovery with respect to disturbance is performed.

  If it is determined in step S12 that the battery load fluctuation is severe and calculation using the terminal voltage V of the battery is not possible, the process proceeds from step S12 to step S14, and the value of the remaining capacity SOC is set to an intermediate value. Forcibly set to 50% and output. Then, the process proceeds from step S14 to the calculation process after step S3 described above, and the remaining capacity SOCc of current integration is calculated using the remaining capacity SOC that is forcibly set to the intermediate value (50%) as the base value (initial value). By combining the capacity SOCc and the remaining capacity SOCv based on the open-circuit voltage Vo using the weight w, self-recovery is performed while reliably preventing divergence during the synthesis.

  As described above, when calculating the remaining capacity using the remaining capacity SOCc based on the current integration and the remaining capacity SOCv based on the estimated value of the open-circuit voltage, the weight w set according to the battery usage state is used to determine the mutual capacity. The calculation accuracy can be made uniform by optimizing the weighting. In addition, even when the calculation result becomes abnormal, it is possible to quickly converge to the true value, and the remaining capacity of the battery (power storage device) can be obtained accurately at all times.

System configuration diagram showing an example of application to a hybrid vehicle Block diagram showing the remaining battery capacity estimation algorithm Circuit diagram showing equivalent circuit model Explanatory diagram showing the remaining capacity without the current moving average process Explanatory diagram showing the remaining capacity with current moving average processing Explanatory drawing showing the remaining capacity calculation result during actual vehicle running Flowchart of remaining battery capacity estimation process Illustration of current capacity table Illustration of impedance table Explanation of remaining capacity table Illustration of weight table

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply unit 2 Battery 3 Calculation unit (1st, 2nd, 3rd calculation means, current integration initial value calculation means)
SOCc remaining capacity (first remaining capacity)
SOCv remaining capacity (second remaining capacity)
SOC remaining capacity (third remaining capacity)
I Charge / discharge current V Terminal voltage Vo Open voltage Z Impedance w Weight
Agent Patent Attorney Susumu Ito

Claims (3)

First calculating means for calculating a first remaining capacity based on an integrated value of the charge / discharge current of the electricity storage device;
Second computing means for calculating a second remaining capacity based on an open circuit voltage estimated from the internal impedance of the electricity storage device;
A third remaining capacity obtained by weighting and combining the first remaining capacity and the second remaining capacity using a weight set according to the usage state of the power storage device is used as a final remaining capacity of the power storage device. A third calculating means for calculating;
When the third remaining capacity is abnormal, an approximate value of the third remaining capacity is calculated based on the terminal voltage of the power storage device, and this approximate value is used for current integration when calculating the first remaining capacity. Current integrated initial value calculation means as an initial value of
The current integrated initial value calculating means includes:
An apparatus for calculating a remaining capacity of a power storage device, comprising: determining whether the third remaining capacity is abnormal based on a difference between a terminal voltage of the power storage device and an open circuit voltage . The current integrated initial value calculating means includes:
Further, the remaining capacity calculation unit of the electric storage device according to claim 1, wherein identifying an abnormality by abnormality failure due to disturbance on the basis of the difference between the first residual capacity and the second remaining capacity. The current integrated initial value calculating means includes:
When not calculating the approximate value in a state where the third remaining capacity is identified as abnormal by the disturbance, according to claim 2, wherein calculating a median value of the third remaining capacity as the initial value Device for remaining capacity of electricity storage device.

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