JP2006038495A - Remaining capacity calculation device for power storage device - Google Patents

Abstract

The remaining capacity is always obtained with uniform accuracy by taking advantage of both the remaining capacity based on current integration and the remaining capacity based on open circuit voltage.
When a deviation between a remaining capacity SOCc based on current integration and a remaining capacity SOCv based on an estimated value of an open circuit voltage is equal to or less than a set value, a weight w corresponding to a normal state is used to weight and synthesize the remaining capacities SOCc and SOCv. Then, the remaining capacity SOC is calculated (S8, S14). On the other hand, when the deviation is larger than the set value, when the cell temperature is equal to or higher than the reference value, the weight w near the SOCv is calculated (S10), and the estimated value of the open circuit voltage is within the upper and lower limit voltage range when the cell temperature is lower than the reference value If the cell temperature is below the reference value and the estimated open circuit voltage deviates from the upper and lower limit voltage range, the weight of the remaining capacity SOCv is set to zero and the remaining capacity SOCc is output. Thus, the remaining capacity is always obtained with uniform accuracy.
[Selection] Figure 7

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 the 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, taking advantage of both the remaining capacity based on the current integration and the remaining capacity based on the open circuit voltage, and the remaining capacity of the electricity storage device that can always obtain the remaining capacity with uniform accuracy. It aims at providing a capacity | capacitance calculating device.

  In order to achieve the above object, an apparatus for calculating a remaining capacity of a power storage device according to the present invention includes a first calculation means for calculating a first remaining capacity based on an integrated value of charge / discharge currents of the power storage device, A second computing means for calculating a second remaining capacity based on an open-circuit voltage estimated from an internal impedance; and a third composition obtained by weighting and combining the first remaining capacity and the second remaining capacity using weights. A third calculating means for calculating a remaining capacity as a final remaining capacity of the power storage device; and a weight for adjusting the value of the weight according to a use environment of the power storage device and a transition of a calculated value of the remaining capacity. And adjusting means.

  At this time, when the deviation between the first remaining capacity and the second remaining capacity is equal to or less than the set value, it is desirable to adjust the weight value based on the current change rate of the charge / discharge current of the power storage device. When the deviation between the remaining capacity and the second remaining capacity exceeds the set value and the power storage device is equal to or higher than the reference temperature, it is desirable to adjust the weight value in a direction to increase the weight of the second remaining capacity.

  Further, when the deviation between the first remaining capacity and the second remaining capacity exceeds the set value and the storage device is lower than the reference temperature, the estimated open circuit voltage is within the range between the upper limit voltage and the lower limit voltage of the storage device. In this case, it is desirable to adjust the value of the weight in the direction of increasing the weight of the first remaining capacity, the deviation between the first remaining capacity and the second remaining capacity exceeds the set value, and the power storage device When the estimated value of the open circuit voltage deviates from the range between the upper limit voltage and the lower limit voltage of the electricity storage device in a state lower than the reference temperature, it is desirable to adjust the weight value so that the weight of the second remaining capacity is zero.

  The remaining capacity computing device for an electricity storage device of the present invention can always obtain the remaining capacity with uniform accuracy by taking advantage of both the remaining capacity based on current integration and the remaining capacity based on the open circuit voltage.

  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 the temperature (T), a state of charge (SOC), that is, a 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.

  As will be described later, the calculation ECU 3 calculates the remaining capacity SOC by calculating the data before one calculation cycle in the periodic calculation (base value when calculating the remaining capacity by current integration described later) SOC (t−1). Is used.

  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 SOCc and SOCv are weighted using the weight (weight coefficient) w. The combined remaining capacity SOC as the third remaining capacity is calculated as the remaining capacity of the battery 2. The weight w is adjusted according to the usage environment of the battery 2 and the transition of the calculated value of the remaining capacity by the function of the calculation ECU 3 as the weight adjusting means.

  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.On the other hand, the open-circuit voltage must be set when the load fluctuates greatly in a short time or when the battery voltage hysteresis becomes large. There is a drawback that the impedance at the time of estimation cannot be obtained accurately and the calculated value of the remaining capacity is likely to vibrate.

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-circuit voltage are used as the usage environment and the remaining capacity of the battery 2. By weighting with a weight (weighting coefficient) w that is changed as needed according to the transition of the calculated value, the disadvantages of both the remaining capacities SOCc and SOCv are canceled out and the mutual advantages are maximized. Yes. 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 is the current battery usage environment, for example, the current change rate of the charge / discharge current of the battery, the convergence of the estimated value of the remaining capacity SOC, the temperature condition for avoiding the influence of the voltage hysteresis, a predetermined battery It is determined in consideration of various conditions such as upper and lower limit voltages that guarantee the characteristics. In the present embodiment, the weight w is adjusted based on the current change rate and taking other conditions into consideration.

  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. The effects of spike-like current changes can be prevented by using current change rates that have undergone processing such as simple average, moving average, and weighted average of a predetermined number of samplings. In this case, it is desirable to use a moving average that can appropriately reflect the past history without excessively changing the charge / discharge state of the battery.

  Then, by determining the weight w based on the current change rate by the moving average, when the moving average value of the current I is large, the remaining capacity SOCc based on the open circuit voltage is estimated by increasing the remaining capacity SOCc based on the current integration. , The influence of load fluctuation can be accurately reflected by current integration, and vibration during open circuit voltage estimation can be prevented. 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.

  In this case, if the weight of the remaining capacity SOCc based on the current integration becomes excessively higher than necessary, the convergence speed to the true value decreases, so the remaining capacity SOCc based on the current integration and the remaining capacity based on the estimated value of the open circuit voltage. The deviation from the SOCv is monitored, and when this deviation becomes large, the convergence is improved by increasing the weight of the remaining capacity SOCv based on the estimated value of the open circuit voltage. In addition, at low temperatures, the estimation accuracy of the open-circuit voltage is deteriorated due to the influence of the voltage hysteresis of the battery 2, and the accuracy of the remaining capacity SOCv may be lowered. Therefore, the cell temperature is monitored, and an adverse effect of the voltage hysteresis is expected. When the temperature is lower than the reference temperature, the accuracy of the remaining capacity SOC is compensated by increasing the weight of the remaining capacity SOCc by current integration.

  Specifically, the weight w is stored in a weight table (see FIG. 11) created using the battery temperature T and the current change rate ΔI / Δt as basic parameters, and is determined with reference to this weight table. More specifically, as will be described later, as the temperature becomes lower, the internal impedance of the battery increases and the current change rate decreases, so the weight table parameter is a current change after correction in which the moving average value of the current I is temperature corrected. Further, a coefficient K1 that is varied according to conditions such as a deviation of the remaining capacities SOCc and SOCv, a temperature of voltage hysteresis, a voltage range of the estimated open circuit voltage, and the like, using the rate kΔI / Δt. Is used as a parameter K1 · kΔI / Δt.

  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.
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

  Although the current efficiency η and the self-discharge rate SD in the equation (2) can be regarded as constants (for example, η = 1, SD = 0), the current capacity Ah varies 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.

Further, 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 (initial value) (delay operator Z ⁻¹ in the block diagram of FIG. 2). Therefore, errors do not accumulate or diverge, and even if the initial value is significantly different from the true value, it should converge to the true value after a predetermined time (for example, after several minutes). Can do.

  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)

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 as 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 shown in FIG. 6 where the battery is repeatedly charged and discharged until the elapsed time of about 1500 seconds, the calculation result of the remaining capacity SOCc by current integration is well reflected 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.

  Next, calculation and synthesis processing of the remaining capacities SOCc and SOCv according to the above SOC estimation algorithm 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, and if there is new data input, the process proceeds from step S1 to step S2, and the battery current capacity is changed to the current capacity shown in FIG. Operate with reference to the table. 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 S3, 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 S4, 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 the subsequent step S5, 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 S6, 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 S7, and it is checked whether or not the deviation between 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 is equal to or less than a set value. This is to detect a case where the deviation of the remaining capacities SOCc and SOCv becomes large due to some factor such as a disturbance. The deviation of the remaining capacities SOCc and SOCv is determined by a parameter such as a moving average value of the current I. If it is equal to or less than the value, it is determined that the state is a normal state, and the process proceeds from step S7 to step S8 to calculate a weight w corresponding to the normal state.

  The weight w corresponding to the normal state is obtained by setting the coefficient K1 in the parameter K1 · ΔKI / Δt referring to the weight table shown in FIG. 11 to k1, that is, by referring to the table using the corrected current change rate kΔI / Δt as a parameter. Ask. The weight table is set to a characteristic in which the weight w is decreased to decrease the weight of the remaining capacity SOCc by current integration as the corrected current change rate kΔI / Δt decreases, that is, the battery load fluctuation decreases. Yes.

  Then, after calculating the weight w corresponding to the normal state, the process proceeds from step S8 to step S14, and the remaining capacity SOCc by current integration and the remaining capacity SOCv by estimation of the open circuit voltage Vo are weighted according to the above-described equation (1). Weighting is performed using w, and the final remaining capacity SOC (t) is synthesized and calculated, thereby completing one cycle of the calculation process.

  On the other hand, if the deviation of the remaining capacities SOCc and SOCv does not satisfy the condition that the deviation of the remaining capacities SOCc and SOCv is less than or equal to the set value and the deviation of the remaining capacities SOCc and SOCv exceeds the set value, the process proceeds from step S7 to step S9. It is determined whether or not the cell temperature is a reference value (for example, 10 ° C.) or less. This determination is for avoiding an increase in error due to unstable voltage estimation due to an increase in voltage hysteresis when the cell temperature is low, and when the cell temperature T is equal to or higher than a reference value. The process proceeds from step S9 to step S10, and the weight w near the open circuit voltage, that is, the weight of the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo is adjusted to be relatively higher than the remaining capacity SOCc based on the current integration. The weight w is calculated.

  The weight w close to the open circuit voltage makes the reference position of the table relatively far from w = 1 by setting the coefficient K1 in the reference parameter K1 · kΔI / Δt of the weight table shown in FIG. 11 to K1 <1.0. Thus, the value of the weight w is made smaller than in the normal state. Then, the process proceeds to step S14, and the final remaining capacity SOC (t) is synthesized according to the above-described equation (1) using the weight w adjusted to be close to the open circuit voltage, thereby completing one cycle of the present calculation process. To do. In this case, the final remaining capacity SOC is weighted more than usual, and the weight of the remaining capacity SOCc that is excessively larger than necessary can be reduced to speed up the convergence to the true value. .

  In step S9, if the cell temperature is in a low temperature state where the adverse effect of voltage hysteresis below the reference value is expected, the process proceeds from step S9 to step S11, where the estimated value of the open circuit voltage Vo is the upper limit voltage of the battery 2. It is checked whether or not the voltage is within the upper and lower limit voltages according to Vmax and the lower limit voltage Vmin. The upper limit voltage Vmax and the lower limit voltage Vmin of the battery 2 can be defined as a voltage giving an upper limit (100%) and a voltage giving a lower limit (0%) of the remaining capacity SOC, respectively. By using the table and referring to the upper and lower limits of the open circuit voltage Vo at the predetermined temperature T, the upper limit voltage Vmax and the lower limit voltage Vmin at the temperature T can be known.

  As a result, if the estimated value of the open-circuit voltage Vo deviates from the upper and lower limit voltage ranges of the battery 2 under a low temperature state in which adverse effects of voltage hysteresis are expected, an instantaneous voltage estimation error due to a sudden load fluctuation or the like The process proceeds from step S11 to step S12, the weight of the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo is set to zero (w = 1), and is not easily affected by transient voltage fluctuations. The remaining capacity SOCc resulting from the current integration is output as the final remaining capacity SOC, and this calculation process for one cycle is completed.

  Further, when the estimated value of the open circuit voltage Vo is within the upper and lower limit voltage range of the battery 2 under a low temperature state in which an adverse effect of voltage hysteresis is expected, the process proceeds from step S11 to step S13, and a weight near the current integration is reached. w, that is, the weight w adjusted so that the weight of the remaining capacity SOCc based on the current integration is relatively higher than the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo is calculated.

  The weight w closer to the current integration makes the reference position of the table relatively close to w = 1 by setting the coefficient K1 in the reference parameter K1 · kΔI / Δt of the weight table shown in FIG. 11 to K1> 1.0. The weight w is made larger than in the normal state. In step S14, the final remaining capacity SOC (t) is synthesized according to the above-described equation (1) using the weight w adjusted to be close to the current integration, thereby completing one cycle of the calculation process. . In this case, as the final remaining capacity SOC, the weight of the remaining capacity SOCc due to current integration is increased, and it is possible to obtain the remaining capacity SOC with stable accuracy by avoiding the influence of voltage hysteresis at low temperatures.

  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, depending on the usage environment of the battery and the transition of the calculated value of the remaining capacity. Each weight is optimized using the adjusted weight w. This prevents a decrease in calculation accuracy due to voltage hysteresis during load fluctuations or low temperatures, and improves convergence to the true value. The remaining capacity of the battery (power storage device) is always uniform and accurate. Can be requested.

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, weight adjustment 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 (5)

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;
Third computing means for calculating a third remaining capacity obtained by weighting and combining the first remaining capacity and the second remaining capacity using a weight as a final remaining capacity of the power storage device;
An apparatus for calculating a remaining capacity of a power storage device, comprising: weight adjusting means for adjusting the value of the weight according to a use environment of the power storage device and a transition of a calculated value of the remaining capacity. The weight adjusting means is
The weight value is adjusted based on a current change rate of a charge / discharge current of the power storage device when a deviation between the first remaining capacity and the second remaining capacity is equal to or less than a set value. Item 10. A remaining capacity calculation device for an electricity storage device according to Item 1. The weight adjusting means is
When the deviation between the first remaining capacity and the second remaining capacity exceeds a set value and the power storage device is equal to or higher than a reference temperature, the weight value is increased by increasing the weight of the second remaining capacity. The remaining capacity calculation apparatus for an electricity storage device according to claim 2, wherein The weight adjusting means is
When the deviation between the first remaining capacity and the second remaining capacity exceeds a set value and the power storage device is lower than a reference temperature, the estimated value of the open circuit voltage is the upper limit voltage and the lower limit voltage of the power storage device. 4. The apparatus for calculating a remaining capacity of an electricity storage device according to claim 3, wherein the weight value is adjusted in a direction to increase the weight of the first remaining capacity. The weight adjusting means is
When the deviation between the first remaining capacity and the second remaining capacity exceeds a set value and the power storage device is lower than a reference temperature, the estimated value of the open circuit voltage is the upper limit voltage and the lower limit voltage of the power storage device. 5. The remaining capacity calculation device for an electricity storage device according to claim 3, wherein the weight value is adjusted so that the weight of the second remaining capacity becomes zero when the value deviates from the range.

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