JP2005341760A - Hybrid vehicle battery management device - Google Patents

Abstract

An object of the present invention is to accurately grasp a change in battery impedance and reflect it in battery management.
A power generation request for impedance calculation is issued, the motor is operated as a generator, and when a time given by a set value TGEN has elapsed from the start of power generation, the battery current I1 and voltage V1 are measured to generate power. When the time given by the set value TNLD has elapsed after the end of power generation, the battery current I2 and the voltage V2 are measured again. Then, an impedance correction value is calculated by comparing the impedance calculated from the measured currents I1, I2 and voltages V1, V2 with the reference impedance obtained in the initial state, and the open-circuit voltage is estimated from the impedance table value. By using it for correcting the table value when calculating the remaining capacity, the accuracy of the remaining capacity is maintained even when the battery is deteriorated, and reflected in the battery management.
[Selection] Figure 11

Description

  The present invention relates to a battery management apparatus for a hybrid vehicle that calculates an impedance of a battery mounted on the hybrid vehicle and reflects the impedance in battery management.

  In recent years, in vehicles such as automobiles, an engine that uses gasoline or other fuel as a power source is used with a motor that generates driving force by electric power from a battery for the purpose of promoting low pollution and resource saving. In addition, hybrid vehicles are being developed that use both an engine and a motor. In such a hybrid vehicle, it is important to accurately grasp and manage the battery state, and in addition to basic parameters such as battery voltage, current, and temperature, the remaining capacity is calculated. Since the remaining capacity changes due to deterioration of the battery, it is difficult to maintain accuracy over a long period of time.

In order to cope with this, for example, Patent Document 1 discloses a remaining capacity at the time of stoppage based on an open voltage obtained from a battery voltage at the time of vehicle stop of an electric vehicle, and discharge electric capacity based on an integrated value of the discharge current of the battery. The full charge capacity is calculated from the discharge electric capacity and the remaining capacity at stop, the degree of deterioration is calculated from the full charge capacity and the nominal full charge capacity, and the remaining capacity in consideration of the degree of deterioration is detected. Techniques to do this are disclosed.
JP-A-6-242193

  However, in the technique disclosed in Patent Document 1, the open circuit voltage is obtained from the battery voltage when the vehicle is stopped. However, when the battery is deteriorated, it is not considered that the internal impedance increases and the open circuit voltage changes. In an electric vehicle, since an electric current flows through a load such as an inverter even when the motor is stopped, an accurate open-circuit voltage cannot always be detected. In other words, the technique disclosed in Patent Document 1 limits the scope of application, and is insufficient for accurately managing the state of the battery mounted on the hybrid vehicle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery management device for a hybrid vehicle that can accurately grasp a change in battery impedance and reflect the change in battery management.

  In order to achieve the above object, a battery management apparatus for a hybrid vehicle according to the present invention supplies power to a motor that is coupled to an engine and assists the driving force of the engine, and is charged by the power generated by the motor. A battery management device for a hybrid vehicle that manages the state of the battery, wherein at least when the remaining capacity, current, and temperature of the battery are within a set range, the motor is operated to generate power, and the voltage / current of the battery during power generation is And measuring the voltage and current of the battery after power generation is completed, calculating impedance of the battery from the measured voltage and current, impedance calculated by the impedance calculating means, and the battery in advance Compared to the reference impedance obtained in the initial state of Characterized by comprising an impedance correction value calculating means for obtaining a correction value of the impedance in accordance with the time.

  At that time, when the speed of the hybrid vehicle is equal to or less than the set value, the motor is controlled to the set rotation speed and the engine is operated at the set torque to cause the motor to generate electricity, and the engine speed and torque are below the set range and When the required torque of the motor is zero, it is desirable to cause the motor to perform a power generation operation by operating the engine with an instruction torque obtained by adding a torque calculated from an electric energy preset for impedance calculation and the engine speed.

  Impedance can be calculated by dividing the voltage difference between power generation and after power generation by the current difference between power generation and after power generation, and the weighted average of the difference between the calculated impedance and the reference impedance The correction value of the impedance corresponding to the degree of deterioration of the battery can be obtained from the value or a value obtained by weighted averaging the ratio between the calculated impedance and the reference impedance. It is desirable to monitor the torque request from the control system and forcibly terminate the operation related to the calculation of the impedance when there is a torque request.

  Also, when calculating the remaining capacity of the battery, it is desirable to correct the impedance read from the table with a correction value according to the degree of deterioration of the battery. From the open-circuit voltage estimated using the corrected impedance, it is highly accurate. The remaining capacity can be calculated. This remaining capacity is weighted by combining a first remaining capacity based on the integrated value of the charge / discharge current of the battery and a second remaining capacity based on the open circuit voltage of the battery using a weight set in accordance with the battery usage status. By doing so, it is possible to obtain a remaining capacity with uniform accuracy, taking advantage of both the remaining capacity due to current integration and the remaining capacity based on the open circuit voltage.

  The battery management device for a hybrid vehicle according to the present invention can accurately grasp the change in the impedance of the battery, and can reflect the change in the remaining capacity and the deterioration degree of the battery.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 11 relate to a first embodiment of the present invention, FIG. 1 is a system configuration diagram of a parallel hybrid vehicle, FIG. 2 is a block diagram showing an estimation algorithm of a remaining battery capacity, and FIG. 3 is an explanation of a current capacity table. 4 is a circuit diagram showing an equivalent circuit model, FIG. 5 is an explanatory diagram of an impedance table, FIG. 6 is an explanatory diagram showing characteristics of a temperature correction value, FIG. 7 is an explanatory diagram of a remaining capacity table, and FIG. 8 is a weight table. FIG. 9 and FIG. 10 are flowcharts showing the impedance calculation processing, and FIG. 11 is an explanatory diagram showing the system operation state at the time of impedance calculation.

  FIG. 1 shows a system configuration of a hybrid (HEV) vehicle. In this embodiment, a transmission 3 is mainly connected to an engine 1 for driving driving via a motor (motor generator) 2 for generating power and driving assist force. It is a connected parallel hybrid vehicle. A final gear 5 is connected to the output shaft of the transmission 3 via a gear 4, and traveling driving force is transmitted to driving wheels (not shown). The motor 2 is connected to an inverter 6 that converts DC power into AC power. The electric power from the battery 7 is supplied to the motor 2 via the inverter 6 to drive the motor 2, and the motor 2 generates power. Electric power is supplied to the battery 7 via the inverter 6 to charge the battery 7. The battery 7 is configured by connecting a plurality of battery packs in which a plurality of cells are sealed in series.

  The battery 7 is connected to a DC-DC converter 8 that converts a high DC voltage from the battery 7 into a low-voltage (12V) DC voltage. Power is supplied to low-voltage (12V) auxiliary machines, batteries, etc. (not shown). Further, an electronic control unit (ECU) 20 comprising a microcomputer or the like is connected to the battery 7, and the ECU 20 performs management of the battery 7 and HEV control for the engine 1 and the inverter 6.

  Battery management by the ECU 20 depends on the remaining capacity indicated by the state of charge (SOC) of the battery 7, the input / output possible power amount indicated by the maximum input / output power in the battery 7, the deterioration degree of the battery 7, and the like. The battery state is grasped, the battery 7 is cooled and charged after grasping the battery state, the abnormality detection and the protection operation at the time of the abnormality detection, etc. The impedance (internal impedance) of the battery 7 is calculated under certain conditions that make use of the characteristics of the vehicle and reflected in battery management.

  In other words, the impedance of the battery can be obtained from the relationship between the current during charging / discharging, the terminal voltage, and the open circuit voltage, but depends on many parameters such as the remaining capacity, temperature, and current, and therefore is calculated as appropriate during vehicle operation. For this purpose, complicated calculations are required. However, since the parallel hybrid vehicle has a characteristic that the engine and the motor are mechanically connected, the state of charge is always compulsorily created when calculating the impedance of the battery by utilizing the characteristic. Then, the impedance can be calculated based on the battery current and voltage measured under the certain conditions.

  The impedance calculated under certain conditions can be used directly when calculating the remaining capacity, input / output power amount, degree of deterioration, etc. Therefore, by the function as the impedance correction value calculation means, the battery is deteriorated by comparing it with the reference impedance that is obtained in advance when the battery is in the initial state (not deteriorated) and stored in the ECU 20. It is effective to use it as a correction value of impedance according to the above.

  Hereinafter, in the present embodiment, an example in which the calculation result of impedance under a certain condition is applied to a process of calculating the remaining battery capacity with high accuracy will be described.

  As is well known, the remaining capacity of the battery can be calculated based on the integrated value of the charge / discharge current or the open-circuit voltage obtained from the impedance. However, since the impedance increases as the battery deteriorates, the remaining capacity remains when the battery deteriorates. Capacity estimation accuracy deteriorates. Therefore, by calculating the change in impedance and reflecting it in the remaining capacity estimation algorithm, it is possible to maintain the remaining capacity calculation with high accuracy even when the battery is deteriorated.

  The remaining capacity in this embodiment is calculated according to the estimation algorithm shown in FIG. In this estimation algorithm, parameters that can be measured by the battery 7, that is, the terminal voltage V, current I, and temperature T are used, and the function as the remaining capacity calculation means performs the first remaining based on the current integration at every predetermined time t. The remaining capacity SOCc (t) as the capacity and the remaining capacity SOCv (t) as the second remaining capacity based on the estimated value of the battery open voltage Vo are calculated in parallel, and the remaining capacity is synthesized by weighting each. SOC (t) is the remaining capacity of the battery 7.

  The remaining capacity SOCc obtained by integrating the current I and the remaining capacity SOCv obtained by estimating the open-circuit voltage Vo have advantages and disadvantages, respectively. On the other hand, it is strong against load fluctuations such as inrush current. On the other hand, the remaining capacity SOCv based on the open-circuit voltage estimation can be obtained as a substantially accurate value during normal use, but the value may oscillate when the load greatly fluctuates in a short time.

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 Vo are determined according to the usage state of the battery 7. Thus, by combining the weights with weights (weighting factors) w that are changed as needed, the disadvantages of both the remaining capacities SOCc (t) and SOCv (t) are canceled 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 by using a parameter that can accurately represent the current battery usage status, and the parameters include a current change rate per unit time and a 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 a change in current that instantaneously stops, a current change rate that has been processed by a simple average, a moving average, a weighted average, or the like of a predetermined sampling number is used. In particular, when considering a delay in current, 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. I have to.

  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 current integration is increased to lower the weight of the open circuit voltage estimation, and the influence of the load fluctuation is While accurately reflecting by integration, vibration during open circuit voltage estimation can be prevented. Conversely, when the moving average value of current I is small, the effect of error accumulation during current integration is avoided by reducing the current integration weight and increasing the open-circuit voltage estimation weight. The remaining capacity can be calculated.

  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.

  Furthermore, as a feature of the present SOC estimation algorithm, the internal state of the battery is grasped electrochemically based on the battery theory, and the calculation accuracy of the remaining capacity SOCv based on the battery open voltage Vo 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.

  FIG. 3 shows an example of a current capacity table storing a capacity ratio Ah ′ with respect to a rated capacity with a temperature T as a parameter (for example, a rated current capacity with a predetermined number of cells as a reference unit). Since the current capacity decreases as the temperature becomes lower than the capacity ratio Ah ′ (= 1.00) at room temperature (25 ° C.), the value of the capacity ratio Ah ′ increases. Using the capacity ratio Ah ′ referred to from this current capacity table, the current capacity Ah at the temperature T for each measurement target can be calculated.

Further, the calculation of the remaining capacity SOCc (t) according to the equation (2) is specifically executed by discrete time processing in the ECU 20, and the combined remaining capacity SOC (t−1) one calculation cycle before is used as a base for current integration. It is input as a 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 Vo, the estimated value of the open circuit voltage Vo is calculated from the battery impedance Z, the measured terminal voltage V and the current I using the following equation (3). Ask. However, the current I is + on the discharge side.
Vo = I · Z + V (3)

  The battery impedance Z can be obtained using an impedance table created using the equivalent circuit model shown in FIG. The equivalent circuit of FIG. 4 is an equivalent circuit model in which the 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 AC impedance 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 storing the data, a table of impedance Z is created based on the temperature T and the moving average value of the current I per unit time.

  Note that the moving average value of the current I is obtained, for example, by moving and averaging five pieces of data when the sampling of the current I is performed every 0.1 sec and the calculation cycle of current integration is performed every 0.5 sec. As described above, the moving average value of the current I is also used as a parameter for determining the weight w and facilitates the calculation of the weight w and the impedance Z. In detail, the internal impedance of the battery decreases as the temperature decreases. Therefore, the weight w and the impedance Z are directly determined using the corrected current change rate KΔI / Δt obtained by temperature-correcting the moving average value of the current I.

  FIG. 5 shows an impedance table in which impedance Z is stored with the corrected current change rate KΔI / Δt obtained by correcting the temperature of current change rate ΔI / Δt (moving average value of current I per unit time) and temperature T as parameters. For example, 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 / As Δt decreases, the impedance Z tends to increase. In the table shown in FIG. 5 and FIG. 7, which will be described later, data in a range used under normal conditions is shown, and data in other ranges is omitted.

  The above impedance table is a table created on the assumption that the battery 7 is in an initial state (a state in which the battery 7 is not deteriorated). Therefore, when long-term use is considered, it is necessary to correct the impedance table value Z according to the degree of deterioration of the battery 7. By performing this correction, the remaining capacity SOC of the battery 7 is deteriorated. The estimation accuracy can be maintained with high accuracy.

The correction of the impedance table value Z can be performed by using the impedance Rn calculated under a certain condition created by taking advantage of the characteristics unique to the parallel hybrid vehicle. The details of this impedance calculation process will be described later. Basically, the engine 1 is operated at a constant torque and the motor 2 is rotated at a constant speed under the condition that the vehicle is substantially stopped and the disturbance caused by the electric load is suppressed. The motor 2 is operated as a generator to generate power for a set time. Then, the current I1 and voltage V1 during power generation, the current I2 and voltage V2 after power generation are measured, and the impedance Rn is calculated by the following equation (4) using the measured currents I1 and I2 and voltages V1 and V2. .
Rn = | V1-V2 | / | I1-I2 | (4)

Further, as shown in the following equation (5-1), a difference Re between the calculated impedance Rn and the reference impedance Rr for correction calculation is obtained, and as shown in the following equation (6-1), the difference Re The weighted average value Rc is calculated as a learning value for impedance correction. The reference impedance Rr is an impedance calculated under the same conditions as described above in the initial state (not deteriorated) of the battery 7.
Re = Rn−Rr (5-1)
However, Re> 0
Rc = (1-a) · Rc + a · Re (6-1)
Where a: weighted average weight (0 <a <1; for example, a = 1/16)

Then, the table value Z of the impedance is corrected by using the learning value Rc described above, and the above equation (3) for obtaining the estimated value of the open circuit voltage Vo is replaced with the following equation (3-1) to calculate the open circuit voltage Vo. By obtaining, it is possible to appropriately reflect the change in impedance that changes according to the deterioration of the battery.
Vo = I · (Z + Rc) + V (3-1)

In this case, as shown in the following equation (3-2), a temperature correction value KT using temperature as a parameter may be used. As shown in FIG. 6, this temperature correction value KT is set to KT = 1 at a predetermined reference temperature. The lower the reference temperature, the larger the temperature correction value KT, and the higher the reference temperature, By reducing the temperature correction value KT, the impedance that changes depending on the temperature is compensated.
Vo = I · (Z + Rc · KT) + V (3-2)

For impedance correction, the ratio Kre between the impedance Rn and the reference impedance Rr shown in the following equation (5-2) is used instead of the difference Re between the impedance Rn and the reference impedance Rr, and the following (6-2) As shown in the equation, the weighted average value Krc of the ratio Kre may be used as the learning value.
Kre = Rn / Rr (5-2)
However, Kre> 1
Krc = (1-a) · Krc + a · Kre (6-2)
Where a: weighted average weight (0 <a <1; for example, a = 1/16)

Using the ratio Kre between the calculated impedance Rn and the reference impedance Rr means that the temperature correction is canceled, and therefore no temperature correction is required for impedance correction. The above equation (3) for obtaining the estimated value of the open-circuit voltage Vo from the impedance table value Z can be replaced by the following equation (3-3), and correction for deterioration can be performed in a simpler manner without depending on the temperature condition. It can be performed.
Vo = I · Z · Krc + V (3-3)

After the open circuit voltage Vo is estimated, the remaining capacity SOCv is calculated based on the electrochemical relationship in the battery. Specifically, when the well-known Nernst equation describing the relationship between the electrode potential and the ion activity in the equilibrium state is applied and the relationship between the open circuit voltage Vo and the remaining capacity SOCv is expressed, the following (7) The formula can be obtained.
Vo = E + [(Rg · T / Ne · F) × lnSOCv / (100−SOCv)] + Y (7)
However, E: Standard electrode potential (for example, E = 3.745 in a lithium ion battery)
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)

In Equation (7), Y is a correction term, and the voltage-SOC characteristic at normal temperature is expressed as a function of SOC. If SOCv = X, it can be expressed by a cubic function of SOC as shown in the following equation (8).
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (8)

  From the above equation (7), it can be seen that the remaining capacity SOCv has a strong correlation with the temperature T as well as the open circuit voltage Vo. In this case, the remaining capacity SOCv can be calculated directly using the equation (7) 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 (7), a charge / discharge test or simulation in each temperature range is performed on the basis of the SOC-Vo characteristic at normal temperature, and the measured data is obtained. accumulate. Then, a table of the remaining capacity SOCv that parameters the open circuit voltage Vo and the temperature T is created from the accumulated measured data, and the remaining capacity SOCv is obtained using this table. FIG. 7 shows an example of the remaining capacity table. Generally, the lower the temperature T and the open circuit voltage Vo, the smaller the remaining capacity SOCv, and the higher the temperature T and the open circuit voltage Vo, the remaining capacity. The capacity SOCv tends to increase.

  After calculating the remaining capacities SOCc and SOCv, as shown in the above equation (1), the remaining capacities SOCc and SOCv are weighted and synthesized using the weight w determined by referring to the table or the like, and the remaining capacities SOC are obtained. Is calculated. FIG. 8 shows an example of a weight table for determining the weight w, and is a one-dimensional table using the corrected current change rate KΔI / Δt as a parameter. This weight table generally indicates that the smaller the corrected current change rate KΔI / Δt, that is, the smaller the battery load fluctuation, the smaller the value of the weight w and the smaller the weight of the remaining capacity SOCc due to current integration. Have a tendency to

  Next, an impedance calculation process that changes as the battery deteriorates will be described with reference to the flowchart of the impedance calculation process shown in FIGS. In general, since the deterioration of the battery gradually proceeds, the substantial impedance calculation control execution frequency by this processing is low (for example, in one operation) when used for correction. The impedance calculation frequency may be about once.

  When the impedance calculation process of FIGS. 9 and 10 starts, first, in step S1, the counter CNT (initial value 0) is incremented (CNT = CNT + 1). This counter measures the time until the system state is stabilized in order to perform impedance calculation.

  Next, it progresses to step S2 and it is determined whether impedance calculation control is under way. If the impedance calculation control is already in progress, the process jumps to step S8. If the impedance calculation control is not in progress, it is checked in step S3 whether the counter CNT has reached the set value TCST. The set value TCST is an elapsed time that can be considered that the system is in a stable state when the impedance calculation process is executed for the first time, for example, the engine 1 has been warmed up after the system is started. In addition, a sufficient elapsed time (several tens of hours to about 1 hour) is provided for stabilizing the system.

  In step S3, if CNT <TCST, the process is temporarily exited. If CNT ≧ TCST, the process proceeds to step S4, and the vehicle speed is substantially stopped (eg, 2 Km / h) or less. It is determined whether or not the vehicle is stopped. As a result, if the vehicle is not in a substantially stopped state, the process is similarly exited. If the vehicle is in a substantially stopped state, the process proceeds to step S5.

  In step S5, the parameters affecting the impedance, that is, the remaining capacity SOC of the battery, the current I, and the temperature T are within the set ranges (for example, the remaining capacity SOC: 50 to 60%, the current I: −5 to +5 A, the temperature T: 30 to 40 ° C.). If any of the remaining capacity SOC, current I, and temperature T is out of the set range, the process exits from step S5, and if the remaining capacity SOC, current I, and temperature T are all within the set range, Proceeding from step S5 to step S6, initialization such as variable clearing is performed, and impedance calculation control is started.

  In step S7 following step S6, the control counter CIC is cleared (CIC = 0), and in step S8, the DC-DC converter 8 is turned off in order to stabilize the battery current by suppressing disturbance due to the electric load. In step S9, the control counter CIC is incremented (CIC = CIC + 1), and the process proceeds to step S10. The control counter is for monitoring the power generation time and the power generation end time in the impedance calculation control described below.

  In step S10, it is monitored whether or not the stop state is maintained (function as monitoring means). This is for monitoring the case where the vehicle is not stopped due to the drive request (torque request) from the HEV control system during the impedance calculation control, and terminating the impedance calculation control. When the vehicle is in a stopped state, the process proceeds from step S10 to step S11 and subsequent steps, and a set amount of power generation and a current / voltage measurement process are executed. If the vehicle is not stopped during this process, the process jumps from step S10 to step S20 to end the impedance calculation control, and in step S21, the DC-DC converter 8 is turned on to exit this process. In this case, the learning value is not updated based on the impedance calculation result, which will be described later, and erroneous impedance correction due to disturbance input can be avoided.

  In step S11 and subsequent steps, power generation is performed with a preset power generation amount and time, and current and voltage are measured. That is, in step S11, it is checked whether or not the control counter CIC is equal to or less than a set value TGEN that gives power generation time (for example, 10 seconds). If CIC> TGEN, the process jumps to step S13, and if CIC ≦ TGEN, the process goes to step S12. Then, a power generation request is issued and the motor 2 is driven by the engine 1 to generate power. Since this power generation is not possible to arbitrarily set the engine speed in a parallel hybrid vehicle, the motor 2 is controlled to a preset speed (for example, 800 rpm) and the engine 1 is operated at a preset torque. A set amount of power is generated while maintaining the vehicle in a substantially stopped state.

  Then, after the power generation is performed, the process proceeds to step S13, and it is checked whether or not the control counter CIC is equal to the set value TGEN. As a result, when CIC ≠ TGEN, the process jumps from step S13 to step S16, and when CIC = TGEN, the process proceeds from step S13 to step S14, and at that time (a preset power generation time has elapsed since the start of power generation). The battery current I1 and voltage V1 at the time of measurement) are measured and recorded, and in step S15, the torque instruction to the engine 1 and the rotational speed control of the motor 2 are terminated, and the power generation is terminated.

  Thereafter, the process proceeds to step S16, and whether or not the control counter CIC has reached an addition value (TGEN + TNLD) of a set value TGEN that gives a power generation time and a set value TNLD that gives a set time (for example, 10 seconds) after the end of power generation. Find out. If CIC ≠ (TGEN + TNLD), the process exits, and when CIC = (TGEN + TNLD), the process proceeds to step S17, and the battery current at that time (when the set time has elapsed from the end of power generation). I2 and voltage V2 are measured and recorded.

  That is, as shown in FIG. 11, when a power generation request for impedance calculation is issued and the motor 2 is operated as a power generator to generate power, when the time given by the set value TGEN has elapsed from the start of power generation, the current of the battery I1 and voltage V1 are measured and power generation is completed. After the power generation is completed, when the time given by the set value TNLD has elapsed, the current I2 and voltage V2 of the battery are measured again to measure current and voltage. Has a delay. As a result, measurement can be performed under stable conditions, and impedance calculation accuracy can be improved.

  Thereafter, the process proceeds to step S18, and the impedance Rn is calculated by the above-described equation (4) using the measured currents I1, I2 and voltages V1, V2. Then, in step S19, the above-described equations (5-1) and (6 The learning value Rc according to the equation -1) or the learning value Krc according to the equations (5-2) and (6-2) is calculated and the learning value up to the previous time is updated. In step S20, the impedance calculation control is terminated, and in step S21, the DC-DC converter 8 is turned on to exit this processing. If the impedance calculation frequency is increased, the counter CNT is cleared in step 21.

  As described above, the learned value of impedance can be used as a correction value for compensating for battery deterioration when determining the remaining capacity SOC, and a highly accurate remaining capacity SOC can be obtained even when the battery is deteriorated.

  Next, a second embodiment of the present invention will be described. FIGS. 12 to 14 relate to the second embodiment of the present invention, FIGS. 12 and 13 are flowcharts showing impedance calculation processing, and FIG. 14 is an explanatory diagram showing a system operation state at the time of impedance calculation.

  The second form changes the condition for impedance calculation control so that the impedance can be calculated even when the vehicle is running, compared to the first form described above. For this reason, a part of the impedance calculation process of the first embodiment (see FIGS. 9 and 10) is changed to the impedance calculation process shown in FIGS.

  Hereinafter, the steps different from the first embodiment will be mainly described. First, as shown in the flowchart of FIG. 12, in the second mode, the process of step S4 in the first mode for determining whether or not the vehicle is substantially stopped is changed to the process of steps S4-1 and S4-2. .

  When the counter CNT reaches the set value TCST through the same steps S1 to S3 as in the first embodiment, the process proceeds to step S4-1, and the engine speed NE and the command torque ETRQ are within the set range (for example, the engine speed). (NE: 1500 to 2000 rpm, engine command torque ETRQ: 40 to 80 Nm). Further, in step S4-2 following step S4-1, it is determined whether or not a condition that the required torque of the motor 2 (indicated torque to the motor 2) is zero is satisfied.

  If any of the conditions of Steps S4-1 and S4-2 is not satisfied, the process exits without performing the impedance calculation control, and both conditions are satisfied. In Step S5, the remaining capacity SOC, the current I, When the condition that the temperature T is within the set range is satisfied, the impedance calculation control is started in step S6.

  Then, through steps S7 to S9, instead of the process of step S10 for monitoring the stop state of the first form, the engine speed NE and the instruction torque ETRQ are monitored in step S10-1 shown in FIG. 13, step S10-2. The required torque of the motor 2 is monitored, and in step S12, a set amount of power generation is started.

In this case, as shown in the following equation (9), the motor torque GTRQ [unit: from the preset power generation amount GPWR [unit: W] for impedance calculation and the engine speed NE [unit: rpm] is calculated. Nm] is calculated, the motor torque GTRQ is added to the instruction torque to the engine 1 and the absorption torque at the motor 2 is used to start the power generation, and the motor torque GTRQ is reset to end the power generation.
GTRQ = GPWR / (NE / 2π) (9)

  That is, under the condition where there is no request for assist by the motor 2 in a constant running state, the required torque of the vehicle becomes the command torque to the engine, so that the power generation torque is added to the engine command torque as shown in FIG. By doing so, the impedance can be calculated without affecting the running state.

  During power generation, the torque request from the system side to the motor 2 may be canceled, thereby increasing the number of correction opportunities.

  The processing after step S12 is the same as that of the first embodiment, and the current I1 and the voltage V1 are measured after the set time has elapsed from the start of power generation to end the power generation. Current I2 and voltage V2 are measured, impedance is calculated using the measured currents I1 and I2, and voltages V1 and V2, and the learning value is updated.

  The conditions for stopping the impedance calculation control are as follows when the engine speed NE and the command torque ETRQ are out of the setting range according to the monitoring results of steps S10-1 and S10-2, or when the assist request or energy regeneration is performed. This is a time when there is a motor request torque other than the control. At this time, the impedance calculation control is forcibly terminated and the learning value is not updated.

  In the second mode, the impedance of the battery can be calculated even when the vehicle is running, and the remaining capacity at the time of battery deterioration can be maintained with higher accuracy by increasing the chance of correction.

  As described above, in each of the embodiments, it is possible to accurately grasp the change in the impedance of the battery, and this impedance change is used as a parameter representing the battery state such as the remaining capacity, the input / output power amount, and the degree of deterioration. By reflecting, accurate battery management can always be performed.

  In each of the embodiments described above, the parallel hybrid vehicle has been described. However, the present invention is not limited to the parallel hybrid vehicle, but can be applied to a series / parallel hybrid vehicle.

The system block diagram of a parallel hybrid vehicle according to the first embodiment of the present invention. As above, a block diagram showing an estimation algorithm of the remaining battery capacity Same as above, explanatory diagram of current capacity table Same as above, circuit diagram showing equivalent circuit model Same as above, explanatory diagram of impedance table Same as above, explanatory diagram showing characteristics of temperature correction value Same as above, explanatory diagram of remaining capacity table Same as above, illustration of weight table Same as above, flowchart showing impedance calculation processing Same as above, flowchart showing impedance calculation processing (continued) Same as above, explanatory diagram showing the system operating state at the time of impedance calculation The flowchart which shows an impedance calculation process in connection with 2nd Embodiment of this invention. Same as above, flowchart showing impedance calculation processing (continued) Same as above, explanatory diagram showing the system operating state at the time of impedance calculation

Explanation of symbols

1 Engine 2 Motor 7 Battery 20 Electronic control unit (impedance calculation means, impedance correction value calculation means, monitoring means, remaining capacity calculation means)
Rn impedance Rr reference impedance Z impedance (table value)
SOCc remaining capacity (first remaining capacity)
SOCv remaining capacity (second remaining capacity)
w weight
Agent Patent Attorney Susumu Ito

Claims (9)

A battery management device for a hybrid vehicle that supplies power to a motor that is coupled to an engine and assists the driving force of the engine, and manages the state of a battery that is charged by the power generated by the motor,
When at least the remaining capacity, current and temperature of the battery are within the set range, the motor is operated to generate power, and the voltage and current of the battery during power generation and the voltage and current of the battery after power generation is completed Impedance calculating means for calculating the impedance of the battery from the measured voltage / current,
Impedance correction value calculating means for comparing the impedance calculated by the impedance calculating means with a reference impedance obtained in advance in the initial state of the battery and obtaining a correction value of the impedance according to the degree of deterioration of the battery. A battery management device for a hybrid vehicle. The impedance calculation means is
The battery management device for a hybrid vehicle according to claim 1, wherein when the speed of the hybrid vehicle is equal to or lower than a set value, the motor is controlled to a set rotation speed and the engine is operated at a set torque. The impedance calculation means is
When the engine speed and torque are below the set range and the required torque of the motor is zero, the engine is added with the torque calculated from the amount of power preset for impedance calculation and the engine speed. The battery management device for a hybrid vehicle according to claim 1, wherein the battery management device is operated with a command torque. The impedance calculation means is
The impedance is calculated by dividing a voltage difference between power generation at a specified power generation amount and after completion of power generation by a current difference between power generation at a specified power generation amount and after completion of power generation. The battery management apparatus of the hybrid vehicle as described in any one of 1-3. The impedance correction value calculation means includes
5. The battery management apparatus for a hybrid vehicle according to claim 1, wherein a value obtained by weighted averaging the difference between the impedance calculated by the impedance calculation means and the reference impedance is calculated as the correction value. The impedance correction value calculation means includes
5. The battery management apparatus for a hybrid vehicle according to claim 1, wherein a value obtained by weighted averaging the ratio between the impedance calculated by the impedance calculation means and the reference impedance is calculated as the correction value.   The system further comprises monitoring means for monitoring a torque request from a control system for controlling the hybrid vehicle, and forcibly terminating the operation related to the impedance calculation when the torque request is received. Item 7. A battery management device for a hybrid vehicle according to any one of Items 1 to 6.   The impedance read from the table held in advance is corrected using the correction value calculated by the impedance correction value calculation means, the open voltage of the battery is estimated using the corrected impedance, and based on the estimated open voltage The battery management apparatus for a hybrid vehicle according to any one of claims 1 to 7, further comprising a remaining capacity calculation unit that calculates a remaining capacity of the battery. The remaining capacity calculation means is:
The first remaining capacity based on the integrated value of the charge / discharge current of the battery and the second remaining capacity based on the open circuit voltage of the battery are weighted and synthesized using weights set according to the use status of the battery, 9. The battery management apparatus for a hybrid vehicle according to claim 8, wherein the remaining capacity of the battery is calculated.

Images