JP2000261905A - Battery control method for power generation type electric vehicle - Google Patents

Abstract

(57) [Problem] To provide a battery control method for a power generation type electric vehicle which is excellent in accuracy and usability. When the reference state battery voltage drops below the normal minimum voltage value Vp, an operation is performed to charge the battery near the normal maximum voltage value Vq and then discharge it to near the target voltage value Vc. In this way, the reference state battery voltage corresponding to the target voltage value Vc and the actual capacity value actually corresponding to the target voltage point with respect to the target coordinate point defined by the target voltage value Vc and the corresponding target capacity value are set. Capacitance deviation between them can be reduced favorably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery control method for a power generation type electric vehicle equipped with power generation means, such as a hybrid vehicle in which an engine and an electric motor driven by a chargeable / dischargeable battery are combined.

[0002]

2. Description of the Related Art In recent years, HV (hybrid) vehicles equipped with an engine and a motor driven by a battery have attracted attention for the purpose of improving fuel efficiency. The battery mounted on the HV vehicle is discharged mainly from the battery during a high load operation such as acceleration, and is charged during a low load operation such as deceleration or running at a constant speed. In order to stably charge and discharge such a battery, the SOC (State Of Charge) is used.
e / charged state) needs to be balanced at a predetermined constant value, so that SOC detection is an indispensable technique in battery control.

As a method of detecting the SOC (or remaining capacity) of a battery, a method based on integration of charge / discharge current (hereinafter also referred to as a current integration method) or a method for estimating the SOC based on battery voltage (hereinafter referred to as voltage) An estimation method is also known. Japanese Patent Application Laid-Open No. Hei 10-51906 discloses that, in view of the small voltage change in the middle SOC region, only the current / voltage map at the normal (permissible) upper limit or the normal (permissible) lower limit of the SOC is stored and detected. Current
The voltage is put into this map to estimate the SOC, and the estimated SOC
When the battery reaches a predetermined upper limit of the SOC, the battery is discharged. After that, a battery control has been proposed in which the charge / discharge cycle for charging the battery is forcibly repeated when the estimated SOC reaches a preset lower limit of the normal SOC.

[0004]

However, the current integration method is a method of sequentially detecting the charge / discharge current of the battery and infinitely accumulating (accumulating) the current in the initial value of the SOC. Accumulate, and it is difficult to obtain an accurate detection value. On the other hand, the voltage estimation method is
Although it does not have the above-mentioned cumulative error, it has a large charge polarization action like a nickel-metal hydride battery, for example, and the battery voltage and S
In a battery of the type in which the relationship with the OC greatly changes due to its charging / discharging history (also referred to as a large hysteresis battery), the relationship between the battery voltage and the SOC, or the relationship between the battery voltage, the current, and the capacity is stored in advance as a map. Voltage data or voltage / voltage
Even if the capacity is estimated by putting the current data into this map, the expected accuracy cannot be obtained.

Further, in the above-mentioned conventional publication, the SOC (capacity) is determined on the basis of the voltage / current data in the case of a high SOC value and the case of a low SOC value which can be detected relatively accurately with a large slope of the voltage-capacity characteristic. ) Make a detection and, based on the results,
Since the battery state must be forcibly reciprocated between a high SOC value and a low SOC value, when the battery state is forcibly shifted to a low SOC value side, it becomes difficult to obtain necessary power from the battery,
When the shift is forcibly shifted to the high SOC value side, it becomes difficult to store the regenerative electric power in the battery, the usability of the battery is deteriorated, and the running function and the fuel efficiency are deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a battery control method for a power-generating electric vehicle having excellent accuracy and ease of use.

[0007]

According to the configuration described in each of the claims for solving the above problems, it is possible to realize a battery control method for a power generation type electric vehicle which is excellent in accuracy and usability. The common features of the battery control method for a power generation type electric vehicle described in these claims will be described below.

First, a reference state battery voltage, which is a battery voltage at a predetermined reference current value or a predetermined reference power value, is calculated based on the measured voltage value and measured current value of the battery, and the calculated reference state battery is calculated. The voltage is a predetermined target voltage value Vc
The charge / discharge of the battery is controlled so that More specifically, in a battery of an electric vehicle (battery for storing running power), a charge / discharge current state or a charge / discharge power state has a use mode that changes every moment. On the other hand, the battery voltage varies depending on the magnitude of the current due to the effect of the internal resistance of the battery. Therefore, it is difficult to accurately estimate the capacity simply by introducing the measured battery voltage data into the map of the battery voltage and the capacity. Therefore, it is conceivable to store a map of battery voltage, current, and capacity, and to estimate the capacity by introducing battery voltage data and current data into the map. In this case, a three-dimensional map must be stored. This requires a large-scale memory.

[0009] In a large hysteresis battery such as a nickel-metal hydride battery, the relationship between the SOC and the battery voltage cannot be determined unconditionally due to the influence of charging polarization and the like. In order to solve this problem, in the present invention, the obtained battery voltage data and current data are once converted into a reference state battery voltage which is the battery voltage data in the reference current state or the reference power state. Then, a predetermined target voltage value Vc corresponding to the normal capacity range at the reference current value or the reference power value is set.

In this manner, the reference state battery voltage and the target voltage value Vc can be obtained without requiring a large-scale memory.
Charging and discharging so as to eliminate the difference between the battery voltage and the target voltage value Vc regardless of the current fluctuation.
Can be held in the capacity range corresponding to Secondly,
A normal minimum capacity value P on a discharge-time minimum voltage characteristic line indicating a capacity-voltage characteristic when the battery is discharged from a substantially fully charged state, and a charging maximum value indicating a capacity-voltage characteristic when the battery is charged from a substantially completely discharged state. Set the normal maximum capacitance value Q on the voltage characteristic line,
Since the battery does not reach from P to P or does not reach from P to Q, the battery capacity state (the reference state battery voltage-coordinate point on the capacity plane) is set between the normal maximum capacity value Q and the normal minimum capacity value P. In the normal capacity range. In order to set the capacity state to the point P or Q before the above, the battery may be discharged from a substantially fully charged state or charged from a substantially completely discharged state.

Third, battery voltage (reference state battery voltage)
Is converged to a predetermined target voltage value Vc between the normal maximum voltage value Vq and the normal minimum voltage value Vp corresponding to P and Q. In this way, when the reference state battery voltage matches the target voltage value Vc, the difference between the target capacity value corresponding to the target voltage value Vc and the actual capacity can be made very small. Further, by performing charge / discharge control so that the reference state battery voltage falls within the range of the normal maximum voltage value Vq and the normal minimum voltage value Vp, it is possible to prevent the actual capacity from deviating from the range PQ. it can.

Instead of operating so that the reference state battery voltage is within the range of the normal maximum voltage value Vq and the normal minimum voltage value Vp, the calculated capacity calculated by a method such as current integration is replaced with the normal maximum voltage value Vq. Even when charge / discharge control is performed to maintain the maximum capacity value Q and the minimum capacity value P corresponding to the common minimum voltage value Vp and the actual capacity deviates from the range PQ. Can be prevented.

[0013] Therefore, it is possible to reduce the fluctuation of the relationship between the battery voltage and the capacity due to the charging / discharging history, to maintain the capacity simply and accurately within the range of PQ to avoid overcharging and overdischarging. Can be. This will be described in more detail. An electric vehicle battery (battery for storing running power) has a use mode in which a charge / discharge current state or a charge / discharge power state changes every moment. On the other hand, in a large hysteresis battery such as a nickel-metal hydride battery, the discharge voltage and the charge voltage are different due to the influence of charge polarization and the like, and the discharge voltage-capacity characteristics and the charge voltage-capacity characteristics vary greatly. Since the magnitude of the charge polarization depends on the past charge / discharge history, after all,
The battery voltage is greatly affected by not only current but also past charge / discharge history (past charge / discharge current or change in charge / discharge power).

In response to this problem, the present inventors have obtained the following findings as a result of numerous experiments. In the charging / discharging state of the reference current or the reference power (that is, the charging / discharging state in which the influence of the fluctuation of the battery voltage drop due to the current fluctuation can be neglected), the variation in the capacity with respect to the reference state battery voltage (battery voltage) is determined as described later. Can be converged to a range.

In order to realize the convergence of the variation in the capacity, the capacity-voltage characteristic (minimum voltage characteristic line at the time of discharge) at the time of discharging from a substantially fully charged state (here, a capacity state of 95% or more) is obtained. The normal minimum capacity value P and a predetermined normal maximum capacity value on a capacity-voltage characteristic (maximum voltage characteristic line during charging) when charging the battery from a substantially completely discharged state (here, a state of less than 5%). Charge and discharge may be performed with the Q. As specific control, for example, voltage control for maintaining the reference state battery voltage between the normal maximum voltage value Vq and the normal minimum voltage value Vp individually corresponding to P and Q is performed. The start of the charge / discharge history is performed from the above-mentioned substantially fully charged state or the above-mentioned substantially completely discharged state.

In this manner, the capacity can be maintained between the normal minimum capacity value P and the normal maximum capacity value Q regardless of the repetition of the change of the charge / discharge state. This is because, even in a large hysteresis battery, the reference state battery voltage and its corresponding capacity are coordinate points determined by the normal minimum capacity value P and the normal minimum voltage value Vp corresponding thereto on the discharge minimum voltage characteristic line, This is based on the finding that the normal maximum capacity value Q and a coordinate point determined by the maximum normal voltage value Vq corresponding to the maximum voltage characteristic line at the time of charging are present in a crescent-shaped region having both ends.

According to the first aspect of the present invention, when the reference state battery voltage drops below the normal minimum voltage value Vp, the battery is charged to near the normal maximum voltage value Vq and then to the target voltage value Vc. Perform the operation to discharge. In this way, the reference state battery voltage corresponding to the target voltage value Vc and the actual capacity value actually corresponding to the target voltage point with respect to the target coordinate point defined by the target voltage value Vc and the corresponding target capacity value are set. Capacitance deviation between them can be reduced favorably.

According to a second aspect of the present invention, there is provided the above-described first aspect.
Only the invention of the present invention differs from the recovery process from the overcharge. In other words, after the reference state battery voltage falls below the normal minimum voltage value Vp, when a predetermined condition is satisfied, full charge (capacity of 95% or more), preferably equal charge is performed, and then discharge is performed. By changing the battery capacity to the normal minimum voltage value Vp
Then, the battery is charged to a predetermined amount that does not reach the maximum normal capacity value Q from the minimum normal capacity value P, and the battery capacity is reduced to a normal capacity range between the maximum normal capacity value Q and the minimum normal capacity value P. Put in.

That is, in this embodiment, the battery is fully charged at a suitable time after deviating from the normal range, and the operating point (coordinate point) on the reference voltage-capacity plane of the battery is again set to the minimum voltage at the time of discharging. Since it is possible to return to the normal minimum capacitance value P on the characteristic line, it is possible to eliminate the displacement of the capacitance by subsequently operating in the voltage range corresponding to this capacitance range PQ.

According to a third aspect of the present invention, in the battery control method for a power generation type electric vehicle according to the second aspect, the full charge is performed by a uniform charge (after a predetermined reference state battery voltage is reached and a small current value is reached). The charging operation is performed until the battery is fully charged by charging for a predetermined time. Therefore, the operating point is accurately returned to the point P on the minimum voltage characteristic line by the subsequent discharge, and is accurately returned to the target point by the subsequent charging. be able to.

According to the third aspect of the present invention, when the battery voltage is over-discharged by exceeding the normal minimum voltage value by a predetermined amount, the battery is over-charged from the normal maximum voltage value Vq to a range not exceeding the predetermined amount. , An operation of discharging to the target voltage value Vc is performed. By doing so, the capacity when the reference state battery voltage matches the target voltage value Vc can be satisfactorily returned to the target capacity value corresponding to the target voltage value Vc.

According to a fifth aspect of the present invention, in the battery control method for a power generation type electric vehicle according to any one of the first to fourth aspects, the battery is a nickel-metal hydride battery. With this configuration, a nickel-metal hydride battery having a large hysteresis characteristic can be accurately operated in a predetermined normal capacity range.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the following examples. In addition, as the power generation type electric vehicle, in addition to the above-described hybrid vehicle, there is a fuel cell vehicle having a fuel cell and a battery that absorbs imbalance between the generated power and the required power of the load.

[0024]

FIG. 1 shows an example of the configuration of a parallel hybrid vehicle using the battery control method of the present invention. Reference numeral 11 denotes an engine, 12 denotes an AC-type generator that generates power by part of the driving force of the engine 11, 13 denotes an inverter that converts AC power output from the generator 12 into DC power, and 14 denotes a nickel-metal hydride battery. It is a battery device including an assembled battery (also simply referred to as a battery). The output of the engine 11 is transmitted to wheels 18 via a torque distributor 15 and a gear 17. The inverter 13 drives the motor 16 by being supplied with power from the generator 12 and the battery 14, or charges the battery 14 with electric power regenerated by the motor 16.

FIG. 2 is a block diagram showing the battery 14 of the hybrid vehicle shown in FIG. In the battery 14, 2
1 is a battery pack, 22 is a number of battery modules that are connected in series to each other to form the battery pack 22, 23 is a temperature sensor, 24 is a detection circuit for detecting the voltage of each battery module 22, 25 is a temperature detection circuit, and 26 is Current detection circuit, 2
Reference numeral 7 denotes a battery control microcomputer (also referred to as a battery controller) for detecting the capacity of the battery 14 based on signals from the voltage detection circuit 24, the temperature detection circuit 25, and the current detection circuit 26. Reference numeral 28 denotes a vehicle controller that actually controls charging / discharging of the battery pack 21 based on an SOC signal or the like from the battery 14. The vehicle controller 28 performs control based on input information from the battery control microcomputer 27 and various parts of the vehicle.
The engine 11, the generator 12, and the inverter 16 are controlled.

FIG. 3 shows the voltage-current characteristics of the nickel-metal hydride battery (single cell) used in this embodiment during actual running of the vehicle.
In FIG. 3, a characteristic line L is a predetermined constant power (voltage × current = constant) curve. In this embodiment, the maximum discharge power value of the battery pack 21 in this hybrid vehicle system is converted into one battery cell. It is shown.

In FIG. 3, a broken line 31 shows current and voltage characteristics when the battery capacity is in a fully charged state, and a broken line 32 shows that the battery voltage has the minimum operation when the battery capacity is discharged at the maximum discharge power value. The current and voltage characteristics when the value reaches the voltage V_min are shown. As described above, the current and voltage characteristics are high near the full charge, as shown by a characteristic 31, and decrease as the battery capacity decreases, as shown by a characteristic 32.

Here, in the characteristic 31, the coordinate point of the current = 0 A is the point of the capacitance P_max 'and the voltage V_max', and the characteristic 3
2, the coordinate point of the current = 0 A is the capacitance P_min ′ and the voltage V
_Min '. In this manner, the current and voltage characteristics during running are measured, and a predetermined constant current value (for example, current = 0) is measured.
By converting the voltage value to A) and using this as the reference state battery voltage, and using these capacity values and the reference state battery voltage value, it is possible to eliminate the effect of the voltage fluctuation due to the current change.

Alternatively, current and voltage characteristics 31 near full charge
, The point at the time of predetermined constant power discharge (here, at the time of the maximum discharge power value) is P_max and the voltage V_max. In the characteristic 32, the point at the time of constant power discharge is P_min and the voltage V_min.
Is the point. In this way, the current and voltage characteristics during traveling are measured, the voltage value is converted to a predetermined constant power value, and this is used as the reference state battery voltage. Is used, it is possible to remove the influence of the voltage fluctuation due to the power change.

In this manner, the relationship between the reference state battery voltage and the capacity at a predetermined constant power (or constant current) can be obtained. FIG. 4 shows the relationship between the battery voltage and the capacity in the reference state at the time of constant power discharge (here, at the time of the maximum discharge power value).
FIG. 5 shows the relationship between the reference state battery voltage (open-circuit voltage) and the capacity when the current is 0 A as an example at the time of constant current. Since both are almost the same, the case of FIG. 4 will be described below.

In FIG. 4, reference numeral 41 denotes a voltage characteristic (minimum voltage characteristic line at the time of discharge) measured when the SOC tends to discharge from a state of 100% SOC, and 42 denotes a voltage measured when the battery tends to charge from a state close to complete discharge. Characteristics (maximum voltage characteristic line during charging). The characteristics of 41 and 42 are greatly different,
It can be seen that large hysteresis occurs in the characteristics of the discharge tendency and the charge tendency.

Reference numeral 43 denotes coordinates P_Hi of the SOC 80%.
Coordinate P_L of SOC 40% from (common maximum capacity value Q) point
A voltage characteristic line 44 when the battery is discharged to the point o (normal minimum capacity value P). Reference numeral 44 denotes an SOC8 from the point P_Lo of the SOC 40%.
It is a voltage characteristic line at the time of charging to the point P_Hi of 0% of coordinates. It can be seen that the hysteresis surrounded by the characteristics of the voltage characteristic lines 43 and 44 is much smaller than the hysteresis surrounded by the voltage characteristic lines 41 and 42. The voltage at the point P_Hi is V_Hi (maximum voltage Vq), and the voltage at the point P_Lo is V_Lo (minimum voltage Vp).

To explain further, the coordinates P_ of the 80% SOC
The Hi point can be regarded as a point of 80% SOC on the maximum charging voltage characteristic line 42 showing the capacity-voltage characteristic at the time of charging from a substantially completely discharged state. Or to V_Hi). Similarly, the point P_Lo of the SOC 40% is indicated by the SOC4 on the discharge minimum voltage characteristic line 43 indicating the capacity-voltage characteristic at the time of discharging from a substantially full charge state.
It can be roughly regarded as a point of 0%, and can therefore be reached by discharging from a substantially fully charged state to SOC 40% (or to V_Lo).

In FIG. 4, reference numeral 43 denotes a reference state line when the battery is discharged from the point P_Hi (ordinary minimum voltage characteristic line), and reference numeral 44 denotes a reference when the battery is charged and discharged from the point P_Lo. It is a line (normal maximum voltage characteristic line) showing a change in state battery voltage. Therefore, once the point P_Hi or the point P_Lo is reached, the capacity 40
８０80% or equivalent reference state battery voltage V_H
When charging / discharging the battery between i or V_Lo (hereinafter also referred to as standard charging / discharging), it can be seen that the relationship between the reference battery voltage and the capacity of the battery is within the diagonal lines in FIG.

Next, as the target voltage value Vc or the reference voltage value in the present invention, a capacity of 60%, a reference state battery voltage (also simply referred to as a battery voltage) is set as a substantially center point of the hatched area.
Set the VM points. Therefore, if the standard charge / discharge is performed, the fact that the battery voltage is VM means that the battery voltage is VM and the normal minimum voltage characteristic line 43 regardless of the past charge / discharge history.
It can be understood that the fluctuation range of the capacitance can be limited to 10% from the capacitance value of about 55% at the intersection with the maximum voltage characteristic line 44 to about 65% of the capacitance value at the intersection with VM.

The same applies to FIG. 5. If VM ′ corresponding to the above-mentioned VM is appropriately selected, if the voltage at the time of the current = 0 A is VM ′, the capacity fluctuation width regardless of the past charging / discharging history. From about 55% to about 65%. Next, FIG. 6 shows the results of further detailed examination of the charge / discharge characteristics (reference state battery voltage-capacity characteristics) in the characteristic lines 43 and 44 in FIG.

Reference numeral 61 denotes a characteristic line for charging from a predetermined point P1 to P2 on the ordinary minimum voltage characteristic line 43 when discharging from the point P_Hi, and 62 denotes a characteristic line for discharging from P2 to P3. . From FIG. 6, the characteristic line 61 when the capacity changes due to the charging tendency from the coordinate P1 is indicated by the coordinate P_Hi
Converge to a point. Furthermore, it can be seen that when charging from an arbitrary point on the characteristic line 43, it converges to the point P_Hi. On the other hand, it is understood that the characteristic line 62 when the capacity changes due to the discharge tendency from the coordinate P2 converges to the coordinate P1.

That is, the discharge from a predetermined point in the service area surrounded by the characteristic lines 43 and 44 is directed toward the characteristic line 43 if the charging start point in the previous charging up to the predetermined point is on the characteristic line 43. I understand. Similarly, characteristic lines 43 and 4
It can be seen that the charging from a predetermined point in the common area surrounded by 4 is directed to the characteristic line 44 if the discharge starting point in the previous discharging to the predetermined point is on the characteristic line 44.

That is, it is understood that, in this ordinary area, if the battery is once discharged or charged from a certain state and then is returned to the original value based on the SOC, the voltage also returns to the original value.
This is a feature common to all rechargeable secondary batteries, not limited to nickel-metal hydride batteries, and is called a polarization phenomenon. Here, the capacitance value at the time of the voltage VM on the characteristic line 43 is represented by SOC1,
The capacitance value at the time of the voltage VM on the characteristic line 44 is set to SOC2.
The voltage VM is determined as the target voltage value Vc such that the SOC1 and the SOC2 become equal to plus or minus around the capacity of 60%.

In this state, it is assumed that the vehicle has started traveling from the point P_Hi. The battery voltage at the time of constant power discharge (reference state battery voltage) during driving of the hybrid vehicle is V
When the generator 12 is controlled to be at M, the point P_Hi changes on the characteristic 43, and the SOC changes from 80% to SOC1 at which the characteristic 43 intersects the voltage VM. Understand.

Thereafter, when the driver runs in a manner that consumes the battery capacity and reaches, for example, the SOC at the coordinate P1, the voltage is restored to the voltage VM on the characteristic line 61 this time. Is stable at 60%. That is, the variation range of the capacity is limited to SOC 80% to 40% (or the battery voltage is limited to V_Hi to V_Lo),
By reducing the hysteresis of the battery characteristics, the SOC is maintained at least in the range from SOC1 to SOC2.
Further, when charge and discharge are repeated, the capacity gradually increases to the target voltage value V
It converges to the target capacity value (SOC 60%) corresponding to c (VM).

A lead battery or the like having a small hysteresis characteristic can maintain a target capacity without limiting the range of use of the battery capacity. Also, the voltage V
By setting M to the capacity to maintain the battery capacity, the capacity to be maintained can be changed to an arbitrary capacity instead of 60% of the present embodiment. (Example 1 of Recovery Processing from Overdischarge) Next, in FIG. 6, a case where the power source deviates from the crescent-shaped normal range surrounded by the normal minimum voltage characteristic line 43 and the normal maximum voltage characteristic line 44 to the discharge side is referred to FIG. I will explain.

Now, the operating point (coordinate) is SOC1 (80
%) And SOC2 (40%), and the coordinates Q (P_P
Hi) A discharge characteristic line 45 connecting a point, a target point (a target capacity value (60%), a target voltage value Vc (1.1 V)), and a coordinate point P ′.
Let it be above. In this state, it is assumed that the discharge has progressed to the point B in response to the request from the vehicle, and then the battery can be charged due to a decrease in the vehicle running load. Then, the battery moves from point B to B '
It returns along the charging characteristic line 46 that passes through the point to the point Q (strictly speaking, the value is slightly smaller than the point Q but can be regarded as the point Q). Therefore, thereafter, by discharging substantially from the point Q, it is possible to return to the target point C 'again.

That is, when the battery is overdischarged from the normal range, simply charging up to the target voltage value Vc results in the capacity being at the point B ', which is insufficient. Therefore, in this embodiment, when the over-discharge occurs beyond the normal range, the target voltage value Vc
In addition to charging up to the normal maximum capacity value Q (or its corresponding maximum normal voltage value Vq), the battery is discharged to the target voltage value Vc. This makes it possible to satisfactorily return the operating point when the reference state battery voltage V reaches the target voltage value Vc to the vicinity of the target point C ′.

An example of a specific charge / discharge control including the above-described recovery process 1 from overdischarge will be described below. First, a reference state battery voltage at constant power (or a reference state battery voltage at constant current) is calculated from a pair of the detected voltage data and current data. The voltage data is preferably detected for each cell. However, when detecting the voltage of a plurality of cells connected in series, the voltage is corrected to a value per cell.

Next, after the operating point is set on the characteristic line 43 or 44 by the above-described method (discharge from the fully charged state or charging from the completely discharged state), the battery voltage is changed from V_Hi to V_L.
The charge / discharge is controlled so as not to deviate from the range of o. Specifically, charging is prohibited when the battery voltage reaches V_Hi,
When the battery voltage reaches V_Lo, discharging is prohibited. Separately, a temporary SOC is calculated by current integration.
Next, the SOC is corrected based on the comparison result.

The SOC correction will be described in more detail. When the capacity obtained by current integration has reached the target capacity value of 60%, the difference between the reference state battery voltage and VM as the target voltage value Vc is obtained. Is charged or discharged as compensation charge / discharge until the value becomes zero. Since this difference can be regarded as a current integration error, it is not accumulated in the value of the current integration capacity.

[0048] Then, until the capacity obtained by the current integration reaches the target capacity value of 60%, the following procedure is performed.
The capacity is estimated using the current integrated capacity without any integration error, and based on the difference between the current integrated capacity and the target capacity value, the capacity is converged to the target capacity value by performing charge / discharge control to eliminate the difference. Can be done. In addition, instead of controlling the charge / discharge so that the battery voltage does not deviate from the range of V_Hi to V_Lo, the integrated current capacity becomes P_Hi.
Charge / discharge control may be performed so as not to deviate from the range of P_Lo.

(Example 2 of Recovery Processing from Overdischarge) When the above-described (Example 1 of recovery processing from overdischarge) is performed, the target voltage value Vc can be returned to, for example, the point C '. However, when the battery is thereafter operated while converging to the target voltage value Vc between the normal maximum voltage value Vq and the normal minimum voltage value Vp, the operating points of the battery are Q, O, P,
From the range before connecting O ', Q, Q, C', P ',
Shift to within the range connecting B and Q. That is, the capacity range when the reference state battery voltage V matches the target voltage value Vc shifts from O to O 'to C' to B.

Therefore, in the present embodiment, in order to eliminate this shift, a time period in which the vehicle state permits it is detected, and during this time period, the battery is automatically or periodically charged uniformly. The state battery voltage V is returned to the point P (the normal minimum voltage value Vp), and then returned to the target voltage value Vc by charging. Thereby, the shift can be eliminated. In particular, in this embodiment, only when the vehicle deviates from the normal range to the discharging side, the vehicle is charged evenly thereafter when the vehicle conditions permit, so that there is an advantage that no trouble occurs in running the vehicle. It should be noted that the equivalent charge may be simplified to a simple full charge / discharge process, or the full charge process may be normally performed, and the equal charge process may be sometimes performed.

(Example 3 of Recovery Processing from Overdischarge) The disadvantage of the above (Example 1 of recovery processing from overdischarge) is that since the coordinate P shifts to the coordinate P ′, the normal minimum voltage characteristic line becomes 43 to 45. In addition, the normal maximum voltage characteristic line shifts from 44 to 47, and as a result, the capacitance width at the target voltage value Vc shifts to a lower capacitance side. Although the above-mentioned (Example 2 of over-discharge recovery processing) can be implemented and eliminated, the shift can be reduced or eliminated by the following method for convenience.

In FIG. 7, it is clear that the discharge-side shift is caused by an excessive discharge exceeding the normal range. Therefore, in this embodiment, for example, when the charge is returned from the point B, a point smaller than the excess discharge amount (the difference between the capacity B (20%) and the normal minimum capacity value P (40%)) from the normal range. Maximum capacity Q for regular use only for a fixed amount (excess charge)
Overcharge more. In this manner, the influence of the operating point left shift caused by the immediately preceding excess discharge can be canceled to some extent by the effect of the operating point right shift caused by the immediately following excess charge.

Accordingly, this makes it possible to satisfactorily return the operating point to the position before the overdischarge, thereby making it possible to make the capacitance variation at the target voltage value Vc close to the range between O and O '. (Example 4 of recovery process from over-discharge) Further, in the above-mentioned (example 3 of recovery process from over-discharge), S
From the operating point exceeding OC1, excess discharge is again performed to become less than SOC2. However, the amount of excess discharge (the difference between the capacity value reached by the overdischarge and SOC2) is made smaller than the amount of excess charge immediately before (the difference between the capacity value reached by the overcharge and the SOC1). By doing so, the operating point can be returned to the position before the overdischarge more satisfactorily, and the capacity variation at the target voltage value Vc can be made closer to the range between O and O '.

Further, as one mode of this method, the temporary target SOC value can be alternately swung to both sides of the original target capacity value of 60% and gradually approach the target capacity value. The above-mentioned method is the same as the AC demagnetization for eliminating the residual magnetization of the magnetic film having the magnetic hysteresis. The charging operation and the discharging operation up to the predetermined capacity in each of the above-described recovery processing examples can be performed based on the corresponding reference state battery voltage, but can also be performed based on the current integrated capacity.

Next, a more specific control operation of the above-described charge / discharge control example will be described below with reference to a flowchart.
First, the charge / discharge control of the vehicle controller 28 will be briefly described with reference to FIG. The vehicle controller 28 controls the output of the engine 11 so that the total value of the vehicle load calculated based on the traveling state and the operation state and the SOC signal (signal indicating the current capacity of the battery) received from the battery controller 27 matches the output of the engine 11. Then, control is performed to instruct a motor controller (not shown) that controls the engine 11. Since the control itself in the hybrid vehicle is not the gist of this embodiment, further description is omitted.

FIG. 8 shows a specific control of the portion related to the charge / discharge control of the battery 14 by the vehicle controller 28.
In step 1000, the SOC is
In step 1002, a difference between the read SOC and a target SOC to be targeted is obtained in advance, and the difference is set as a required battery power value.

In step 1004, the calculated load required power value is added to the previously calculated traveling load power to obtain a total load power, and the required engine output value is made to match this total load power. Further, the vehicle controller 28 calculates the difference between the engine output and the traveling load power, and performs control for driving the generator 12 or the motor 16 by the difference. However, this control is not the gist of this embodiment. Is omitted.

Next, the SO in the battery controller 27 is
The C determination operation will be described below with reference to FIG. Note that in the past, the operating point was previously set on the characteristic line 43 or 44 by the above-described method, and then the battery voltage was changed to V_H.
By controlling the charge and discharge so as not to deviate from the range of i to V_Lo, it is assumed to be between the characteristic lines 43 and 44.

In FIG. 9, first, in step 901, the voltage VB, the current IB, and the temperature TB during running are detected, and the internal resistance Rk is calculated by the least square method based on a plurality of pairs of the voltage VB and the current IB. , A voltage at the time of predetermined power discharge (reference state battery voltage) VBw is calculated as a reference state battery voltage (step 902). VB0 = VB + Rk × IB VBw = {VB0 + (VB0 2 -4 × Rk × α) 0.5}
× 0.5 where α is the constant power used (21 kW in this case).

Next, the SOC calculated by the current integration method in step 903 and the SOC calculated in step 904
Is smaller than the normal minimum capacity value P of 40% (also referred to as an overdischarge state), or is currently being recovered from the past overdischarge state (in this embodiment, a flag F1 or F2, At least one of them is 1), and if not, step 907
And if so, to step 906. The capacity may be estimated based on a map stored in advance based on the reference state battery voltage VBw instead of the current integration method.

This does not cause a significant problem even if the estimated capacity varies as long as the estimated capacity does not exceed the ordinary minimum capacity value P. In addition, at the time of excessive discharge in which the estimated capacity decreases beyond the ordinary minimum capacity value P, the reference state is not changed. This is because the variation in capacity with respect to the battery voltage VBw is significantly reduced, so that at least excess discharge can be practically and accurately detected by the reference state battery voltage VBw regardless of the past charge / discharge history. Further, as can be seen from FIG. 7, when the battery is discharged beyond the normal minimum capacity value P, there is an advantage that the change in the reference state battery voltage VBw with respect to the capacity change is large and the sensitivity is good.

In step 906, a process for recovering from the above excessive discharge state is performed. An example of this recovery processing will be described below with reference to FIG. First, in step 9060,
Check whether the flag F1 is 0 or not. This flag F1 is 1
Means that the battery is over-discharged (for example, B in FIG. 7).
This is a flag indicating that charging is being performed from the point (point) to the substantially point Q following the charging characteristic line 46.

If the flag F1 is 1, step 9063
If it is 0, the process proceeds to step 9061 to shift the target capacity value to 80%. At the next step 9062, the flag F1 is set to 1. Next, step 9063
In step 903, it is checked whether or not the SOC calculated in step 903 has reached the normal maximum capacity value Q of 80%. If the SOC has not reached 80%, the process proceeds to step 907. Step 90
At step 64, the flag F1 is reset to 0.

Next, it is checked whether or not the flag F2 is 0 (step 9065). The fact that the flag F2 is 1 means that C 'is traced from the substantially point Q on the discharge characteristic line 45.
It means that discharging is in progress until the point is reached. If the flag F2 is 1, the process proceeds to step 9068. If the flag F2 is 0, the target SOC (target capacity value) is returned to 60% (step 9066), the flag F2 is set to 1 (step 9067), and the process proceeds to step 9068. .

In step 9068, it is determined whether or not the SOC calculated in step 903 has reached 60% due to the discharge. If not, the process proceeds to step 907. If the SOC has reached, the flag F2 is reset to 0 and the process proceeds to step 903. . In the above embodiment, the operating point is determined based on the capacity value integrated in step 903. However, it is needless to say that the operating point may be determined based on the reference state battery voltage. For example, whether or not the approximate point Q has been reached is determined by the reference state battery voltage VBw.
And Vq, and whether or not the point C 'has been reached can be determined by a match between the reference state battery voltage VBw and VM.

With this control, the operating point can be shifted from the point B in FIG. 7 to the point C 'by substantially following the point Q. On the other hand, from the point B, simply the target voltage value Vc = VM
When the reference state battery voltage is controlled between Vp and Vq, the actual capacity variation when the reference state battery voltage is the target voltage value Vc = VM is C ′. ~ B '.

In step 907, the calculated SO
C and the target SOC are actually output to the vehicle controller 28 that controls the generator 12 and the like. In step 908, it is monitored whether or not the SOC is between the upper limit of 80% and the lower limit of 40%. This subroutine will be described below with reference to FIGS. In FIG. 11, step 1001
Then, the case where the obtained SOC exceeds 80% is determined, and in step 1002, a charge restriction command for prohibiting further charge is output to the controller 12. When the processing of steps 9061 to 9063 is performed (F1
This is not the case in the case of = 1). In step 1003, it is determined whether or not the obtained SOC falls below 40%, and in step 1004, a recovery processing command for performing recovery processing is output to the controller 12.

As another method, as shown in FIG. 12, the upper limit and the lower limit of the SOC may be monitored based on the reference state battery voltage. More specifically, when the reference state battery voltage VBw at the time of constant power discharge exceeds V_Hi corresponding to a voltage of 80% SOC in step 1101, a charge limit command is output in step 1102 to prevent further charge. Note that this is not the case when the processing of steps 9061 to 9063 is performed (F1 = 1).
In step 1103, the reference state battery voltage V at the time of constant power discharge
When Bw falls below V_Lo corresponding to the voltage of the SOC of 40%, a recovery processing command for performing the recovery processing is output to the controller 12 in step 1104. In addition,
In this case, besides detecting the upper and lower limits based on the reference state battery voltage VBo at the time of constant power discharge, the upper and lower limits may be detected based on the reference state battery voltage (for example, the voltage at the time of current = 0 A) VBo during the constant current discharge. .

In step 909, it is checked whether or not the traveling has been completed. When the traveling is completed, in step 910, the result of the calculation is stored in a memory or the like (not shown) so as to be used as an initial value at the start of the next traveling. I do. Note that, in the above-described recovery processing, as described above, the variation range of the SOC when the reference state battery voltage VBw or the target voltage value Vc matches does not strictly recover to the initial state. Therefore, in this embodiment, after the occurrence of excessive discharge, equal charging (or full charging) is performed under predetermined conditions. The equal charging start condition may be a manual start by the driver, or may be determined automatically by determining a running state.

The recovery process by this equal charging will be described below with reference to FIG. First, in step 2000, uniform charging is started. In this embodiment, the equalizing charge refers to a charging operation in which the charging is continued for a predetermined period of time with a small current after charging to near the full charge voltage Vq, and it is checked in step 2002 whether or not the equalizing charge has been completed. When the equal charge is completed,
The battery is discharged until the reference state battery voltage VBw reaches the normal minimum voltage value Vp or the current integrated capacity becomes 100% to 40% (step 2004), and then the reference state battery voltage VBw reaches the normal minimum voltage value Vp. Or until the integrated current capacity becomes 40% to 60% (step 2).
006), and terminate the routine.

(Modification) Step 906 in FIG.
Another embodiment will be described below. First, the premised technical idea will be described with reference to FIG. For example, let us consider a case where the battery is excessively discharged to the point B and then charged to a predetermined capacity value exceeding the point Q, for example, the point P '. If the discharge characteristic line (for example, 48) discharging from this capacity value P 'passes through point O, as long as charging and discharging between SOC1 and SOC2 are repeated, the reference state battery voltage VBw is equal to the target voltage value Vc =
It can be seen that the upper limit of the variation of the capacitance value is at the point O in the state where it matches the VM, and the variation of the capacitance shifts to the left from C ′ to B. However, if the excess charge performed after the occurrence of the excess discharge exceeding the point P is larger than the previous excess discharge, the influence field of the subsequent excess charge becomes large.

As described above, the characteristics in the case of overdischarge beyond the point P are close to the minimum voltage characteristic line 41. Therefore, the amount of excess discharge in advance (based on the capacity at point P of 40%)
Alternatively, a suitable excess charge amount (based on a capacity of 80% at point P) or the highest voltage to be reached is stored in a map in advance corresponding to the reached lowest voltage.

More specifically, with reference to the flowchart shown in FIG. 14, in step 3000, the excess discharge amount (capacity at point P of 40%
7, a suitable excess charge amount (based on a capacity of 80% at point P) or reached corresponding to the lowest voltage reached (reference state battery voltage VBw at point B in FIG. 7) or reached. The highest voltage to be read is read, and overcharging is performed from point B to point P ′.

In the next step 3000, discharging is performed from the above-mentioned excess charge amount (based on the capacity of point P of 80%) or the operating point (here, point P ') determined by the highest voltage to be reached to point O, and thereafter, The control may be performed so that the reference state battery voltage VBw becomes the target voltage value Vc = VM = 1.1V. Alternatively, the capacity is controlled to 60% by the current integration method.

In this way, it is possible to more easily return the operating point. Further, according to this modified embodiment, a method of further canceling this excess discharge by excess charge is developed, and thereafter, while alternately charging and discharging a predetermined amount from the target capacity value to a capacity value separated to the charge side or the discharge side. It is also possible to perform an operation approaching the target capacity value.

In this manner, as in the case where the remanent magnetization of the ferromagnetic material having the magnetic hysteresis characteristic is AC demagnetized by the AC magnetic field whose amplitude is gradually reduced, the battery having the charge / discharge hysteresis due to the remaining polarization also has the reference state. The capacity when the battery voltage matches the target voltage value Vc is
It is possible to satisfactorily return to the target capacitance value corresponding to this target voltage value Vc.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a parallel hybrid vehicle using a battery control method of the present invention.

FIG. 2 is a block diagram showing an electric system of the hybrid vehicle shown in FIG.

FIG. 3 is a diagram showing voltage-current characteristics of a nickel-metal hydride battery (single cell) used in this example during actual running of the vehicle.

FIG. 4 is a diagram showing a voltage-capacity characteristic in a constant power state created based on FIG. 3;

FIG. 5 is a diagram showing voltage-capacity characteristics in a constant current state created based on FIG. 3;

6 is a diagram showing a voltage-capacity characteristic in a constant power state showing a charge / discharge trajectory in FIG.

FIG. 7 is a diagram showing voltage-capacity characteristics in a constant power state showing an overdischarge and a subsequent recovery charge trajectory in FIG. 4;

FIG. 8 is a flowchart illustrating a battery control method according to this embodiment.

FIG. 9 is a flowchart showing a battery control method according to this embodiment.

FIG. 10 is a flowchart illustrating a battery control method according to this embodiment.

FIG. 11 is a flowchart illustrating a battery control method according to this embodiment.

FIG. 12 is a flowchart illustrating a battery control method according to this embodiment.

FIG. 13 is a flowchart illustrating a battery control method according to this embodiment.

FIG. 14 is a flowchart illustrating a battery control method according to this embodiment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01R 31/36 H02J 7/34 D H02J 7/00 B60K 9/00 Z 7/34 (72) Inventor Yamashita Takashi 1-1-1 Showa-cho, Kariya-shi, Aichi Pref. Denso Corporation (72) Inventor Toshiyuki Kawai 14 Iwatani, Shimoba-Kakucho, Nishio-shi, Aichi F-term in Japan Auto Parts Research Institute Co., Ltd. 2G016 CA03 CB12 CB13 CB21 CB31 CC01 CC04 CC27 3G093 AA07 AA16 BA14 DB00 DB09 DB19 DB20 EB00 FA07 FA10 FA11 FB05 FB06 5G003 AA07 BA01 CA01 CA11 CB01 DA07 DA12 DA18 FA06 GB06 GC05 5H115 PG04 PI16 PI18 PI24 PI29 PU01 PU26 QN02 TI06 TI06 TI06 TI06 TI06 TI06

Claims (5)

[Claims] 1. A battery control method for an electric vehicle, comprising: a power generating means; and a battery for storing power generated by the power generating means and supplying power to a traveling motor. Calculating a reference state battery voltage, which is a battery voltage at a predetermined reference current value or a predetermined reference power value, based on a discharge-time minimum voltage characteristic line indicating a capacity-voltage characteristic when the battery is discharged from a substantially full charge state. Setting a predetermined normal minimum capacity value P; setting a predetermined normal maximum capacity value Q on a charging maximum voltage characteristic line indicating a capacity-voltage characteristic when charging the battery from a substantially completely discharged state; A predetermined amount of discharge from the capacity value Q that does not reach the working minimum capacity value P or a predetermined amount of charging from the working minimum capacity value P that does not reach the working maximum capacity value Q is performed to reduce the capacity of the battery. A normal capacity range between the normal maximum capacity value Q and the normal minimum capacity value P, and the reference state battery voltage is a normal maximum voltage value individually corresponding to the normal minimum capacity value P and the normal maximum capacity value Q. Charge / discharge control is performed so as to converge to a predetermined target voltage value Vc between Vq and the normal minimum voltage value Vp, and when the reference state battery voltage falls below the normal minimum voltage value Vp, A battery control method for a power-generating electric vehicle, comprising performing an operation of charging to a voltage value of about Vq and then discharging to a voltage of about the target voltage value Vc. 2. A battery control method for an electric vehicle, comprising: a power generating means; and a battery that stores power generated by the power generating means and supplies power to a traveling motor. Calculating a reference state battery voltage, which is a battery voltage at a predetermined reference current value or a predetermined reference power value, based on a discharge-time minimum voltage characteristic line indicating a capacity-voltage characteristic when the battery is discharged from a substantially full charge state. Setting a predetermined normal minimum capacity value P; setting a predetermined normal maximum capacity value Q on a charging maximum voltage characteristic line indicating a capacity-voltage characteristic when charging the battery from a substantially completely discharged state; A predetermined amount of discharge from the capacity value Q that does not reach the working minimum capacity value P or a predetermined amount of charging from the working minimum capacity value P that does not reach the working maximum capacity value Q is performed to reduce the capacity of the battery. A normal capacity range between the normal maximum capacity value Q and the normal minimum capacity value P, and the reference state battery voltage is a normal maximum voltage value individually corresponding to the normal minimum capacity value P and the normal maximum capacity value Q. The charge / discharge control is performed so as to converge to a predetermined target voltage value Vc between Vq and the normal minimum voltage value Vp, and when the reference state battery voltage falls below the normal minimum voltage value Vp, The battery capacity is restored to a value close to the normal minimum voltage value Vp by performing full charge during the period, and then discharging, and thereafter the normal maximum capacity value Q from the normal minimum capacity value P is reached. A battery control method for a power-generating electric vehicle, characterized in that the battery is charged in a predetermined amount and the capacity of the battery is set in a normal capacity range between the normal maximum capacity value Q and the normal minimum capacity value P. 3. The battery control method for an electric vehicle according to claim 2, wherein the full charge is performed by equal charging. 4. A battery control method for an electric vehicle, comprising: a power generation means; and a battery for storing power generated by the power generation means and supplying power to a traveling motor. Calculating a reference state battery voltage, which is a battery voltage at a predetermined reference current value or a predetermined reference power value, based on a discharge-time minimum voltage characteristic line indicating a capacity-voltage characteristic when the battery is discharged from a substantially full charge state. Setting a predetermined normal minimum capacity value P; setting a predetermined normal maximum capacity value Q on a charging maximum voltage characteristic line indicating a capacity-voltage characteristic when charging the battery from a substantially completely discharged state; A predetermined amount of discharge from the capacity value Q that does not reach the working minimum capacity value P or a predetermined amount of charging from the working minimum capacity value P that does not reach the working maximum capacity value Q is performed to reduce the capacity of the battery. A normal capacity range between the normal maximum capacity value Q and the normal minimum capacity value P, and the reference state battery voltage is a normal maximum voltage value individually corresponding to the normal minimum capacity value P and the normal maximum capacity value Q. Charge and discharge control is performed so as to converge to a predetermined target voltage value Vc between Vq and the normal minimum voltage value Vp, and when the reference state battery voltage decreases by a predetermined amount from the normal minimum voltage value Vp, Charging the reference state battery voltage within a range not exceeding the predetermined amount from the normal maximum voltage value Vq, and then discharging the battery voltage to the target voltage value Vc. . 5. The battery control method for a power-generating electric vehicle according to claim 1, wherein said battery is a nickel-metal hydride battery.