JP4433535B2 - Battery control method for power generation type electric vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery control method in a power generation type electric vehicle in which power generation means is mounted, such as a hybrid vehicle that combines an engine and an electric motor driven by a chargeable / dischargeable battery.
[0002]
[Prior art]
In recent years, HV (hybrid) vehicles equipped with an engine and a motor driven by a battery have been attracting attention for the purpose of improving fuel consumption. A battery mounted on an HV vehicle is mainly discharged from the battery during a high load operation such as acceleration, and is charged during a low load operation such as deceleration or traveling at a constant speed. In order to stably charge and discharge such a battery, it is necessary to balance SOC (State Of Charge / charged state) at a predetermined constant value, and therefore, SOC detection is an indispensable technology in battery control. Yes.
[0003]
As a method for detecting the SOC (or remaining capacity) of a battery, a method using charge / discharge current integration (hereinafter also referred to as a current integration method), a method for estimating SOC based on battery voltage (hereinafter referred to as a voltage estimation method). Is known).
[0004]
In view of the fact that the voltage change is small in the middle SOC region, Japanese Patent Application Laid-Open No. 10-51906 stores only the current / voltage map in the normal (allowable) upper limit value or the normal (allowable) lower limit value of the SOC for detection. If the measured current / voltage meets the conditions of this map, the SOC obtained by current integration is reset. Then, when the estimated SOC reaches the preset upper limit value of SOC, the battery is discharged. After that, when the estimated SOC reaches a preset SOC lower limit value, battery control is proposed in which a charge / discharge cycle for charging the battery is forcibly repeated.
[0005]
[Problems to be solved by the invention]
However, the current integration method is a method in which the charging / discharging current of the battery is sequentially detected, and this is infinitely accumulated (integrated) with the initial value of the SOC, so that the integration processing error gradually accumulates and accurate detection is performed. There was a problem that it was difficult to obtain values.
[0006]
Furthermore, in the above-mentioned conventional publication, SOC (capacity) detection is performed based on voltage / current data in the case of a high SOC value and a low SOC value that can be detected with relatively high accuracy because the slope of the voltage-capacitance characteristic is large. Based on the result, the battery state must be forcibly reciprocated between the high SOC value and the low SOC value. Therefore, if the battery state is forcibly shifted to the low SOC value side, the necessary power is obtained from the battery. When it is forcibly shifted to the high SOC value side, it becomes difficult to store the regenerative power in the battery, the usability of the battery is deteriorated, and the running function and fuel consumption are problematic.
[0007]
On the other hand, although the voltage estimation method does not have the above cumulative error, it has a large charge polarization effect, such as a nickel metal hydride alloy battery, and the relationship between the battery voltage and the SOC greatly changes depending on the charge / discharge history. In a battery (also referred to as a large hysteresis battery), even if 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, the charge / discharge history is different. Even if the current data is put in this map and the capacity is estimated, there is a problem that the expected accuracy cannot be obtained.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery control method for a power generation electric vehicle excellent in accuracy and usability.
[0009]
[Means for Solving the Problems]
According to the remaining capacity estimation method for a power generation type electric vehicle according to claim 1 for solving the above-mentioned problem, a predetermined reference current value or a predetermined reference power value is determined based on the measured voltage value and measured current value of the battery. The reference state battery voltage that is the battery voltage at is calculated, and charging / discharging of the battery is controlled such that the calculated reference state battery voltage becomes a predetermined target voltage value Vc.
[0010]
More specifically, a battery for an electric vehicle (battery for running power storage) has a use mode in which the charge / discharge current state or the charge / discharge power state changes every moment. On the other hand, the battery voltage varies depending on the magnitude of the current due to the influence of the internal resistance of the battery. Further, in a large hysteresis battery such as a nickel metal hydride battery, an electromotive voltage during discharge differs from an electromotive voltage during charging due to the influence of a charging polarization action or the like. Therefore, it is difficult to accurately estimate the capacity simply by introducing the measured battery voltage data into the battery voltage / capacity map. 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 data into this, but in this case, a three-dimensional map is stored. This must lead to an increase in memory scale.
[0011]
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 battery voltage data in a reference current state or a reference power state. Then, a predetermined target voltage value Vc corresponding to the normal capacity range in the reference current value or the reference power value is set.
[0012]
In this way, by charging and discharging so as to eliminate the difference between the reference state battery voltage and the target voltage value Vc without requiring a large-scale memory, the capacity of the battery can be reduced regardless of current fluctuations. It is always possible to keep the capacitance range corresponding to the target voltage value Vc.
[0013]
Claim 1 According to the configuration described , In the battery control method for a power generation type electric vehicle, a predetermined common minimum on a discharge minimum voltage characteristic line indicating a capacity-voltage characteristic which is a relation between a battery capacity when discharged from a substantially full charge state and a reference state battery voltage. A point on the maximum voltage characteristic line during charging indicating a capacity-voltage characteristic, which is a relationship between the capacity value when the battery is charged from a substantially fully discharged state and the reference state battery voltage, or a predetermined value from P When a predetermined normal maximum capacity value, which is a value obtained by charging only the capacity, is Q, the target maximum voltage value Vq and the normal minimum corresponding to the target minimum voltage value P and the normal maximum capacity value Q are individually set as the target voltage value Vc. The value is between the voltage values Vp, and charging / discharging is performed between the normal minimum capacity value P and the normal maximum capacity value Q.
[0014]
In this way, the fluctuation of the relationship between the battery voltage and the capacity due to the charge / discharge history is reduced, and the capacity is easily and accurately maintained within the range of PQ so as to avoid overcharge and overdischarge. be able to.
[0015]
This will be described in more detail.
[0016]
An electric vehicle battery (battery for running power storage) has a usage mode in which the charge / discharge current state or the charge / discharge power state changes every moment. On the other hand, in the case of a large hysteresis battery such as a nickel metal hydride battery, the battery voltage differs between the electromotive voltage during discharge and the electromotive voltage during charging due to the effects of charge polarization, etc. Fluctuates greatly. Since the magnitude of the charge polarization depends on the past charge / discharge history, the battery voltage is greatly influenced not only by the current but also by the past charge / discharge history (past charge / discharge current or charge / discharge power fluctuation record). The
[0017]
In response to this problem, the present inventors have obtained the following knowledge as a result of numerous experiments.
[0018]
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 battery voltage drop variation due to the current variation can be ignored), the capacity variation with respect to the reference state battery voltage (battery voltage) is predetermined as described later. Can converge to a range.
[0019]
In order to realize the convergence of the capacity variation, the normal minimum capacity on the capacity-voltage characteristic (minimum voltage characteristic line during discharge) at the time of discharging from a substantially fully charged state (here, the capacity state of 95% or more). A value P and a predetermined normal maximum capacity value Q on a capacity-voltage characteristic (maximum voltage characteristic line at the time of charging) from a substantially complete discharge state (referred to here as a capacity state of less than 5%) of the battery Charging / discharging may be performed in between. As specific control, for example, voltage control is performed in which the reference state battery voltage is held between the maximum common voltage value Vq and the minimum normal voltage value Vp corresponding to P and Q individually. The charge / discharge history is started from the substantially full charge state to the substantially complete discharge state.
[0020]
In this way, the capacity can be maintained between the normal minimum capacity value P and the normal maximum capacity value Q regardless of the repeated fluctuations in the charge / discharge state.
[0021]
This is because, even in a large hysteresis battery, the reference state battery voltage and the capacity corresponding thereto are the coordinate point 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 knowledge that a coordinate point determined by the normal maximum capacity value Q and the normal maximum voltage value Vq corresponding to the maximum voltage characteristic line at the time of charging exists in a crescent-shaped region having both ends.
[0022]
More preferably, the claims 2 As described, control is performed to converge the reference state battery voltage to a predetermined target voltage value Vc between the normal maximum voltage value Vq and the normal minimum voltage value Vp. In this way, the capacity can be held in a narrower region between the normal minimum capacity value P and the normal maximum capacity value Q, regardless of repeated fluctuations in the charge / discharge state.
[0023]
In particular, by setting the target voltage value Vc to a value in the vicinity of the median value between the normal maximum voltage value Vq and the normal minimum voltage value Vp (20% range above and below the median value), the reference state battery voltage is It is possible to maintain the capacity in a region in the vicinity of the median value between the normal minimum capacity value P and the normal maximum capacity value Q only by performing charge / discharge control for convergence to the target voltage value Vc.
[0024]
Claim 3 Claims according to the arrangement described 1 Or 2 In the power generation type electric vehicle battery control method described above, the capacity value convergence technique based on the reference state battery voltage is combined with the charge / discharge control technique based on the current integration capacity. Can be canceled.
[0025]
More specifically, when the current integrated capacity matches a predetermined reference capacity value, a predetermined reference voltage value (precisely, a predetermined standard state battery voltage value) corresponding to the reference capacity value and an actual reference The difference from the state battery voltage is calculated, this difference is regarded as a current integration error, and correction charge / discharge is performed to eliminate this difference. Naturally, since this difference is regarded as a current integration error, this correction charging / discharging does not perform current integration for calculating the current integration capacity.
[0026]
As a result, it is possible to cancel the current integration error with high accuracy and proceed to the next current integration capacity calculation.
[0027]
Claim 4 Claims according to the arrangement described 3 In the battery control method for the electric power generation electric vehicle described above, the reference voltage value is the target voltage value Vc, and the reference capacity value is in the vicinity of the median value between the normal minimum capacity value P and the normal maximum capacity value Q. A predetermined target capacity value is set. Then, charge / discharge control for converging the current integrated capacity to the target capacity value is performed.
[0028]
That is, charge / discharge control for converging the current accumulated capacity to the target capacity value is performed, and when the current accumulated capacity reaches the target capacity value, the correction charge for canceling the difference between the reference state battery voltage and the target voltage value Vc at that time is performed. Perform discharge control.
[0029]
In this way, the charge / discharge operation for correcting the current integration error is an operation for converging the capacity to the target capacity as it is.
[0030]
Claim 5 According to the described configuration, claims 1 to 4 In the battery control method for a power generation type electric vehicle described in any one of the above, the battery is a nickel metal hydride battery.
[0031]
In this way, a nickel metal hydride battery having a large hysteresis characteristic can be accurately operated within a predetermined normal capacity range.
[0032]
Claim 6 Claims according to the arrangement described 2 In the battery control method for the electric power generation type electric vehicle described above, the current integrated capacity, which is the capacity obtained by integrating the charge / discharge current to the initial capacity value, is calculated, and the measured voltage value of the measured battery and Based on the measured current value, a reference state battery voltage that is a battery voltage at a predetermined reference current value or a predetermined reference power value is calculated, and a value near the median value between the normal maximum capacity value Q and the normal minimum capacity value P is calculated. When a central coordinate point A defined by a predetermined target capacity value and target voltage value is set, and there is no memory effect on the two-dimensional plane of the reference state battery voltage and capacity, the normal maximum capacity value Q is used. A voltage characteristic line 43 for discharging to the minimum capacity value P is set, and when the operating point reaches the voltage characteristic line 43 or deviates to the low voltage side, the central return for returning the operating point to the central coordinate point A is performed. Process.
[0033]
In this way, the operating point reaches the voltage characteristic line 43 as described above as to whether or not a specific voltage drop phenomenon has occurred due to an increase in the memory effect or elimination of the charge polarization for some reason. Or when it deviates, the charge / discharge process, that is, the central return process here is performed, and the operating point is again set as the target capacity value and the target voltage value. It is possible to return to the vicinity of the central coordinate point A defined by
[0034]
Claim 7 Claims according to the arrangement described 6 In the battery control method for the power generation type electric vehicle described above, it is further determined whether or not the operating point has deviated by a predetermined voltage width or more from the voltage characteristic line 43 to a lower voltage side. Therefore, the memory effect is eliminated by deep discharge to a predetermined SOC value or less, and the central return processing is required thereafter. Therefore, the decrease in the reference state battery voltage is for eliminating the charge polarization or for increasing the memory effect. The operating point can be returned to the vicinity of the original central coordinate point A by deep discharge and subsequent central return processing of the operating point only when the memory drop increases.
[0035]
Claim 8 Claims according to the arrangement described 6 Or 7 Further, in the battery control method for the electric power generation type electric vehicle described above, the center return processing is performed between the voltage characteristic line 43 or the coordinate C of the minimum SOC when the voltage characteristic line 43 deviates to the lower voltage side and the target capacity value. Is calculated by multiplying the capacity difference X by the multiplication charge coefficient α (a value greater than 1 and less than 2), and then the multiplication charge capacity X ′ is calculated from the coordinates C. It consists of a process of charging only X ′ and then discharging to near the target capacity value.
[0036]
In this way, the operating point can be satisfactorily returned to the vicinity of the central coordinate point A.
[0037]
Claim 9 Claims according to the arrangement described 6 Or 7 In the battery control method for the electric power generation type electric vehicle described above, this central return processing is performed between the voltage characteristic line 43 or the coordinate G of the minimum SOC when the voltage characteristic line 43 deviates to the lower voltage side and the target capacity value. The capacity difference X is calculated, then charged by the capacity difference X, and the reference state battery voltage VM ′ at this time is rewritten as the target voltage value.
[0038]
In this way, the operating point can be satisfactorily returned to the vicinity of the central coordinate point A.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the invention will now be described with reference to the following examples.
[0040]
In addition to the hybrid vehicle described above, the power generation electric vehicle includes a fuel cell vehicle having a fuel cell and a battery that absorbs an imbalance between the generated power and the required power of the load.
[0041]
【Example】
A configuration example of a parallel hybrid vehicle using the battery control method of the present invention is shown in FIG.
[0042]
11 is an engine, 12 is an AC generator that generates power using a part of the driving force of the engine 11, 13 is an inverter that converts AC power output from the generator 12 into DC power, and 14 is a nickel metal hydride battery. It is a battery device (also simply referred to as a battery) composed of an assembled battery. The output of the engine 11 is transmitted to the wheels 18 via the torque distributor 15 and the gear 17. The inverter 13 is supplied with power from the generator 12 and the battery 14 to drive the motor 16, or charges the battery 14 with the electric power regenerated by the motor 16.
[0043]
FIG. 2 is a block diagram showing the battery 14 of the hybrid vehicle shown in FIG.
[0044]
In the battery 14, 21 is a battery pack, 22 is a number of battery modules that are connected in series with each other to form the battery pack 22, 23 is a temperature sensor, 24 is a detection circuit that detects the voltage of each battery module 22, and 25 is a temperature detection A circuit 26 is a current detection circuit, 27 is 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. is there. 28 is a vehicle controller that actually controls charging / discharging of the battery pack 21 based on the SOC signal from the battery 14, and the vehicle controller 28 is an engine based on input information from the battery control microcomputer 27 and each part of the vehicle. 11. The generator 12 and the inverter 16 are controlled.
[0045]
FIG. 3 shows the voltage-current characteristics of the nickel metal hydride battery (single cell) used in this example when the vehicle is actually running.
[0046]
In FIG. 3, the 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 per battery cell. It is shown.
[0047]
In FIG. 3, the broken line 31 represents current and voltage characteristics when the battery capacity is in a fully charged state, and the broken line 32 represents the battery voltage at the minimum guaranteed operating voltage V_min when the battery capacity is discharged at the maximum discharge power value. The current and voltage characteristics when the value is reached are shown. As described above, the current and voltage characteristics are high as shown by the characteristic 31 near full charge, and the voltage decreases as the characteristic 32 when the battery capacity is reduced.
[0048]
Here, in the characteristic 31, the coordinate point of current = 0A is the point of the capacity P_max ′ and the voltage V_max ′, and in the characteristic 32, the coordinate point of current = 0A is the point of the capacity P_min ′ and the voltage V_min ′. In this way, the current and voltage characteristics during running are measured, the voltage value is converted so as to be a predetermined constant current value (for example, current = 0 A), and this is used as the reference state battery voltage, and these capacity values and If the reference state battery voltage value is used, it is possible to remove the influence of the voltage fluctuation in the current change.
[0049]
Alternatively, in the current and voltage characteristic 31 near full charge, the point at a predetermined constant power discharge (here, at the maximum discharge power value) is P_max and the voltage V_max, and in the characteristic 32, the point at the constant power discharge is P_min, This is the point of voltage V_min. In this way, the current and voltage characteristics during running are measured, the voltage value is converted so as to become a predetermined constant power value, and this is used as the reference state battery voltage, and these capacity value and reference state battery voltage value are By using, it is possible to remove the influence of voltage fluctuations in the power change.
[0050]
In this way, the relationship between the reference state battery voltage and the capacity at a predetermined constant power (or constant current) can be obtained.
[0051]
FIG. 4 shows the relationship between the reference state battery voltage and capacity during constant power discharge (here, the maximum discharge power value). As an example of constant current, the reference state battery voltage (open voltage) and capacity when current = 0 A is shown. FIG. 5 shows the relationship. Since both are almost the same, the case of FIG. 4 will be described below.
[0052]
In FIG. 4, 41 is a voltage characteristic (minimum voltage characteristic line at the time of discharge) measured when the SOC is 100%, and 42 is a voltage characteristic (charge) measured when there is a charge tendency from a state close to complete discharge. Maximum voltage characteristic line). It can be seen that the characteristics of 41 and 42 are greatly shifted, and a large hysteresis occurs in the characteristics of the discharge tendency and the charge tendency.
[0053]
Reference numeral 43 denotes a voltage characteristic line when discharging from the coordinate P_Hi (ordinary maximum capacity value Q) of the SOC 80% to the coordinate P_Lo (ordinary minimum capacity value P) of the SOC 40%, and 44 denotes the SOC 80 from the coordinate P_Lo point of the SOC 40%. It is a voltage characteristic line when it is charged to the coordinate P_Hi point of%. It can be seen that the hysteresis surrounded by the characteristics of the voltage characteristic lines 43 and 44 is significantly smaller than the hysteresis surrounded by the voltage characteristic lines 41 and 42. The voltage at the coordinate P_Hi point is V_Hi (normal maximum voltage value Vq), and the voltage at the coordinate P_Lo point is V_Lo (normal minimum voltage value Vp).
[0054]
More specifically, the coordinate P_Hi point of SOC 80% can be regarded as a point of SOC 80% on the charging maximum voltage characteristic line 42 indicating the capacity-voltage characteristic at the time of charging from a substantially fully discharged state. It can be reached by charging from a fully discharged state to SOC 80% (or V_Hi). Similarly, the coordinate P_Lo point of SOC 40% can be substantially regarded as a point of SOC 40% on the minimum voltage characteristic line 43 at the time of discharge indicating the capacity-voltage characteristic at the time of discharging from a substantially fully charged state. It can be reached by discharging from the state of charge to SOC 40% (or V_Lo).
[0055]
In FIG. 4, 43 is a line (normal minimum voltage characteristic line) showing a change in the reference state battery voltage when discharging from the coordinate P_Hi point, and 44 is a reference state battery voltage when charging / discharging from the coordinate P_Lo point. It is a line (normal maximum voltage characteristic line) showing the change of. Therefore, once the coordinate P_Hi point or the coordinate P_Lo point is reached, the battery is charged / discharged (hereinafter also referred to as standard charge / discharge) between 40 to 80% capacity or a reference state battery voltage V_Hi or V_Lo corresponding thereto. In that case, it can be seen that the relationship between the battery's reference state battery voltage and capacity is within the diagonal lines in FIG.
[0056]
Next, as the target voltage value Vc or the reference voltage value according to the present invention, a point of a capacity of 60% and a reference state battery voltage (also simply referred to as a battery voltage) VM is set as a substantially central point of the hatched area.
[0057]
Therefore, if standard charge / discharge is performed, the battery voltage is VM, which means that regardless of the past charge / discharge history, from the capacity value of about 55% at the intersection of VM and the normal minimum voltage characteristic line 43, VM It can be seen that the fluctuation range of the capacity can be limited to 10% up to a capacity value of about 65% at the intersection of the normal maximum voltage characteristic line 44 and the common maximum voltage characteristic line 44.
[0058]
The same applies to FIG. 5. If VM ′ corresponding to the VM is appropriately taken, if the voltage at the time of current = 0 A is VM ′, the capacity fluctuation range is about 55 regardless of the past charge / discharge history. It can be seen that it can be estimated from% to about 65%.
[0059]
Next, FIG. 6 shows the result of examining the charge / discharge characteristics (reference state battery voltage-capacity characteristics) in the characteristic lines 43 and 44 in FIG. 4 in more detail.
[0060]
61 is a characteristic line when charging from a predetermined point P1 to P2 on the common minimum voltage characteristic line 43 when discharging from the coordinate P_Hi point, and 62 is a characteristic line when discharging from P2 to P3.
[0061]
From FIG. 6, the characteristic line 61 when the capacity changes from the coordinate P1 due to the charging tendency converges to the coordinate P_Hi point. Furthermore, it can be seen that when charging from an arbitrary point on the characteristic line 43, it converges to the coordinate P_Hi point. On the other hand, it can be seen that the characteristic line 62 when the capacity transitions from the coordinate P2 due to the tendency to discharge converges to the coordinate P1.
[0062]
That is, it can be seen that the discharge from the predetermined point in the normal region surrounded by the characteristic lines 43 and 44 is directed to the charging start point in the charging up to the predetermined point before that point if it is on the characteristic line 43.
[0063]
Similarly, it can be seen that charging from a predetermined point in the normal area surrounded by the characteristic lines 43 and 44 is directed to the discharge starting point in the discharge up to the predetermined point before that point if it is on the characteristic line 44. .
[0064]
In other words, it can be seen that within this normal range, once the battery is discharged or charged from a certain state and then returned to the SOC, the voltage will also return to the original value. This is a characteristic common to all rechargeable secondary batteries as well as nickel metal hydride batteries, and is called a polarization phenomenon.
[0065]
Here, it is assumed that the capacitance value at the voltage VM on the characteristic line 43 is SOC1, and the capacitance value at the voltage VM on the characteristic line 44 is SOC2. The voltage VM is determined as a target voltage value Vc so that SOC1 and SOC2 are equal to each other around the capacity of 60%.
[0066]
In this state, it is assumed that traveling is started from the coordinate P_Hi point. When the generator 12 is controlled so that the battery voltage at the time of constant power discharge (reference state battery voltage) becomes VM while the hybrid vehicle is running, the coordinate P_Hi point changes on the characteristic 43, and the SOC starts from 80%. It can be seen from FIG. 6 that the characteristic 43 shifts to SOC1 where it crosses the voltage VM and is stable.
[0067]
Thereafter, the driver travels to consume the battery capacity. For example, when reaching the SOC at the coordinate P1 point, the voltage is restored to the voltage VM on the characteristic line 61, so the SOC is almost 60%. It turns out to be stable.
[0068]
That is, by limiting the capacity fluctuation range to SOC 80% to 40% (or limiting the battery voltage to V_Hi to V_Lo) and reducing the battery characteristic hysteresis, the SOC is maintained at least in the range of SOC1 to SOC2. . Furthermore, when charging and discharging are repeated, the capacity gradually converges to the target capacity value (SOC 60%) corresponding to the target voltage value Vc (VM).
[0069]
In addition, the lead battery etc. with a small hysteresis characteristic of a battery can maintain the target capacity | capacitance, without limiting the use range of battery capacity. Further, by setting the voltage VM with respect to the capacity for maintaining the battery capacity, the capacity to be maintained can be changed to an arbitrary capacity instead of 60% of the present embodiment.
[0070]
(Charge / discharge control example 1)
An example of a battery capacity control device for a hybrid vehicle realized using the charge / discharge control will be described below.
[0071]
First, a reference state battery voltage at a constant power (or a reference state battery voltage at a constant current) is calculated from a pair of a detection voltage and a detection current. After the operating point is placed on the characteristic line 43 or 44 by the above-described method, charging / discharging is controlled so that the battery voltage does not deviate from the range of V_Hi to V_Lo. Specifically, charging is prohibited when the battery voltage V_Hi is reached, and discharging is prohibited when the battery voltage reaches V_Lo. Apart from this, a temporary SOC is calculated by integrating the current. Next, the SOC is corrected based on the comparison result.
[0072]
This SOC correction will be described in more detail. When the capacity obtained by current integration reaches the target capacity value of 60%, the difference between the reference state battery voltage and the VM as the target voltage value Vc is obtained. Charging or discharging as compensation charging / discharging is performed until In addition, since this difference can be regarded as a current integration error, it is not accumulated in the value of the current integration capacity.
[0073]
If it does in this way, after that, until the capacity | capacitance calculated | required by the current integration reaches the target capacity value of 60%, the capacity is estimated using the current integrated capacity without an integration error, and the current integrated capacity and the target capacity value Based on the difference, the charge / discharge control is performed so as to eliminate this difference, whereby the capacity can be converged to the target capacity value.
[0074]
In this example, instead of controlling the charge / discharge so that the battery voltage does not deviate from the range of V_Hi to V_Lo, the charge / discharge control may be performed so that the current integrated capacity does not deviate from the range of P_Hi to P_Lo. Good.
[0075]
7 to 11 show actual travel data when the battery charge / discharge control is performed during the travel of the hybrid vehicle using the charge / discharge control example 2 described above. FIG. 7 shows the power flowing through the battery pack 21 during traveling, and FIG. 8 shows the battery temperature. FIG. 9 shows the transition of the remaining capacity (SOC) during travel, where 831 is the capacity value (also referred to as the SOC detection value) obtained in charge / discharge control example 2, and 832 is the current integration after measuring the capacity in advance. Is the true value obtained by. FIG. 10 shows a difference between the SOC detection value obtained in FIG. 9 and the true value, that is, a detection error. The detection error is about +4 to -4%, and it can be seen that highly accurate detection was realized. In FIG. 11, 851 is a control target voltage VM, and 852 is a battery voltage (that is, a reference state battery voltage) at the time of constant power discharge (21 kW for the entire battery pack 212) obtained by the moving average method. From FIG. 11, it can be seen that the constant power discharge voltage is controlled to be the target voltage VM during traveling.
[0076]
Next, a specific control operation of the above-described charge / discharge control example 2 will be described below with reference to FIGS.
[0077]
FIG. 12 shows charge / discharge control of the vehicle controller 28.
[0078]
The vehicle controller 28 is configured 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. Next, control is performed to instruct a prime mover controller (not shown) that controls the engine 11.
[0079]
FIG. 12 shows specific control of the part related to charge / discharge control of the battery 14 by the vehicle controller 28.
[0080]
In step 1000, the SOC is read from the battery controller 27, and in step 1002, the difference between the read SOC and the target SOC that has been set in advance is obtained, and this is used as the battery required power value.
[0081]
In step 1004, the travel load power calculated in advance is added to the calculated battery required power value to obtain the total load power, and the engine output request value is matched with the total load power. Since this control itself in the hybrid vehicle is not the gist of this embodiment, further explanation is omitted.
[0082]
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, but this control is not the gist of this embodiment. Is omitted.
[0083]
13 to 15 show control operations performed by the battery controller (battery control microcomputer) 27, which will be described below.
[0084]
In the past, the operating point was previously set on the characteristic line 43 or 44 by the above-described method, and then charging / discharging is controlled so that the battery voltage does not deviate from the range of V_Hi to V_Lo. , Between the characteristic lines 43 and 44.
[0085]
In FIG. 13, first, in step 901, the running voltage VB, current IB, and temperature TB are detected, and the internal resistance Rk is calculated by the least square method based on a plurality of pairs of voltage VB and current IB. A voltage VBw at a predetermined power discharge is calculated as the reference state battery voltage (S902).
[0086]
VB0 = VB + Rk × IB
VBw = {VB0 + (VB0 ² -4 x Rk x α) ^0.5 } × 0.5
Α is the constant power used (21 kW in this case).
[0087]
Next, in step 903, the SOC is calculated by the current integration method, and is restored to an SOC (−57 to + 63%) that is very close to the target capacity value (here, 60%) targeted by the battery capacity control device. (S904), if not, the process proceeds to step 907, and if so, the process proceeds to step 907 via step 906.
[0088]
In step 906, the reference state battery voltage VBw is compared with the target voltage VM. If VBw is lower than VM, the SOC obtained in step 903 is corrected. At this time, since it is necessary to charge if VBw <VM, the SOC is rewritten to a value smaller than about 60% obtained by the current integration, whereby the vehicle controller 28 sets each part so that the SOC becomes 60%. Command, resulting in charging.
[0089]
Since it is necessary to discharge if VBw> VM, the SOC is rewritten to be higher than the above-mentioned approximately 60% obtained by the current integration, whereby the vehicle controller 28 in each step so that the SOC is set to 60% in the steps described later. As a result, discharge occurs. The correction amount at one time may be 1 to 0.01%, and can be gradually corrected to an accurate value by repeatedly correcting.
[0090]
In step 907, the calculated SOC is actually output to the vehicle controller 28 that controls the generator 12 and the like. In step 908, it is monitored whether the SOC is in the range between the upper limit of 80% and the lower limit of 40%. This subroutine will be described below with reference to FIGS.
[0091]
In FIG. 14, in step 1001, it is determined whether the obtained SOC exceeds 80%, and in step 1002, a charge restriction command for prohibiting further charging is output to the controller 12. In step 1003, it is determined whether the obtained SOC is less than 40%, and in step 1004, a discharge restriction command for prohibiting further discharge is output to the controller 12.
[0092]
As another method, as shown in FIG. 15, the upper limit and the lower limit of the SOC may be monitored by the reference state battery voltage.
[0093]
More specifically, if the reference state battery voltage VBw during constant power discharge exceeds V_Hi in step 1101, a charge limit command is output in step 1102 in order to prevent further charging. When the reference state battery voltage VBw at the time of constant power discharge or V_Lo corresponding to 40% SOC is lower than V_Lo in step 1103, a discharge restriction command is output in step 1104 to prevent further discharge. In this case, the upper and lower limits are detected by the reference state battery voltage VBw at the time of constant power discharge, and the upper and lower limits are detected by the reference state battery voltage at the constant current discharge (for example, voltage at current = 0 A) VBo. Also good. In FIG. 13, when the travel is completed in step 909, the result of the calculation is stored in a memory or the like (not shown) in step 910 so as to be the initial value at the start of the next travel, and the series of controls is terminated.
[0094]
Next, a measurement example of the SOC change by the above charge / discharge control will be described with reference to FIG.
[0095]
From the start of travel to point 121, the SOC current integration detection value is within the range of 57 to 63%, so that the SOC detection value is corrected to an accurate value in step 906. When the driver performs driving that consumes a large amount of battery power, the SOC decreases to less than 57% SOC as shown between points 121 and 122, so the SOC calculated in step 903 is output to the controller 28. The
[0096]
Since the SOC lower limit value 40% is reached at the point 122, the discharge is limited by the step 908, and the capacity such as the 122 to 123 points is recovered. When the point 123 is reached, the SOC falls within the range of 57% to 63%, so that the SOC detection value is corrected to an accurate value again at step 906.
[0097]
Thus, even if the SOC fluctuates, it is possible to quickly return to the target SOC, and it is possible to correct the SOC detection value obtained by the current integration in which the accumulated error occurs.
[0098]
(Charge / discharge control example 2)
Another example of a battery capacity control device for a hybrid vehicle realized using the charge / discharge control will be described below.
[0099]
First, a reference state battery voltage at a constant power (or a reference state battery voltage at a constant current) is calculated from a pair of a detection voltage and a detection current. Next, after the operating point is placed on the characteristic line 43 or 44 by the above-described method, charging / discharging is controlled so that the battery voltage does not deviate from the range of V_Hi to V_Lo. Specifically, when the battery voltage V_Hi is reached, a command for prohibiting charging is issued to the vehicle controller 28, and when the battery voltage reaches V_Lo, a command for prohibiting discharging is issued. Next, the difference between the reference state battery voltage and the voltage VM, which is the target voltage value Vc, is obtained, and an instruction is given to cause charging / discharging in the direction to eliminate the difference, thereby matching the reference state battery voltage with VM.
[0100]
In this way, the capacity can be held between SOC1 and SOC2 shown in FIG.
[0101]
(Recovery from specific voltage drop phenomenon 1)
Next, countermeasures in the case where the operating characteristics change specifically due to an increase in memory drop or a large charge polarization cancellation will be described below.
[0102]
First, this specific voltage drop phenomenon will be described.
[0103]
As described above, in the charge / discharge control according to the embodiment, as shown in FIG. 17, the reference state battery voltage is used during normal charging / discharging within the range between the normal minimum capacity value P and the normal maximum capacity value Q. The center value (target voltage value) VM between the minimum voltage value Vp and the normal maximum voltage value Vq between the normal minimum voltage value Vp and the SOC of the target capacity value of 60%, that is, the central coordinate point A is converged. .
[0104]
However, due to the decrease in the reference state battery voltage due to the increase in the memory effect and the decrease in the amount of charge polarization, the operating point at the time of discharge is the capacity (SOC) and the reference state battery as shown in FIG. It was found that the voltage characteristic line 43 on the two-dimensional plane defined by the voltage (21 kW discharge voltage) may deviate downward from the voltage characteristic line 43 (showing characteristics when discharging from Q). Further, when the memory effect does not occur and only the charge polarization is eliminated, the operating point reaches the voltage characteristic line 43. Hereinafter, this phenomenon is referred to as a specific voltage drop phenomenon.
[0105]
For example, when this specific voltage drop phenomenon occurs, as shown in FIG. 18, the SOC 40% passes from the central coordinate point A through the coordinate B on the voltage characteristic line 43 and the coordinate P ′ on the discharge minimum voltage characteristic line 41. The coordinate P ″ is reached, the normal discharge path 106 is traced, and the coordinate (ordinary minimum capacity value P) P is not reached.
[0106]
When this specific voltage drop phenomenon occurs, the operating point on the two-dimensional plane remains at the voltage characteristic line 44 (characteristic when charging from P) even if the reference state battery voltage is restored to the original median value VM. Between the median minimum capacity value SOCmmin, which is the capacity of the intersection point O ′ between the center value VM, and the median maximum capacity value SOCmmax, which is the capacity of the intersection point O between the discharge minimum voltage characteristic line and the median value VM. Since the center capacitance value, that is, the capacitance value of the central coordinate point A does not return to 60%, a large deviation occurs in the subsequent control.
(Return method from specific voltage drop 1)
Therefore, in this control, when the above-mentioned specific voltage drop phenomenon occurs, the central return operation shown in the characteristic diagram of FIG. 19 and the flowchart of FIG. 21 is performed. This flowchart is executed by interrupting the main routine of FIG. 13 at a predetermined timing.
[0107]
First, it is checked whether the operating point (VBw, current SOC value) is on the voltage characteristic line 43 stored in advance on the map of FIG. 19 or on the lower voltage side (1100). Helical return.
[0108]
If the operating point (VBw, current SOC value) is on the voltage characteristic line 43 or a lower voltage side, the subsequent operating point is monitored, and the operating point C when switching from discharging to charging (see FIG. 19) The capacity difference X between the capacity value (minimum SOC value) and the target capacity value (60%) is calculated (1102).
[0109]
Next, X is multiplied by a pre-stored multiplication charge coefficient α (a value greater than 1 and less than 2) to obtain a multiplication charge capacity X ′, and only the multiplication charge capacity X ′ is charged. (1104).
[0110]
Next, discharging is performed, discharging is performed up to the median value VM, and the operating point is returned to the vicinity of the coordinate A (1106).
[0111]
The feature of this control is that when the operating point reaches the voltage characteristic line 43 or deviates to a lower voltage side, instead of charging only by X in normal control, the multiplication is increased by a multiplication charge coefficient α from X. The battery is charged and then converges to the median value VM.
[0112]
In this way, even if the specific voltage drop phenomenon occurs, the operating point can be easily returned to the vicinity of the central coordinate point A.
(Modification)
In addition, you may reach | attain repeating charging / discharging, without performing the multiplication charge from the coordinate C to the coordinate D continuously.
[0113]
Further, the subsequent discharge from the coordinate D to the median value VM may be achieved while repeating the charge / discharge without continuously performing the discharge.
[0114]
Furthermore, when the operating point does not reach D due to vehicle operation control when returning from the coordinate C to the coordinate D, the coordinate D may be estimated from this operating point when the operating point reaches the vicinity of D. .
(Return method 2 from specific voltage drop phenomenon)
Other return methods are described below. In this return method, when the above specific voltage drop phenomenon occurs, the center return operation shown in the characteristic diagram of FIG. 20 and the flowchart of FIG. 22 is performed. This flowchart is executed by interrupting the main routine of FIG. 13 at a predetermined timing.
[0115]
First, it is checked whether the operating point (VBw, current SOC value) is on the voltage characteristic line 43 stored in advance on the map of FIG. 20 or on the lower voltage side (1100). Helical return.
[0116]
If the operating point (VBw, current SOC value) is on the voltage characteristic line 43 or a lower voltage side, the subsequent operating point is monitored and the operating point G when switching from discharging to charging (see FIG. 20). The capacity difference X between the capacity value (minimum SOC value) and the target capacity value (60%) is calculated (1102).
[0117]
Next, by charging only this capacity difference X, the SOC is returned to the coordinate H corresponding to the SOC value 60% of the central coordinate point A (1204).
[0118]
Next, the median value VM is rewritten to the reference state battery voltage VM ′ at this time (1206).
[0119]
The feature of this control is that when the operating point reaches the voltage characteristic line 43 or the operating point deviates outside the voltage characteristic line 43, in the normal control, instead of charging only the capacity X, further charging only X is performed thereafter. The reference state battery voltage VM ″ when the capacity value at the center coordinate point A is reached is newly rewritten to the median value VM.
[0120]
In this way, even if the specific voltage drop phenomenon occurs, the operating point can be easily returned to the vicinity of the central coordinate point A.
(Modification)
In addition, you may reach | attain repeating charging / discharging, without performing charging from the coordinate G to the coordinate H continuously.
[0121]
Further, if the operating point does not reach H due to the vehicle operation control when returning from the coordinate G to the coordinate H, the coordinate H may be estimated from the operating point when the operating point reaches near H. Good.
(Return method 3 from specific voltage drop phenomenon)
In this control, the large memory effect and the charge polarization elimination are discriminated, and the memory effect is removed by performing deep discharge at the opportunity in the former case.
[0122]
A control example will be described with reference to FIG.
[0123]
First, it is checked whether or not the voltage characteristic line 43 has been lowered to a lower potential side by a discharge or more than a predetermined voltage value (1302). If the voltage characteristic has decreased, it is determined that a large memory effect has occurred. A discharge process is requested (1304).
[0124]
This deep discharge treatment is a known memory effect elimination method that eliminates the memory effect due to deep discharge up to SOC 10% or less. This deep discharge treatment is performed by, for example, the above-described restoration method 1 or 2 after the completion of the deep discharge treatment. Return processing to the vicinity of the central coordinate point A.
[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 electrical 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 vehicle travel.
4 is a diagram showing voltage-capacitance characteristics in a constant power state created based on FIG. 3; FIG.
FIG. 5 is a diagram showing voltage-capacitance characteristics in a constant current state created based on FIG. 3;
6 is a diagram showing voltage-capacitance characteristics in a constant power state showing the charge / discharge locus in FIG. 4; FIG.
FIG. 7 is a timing chart showing a transition of electric power that flows to the battery pack 21 during traveling.
FIG. 8 is a timing chart showing changes in battery temperature of the battery pack 21 during traveling.
FIG. 9 is a timing chart showing a change in SOC of the battery pack 21 during traveling.
FIG. 10 is a timing chart showing an SOC detection error of the battery pack 21 during traveling.
FIG. 11 is a timing chart showing changes in the reference state battery voltage of the battery pack 21 during travel.
FIG. 12 is a flowchart showing a battery control method of this embodiment.
FIG. 13 is a flowchart showing a battery control method of this embodiment.
FIG. 14 is a flowchart showing a battery control method of this embodiment.
FIG. 15 is a flowchart showing a battery control method of this embodiment.
FIG. 16 is a timing chart showing a change in SOC during actual traveling of the hybrid vehicle using the battery control method of this embodiment.
FIG. 17 is a battery characteristic diagram showing a relationship between battery voltage and capacity in charge / discharge of reference power (21 kW) showing the battery control method of this example.
FIG. 18 is a battery characteristic diagram showing a specific voltage drop phenomenon.
FIG. 19 is a battery characteristic diagram showing an example of a process for returning a battery in which a specific voltage drop phenomenon has occurred to the vicinity of the central coordinate point A;
FIG. 20 is a battery characteristic diagram showing another example of a process for returning a battery in which a specific voltage drop phenomenon has occurred to the vicinity of the central coordinate point A;
FIG. 21 is a flowchart showing an example of a process for returning a battery in which a specific voltage drop phenomenon has occurred to the vicinity of the central coordinate point A;
FIG. 22 is a flowchart showing another example of a process for returning a battery that has caused a specific voltage drop phenomenon to the vicinity of the central coordinate point A;
FIG. 23 is a flowchart showing still another example of a process for returning a battery in which a specific voltage drop phenomenon has occurred to the vicinity of the central coordinate point A;

Claims (9)

In a battery control method for an electric vehicle, comprising: a power generation means; and a battery that stores power generated by the power generation means and supplies power to a traveling motor.
Based on the measured voltage value and measured current value of the measured battery, a reference state battery voltage that is a battery voltage at a predetermined reference current value or a predetermined reference power value is calculated,
Set a predetermined target voltage value corresponding to the normal capacity range in the reference current value or the reference power value,
Control charging / discharging of the battery so as to eliminate the difference between the calculated reference state battery voltage and the target voltage value ,
A predetermined normal minimum capacity value on a minimum voltage characteristic line at the time of discharge indicating a capacity-voltage characteristic that is a relationship between a capacity at the time of discharging from a substantially fully charged state of the battery and the reference state battery voltage is P, and A point on the maximum voltage characteristic line during charging indicating a capacity-voltage characteristic that is a relationship between the capacity at the time of charging from a substantially fully discharged state of the battery and the reference state battery voltage, or a value charged by a predetermined capacity from the P When the predetermined normal maximum capacity value is Q, the target voltage value is set to the normal maximum voltage value Vq and the normal minimum voltage value Vp individually corresponding to the normal minimum capacity value P and the normal maximum capacity value Q. A battery control method for a power generation type electric vehicle, characterized in that charging / discharging is performed between the normal minimum capacity value P and the normal maximum capacity value Q. The battery control method for a power generation type electric vehicle according to claim 1 ,
A battery control method for a power generation type electric vehicle, wherein the target voltage value is set to a value in the vicinity of a median value between the normal maximum voltage value Vq and the normal minimum voltage value Vp. In the battery control method of the power generation type electric vehicle according to claim 1 or 2 ,
Accumulating the charge / discharge current accumulated amount to the initial capacity value to calculate the current accumulated capacity which is the capacity by the current accumulation of the battery,
Based on the measured voltage value and measured current value of the measured battery, a reference state battery voltage that is a battery voltage at a predetermined reference current value or a predetermined reference power value is calculated,
Storing a predetermined reference capacity value of the battery and a predetermined reference voltage value corresponding thereto;
In the case where the current accumulated capacity and the reference capacity substantially coincide with each other, correction charge / discharge that eliminates a difference between the reference state battery voltage and the reference voltage value is performed, and the capacity by the current accumulation is corrected. A battery control method for a power generation electric vehicle. In the battery control method of the power generation type electric vehicle according to claim 3 ,
The reference voltage value is the target voltage value,
The reference capacity value is a predetermined target capacity value in the vicinity of a median value between the normal minimum capacity value P and the normal maximum capacity value Q;
A battery control method for a power generation type electric vehicle characterized by performing charge / discharge control for converging the current accumulated capacity to the target capacity value. In the battery control method of the power generation electric vehicle according to any one of claims 1 to 4, a battery control method of the power generation electric vehicle, wherein the battery is a nickel-hydrogen battery. The battery control method for a power generation type electric vehicle according to claim 2 ,
Accumulating the charge / discharge current accumulated amount to the initial capacity value to calculate the current accumulated capacity which is the capacity by the current accumulation of the battery,
Based on the measured voltage value and measured current value of the measured battery, a reference state battery voltage that is a battery voltage at a predetermined reference current value or a predetermined reference power value is calculated,
A central coordinate point A defined by a predetermined target capacity value that is a value in the vicinity of a median value between the maximum common capacity value Q and the minimum normal capacity value P, and the target voltage value;
On the two-dimensional plane of the reference state battery voltage and the capacity, set a voltage characteristic line 43 when discharging from the normal maximum capacity value Q to the normal minimum capacity value P when there is no memory effect;
A battery for a power generation type electric vehicle characterized in that when the operating point reaches the voltage characteristic line 43 or deviates to the low voltage side, a central return process is performed to return the operating point to the central coordinate point A. Control method. The battery control method for a power generation type electric vehicle according to claim 6 ,
Determining whether the operating point has deviated more than a predetermined voltage width to a lower voltage side than the voltage characteristic line 43;
Battery control for a power generation type electric vehicle characterized in that it is determined that a large memory effect has occurred when deviating and a memory effect elimination and subsequent central return processing are requested by deep discharge up to a predetermined SOC value or less Method. In the battery control method of the electric power generation type electric vehicle according to claim 6 or 7 ,
The center return process calculates a capacitance difference X between the voltage characteristic line 43 or the coordinate C of the minimum SOC when deviating to a lower voltage side than the voltage characteristic line 43 and the target capacity value,
Next, a multiplication charge capacity X ′ is calculated by multiplying the capacity difference X by a multiplication charge coefficient α (a value greater than 1 and less than 2) stored in advance.
Next, the multiplication charge capacity X ′ is charged from the coordinate C,
Next, a battery control method for a power generation type electric vehicle characterized by discharging to the vicinity of the target capacity value. In the battery control method of the electric power generation type electric vehicle according to claim 6 or 7 ,
The center return process calculates a capacity difference X between the voltage characteristic line 43 or the coordinate G of the minimum SOC when the voltage characteristic line 43 deviates to a lower voltage side than the voltage characteristic line 43 and the target capacity value,
Next, the battery control method for a power generation type electric vehicle is characterized in that only the capacity difference X is charged and the reference state battery voltage VM ′ at this time is rewritten as the target voltage value.

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