JPH09312901A - Electric power controller of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably control charge and discharge power of a battery. SOLUTION: A discharge current at a first voltage of a battery 11 is estimated on the basis of a voltage and a current of the battery 11 which are measured when a discharge current is increased. On the basis of the estimated discharge current, the maximum discharge power of the battery 11 is operated, and a discharge power of the battery 11 is operated on the basis of a specified discharge current smaller than the estimated discharge current. The discharge power of the battery 11 is restricted to the smaller value out of these operation results of electric power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling discharge power and regenerative charge power of a battery mounted on an electric vehicle.

[0002]

2. Description of the Related Art A battery, which is an energy source of an electric vehicle, has a characteristic that electric power that can be discharged or charged changes with the lapse of time of a discharge reaction or a charging reaction. On the other hand, in an electric vehicle, the charging / discharging power required according to the running load changes momentarily according to the running pattern.

[0003]

There is no problem if the battery can always supply the necessary electric power according to the driving pattern of the electric vehicle, but the driving pattern depends on the conditions such as the depth of discharge of the battery, the charging / discharging current, and the charging / discharging time. It may not be possible to supply power according to. In such a case, the terminal voltage of the battery exceeds the maximum allowable voltage Vmax or the discharge end voltage Vm
It is necessary to control the charge / discharge power so that it does not become lower than in.

An object of the present invention is to provide a power control device for an electric vehicle that optimally controls the charging / discharging power of a battery.

[0005]

[Means for Solving the Problems]

(1) According to the invention of claim 1, a voltage measuring means for measuring a voltage of the battery, a current measuring means for measuring a current flowing through the battery, a voltage measuring means and a voltage when the discharge current increases measured by the current measuring means Current estimating means for estimating the discharge current of the battery at the first voltage based on the current and current, first calculating means for calculating the discharge power of the battery based on the discharge current at the first voltage, and A second calculation means for calculating the discharge power of the battery based on a predetermined discharge current smaller than the discharge current at the voltage, and the discharge power of the battery among the power calculated by the first and second calculation means. And a power control means for limiting to a smaller one. The discharge current at the first voltage of the battery is estimated based on the voltage and current of the battery measured when the discharge current increases, the discharge power of the battery is calculated based on this estimated discharge current, and the discharge current is determined to be smaller than the estimated discharge current. The discharge power of the battery is calculated based on the discharge current of, and the discharge power of the battery is limited to a smaller value of these power calculation results. (2) The electric power control device for an electric vehicle according to a second aspect of the invention is based on the voltage and the current at the time when the discharge current increases measured by the current estimating means by the voltage measuring means and the current measuring means. The charging current is estimated, the charging power of the battery is calculated by the first calculating means based on the charging current at the second voltage, and the second calculating means determines a predetermined value smaller than the charging current at the second voltage. The charging power of the battery is calculated based on the charging current, and the power control unit limits the charging power of the battery to a smaller value of the powers calculated by the first and second calculating units. The charging current at the second voltage of the battery is estimated based on the voltage and the current of the battery measured when the discharging current increases, and the charging power of the battery is calculated based on this estimated charging current, and the predetermined charging current is smaller than the estimated charging current. The charging power of the battery is calculated based on the charging current of, and the charging power of the battery is limited to a smaller value of these power calculation results. (3) An electric power control device for an electric vehicle according to a third aspect of the invention determines a predetermined discharge current and a predetermined charging current based on a maximum rated current of an electric motor of the electric vehicle. (4) A power control device for an electric vehicle according to claim 4 is the first
Is the discharge end voltage of the battery. (5) A power control device for an electric vehicle according to claim 5 is the second power control device.
Is the maximum allowable voltage of the battery.

[0006]

【The invention's effect】

(1) According to the invention of claim 1, since the maximum rated current of the electric motor can be reduced, the electric motor and the inverter can be downsized, and the cost and weight of the motor and the inverter can be reduced. (2) According to the invention of claim 2, the same effect as that of claim 1 can be obtained. (3) According to the invention of claim 3, in addition to the effect of claim 1, even when the battery is in the final stage of discharge, the battery can be discharged up to the maximum rated current, and a large output can be maintained. (4) According to the invention of claim 4, the maximum discharge current of the battery can be estimated, and the accurate maximum discharge power can be obtained. (5) According to the invention of claim 5, the maximum charging current of the battery can be estimated, and the accurate maximum charging power can be obtained.

[0007]

1 is a block diagram showing the structure of a traveling drive mechanism of an electric vehicle according to an embodiment. During power running, the battery 11 is discharged to supply DC power to the inverter 12, and the inverter 12 converts the DC power into AC power and applies it to the motor 13. As a result, the motor 13 generates running energy and the vehicle runs. On the other hand, during regeneration, the running energy of the vehicle is converted back into electric energy via the motor 13 and the inverter 12, and the battery 1
1 is charged and the vehicle is regeneratively braked. The voltage sensor 14 detects the voltage V across the battery 11, and the current sensor 15 detects the current I flowing through the battery 11. The current I is positive when flowing from the battery 11 to the inverter 12 when driving the motor, and is negative when flowing from the inverter 12 to the battery 11 during regenerative charging. The controller 16 calculates the maximum discharge power and the maximum charge power of the battery 11 based on the voltage V and the current I detected by the voltage sensor 14 and the current sensor 15, and controls the output of the inverter 12 based on the calculation result. Perform regenerative control.

<< Characteristics of Battery >> Here, the characteristics of the battery will be described. Certain types of batteries, such as lithium-ion batteries and nickel-hydrogen batteries, have the following characteristics. (1) As shown in FIG. 2, the depth of discharge of the battery (hereinafter, D
OD (Depth of Discharge) is low (~ 60)
%), The internal resistances during charging and discharging are almost the same. (2) The linearity of the voltage V-current I characteristic during charge / discharge is good. If such a characteristic of this type of battery is utilized, the DO
It is possible to accurately calculate the maximum discharge power and the maximum charge power according to the state of the battery such as D and temperature. The battery is not limited to the lithium ion battery or the nickel hydrogen battery, and may be any battery having the above characteristics.

Generally, a battery has a characteristic that when discharged at a constant current, the voltage decreases as the discharge reaction progresses, and when charged at a constant current, the voltage rises as the charging reaction progresses. FIG. 3 shows changes in the terminal voltage V of the battery when discharged at a constant current. From time t1 to t3
Up to the terminal voltage V
Changes as shown in the figure. At the discharge start time t1, the terminal voltage V instantly drops from V0 to V1 at 0.1 mS or less. This transient voltage VX is a voltage drop due to the liquid resistance and contact resistance of the battery. Next, in the period T1 from the time t1 to t2, the terminal voltage V rapidly decreases from V1 to V2. This fall time is 100 mS or less, and the transient voltage VY is a voltage drop due to the charge transfer resistance of the battery.
Further, in the period T2 from time t2 to time t3, the terminal voltage V gradually decreases from V2 to V3. This transient voltage VZ is a voltage drop due to concentration polarization of the electrolytic solution, and this region is generally called a diffusion region. After that, when the discharge stop time t3 has passed, the terminal voltage V recovers rapidly. Periods T1 and T3 are transient states that change in a short time, and period T2 is a normal use state of the battery. In this way, the terminal voltage of the battery changes according to the discharge current, and also changes over time of the discharge reaction. Therefore,
When the maximum discharge power of the battery is calculated based on the terminal voltage in the transient state of the discharge reaction, an error may occur, and in some cases, the terminal voltage at the time of discharging may fall below the discharge end voltage of the battery. The discharge end voltage is the allowable minimum voltage of a battery that cannot continue discharging any more.

<< Calculation Method of Maximum Charge / Discharge Power >> Next, a calculation method of the maximum discharge power and the maximum charge power of the battery will be described.
First, the V-I characteristic of the battery being discharged is sampled, and the sampling result is plotted on a V-I graph as shown in FIG. 4 (indicated by X in the figure). As described above, in this type of battery, the internal resistances during charging and discharging are almost the same, and the linearity of the V-I characteristic is good.
The −I characteristic can be linearly regressed, and the regression line can be extended to the charge side and the discharge side. In the figure, the V-axis intercept Eo of the regression line represents the open circuit voltage of the battery, and the slope of the regression line represents the internal resistance R of the battery. The regression line is

## EQU1 ## V = Eo-IR.

The current ICmax at the intersection A between the regression line and the maximum allowable voltage Vmax during charging gives a charge allowable value, and at the intersection A, the following equation holds.

## EQU00002 ## Vmax = Eo-ICmax.R Similarly, the current IDmax at the intersection B between the regression line and the discharge end voltage Vmin at the time of discharge gives a discharge allowable value, and at the intersection B, the following equation is established.

[Equation 3] Vmin = Eo-IDmax · R

The maximum charging power PC can be calculated by the above equation 2

## EQU00004 ## PC = Vmax.ICmax = Vmax. (Eo-Vmax) / R Further, the maximum discharge power PD can be calculated by the following equation 3.

## EQU00005 ## PD = Vmin.IDmax = Vmin. (Eo-Vmin) / R. The sampling value of the VI characteristic during discharging is a value according to the battery state such as the DOD and temperature of the battery, and the maximum charging power PC and the maximum discharging power PD obtained by linear regression of such sampling values. Is, of course, electric power according to the state of the battery such as DOD and temperature.

By the way, the discharge end voltage Vmin of a battery mounted on an electric vehicle is usually

[Formula 6] Vmin ≧ Eo / 2. On the other hand, in general, the maximum output P of a battery, that is, the maximum discharge power P is

## EQU7 ## It is known that V = Eo / 2 is obtained. Therefore, the discharge end voltage Vmin of the electric vehicle battery is

When set within the range of Vmin> Eo / 2, the maximum discharge power PD calculated by the above-mentioned method becomes smaller than the maximum discharge power of a general battery. In this specification, the discharge end voltage Vmin is expressed by Equation 6
The discharge power that is set within the range and is calculated for the set discharge end voltage Vmin is the maximum discharge power of the battery.

By the way, the motor 13 of the electric vehicle produces the maximum output when the maximum rated voltage and the maximum rated current are supplied, and the output decreases as the voltage or current decreases. When the terminal voltage V of the battery 11 drops to near the discharge end voltage Vmin, it is necessary to increase the current by the amount of the drop in voltage in order to maintain the maximum output. However,
The current cannot be increased indefinitely, and must be limited to the maximum rated current of the motor 13 or less. Since it is considered that such discharging of the battery 11 until the end of discharge is not actually frequent, it is sufficiently acceptable to temporarily limit the output at the end of discharge. By limiting the output, the maximum rated current of the motor 13 can be reduced, so that the motor 13 and the inverter 12 can be downsized, and the cost and weight can be reduced. Therefore, in this embodiment, the maximum charging / discharging current IDmax is reduced to IDmax 'when the maximum charging / discharging power is calculated.

## EQU9 ## IDmax '<IDmax This reduced current IDmax' is determined based on the maximum rated current of the motor 13.

5 and 6 show VI when the maximum discharge current IDmax is not reduced in the calculation of the maximum discharge power PD.
The characteristics and the maximum power characteristics are shown, and FIGS. 7 and 8 show the VI characteristics and the maximum power characteristics when the maximum discharge current IDmax is reduced. In these figures, PD is the maximum discharge power calculated by Equation 5, and represents the capacity of the battery. PI and PI 'are the maximum discharge currents IDmax and IDma, respectively.
It is the maximum discharge power calculated by the following equation based on x'and represents the motor capacity.

## EQU10 ## PI = IDmax (Eo-IDmax.R), PI '= IDmax'(Eo-IDmax'.R) Further, PM represents the maximum output of the motor 13, and PM 'can guarantee the specified mode running. Indicates the motor output. Current I
When the power PD is calculated without reducing Dmax, the motor capacity PI is around the battery capacity P around the point J1 shown in FIG.
If the output is to be made larger than D to maintain the output up to the full battery capacity PD, the motor current must be increased as described above, and the motor and the inverter become large and the weight and cost increase.

However, as shown in FIG. 7, the current IDmax is changed to I
When the power PD is calculated by reducing it to Dmax ', FIG.
The output is only slightly limited in the end-of-discharge region in the range from the J2 point to the J3 point, and the cost, weight and size of the motor and the inverter are not increased.
Of course, the motor output PM 'for ensuring the specified mode running is secured. In this embodiment, the maximum discharge power PD is calculated according to Expression 5, and the maximum discharge power PI ′ is calculated according to Expression 10, and the smaller one is set as the final maximum discharge power PD ′. In the calculation of the maximum charging power, similarly, the maximum charging current ICmax is set to the motor 1
The maximum discharge power (motor capacity) calculated based on these maximum charging currents ICmax and ICmax ′ is calculated, and the maximum charging power is calculated according to the above formula 4. PC (battery capacity)
Is calculated. Then, the smaller one is set as the final maximum charging power PC '.

<< Sampling Method of Battery VI Characteristics >>
Next, a method of sampling the V-I characteristic of the battery will be described. The relationship between the voltage V and the current I of the battery is expressed by the above mathematical expression 1. However, as described above, the terminal voltage V of the battery changes with the lapse of time of the discharge reaction, and even if the voltage is sampled at the same discharge current, the same voltage cannot be obtained if the reaction stage is different. Conversely, even if the current is sampled at the same voltage, the same current cannot be obtained if the reaction steps are different. That is, since the terminal voltage V and the discharge current I change depending on the stage of the chemical reaction of the battery itself, in order to accurately estimate the ability of the battery every moment, the reaction stage of the battery should be taken into consideration in the V-I characteristic. Need to sample.

FIG. 9 shows a terminal voltage V and a discharge current I during discharging.
5 is a diagram illustrating the sampling timing of FIG. Generally, a battery has a property that a change in voltage is delayed with respect to a change in current when the discharge current decreases. Therefore, when sampling the terminal voltage V and the discharge current I, a transient phenomenon between different reaction modes such as discharge reaction to charge reaction, discharge reaction to discharge stop, or equilibrium state to discharge reaction or charge reaction and discharge current decrease. In order to exclude the time, the rise of the discharge current is detected, and the terminal voltage V and the discharge current I when the discharge current increases are sampled. Further, in order to avoid unstable sampling of the terminal voltage V and the discharge current I in the transient region (the period T1 in which the transient voltages VX and VY in FIG. 3 occur), a predetermined time Δ from the rise of the discharge current is avoided.
After t, the terminal voltage V and the discharge current I are sampled.

Here, the discharge current rises when the current I and its rate of change dI / dt are both positive. The rising point of this discharge current is the starting point of the discharge reaction of the battery. In the example of FIG. 9, t1, t3, and t5 are the rising points of the discharge current, and the predetermined time Δ from those points.
At t2, t4 and t6 after t, the terminal voltages V1, V2 and V3 and the discharge currents I1, I2 and I3 are sampled. As a result, the measurement in the unstable transient region where the state of the battery changes rapidly can be avoided, and the terminal voltage V and the discharge current I of the battery in the stable diffusion region can be measured. When sampling the V-I characteristic, if there is a new rise of the discharge current within a predetermined time from the rise of the discharge current, the timing is restarted from that time point, and after the predetermined time, discharge with the terminal voltage V The current I is sampled.

By the way, if the sampling timing of the VI characteristic is set to only one point after a predetermined time from the rising of the discharge current, the following problems occur. FIG. 10 shows how the discharge current I and the terminal voltage V are sampled after a predetermined time Δt from the rise of the discharge current. In addition, FIG. 11 plots the sampling result on the VI graph,
It is a linear regression. Maximum discharge power P of this battery
D'is obtained by the method described above. The calculated maximum discharge power PD ′ is obtained based on the sampling result after the predetermined time Δt from the rising of the discharge current, and is therefore the maximum power that can be discharged for the predetermined time Δt.
However, when the maximum discharge power PD ′ is discharged for more than Δt time, the terminal voltage V becomes equal to or lower than the discharge end voltage Vmin during the discharge as shown by a straight line C in FIG.

That is, since the dischargeable electric power of the battery varies depending on the reaction stage, it is necessary to sample the VI data according to the required discharge time. Therefore, after the discharge current rises, the VI characteristic is sampled at a plurality of times. FIG. 12 shows how the discharge current I and the terminal voltage V are sampled after a predetermined time Δt1 and Δt2 from the rising of the discharge current. In addition, FIG. 13 plots the sampling result on the VI graph,
It is a linear regression. In FIG. 13, a straight line D is a regression line based on sampling data (x mark) after a predetermined time Δt1 from the rising of the discharge current, and a straight line E is sampling data (◯ mark) after a predetermined time Δt2 from the rising of the discharge current. It is a regression line based on this. In addition, the straight line F indicates that after a predetermined time Δt1 from the rising of the discharge current and Δ
It is a regression line based on the sampling data (both x and o) after t2. This regression line F gives the maximum discharge power P
By obtaining D ′, it is possible to obtain the average maximum power for various discharge forms with different discharge currents and discharge times.

FIG. 14 shows an example in which the VI characteristic is sampled at a plurality of points in a normal driving pattern of an electric vehicle. In this example, 1 from the rise of the discharge current
Sampling is performed after 2 seconds and 3 seconds. In addition, FIG. 15 is a graph obtained by plotting the sampling results on a VI graph and performing linear regression. In FIG. 15, a straight line G indicates sampling data (x mark) one second after the rise of the discharge current.
And a straight line H is a regression line based on sampling data (marked with a circle) 3 seconds after the rise of the discharge current. The straight line J is a regression line based on the sampling data (both x and ◯) 1 second and 3 seconds after the rise of the discharge current.

FIG. 16 shows the sampling data shown in FIGS. 14 and 15 based on the sampling timing Δt and the discharge current I.
It is classified by. 5 samples were collected in 1 second sampling and 3 samples in 3 seconds sampling.
Individual data were collected. However, as shown in FIG. 15, the sampling data after 1 second in which Δt is small is likely to concentrate in the low current region, and therefore the regression calculation accuracy based on these data is low. On the other hand, although the sampling data after 3 seconds in which Δt is large is distributed in a wide current range, the number of data tends to be small, and the regression calculation accuracy is also low.
However, the sampling data at a plurality of points after the rise of the discharge current, that is, after 1 second and 3 seconds, naturally has a large number of data, and since the current I and the voltage V are distributed in a wide range, the regression calculation accuracy is high. Become. Therefore, by calculating the maximum discharge power PD 'from the regression line J based on these data, it is possible to obtain the ideal average maximum power for various discharge forms with different discharge currents and discharge times. Further, if the accuracy of the regression calculation is improved based on the sampling data at a plurality of time points, the calculated regression line can be extended to the charging side to obtain an accurate maximum charging power PC ', as shown in FIG. .

In the sampling examples shown in FIGS. 12 to 15, the sampling is performed at two points after the rise of the discharge current, but the sampling timing is 3
There may be more than one. In addition, when sampling the VI characteristic, if there is a new rise of the discharge current within a predetermined time from the rise of the discharge current, timing is restarted from that time point, and after the predetermined time, discharge with the terminal voltage V The current I is sampled.

<< Method of Storing Sampling Data of VI Characteristics >> The data sampled at a plurality of timings described above are stocked by the following method. The range of the discharge current I is divided into a plurality of regions, and a predetermined number of stock memories are prepared for each region. For example, as shown in FIG. 17, the discharge current range is divided into five areas, and three stock memories are prepared for each area. Then, during the predetermined sampling time, the current in and the voltage vn are generated at the above-mentioned timing.
(N indicates the sampling order) and
Stock by classifying by current area. When the number of data in the current region reaches a predetermined number, the oldest data is erased and the latest data is stocked. For example, in the example of FIG. 17, when the data (i8, v8) is sampled and the data is included in the I2 to I3 area, the oldest data (i3, v3) in that area is erased and the latest data is used instead. The data (i8, v8) of is stored. According to this sampling data stocking method, since only a predetermined number of data sufficient for linear regression is stocked for each divided current region, a straight line of the VI characteristic based on the sampling data concentrated in a specific divided current region is stocked. Regression can be avoided, and accurate linear regression can be performed based on sampling data of a wide range of terminal voltage and discharge current, and accurate maximum charge / discharge power PD ', PC' can be estimated. In addition, since a predetermined number of sampling data are stocked for each divided current region, accurate linear regression can be performed using sampling data in a wide range within the discharge current range, and accurate maximum charge / discharge power PD ', PC 'Can be estimated, and there is no need to secure a huge memory capacity in the controller.

The V-I characteristic is sampled within a predetermined time period or at every predetermined discharge electricity amount, and the maximum discharge power PD 'and the maximum charge power PC' are calculated based on the data stocked by the above method. When the calculation of the maximum discharge power PD 'and the maximum charge power PC' is completed, all the sampling data stored in the memory are erased and the data is stocked again at the next sampling time. This allows
The terminal voltage V and the discharge current I in the latest state of the battery can be sampled, and the accurate maximum discharge power PD 'can be obtained based on the sampling data in the latest state of the battery.
And the maximum charging power PC 'can be calculated.

<< Charging / Discharging Power Calculation Process >> FIG. 18 is a flowchart showing the power calculation process of the controller 16. The controller 16 repeatedly executes this processing while the electric vehicle is in operation. In step 1, the voltage V and the current I are sampled at a plurality of points when the discharge current is increased, and the sampling data is stocked by the method described above. This sampling is performed within a predetermined time or every predetermined amount of discharged electricity. After the sampling is completed, in step 2, it is checked whether or not sampling data is stocked in three or more divided current regions in order to prevent regression calculation in a narrow current range and improve calculation accuracy. 3
If the data is stocked in more than one area, the process proceeds to step 3, and the VI characteristic is linearly regressed by the stock data. On the other hand, when the sampling data is not stocked in three or more divided current regions in step 2, the maximum charging / discharging powers PD 'and PC' are not calculated.
In step 4, the discharge cutoff voltage Vmi is calculated from the regression line.
The current IDmax at n is calculated, the maximum discharge power PD is calculated by the above equation 5, and the reduced current IDmax '
Based on the above, the maximum discharge power PI 'is calculated by Expression 10, and the smaller one is set as the final maximum discharge power PD'. Further, the current ICmax at the maximum allowable voltage Vmax is calculated, the maximum charging power PC is calculated by the above-mentioned formula 4, and the maximum discharge power is calculated based on the reduced current ICmax ′, and the smaller one is the final maximum discharge. Electric power P
Let's say C '.

<Output Limiting Process> Depending on the running pattern of the vehicle during power running, a running load exceeding the maximum discharge power PD 'may be applied. The maximum discharge power PD ′ is the power calculated based on the data sampled in a relatively short time from the rise of the discharge current, and can be said to be the power that can be discharged in a short time. For example, when a large current is discharged for a time longer than the sampling interval during power calculation, the maximum discharge power PD 'is exceeded and the terminal voltage V becomes equal to or lower than the discharge end voltage Vmin. Further, since the maximum discharge power PD 'decreases as the depth of discharge DOD increases, a time longer than the calculation interval of the maximum discharge power PD',
Similar results are obtained when a large current is discharged. It should be noted that if the V-I characteristic is sampled at a plurality of time points for a long time after a predetermined time from the rise of the discharge current and the maximum discharge power PD is calculated based on such a sampling result, the maximum discharge for a long time discharge Electric power PD '
Can be calculated. However, since discharge for a long time is rare, the number of data after a long time from the rise of the discharge current is small, and if the regression line is calculated including such data, the accuracy of the regression line decreases. There is a risk of causing it to be undesirable. On the other hand, the calculated maximum discharge power PD 'may include some error. When the maximum output power is required according to the running pattern of the vehicle and the discharge is performed up to the maximum discharge power PD ', the maximum discharge power P
If there is an error in D ', the terminal voltage V will fall below the discharge end voltage Vmin accordingly.

Therefore, as shown in FIG. 19, the terminal voltage V
When the voltage becomes equal to or lower than the reference voltage V1, the maximum discharge power PD 'is corrected by the limiting coefficient K to limit the output. This output limitation is repeated every predetermined time T2 until the terminal voltage V becomes equal to or higher than the reference voltage V1. In FIG. 19, it is assumed that discharge is started at time t1 and the discharge power exceeds the maximum discharge power PD '. At time t2 when the terminal voltage V becomes equal to or lower than the reference voltage V1, the limiting coefficient K is updated from 1 to k. At time t3 after the control delay time T1, the maximum discharge power is k · PD ′
Is limited to As a result, the discharge current I decreases and the terminal voltage V increases. At time t4, which is T2 hours after time t2, the terminal voltage V and the reference voltage V1 are compared, and if V <V1, the limiting coefficient K is updated to limit the output, and if V ≧ V1, the limiting coefficient K and The maximum discharge power PD 'is not changed. In this example, since it is V <V1 at time t4, the restriction coefficient K and k ^2. Time t5 after control delay time T1
, The maximum discharge power is limited to k ² · PD ′, and the discharge current I
Decreases and the terminal voltage V increases. Then, in time t6 T2 hours after the time t4, and it updates the restriction coefficient K k ³ because it is V <V1. At time t7 after the control time T1, the maximum discharge power is limited to k ³ · PD '. As a result, the discharge current I decreases and the terminal voltage V increases.
At time t8, which is T2 hours after time t6, the terminal voltage V is higher than the reference voltage V1, and therefore the limit coefficient K is not updated.

During the period from time t1 to time t8 immediately after the start of discharge, the discharge power overshoots and the maximum discharge power P
D'is frequently restricted every T2 hours. As described above, the overshoot of the discharge power immediately after the start of discharge is due to the calculation error of the maximum discharge power PD '. On the other hand, at time t9 that the steady state is detected again V <V1, restriction coefficient K is updated to k ^4.
At time t10 after the control delay time T1, the maximum discharge power P
D ′ is limited to k ⁴ · PD ′, the discharge current I decreases, and the terminal voltage V increases. The excess of the discharge power in the steady state is due to the discharge continuing for a long time as described above. When the mode is switched from the discharging mode to the regenerative charging mode at time t12, the terminal voltage V sharply increases, and the limiting coefficient K is reset to 1 at this time.

The reference voltage V1 is

## EQU11 ## Any value that satisfies V1 ≧ Vmin can be selected. The repetition time T2 of the output limiting process is longer than the control delay time T1, and the constant k is set to an optimal value such that the overshoot of the discharge power becomes 0 within a predetermined convergence time. The minimum value of the limiting coefficient K is set to 0.1 and values below that are considered to be 0.
For example, the convergence time is 3S. When k = 0.8,
When n = 10, K becomes smaller than 0.1. Therefore, if the repetition time T2 is selected to be 300 mS, the limiting coefficient K becomes 0 and the output power becomes 0 at 3S.

FIG. 20 is a flow chart showing the output limiting process. The controller 16 executes this process when the discharge is started. In step 11, the terminal voltage V is compared with the reference voltage V1, and if V <V1, the process proceeds to step 12, and if V ≧ V1, the process proceeds to step 18. When V ≧ V1, it is confirmed in step 18 whether the current I is negative, that is, whether the discharge mode is switched to the regenerative charge mode. If it remains in the discharge mode, the process returns to step 11, and if it switches to the regenerative charging mode, the process proceeds to step 17. In step 17, 0 is set to the variable n indicating the output limit number, and the process is ended. On the other hand, when V <V1, step 1
At 2, the variable n indicating the output limit number is incremented.
Note that the initial value of the variable n is 0. In step 13, the limiting coefficient K is set. At the time of the first output limitation, since n = 1, the limitation coefficient K is k. In step 14, the calculated maximum discharge power PD 'is multiplied by the limiting coefficient K to correct. In step 15, the timer is set to T2 and started. This T2 time is the repetition time of the output limiting process described in FIG. In step 16,
It is confirmed whether or not the current I is negative, that is, whether the discharge mode is switched to the regenerative charging mode. If the current I is switched to the regenerative charging mode, the process proceeds to step 17, the variable n is set to 0, and the process ends. On the other hand, when the discharge mode is continuing, the routine proceeds to step 19, where the timer expires and T
Check to see if 2 hours have passed. When the time T2 has elapsed, the process returns to step 11 and the above process is repeated.

<< Regeneration Restriction Process >> Similar to power running, regenerative power exceeding the maximum charging power PC 'may be generated depending on the running pattern of the vehicle during regenerative charging. The maximum charging power PC ′ is the power calculated based on the data sampled for a relatively short time from the rise of the discharge current, and can be said to be the power that can be regeneratively charged in a short time. For example, if regenerative charging with a large current is performed for a time longer than the sampling interval during power calculation, the maximum charging power PC 'will be exceeded and the terminal voltage V will exceed the maximum allowable voltage Vmax. Further, the calculated maximum charging power PC 'may include some errors. Maximum regenerative braking force is required according to the running pattern of the vehicle, and when charging is performed with the maximum charging power PC ', if there is an error in the maximum charging power PC', the terminal voltage V exceeds the maximum allowable voltage Vmax. Will end up.

Therefore, as shown in FIG. 21, the terminal voltage V
Exceeds the reference voltage V2, the maximum charging power PC 'is corrected by the limiting coefficient K to limit the regeneration. This regenerative limitation is repeated every predetermined time T2, and is performed until the terminal voltage V becomes equal to or lower than the reference voltage V2. In FIG. 21, time t1
It is assumed that the regenerative charging is started and the charging power exceeds the maximum charging power PC '. At time t2 when the terminal voltage V exceeds the reference voltage V2, the limiting coefficient K is updated from 1 to k. At time t3 after the control delay time T1, the maximum charging power PC ′ is k · PC ′.
Is limited to As a result, the charging current I and the terminal voltage V
Decrease. At time t4, which is T2 hours after time t2, the terminal voltage V is compared with the reference voltage V2, and if V> V2, the limiting coefficient K is updated to limit the output, and if V ≦ V2, the limiting coefficient K and Do not change the maximum charging power PC '.
In this example, because there in at time t4 V> V2, the restriction coefficient K and k ^2. At time t5 after the control delay time T1, the maximum charging power is limited to k ² · PC ', and the charging current I and the terminal voltage V decrease. Next, at time t6, which is T2 hours after time t4, since V> V2, the limiting coefficient K
To k ³ . At time t7 after the delay time T1, the maximum charging power is limited to k ³ · PC ′, and the discharge current I and the terminal voltage B decrease. Time t8, which is T2 hours after time t6
Then, the terminal voltage V is lower than the reference voltage V2, and therefore the limiting coefficient K is not updated.

During the period from time t1 to time t8 immediately after the start of regenerative charging, the charging power overshoots and the maximum charging power PC 'is frequently limited every T2 hours. As described above, the overshoot of the charging power immediately after the start of the regenerative charging is due to the calculation error of the maximum charging power PC '. On the other hand, at time t9 that the steady state is again V> V2 is detected, restriction coefficient K is updated to k ^4. At time t10 after the control delay time T1, the maximum charging power is limited to k ⁴ · PC ′, and the charging current I and the terminal voltage V decrease. The excess of the charging power in the steady state is due to the charging being continued for a long time as described above. When the regenerative charging mode is switched to the discharging mode at time t12, the terminal voltage V sharply decreases,
At this point, the limiting coefficient K is reset to 1.

The reference voltage V2 is

(12) Any value that satisfies V2 ≦ Vmax can be selected. Further, the repetition time T2 of the regeneration limiting process is set to be longer than the control delay time T1, and the constant k is set to an optimum value at which the overshoot of the charging power becomes 0 within a predetermined convergence time. The minimum value of the limiting coefficient K is set to 0.1 and values below that are considered to be 0.
For example, the convergence time is 3S. When k = 0.8, K becomes smaller than 0.1 when n = 10. Therefore, if the repetition time T2 is selected to be 300 mS, the limiting coefficient K becomes 0 and the regenerative power becomes 0 at 3S. In the output limiting process and the regeneration limiting process described above, an example is shown in which the limiting process is performed at the same time interval T2, but the output limiting process and the regeneration limit may be performed at different time intervals. .

FIG. 22 is a flow chart showing the regeneration limiting process. The controller 16 executes this processing when the regenerative charging is started. In step 21, the terminal voltage V is compared with the reference voltage V2, and if V> V2, step 2
2. If V≤V2, proceed to step 28. V ≦
When it is V2, it is confirmed in step 28 whether the current I is positive, that is, whether the regenerative charging mode is switched to the discharging mode. If the regenerative charging mode remains, step 21
If the discharge mode is switched back to, the process proceeds to step 27. In step 27, 0 is set in the variable n indicating the number of times regeneration is limited.
Is set and the process ends. On the other hand, when V> V2, the variable n indicating the number of times of regeneration limitation is incremented in step 22. Note that the initial value of the variable n is 0. Step 2
The limit coefficient K is set at 3. At the time of the first output limitation, since n = 1, the limitation coefficient K is k. Step 2
In step 4, the calculated maximum charging power PC 'is multiplied by the limiting coefficient K to correct the maximum charging power PC'. In step 25, the timer is set to T2 and started. This T2 time is the repetition time of the regeneration limiting process described in FIG. In step 26, it is confirmed whether or not the current I is negative, that is, whether the regenerative charging mode is switched to the discharging mode. If the current is switched to the discharging mode, the process proceeds to step 27, 0 is set to the variable n, and the process is ended. On the other hand, when the regenerative charging mode continues, the routine proceeds to step 29, where it is confirmed whether the timer has timed up and T2 time has elapsed. When T2 time has elapsed, the process returns to step 21 and the above process is repeated.

As shown in FIG. 2, the DOD is 60%.
If it exceeds, the internal resistance R during discharging and the internal resistance R during charging
, The maximum charging power PC 'calculated includes a large error. However, when the DOD exceeds 60%, since the true maximum charging power of the battery is sufficiently larger than the maximum power regenerated from the inverter 12, even if there is a large error in the calculated value PC ′ of the maximum charging power, there is a problem. do not become.

-Modification of Embodiment of the Invention- In the above-described embodiment, the battery 1 is provided by the voltage sensor 14.
An example is shown in which the terminal voltage V at both ends of 1 is measured and power calculation, output limitation, and regeneration limitation are performed. Generally, an electric vehicle uses an assembled battery in which a plurality of unit cells are connected in series. Therefore, the voltage across each unit cell (hereinafter referred to as the cell voltage) is measured, and power calculation and output limitation are performed based on the cell voltage. And regenerative restriction may be performed. FIG. 23 shows a configuration of a modified example in which the charge / discharge power is calculated based on the cell voltage, and output limitation and regeneration limitation are performed. In the battery 11A, n unit cells 111 to 11n are connected in series, and voltage sensors 141 to 14n are connected in parallel to each unit cell. The outputs of these voltage sensors 141 to 14n are connected to the controller 16A. Other configurations are the same as those shown in FIG.

In calculating the maximum charge / discharge power PD 'and PC', the detected voltages of the voltage sensors 141 to 14n are added to obtain the terminal voltage V across the battery 11A, and the maximum charge / discharge power PD 'is calculated by the above method. , PC ′ is calculated. In the output limiting process, the reference voltage V1 ′ of the single cell corresponding to the above-mentioned reference voltage V1 is set, and the voltage sensors 141 to 14 are set.
The output is limited by the method described above while comparing the minimum cell voltage detected by n with the reference voltage V1 '. Further, in the regeneration limiting process, the reference voltage V2 ′ of the single cell corresponding to the above-mentioned reference voltage V2 is set, and the voltage sensor 141 is set.
Maximum cell voltage and reference voltage V2 'detected at ~ 14n
Regeneration is restricted by the method described above while comparing

-Other Modifications of the Embodiment of the Invention- In the modification shown in FIG. 23 described above, an example is shown in which the maximum charge / discharge power is calculated and the output / regeneration is limited based on the cell voltage and current of the battery. However, another modification will be described in which the maximum charge / discharge power is calculated and the output / regeneration is limited based on the cell voltage, terminal voltage and current of the battery. In this modified example, FIG.
As shown in FIG. 4, the voltage sensor 14 for measuring the terminal voltage V of the battery 11A is added to the configuration of the modification shown in FIG. When calculating the maximum charging / discharging powers PD 'and PC', the maximum charging / discharging powers PD 'and PC' are calculated by the method described above based on the terminal voltage V and the discharge current I measured by the terminal voltage sensor 14. Further, in the output limiting process, the reference voltage V1 ′ of the single cell corresponding to the reference voltage V1 is set, and the minimum cell voltage detected by the cell voltage sensors 141 to 14n is compared with the reference voltage V1 ′. Output limitation by the method. In the regeneration limiting process, the reference voltage V2 'of the single cell corresponding to the reference voltage V2 is set,
Regeneration is limited by the above-described method while comparing the maximum cell voltage detected by the cell voltage sensors 141 to 14n with the reference voltage V2 '.

After calculating the maximum charge / discharge power PD ', PC' based on the terminal voltage measured by the terminal voltage sensor 14, the minimum cell voltage detected by the cell voltage sensors 141 to 14n and the terminal voltage sensor 14 are detected. Either of the terminal voltages measured by the reference voltage (V1 or V
1 ') or less, output is limited and the terminal voltage or maximum cell voltage is the reference voltage (V2 or V2
2 ') When it is above, you may make it possible to limit the regeneration.

In the configuration of the above embodiment, the voltage sensor 14 is the voltage measuring means, the current sensor 15 is the current measuring means, and the controller 16 is the current estimating means, the first calculating means, the second calculating means and the power. Each of the control means is configured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electric vehicle according to an embodiment.

FIG. 2 is a diagram showing the relationship between the depth of discharge (DOD) of a battery and the internal resistance.

FIG. 3 is a diagram showing changes in the terminal voltage of the battery when discharged at a constant current.

FIG. 4 is a diagram showing a regression line based on sampling data of terminal voltage and discharge current during discharging.

FIG. 5 is a diagram showing V-I characteristics when the maximum discharge power is calculated without reducing the maximum discharge current.

FIG. 6 is a diagram showing a maximum power characteristic when a maximum discharge power is calculated without reducing the maximum discharge current.

FIG. 7 is a diagram showing VI characteristics when a maximum discharge current is reduced and a maximum discharge power is calculated.

FIG. 8 is a diagram showing a maximum power characteristic when the maximum discharge current is reduced and the maximum discharge power is calculated.

FIG. 9 is a diagram illustrating sampling timings of a terminal voltage and a discharging current during discharging.

FIG. 10 is a diagram showing a case where a discharge current and a terminal voltage are sampled after a predetermined time has elapsed from the rise of the discharge current.

FIG. 11 shows the sampling data shown in FIG.
The figure which plotted on the graph and linearly regressed.

FIG. 12: A predetermined time Δt1 from the rising of the discharge current
The figure which shows the case where discharge current and terminal voltage are sampled after and after (DELTA) t2.

FIG. 13 shows the sampling data shown in FIG.
The figure which plotted on the graph and linearly regressed.

FIG. 14 is a diagram showing an example in which VI characteristics are sampled at a plurality of points in a normal traveling pattern of an electric vehicle.

FIG. 15 shows the sampling data shown in FIG.
The figure which plotted on the graph and linearly regressed.

16 is a diagram in which the sampling data shown in FIG. 14 is classified according to sampling timing and discharge current.

FIG. 17 is a diagram illustrating a method of stocking sampling data.

FIG. 18 is a flowchart showing power calculation processing.

FIG. 19 is a diagram illustrating output restriction.

FIG. 20 is a flowchart showing output restriction processing.

FIG. 21 is a diagram showing a regeneration restriction process.

FIG. 22 is a flowchart showing a regeneration limiting process.

FIG. 23 is a diagram showing a configuration of a modified example in which cell voltage and current of a battery are measured, maximum charge / discharge power is calculated, and output limitation and regeneration limitation are performed.

FIG. 24 is a diagram showing the configuration of another modified example in which the cell voltage, the terminal voltage, and the current of the battery are measured, the maximum charge / discharge power is calculated, and the output limitation and the regeneration limitation are performed.

[Explanation of symbols]

 11, 11A Battery 12 Inverter 13 Motor 14, 141-14n Voltage sensor 15 Current sensor 16, 16A, 16B Controller 111-11n Single cell

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H02J 7/10 H02J 7/10 H

Claims (5)

[Claims] 1. A voltage measuring unit for measuring a voltage of a battery; a current measuring unit for measuring a current flowing through the battery; a voltage and a current when the discharge current increases measured by the voltage measuring unit and the current measuring unit. Current estimating means for estimating a discharge current of the battery at a first voltage, first calculating means for calculating a discharge power of the battery based on the discharge current at the first voltage, and Second calculating means for calculating discharge power of the battery based on a predetermined discharge current smaller than discharge current at a voltage of 1; and discharge power of the battery is calculated by the first and second calculating means. And an electric power control unit for limiting the electric power to a small value. 2. The electric power control apparatus for an electric vehicle according to claim 1, wherein the current estimating means is based on the voltage and current when the discharge current increases measured by the voltage measuring means and the current measuring means, Estimating a charging current at a second voltage of the battery, the first computing means computing the charging power of the battery based on the charging current at the second voltage, and the second computing means: The charging power of the battery is calculated based on a predetermined charging current smaller than the charging current at the second voltage, and the power control unit calculates the charging power of the battery as the first charging current.
And an electric power control apparatus for an electric vehicle, wherein the electric power is limited to a small value of the electric power calculated by the second calculating means. 3. The electric power control apparatus for an electric vehicle according to claim 1, wherein the predetermined discharge current and the predetermined charge current are determined based on a maximum rated current of an electric motor of the electric vehicle. Characteristic electric power control device for electric vehicles. 4. The electric power control device for an electric vehicle according to claim 1, wherein the first voltage is a discharge end voltage of the battery. apparatus. 5. The electric power control apparatus for an electric vehicle according to claim 2, wherein the second voltage is a maximum allowable voltage of the battery. apparatus.