JP3503195B2 - Regenerative controller for electric vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative control device for an electric vehicle which controls a regenerative amount of an electric vehicle driven by a secondary battery, that is, a regenerative charge amount during deceleration (including braking).

[0002]

2. Description of the Related Art As a conventional regeneration control device for an electric vehicle, for example, there is one described in "Nissan FEV Pamphlet". In the above-mentioned conventional example, when the accelerator pedal is off, or when the accelerator pedal is off and the brake is operated, that is, at the time of deceleration or braking, a device for performing regenerative charging of a secondary battery using a driving motor as a generator. Have been described. In the above-mentioned device, the amount of regeneration is constant, and regenerative charging is stopped when the battery is fully charged.

[0003]

As described above, in the conventional device, the regenerative charge at the time of full charge is stopped in order to prevent overcharge, but otherwise, at the time of deceleration or Since a fixed amount of regenerative charging is always performed during braking, there is a problem that the life of the battery may be adversely affected. The details will be described below. The discharge capacity (the amount of electricity that can be discharged) of a secondary battery decreases each time charging and discharging are repeated.However, in the case of an assembled battery in which a plurality of secondary batteries are connected in series or series-parallel, the discharge capacity The degree of decrease differs for each battery. Therefore, DOD (depth of discharge: 100% at full discharge, 0 at full charge)
%) The discharge capacity from 0% varies from battery to battery,
As a result, the discharge capacity of the assembled battery is reduced. That is, at the time of discharging, a battery whose discharge capacity has become small is quickly discharged and becomes an over-discharged state, and this over-discharged battery becomes a load of other batteries, and all the batteries become DOD.
The voltage drops before it reaches 100%, and the battery pack ends discharging. On the other hand, when charging, the battery that did not reach 100% DOD when discharged first
The voltage rises and the charging ends, but the battery that has been over-discharged at the time of discharging ends charging without DOD 0%, so the difference in DOD widens and the difference in the discharge capacity of each battery Also spreads. Therefore, when charging and discharging are repeated, the battery with a small discharge capacity always becomes insufficiently charged, and the discharge capacity of the entire assembled battery decreases, and the above battery is repeatedly over-discharged and insufficiently charged, so that the battery life is also shortened. It deteriorates. As described above, if the regenerative charge amount is kept constant, the discharge capacity of a specific battery in the battery pack will decrease significantly, the discharge capacity of the battery pack as a whole will decrease, and regeneration will always occur during deceleration. When the battery is charged, there is a problem that the life of the battery is deteriorated because the number of times of charging increases.

The present invention has been made to solve the above-mentioned problems of the prior art, and is an electric vehicle capable of reducing deterioration of battery life and compensating for reduction of discharge capacity as an assembled battery. An object of the present invention is to provide a regeneration control device for use.

[0005]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, in the invention according to claim 1, the assembled battery in which a plurality of secondary batteries are connected in series or in series-parallel and the assembled battery is charged by regenerative power generation during deceleration (including braking) of the electric vehicle Regenerative charging means, voltage detection means for detecting the voltage of each battery constituting the assembled battery, based on the detection result of the voltage detection means,
The maximum width of variation of each battery voltage during charging, that is, the difference between the voltage value of the battery having the highest voltage and the voltage value of the battery having the lowest voltage is detected, and the regeneration amount in the regenerative charging means is changed according to the maximum width. and a control means for, on SL control unit only when the upper Symbol maximum width of the first predetermined value or more to perform the regenerative charging and increase the amount of regeneration according to the maximum width of the variation is large It is controlled to do so.

According to the invention of claim 2 ,
The voltage detection means, when charging by a normal charging device that is not regenerative charging is completed (for example, immediately before completion, the same applies hereinafter),
Detecting the voltage of each battery, the control means detects the maximum width of the variation according to each battery voltage at the end of charging, stores the regenerative amount according to that value, and stores the next regenerative charging. At times, the regenerative amount in the regenerative charging means is controlled according to the stored value. Note that this configuration corresponds to, for example, a first embodiment (flowchart in FIG. 4) described later.

Further, in the invention described in claim 3 ,
The voltage detection means detects the voltage of each battery at the end of charging by a normal charging device and at the end of regenerative charging,
The control means detects the maximum width of the variation according to each battery voltage at the end of the charging, stores the regenerative amount corresponding to the value, and stores the regenerative amount at the next regenerative charging. The regenerative amount in the regenerative charging means is controlled according to the value that has been set. Note that the above-described configuration is, for example, the second
Of the embodiment (flow chart of FIG. 5).

Further, in the invention described in claim 4 ,
The voltage detection means detects the voltage of each battery at the end of charging by a normal charging device and at the end of regenerative charging,
The control means detects the maximum width of the variation according to each battery voltage at the end of the charging, stores the regenerative amount corresponding to the value, and stores the regenerative amount at the next regenerative charging. The regenerative amount in the regenerative charging means is controlled according to the value that has been exceeded, and when the maximum width of the variation is equal to or greater than the second predetermined value, the charging end condition is reached at the next charging by the normal charging device. However, the charging is not terminated but is controlled to be performed uniformly. The above configuration corresponds to, for example, a third embodiment described below.

[0009]

In a battery pack in which a plurality of secondary batteries are connected in series, the maximum width of variation in each battery voltage, that is, the difference ΔV between the voltage value of the battery having the highest voltage and the voltage value of the battery having the lowest voltage.
And the discharge capacity of the assembled battery have a relationship as shown in FIG. That is, the larger the voltage difference ΔV, the smaller the discharge capacity. As described above, the large voltage difference ΔV indicates that the discharge capacity of the assembled battery has decreased. In addition, since the secondary battery generally deteriorates according to the number of times of charging and discharging, the life of the secondary battery becomes longer if it is not necessary, that is, if the discharge capacity is large, it is not charged as much as possible. Therefore , as described in claim 1, when the maximum width of the variation of the battery voltage is smaller than the first predetermined value, that is, when the state of each battery is uniform and the charging is performed well, the regenerative charging is performed. If the maximum range of variation is large without performing the above, that is, if there is a battery with a reduced discharge capacity, the regenerative charge amount is increased according to the maximum range, and the reduced battery is also often charged. By doing so, the difference with others is reduced. In this way, by increasing the charge amount of the battery with reduced discharge capacity and reducing the difference from other batteries, the degree of overall decrease can be reduced and the discharge capacity can be increased. Can be stretched.
It should be noted that if the regenerative charge amount is increased, an effect similar to that of the uniform charge (described later in detail) can be obtained, so that the charge amount of the battery having the reduced discharge capacity can be recovered. Further, when the maximum width of variation is small, regenerative charging is not performed, so that the number of times of charging can be reduced and the battery life can be improved. FIG. 3 is a characteristic diagram showing the relationship between the regeneration amount and the change rate of the voltage difference ΔV. The rate of change of the voltage difference ΔV means the rate of change between the voltage difference ΔV during the previous charging and the value during the current charging. As shown in FIG. 3, when the amount of regeneration is large, the rate of change of the voltage difference ΔV becomes small, and it can be seen that the batteries forming the assembled battery can be charged uniformly.

Further, the invention of claim 2 detects the voltage of each battery at the end of charging (for example, immediately before completion, the same applies hereinafter) at the end of charging by a normal charging device that is not regenerative charging, and responds to the maximum variation width. The regenerative amount is obtained and stored, and at the time of the next regenerative charging, the regenerative amount in the regenerative charging means is controlled according to the stored value. With this configuration, it is possible to immediately charge the battery with a regeneration amount suitable for the state of the battery during regeneration. Further, the invention of claim 3 detects the voltage of each battery at the end of regenerative charging as well as at the end of charging by the normal charging device, and calculates and stores the regenerative amount in the same manner as above. is there. Claim
In the case of 2, the regenerative amount does not change until normal charging is performed, but in claim 3 , the regenerative amount is calculated even during regenerative charging, so that control suitable for the state of the battery can be performed. Further, in the invention of claim 4 , when the maximum width of variation is very large, that is, when there is a battery whose discharge capacity is significantly reduced, the charging end condition (for example, voltage When the battery reaches a predetermined value), the charging is not terminated even when the battery reaches a predetermined value, and the uniform charging is performed. This equal charge is the rated voltage of 10
This is a method of applying a voltage of ~ 15% increase and charging it with a current of about (1/20) C (C is a rated current) for about 2 to 5 hours, which causes a large decrease in capacity (low voltage battery). Can also be charged, and the state of charge of each battery can be equalized.

[0011]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a charging device installed outside the vehicle, for example, installed at home or at a charging station. 2 and 3 are connectors for connecting the charging device 1 and the on-vehicle assembled battery 8, 4 is an accelerator sensor for detecting the amount of depression of the accelerator pedal, 5 is a brake sensor for detecting the amount of operation of the brake, and 6 is for the assembled battery 8. A voltage sensor that detects the voltage of each battery, 7 is a current sensor that detects current, 8 is an assembled battery in which a plurality of batteries are connected in series, 9 is a controller, 10 is a driving motor, and power is generated during regeneration. Operates as a machine. 1
Reference numeral 1 is an inverter that converts the DC output of the assembled battery 8 into three-phase AC, 12 is a tire, and 13 is a drive device (for example, a gear) that connects the motor 10 and the tire 12. In addition, in this embodiment, the case where a plurality of batteries are connected in series as the assembled battery 8 is illustrated, but the batteries may be connected in series and parallel. In the electric vehicle shown in FIG. 1, the DC power of the assembled battery 8 is converted into AC power by the inverter 11, the motor 10 is driven by the power, and the tire 12 is rotated via the drive device 13 to travel. Further, the control device 9 detects when the vehicle is decelerating (including braking) from the signals of the accelerator sensor 4 and the brake sensor 5, and operates the motor 10 as a generator to perform regenerative charging (details will be described later). Further, when charging the assembled battery 8 from the charging device 1 provided outside the vehicle, the charging control described later is also performed.

Next, the operation will be described. FIG. 4 is a flowchart showing a first embodiment of control at the time of charging.

In FIG. 4, first, in step S1, it is determined whether the charging device 1 outside the vehicle performs normal charging or regenerative charging. The regenerative charging is performed, for example, when it is detected from the signals of the accelerator sensor 4 and the brake sensor 5 that the accelerator is off and the brake is on (during deceleration). When it is determined in step S1 that the charging is normal and the charging is started, it is then determined in step S2 whether or not the charging is ended. This judgment is made based on the rated current, voltage value, etc. of the battery. For example, charging is started at a constant current of (1/3) C, switching to constant voltage charging from the time when the voltage value reaches the rated value, and 4 hours after that,
Alternatively, after switching to the constant voltage charging, it is determined that the charging is completed one hour after the current value becomes 1 A or less. The values detected by the voltage sensor 6 and the current sensor 7 are used as the above voltage value and current value. Next, in step S3, each battery voltage of the assembled battery 8 immediately before the end of charging is detected and stored. It is sufficient to store about 10 sets of this data over time, for example, when one set of data obtained by measuring all the voltages of the respective batteries is used.
Next, in step S4, the maximum width of variation in each battery voltage, that is, the voltage difference ΔV between the voltage value of the battery having the highest voltage and the voltage value of the battery having the lowest voltage is calculated, and in step S5,
Calculate the regeneration amount τ. This regeneration amount τ is calculated as a function of the difference between the voltage difference ΔV at that time and a predetermined value α (for example, the voltage difference α corresponding to the target discharge capacity C shown in FIG. 2). In this case, when the value of ΔV is small and (ΔV−α) ≦ 0, that is, when ΔV ≦ α, regenerative charging is not performed, and the value of the regeneration amount τ has a large difference between ΔV and α. Set to a large value. For example, the regeneration amount τ is set to be a value proportional to the difference between ΔV and α. Next, step S6
Then, the calculated regenerative amount τ is stored in the memory for use at the next regenerative operation. On the other hand, when it is determined in step S1 that "regenerative charging" is performed, the regenerative amount τ stored in the memory is read in step S7. Then, in step S8, a regenerative torque command calculation is performed. In this calculation, the ratio between the regenerative braking force by the regenerative power generation and the braking force by the braking device is calculated based on the regenerative amount τ and the brake pedal force T, and the regenerative torque is calculated accordingly. Then, in step S9, regenerative charging according to the regenerative torque is started. Further, in step S10, it is determined whether or not the regenerative charging is ended. Note that this determination is determined to be the end of regenerative charging when the vehicle is in a re-accelerated state after braking (when the accelerator pedal is depressed) or when the brake pedal is released.
With the above configuration, the regenerative amount τ can be calculated and stored according to the voltage value measured during normal charging, and the value can be read out during the next regenerative charging to perform regenerative charging control.

Next, FIG. 5 shows a second control of charging.
3 is a flowchart showing an example of the above. In FIG. 5, when it is determined in step S10 that the regenerative charging is completed,
Going to step S3, each battery voltage immediately before the end of regenerative charging is detected and stored. The following control is the same as in the case of FIG. According to the above configuration, the regenerative amount is calculated even during regenerative charging, so that control suitable for the state of the battery can be performed.

Next, a third embodiment of charge control will be described. Based on the battery voltage values detected and stored in step S3 in the flowchart of FIG. 4 or 5, the maximum width ΔV of the variation obtained in step S4 is the second value.
Is equal to or more than the predetermined value, that is, when the variations in the battery voltages are extremely large, the charging is not terminated even if the charging termination condition is reached in step S2 at the next normal charging, and a new equal charging is performed. Control it to be performed. This equal charging is a voltage of 10 to 15% higher than the rated voltage, and a current of about (1/20) C (C is the rated current) is 2 to
This is a method of charging for about 5 hours, whereby a battery with a large decrease in capacity (battery with a low voltage) can be charged, and the charging state of each battery can be equalized.

Next, the difference between the charging control method described in JP-A-51-85437 and the present invention will be described. In the above-mentioned publicly known example, each battery voltage which constitutes the assembled battery is measured, and those values are compared with a predetermined reference voltage range (between the upper limit value and the lower limit value centering on the reference value) and deviated from the reference range. The charging voltage and charging method are controlled according to the number of batteries. On the other hand, in the present invention, the regenerative charging is performed according to the maximum width of the variations in the voltages of the batteries forming the assembled battery, that is, the difference between the voltage value of the battery having the highest voltage and the voltage value of the lowest battery. It controls whether to perform or not and the amount of regeneration.

FIG. 6 and FIG. 7 are diagrams showing examples of variations in battery voltage in an assembled battery in which eight batteries are connected in series. In the case of the above-mentioned publicly known example, as shown in FIG. 6, when only one battery (No. 5) largely deviates, it is judged that only one battery deviates from the reference. There is no big change in. In the case of the present invention, the voltage difference is used as a reference for determination, so in the case of FIG. 6, the regenerative charge amount is increased or control is performed so as to perform uniform charge at the next normal charge. Further, as shown in FIG. 7, when there are a large number of batteries that are slightly out of the reference range, the charge amount and the like are significantly changed in the above-mentioned known example, but in the present invention, when the voltage difference is small, the regenerative charge amount Is a small value.
In the assembled battery, the discharge capacity of the entire assembled battery gradually decreases when charging and discharging are repeated, but at this time, the voltage of each battery does not vary as a whole, but a particular one battery drops in particular. . In other words, in the case of the assembled battery, the degree of decrease in discharge capacity differs depending on the battery, so during discharge, a battery with a reduced discharge capacity is quickly discharged and overdischarged, resulting in overdischarge. The battery becomes a load of other batteries, and the voltage drops before all the batteries reach DOD 100%, and the assembled battery ends the discharge. On the other hand, when charging, discharging 100% DOD
The battery that did not become DOD reaches 0% first and the voltage rises, and charging ends, but the battery that is over-discharged at the time of discharging ends charging without DOD 0%, so the difference in DOD Spread, and the difference in discharge capacity of each battery also spreads. Therefore, when charging and discharging are repeated, the specific battery having a small discharge capacity is always insufficiently charged, and the difference from other batteries becomes large. As described above, in the assembled battery, the voltage value of the specific battery tends to change more drastically than that of the other batteries, so rather than controlling by the number of batteries deviating from the reference range as in the above-mentioned known example, As in the present invention, the control based on the voltage difference enables the charge control suitable for the characteristics of the assembled battery.

[0018]

As described above, according to the present invention, the regenerative amount is changed according to the maximum width of the variation in the voltage of each battery forming the assembled battery.
It is possible to recover the amount of charge of a battery with reduced discharge capacity and reduce the number of times of charging, so it is possible to compensate for the decrease in discharge capacity as an assembled battery and improve the life of the battery. The effect of, is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the maximum voltage difference ΔV and the discharge capacity of each battery included in the assembled battery.

FIG. 3 is a characteristic diagram showing a relationship between a regeneration amount and a change rate of a maximum voltage difference ΔV.

FIG. 4 is a flowchart showing a first embodiment of charging control.

FIG. 5 is a flowchart showing a second embodiment of charging control.

FIG. 6 is a characteristic diagram showing a voltage variation state in the assembled battery.

FIG. 7 is a characteristic diagram showing a voltage variation state in the assembled battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Charging device installed outside the vehicle 8 ... Batteries 2, 3 ... Connector 9 ... Control device 4 ... Accelerator sensor 10 ... Driving motor 5 ... Brake sensor 11 ... Inverter 6 ... Voltage sensor 12 ... Tire 7 ... Current sensor 13 ... Drive device

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Claims (4)

(57) [Claims] 1. An assembled battery in which a plurality of secondary batteries are connected in series or series-parallel, regenerative charging means for charging the assembled battery by regenerative power generation during deceleration of an electric vehicle, and each battery constituting the assembled battery. Based on the detection result of the voltage detection means for detecting the voltage of, the maximum width of the variation of each battery voltage at the time of charging, that is, the voltage value of the battery with the highest voltage and the voltage value of the lowest battery A control unit that detects a difference and changes the amount of regeneration in the regenerative charging unit according to the maximum width, the control unit being configured to control the maximum width to be equal to or larger than a first predetermined value.
Regenerative charging only, and the maximum width above is large
It controls to increase the amount of regeneration as
There is a regenerative control device for an electric vehicle. 2. The voltage detecting means detects the voltage of each battery at the end of charging by a normal charging device that is not regenerative charging, and the control means sets the voltage according to each battery voltage at the end of charging. The maximum amount of variation is detected, the regenerative amount corresponding to the value is stored, and at the time of the next regenerative charging, the regenerative amount in the regenerative charging means is controlled according to the stored value. The regenerative control device for an electric vehicle according to claim 1, wherein: 3. The voltage detecting means detects the voltage of each battery at the end of charging by an ordinary charging device that is not regenerative charging and at the end of regenerative charging, and the control means detects each voltage at the end of charging. The maximum width of the variation is detected according to the battery voltage, and the regeneration amount according to the value is stored, and at the time of the next regenerative charging, the regeneration by the regenerative charging means is performed according to the stored value. The regenerative control device for an electric vehicle according to claim 1, wherein the regenerative control device controls an amount. 4. The voltage detecting means detects the voltage of each battery at the end of charging by an ordinary charging device other than regenerative charging and at the end of regenerative charging, and the control means detects each voltage at the end of charging. The maximum width of the variation is detected according to the battery voltage, and the regeneration amount according to the value is stored, and at the time of the next regenerative charging, the regeneration by the regenerative charging means is performed according to the stored value. When the amount is controlled and the maximum width of the variation is equal to or larger than the second predetermined value, the charging is not terminated even if the charging termination condition is reached at the next charging by the normal charging device, and the uniform charging is performed. The control is performed so as to perform.
The regenerative control device for an electric vehicle according to 1 .