JP2000152420A - Control method for charging battery in hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for charging battery in a hybrid vehicle for enlarging the usage range of SOC of a battery and efficiently using the battery. SOLUTION: An early-stage target of a charged state of a battery is set and a mean charging/discharging amount determined by the running state of a vehicle for the battery is calculated, and an SOC corrected value is sought from this mean charging/discharging amount through a prescribed algorithm. The early-stage target value of SOC is compensated by the SOC corrected value to calculate a target SOC according to the running state. An engine, requiring power Pe for requiring the engine, is calculated from the target SOC and an actual SOC of the battery. In addition, the charging of battery by the engine power and the discharging of battery by the motor can be determined, and the control is carried out, so that the SOC of the battery is made matching with the target SOC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for controlling a state of charge of a battery in a hybrid vehicle.

[0002]

2. Description of the Related Art A hybrid vehicle is equipped with a battery serving as a power supply for supplying electric power for driving a motor. This battery has an allowable range of state of charge (SOC), and it is necessary to control so that the SOC is maintained within this range. Conventionally, control has been performed while keeping the target SOC, which is the target of SOC control, substantially constant.

[0003]

However, the conventional S
In the OC control method, for example, it is necessary to charge the battery with electric power regenerated by brake control during a downhill, so the above-described target value of the SOC is set to a lower value in advance.
For this reason, the battery SO on a flat ground where power regeneration is not performed
There is a problem that the use range of C is limited, and it is not possible to sufficiently improve the fuel efficiency by using the power of the motor for running the hybrid vehicle.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to increase the SOC of a battery and to improve the state of charge of the battery in a hybrid vehicle in which the battery can be used efficiently. It is to provide a control method.

[0005]

To achieve the above object, the present invention relates to a method for controlling the state of charge of a battery in a hybrid vehicle, comprising the steps of: setting an initial target value of the state of charge (SOC) of the battery; An average charge / discharge amount is obtained from the charge amount and the discharge amount of the battery, an SOC correction amount for correcting an initial target value is obtained based on the average charge / discharge amount, and an initial target value is corrected based on the SOC correction amount to obtain a target SOC. , A corrected power which is a charge amount of the battery by the engine power or a discharge amount of the battery by the motor is obtained from the target SOC and the actual SOC.

[0006]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

In the present invention, the running state of the hybrid vehicle, for example, whether the vehicle is uphill or downhill, is determined from the charge / discharge state of the battery of the hybrid vehicle.
The feature is that the target state of charge (target SOC) is appropriately changed based on this.

As a method for controlling such an SOC, first, an initial target value SOCti of the SOC is set. The average value of the system is set as the initial target value SOCti. However, in order to secure a sufficient regenerative energy acceptance amount, this value is usually set to a value slightly exceeding half of the battery capacity.

Next, an average charge / discharge amount is obtained from the charge amount and the discharge amount of the battery, and an SOC correction amount SOC for correcting the initial target value SOCti of the SOC based on the average charge / discharge amount.
Calculate tc. FIG. 1 shows an example of an algorithm for obtaining the SOCtc. In FIG. 1, when the discharge amount of the battery increases, the SOC correction amount S in a predetermined pattern.
As the OCtc increases and the charge amount increases, the SOCtc decreases in a predetermined pattern. Note that SO
The algorithm for obtaining Ctc is not limited to the example shown in FIG. 1 and can be appropriately changed according to the battery characteristics, the running characteristics of the hybrid vehicle, and the like.

The SOC correction amount SO obtained as described above
The target value of the SOC, that is, the target SOC (S
OCt) is obtained as follows.

[0011]

(Equation 1) As shown in the above equation (1), the target SOC SO
Ct is an SOC initial target value SOCti and an SOC correction amount S
It is obtained as the sum with OCtc. As shown in FIG. 1, for example, when the discharge amount of the battery increases at the time of climbing a slope or the like, the value of SOCtc becomes a positive value, so the value of SOCt also increases. As a result, the battery is charged by the power of the engine mounted on the hybrid vehicle. By such control, the operating time of the engine is increased, but it is possible to avoid as much as possible the possibility that the power performance expected to be further down, that is, the motor cannot be run.

On the other hand, when the charge amount of the battery is increased, for example, on a downhill, as shown in FIG. 1, the value of SOCtc becomes negative, so that the value of SOCt also becomes low. For this reason, the travel by the motor increases, and the fuel efficiency can be improved. In this case, the SOC of the battery is kept low.
Recovery of regenerative power can also be performed sufficiently.

As described above, while determining the running conditions, the SO
Since Ct is changed, SOCt with the highest fuel efficiency can be set.

Next, the required engine power, which is the required output of the engine, is determined from the SOC target value SOCt determined as described above. The required engine power Pe is calculated by the following equation.

[0015]

(Equation 2) Here, the vehicle required power Pv is the power required to make the vehicle travel, and changes according to the location where the vehicle travels, such as when climbing uphill, downhill, traveling on level ground, and the like. Correction power Pc
Is the power required to match the actual SOC of the battery to the SOCt determined as described above from the charge / discharge amount of the battery that varies depending on the running state of the vehicle.
When the actual battery SOC is larger than the SOCt, the corrected power Pc becomes a negative value, and the actual SOC becomes the SOC.
When it is smaller than t, the correction power Pc has a positive value.

FIG. 2 shows an example of an algorithm for calculating the corrected power Pc. In FIG. 2, the target SOC (SOCt) is obtained by the above equation (1), and changes according to the average charge / discharge amount of the battery. Therefore, the origin in FIG. 2 moves in the SOC axis direction according to the value of SOCt. When the actual SOC of the battery shown on the horizontal axis of FIG. 2 is larger than such SOCt, the corrected power Pc becomes a negative value as shown in FIG. Also, the actual SOC of the battery is better than SOCt.
Is small, Pc is a positive value. However, in any case, a limit is set so that the value does not become larger than a predetermined value. This is to prevent the engine from requesting infinite power or the motor from consuming more power than necessary.

As described above, for example, when the actual battery SOC is larger than the SOCt obtained from the current running state of the vehicle, the corrected power Pc becomes negative. The value is smaller than the power Pv. As a result, the running power can be supplied by the motor by the difference between the vehicle required power Pv and the engine required power Pe, that is, Pc, and the energy charged in the battery can be discharged to lower the SOC of the battery. On the other hand,
If the actual SOC of the battery is smaller than SOCt,
The engine required power Pe is larger than the vehicle required power Pv by the correction power Pc. This is for charging the electric power corresponding to Pc to the battery by the engine and raising the SOC of the battery to SOCt. Thus, the corrected power Pc is used to determine the amount of battery charge by engine power or the amount of battery discharge by motor.

FIG. 3 shows an operation flow of the above-described method for controlling the state of charge of a battery in a hybrid vehicle according to the present invention. In FIG. 3, first, the vehicle required power P
v is calculated by a predetermined method (S1).

At the same time, the charge / discharge amount of the battery for a predetermined time, for example, 10 minutes, is calculated, and the average charge / discharge amount is obtained therefrom (S2). Further, the initial target value S of the battery SOC
OCti is set (S3).

From the average charge / discharge amount obtained in S2, FIG.
SOCtc is calculated based on the algorithm of (1), and SOCt, which is the target value of SOC, is calculated by equation (1) (S4). From the SOCt and the actual SOC of the battery, the above-described corrected power Pc is obtained by the algorithm of FIG. 2 (S5).

From the required vehicle power Pv and the corrected power Pc obtained as described above, the required engine power Pe is calculated.
Is obtained by the above equation (2) (S6). Thereafter, based on the required engine power Pe, the battery is charged by the engine power or the battery is discharged by the motor by a predetermined amount, and the SOC of the battery is controlled to reach the target SOC, SOCt (S7).

FIGS. 4 to 6 show examples in which the above-described method for controlling the state of charge of a battery in a hybrid vehicle according to the present invention is applied to an actual battery.

FIG. 4 shows how the actual charge / discharge amount of the battery changes. FIG. 5 shows the average charge / discharge amount of the battery obtained from the charge / discharge amount of FIG. Further, FIG. 6 shows the target SOC (SOCt) obtained from the algorithm shown in FIG. 1 and equation (1) based on the average charge / discharge amount.

As described above, in the present invention, the target SOC is appropriately changed according to the average charge / discharge amount of the battery. Therefore, it is possible to finely control the state of charge of the battery according to the running state of the hybrid vehicle.

[0025]

As described above, according to the present invention,
The target SOC of the battery is appropriately adjusted according to a change in the traveling state of the vehicle such as when the amount of discharge is large when climbing a slope, when the amount of charge is large when descending a slope, and when traveling on level ground. It can be used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for controlling a state of charge of a battery in a hybrid vehicle according to the present invention;
FIG. 9 is a diagram illustrating an example of an algorithm for calculating a C correction amount.

FIG. 2 is a diagram showing an example of an algorithm for calculating a correction power from a target SOC obtained from the SOC correction amount shown in FIG. 1 and an actual SOC of a battery.

FIG. 3 is a flowchart of an operation of a method for controlling a state of charge of a battery in a hybrid vehicle according to the present invention.

FIG. 4 is a diagram showing a state of an actual charge / discharge amount of a battery.

FIG. 5 is a view showing an average charge / discharge amount obtained from the charge / discharge amount shown in FIG. 4;

6 is a diagram showing a target SOC obtained from the average charge / discharge amount shown in FIG. 5 by the method of controlling the state of charge of a battery in a hybrid vehicle according to the present invention.

Claims (1)

[Claims] 1. An initial target value of a state of charge (SOC) of a battery is set, an average charge / discharge amount is obtained from a charge amount and a discharge amount of the battery, and the initial target value is corrected based on the average charge / discharge amount. The target SOC is obtained by correcting the initial target value based on the SOC correction amount. The target SOC and the actual SOC are used to calculate the amount of battery charge by engine power or the amount of battery discharge by motor. A method for controlling the state of charge of a battery in a hybrid vehicle, wherein a method for obtaining a certain corrected power is provided.