Patent Application
20110089905
1. Field of the Invention
The present invention relates to a power supply device that controls the connection state between a load and a battery pack that is composed of a plurality of rechargeable batteries. In particular, the present invention relates to a control art that controls the connection state between a battery pack and an inverter in electric vehicles. Examples of such electric vehicles can be provided by battery electric vehicle (BEV), hybrid electric vehicle (HEV), hybrid electric vehicle including fuel cells and rechargeable batteries. Such electric vehicles convert DC electric power into AC electric power by means of an inverter, and provide the converted electric power to an electric motor. The DC electric power is provided from a battery pack as driving power source installed on the electric vehicles.
2. Description of the Related Art
In recent years, in consideration of environmental issues, hybrid electric vehicles have been commercially practical that are driven by efficient combination of internal-combustion engine and electric motor. Hybrid electric vehicles include a rechargeable battery pack. The battery pack provides electric power to the electric motor in start, acceleration and the like, and retrieves vehicle kinetic energy as electric power in downhill, breaking and the like.
A hybrid electric vehicle has been proposed that includes configuration that allows the included battery pack to be charged with electric power provided from external power sources such as commercial power. In this hybrid electric vehicle, in the case where the battery pack is previously charged by external power sources, the vehicle can be driven for a relatively short distance of driving, such as in driving to and from work or for shopping, with its internal-combustion engine being stopped. As a result, it is possible to improve the total fuel consumption efficiency of the vehicle. Such a drive mode is also referred to as an EV (Electric Vehicle) drive mode.
In order to improve drive performance in this EV drive mode, it is preferable to increase the charging/discharging performance of the battery pack. Since battery packs deteriorate due to over-discharged operation, over-charged operation, and the like, it is important that battery packs are held within a proper range of remaining capacity (also referred to as State Of Charge (SOC), battery charge amount, charge state value and the like, and hereinafter occasionally referred to as “SOC”).
Japanese Patent Laid-Open Publication No. 2008-312381 proposes a method that improves estimation accuracy of SOC of a storage battery. According to this method, as shown in
In this EV drive mode, when a reset request for a first power storage unit BAT1 (SOC1 reset request) is issued, current control is performed to discharge actively the first power storage unit BAT1. After time t2 when charging by an external power supply becomes allowed, a discharge current of the first power storage unit BAT1 to be reset is kept at a given current value, and a second power storage unit BAT2 not to be reset is charged with a charge current including at least the discharge current of the first power storage unit BAT1. When a distinctive point appears on a battery voltage characteristic of the first power storage unit BAT1 at a subsequent time t3, an estimated value of an SOC of the first power storage unit BAT1 is reset to a predetermined reference value. This control can improve estimation accuracy of SOC of the power storage unit.
However, estimation accuracy of SOC is limited. For this reason, switching accuracy between BEV and HEV drive modes in accordance only with calculated SOC is limited. In particular, even if an error between the calculated value of SOC and actual SOC is small, errors are accumulated for a long period of use. Accordingly, the accumulated error will be large. If accumulated error of the calculated values of SOC becomes large, precise control will be difficult. Imprecise charging/discharging operation control may affect the battery pack. This increases risk of battery life deterioration.
The present invention is aimed at solving the problem. It is a main object of the present invention to provide a power supply device capable of changing a charging/discharging current limit values at appropriate timing whereby reducing adverse effect on a battery pack.
To achieve the above object, a power supply device according to a first aspect of the present invention includes a rechargeable battery pack, a charging/discharging control portion, a current detecting portion, a battery capacity calculating portion. The charging/discharging control portion controls charging/discharging operation on the battery pack. The current detecting portion detects charging/discharging currents flowing in the battery pack. The battery capacity calculating portion estimates the remaining capacity of the battery pack based on the charging/discharging currents detected by the current detecting portion. The charging/discharging control portion selects one of control modes. The charging/discharging operation is controlled based on the selected control mode. When the remaining capacity estimated by the battery capacity calculating portion is higher than a predetermined control upper limit, a charging operation disabled mode is selected in that the charging operation is disabled. When the estimated remaining capacity is lower than a control lower limit specified lower than the control upper limit, a discharging operation disabled mode is selected in that the discharging operation is disabled. When the estimated remaining capacity is higher than an upper limit of a given range having its center at a target state value specified between the control upper and lower limits, an allowance mode is selected in that charging/discharging current limit values are adjusted to current values that allow a discharging amount to exceed a charging amount in a predetermined period. When the estimated remaining capacity is lower than the upper limit of the given range, a restriction mode is selected in that charging/discharging currents are restricted so that the remaining capacity is held within the given range having its center at the target state value. According to this power supply device, since the control modes for controlling charging/discharging currents are thus selected in accordance with the remaining capacity, appropriate operation is achieved. In addition, it is possible to prevent the battery pack from being over-charged/over-discharged, and to provide the battery pack with a long life.
In a power supply device according to a second aspect of the present invention, the charging/discharging control portion can adjusts the charging/discharging current limit values in the allowance mode to current values that allow the integrated value of the discharging current in the predetermined period to exceed the integrated value of the chagrining current. According to this power supply device, since the discharging current is allowed to be larger than the charging current in the allowance mode, it is possible to effectively use the battery pack within a range in that the battery pack is not over-charged/over-discharged.
In a power supply device according to a third aspect of the present invention, the charging/discharging control portion can control charging/discharging operation so that the time variation amount of the discharging current is larger than the time variation amount of the charging current in the allowance mode. According to this power supply device, since the discharging current is allowed to be larger than the charging current in the allowance mode, it is possible to effectively use the battery pack within a range in that the battery pack is not over-charged/over-discharged.
In a power supply device according to a fourth aspect of the present invention, the charging/discharging control portion can control charging/discharging operation so that the time variation amount of the discharging current in the restriction mode is smaller than the time variation amount of the discharging current in the allowance mode. According to this power supply device, since the discharge amount in the restriction mode is suppressed as compared with the allowance mode, it is possible to prevent the battery pack from being over-discharged and to protect the battery pack.
A power supply device according to a fifth aspect of the present invention can further include a power supply side communicating portion that transmits the charging/discharging current limit values based on the remaining capacity of the battery pack estimated by the battery capacity calculating portion to a device side to be provided with electric power. This power supply device can provide notification of an available current amount depending on the control modes on the power supply device side to the device side to be provided with electric power. For example, after it is detected that the remaining capacity is lower than the upper limit of the given range, the power supply side communicating portion notifies the device side to be provided with electric power that the charging/discharging current limit values are restricted to small values capable of holding the target state value.
A power supply device according to a sixth aspect of the present invention can further include an externally-connecting switch that can electrically connect the battery pack to an external charging device. According to this power supply device, a battery pack can be charged not only by another battery pack included in the power supply device but also by an external power supply device.
In a power supply device according to a seventh aspect of the present invention, the power supply device can be a vehicle power supply device. In this case, the allowance mode is an EV drive mode, and the restriction mode is an HEV drive mode. According to this power supply device, the EV drive mode and the HEV drive mode can be switched from one to another at appropriate timing in so-called plug-in hybrid electric cars so as not to adversely affect the battery pack. Therefore, the battery pack can be reliably used for long term.
In a power supply device according to an eighth aspect of the present invention, the control upper limit can be not less than 80% of the fully-charged capacity of the battery pack.
In a power supply device according to a ninth aspect of the present invention, the target state value can be not more than 50% of the fully-charged capacity of the battery pack.
According to this power supply device, drive modes can be selected to keep SOC at about 50%, which is suitable particularly to an HEV drive mode.
Therefore, this power supply device is effective for EV, plug-in control.
In a power supply device according to a tenth aspect of the present invention, the restriction upper limit can be 20 to 60 Ah.
In a power supply device according to an eleventh aspect of the present invention, the target state value can be 2 to 10 Ah.
The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings.
The following description will describe embodiments according to the present invention with reference to the drawings. It should be appreciated, however, that the embodiments described below are illustrations of a power supply device and a method for controlling charging/discharging operation of a power supply device to give a concrete form to technical ideas of the invention, and a power supply device and a method for controlling charging/discharging operation of a power supply device of the invention are not specifically limited to description below. Furthermore, it should be appreciated that the members shown in claims attached hereto are not specifically limited to members in the embodiments. Unless otherwise specified, any dimensions, materials, shapes and relative arrangements of the members described in the embodiments are given as an example and not as a limitation. Additionally, the sizes and the positional relationships of the members in each of drawings are occasionally shown larger exaggeratingly for ease of explanation. Members same as or similar to those of this invention are attached with the same designation and the same reference numerals, and their description is omitted. In addition, a plurality of structural elements of the present invention may be configured as a single part that serves the purpose of a plurality of elements, on the other hand, a single structural element may be configured as a plurality of parts that serve the purpose of a single element. Also, the description of some of examples or embodiments may be applied to other examples, embodiments or the like.
The following description will describe a power supply device 100 and a charging/discharging control method according to a first embodiment with reference to
As shown in
As shown in
The vehicles controller 8 controls distribution of gasoline engine output and output from the power supply device 100 based on output requirement. The vehicle controller 8 is connected to and can communicate with the power supply controller 12. Thus, the vehicle controller 8 can receive information including SOC of the battery pack 10 (battery SOC value), available charging/discharging current limit values and the like from the power supply controller 12, and can send output requirement and the like to the power supply controller 12. When the battery SOC value is high, the vehicle controller 8 increase output distribution to the power supply device 100. In this case, an EV drive mode is selected in that output distribution to the engine is suppressed. In the EV drive mode, the power supply controller 12 allows the amount of a discharging current from the battery pack 10 to exceed the amount of a charging current to the battery pack 10 until the SOC value becomes not more than a predetermined value. When the power supply controller 12 detects that the SOC value decreases to the predetermined value, a mode is selected in that charging/discharging currents are controlled so as to hold the SOC value at a given value. In addition, the power supply controller 12 notifies the vehicle controller 8 about information that control mode and/or charging/discharging current limit values are changed. Correspondingly, the vehicles controller 8 switches from the EV drive mode to the HEV drive mode in that the vehicle is driven by both the battery and the engine. In the HEV drive mode, charging/discharging currents are controlled so that SOC falls within a given range that has its center at the given value. If SOC decreases and reaches a predetermined minimum control value, a discharging operation disabled mode is selected in that the discharging operation is disabled.
The battery pack 10 can be composed of a plurality of base batteries (battery cells) as rechargeable batteries that are connected to each other in series and/or in parallel. Lithium ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries or the like can be suitably used as rechargeable batteries. Also, in addition to these types of batteries, charge storage elements such as electric double layer capacitors can be used as electric power storage elements. In this specification, the battery pack can includes these types of electric power storage elements.
In the embodiment shown in
The battery pack 10 is connected to an externally-connecting switch SW that allows the battery pack 10 to be electrically connected to an external charging device CD. When the vehicle CA is at rest, the externally-connecting switch SW can be closed (turned ON) so that the battery pack 10 can be charged by the external power source. After the battery pack is charged, the externally-connecting switch SW can be opened (turned OFF). After that, the external charging device CD can be disconnected from the power supply device 100. Commercial power, charging station, and the like can be used as the external charging device CD. A typical example of the vehicle can be provided by a plug-in hybrid car that can be charged by single-phase commercial power for home use. The power supply device 100 thus stores electric power in the battery pack 10, and provides the stored electric power for driving the vehicle.
The power supply controller 12 shown in
The battery capacity calculating portion 15 continuously estimates the charged state (SOC: State Of Charge) of the storage batteries. SOC can be represented by an absolute value (unit [A-h], etc.) of the charged amount of the battery pack, or a ratio (0 to 100%) of the charged amount relative to the charge capacity of the battery pack. In this embodiment, the battery capacity calculating portion 15 sequentially calculates SOC based on the integrated value of the charged/discharged amounts of the battery pack. The integrated value of the charged/discharged amounts can be obtained by integrating product values of battery voltages and battery currents of the battery pack over time.
The charging/discharging control portion 13 adjusts the charging/discharging currents flowing in the battery pack 10 to a value not more than the charging/discharging current limit values. The charging/discharging control portion 13 compares a predetermined remaining capacity with the remaining capacity calculated by the battery capacity calculating portion 15, and switches between control modes. The charging/discharging current limit values are changed depending on the control modes. This control is now described with reference to the graph showing limits and the flowchart of
It is first determined in Step S1 whether the remaining capacity (i.e., SOC) is higher than a control upper limit of the battery pack. If SOC is higher than the control upper limit, the procedure goes to Step S1-2, and a charging operation disabled mode is selected in that the charging operation is disabled. In this case, the charging/discharging operation is stopped, and it is determined that battery abnormality occurs. In addition, for example, a warning sign is displayed, or service request is issued.
If SOC is not higher than the control upper limit, the procedure goes to Step S2, it is determined whether SOC is lower than a control lower limit. If SOC is not higher than the control lower limit, the procedure goes to Step S2-2, and the discharging operation disabled mode is selected in that the discharging operation is disabled, and the procedure ends.
If SOC is higher than the control lower limit, the procedure goes to Step S3, and it is determined whether SOC gets beyond a range in proximity to a target state value, more specifically it is determined whether SOC is lower than the upper limit (target state value+α, hereinafter referred to as range upper limit) of a given range having its center at the target state value (a range of target state value±α). If SOC is higher than the range upper limit, the procedure goes to Step S3-2, an allowance mode is selected that allows a discharging amount to exceed a charging amount in a predetermined period. In this mode, since a discharging amount is allowed to exceed a charging amount, SOC will gradually decrease.
If SOC falls out of the range in proximity to the target state value, the procedure goes to Step S4, and a restriction mode is selected in that the charging/discharging current limit values are reduced so that the remaining capacity is held within the given range having its center at the target state value (from the range upper limit to the range lower limit), and charging/discharging currents are restricted not higher than these limit values.
When SOC reaches the control upper limit so that the battery pack is fully charged, charging operation is disabled. After that, the vehicle is driven. When SOC becomes lower than the control upper limit, the allowance mode is selected. In the allowance mode, a discharging amount is allowed to exceed a charging amount. Specifically, charging/discharging operation is controlled so that the integrated value of discharging amounts is allowed to exceed the integrated value of charging amounts in a predetermined period. Alternatively, charging/discharging operation can be controlled so that the time variation amount of a discharging current is larger than the time variation amount of a charging current in the allowance. Alternatively, charging/discharging operation can be controlled so that the time variation amount of the discharging current in the restriction mode is smaller than the time variation amount of the discharging current in said allowance mode. This allowance mode can correspond to the EV drive mode in that the vehicle is mainly driven by the power supply device.
After that, when it is detected that SOC becomes low, more specifically, when it is detected that SOC becomes not higher than the range upper limit, the EV drive mode is switched to the HEV drive mode so that the discharging current amount is suppressed. Accordingly, the battery pack can be prevented from being over-discharged. Therefore, it is possible to reduce adverse effect on the battery pack. In addition, the power supply device informs the vehicle side that control modes are switched from one to another or charging/discharging currents are restricted to the charging/discharging current limit values. Correspondingly, the vehicle side can select a mode that appropriately controls driving operation of the electric motor and the engine. As a result, the EV drive mode and the HEV drive mode can be appropriately switched from one to another at appropriate timing in so-called plug-in hybrid cars. Therefore, the battery pack can be reliably used for long term.
The control upper limit can be not less than 80% of the fully-charged capacity of the battery pack, 20 to 60 Ah or the like in consideration of the type, the number, the connection type and the like of used batteries. Although the target state value can be determined in consideration of battery conditions and the like, it is preferable that the target state value be a value not more than 50% of the fully-charged capacity of the battery pack or 2 to 10 Ah. In this case, drive modes can be selected to keep SOC at about 50%, which is suitable particularly to an HEV drive mode. Therefore, this power supply device is effective for EV/plug-in control. The control upper and lower limits, and the target state value can be defined by relative values. For example, the predetermined target value can be 5 to 30, preferably 8 to 20 where the control lower limit and the control upper limit are defined as 0 and 100, respectively. For example, the given range having its center at the predetermined target value can be defined by to ±α(α can be 5 to 10% of SOC), by a range of 1 to 5 Ah, or the like.
The aforementioned power supply device can be used as a battery system for vehicles. The power supply device can be installed on electric vehicles such as hybrid cars that are driven by both an engine and an electric motor, and electric vehicles that are driven only by a motor. The power supply device can be used as a power supply device for these types of vehicles.
A power supply device and a method for controlling charging/discharging operation of a power supply device according to the present invention can be suitably applied to charging/discharging control in plug-in hybrid vehicles and hybrid electric vehicles that can switch between the EV drive mode and the HEV drive mode, electric vehicles, and the like.
It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the scope of the invention as defined in the appended claims. The present application is based on Application No. 2009-239,522 filed in Japan on Oct. 16, 2009, the content of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-239522 | Oct 2009 | JP | national |
