JP2015052461A - Power storage system and charging rate estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage system and a charging rate estimation method capable of easily estimating the charging rate of each of a plurality of types of power storage devices interconnected in parallel while reducing the number of current detecting means.SOLUTION: A microcomputer 51 calculates the SOC of a power storage unit 20 on the basis of the current flowing through the power storage unit 20 that is detected by a current sensor 30. The microcomputer 51 calculates the OCV of the power storage unit 20 from the calculated SOC of the power storage unit 20 using the relationship between the SOC and OCV usable for the power storage unit 20 that is stored in a memory 52, and estimates the SOC of each of a lead acid battery 21 and nickel hydrogen battery 22 from the OCV of the power storage unit 20.

Description

  The present invention relates to a power storage system including a power storage unit configured by connecting a plurality of types of power storage devices in parallel, and a charging rate estimation method.

  A vehicle for storing electric power supplied to a motor is mounted on a vehicle such as EV or HV. The power storage unit is configured by connecting a plurality of power storage devices in parallel (see, for example, Patent Document 1). At this time, as shown in FIG. 5, when a plurality of batteries (for example, nickel metal hydride batteries) 100 and 101 are connected in parallel and used to estimate the charging rate (SOC) of each battery 100 and 101, each battery 101 , 101 are provided, and current sensors 110, 111 for detecting the current flowing through the current sensor 101 are provided, and the controller 120 estimates the SOC using each detected current value.

JP 2010-11708 A

  However, regarding the number of current sensors (110, 111), current sensors are required for parallel batteries, which is disadvantageous in terms of cost. In addition, when different types of batteries are connected in parallel as the plurality of batteries (110, 111), it is necessary to perform calculations when estimating the SOC of each battery, which increases the calculation cost.

  An object of the present invention is to provide a power storage system and a charge rate estimation method that can easily estimate the charge rates of a plurality of types of power storage devices connected in parallel while reducing the number of current detection means.

  In the first aspect of the present invention, a plurality of types of power storage devices are connected in parallel, the power storage unit is capable of discharging to a load and is capable of charging the plurality of types of power storage devices, and flows through the power storage unit Current detection means for detecting current, and a common open circuit voltage or a range of power that can be input and output within the range of charge rates that can be used for the plurality of types of power storage devices as the charge rate that can be used for the power storage unit, A storage unit that stores in advance a relationship between a usable charging rate and an open circuit voltage or input / output available power for the power storage unit, and a current of the power storage unit based on a current flowing through the power storage unit detected by the current detection unit. A power storage unit charging rate calculating unit that calculates a charging rate, and a storage unit charging rate calculated by the power storage unit charging rate calculating unit is used for the power storage unit stored in the storage unit. The open circuit voltage or the input / output possible power of the power storage unit is calculated using the relationship between the possible charging rate and the open circuit voltage or the input / output possible power, and the plurality of values are calculated from the open circuit voltage or the input / output possible power of the power storage unit The gist of the invention is that it comprises a charge rate estimating means for estimating the charge rate of each type of power storage device.

  According to the first aspect of the present invention, in the storage unit, the common open circuit voltage or the range of power that can be input / output within the range of the charge rate that can be used for a plurality of types of power storage devices can be used. As a rate, the relationship between the charge rate that can be used for the power storage unit and the open circuit voltage or input / output power is stored in advance. In the power storage unit charging rate calculation means, the charging rate of the power storage unit is calculated based on the current flowing through the power storage unit detected by the current detection unit. In the charging rate estimation means, the relationship between the usable charging rate for the power storage unit stored in the storage means and the open circuit voltage or input / output power is calculated from the charging rate of the power storage unit calculated by the power storage unit charging rate calculation unit. The open circuit voltage or the input / output possible power of the power storage unit is calculated by using this, and the charging rate of each of the plurality of types of power storage devices is estimated from the open circuit voltage or the input / output possible power of the power storage unit. Thereby, it is possible to easily estimate the charging rate of each of a plurality of types of power storage devices connected in parallel while reducing the number of current detection means.

As described in claim 2, in the power storage system according to claim 1, the plurality of types of power storage devices may include lead storage batteries.
As described in claim 3, in the power storage system according to claim 2, the plurality of types of power storage devices may include nickel metal hydride batteries.

  In the invention according to claim 4, in a power storage system comprising a plurality of types of power storage devices connected in parallel, including a power storage unit capable of discharging the load and charging the plurality of types of power storage devices, The charge rate that can be used for the power storage unit, with the common open circuit voltage or the range of power that can be input and output within the range of charge rates that can be used for the plurality of types of power storage devices as the charge rate that can be used for the power storage unit And the relationship between the open circuit voltage or the power that can be input / output is obtained in advance, and the power storage unit detected using the relationship between the charge rate that can be used for the power storage unit and the open circuit voltage or the power that can be input / output The open circuit voltage or input / output possible power of the power storage unit is calculated from the charging rate of the power storage unit obtained from the current flowing through And summarized in that which is adapted to estimate the respective charging rate of the plurality of types of electric storage devices.

  According to the invention described in claim 4, the common open circuit voltage or the range of power that can be input / output in the range of the charge rate that can be used for a plurality of types of power storage devices is used as the charge rate that can be used for the power storage unit. The relationship between the charge rate that can be used for the power storage unit and the open circuit voltage or power that can be input and output is acquired in advance. Then, using the relationship between the usable charging rate of the power storage unit and the open circuit voltage or input / output power, the open circuit voltage of the power storage unit from the charge rate of the power storage unit obtained from the detected current flowing in the power storage unit Alternatively, the input / output possible power is calculated, and the charging rate of each of the plural types of power storage devices is estimated from the open circuit voltage of the power storage unit or the input / output possible power. Thereby, it is possible to easily estimate the charging rate of each of a plurality of types of power storage devices connected in parallel while reducing the number of current detection means.

  According to the present invention, it is possible to easily estimate the charging rate of each of a plurality of types of power storage devices connected in parallel while reducing the number of current detection means.

The figure which shows the electrical constitution of the electrical storage system for vehicles of embodiment. The figure which shows the relationship between SOC of each battery, and OCV. The figure which shows the relationship between SOC of an electrical storage part, and OCV. The figure which shows the relationship between SOC of each battery, and input-output possible electric power. Explanatory drawing of an electrical storage system.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
In the present embodiment, the invention is embodied in a power storage system of a hybrid vehicle (HV) as a vehicle. The hybrid vehicle is equipped with a motor and an engine as a power source, and drives the axle using these.

  As shown in FIG. 1, the power storage system 10 includes a power storage unit 20. The power storage unit 20 includes a lead storage battery 21 as a power storage device and a nickel metal hydride battery 22 as a power storage device, and the lead storage battery 21 and the nickel hydrogen battery 22 are connected in parallel. The lead storage battery 21 and the nickel metal hydride battery 22 can be charged. The lead storage battery 21 and the nickel metal hydride battery 22 can be discharged to a motor generator (MG) 70 and an inverter 71 as loads. As described above, the power storage unit 20 is configured by connecting a plurality of types of power storage devices (21, 22) in parallel. Can be charged. The plurality of types of power storage devices include a lead storage battery 21 and a nickel metal hydride battery 22.

  The lead storage battery 21 has an internal resistance with respect to a part that generates an electromotive force (open circuit voltage: OCV). The nickel metal hydride battery 22 has an internal resistance with respect to a portion that generates an electromotive force (open circuit voltage: OCV). The internal resistance values of the lead storage battery 21 and the nickel metal hydride battery 22 are different.

  The power storage system 10 includes a current sensor 30 and a voltage sensor 40. A current flowing through the power storage unit 20 is detected by a current sensor 30 as current detection means. That is, the current flowing in the parallel circuit composed of a plurality of batteries is detected instead of the current flowing in each battery. In other words, the current flowing through the load is detected. The voltage sensor 40 detects the voltage across the power storage unit 20.

Further, the power storage system 10 includes a controller 50 and a display 60.
Motor generator (MG) 70 is connected to inverter 71. When the motor generator 70 functions as a generator during regeneration, the alternating current generated by the motor generator 70 is converted into direct current by the inverter 71 and supplied to the lead storage battery 21 or the nickel metal hydride battery 22 as charging power. It becomes possible. When torque is obtained by the motor generator 70 during power running, the inverter 71 converts the direct current of the lead storage battery 21 or the nickel metal hydride battery 22 into alternating current and supplies the alternating current to the motor generator 70 to rotate the axle by the motor generator 70. Therefore, the rotational force can be obtained.

  The lead storage battery 21 is used at a charge rate (SOC; state of charge) of, for example, 90% or more. The negative terminal of the lead storage battery 21 is connected to the inverter 71 and the positive terminal of the lead storage battery 21 is connected to the inverter 71. The chargeable / dischargeable lead storage battery 21 is supplied with electric power from the motor generator 70 (inverter 71).

The lead storage battery 21 drives a starter motor, a radio, a meter, an oil pump, a head lamp, a tail lamp, and the like for starting the engine.
The nickel metal hydride battery 22 is configured by connecting a plurality of (for example, 10) cells in series. The nickel metal hydride battery 22 is used with an SOC of 20% to 80%, for example. The negative terminal of the nickel metal hydride battery 22 is connected to the inverter 71 and the positive terminal of the nickel metal hydride battery 22 is connected to the inverter 71. The chargeable / dischargeable nickel metal hydride battery 22 is supplied with electric power from the motor generator 70.

  Rather than calculating the SOC of each battery in the power storage unit 20 configured by connecting a plurality of types of secondary batteries in parallel, the power storage unit 20 (that is, a parallel power supply) is regarded as one power source, and Calculate the SOC. In this case, since the SOC ranges to be used are different, for the OCV and SOC, as shown in FIG. 2, using a common OCV range (a range in which both batteries can be used) from the usable SOC ranges of the batteries, FIG. As shown, the SOC range in the power storage unit 20 is associated with the OCV.

explain in detail.
In FIG. 2, the SOC and OCV characteristics of the lead storage battery 21 and the nickel metal hydride battery 22 are shown. In FIG. 2, the horizontal axis represents the SOC of each battery (lead storage battery 21, nickel hydride battery 22), and the vertical axis represents the OCV of each battery (lead storage battery 21, nickel hydride battery 22). In FIG. 2, the characteristic line L10 about the lead acid battery 21 and the characteristic line L11 about the nickel metal hydride battery 22 are shown.

  The usable SOC range of the nickel metal hydride battery 22 is 20 to 80%. The usable SOC range of the lead storage battery 21 is 90 to 100%. And the OCV range which can use both batteries (lead storage battery 21, nickel metal hydride battery 22) is Y1-Y2. Therefore, if the OCV value of power storage unit 20 is known in the range of Y1 to Y2, the SOC of lead storage battery 21 and the SOC of nickel metal hydride battery 22 can be known. For example, if the OCV value of the power storage unit 20 is “b”, the SOC of the lead storage battery 21 is “c2”, and the SOC of the nickel metal hydride battery 22 is “c1”.

  In FIG. 1, the controller 50 includes a microcomputer 51 and a memory 52. The memory 52 stores various programs and various data. The memory 52 stores a map shown in FIG.

  As shown in FIG. 3, the horizontal axis represents the SOC of the power storage unit 20, and the vertical axis represents the OCV of the power storage unit 20. In FIG. 3, the characteristic line L1 is provided, and the characteristic line L1 is used to determine the common OCV range in the usable SOC range of the lead storage battery 21 and the nickel metal hydride battery 22 as the usable charging rate of the power storage unit 20. The relationship between usable SOC and OCV for the power storage unit 20 is defined.

  As described above, the memory 52 as the storage unit uses the common OCV range in the usable SOC range of the plurality of types of power storage devices (21, 22) as the usable SOC of the power storage unit 20, and the power storage unit 20 The relationship between the usable SOC and OCV is stored in advance. Further, the characteristic line L10 for the lead storage battery 21 and the characteristic line L11 for the nickel metal hydride battery 22 in FIG. 2 are also stored in the memory 52 as maps.

  A current sensor 30 and a voltage sensor 40 are connected to the controller 50, and detection signals of the sensors 30 and 40 are input. The controller 50 is connected to an inverter 71 via a motor generator ECU (ECU; electronic control unit) (not shown) so that the output power of the inverter 71 (motor generator 70) can be controlled by the motor generator ECU. ing. Specifically, the motor generator ECU receives a vehicle deceleration request or an acceleration request from a vehicle ECU (not shown) and controls whether the motor generator 70 is driven by a motor (powering) or generator driven (regeneration). Further, the motor generator ECU controls the output power of the inverter 71 (motor generator 70) based on information from the controller 50 to limit the output to the batteries 21 and 22.

Next, the operation of the power storage system 10 configured as described above will be described.
The microcomputer 51 uses the current sensor 30 to calculate the SOC in the power storage unit 20 configured by connecting a plurality of types of secondary batteries in parallel. Specifically, the microcomputer 51 determines the SOC of the power storage unit 20 from the charge / discharge current of the power storage unit 20 detected by the current sensor 30 and the voltage across the power storage unit 20 detected by the voltage sensor 40. The SOC is obtained by current integration. Specifically, it is obtained by the sum of the initial SOC and the time integration value of the charge / discharge current. Since the detection of the SOC by the current integration causes a shift due to the accumulation of the error of the current sensor, the relationship between the OCV and the SOC of the power storage unit 20 is obtained in advance to correct the shift, and the SOC with respect to the OCV at that time is obtained. To correct. The OCV is obtained from Vocv = V + RI from the measured voltage value V, the known internal resistance R, and the measured current value I.

  And the microcomputer 51 reads OCV of the electrical storage part 20 comprised by connecting in parallel multiple types of secondary batteries using the map of FIG. 3 from SOC of the electrical storage part 20. FIG. Specifically, the OCV value b of the power storage unit 20 is obtained from the OCV value a of the power storage unit 20 at that time in FIG.

  The microcomputer 51 reads the SOC of each of the batteries 21 and 22 from the map data shown in FIG. 2 from the read OCV value of the power storage unit 20 configured by connecting a plurality of types of secondary batteries in parallel. Specifically, the SOC value c1 of the nickel metal hydride battery 22 and the SOC value c2 of the lead storage battery 21 are obtained from the OCV value b of the power storage unit 20.

  Then, the microcomputer 51 causes the display 60 to display the SOC of each of the batteries 21 and 22. Specifically, the SOC of the lead storage battery 21 is displayed on the display unit 61, and the SOC of the nickel metal hydride battery 22 is displayed on the display unit 62.

  Furthermore, output control of the inverter 71 is performed based on the SOC of each of the batteries 21 and 22. Specifically, for example, the microcomputer 51 calculates chargeable / dischargeable power of the batteries 21, 22, and output control of the inverter 71 is performed by a motor generator ECU (not shown) based on the calculated chargeable / dischargeable power.

  In this way, since the SOC of the power storage unit 20 configured by connecting a plurality of types of secondary batteries in parallel is managed, only one current sensor is required, and the SOC of each of the batteries 21 and 22 is reduced with a small number of current sensors. And the number of current sensors can be reduced.

  In addition, the number of SOC management can be reduced. That is, compared with the case of obtaining the SOC of each battery by managing the SOC as the power storage unit 20 configured by connecting a plurality of types of secondary batteries in parallel instead of the SOC of the nickel metal hydride battery 22 and the lead storage battery 21. Calculation cost can be reduced. That is, the SOC of each of the batteries 21 and 22 can be easily estimated by reducing the calculation load.

According to the above embodiment, the following effects can be obtained.
(1) As a configuration of the power storage system, the microcomputer 51 serving as the power storage unit charging rate calculation unit calculates the SOC of the power storage unit 20 based on the current flowing through the power storage unit 20 detected by the current sensor 30. The microcomputer 51 as the charging rate estimation means calculates the OCV of the power storage unit 20 from the calculated SOC of the power storage unit 20 using the relationship between the usable SOC and the OCV for the power storage unit 20 stored in the memory 52. Then, the SOC of each of the lead storage battery 21 and the nickel metal hydride battery 22 is estimated from the OCV of the power storage unit 20. Therefore, it is possible to easily estimate the charging rate of the lead storage battery 21 and the nickel hydride battery 22 (multiple types of power storage devices) connected in parallel while reducing the number of current sensors.

  (2) As a charging rate estimation method, the common OCV range in the usable SOC range of the plurality of types of power storage devices (21, 22) is used as the usable SOC of the power storage unit 20, and is used for the power storage unit 20. The relationship between possible SOC and OCV is acquired in advance. Then, using the relationship between the usable SOC and the OCV for the power storage unit 20, the OCV of the power storage unit 20 is calculated from the SOC of the power storage unit 20 obtained from the detected current flowing in the power storage unit 20. The SOCs of the lead storage battery 21 and the nickel metal hydride battery 22 are estimated from the 20 OCVs. Therefore, it is possible to easily estimate the charging rate of the lead storage battery 21 and the nickel hydride battery 22 (multiple types of power storage devices) connected in parallel while reducing the number of current sensors.

The embodiment is not limited to the above, and may be embodied as follows, for example.
-Instead of the relationship between the SOC and OCV of each battery in FIG. 2, the SOC of each of the lead storage battery 21 and the nickel metal hydride battery 22 is estimated using the relationship between the SOC of each battery and the input / output possible power shown in FIG. You may do it.

  As shown in FIG. 4, the horizontal axis represents the SOC of the battery (lead storage battery 21, nickel hydride battery 22), and the vertical axis represents the input / output power of the battery (lead storage battery 21, nickel hydride battery 22). In FIG. 4, the characteristic line L20 about the lead storage battery 21 and the characteristic line L21 about the nickel metal hydride battery 22 are shown. The usable SOC range of the nickel metal hydride battery 22 is 20 to 80%. The usable SOC range of the lead storage battery 21 is 90 to 100%. And the range of the electric power which can be used for both batteries (lead storage battery 21 and nickel metal hydride battery 22) is Y11 to Y12. Therefore, if the input / output possible power value of power storage unit 20 is known in the range of Y11 to Y12, the SOC of lead storage battery 21 and the SOC of nickel metal hydride battery 22 can be known.

  Thus, as a charging rate estimation method, the common input / output available power range in the usable SOC range of the plurality of types of power storage devices (21, 22) is used as the usable SOC of the power storage unit 20, and the power storage unit The relationship between the usable SOC and the input / output available power for 20 is acquired in advance. Then, by using the relationship between the usable SOC and the power that can be input / output for the power storage unit 20, the input / output power of the power storage unit 20 is calculated from the SOC of the power storage unit 20 obtained from the detected current flowing in the power storage unit 20. The SOC of each of the lead storage battery 21 and the nickel metal hydride battery 22 is estimated from the power that can be input and output from the power storage unit 20 by calculation. In addition, as a configuration of the power storage system, the memory 52 as a storage unit can use the common power input / output range in the range of usable SOC of the plurality of types of power storage devices (21, 22). As the SOC, the relationship between the usable SOC and the power that can be input / output for the power storage unit 20 is stored in advance. The microcomputer 51 calculates the SOC of the power storage unit 20 based on the current flowing through the power storage unit 20 detected by the current sensor 30. From the calculated SOC of the power storage unit 20, the input / output possible power of the power storage unit 20 is calculated using the relationship between the usable SOC and the input / output available power for the power storage unit 20 stored in the memory 52. The SOCs of the lead storage battery 21 and the nickel metal hydride battery 22 may be estimated from the 20 input / output powers.

-An electrical storage device is not limited to a lead acid battery and a nickel metal hydride battery. For example, a lithium ion secondary battery, a capacitor, or the like may be combined and connected in parallel.
-About the kind of electrical storage device connected in parallel in an electrical storage part, although there were two types, a nickel hydrogen battery and a lead storage battery, three or more types of electrical storage devices may be connected in parallel.

-You may display SOC of the electrical storage part 20 on the indicator 60. FIG.
-Although load was motor generator 70 and inverter 71, it is not limited to this, The electric power of an electrical storage device should just be dischargeable.

  DESCRIPTION OF SYMBOLS 10 ... Power storage system, 20 ... Power storage part, 21 ... Lead storage battery, 22 ... Nickel metal hydride battery, 30 ... Current sensor, 51 ... Microcomputer, 52 ... Memory, 70 ... Motor generator, 71 ... Inverter.

Claims (4)

A power storage unit configured by connecting a plurality of types of power storage devices in parallel, capable of discharging the load and charging the plurality of types of power storage devices;
Current detection means for detecting a current flowing through the power storage unit;
The charge rate that can be used for the power storage unit, with the common open circuit voltage or the range of power that can be input and output within the range of charge rates that can be used for the plurality of types of power storage devices as the charge rate that can be used for the power storage unit Storage means for storing in advance the relationship between the open circuit voltage or the power that can be input and output;
Power storage unit charge rate calculating means for calculating a charge rate of the power storage unit based on a current flowing through the power storage unit detected by the current detection unit;
From the charging rate of the power storage unit calculated by the power storage unit charging rate calculating means, using the relationship between the usable charging rate and the open circuit voltage or the input / output possible power for the power storage unit stored in the storage means. Charge rate estimating means for calculating an open circuit voltage or input / output available power of the power storage unit and estimating a charge rate of each of the plurality of types of power storage devices from the open circuit voltage or input / output available power of the power storage unit;
A power storage system comprising:   The power storage system according to claim 1, wherein the plurality of types of power storage devices include a lead storage battery.   The power storage system according to claim 2, wherein the plurality of types of power storage devices include nickel metal hydride batteries. In a power storage system comprising a power storage unit configured by connecting a plurality of types of power storage devices in parallel and capable of discharging the load and charging the plurality of types of power storage devices,
The charge rate that can be used for the power storage unit, with the common open circuit voltage or the range of power that can be input and output within the range of charge rates that can be used for the plurality of types of power storage devices as the charge rate that can be used for the power storage unit And the relationship between the open circuit voltage or power that can be input and output in advance,
Using the relationship between the usable charging rate for the power storage unit and the open circuit voltage or power that can be input and output, the power storage unit is opened from the charging rate of the power storage unit obtained from the detected current flowing in the power storage unit. Charge rate estimation characterized by calculating circuit voltage or input / output possible power and estimating each charge rate of said plurality of types of power storage devices from open circuit voltage or input / output possible power of said power storage unit Method.