JP2014165106A - Secondary battery control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently rise temperature of a secondary battery in a short time.SOLUTION: A secondary battery control device according to the present embodiment includes: a charger/discharger 6 connecting between a first secondary battery 2a and a second secondary battery 2b and charging one of the secondary batteries by the power discharged by the other, with each other; a secondary battery SOC estimation section 3 estimating each of the SOCs of the first and second secondary batteries 2a and 2b; and a charger/discharger control section 10 determining a straight line representing a target SOC on the basis of a preliminarily obtained SOC region where the first and second secondary batteries can output, and controlling the charger/discharger 6 so that the SOC estimated in the secondary battery SOC estimation section 3 equals to the target SOC on the straight line.

Description

  Embodiments described herein relate generally to a secondary battery control device for heating a secondary battery.

  When the secondary battery is used in a low temperature environment, there is a problem that a desired current cannot be output because the internal resistance increases. Conventionally, a method of using the heater device or the like after warming the battery has been proposed for this problem, but there is a problem that a loss of heat energy when the battery is warmed by the heater is large. In view of this, there has been proposed a temperature raising method in which the secondary battery is repeatedly charged and discharged between the secondary battery and the DC capacitor (see, for example, Patent Document 1).

JP 2007-12568 A

  However, in the above temperature raising method, it is necessary to considerably increase the capacity of the capacitor with respect to charge and discharge of a large current necessary for raising the temperature of the battery in a short time, which is a problem in terms of volume and cost.

  The objective of this embodiment is to provide the secondary battery control apparatus which can heat up a secondary battery efficiently in a short time.

  The secondary battery control device according to the present embodiment is a device that controls the first secondary battery and the second secondary battery, and connects the first and second secondary batteries to each other. Charging / discharging means for charging the other secondary battery with the electric power discharged by the secondary battery, first SOC estimating means for estimating the SOC of the first secondary battery, and the second secondary battery A straight line representing a target SOC is determined on the basis of second SOC estimation means for estimating the SOC and the SOC regions that can be output from the first and second secondary batteries acquired in advance, and the first and second Charge / discharge control means for controlling the charge / discharge means so that the SOC estimated by the SOC estimation means becomes the target SOC on the straight line.

The figure which shows the secondary battery system using the secondary battery control apparatus which concerns on 1st Embodiment. The figure which shows the target SOC setting method which concerns on 1st Embodiment. The figure which shows an example of the temperature rising operation which concerns on 1st Embodiment. The figure which shows the target SOC setting method which concerns on 2nd Embodiment. The figure which shows the temperature rising effect characteristic by SOC which concerns on 3rd Embodiment. The figure which shows the target SOC setting method which concerns on 3rd Embodiment. The figure which shows the detail of the charger / discharger control part 10 which concerns on 4th Embodiment. The figure which shows the target SOC setting method which concerns on 4th Embodiment.

  Hereinafter, the secondary battery control device according to the present embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a secondary battery system using the secondary battery control device according to the present embodiment.

  A first secondary battery 2a and a second secondary battery 2b (collectively referred to as a secondary battery) are composed of secondary battery cells 1 electrically connected in a multi-series and multi-parallel configuration, and have a secondary battery inside. The SOC estimation unit 3 and the temperature measurement unit 4 of at least one secondary battery are included. The voltage and capacity of the secondary battery may be different. As the temperature measurement unit 4, for example, a thermistor or a thermocouple is used. The secondary battery SOC estimation unit 3 estimates the remaining battery energy (SOC: State of Charge) using the cell voltage, the battery conduction current, the temperature, and the like.

  The load device 5 is supplied with power from the secondary battery or from the charger 8. The load device 5 includes a power converter such as an inverter that converts DC power into AC power and a DC / DC converter that changes DC voltage. The charger / discharger 6 exchanges electric power between the first secondary battery 2a and the second secondary battery 2b. The charger / discharger 6 includes a semiconductor switch inside, and changes output power and current by changing switching timing. Moreover, in FIG. 1, although the charger / discharger 6 is one, it may combine a unidirectional converter. Furthermore, the charger / discharger 6 includes a battery current measuring unit 12 that measures the current of the secondary battery and a battery voltage measuring unit 13 that measures the voltage of the secondary battery.

  The charger / discharger control device 7 supplies electrical energy to the load device 5, a temperature increase command unit 9 that instructs the charger / discharger 6 to start temperature increase, a charger / discharger controller 10 that controls charging / discharging of the charger / discharger 6, and the like. Is included.

  The charger / discharger 6 starts from the temperature rise start command from the temperature rise command unit 9 of the charger / discharger control device 7 or the temperature measured by the temperature measurement unit 4 of the secondary battery is lower than a predetermined temperature. The temperature / charge operation starts and the secondary battery SOC estimation unit 3 alternately turns the secondary battery into a secondary battery by the charger / discharger 6 so that the SOC estimated by the charger / discharger controller 7 described later becomes a target SOC. Apply pulse current. The pulse time may be a fixed value (for example, 40 sec), or may be stopped when the battery voltage falls outside the use voltage range of each secondary battery. However, when such pulse charge / discharge is performed without managing the SOC, even if the temperature of the battery rises, it may not reach the SOC required to obtain the desired output. It may take time to adjust the SOC.

  Below, in order to solve this problem, the charging / discharging control process which the charger / discharger control part 10 of the charger / discharger controller 7 performs is demonstrated using FIG.2 and FIG.3. The SOC of the secondary battery necessary to obtain a desired output is determined according to the temperature of the secondary battery itself. Generally, the lower the temperature, the higher the SOC is required, and the higher the temperature, the lower the required SOC. Show a tendency to If the SOC has reached the SOC required to obtain a desired output at a predetermined temperature, the secondary battery is in a high output possible region, and otherwise is in a high output impossible region. To do.

  FIG. 2 is a diagram illustrating an example of the high output possible region and the high output impossibility region of each of the two secondary batteries 2a and 2b in a low temperature environment (for example, −30 ° C.), and target SOC straight line setting. In this case, the SOC required to obtain a desired output in a low temperature environment is 80% for any secondary battery. The high output possible area 16 is represented by a portion other than the high output impossible area 14 of the first secondary battery 2a and the high output impossible area 15 of the second secondary battery 2b. In the case of FIG. 2, a straight line connecting the intersection P <b> 1 between the two high output impossibility regions 14 and 15 and the point where the SOC of the two batteries is 0% is represented as a target SOC straight line 17. The SOC of the secondary battery may not be constant depending on the charging current of the charger 8 during the temperature raising operation or the current consumption of the load device 5, but the secondary SOC can be obtained by making the target SOC straight in this way. Even if the SOC of the battery changes, the target SOC can be successively changed on this straight line.

  FIG. 3 shows an example of the temperature raising operation starting from the time of low temperature (for example, the above-described −30 ° C.). It is assumed that the SOC state of the two sets of secondary batteries at the start of temperature increase is P2 (SOC of the first secondary battery 2a = 5%, SOC of the second secondary battery 2b = 70%). When the input / output of energy from the outside, the conversion loss of the charger / discharger 6 and the heat loss of the secondary battery are ignored for the two secondary batteries, the SOC of the first secondary battery 2a + the second secondary battery 2b SOC = constant value. Then, charge / discharge control is performed between the secondary batteries so that the SOC of each secondary battery becomes a value on the target SOC straight line 17 while maintaining the constant value of the SOC. In the case of FIG. 3, the second secondary battery 2b is discharged to the first secondary battery 2a. In addition, in the charge / discharge control at this time, charge / discharge is not switched until the target SOC is reached unless the battery voltage exceeds the operating voltage of the secondary battery. As a result, the SOC of each secondary battery moves from P2 in FIG. 3 toward the target SOC straight line 17 while raising the temperature in the direction of the arrow.

  Once the target SOC is reached, the pulse charge / discharge width is set to a constant value (for example, 40 s), and the charge / discharge operation is continued to increase the temperature further to an expected value. If this pulse width is large, the target SOC line is separated, and if it is too short, a sufficient temperature rise effect cannot be obtained. From these relationships, it is more effective to set ΔSOC.

  As described above, according to the first embodiment, since the temperature is increased by charge / discharge control while managing the target SOC of each secondary battery, each secondary battery is necessary to obtain a desired output. The temperature is increased while ensuring a sufficient SOC. Therefore, there is no need to readjust the SOC after the temperature rise, and the time from the start of the temperature rise of the secondary battery until it can be used can be shortened.

(Second Embodiment)
When the battery temperature rises due to the characteristics of the secondary battery, the high output impossible area of the secondary battery decreases. Moreover, the temperature rise of both secondary batteries changes with battery structures, installation locations, cooling environments, remaining battery levels, and the like. Therefore, in order to reach the high output possible region in a shorter time, it is desirable to change the target SOC according to the temperature rise.

  FIG. 4 shows an example of characteristics when the first secondary battery 2a is −20 ° C. and the second secondary battery 2b is −10 ° C. Assuming that the target SOC when both secondary batteries 2a and 2b start to rise from −30 ° C. is P4, the first secondary battery 2a is −20 ° C., and the second secondary battery 2b is −10 ° C. When the target SOC straight line is calculated so as to pass through P3 from the difference in the high output impossibility region between the first secondary battery 2a and the second secondary battery 2b, the target value newly changes. . The update timing of the target value may be updated every time when the SOC difference between the current target value and the updated target value is a predetermined value or more, or every fixed time from the start of temperature increase.

(Third embodiment)
FIG. 5 shows the temperature rise effect characteristic by SOC. In FIG. 5, a large temperature increase effect region 19 can obtain a large temperature increase effect by flowing a large current for a certain period of time when the battery is heated. On the other hand, the temperature increase effect is low in the low temperature increase effect region 18 composed of an extremely high SOC region and an extremely low region. If these characteristics are acquired in advance by a test or the like, the temperature can be increased more efficiently.

  A method of setting the target SOC when considering the characteristics of FIG. 5 will be described with reference to FIG. According to the first embodiment, the target SOC straight line 17 is represented by a straight line passing through P6. However, in the third embodiment, when the SOC before the temperature rise is at P5, the intersection of P5 and the high output impossible region As for the target SOC calculated from the above, a straight line passing through P7 is set as a target SOC straight line.

(Fourth embodiment)
The fourth embodiment will be described with reference to FIG. When only the output of any one of the load devices 5 is excessively large, power can be supplied using the charger / discharger 6. In the voltage control unit 102 of FIG. 7, the voltage of the first secondary battery 2a is acquired, and a current command value to be input to the current control unit 104 through the PI controller is calculated as a difference from the voltage command value 101. When the voltage of the first secondary battery 2a is low, the charging current from the second secondary battery 2b to the first secondary battery 2a can be increased by setting the voltage command value 101 high. . The limiter 103 limits the current value calculated by the voltage control unit 102 so that a value greater than a certain current does not flow, and can determine the maximum value of the current supply amount. In the current control unit 104 in FIG. 7, the difference between the current flowing through the first secondary battery 2 a and the current command value obtained from the voltage control unit 101 is input to the gate signal generation unit 105 by the PI controller. Thus, a switching signal to the semiconductor device that generates a desired current can be generated.

  In this way, the change in the temperature rise possible region when the SOC required for obtaining a desired output after the temperature rise is smaller in the first secondary battery 2a than in the second secondary battery 2b is shown. 8 will be used for explanation. When the first secondary battery 2a and the second secondary battery 2b are in the high output possible region 16 when the battery temperature is −30 ° C. as shown in FIG. When the power is interchanged, the high output possible area 16 changes as shown in FIG. Since it is assumed that electric power is supplied from the first secondary battery 2a to the second secondary battery 2b, the target SOC of the first secondary battery 2a is lowered and the target of the second secondary battery 2b is reduced. The SOC needs to be increased. Accordingly, the high output impossible area 14 of the first battery 2a decreases, and the high output impossible area 15 of the second secondary battery 2b increases.

  Since this ratio can be set by the current command value limiter 103, when the second secondary battery 2b is not used, the maximum limit can be set as large as possible. Since the current that can be output by the second secondary battery 2b varies depending on the SOC and temperature, it is desirable to set the current using a table in which battery characteristics are acquired in advance. As described above, any output of the secondary battery can be made larger than the original battery capacity without increasing the temperature. Assuming that power can be accommodated in one side at the time of output, it is effective to change the target SOC straight line so as to pass through P8 in FIG.

  Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Secondary battery cell, 2a ... 1st secondary battery, 2b ... 2nd secondary battery, 3 ... Secondary battery SOC estimation part, 4 ... Temperature measurement part, 5 ... Load apparatus, 6 ... Charge / discharge device , 7: Charger / discharger control device, 8 ... Charger, 9 ... Temperature increase command unit, 10 ... Charger / discharger control unit, 11 ... Load output command unit, 12 ... Battery current measurement unit, 13 ... Battery voltage measurement unit, 14 ... High output impossible area of battery 1, 15 ... High output impossible area of battery 2, 16 ... High output possible area of first secondary battery and second secondary battery, 17 ... Target SOC straight line, 18 ... Low Temperature increase effect region, 19 ... High temperature increase effect region.

Claims (6)

An apparatus for controlling a first secondary battery and a second secondary battery,
Charging / discharging means for connecting the first and second secondary batteries and charging the other secondary battery with electric power discharged by the one secondary battery;
First SOC estimating means for estimating the SOC of the first secondary battery;
Second SOC estimating means for estimating the SOC of the second secondary battery;
A straight line representing a target SOC is determined based on the SOC regions that can be output from the first and second secondary batteries acquired in advance, and the SOC estimated by the first and second SOC estimation means is on the straight line. And a charging / discharging control means for controlling the charging / discharging means so as to achieve a target SOC of the secondary battery.   The secondary battery control device according to claim 1, wherein the charge / discharge control unit performs charge / discharge within a certain SOC range from the target SOC.   3. The secondary battery control device according to claim 1, wherein the charge / discharge control unit further changes the straight line in accordance with an increase in temperature of the first and second secondary batteries.   4. The secondary battery control device according to claim 1, wherein the charge / discharge control unit changes the straight line in accordance with a low temperature increase effect region acquired in advance. 5.   The charge / discharge control means further controls the charge / discharge means to supply power from the first or second secondary battery to the other secondary battery. A secondary battery control device according to claim 1.   The charge / discharge control means changes the SOC region that can be output from the first and second secondary batteries when power is supplied to the other secondary battery, and the straight line based on the changed SOC region. The secondary battery control device according to claim 5, further characterized in that:

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