JP6546554B2 - Power storage system - Google Patents

Description

  The present invention relates to a storage system including a plurality of storage elements connected in parallel.

  DESCRIPTION OF RELATED ART In the electrical storage system provided with electrical storage elements, such as a secondary battery and an electrical double layer capacitor, in order to make the electric power output with respect to load increase, the structure which connects an electrical storage element in parallel is known. Here, it is conceivable that internal resistances of a plurality of storage elements connected in parallel have different values due to deterioration or the like. In this case, assuming that an output voltage of the storage system is Vout, an open end voltage of each storage element is Vop, and an internal resistance of each storage element is Rin, a current amount In flowing through each storage element is In = (Vout-Vop) / It will be Rin.

  That is, the amount of current flowing to each storage element differs according to the inverse ratio of the internal resistance, and a large current flows in the storage element having a small internal resistance as compared to other storage elements. Therefore, the current flowing to the storage element having a small internal resistance may reach the allowable upper limit, or the state of charge (SOC) may reach the lower limit (for example, 0%) earlier than the other storage elements. Conceivable.

  Therefore, in a storage device in which a series storage element group in which storage elements are connected in series is connected in parallel, a variable resistance circuit is connected in series to each series storage element group to measure the amount of current flowing in each series storage element group Patent Document 1 discloses an arrangement for adjusting

Patent 5342860

  Here, in the configuration disclosed in Patent Document 1, a variable resistance circuit is used for storage elements connected in parallel (hereinafter, “the series storage element group” is included in “the storage element” in the present specification). The variable resistance circuit is connected in series to constantly adjust the amount of current flowing to the storage element. That is, power consumption always occurs in the variable resistance circuit.

  The present invention has been made in view of the above problems, and has a configuration capable of bringing the charging rates of storage elements closer to one another while performing charging and discharging, and further reducing power consumption in a variable resistance circuit. The main purpose is to provide a possible configuration.

  This configuration is a storage system (10) including a plurality of storage elements (C1, C2) connected in parallel, and variable resistance circuits (R1, R2) connected in series to the storage elements and having variable resistance values. And setting the resistance value of all the variable resistance circuits to a minimum when the charging rate of all the storage elements is equal to or greater than a first predetermined value at the time of discharging the storage system, and the plurality of storage elements When one of the charging rates is less than the first predetermined value, the smaller the charging rate of the storage element is, the smaller the discharge current flows to the storage element, and the resistance value of the variable resistance circuit is set. Discharge control, and setting the resistance value of all the variable resistance circuits to a minimum when the charging rates of all the storage elements are equal to or less than a second predetermined value during charging of the storage system. When the charging rate of any of the plurality of storage elements is larger than the second predetermined value, the resistance of the variable resistance circuit is set such that a smaller charging current flows to the storage element as the charging rate of the storage element is larger. A control unit (50) for performing at least one control of charging control for setting each value is characterized.

  According to the above configuration, when the charge rate of any one of the plurality of storage elements is less than the first predetermined value during discharging of the storage system, a smaller discharge current flows to the storage element as the charge rate decreases. The resistance value of the variable resistance circuit is set. This makes it possible to approximate the charging rate of the storage element while discharging. In addition, when the charging rates of all the storage elements are equal to or greater than the first predetermined value, all the variable resistance circuits are set to the minimum value, so that power consumption in the variable resistance circuits can be reduced.

  Similarly, at the time of charging of the storage system, when the charging rate of any one of the plurality of storage cells is larger than the second predetermined value, the variable resistance circuit flows such that a smaller charging current flows to the storage cell as the charging rate increases. The resistance value of is set. This makes it possible to approximate the charging rate of the storage element while performing charging. In addition, when the charging rates of all the storage elements are equal to or less than the second predetermined value, all the variable resistance circuits are set to the minimum value, and therefore power consumption in the variable resistance circuits can be reduced.

  That is, according to the above configuration, while performing charging and discharging, it is possible to approximate each charging rate of the storage element, and further, it is possible to reduce power consumption in the variable resistance circuit.

The electric block diagram of 1st Embodiment. The conceptual diagram showing discharge allowable electric power and charge allowable electric power. The figure showing the charge rate dependence and temperature dependence of discharge allowable power. The figure showing the charge rate dependence and temperature dependence of charge allowable power. FIG. 7 is a diagram showing a charging rate calculation process of the first embodiment. FIG. 7 is a diagram showing resistance value setting processing of the variable resistance circuit of the first embodiment. The electrical block diagram of 2nd Embodiment. The figure showing the charge rate calculation process of 2nd Embodiment.

First Embodiment
FIG. 1 shows the electrical configuration of the storage system of the present embodiment. The storage system 10 includes a battery pack 11. Specifically, power storage system 10 is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and performs power supply from assembled battery 11 to a load 100 such as a motor mounted on the vehicle. In addition, the storage system 10 performs charging of the assembled battery 11 by being supplied with power from the power supply 101. Specifically, the power supply 101 is a commercial power supply outside the vehicle, a generator mounted on the vehicle, or the like.

  The assembled battery 11 includes a battery group C1 in which a plurality of battery cells C11 to C18 are connected in series and a battery group C2 in which a plurality of battery cells C21 to C28 are connected in series. The battery group C1 and the battery group C2 are It is connected in parallel. The battery groups C1 and C2 are provided with cooling devices 21 and 22 for cooling the battery groups C1 and C2, respectively. Specifically, the cooling devices 21 and 22 are cooling fans. In the present embodiment, the battery groups C1 and C2 correspond to "electric storage elements". Battery cells C11 to C18 and C21 to C28 are lithium ion secondary batteries, respectively.

  In the present embodiment, variable resistance circuits R1 and R2 are connected in series to battery groups C1 and C2, respectively, and then connected in parallel. The variable resistance circuits R1 and R2 are connected to a plurality of resistance elements R11 to R15 and R21 to R25 connected in series and switches SW11 to SW15 and SW21 to SW25 connected in parallel to the resistance elements R11 to R15 and R21 to R25, respectively. It is configured.

  The switches SW11 to SW15 and SW21 to SW25 are each a semiconductor switching element, and more specifically, a MOS-FET. When the switches SW11 to SW15 and SW21 to SW25 are turned on, the current flowing through the resistance elements R11 to R15 and R21 to R25 connected in parallel bypasses the switches SW11 to SW15 and SW21 to SW25, and the variable resistance The resistance values of the circuits R1 and R2 change. When all the switches SW11 to SW15 are turned on, the resistance value of the variable resistance circuit R1 becomes the minimum value (approximately 0), and when all the switches SW21 to SW25 are turned on, the resistance of the variable resistance circuit R2 The value is the minimum value (approximately 0).

  In addition, the storage system 10 includes a current sensor 31 for detecting the charge / discharge current I flowing through the assembled battery 11, a voltage sensor 32 for detecting the output voltage V of the storage system 10, and a temperature sensor for detecting the temperatures of the battery groups C1 and C2. 41 and 42 are provided. The output of each sensor 31, 32, 41, 42 is input to the control unit 50. The current sensor 31 is, for example, a Hall element. The voltage sensor 32 is, for example, an analog-to-digital converter that converts a voltage value from an analog value to a digital value. The temperature sensors 41 and 42 are, for example, temperature sensitive resistors.

  The control unit 50 sets the resistance values of the variable resistance circuits R1 and R2 by performing on / off control of the switches SW11 to SW15 and SW21 to SW25 based on the detection values of the sensors 31, 32, 41, and 42. The charge and discharge currents I1 and I2 flowing to the groups C1 and C2 are adjusted. The control unit 50 also controls the cooling devices 21 and 22. Hereinafter, control by the control unit 50 will be described.

  At the time of discharge of power storage system 10, control unit 50 sets resistance values of variable resistance circuits R1 and R2 when both charging rates SOC1 and SOC2 of battery groups C1 and C2 are equal to or greater than a predetermined value (first predetermined value). Set each to the minimum (approximately 0). Furthermore, control unit 50 determines that the battery group with the smaller charging rate is used, when both of charging rates SOC1, SOC2 of battery groups C1, C2 are less than the predetermined value (first predetermined value) at the time of discharging power storage system 10. The resistance values of the variable resistance circuits R1 and R2 are set so that a small discharge current flows to the battery group. More specifically, for example, when the charge ratio SOC1 is 20% and the charge ratio SOC2 is 10%, the ratio of the current I1 flowing to the battery group C1 to the current I2 flowing to the battery group C2 is I1: I2 = 2 The resistance values of the variable resistance circuits R1 and R2 are set so as to be 1: respectively. As a result, at the time of discharge, both of the charge rates SOC1 and SOC2 can be made 0%. The charge rate is the ratio of the current capacity to the full charge capacity of each of the battery groups C1 and C2.

  In addition, when both of charging rates SOC1 and SOC2 of battery groups C1 and C2 are equal to or less than a predetermined value (second predetermined value) during charging of storage system 10, the resistance values of variable resistance circuits R1 and R2 are respectively minimized Set to approximately 0). Furthermore, when charging rates SOC1 and SOC2 of battery groups C1 and C2 are both greater than the predetermined value (second predetermined value) during charging of power storage system 10, control unit 50 determines that the battery group having the higher charging rate is higher. The resistance values of the variable resistance circuits R1 and R2 are set so that a small charging current flows to the battery group. More specifically, for example, when the charge ratio SOC1 is 80% and the charge ratio SOC2 is 90%, the ratio of the current I1 flowing to the battery group C1 to the current I2 flowing to the battery group C2 is I1: I2 = 2 The resistance values of the variable resistance circuits R1 and R2 are set so as to be 1: respectively. As a result, at the time of charging, both the charging rates SOC1 and SOC2 can be made 100%.

  Next, using FIGS. 2 to 4, discharge allowable powers Wom1 and Wom2 that are permitted to be discharged from each battery group C1 and C2 and charging to each battery group C1 and C2 are permitted. The charge allowable power Wim1 and Wim2 will be described. Note that only the discharge allowable power Wom1 and the charge allowable power Wim1 of the battery group C1 will be described, and the discharge allowable power Wom2 and the charge allowable power Wim2 of the battery group C2 will be the discharge allowable power Wom1 and the charge allowable power Wim1 of the battery group C1. The description is omitted because it is the same as the above.

  FIG. 2 shows the relationship between the inter-terminal voltage CCV1 of the battery group C1 and the charge / discharge current I1. When the charge / discharge current I1 is 0, the inter-terminal voltage CCV1 matches the open end voltage OCV1.

  When discharging from battery group C1 to load 100, charge / discharge current I1 becomes a positive value, and at terminal voltage CCV1, the product of internal resistance Ri1 of battery group C1 and charge / discharge current I1. A voltage drop corresponding to the voltage occurs. Here, when the charge / discharge current I1 reaches the predetermined value Th1, the inter-terminal voltage CCV1 becomes the lower limit value Vmin of the inter-terminal voltage CCV1. Here, specifically, the lower limit value Vmin is a value set based on the operation lower limit voltage of the load 100. The area (a) shown in FIG. 2 corresponds to the discharge allowable power Wom1, and Wom1 = Vmin · Th1.

  Here, the internal resistance Ri1 of the battery group C1 is a value determined according to the charging rate SOC1 and the temperature T1. The open end voltage OCV1 of the battery group C1 is a value determined according to the charging rate SOC1. The predetermined value Th1 is a value determined according to the internal resistance Ri1, the open end voltage OCV1, and the lower limit value Vmin (Th1 = (OCV1−Vmin) / Ri1). Therefore, discharge allowable power Wom1 is a value determined according to charging rate SOC1 and temperature T1.

  FIG. 3 is a diagram showing the relationship between discharge allowable power Wom1, charging rate SOC1 and temperature T1. As open-circuit voltage OCV1 decreases in accordance with the decrease in charging rate SOC1, discharge allowable power Wom1 decreases. Further, as the internal resistance Ri1 increases according to the decrease in the temperature T1, the discharge allowable power Wom1 decreases.

  Returning to the explanation of FIG. 2, when charging is performed from the battery group C1 to the power supply 101, the charge / discharge current I1 becomes a negative value, and at the terminal voltage CCV1, the internal resistance Ri1 of the battery group C1 and the charge / discharge A voltage increase corresponding to the product of the current I1 occurs. Here, when the charge / discharge current I1 reaches the predetermined value Th2, the inter-terminal voltage CCV1 becomes the upper limit value Vmax of the inter-terminal voltage CCV1. Here, specifically, the upper limit value Vmax is a value set based on the operation upper limit voltage of the load 100. The area (b) shown in FIG. 2 corresponds to the charge allowable power Wim1, and Wim1 = OCV1 · Th2.

  Similar to the discharge allowable power Wom1, the charge allowable power Wim1 is a value determined according to the charge ratio SOC1 and the temperature T1. That is, the internal resistance Ri1 of the battery group C1 is a value determined according to the charging rate SOC1 and the temperature T1. The open end voltage OCV1 of the battery group C1 is a value determined according to the charging rate SOC1. The predetermined value Th2 is a value determined according to the internal resistance Ri1, the open end voltage OCV1, and the upper limit value Vmax (Th2 = (Vmax−OCV1) / Ri1).

  FIG. 4 is a diagram showing the relationship between the charge allowable power Wim1, and the charging rate SOC1 and the temperature T1. In response to the increase of the charging rate SOC1, the open circuit voltage OCV1 is increased, whereby the charge allowable power Wim1 is decreased. Further, the charge allowable power Wim1 decreases due to the increase of the internal resistance Ri1 according to the decrease of the temperature T1.

  Thus, control unit 50 stores in advance a map (FIG. 3) representing the relationship between discharge allowable power Wom1, charging rate SOC1 and temperature T1, and based on the map and charging rate SOC1 and temperature T1. The discharge allowable power Wom1 can be calculated. Further, control unit 50 stores in advance a map (FIG. 4) representing the relationship between charge allowable power Wim1, charging rate SOC1 and temperature T1, and based on the map and charging rate SOC1 and temperature T1, charging is performed. Allowable power Wim1 can be calculated. The value of the internal resistance Ri1 may not be used when calculating the discharge allowable power Wom1 and the charge allowable power Wim1.

  Hereinafter, a method of creating a map representing the relationship between discharge allowable power Wom1, charging rate SOC1 and temperature T1 will be described. After setting the charging rate SOC1 and the temperature T1 to predetermined values, when a constant current is supplied to the battery group C1 for a predetermined discharge execution time To, a current value that reaches the lower limit value Vmin is acquired. The value of the product of the acquired current value and lower limit value Vmin is acquired as discharge allowable power Wom1. Then, a map representing the correspondence between the values of the charging rate SOC1 and the temperature T1 and the values of the allowable discharge power Wom1 is created.

  In addition, a map generation method will be described that represents the relationship between the charge allowable power Wim1, the charging rate SOC1, and the temperature T1. When a constant current is supplied to the battery group C1 for a predetermined charging time Ti, a current value that reaches the upper limit value Vmax is acquired. A value of the product of the acquired current value and the open end voltage OCV1 is acquired as the charge allowable power Wim1. Then, a map representing the correspondence between each value of charging rate SOC1 and temperature T1 and the value of charging allowable power Wim1 is created.

  Here, as shown in FIG. 3, it is feared that discharge allowable power Wom1 decreases with the decrease of the charging rate SOC1 due to discharge and becomes smaller than discharge power Wo1. When discharge allowable power Wom1 becomes smaller than discharge power Wo1, the voltage supplied to load 100 becomes lower than lower limit voltage Vmin, causing problems such as the operation of load 100 becoming unstable.

  Further, as shown in FIG. 4, it is feared that the charge allowable power Wim1 decreases with the increase of the charging rate SOC1 due to charging and becomes smaller than the charge power Wi1. Since the charge allowable power Wim1 is smaller than the charge power Wi1, the inter-terminal voltage CCV1 of the battery group C1 becomes higher than the upper limit voltage Vmax, causing problems such as the operation of the load 100 becoming unstable.

  Therefore, in the present embodiment, when at least one of battery groups C1 and C2 allows discharge allowable powers Wom1 and Wom2 to be lower than discharge powers Wo1 and Wo2 discharged from battery groups C1 and C2, charging rate SOC1, SOC2 is lower. It is determined that the SOC2 is less than a predetermined value (first predetermined value), and the current adjustment control is performed. When at least one of battery groups C1 and C2 has charge allowable powers Wim1 and Wim2 below charging powers Wi1 and Wi2 charged from battery groups C1 and C2, charging rates SOC1 and SOC2 have predetermined values ( It is determined that the value is larger than the second predetermined value, and the current adjustment control is performed.

  FIG. 5 is a flowchart showing the process of calculating the charging rates SOC1 and SOC2 of the battery groups C1 and C2. The said process is implemented by the control part 50 for every predetermined period.

  In step S01, it is determined whether or not the storage system 10 is charging / discharging. When the storage system 10 is not charging / discharging (S01: NO), it is suitable to acquire the detected value of the output voltage V by the voltage sensor 32 as the open end voltages OCV1 and OCV2 of the respective battery groups C1 and C2 in step S02. It is determined whether the situation is Here, the condition suitable for obtaining as the open end voltage of each of the battery groups C1 and C2 is specifically the difference between the open end voltage OCV1 of the battery group C1 and the open end voltage OCV2 of the battery group C2. The value is substantially zero, and no current flows between the battery groups C1 and C2, and the polarization of the battery groups C1 and C2 is relaxed.

  If the condition is suitable for acquiring the open end voltages OCV1 and OCV2 of the battery groups C1 and C2 (S02: YES), in step S03, the detection value of the output voltage V by the voltage sensor 32 is The open end voltages OCV1 and OCV2 of C2 are acquired, and in step S04, based on the acquired open end voltages OCV1 and OCV2 and a map representing the correspondence between the open end voltage and the charging rate, The charging rates SOC1 and SOC2 are calculated, and the process ends. If the condition is not suitable for acquiring the open end voltages OCV1 and OCV2 of the battery groups C1 and C2 (S02: NO), the process is ended.

  If the storage system 10 is charging / discharging (S01: YES), in step S05, the previous values of the charging rates SOC1, SOC2 of the battery groups C1, C2 are acquired. In step S06, detection values of temperatures T1 and T2 of the battery groups C1 and C2 are acquired. In step S07, the detection value of the charge / discharge current I of the battery pack 11 by the current sensor 31 and the detection value of the output voltage V by the voltage sensor 32 are acquired. In step S 08, open end voltages OCV 1 and OCV 2 of each of battery groups C 1 and C 2 are calculated based on the charging rates SOC 1 and SOC 2 of each of battery groups C 1 and C 2 and the map representing the correspondence between the charging rate and the open end voltage. Do.

  In step S09, based on the charging rates SOC1 and SOC2 of the battery groups C1 and C2, the temperatures T1 and T2 of the battery groups C1 and C2, and the maps representing the charging rates and the correspondence between the temperature and the internal resistance, The internal resistances Ri1 and Ri2 of the battery groups C1 and C2 are calculated. Furthermore, internal resistances Ri1 and Ri2 of the battery groups C1 and C2 are calculated based on the capacity maintenance rates of the battery groups C1 and C2. Here, the capacity retention rate is a value representing the ratio of the full charge capacity to the current value of the full charge capacity to the initial value, and deterioration of each of the battery groups C1 and C2 (battery cells C11 to C18 and C21 to C28). Is a value representing Specifically, based on the capacity maintenance rates of the battery groups C1 and C2, a map representing the correspondence between the charging rate and the temperature and the internal resistance is switched.

  In step S10, based on open end voltages OCV1 and OCV2 of respective battery groups C1 and C2, charge / discharge current I of assembled battery 11, and internal resistances Ri1 and Ri2 of respective battery groups C1 and C2, respective battery groups C1 and C2 are obtained. The charge / discharge currents I1 and I2 flowing to C2 are calculated. In step S11, by adding the change amounts ΔSOC1 and ΔSOC2 of the charging rate calculated from the charging and discharging currents I1 and I2 to the previous values of the charging rates SOC1 and SOC2 of the battery groups C1 and C2, the current charging rate Calculate the value and finish the process.

Here, the method of calculating the charge / discharge currents I1 and I2 flowing to the respective battery groups C1 and C2 in step S10 will be described in detail. The charge and discharge currents I1 and I2 are
I = I1 + I2
It has a relationship of Furthermore, the voltage V1 across the terminals of the series connection of the battery group C1 and the variable resistance circuit R1 and the voltage V2 across the terminals of the series connection of the battery group C2 and the variable resistance circuit R2 are
V1 = OCV1−I1 · (Ri1 + R1)
V2 = OCV2−I2 · (Ri2 + R2)
It has a relationship of Here, since V1 = V2 = V, assuming that R1 = R2 = 0, the charge / discharge currents I1 and I2 are
I1 = (OCV1−OCV2 + I · Ri1) / (Ri1 + Ri2)
I2 = I-I1
It can be calculated as

Also, in step S11, the change rates ΔSOC1, ΔSOC2 of the charging rate are
ΔSOC1 = ∫I1 · dt / Af1
ΔSOC2 = ∫I2 · dt / Af2
It can be calculated as Here, Af1 and Af2 are full charge capacities of the respective battery groups C1 and C2.

  FIG. 6 shows a flowchart representing the output adjustment process of power storage system 10. The said process is implemented by the control part 50 for every predetermined period. Here, the predetermined cycle which is a cycle in which the output adjustment process is performed is set to a cycle shorter than the discharge execution time To used to obtain the allowable discharge powers Wom1 and Wom2. As a result, discharge powers Wo1 and Wo2 can be suppressed from temporarily exceeding discharge allowable powers Wom1 and Wom2. Similarly, a predetermined cycle which is a cycle in which the output adjustment process is performed is set to a cycle shorter than the charging execution time Ti used for acquiring the charge allowable powers Wim1 and Wim2. As a result, it is possible to suppress that the charging powers Wi1 and Wi2 temporarily exceed the charging allowable powers Wim1 and Wim2.

  In step S21, charging rates SOC1 and SOC2 of the battery groups C1 and C2 are acquired. In step S22, temperatures T1 and T2 of the battery groups C1 and C2 are acquired. In step S23, it is determined based on whether the charge / discharge current I is positive or negative, whether or not the assembled battery 11 is being discharged.

  If the battery pack 11 is discharging (S23: YES), in step S24, the charging rates SOC1, SOC2 of the battery groups C1, C2 and the temperatures T1, T2 of the battery groups C1, C2 and the charging rates SOC1, SOC2 And based on the map showing the relationship between temperature T1, T2 and discharge allowable electric power Wom1, Wom2 of each battery group C1, C2, discharge allowable electric power Wom1, Wom2 of each battery group C1, C2 is calculated.

  In step S25, charge / discharge currents I1 and I2 flowing through the battery groups C1 and C2 are acquired. In step S26, terminal voltages CCV1 and CCV2 of the battery groups C1 and C2 are calculated. In step S27, products of charge / discharge currents I1 and I2 and voltages across terminals CCV1 and CCV2 are calculated as discharge powers Wo1 and Wo2 currently discharged from the respective battery groups C1 and C2.

  In step S28, discharge powers Wo1 and Wo2 are compared with discharge allowable powers Wom1 and Wom2. If discharge allowable powers Wom1 and Wom2 are respectively equal to or higher than discharge powers Wo1 and Wo2 (S28: NO), the resistances of variable resistance circuits R1 and R2 are both set to 0 in step S29, and the process is ended.

If at least one of discharge allowable powers Wom1 and Wom2 is smaller than discharge powers Wo1 and Wo2 (S28: YES), target values I1 * and I2 * of currents suitable for flowing to respective battery groups C1 and C2 in step S30. Set Specifically, the target values I1 * and I2 * are set such that the ratio between the target value I1 * and the target value I2 * is the ratio between the charging rate SOC1 and the charging rate SOC2. Specifically, the target values I1 * and I2 * are expressed as I1 * = I · SOC1 / (SOC1 + SOC2)
I2 * = I · SOC2 / (SOC1 + SOC2)
Set as.

In step S31, values of variable resistance circuits R1 and R2 are set. If the currents I1 and I2 flowing to the battery groups C1 and C2 are regarded as OCV1 = OCV2, then
I1: I2 = Ri2 + R2: Ri1 + R1
It has a relationship of Also, target values I1 * and I2 * are
I1 *: I2 * = SOC1: SOC2
It has a relationship of

For this reason,
Ri1 + R1: Ri2 + R2 = SOC2: SOC1
The resistance values R1 and R2 of the variable resistance circuits R1 and R2 may be set so as to establish the following relationship. Specifically, while making one of R 1 and R 2 0, the other is a positive value,
R1 = 0, R2 = Ri1 · SOC1 / SOC2-Ri2 (> 0)
Or
R1 = Ri2 · SOC2 / SOC1−Ri1 (> 0), R2 = 0
Set as

  After step S31, control of the cooling devices 21 and 22 is performed in step S32. Specifically, the temperature of the battery group having the smaller charging rate (smaller target values I1 * and I2 * of the charging / discharging current) of the battery groups C1 and C2 is compared to the battery group having the larger charging rate. The cooling devices 21 and 22 are controlled to be low. After step S32, the process ends.

  If it is determined in step S23 that the battery pack 11 is not discharging (S23: NO), it is determined in step S33 whether the battery pack 11 is charging. If the battery pack 11 is not charging (S33: NO), the process is ended. If the assembled battery 11 is being charged (S33: YES), in step S34, the charging rates SOC1, SOC2 of the battery groups C1, C2 and the temperatures T1, T2 of the battery groups C1, C2 and the charging rates SOC1, SOC2 And based on the map showing the relationship between temperature T1, T2 and charge allowable power Wim1, Wim2 of each battery group C1, C2, charge allowable power Wim1, Wim2 of each battery group C1, C2 is calculated.

  In step S35, charge / discharge currents I1 and I2 flowing through the battery groups C1 and C2 are acquired. In step S36, the inter-terminal voltages CCV1 and CCV2 of the battery groups C1 and C2 are calculated. In step S37, products of charge / discharge currents I1 and I2 and inter-terminal voltages CCV1 and CCV2 are calculated as charge powers Wi1 and Wi2 currently discharged from the respective battery groups C1 and C2.

  In step S38, the charging powers Wi1 and Wi2 are compared with the charging allowable powers Wim1 and Wim2. If the charge allowable powers Wim1 and Wim2 are respectively equal to or higher than the charge powers Wi1 and Wi2 (S38: NO), the values of the variable resistance circuits R1 and R2 are both set to 0 in step S39, and the process is ended.

If at least one of charge allowable powers Wim1 and Wim2 is less than charge powers Wi1 and Wi2 (S38: YES), target values I1 * and I2 * of currents suitable for flowing to respective battery groups C1 and C2 in step S40. Set Specifically, the target values I1 * and I2 * are set such that the ratio of the target value I1 * to the target value I2 * is the ratio of “100−SOC1” to “100−SOC2”. Specifically, the target values I1 * and I2 * are expressed as I1 * = I · (100−SOC1) / (200−SOC1−SOC2)
I2 * = I. (100-SOC2) / (200-SOC1-SOC2)
Set as. In the above equation, SOC1 and SOC2 are expressed as percentages.

In step S41, values of variable resistance circuits R1 and R2 are set. If the currents I1 and I2 flowing to the battery groups C1 and C2 are regarded as OCV1 = OCV2, then
I1: I2 = Ri2 + R2: Ri1 + R1
It has a relationship of Also, target values I1 * and I2 * are
I1 *: I2 * = 100-SOC1: 100-SOC2
It has a relationship of For this reason,
Ri1 + R1: Ri2 + R2 = 100-SOC2: 100-SOC1
The resistance values R1 and R2 of the variable resistance circuits R1 and R2 may be set so as to establish the following relationship. Specifically, while making one of R 1 and R 2 0, the other is a positive value,
R1 = 0, R2 = Ri1 (100-SOC1) / (100-SOC2) -Ri2 (> 0)
Or
R1 = Ri2 · (100−SOC2) / (100−SOC1) −Ri1 (> 0), R2 = 0
Set as

  After step S41, control of the cooling devices 21 and 22 is performed in step S42. Specifically, the temperature of the battery group having the larger charging rate (smaller target values I1 * and I2 * of the charging and discharging current) among the battery groups C1 and C2 is lower than that of the battery group having the smaller charging rate. The cooling devices 21 and 22 are controlled to be low. After step S42, the process ends.

  The effects of this embodiment will be described below.

  According to the above configuration, when the charge rate SOC1, SOC2 of any of the plurality of battery groups C1, C2 is less than the predetermined value when the storage system 10 is discharged, the charge rate is larger than that of the battery groups C1, C2. The resistance values of the variable resistance circuits R1 and R2 are set such that a sufficiently large discharge current flows. This makes it possible to bring the charging rates SOC1, SOC2 of the battery groups C1, C2 close to each other while discharging. In addition, when the charging rates SOC1 and SOC2 of all the battery groups C1 and C2 are equal to or higher than a predetermined value, the resistance values of all the variable resistance circuits R1 and R2 are set to the minimum value (approximately 0). Power consumption in R1 and R2 can be reduced.

  Similarly, when charging rate SOC1, SOC2 of one of the plurality of battery groups C1, C2 is larger than the predetermined value during charging of storage system 10, the larger the charging rates SOC1, SOC2 with respect to battery groups C1, C2, The resistance values of the variable resistance circuits R1 and R2 are set such that a small charging current flows. This makes it possible to bring the charging rates SOC1, SOC2 of the battery groups C1, C2 close to each other while charging. In addition, when the charging rates of all the battery groups C1 and C2 are equal to or less than the predetermined value, the resistance values of all the variable resistance circuits R1 and R2 are set to the minimum value (approximately 0). Power consumption can be reduced.

  That is, according to the above configuration, it is possible to make the charging rates SOC1 and SOC2 of the battery groups C1 and C2 close to each other while performing charge and discharge, and further reduce the power consumption in the variable resistance circuits R1 and R2. is there.

  Specifically, compared to the configuration described in Patent Document 1 (Japanese Patent No. 5342860), the power efficiency is improved by 0.1% in the region where the temperature of the assembled battery 11 is about 10 ° C. at the time of discharge. In the region where the temperature of the battery 11 is about 0 ° C., the power efficiency is improved by 1.3%. In a low temperature range where the temperature of the assembled battery 11 is about 0 ° C., the values of the internal resistances Ri1 and Ri2 of the battery groups C1 and C2 become large, and it is necessary to increase the resistance value of the variable resistance circuits R1 and R2 There is. For this reason, in the low temperature region, the configuration of the present embodiment significantly improves the power efficiency as compared with the configuration in which the power adjustment by the variable resistor circuits R1 and R2 is always performed.

  In the configuration of the present embodiment, the resistance values of the variable resistance circuits R1 and R2 are set based on the charging rate and the internal resistances Ri1 and Ri2 of the battery groups C1 and C2. This makes it possible to simultaneously set the charging rates SOC1 and SOC2 to predetermined values (for example, 0%) at the time of discharging. Further, at the time of charging, it is possible to simultaneously set the charging rates SOC1 and SOC2 to predetermined values (for example, 100%).

  When the battery groups C1 and C2 deteriorate, the capacity retention rate decreases and the internal resistances Ri1 and Ri2 increase. Here, there is a correlation between the decrease in capacity retention rate and the increase in internal resistances Ri1 and Ri2. Therefore, in the present embodiment, the internal resistances Ri1 and Ri2 are calculated based on the capacity retention ratio.

  At the time of discharge, if at least one of battery groups C1 and C2 allows discharge allowable powers Wom1 and Wom2 to be lower than discharge powers Wo1 and Wo2 discharged from battery groups C1 and C2, charge rates SOC1 and SOC2 are predetermined. It is determined that the current value is less than the value, and the current adjustment control is performed. According to this configuration, discharge powers Wo1 and Wo2 can be prevented from exceeding discharge allowable powers Wom1 and Wom2. As a result, the output voltage V of the storage system 10 can be prevented from decreasing beyond the lower limit voltage Vmin, and the operation of the load 100 can be suppressed from becoming unstable.

  Further, at the time of charging, when at least one of battery groups C1 and C2 has charge allowable powers Wim1 and Wim2 smaller than charge powers Wi1 and Wi2 discharged from battery groups C1 and C2, charging rates SOC1 and SOC2 are Is determined to be larger than a predetermined value, and current adjustment control is performed. With this configuration, it is possible to suppress that the charging powers Wi1 and Wi2 exceed the charging allowable powers Wim1 and Wim2. Thus, the output voltage V of the storage system 10 can be prevented from rising beyond the upper limit voltage Vmax, and the operation of the load 100 can be suppressed from becoming unstable.

  The secondary battery has a characteristic that the internal resistance increases as the temperature is lower. Therefore, cooling is performed by the cooling devices 21 and 22 such that the temperatures of the battery groups C1 and C2 become lower as the battery groups C1 and C2 have smaller charging rates during discharge. This makes it possible to suppress the deterioration of the battery groups C1 and C2 accompanying the temperature rise, and to reduce the power consumption in the variable resistance circuits R1 and R2.

  Similarly, at the time of charging, cooling is performed by the cooling devices 21 and 22 such that the temperatures of the battery groups C1 and C2 decrease as the battery groups C1 and C2 having smaller charging rates decrease. This makes it possible to suppress the deterioration of the battery groups C1 and C2 accompanying the temperature rise, and to reduce the power consumption in the variable resistance circuits R1 and R2.

Second Embodiment
FIG. 7 shows an electrical configuration in the second embodiment. The same components as those in the electrical configuration of the first embodiment shown in FIG.

  In the configuration of the second embodiment, instead of the current sensor 31 for detecting the charge / discharge current I flowing to the assembled battery 11, the current sensors 31a and 31b for detecting the charge / discharge currents I1 and I2 flowing to the battery groups C1 and C2, respectively. It is provided.

  FIG. 8 is a flowchart showing the process of calculating the charging rate of the battery groups C1 and C2. The said process is implemented by the control part 50 for every predetermined period. The same processing as that of the first embodiment shown in FIG. 5 is denoted by the same reference numeral, and the description will be omitted.

  If the storage system 10 is charging / discharging (S01: YES), in step S05, the previous values of the charging rates SOC1, SOC2 of the battery groups C1, C2 are acquired. In step S12, detected values of the charge / discharge currents I1 and I2 are acquired from the current sensors 31a and 31b. Thereafter, in step S11, the charge ratio is calculated by adding the change amounts ΔSOC1 and ΔSOC2 of the charge ratio calculated from the charge and discharge currents I1 and I2 to the previous values of the charge ratios SOC1 and SOC2 of the respective battery groups C1 and C2. Calculate the current value of and finish the process.

  According to the configuration of the second embodiment, compared with the configuration of the first embodiment, the charging rates SOC1 and SOC2 of the battery groups C1 and C2 can be accurately calculated with a simple configuration. The configuration of the first embodiment can reduce the number of current sensors used as compared with the configuration of the second embodiment, and therefore can suppress an increase in the physical size of the storage system 10 and reduce the manufacturing cost. It is possible to

Third Embodiment
In step S31 of the flowchart shown in FIG. 6 of the first embodiment, the open end voltages OCV1 and OCV2 of the battery groups C1 and C2 are regarded as equal, and the resistance values R1 and R2 of the variable resistance circuits R1 and R2 are set. did. You may change this.

For example, under the condition that SOC1> SOC2 at the time of discharge and the resistance value R1 of the variable resistance circuit R1 is set to 0,
OCV1-I1.Ri1 = OCV2-I2 (Ri2 + R2) (1)
It has a relationship of here,
I = I1 + I2
Because equation (1) is
OCV1-I1.Ri1 = OCV2- (I-I1) (Ri2 + R2)
Can be deformed. further,
-(Ri1 + Ri2 + R2) I1 = OCV2-I (Ri2 + R2) -OCV1
The charge / discharge current I1 is
I1 = (OCV1-OCV2 + I (Ri2 + R2)) / (Ri1 + Ri2 + R2)
It can be expressed as. Furthermore, the charge / discharge current I2 is
I2 = I-I1
= (-OCV1 + OCV2 + I.Ri1) / (Ri1 + Ri2 + R2)
It can be expressed as.

Further, target values I1 * and I2 * of charge and discharge currents I1 and I2 are
I1 *: I2 * = SOC1: SOC2
It has a relationship of Therefore, in order to set the charge and discharge currents I1 and I2 to the target values I1 * and I2 *,
SOC1 · I2 = SOC2 · I1 (2)
The resistance value R2 of the variable resistor circuit R2 may be set to satisfy the following. That is, when the above I1 and I2 are substituted into the equation (2),
SOC1 · (−OCV1 + OCV2 + I · Ri1) / (Ri1 + Ri2 + R2) = SOC2 · (OCV1−OCV2 + I (Ri2 + R2)) / (Ri1 + Ri2 + R2)
And further deform,
SOC1 · (−OCV1 + OCV2 + I · Ri1) = SOC2 · (OCV1−OCV2 + I (Ri2 + R2))
And further deform,
(OCV1-OCV2 + I (Ri2 + R2)) = (SOC1 / SOC2). (-OCV1 + OCV2 + I.Ri1)
And further deform,
(Ri2 + R2) = 1 / I ((SOC1 / SOC2). (-OCV1 + OCV2 + I.Ri1)-(OCV1-OCV2))
It becomes.

Therefore, the resistance value R2 is
R2 = 1 / I ((SOC1 / SOC2). (-OCV1 + OCV2 + I.Ri1)-(OCV1-OCV2) -Ri2
Even if the open end voltages OCV1 and OCV2 of the battery groups C1 and C2 are largely different from each other, discharging is performed until both the charging rates SOC1 and SOC2 of the battery groups C1 and C2 become 0%. Becomes possible.

(Other embodiments)
-Although the number of the battery groups with which the assembled battery 11 is equipped is set to "2" in the said embodiment, it is good also as changing this and setting the number of a battery group to two or more arbitrary natural numbers. In addition, although the number of battery cells included in each of the battery groups C1 and C2 is “8”, the number of battery cells included in each of the battery groups may be changed to any natural number. In addition, although the number of resistance elements and switches included in each of variable resistance circuits R1 and R2 is “5”, the number of resistance elements and switches included in each of variable resistance circuits R1 and R2 may be changed to any natural number. .

  -"Electric storage element" may be replaced with a lithium ion secondary battery, and may be other secondary batteries such as a lead secondary battery or a nickel hydrogen secondary battery. Also, the "storage element" may be a single battery cell instead of the series connection of battery cells. Further, the "storage element" may be an electric double layer capacitor.

  The cooling devices 21 and 22 may be omitted. Further, the cooling device 21 may be a water cooling device using a liquid such as water as a refrigerant instead of the cooling fan (air cooling device).

  The configuration may be such that only one of the “discharge control” and the “charge control” is performed.

  -Although set as the structure which sets discharge allowable electric power Wom1 and Wom2 based on the operation lower limit voltage (lower limit value Vmin) of the load 100, you may change this. For example, discharge allowable powers Wom1 and Wom2 may be set based on the maximum values of the currents I1 and I2 flowing to the respective battery groups C1 and C2. Similarly, although the charge allowable powers Wim1 and Wim2 are set based on the operation upper limit voltage (upper limit value Vmax) of the load 100, this may be changed. For example, the charge allowable powers Wim1 and Wim2 may be set based on the maximum values of the currents I1 and I2 flowing to the respective battery groups C1 and C2.

  In the above embodiment, if at least one of battery groups C1 and C2 allows discharge allowable powers Wom1 and Wom2 to be lower than discharge powers Wo1 and Wo2 discharged from battery groups C1 and C2, charging rates SOC1 and SOC2 are obtained. Is determined to be less than a predetermined value, and current adjustment control is performed. This may be changed, the charging rates SOC1 and SOC2 may be compared with a predetermined value, and the current adjustment control may be performed when at least one of the charging rates SOC1 and SOC2 is less than the predetermined value. Alternatively, current adjustment control may be performed by comparing open end voltages OCV1 and OCV2 with a predetermined value and at least one of open end voltages OCV1 and OCV2 is lower than the predetermined value.

  Further, in the above embodiment, when at least one of battery groups C1 and C2 has charge allowable powers Wim1 and Wim2 lower than charge powers Wi1 and Wi2 charged in battery groups C1 and C2, charging rate SOC1, SOC2 is lower It is determined that the SOC2 is larger than a predetermined value, and the current adjustment control is performed. This may be changed to compare the charging rates SOC1 and SOC2 with a predetermined value, and the current adjustment control may be performed when at least one of the charging rates SOC1 and SOC2 is larger than the predetermined value. Alternatively, the open end voltages OCV1 and OCV2 may be compared with a predetermined value, and current adjustment control may be performed when at least one of the open end voltages OCV1 and OCV2 is larger than the predetermined value.

  In the above embodiment, the voltage sensor 32 detects the voltage (output voltage) of the series connection of the battery group C1 and the variable resistance circuit R1 and the series connection of the battery group C2 and the variable resistance circuit R2, and The charging rates SOC1 and SOC2 of the battery groups C1 and C2 are calculated based on the detected values. It is good also as composition provided with a voltage sensor which changes this and detects voltage between terminals of battery cells C11-C15 which constitute each battery group C1 and C2, and C21-C25, respectively. Furthermore, it is preferable to calculate the charging rate of each of the battery cells C11 to C15 and C21 to C25 based on the detection value of each voltage sensor. With such a configuration, it is possible to suppress the overdischarge and the overcharge in each of the battery cells C11 to C15 and C21 to C25 constituting each of the battery groups C1 and C2.

  In the above embodiment, the internal resistances Ri1 and Ri2 of the battery groups C1 and C2 are calculated using the same map during charging and discharging (FIG. 5: step S09). This may be changed, and the internal resistances Ri1 and Ri2 may be calculated using different maps at the time of charge and at the time of discharge. By calculating the internal resistances Ri1 and Ri2 using different maps during charging and discharging, it is possible to bring the SOCs of the respective battery groups C1 and C2 close to 100% with high accuracy during charging, At the time of discharge, it is possible to bring the SOCs of the respective battery groups C1 and C2 close to 0% with high accuracy. This makes it possible to increase the usable charge capacity of the battery pack 11.

  The discharge allowable power Wom1 and the charge allowable power Wim1 may be changed from those shown in FIG. For example, when the battery group C1 is discharged for a predetermined time, the charging rate SOC1 of the battery group C1 decreases with the discharge. As the charging rate SOC1 decreases, the open end voltage OCV1 decreases. The configuration may be such that discharge allowable power Wom1 is calculated in consideration of the decrease in open end voltage OCV1. Similarly, when charging is performed in the battery group C1 for a predetermined time, the charging rate SOC1 of the battery group C1 increases with charging. As the charging rate SOC1 increases, the open end voltage OCV1 increases. The charge allowable power Wim1 may be calculated in consideration of the increase of the open end voltage OCV1.

  10: storage system, 50: control unit, C1, C2: battery group, R1, R2: variable resistance circuit.

Claims (9)

A storage system (10) comprising a plurality of storage elements (C1, C2) connected in parallel, comprising:
Variable resistance circuits (R1 and R2) connected in series to the storage elements and having variable resistance values;
At the time of discharging of the storage system, when the charging rate of all the storage elements is equal to or more than a first predetermined value, the resistance value of all the variable resistance circuits is set to a minimum, and any of the plurality of storage elements Discharge control for setting the resistance value of the variable resistance circuit such that a smaller discharge current flows to the storage element as the state of charge of the storage element decreases, when the charging rate of the storage element is less than the first predetermined value When,
At the time of charging of the storage system, when the charging rate of all the storage elements is equal to or less than a second predetermined value, the resistance value of all the variable resistance circuits is set to a minimum, and any of the plurality of storage elements And charging control for setting the resistance value of the variable resistance circuit such that a smaller charging current flows to the storage element as the charging rate of the storage element is larger when the charging rate of the storage element is greater than the second predetermined value. ,
And a control unit (50) for performing at least one control of the above.   The variable resistance circuit includes one or more resistance elements (R11 to R15, R21 to R25), and switching elements (SW11 to SW15, SW21 to SW25) respectively connected in parallel with the resistance elements. The storage system according to claim 1, wherein the resistance value of the variable resistance circuit is set to a minimum by turning on all the switching elements.   The control unit performs the discharge control, and when the charge rate of any of the plurality of storage elements is less than the first predetermined value, each charge rate of the plurality of storage elements, and The power storage system according to claim 1, wherein a resistance value of the variable resistance circuit is set based on each internal resistance of the plurality of power storage elements.   The control unit performs the charge control, and when the charge rate of any one of the plurality of storage elements is larger than the second predetermined value, each charge rate of the plurality of storage elements, and The power storage system according to any one of claims 1 to 3, wherein a resistance value of the variable resistance circuit is set based on each internal resistance of a plurality of power storage elements.   The control unit is characterized in that, in each storage element, the internal resistance of the storage element is calculated based on a capacity maintenance ratio which is a value representing a ratio of the full charge capacity to the current value of the full charge capacity. The electrical storage system according to claim 3 or 4. The control unit implements the discharge control, and
In any one of the plurality of storage elements, the charging rate of any one of the plurality of storage elements is lower than the discharge power which is the discharge power from which the discharge is permitted. The storage system according to any one of claims 1 to 5, wherein the storage system is determined to be less than the first predetermined value. The control unit performs the charge control, and
In any one of the plurality of storage elements, the charging rate of any one of the plurality of storage elements is lower than the charging power with which the storage element is charged. The storage system according to any one of claims 1 to 6, wherein the storage system is determined to be larger than the second predetermined value. The storage system includes cooling devices (21, 22) for cooling the storage element for each of the plurality of storage elements,
The storage element is a secondary battery,
The control unit performs the discharge control, and when the charging rate of any of the plurality of storage cells is smaller than the first predetermined value, the smaller the charging rate of the storage cell, The storage system according to any one of claims 1 to 7, wherein the cooling device performs cooling so as to lower the temperature of the storage battery. The storage system includes cooling devices (21, 22) for cooling the storage element for each of the plurality of storage elements,
The storage element is a secondary battery,
The control unit executes the charge control, and when the charge rate of any of the plurality of storage elements is larger than the second predetermined value, the larger the charge rate of the storage element, the higher the storage element. The storage system according to any one of claims 1 to 8, wherein the cooling device performs cooling so as to lower the temperature of

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