JP6307992B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device in which a plurality of secondary batteries are connected in parallel and charging / discharging in the plurality of secondary batteries is performed.

  Conventionally, a power supply device having a plurality of storage batteries (secondary batteries) connected in parallel to each other has been put into practical use. In such a power supply device, when charging is performed by supplying power from the charging device, if the output voltage of each storage battery is different, current outflow (reverse flow) occurs in the storage battery on the high voltage side, and the storage battery on the low voltage side In addition to the charging current from the charging device, current flows from the storage battery on the high voltage side. As a result, excessive current flows through the storage battery on the low voltage side.

  In addition, when discharging from the above power supply device to an electric load, if the output voltage of each storage battery is different, an inflow of current (reverse flow) occurs in the storage battery on the low voltage side, and the storage battery on the high voltage side In addition to discharging to the battery, discharging to the low-voltage storage battery is also performed. As a result, excessive current flows through the storage battery on the high voltage side.

  In order to suppress the inflow of current from the storage batteries connected to each other in parallel to each other, a backflow prevention diode is connected in series to each storage battery, and a switch (opening / closing means) is connected in parallel to the diode. Technology has been proposed (Patent Document 1).

  In this case, the backflow prevention diode connected in series with the storage battery suppresses the backflow of current during charging or discharging, and the backflow prevention is achieved by opening and closing the switch according to the detected value of the voltage across each diode. The loss generated in the diode for use is reduced.

  More specifically, for example, when the output voltage of each storage battery is different at the time of discharging the power supply device, the switch on the low voltage storage battery side is opened and the switch on the high voltage storage battery side is closed. Prevent discharge from a voltage storage battery to a low voltage storage battery. And when the output voltage of each storage battery becomes substantially equal, all the switches are closed. Thereby, each storage battery is discharged uniformly.

JP-A-9-140065

  However, in the above technique, a current flows in the storage battery in which the switch is closed, and the current is stopped in the storage battery in which the switch is open. When the output voltage of each storage battery is detected under such circumstances, the open voltage (OCV) includes the voltage drop in the internal resistance of the storage battery as the output voltage of the storage battery whose switch is closed. A value is detected. Moreover, OCV is detected as an output voltage of the storage battery in which the switch is opened.

  That is, even if the detected values of the output voltages of both storage batteries are equal, the voltage drop in the internal resistance between the OCV of the storage battery in which the switch is closed and the OCV of the storage battery in which the switch is open It is thought that there is a voltage difference of minutes. For this reason, if the amount of current flowing through the electrical load or the amount of current flowing from the charging device decreases after both switches are closed on condition that the detected values of the output voltages of both storage batteries are equal, the difference in OCV between the two storage batteries. Therefore, there is a concern that a reverse flow from one storage battery to the other storage battery occurs.

  This invention is made | formed in view of the said subject, and it aims at providing the power supply device which can implement suitably charging / discharging about a some secondary battery.

  The present invention is a power supply device (10) including a plurality of secondary batteries (11, 12) connected in parallel to each other, and detects currents flowing through the plurality of secondary batteries during charging or discharging, respectively. A current detection means (41, 42); a diode (51-54) which is connected in series to each of the plurality of secondary batteries and prevents current backflow during charging or current discharge during discharging; The switching means (SW1 to SW4) connected in series to the secondary batteries and connected in parallel to the diodes, respectively, and one of the plurality of secondary batteries is selected as a charge / discharge target, By closing the open / close means connected in series to the secondary battery targeted for discharge, and opening the open / close means connected in series to the secondary battery not subject to charge / discharge First control means (20) for performing charging / discharging in the secondary battery as the charge / discharge target, a detected value of the current flowing through the secondary battery as the charge / discharge target, and not the charge / discharge target A current difference determination means (20) for determining whether or not a difference between a detected value of the current flowing in the secondary battery is equal to or less than a first threshold value, and a difference between the detected current values by the current difference determining means is the first threshold value. When it is determined that the secondary battery is not charged / discharged, the secondary battery is added as a charge / discharge target, and the opening / closing means connected in series to the added secondary battery is closed. And means (20).

  In the present invention, at the start of charging / discharging of the power supply device, any of the plurality of secondary batteries is subjected to charging / discharging. At that time, the open / close means connected in series to the secondary battery to be charged / discharged is closed to charge / discharge the secondary battery to be charged / discharged without causing power loss due to the diode. Can be implemented.

  After charging / discharging of the power supply device with one of the secondary batteries being charged / discharged and the other being not covered, the voltage between the terminals of the batteries is reduced as the voltage between the terminals of the secondary battery to be charged / discharged decreases. The voltage difference becomes smaller, and current begins to flow even on the non-target secondary battery side. Based on the current difference between the secondary batteries in this state, charging / discharging of the non-target secondary battery (turning on of the opening / closing means) is performed. Specifically, when the difference between the current flowing through the secondary battery that is the target of charging / discharging and the current flowing through the secondary battery that is not the target of charging / discharging is below the first threshold, A secondary battery is newly added as a charge / discharge target.

  In this case, the voltage difference between the terminals of both the secondary batteries is small and the current difference is also small, so the difference in the open voltage between the secondary batteries is also small. Therefore, even when both the opening / closing means are closed, the charging current flowing from the charging device to the power supply device is reduced or the load current flowing from the power supply device to the electric load is reduced. Therefore, it is possible to suppress the occurrence of reverse flow in which current flows.

The electrical block diagram in 1st Embodiment. The flowchart showing the discharge object selection process in 1st Embodiment. The flowchart showing the discharge object addition process in 1st Embodiment. The timing chart showing operation | movement of the power supply device in 1st Embodiment. The flowchart showing the discharge object exclusion process in 1st Embodiment. The figure showing the SOC-OCV characteristic of a lithium ion storage battery. The flowchart showing the discharge object selection process in 2nd Embodiment. The electrical block diagram in 3rd Embodiment. The flowchart showing operation | movement of the power supply device in 3rd Embodiment. The electrical block diagram in a modification.

(First embodiment)
The power supply device according to the first embodiment is an on-vehicle power supply device mounted on a vehicle such as an automobile, and supplies power to various on-vehicle electric loads when the vehicle travels. Moreover, the power supply device has a configuration including a plurality of storage batteries each including a storage battery, and each storage battery can be charged by supplying power from the on-vehicle power generation device when the vehicle is traveling. Further, in the present embodiment, the discharge is optimized in a state where electric power is supplied to an electric load using a plurality of storage batteries (that is, a discharge state). First, the electrical configuration of the power supply apparatus 10 will be described with reference to FIG. In particular, FIG. 1 shows a configuration related to the discharge of the power supply device 10.

  The power supply device 10 is connected to an electric load 100 having a resistance component 101 and a capacitance component 102, and supplies power to the electric load 100. The power supply device 10 includes a first storage battery 11 and a second storage battery 12. Both the storage batteries 11 and 12 are connected in parallel to each other and connected to the electric load 100. Both the storage batteries 11 and 12 are lithium ion storage batteries.

  Here, the electric load 100 is configured by connecting a plurality of driving loads (not shown) in parallel, and the load current Ia flowing through the electric load 100 varies depending on the driving state of the driving load. .

  Both storage batteries 11 and 12 are connected to shunt resistors 31 and 32, respectively, and voltage sensors 41 and 42 are connected in parallel to the shunt resistors 31 and 32. The voltage sensors 41 and 42 detect currents flowing through the storage batteries 11 and 12 from the amount of voltage drop caused by the shunt resistors 31 and 32, and the detection result is notified to the ECU 20. In the present embodiment, a positive current is detected if each storage battery 11, 12 is in a discharged state, and a negative current is detected if each storage battery 11, 12 is in a charged state. The voltage sensors 41 and 42 correspond to current detection means.

  A first diode 51 and a second diode 52 are connected to the first storage battery 11 and the second storage battery 12, respectively. Both the diodes 51 and 52 have cathodes connected to the negative electrodes of the storage batteries 11 and 12 and permit discharge from the storage batteries 11 and 12 when the power supply device 10 is in a discharged state. 12 is prohibited from being charged. Each of the diodes 51 and 52 uses a discharge current as a forward current, and a forward drop voltage Vf of about 0.6 V, for example, is generated by the forward current. The diodes 51 and 52 correspond to current backflow prevention means during discharge.

  A first switch SW1 and a second switch SW2 are connected in parallel to the first diode 51 and the second diode 52, respectively. The switches SW1 and SW2 form discharge paths that bypass the diodes 51 and 52. If the switches SW1 and SW2 are on, a path that bypasses the diodes 51 and 52 is formed as a discharge path, and if the switches SW1 and SW2 are off, a path that passes through the diodes 51 and 52 is formed as a discharge path. The In a situation where the electrical load 100 is not operating and the power supply device 10 is not discharging the electrical load 100, both switches SW1 and SW2 are both in the off state. Thereby, the backflow of the electric current from one storage battery to the other storage battery is suppressed irrespective of the open circuit voltage OCV1, OCV2 of both the storage batteries 11, 12.

  The ECU 20 controls the on / off states of the switches SW1, SW2 based on the detection results of the voltage sensors 41, 42 (values I1, I2 of the currents flowing through the storage batteries 11, 12). In this case, at the start of discharge, a storage battery having a high OCV among the storage batteries 11 and 12 is to be discharged, a switch connected in series to the storage battery to be discharged is turned on, and the storage battery not connected to discharge is connected in series. Turn off the switch. As a result of the discharge in the storage battery to be discharged, the OCV of the storage battery to be discharged decreases. As a result of the decrease in the OCV of the storage battery to be discharged, the OCV of the storage battery to be discharged approaches the OCV of the storage battery that is not the discharge target, so that the electric load 100 is discharged from the storage battery that is not the discharge target via the diode. Thereafter, a storage battery that is not a discharge target is newly added as a discharge target, so that each of the storage batteries 11 and 12 discharges the electric load 100 without a diode.

  FIG. 2 shows a flowchart of the discharge target selection process. The processing is performed at a predetermined cycle by the ECU 20 as the first control means when the electric power 100 is not discharged from the power supply device 10.

  In step S11, current detection values I1 and I2 which are detection results of the voltage sensors 41 and 42 are acquired. In a subsequent step S12, it is determined whether or not the power supply device 10 has started discharging the electric load 100 based on the currents I1 and I2. Specifically, it is determined whether or not discharging is being performed in at least one of the storage batteries 11 and 12.

  In the subsequent step S13, the currents I1 and I2 are compared. The open circuit voltage OCV of the storage battery in which a large current flows is larger than the open circuit voltage OCV of the storage battery in which a small current flows. Therefore, in order to discharge the electric load 100 from the storage battery having a large open circuit voltage OCV, the following switch control is performed.

  When the current I1 is larger than I2 (S13: YES), in step S14, the switch SW1 is turned on and the switch SW2 is turned off. Thereby, discharge from the first storage battery 11 to the electric load 100 is mainly performed. If the current I1 is less than or equal to I2 (S13: NO), in step S15, the switch SW1 is turned off and the switch SW2 is turned on. Thereby, the discharge with respect to the electrical load 100 is mainly implemented from the 2nd storage battery 12. FIG.

  FIG. 3 shows a flowchart of the discharge target addition process. The processing is periodically performed during discharge from the power supply device 10 to the electric load 100 by the ECU 20 as the second control means.

  In step S21, it is determined whether or not the switch SW1 is on and the switch SW2 is off. When the switch SW1 is in the on state and the switch SW2 is in the off state (S21: YES), in step S22, the difference between the current I1 flowing through the storage battery 11 and the current I2 flowing through the storage battery 12 (= I1-I2) Is less than or equal to a predetermined threshold value Ith1. When the difference between the current I1 and the current I2 is equal to or smaller than the predetermined threshold value Ith1 (S22: YES), the switch SW2 is changed to the on state in step S23, and the process is terminated. If the difference between the current I1 and the current I2 is greater than the predetermined threshold value Ith1 (S22: NO), the process ends without changing the state of the switches SW1 and SW2.

  If the switch SW1 is on and the switch SW2 is not off (S21: NO), whether or not the switch SW1 is off and the switch SW2 is on is determined in step S24. judge.

  If the switch SW1 is in the off state and the switch SW2 is in the on state (S24: YES), whether or not the difference between the current I2 and the current I1 (= I2−I1) is equal to or less than a predetermined threshold value Ith1 in step S25. Determine whether. When the difference between the current I2 and the current I1 is equal to or smaller than the predetermined threshold value Ith1 (S25: YES), in step S26, the switch SW1 is changed to the on state, and the process ends. If the difference between the current I2 and the current I1 is greater than the predetermined threshold value Ith1 (S25: NO), the process ends without changing the state of the switches SW1 and SW2. When both the switches SW1 and SW2 are in the off state or the on state (S24: NO), in step S27, the discharge target exclusion process described later is performed and the process is terminated.

  In the discharge target addition process, the difference between the currents I1 and I2 flowing in the storage batteries 11 and 12 is determined as a threshold value Ith1 in a situation where one of the storage batteries 11 and 12 is a discharge target and one of the switches SW1 and SW2 is turned on. Compare with When the difference between the currents I1 and I2 is equal to or smaller than the threshold value Ith1, the difference between the open-circuit voltages OCV1 and OCV2 of the two storage batteries 11 and 12 is considered to be small, and both the storage batteries 11 and 12 are discharged. The switch state is changed so that both are turned on.

  FIG. 4 shows, as a timing chart, the voltage and current of each of the storage batteries 11 and 12 and the time change of the switches SW1 and SW2 when the discharge control of this embodiment is performed.

  At time T0, the electric load 100 is not driven, and the currents I1 and I2 flowing through the storage batteries 11 and 12 are both zero. Since I1 and I2 flowing through the storage batteries 11 and 12 are 0, the inter-terminal voltages V1 and V2 of the storage batteries 11 and 12 correspond to the open-circuit voltages OCV1 and OCV2, respectively. Here, the state of charge (SOC) of the storage battery 11 is greater than the SOC of the storage battery 12, and as a result, the open circuit voltage OCV 1 of the storage battery 11 is greater than the open circuit voltage OCV 2 of the storage battery 12. Further, both switches SW1, SW2 are in an off state.

  At time T <b> 1, the electric load 100 starts driving, so that the discharge from the power supply device 10 to the electric load 100 is started. Here, since the open circuit voltage OCV1 of the storage battery 11 is larger than the open circuit voltage OCV2 of the storage battery 12, the discharge from the storage battery 11 to the electric load 100 is performed, and the discharge in the storage battery 12 is not performed. Since the discharge current flows through the storage battery 11, the voltage V <b> 1 of the storage battery 11 decreases as the voltage drops due to the internal resistance R <b> 1 of the storage battery 11.

  At time T1, which is the discharge start time, since I1> I2, the switch SW1 is turned on. Thereafter, as the storage battery 11 is discharged, the SOC of the storage battery 11 decreases, and as a result, the voltage of the storage battery 11 gradually decreases.

  At time T2, the voltage V1 and the voltage V2 become equal, but since the current flows through the storage battery 11, the voltage V1 is the closed circuit voltage CCV and the current does not flow through the storage battery 12, so the voltage V2 is the open circuit voltage OCV. It corresponds to. That is, there is a difference in voltage drop due to the internal resistance in the storage battery 11 between the open circuit voltage OCV1 of the storage battery 11 and the open circuit voltage OCV2 of the storage battery 12 (OCV1-R1 · I1 = OCV2). If the switches SW1 and SW2 are both turned on at time T2, then if the current flowing through the electrical load 100 decreases, a backflow from the storage battery 11 to the storage battery 12 may occur due to the difference between the open circuit voltages OCV1 and OCV2. Concerned.

  At time T3, the voltage V1 becomes a value obtained by subtracting the forward drop voltage Vf from the voltage V2 (V1 = V2−Vf). Accordingly, power supply from the storage battery 12 to the electric load 100 is started while preventing backflow by the diode 52. At times T3 to T4, current flows from each of the storage batteries 11 and 12 to the electric load 100, both the SOCs of the storage batteries 11 and 12 decrease, and both the voltages V1 and V2 decrease. At time T3 to T4, since I1> I2, the open circuit voltage OCV1 of the storage battery 11 decreases faster than the open circuit voltage OCV2 of the storage battery 12. Therefore, the difference between SOC1 and SOC decreases, and as a result, current I1 decreases and current I2 increases. Moreover, since the 1st storage battery 11, the 2nd storage battery 12, and the diode 52 are connected in parallel, the state set to V1 = V2-Vf is maintained.

  At time T4, the difference between the currents I1 and I2 becomes a predetermined threshold value Ith1 = 0. Here, immediately before the switch SW2 is turned on, the state of V1 = V2-Vf is maintained. The inter-terminal voltage V1 of the storage battery 11 is V1 = OCV1 + R1 · I1, and the inter-terminal voltage V2 of the storage battery 12 is V2 = OCV2 + R2 · I2. If the values of the internal resistances R1, R2 of the storage battery 11 and the storage battery 12 are equal, the difference between the open voltage OCV2 of the storage battery 12 and the open voltage OCV1 of the storage battery 11 is equal to the forward drop voltage Vf of the diode 52 (OCV2 -OCV1 = Vf).

  When both switches SW1 and SW2 are turned on, a reverse flow is generated from the storage battery 12 to the storage battery 11 under the condition that OCV2-OCV1> Ia · R2 (Ia is a load current flowing through the electric load 100). . That is, if the forward voltage drop Vf of the diode 52 is smaller than the load current Ia multiplied by the internal resistance R2, no backflow occurs. In this respect, the forward voltage drop Vf is as small as about 0.6 V, the load current Ia is, for example, 20 A, the internal resistance R2 of the storage battery 12 is, for example, 100 mΩ, and OCV2-OCV1 = Vf <Ia · R2 is established. No back flow occurs.

  At time T4, since both switches SW1 and SW2 are turned on, both storage batteries 11 and 12 are connected in parallel without the diodes 51 and 52, so that the voltages V1 and V2 between the terminals of both storage batteries 11 and 12 are It becomes equal value.

  Assume that the driving state of the electric load 100 changes and the load current Ia decreases to 10 A at time T5 when both the storage batteries 11 and 12 are discharged. Even in this case, since OCV2−OCV1 = Vf <Ia · R2, the backflow in the storage battery 11 does not occur.

  Here, when there is a difference between the internal resistance R1 of the first storage battery 11 and the internal resistance R2 of the second storage battery 12 under the situation where both the storage batteries 11 and 12 are discharged, the internal resistance is small. The current flowing from the storage battery to the electric load 100 increases. For example, when R1 <R2, I1> I2. Under such circumstances, when discharging from both storage batteries 11 and 12 to the electric load 100 is continued, the SOC of the first storage battery 11 decreases faster than the SOC of the second storage battery 12. That is, the open circuit voltage OCV1 of the first storage battery 11 decreases faster than the open circuit voltage OCV2 of the second storage battery 12. In this way, it is conceivable that a difference occurs between the open voltage OCV1 of the first storage battery 11 and the open voltage OCV2 of the second storage battery. Thus, if the driving state of the electric load 100 changes and the flowing load current Ia decreases under the situation where the open-circuit voltages OCV1 and OCV2 are different, a backflow may occur between the storage battery 11 and the storage battery 12. .

  In order to prevent such a backflow, in a situation where the switches SW1 and SW2 of both the storage batteries 11 and 12 are both turned on, one of the currents I1 and I2 flowing through the storage batteries 11 and 12 is greater than a predetermined threshold value Ith2. When it becomes small, the storage batteries 11 and 12 are excluded from discharge targets by turning off the switches SW1 and SW2 of the storage batteries 11 and 12. By performing such control, the backflow generated in the storage batteries 11 and 12 can be suppressed.

  FIG. 5 shows a flowchart of the discharge object exclusion process in the present embodiment. This process is performed by the ECU 20 as the third control means during the discharge target addition process.

  In step S31, it is determined whether or not both the switches SW1 and SW2 are turned on. If at least one of the switches SW1 and SW2 is in the off state (S31: NO), the process is terminated without changing the state of the switches SW1 and SW2. When the switches SW1 and SW2 are both turned on, that is, when both the storage batteries 11 and 12 are to be discharged (S31: YES), in step S32, the current I1 flowing through the storage battery 11 is a predetermined threshold value Ith2 ( For example, it is determined whether it is smaller than 0.1A). If I1 <Ith2 is established (S32: YES), in step S33, the switch SW1 is turned off to end the process in order to exclude the storage battery 11 from the discharge target.

  When I1 ≧ Ith2 (S32: NO), it is determined in step S34 whether or not the current I2 flowing through the storage battery 12 is smaller than the threshold value Ith2. When I2 <Ith2 is satisfied (S34: YES), in step S35, the switch SW2 is turned off to exclude the storage battery 12 from the discharge target, and the process ends. If the currents I1 and I2 are both greater than or equal to the threshold value Ith2 (S34: NO), the process ends without changing the state of the switches SW1 and SW2.

  By performing the discharge target exclusion process, it becomes possible to exclude one of the storage batteries having the reduced open circuit voltage OCV from the discharge target. Furthermore, when the open circuit voltage OCV of the other storage battery decreases, the discharge target addition process is performed again, so that the discharge from the storage batteries 11 and 12 to the electric load 100 can be performed.

  Hereinafter, effects in the present embodiment will be described.

  After starting the discharge of the power supply apparatus 10 with one of the storage batteries 11 and 12 as the discharge target and the other as the target, the difference in the terminal voltage between the storage batteries 11 and 12 as the voltage between the terminals of the storage battery to be discharged decreases. Becomes smaller, and current starts to flow even on the side of the storage battery that is not to be discharged. Based on the current difference between the storage batteries 11 and 12 in this state, the discharge of the storage battery that is not to be discharged is started (ON control of the switches SW1 and SW2). Specifically, when the difference between the current flowing through the storage battery that is the target of discharge and the current flowing through the storage battery that is not the target of discharge is equal to or less than the threshold value Ith1, the storage battery that is not the target of discharge is newly set as the target of discharge. to add.

  In this case, the difference between the voltages V1, V2 between the terminals of both the storage batteries 11, 12 is small and the current difference (I1-I2 or I2-I1) is also small. Therefore, the open circuit voltage OCV1 between the storage batteries 11, 12 is small. , OCV2 is also small. Therefore, even when the load current Ia flowing from the power supply device 10 to the electric load 100 decreases after both the switches SW1 and SW2 are turned on, the occurrence of a reverse flow in which a current flows between the storage batteries 11 and 12 is suppressed. It becomes possible to do.

  At the start of discharge, the SOC of each of the storage batteries 11 and 12 may vary, and in this state, the storage battery to be discharged and the storage battery that is not to be discharged are selected. And after the start of discharge, based on the determination result of the current difference between the storage battery to be discharged and the storage battery that is not to be discharged, the storage battery that is not to be discharged at the beginning of discharge is switched as the storage battery to be discharged. In this case, the inter-battery variation at the beginning of discharge can be eliminated after the start of discharge.

  When one of the switches SW1 and SW2 is turned on and the other is turned off, the difference between the open voltages OCV1 and OCV2 of the storage batteries 11 and 12 is a diode when the difference between the currents I1 and I2 is 0. 51 and 52 are equal to the forward voltage drop Vf. Since the forward drop voltage Vf is a small value of about 0.6 V, if both switches SW1 and SW2 are turned on on condition that the difference between the currents I1 and I2 becomes zero, the open-circuit voltages OCV1 and OCV2 A difference can be made small enough and the backflow between the storage batteries 11 and 12 can be suppressed.

  By the discharge target exclusion process, it becomes possible to exclude one of the storage batteries having the reduced open circuit voltage OCV from the discharge target. Thereby, it can suppress that a backflow arises between the storage batteries 11 and 12. FIG. Furthermore, when the open circuit voltage OCV of the other storage battery decreases, the discharge target addition process is performed again, so that the discharge from the storage batteries 11 and 12 to the electric load 100 can be performed.

  In the present embodiment, at the start of discharging, both switches SW1 and SW2 are turned off, and then, based on the detection values of the currents I1 and I2 flowing through the storage batteries 11 and 12, 12 is a discharge target. Thereby, even if it does not detect the inter-terminal voltages V1 and V2 of the storage batteries 11 and 12, the storage batteries 11 and 12 with the higher open-circuit voltages OCV1 and OCV2 can be targeted for discharge.

(Second Embodiment)
Next, differences of the second embodiment from the first embodiment will be mainly described. In the present embodiment, when both SOCs 11 and 12 are in a predetermined range at the start of discharge, both the storage batteries 11 are targeted for discharge. With such a configuration, subsequent discharge target addition processing is not performed.

  FIG. 6 shows SOC-OCV characteristics of the storage batteries 11 and 12 which are lithium ion storage batteries. In the lithium ion storage battery, in the region where the SOC is SOCa (for example, SOCa = 20%) or less and the region where the SOC is the SOCb (for example, SOCb = 80%) or more, the OCV greatly increases as the SOC increases. . Then, in the region where the SOC is SOCa to SOCb, the OCV gradually increases as the SOC increases (so-called plateau region) as compared with the region where the SOC is SOCa or lower and the region where the SOC is higher than SOCb. In other words, in the region where the SOC becomes SOCa to SOCb, the change in the OCV accompanying charging / discharging is slight. That is, in the region where the SOCs of both the storage batteries 11 and 12 are both SOCa to SOCb, the difference in the open circuit voltage OCV associated with charging / discharging is unlikely to occur. As a result, it is considered that backflow hardly occurs.

  Therefore, when the SOCs of both storage batteries 11 and 12 are both in the range of SOCa to SOCb, both storage batteries 11 and 12 are targeted for discharge. In the present embodiment, voltage sensors are provided at both terminals of both storage batteries 11 and 12, and the ECU 20 acquires detection values of both voltage sensors and calculates the SOCs of both storage batteries 11 and 12.

  FIG. 7 is a flowchart showing the discharge target selection process in the present embodiment. The processing is performed by the ECU 20 at a predetermined cycle when the electric power supply 100 is not discharged to the electric load 100. Here, the same processes as those in the flowchart shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as necessary.

  In step S11, after obtaining the detected values of the currents I1 and I2, it is determined whether or not the discharge is started in step S12. When the discharge is not started (S12: NO), the detected values of the inter-terminal voltages V1, V2 of the storage batteries 11, 12 are acquired in step S41. Here, since no discharge is performed, no current flows through both the storage batteries 11 and 12, and the inter-terminal voltages V1 and V2 correspond to the open-circuit voltages OCV1 and OCV2, respectively. In step S42, the SOCs of the storage batteries 11 and 12 are calculated based on the detected values of the inter-terminal voltages V1 and V2, and the process is terminated.

  When the discharge is started (S12: YES), in step S43, it is determined whether or not the SOC (previous value) of both the storage batteries 11 and 12 is SOCa or less or SOCb or more. When at least one of the SOCs of both the storage batteries 11 and 12 is SOCa or less or SOCb or more, the process after step S13 is performed. When the SOCs of both storage batteries 11 and 12 are both in the range of SOCa to SOCb (S43: NO), both switches SW1 and SW2 are both turned on to end the process in order to discharge both storage batteries 11 and 12 together. To do.

  The power supply apparatus 10 according to the second embodiment has the following effects in addition to the effects exhibited by the power supply apparatus 10 according to the first embodiment.

  The SOC-OCV characteristic of the lithium ion storage battery has a plateau region (SOCa to SOCb) as shown in FIG. In the plateau region, the open-circuit voltage OCV of the lithium ion storage battery is substantially constant. That is, outside the plateau region, the open voltages OCV1, OCV2 of the storage batteries 11, 12 are likely to be different. Therefore, when at least one of the storage batteries 11 and 12 is outside the plateau region, either one of the storage batteries 11 or 12 is set as a discharge target at the start of discharge. Thereby, it becomes possible to suppress the backflow in the storage batteries 11 and 12 while suppressing the power loss in the diodes 51 and 52.

(Third embodiment)
Next, differences of the third embodiment from the first embodiment will be mainly described. In the present embodiment, the charging is optimized in a state where the storage battery is charged by supplying power from the charging means to each storage battery. The electrical configuration of the power supply apparatus 10A in the third embodiment will be described with reference to FIG. FIG. 8 particularly shows a configuration related to charging of the power supply apparatus 10A. In FIG. 8, the same components as those in FIG.

  A charging device 200 (constant current source) is connected to the power supply device 10 </ b> A so as to supply charging power to the storage batteries 11 and 12. A third diode 53 and a fourth diode 54 are connected to the storage batteries 11 and 12, respectively. Both diodes 53 and 54 have their anodes connected to the negative electrodes of the respective storage batteries 11 and 12, and permit charging of the respective storage batteries 11 and 12 when the power supply device 10 </ b> A is in a charged state. Discharge from 12 is prohibited. The diodes 53 and 54 correspond to current backflow prevention means during charging.

  A third switch SW3 and a fourth switch SW4 are connected in parallel to the third diode 53 and the fourth diode 54, respectively. The switches SW3 and SW4 form a charging path that bypasses the diodes 53 and 54. If the switches SW3 and SW4 are closed, a path that bypasses the diodes 53 and 54 is formed as a charging path, and if the switches SW3 and SW4 are open, a path that passes through the diodes 53 and 54 is formed as a charging path. The

  Moreover, in this embodiment, unlike 1st Embodiment and 2nd Embodiment, if each storage battery 11 and 12 is a discharge state, a negative electric current will be detected, and if each storage battery 11 and 12 is a charge state, it will be positive. It is assumed that current is detected.

  FIG. 9 shows, as a timing chart, the voltage and current of each of the storage batteries 11 and 12 and the time change of the switches SW3 and SW4 when the charge control of this embodiment is performed.

  At time T10, no current is supplied from charging device 200, and currents I1, I2 flowing through storage batteries 11, 12 are both zero. Since I1 and I2 flowing through the storage batteries 11 and 12 are 0, the voltages V1 and V2 of the storage batteries 11 and 12 correspond to the open-circuit voltages OCV1 and OCV2, respectively. Here, the SOC of the storage battery 11 is smaller than the SOC of the storage battery 12, and as a result, the open circuit voltage OCV1 of the storage battery 11 is smaller than the open circuit voltage OCV2 of the storage battery 12. Further, both switches SW3 and SW4 are turned off.

  At time T11, charging from the charging device 200 to the power supply device 10A is started. Here, since the open circuit voltage OCV1 of the storage battery 11 is smaller than the open circuit voltage OCV2 of the storage battery 12, the charging of the storage battery 11 is performed from the charging device 200, and the charging of the storage battery 12 is not performed. Since the charging current flows through the storage battery 11, the voltage V <b> 1 of the storage battery 11 increases with a voltage drop due to the internal resistance R <b> 1 of the storage battery 11.

  At time T11, which is the charging start time, the ECU 20 controls the on / off states of the switches SW3 and SW4 based on the detection results of the voltage sensors 41 and 42 (values I1 and I2 of the currents flowing through the storage batteries 11 and 12). To do. In the illustrated example, since I1> I2, the switch SW3 is turned on. Thereafter, as the storage battery 11 is charged, the SOC of the storage battery 11 increases. As a result, the voltage of the storage battery 11 increases.

  At time T12, the voltage V1 and the voltage V2 become equal, but since the current flows through the storage battery 11, the voltage V1 is the closed circuit voltage CCV and the current does not flow through the storage battery 12, so the voltage V2 is the open circuit voltage OCV. It corresponds to. That is, there is a difference in voltage drop due to the internal resistance in the storage battery 11 between the open circuit voltage OCV1 of the storage battery 11 and the open circuit voltage OCV2 of the storage battery 12 (OCV1 + R1 · I1 = OCV2). If the switches SW3 and SW4 are both turned on at time T12, then when the current flowing from the charging device 200 decreases, a backflow from the storage battery 12 to the storage battery 11 may occur due to the difference between the open circuit voltages OCV1 and OCV2. Concerned.

  At time T13, the voltage V1 becomes a value obtained by adding the forward drop voltage Vf to the voltage V2 (V1 = V2 + Vf). Accordingly, charging of the storage battery 12 from the charging device 200 is started. From time T13 to T14, current flows from the charging device 200 to the storage batteries 11, 12, the SOC of the storage batteries 11, 12 increases, and the voltages V1, V2 both increase. Here, since I1> I2, the open circuit voltage OCV1 of the storage battery 11 increases faster than the open circuit voltage OCV2 of the storage battery 12. As a result, the current I1 decreases and the current I2 increases.

  The ECU 20 compares the difference between the currents I1 and I2 flowing through the storage batteries 11 and 12 with the threshold value Ith3 under a situation where one of the storage batteries 11 and 12 is to be charged and one of the switches SW3 and SW4 is turned on. . When the difference between the currents I1 and I2 is equal to or less than the threshold value Ith3, the difference between the open-circuit voltages OCV1 and OCV2 of the storage batteries 11 and 12 is considered to be small, and both storage batteries 11 and 12 are to be charged. The switch state is changed so that both are turned on.

  At a time T14, under the situation where only the switch SW3 is in the on state, the difference between the currents I1 and I2 becomes a predetermined threshold value Ith3 = 0, so that the switch SW4 is in the on state. Here, immediately before the switch SW4 is turned on, V1 = V2 + Vf. The inter-terminal voltage V1 of the storage battery 11 is V1 = OCV1 + R1 · I1, and the inter-terminal voltage V2 of the storage battery 12 is V2 = OCV2 + R2 · I2. If the values of the internal resistances R1 and R2 of the storage battery 11 and the storage battery 12 are equal, the difference between the open circuit voltage OCV2 of the storage battery 12 and the open circuit voltage OCV1 of the storage battery 11 becomes equal to the forward drop voltage Vf of the diode 52 (OCV1). -OCV2 = Vf).

  Here, when both the switches SW3 and SW4 are turned on, a reverse flow occurs from the storage battery 11 to the storage battery 12 under the condition of OCV1-OCV2> Ib · R1. Here, Ib is a supply current supplied from the charging device 200, and is equal to the sum (I1 + I2) of the currents flowing through the storage batteries 11, 12. That is, if the forward drop voltage Vf of the diode 52 is smaller than the supply current Ib multiplied by the internal resistance R1, no backflow occurs. In this respect, the forward drop voltage Vf is as small as about 0.6 V, the supply current Ib is 20 A, for example, and the internal resistance R1 of the storage battery 11 is 100 mΩ, for example, so that OCV1-OCV2 = Vf <Ib · R1 is established. , No back flow occurs.

  At time T15 when charging is performed on each of the storage batteries 11 and 12, an electric load other than the power supply device 10A is connected to the charging device 200. As a result, the charging device 200 supplies the power supply device 10A. Assume that the supplied current Ib is reduced to 10A. Even in this case, OCV1−OCV2 = Vf <Ib · R1 is established, and no backflow occurs in the storage battery 11.

  Also in this embodiment, when both the storage batteries 11 and 12 are to be charged, the same charging object exclusion process as the discharging object exclusion process in the first embodiment is performed. It is determined whether or not the current I1 flowing through the storage battery 11 to be charged is smaller than a predetermined threshold value Ith4. If I1 <Ith4 is established, the switch SW3 is turned off to charge the storage battery 11 Exclude from Further, it is determined whether or not the current I2 flowing through the storage battery 12 to be charged is smaller than the threshold value Ith4. If I2 <Ith4 is established, the switch SW4 is turned off to charge the storage battery 12 Exclude from

  According to the present embodiment, when charging the power supply device 10, the same effect as that during discharging in the first embodiment can be obtained during charging.

(Other embodiments)
In the first and second embodiments, a value obtained by dividing the forward drop voltage Vf of the diodes 51 and 52 by the value R1 or R2 of the internal resistance of the storage batteries 11 and 12 may be used as the threshold value Ith1. For example, when the storage battery 11 is a discharge target, the difference between the currents I1 and I2 is Vf / R1.

  At this time, assuming that R1≈R2, I1≈I2, immediately before the switches SW1 and SW2 are turned on, the inter-terminal voltage V1 of the storage battery 11 is V1 = OCV1 + I1 · R1 = OCV1 + (I1-I2) R1 + I2 · R2 = OCV1 + Vf + I2 · R2. The inter-terminal voltage V2 of the storage battery 12 is V2 = OCV2 + I2 · R2. Further, since V1−Vf = V2, the open-circuit voltages OCV1 and OCV2 of both the storage batteries 11 and 12 are equal (OCV1 = OCV2).

  Therefore, both switches SW1 and SW2 are turned on in a situation where the open-circuit voltages OCV1 and OCV2 of both the storage batteries 11 and 12 are equal, and the backflow generated in both the storage batteries 11 and 12 can be suitably suppressed. Further, since Vf / R1> 0, the period of time T3 to T4 in FIG. 4 can be shortened, and power loss due to current flowing through the diodes 51 and 52 can be suppressed.

  Similarly, in the third embodiment, a value obtained by dividing the forward drop voltage Vf of the diodes 51 and 52 by the value R1 or R2 of the internal resistance of the storage batteries 11 and 12 may be used as the threshold value Ith3. Also in this case, as in the case of discharging, both switches SW1 and SW2 are turned on in a situation where the open-circuit voltages OCV1 and OCV2 of both storage batteries 11 and 12 are equal, and the reverse flow generated in both storage batteries 11 and 12 is preferable. Can be suppressed. Further, since Vf / R1> 0, the period of time T13 to T14 in FIG. 9 can be shortened, and power loss due to current flowing through the diodes 53 and 54 can be suppressed.

  -A power supply device is good also as a structure which has the function of discharge control and the function of charge control together. The electrical configuration of the power supply apparatus 10B having a charge / discharge control function will be described with reference to FIG. In FIG. 10, the same components as those in FIGS. 1 and 8 are denoted by the same reference numerals.

  In the power supply device 10B, diodes 51 and 53 whose forward directions are opposite to each other are connected in series to the first storage battery 11, and diodes 52 and 54 whose forward directions are opposite to each other are connected to the second storage battery 12 in series. It is connected. Further, switches SW1, SW2, SW3, and SW4 are connected in parallel to the diodes 51 to 54, respectively.

  The ECU 20 controls the open / close states of the switches SW1 to SW4 based on the detection results of the voltage sensors 41 and 42 (values of the currents I1 and I2 flowing through the storage batteries 11 and 12). In this case, charge / discharge control is performed while using both or either one of the storage batteries 11 and 12 as a storage battery to be discharged or charged.

  The ECU 20 performs the discharge control described in the first embodiment or the second embodiment and the charge control described in the third embodiment. At the time of discharging, both the switches SW3 and SW4 are turned on. At the time of charging, both the switches SW1 and SW2 are turned on.

  -In the above-mentioned embodiment, although the power supply device was set as the structure provided with 2 storage batteries, it is good also as a structure provided with 3 or more storage batteries. In this case, a backflow prevention diode, a switch as a detour path, and current detection means are provided for the storage battery. Then, when the difference between the current flowing through the storage battery that is the target of charge / discharge and the current flowing through the storage battery that is not the target of charge / discharge is equal to or less than a predetermined threshold value, the charge / discharge is excluded. By making the storage battery a new charge / discharge target, it is possible to suppress an increase in the difference between the open-ended voltages of the storage batteries, and it is possible to suppress backflow between the storage batteries.

  Even when storage batteries having different charge capacities are connected in parallel, the difference in the open circuit voltage of each storage battery can be suppressed to the forward drop voltage Vf of the diode. For this reason, it becomes possible to use those storage batteries suitably.

  As the current detection means, a Hall element or the like may be used instead of the voltage sensor. Moreover, you may use other storage batteries, such as a nickel hydride storage battery, instead of a lithium ion storage battery as a storage battery.

  DESCRIPTION OF SYMBOLS 10 ... Power supply device, 11 ... 1st storage battery (secondary battery), 12 ... 2nd storage battery (secondary battery), 20 ... ECU (1st control means, electric current difference determination means, 2nd control means), 41,42 ... Voltage sensor (current detection means), 51, 52 ... Diode, SW1, SW2 ... Switch (opening / closing means).

Claims (5)

A power supply device (10) comprising a plurality of secondary batteries (11, 12) connected in parallel to each other,
Current detecting means (41, 42) for respectively detecting currents flowing through the plurality of secondary batteries during charging or discharging;
Diodes (51 to 54) connected in series to the plurality of secondary batteries, respectively, to prevent current backflow during charging or current backflow during discharging,
Opening / closing means (SW1 to SW4) connected in series to the plurality of secondary batteries and connected in parallel to the diodes,
Wherein the plurality of either one of the secondary batteries was selected for charging or discharging, said switching means being connected in series with the secondary battery was subject to its closed state, not before Symbol Target secondary by the switching means are connected in series with the open state to the battery, first control means for performing charging or discharging of the secondary battery was pre-Symbol Target (20),
The detection value of the current flowing through the secondary battery before and Symbol Target, before Symbol difference between the detected value of the current flowing through the secondary battery not Target determines the current difference determining means for determining whether the first threshold value or less ( 20)
Wherein the difference between the detected value of the current by the current difference detection means is determined to be equal to or less than the first threshold value, and add the secondary battery not before Symbol Target as the target, in series with the added secondary battery A second control means (20) for closing the connected opening and closing means;
Equipped with a,
The current difference determining means, power supply characterized that you set the value obtained by dividing the internal resistance as the first threshold value of the secondary battery a predetermined forward voltage drop of the diode. The first control means, at the commencement of the charging or discharging, based on the state of each of the power storage in the plurality of secondary batteries, to select a secondary battery not the secondary battery of the target object,
The current difference determining means, according to claim 1, which comprises carrying out the determination of the current difference between the secondary battery after the start of charging or discharging, non-rechargeable battery before Symbol Target before Symbol Target Power supply. When a plurality of said secondary battery and the target, respectively determines the current reduction determining means whether or not the detected value of the current flowing through the secondary battery and subject to its is decreased from the second threshold value (20 )When,
If it is determined that the detected value of the current is decreased from the second threshold value by the current decrease determining means excludes the secondary battery from the subject, the opening and closing is connected in series with the secondary battery Third control means (20) for opening the means;
The power supply device according to claim 1 or 2, characterized in that it comprises a. Each of the secondary batteries has a plateau region in which the change in the open circuit voltage with respect to the change in the remaining capacity is small as the remaining capacity-open circuit voltage characteristics,
When the remaining capacity of the secondary battery does not belong to the plateau region with respect to at least one secondary battery among the plurality of secondary batteries, the first control unit stores each power storage in the plurality of secondary batteries. based on the state, the power supply device according to any one of claims 1 to 3, wherein the selecting the secondary battery and the secondary battery of the subject not the object. A power supply device (10) comprising a plurality of secondary batteries (11, 12) connected in parallel to each other,
Current detecting means (41, 42) for respectively detecting currents flowing through the plurality of secondary batteries during charging or discharging;
Diodes (51 to 54) connected in series to the plurality of secondary batteries, respectively, to prevent current backflow during charging or current backflow during discharging,
Opening / closing means (SW1 to SW4) connected in series to the plurality of secondary batteries and connected in parallel to the diodes,
One of the plurality of secondary batteries is selected as a target for charging or discharging, and the open / close means connected in series to the target secondary battery is closed, and connected in series to a secondary battery that is not the target. A first control means (20) for carrying out charging or discharging on the target secondary battery by opening the open / close means being open;
Current difference determination means (20) for determining whether or not a difference between a detected value of a current flowing in the target secondary battery and a detected value of a current flowing in the non-target secondary battery is equal to or less than a first threshold;
When the current difference determination means determines that the difference between the detected current values is less than or equal to the first threshold value, a secondary battery that is not the target is added as the target, and is connected in series to the added secondary battery. Second control means (20) for closing said opening and closing means;
With
Each of the secondary batteries has a plateau region in which the change in the open circuit voltage with respect to the change in the remaining capacity is small as the remaining capacity-open circuit voltage characteristics,
When the remaining capacity of the secondary battery does not belong to the plateau region with respect to at least one secondary battery among the plurality of secondary batteries, the first control unit stores each power storage in the plurality of secondary batteries. Based on the state of the above, the target secondary battery and the non-target secondary battery are selected.

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