JP2017203748A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate the state of charge (SOC) of a secondary battery in a power supply system that includes a secondary battery having a first area where an open circuit voltage (OCV) changes very little even when the SOC changes and a second area where the OCV changes in correspondence to a change of the SOC.SOLUTION: Provided is a power supply system 9 comprising a battery 1, a voltage sensor 5, a current sensor 7, and a controller 8 for integrating the charge/discharge currents of the battery 1 that are detected by the current sensor 7 and estimating the SOC of the battery 1, the controller 8 detecting the OCV of the battery 1 by the voltage sensor 5, with the charge/discharge currents of the battery 1 reduced to zero, and, when the detected OCV is in an area where an OCV change rate relative to the SOC of the battery 1 is larger than a prescribed threshold, replacing the SOC of the battery 1 estimated by integrating the charge/discharge currents with the SOC estimated on the basis of the OCV.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system, and more particularly to a configuration of a power supply system that estimates a charging rate of a battery.

  In recent years, electric vehicles such as hybrid vehicles that use an engine and a motor as driving sources and electric vehicles that are driven by a motor are often used. Such an electric vehicle is equipped with a main battery that supplies driving power to the driving motor and an auxiliary battery that supplies driving power to various auxiliary machines. The main battery and the auxiliary battery are chargeable / dischargeable secondary batteries, and the charge / discharge current depends on the charge rate (ratio of charge capacity (A × h) to full charge capacity (A × h), hereinafter referred to as SOC). Is controlled. For this reason, in a power supply system using a secondary battery, it is required to accurately grasp the SOC of the secondary battery.

  As a method of estimating the SOC of the secondary battery, a method of integrating and calculating a charge / discharge current to the secondary battery, or detecting an open circuit voltage (hereinafter referred to as OCV) of the secondary battery, from a characteristic curve of the OCV with respect to the SOC. A method for estimating the SOC is used (see, for example, Patent Document 1).

  When the secondary battery repeats the discharge current, the temperature rises, which may raise the temperature of the current sensor that detects the charge / discharge current of the secondary battery. It is known that the current sensor generates a temperature drift in which the output changes as the temperature rises. When the temperature drift occurs, the measurement error of the charge / discharge current becomes large, so that there is a problem that the estimation accuracy of the SOC is lowered. For this reason, once the temperature of the current sensor rises above the specified temperature, the charging / discharging of the secondary battery is stopped once to make the charging / discharging current zero, and the current sensor output at that time is corrected to the output when the current is zero. And the method of restarting charging / discharging after that is proposed (for example, refer patent document 2).

JP 2007-178215 A Japanese Patent Laid-Open No. 2015-200590

  By the way, as the secondary battery, for example, a nickel metal hydride battery, a lithium ion battery, or the like is often used. These secondary batteries have a characteristic that the OCV increases as the SOC increases. For this reason, if the OCV of the battery can be detected, the SOC can be estimated from the SOC-OCV characteristic curve. However, in recent years, secondary batteries having a first region in which the OCV hardly changes even when the SOC changes and a second region in which the OCV changes in response to the change in SOC may be used. In such a secondary battery, when the OCV is in the first region, there is a problem that the SOC cannot be estimated by the OCV or even if it can be estimated, the estimation accuracy is lowered.

  When estimating the SOC in the first region of the secondary battery as described above, the charge / discharge current to the secondary battery while correcting the zero point of the current sensor as in the prior art described in Patent Document 2. It is conceivable to use a method of calculating and summing up. However, in this case, even if the temperature drift of the current sensor can be corrected, the error of the other current sensor is integrated during the integration calculation. There is a problem that the estimation error becomes large.

  Accordingly, the present invention provides a power supply system including a secondary battery having a first region in which the OCV hardly changes even if the SOC changes and a second region in which the OCV changes with respect to the change in the SOC. The purpose is to accurately estimate the SOC.

  The secondary battery, a voltage sensor for detecting the voltage of the secondary battery, a current sensor for detecting the charge / discharge current of the secondary battery, and the charge / discharge current of the secondary battery detected by the current sensor are integrated. A controller for estimating a charging rate of the secondary battery, wherein the controller detects an open circuit voltage of the secondary battery by the voltage sensor with a charge / discharge current of the secondary battery as zero. When the detected open-circuit voltage is in a region where the change rate of the open-circuit voltage with respect to the charge rate of the secondary battery is larger than a predetermined threshold, the secondary battery estimated by integrating charge / discharge currents The charging rate is replaced with the charging rate estimated based on the open circuit voltage.

  The present invention relates to a power supply system including a secondary battery having a first region in which the OCV hardly changes even if the SOC changes and a second region in which the OCV changes with respect to the change in the SOC. It can be estimated accurately.

It is a systematic diagram which shows the structure of the power supply system in embodiment of this invention. 2 is a characteristic curve showing a change in OCV with respect to SOC of a battery used in the power supply system shown in FIG. 3 is a graph showing polarization elimination time with respect to battery temperature used in the power supply system shown in FIG. It is a flowchart which shows the SOC estimated value replacement | exchange operation | movement of the power supply system shown in FIG. 1, and the zero point correction | amendment operation | movement of a current sensor. It is a systematic diagram which shows the structure of the power supply system in other embodiment of this invention. 6 is a graph showing a change in voltage Vb with respect to the SOC of the auxiliary battery of the power supply system shown in FIG. 5 and a change in output voltage Vdc of the DC / DC converter. It is a flowchart which shows the discharge operation of the power supply system shown in FIG. It is explanatory drawing which shows the flow of the electric current to the auxiliary machine load at the time of vehicle starting of the power supply system shown in FIG. It is explanatory drawing which shows the flow of the electric current to the auxiliary machine load at the time of normal driving | running | working of the power supply system shown in FIG. 6 is a graph showing changes in the output voltage Vdc of the DC / DC converter and the voltage Vb of the auxiliary battery when a rush current to the auxiliary load is generated during normal traveling in the power supply system shown in FIG. In the power supply system shown in FIG. 5, time changes of the auxiliary battery current Ib, the DC / DC converter output current Idc, and the auxiliary load demand current Ireq when a rush current to the auxiliary load occurs during normal traveling. It is a graph which shows. In the power supply system shown in FIG. 5, it is explanatory drawing which shows the flow of an electric current when the rush current to auxiliary machinery load generate | occur | produces during normal driving | running | working. 6 is a flowchart showing a charging operation of the power supply system shown in FIG. 5. In the power supply system shown in FIG. 5, it is explanatory drawing which shows the flow of the electric current at the time of charging an auxiliary machine battery during normal driving | running | working. It is a flowchart which shows the SOC estimated value replacement | exchange operation | movement of the power supply system shown in FIG. 5, and the zero point correction | amendment operation | movement of a current sensor. It is a systematic diagram which shows the structure of the other power supply system of this invention. 16 is a flowchart showing an SOC estimated value replacement operation of the power supply system shown in FIG. 15 and a zero point correction operation of the current sensor.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the power supply system 9 of the present embodiment includes a battery 1 that is a secondary battery, a load 4 that is connected to the battery 1 by a connection line 2, a relay 3 that is disposed on the connection line 2, And a controller 8. The load 4 includes a device driven by electric power from the battery 1 and a power generation element that generates electric power for charging the battery 1. A voltage sensor 5 that detects the voltage Vb of the battery 1 is connected to the battery 1, and a current sensor 7 that detects the current Ib of the battery 1 is connected to the connection line 2. Further, a temperature sensor 6 for detecting the temperature Tb of the battery 1 is attached to the battery 1.

  The controller 8 is a sensor / equipment interface to which a CPU 81 that performs arithmetic processing, a memory 82 that stores control data such as programs and characteristic curves, a voltage sensor 5, a temperature sensor 6, a current sensor 7, and a relay 3 are connected. 83, a CPU 81, a memory 82, and a sensor / equipment interface 83 are connected by a data bus 84. Signals detected by the voltage sensor 5, the temperature sensor 6, and the current sensor 7 are input from the sensor / equipment interface 83 to the controller 8, and the relay 3 is opened and closed according to a command from the controller 8.

  FIG. 2 is a characteristic curve of OCV with respect to the SOC of battery 1 shown in FIG. This characteristic curve is stored as a map in the memory 82 of the controller 8. In the battery 1, when the SOC increases from 0% (fully discharged state) to SOC 100% (fully charged state), the OCV increases from OCV0 to OCV100.

  As shown in FIG. 2, the OCV changes from OCV0 to OCV1 while the SOC is between 0% and SOC1 (for example, between 0% and 10%). Here, the voltage difference between OCV0 and OCV1 is about 30 to 40% of OCV100, which is the OCV when fully charged. Therefore, when the OCV is between OCV0 and OCV1 (SOC is between 0% and SOC1), the OCV changes as the SOC changes.

  Next, when the SOC is between SOC1 and SOC2 (for example, between 10% and 90%), the OCV changes from OCV1 to OCV2. Here, the difference between OCV1 and OCV2 is about 2-3% of OCV100 which is OCV at the time of full charge. Therefore, when the OCV is between OCV1 and OCV2 (SOC is between SOC1 and SOC2), the OCV hardly changes even if the SOC changes.

  When the SOC is between SOC2 and 100% (for example, between 90% and 100%), the OCV changes from OCV2 to OCV100. Here, the voltage difference between OCV2 and OCV100 is about 10 to 20% of OCV100 which is the OCV at the time of full charge. Therefore, when the OCV is from OCV2 to OCV100 (between the SOC is from SOC2 and 100%), the OCV changes as the SOC changes.

  As described above, the battery 1 has an OCV between OCV0 and OCV1 (SOC is between 0% and SOC1) and between OCV is OCV2 and OCV100 (SOC is between SOC2 and 100%). When the SOC changes, the OCV also changes, and the intermediate OCV is between OCV1 and OCV2 (SOC is between SOC1 and SOC2). The OCV hardly changes even if the SOC changes. It is one area. Thus, the battery 1 has a central first region and second regions at both ends.

  Here, the division between the first area and the second area is made based on whether or not the SOC can be accurately estimated based on the OCV, and is specifically determined by the change rate of the OCV with respect to the SOC. For example, when the SOC changes by 10%, the change in the OCV is less than 1%, that is, when the change ratio of the OCV to the SOC is less than 1/10, the area is defined as the first area, and the SOC changes by 10%. If the change in OCV in this case is 1% or more, that is, if the change ratio of the OCV to the SOC is 1/10 or more, the area may be defined as the second area. The threshold value of the change rate of the OCV with respect to the SOC that determines the division of the first region and the second region is not limited to 1/10, and is, for example, 1/20 to 1/50 according to the SOC-OCV characteristic curve of the battery 1. Alternatively, it may be 2/10 to 5/10.

  During charging / discharging, a polarization voltage due to polarization is generated in the battery 1. For this reason, immediately after the charging / discharging current of the battery 1 becomes zero, the voltage detected by the voltage sensor 5 is not the OCV but a voltage including the polarization voltage in the OCV. Polarization is eliminated over time. The polarization elimination time is longer as the temperature Tb of the battery 1 is lower and becomes shorter as the temperature Tb of the battery 1 is higher. The power supply system 9 of the present embodiment stores a map defining the polarization elimination time with respect to the temperature Tb of the battery 1 as shown in FIG. 3 in the memory 82 of the controller 8.

  The controller 8 detects the charge / discharge current of the battery 1 with the current sensor 7 immediately after the use of the battery 1 is started, and accumulates the current Ib to estimate the SOC of the battery 1. Immediately after the use of the battery 1 is started means, for example, when the ignition switch is turned on for the first time after the electric vehicle equipped with the battery 1 is completed.

  Next, the SOC estimated value replacement operation and the zero point correction operation of the current sensor 7 in the power supply system 9 configured as described above will be described with reference to FIG.

  As shown in step S11 of FIG. 4, the controller 8 outputs a command to turn off the relay 3 shown in FIG. By this command, the relay 3 is turned off, and the connection between the battery 1 and the load 4 is cut off. Thereby, the charging / discharging current of the battery 1 becomes zero.

  Next, the controller 8 detects the temperature Tb of the battery 1 with the temperature sensor 6, as shown in step S12 of FIG. The controller 8 acquires the polarization elimination time of the battery 1 from the memory 82 from the map of the polarization elimination time with respect to the temperature Tb of the battery 1 described above with reference to FIG. 3, and obtains it as shown in step S13 of FIG. Wait for the depolarization time. Then, the controller 8 proceeds to step S14 in FIG. 4 when the polarization elimination time has elapsed, and the voltage sensor 5 detects the voltage Vb of the battery 1. In this case, since the polarization elimination time has elapsed since the charge / discharge current became zero, the voltage Vb detected by the voltage sensor 5 is the OCV of the battery 1.

  When the voltage Vb, which is the OCV of the battery 1, is detected, the controller 8 proceeds to step S15 and determines whether the voltage Vb, which is the OCV, is in the second region where the rate of change of the OCV with respect to the SOC is greater than a predetermined threshold. To do. In the case of the battery 1, as described above, in the region where the change rate of the OCV with respect to the change rate of the SOC is 1/10 or more, the OCV changes when the SOC changes, and the SOC can be accurately estimated based on the OCV. This is the second region. As shown in FIG. 2, there are two regions where the OCV is between OCV0 and OCV1 (SOC is between 0% and SOC1) and the OCV is between OCV2 and OCV100 (SOC is between SOC2 and 100%). This is the second area. Further, when the OCV is between OCV1 and OCV2 (SOC is between SOC1 and SOC2), the change ratio of the OCV to the SOC is less than 1/10, and this is the first region in which it is difficult to estimate the SOC based on the OCV. Therefore, when the voltage Vb that is the OCV of the battery 1 is less than OCV1, or the voltage Vb that is the OCV of the battery 1 exceeds OCV2, the OCV of the battery 1 is in the second region, and the voltage Vb that is the OCV is OCV1. When ≦ Vb ≦ OCV2, the OCV of the battery 1 is in the first region.

  Therefore, the controller 8 can accurately estimate the SOC based on the OCV because the OCV of the battery 1 is in the second region if the voltage Vb, which is the OCV of the battery 1, exceeds OCV2, or is less than OCV1. Determination is made, and the process proceeds to step S16 in FIG.

  As shown in step S16 of FIG. 4, the controller 8 uses the voltage Vb, which is the OCV of the battery 1 detected in step S14, and the SOC-OCV characteristic map shown in FIG. Is estimated. For example, when the voltage Vb of the battery 1 is OCV3 shown in FIG. 2, the SOC of the battery 1 is estimated as SOC3 from the map. Then, the estimated value of SOC that has been estimated based on the current integration is replaced with a more accurate estimated value of SOC by OCV. As a result, the SOC estimation error estimated by the current integration can be eliminated. After that, the SOC is estimated by current integration based on the estimated value of the replaced SOC. When the replacement of the estimated SOC value is completed, the controller 8 proceeds to step S17 in FIG.

  On the other hand, if the controller 8 determines NO in step S15 of FIG. 4, it is determined that the OCV of the battery 1 is in the first region and it is difficult to estimate the SOC from the OCV, and the process proceeds to step S18. The SOC value estimated by the current integration up to that time is maintained, and the process proceeds to step S17.

  The controller 8 corrects the zero point of the current sensor 7 in step S17. At this time, since the relay 3 is off and the charge / discharge current of the battery 1 is zero, the output of the current sensor 7 in this state is corrected to the output when the current Ib of the battery 1 is zero. Thereby, an error due to a temperature rise or the like of the current sensor 7 can be corrected, and the estimation accuracy of the SOC based on the current integration can be improved.

  After performing the zero point correction of the current sensor 7 in step S17, the controller 8 turns on the relay 3 and returns to normal operation.

  As described above, when the OCV of the battery 1 is in the second region, the power supply system 9 of the present embodiment replaces the estimated value of the SOC with the estimated value of the SOC based on the OCV with higher accuracy. Since the estimation error of the SOC estimated by the current integration is once eliminated and the zero point correction of the current sensor 7 is performed and then the SOC is estimated by the next current integration, the OCV hardly changes even if the SOC changes. The SOC of the battery 1 having the first region and the second region in which the OCV changes with respect to the change in SOC can be accurately estimated.

[Second Embodiment]
Next, a second embodiment in which the present invention is applied to a vehicle power supply system 100 will be described with reference to FIGS. First, the configuration and basic operation of a power supply system 100 for a vehicle to which the present invention is applied will be described with reference to FIGS.

  As shown in FIG. 5, the power supply system 100 of this embodiment includes a main battery 10 that is a vehicle driving battery, a DC / DC converter 21 that is a voltage converter that steps down the voltage of the main battery 10, and an auxiliary battery. 23, a charging circuit 30 for stepping down the output voltage Vdc of the DC / DC converter 21 to charge the auxiliary battery 23 when the remaining capacity (SOC) of the auxiliary battery 23 is equal to or lower than a predetermined threshold, and DC A discharge circuit 40 for supplying power from the auxiliary battery 23 to the auxiliary load 22 when the output voltage Vdc of the DC / DC converter 21 becomes lower than the voltage Vb of the auxiliary battery 23, and a controller 70. . In FIG. 5, the alternate long and short dash line indicates a signal line.

  As shown in FIG. 5, the main battery 10 is connected to an inverter 12 by a high voltage line 61, and a motor generator 13 for driving the vehicle is connected to the inverter 12. The system main relay 11 is disposed in the high-voltage line 61. The high voltage line 61 on the inverter 12 side of the system main relay 11 and the DC / DC converter 21 are connected by a connection line 63. The DC / DC converter 21 and the auxiliary load 22 are connected by a low voltage line 64. Here, the auxiliary machine load 22 includes, for example, a power steering device, a hydraulic device, a window opening / closing device, a small motor for driving a cooling device for the main battery 10, a lighting device, and the like. The intermediate point 54 of the low voltage line 64 and the output terminal 56 of the discharge circuit 40 are connected by a first auxiliary battery line 65, and the input terminal 55 of the discharge circuit 40 and the auxiliary battery 23 are connected by a second auxiliary battery line 67. It is connected. The intermediate point 52 of the first auxiliary battery line 65 and the input terminal 57 of the charging circuit 30 are connected by a charging circuit input line 66a, and the intermediate point of the output terminal 58 of the charging circuit 30 and the second auxiliary battery line 67. 51 is connected by a charging circuit output line 66b. A current sensor 26, a fuse 27, and an auxiliary relay 28 are connected to the second auxiliary battery line 67 in this order from the auxiliary battery 23 side. A Zener diode 29 is connected between the auxiliary relay 28 and the intermediate point 51. The Zener diode 29 prevents the auxiliary battery 23 from being overvoltaged when the auxiliary battery 23 is charged.

  Thus, the charging circuit 30 includes the DC / DC converter 21 and the auxiliary machine by the low voltage line 64, the first and second auxiliary battery lines 65 and 67, the charging circuit input line 66a, and the charging circuit output line 66b. It is connected between the battery 23. An input end 57 of the charging circuit 30 is an end connected to the DC / DC converter 21 of the charging circuit 30, and is also connected to the auxiliary load 22 via the low-voltage line 64. The discharge circuit 40 is connected between the auxiliary load 22 and the auxiliary battery 23 by the low voltage line 64 and the first and second auxiliary battery lines 65 and 67, and the output terminal 56 of the discharge circuit 40. Is the end of the discharge circuit 40 connected to the auxiliary load 22, and is also connected to the DC / DC converter 21 via the low voltage line 64.

  The charging circuit 30 includes a second switching element 92 and a reactor 32 connected in series between the input end 57 and the output end 58, and a connection point 53 between the second switching element 92 and the reactor 32 and the ground. The on-off operation of the second switching element 92 and the third switching element 93 connected to the gates of the capacitor 34, the third switching element 93, the second switching element 92, and the third switching element 93 connected therebetween is controlled. And a charging control IC 35. The second switching element 92 and the third switching element 93 have parasitic diodes 92a and 93a, respectively. The charging circuit 30 has a function of alternately turning on and off the second switching element 92 and the third switching element 93 to step down the voltage input to the input terminal 57 and output the voltage from the output terminal 58. . Regardless of the configuration described above, the charging circuit 30 may be configured with, for example, a step-down chopper circuit or a step-down switching regulator as long as it is a circuit that can step down and output an input voltage.

  The discharge circuit 40 includes a first switching element 91 connected between the input terminal 55 and the output terminal 56, and a discharge control IC 42 connected to the gate of the first switching element 91 to turn on / off the first switching element 91. Including. The first switching element 91 has a parasitic diode 91a. The discharge control IC 42 is connected to the intermediate point 52 of the first auxiliary battery line 65 and the intermediate point 51 of the second auxiliary battery line 67, and detects the voltage at each intermediate point 51, 52. Since the voltage at the intermediate point 52 is equal to the output voltage Vdc of the DC / DC converter 21 and the auxiliary relay 28 is on, the voltage at the intermediate point 51 is equal to the voltage Vb of the auxiliary battery 23. When the auxiliary relay 28 is on, the voltage Vb of the auxiliary battery 23 and the output voltage Vdc of the DC / DC converter 21 are detected.

  A voltage sensor 24 that detects the voltage Vb and a temperature sensor 25 that detects the temperature Tb are attached to the auxiliary battery 23.

  As shown in FIG. 5, the DC / DC converter 21, the charge control IC 35, the discharge control IC 42, the auxiliary relay 28, the voltage sensor 24, the temperature sensor 25, and the current sensor 26 are connected to the controller 70. The DC / DC converter 21, the charge control IC 35, the discharge control IC 42, and the auxiliary relay 28 operate according to commands from the controller 70. However, the discharge control IC 42 can turn on / off the first switching element 91 independently of the controller 70. Each signal detected by the voltage sensor 24, the temperature sensor 25, and the current sensor 26 is input to the controller 70. Further, signals of voltages at the intermediate points 51 and 52 detected by the discharge control IC 42 are also input from the discharge control IC to the controller 70. The controller 70 is a computer that includes a CPU 71 that performs arithmetic processing therein and a memory 72 that stores control programs and control data. The controller 70 is connected to the auxiliary battery 23 through a connection line 68 and is connected to the DC / DC converter 21 through a connection line 69 and a low voltage line 64, and operating power is supplied from the auxiliary battery 23 or the DC / DC converter 21. The In addition, the memory 72 of the controller 70 includes the SOC-OCV characteristic map of the auxiliary battery 23 described with reference to FIGS. 2 and 3, and the polarization elimination time map with respect to the temperature Tb of the auxiliary battery 23. Stored.

  Similar to the battery 1 described above, the auxiliary battery 23 of the present embodiment is configured by a secondary battery having SOC-OCV characteristics including the first region and the second region as shown in FIG. Further, as shown in FIG. 6, in the auxiliary battery 23 of the present embodiment, the voltage Vb with 0% SOC is V0, and the voltage Vb with 100% SOC (full charge) is V100 higher than V0. As the SOC increases, the voltage Vb changes from V0 to V100. The voltage change range from V0 to V100 of the auxiliary battery 23 is a voltage range in which the auxiliary load 22 can be driven intermittently. 6 represents the output voltage Vdc when the target output voltage of the DC / DC converter 21 is Vd0. As shown in FIG. 6, the target output voltage Vd0 of the DC / DC converter 21 is higher than V100, which is the full charge voltage of the auxiliary battery 23 (Vdc> V100). Therefore, the voltage Vb of the auxiliary battery 23 is lower than the target output voltage Vd0 of the DC / DC converter 21 (Vb <Vd0). The target output voltage Vd0 of the DC / DC converter 21 is a voltage that can drive the auxiliary load 22 continuously.

  The basic operation of the power supply system 100 configured as described above will be described. First, the discharge operation of the auxiliary battery 23 will be described with reference to FIGS. 7 to 10B.

<Discharge control>
The discharge control IC 42 of the discharge circuit 40 has a voltage at the intermediate point 51 equal to the voltage Vb of the auxiliary battery 23 and a voltage at the intermediate point 52 equal to the output voltage Vdc of the DC / DC converter 21 when the auxiliary relay 28 is on. Is detected. Then, as shown in step S101 of FIG. 7, the discharge control IC 42 determines that the voltage Vb of the auxiliary battery 23 is higher than the output voltage Vdc of the DC / DC converter 21 (when Vb> Vdc), FIG. In step S102, the first switching element 91 is turned on to discharge the auxiliary battery 23, and power is supplied from the auxiliary battery 23 to the auxiliary load 22. Further, when the discharge control IC 42 determines NO in step S101 of FIG. 7, that is, when the voltage Vb of the auxiliary battery 23 is equal to or lower than the output voltage Vdc of the DC / DC converter 21 (Vb ≦ Vdc), the first switching is performed. The element 91 is turned off and the discharge of the auxiliary battery 23 is stopped.

<Operation of discharge circuit at vehicle start-up>
As shown in FIG. 8, when the vehicle start switch is turned on and the vehicle is started, the auxiliary relay 28 is turned on by a command from the controller 70. Then, the voltage at the intermediate point 51 becomes equal to the voltage Vb of the auxiliary battery 23. Thereby, the discharge control IC 42 detects the voltage Vb of the auxiliary battery 23 and the output voltage Vdc of the DC / DC converter 21.

  At this time, since the system main relay 11 is still off and the DC / DC converter 21 is also stopped, the output voltage Vdc of the DC / DC converter 21 is zero. For this reason, the discharge control IC 42 determines that the voltage Vb of the auxiliary battery 23 is higher than the output voltage Vdc of the DC / DC converter 21 (Vb> Vdc) in step S101 of FIG. 7, and proceeds to step S102 of FIG. The first switching element 91 is turned on to discharge the auxiliary battery 23, and power is supplied from the auxiliary battery 23 to the auxiliary load 22.

  Then, current flows from the auxiliary battery 23 toward the auxiliary load 22 as indicated by an arrow R1 in FIG. In addition, since the current flows from the auxiliary battery 23 toward the auxiliary load 22 through the parasitic diode 91a of the discharge circuit 40 until the first switching element 91 is turned on from the OFF state, When voltage Vb is higher than output voltage Vdc of DC / DC converter 21, power can be supplied from auxiliary battery 23 to auxiliary load 22 without time delay. Even when the vehicle stops and the DC / DC converter 21 stops, power is supplied from the auxiliary battery 23 to the auxiliary load 22 in the same manner as described above.

<Operation of discharge circuit during normal driving>
As described above with reference to FIG. 8, when electric power is supplied from the auxiliary battery 23 to the auxiliary load 22, an ECU (not shown) is activated. The ECU turns on the system main relay 11 to connect the main battery 10 and the DC / DC converter 21. Further, the controller 70 activates the DC / DC converter 21. When the DC / DC converter 21 starts operation, as shown in FIG. 6, the output voltage Vdc of the DC / DC converter 21 becomes a target output voltage Vd0 higher than the voltage Vb of the auxiliary battery 23 (Vb ≦ Vdc = Vd0). Then, the discharge control IC 42 determines NO in step S101 of FIG. 7, turns off the first switching element 91, stops the discharge of the auxiliary battery 23, and supplies power from the auxiliary battery 23 to the auxiliary load 22. To stop.

  When the power supply from the auxiliary battery 23 to the auxiliary load 22 is stopped, the power of the main battery 10 is supplied from the DC / DC converter 21 to the auxiliary load 22 as indicated by arrows R2 and R4 in FIG. . Further, as indicated by an arrow R3 in FIG. 9, the electric power of the main battery 10 is supplied from the inverter 12 to the motor generator 13, and the vehicle travels normally. While the vehicle is running normally, the output voltage Vdc of the DC / DC converter 21 is maintained at the target output voltage Vd0 that is higher than the voltage Vb of the auxiliary battery 23. Therefore, the discharge control IC 42 performs the first switching. The element 91 is kept off.

  As described above, the power supply system 100 according to the present embodiment supplies power from the auxiliary battery 23 to the auxiliary load 22 when the vehicle in which the DC / DC converter 21 is not operating or when the vehicle is stopped. During normal traveling in which the / DC converter 21 is operating, power is continuously supplied from the DC / DC converter 21 to the auxiliary load 22.

<Operation of discharge circuit during rush current generation of auxiliary load during normal driving>
As shown in FIG. 10A, from time zero to time t1, during normal driving of the vehicle, the output voltage Vdc of the DC / DC converter 21 (indicated by a one-dot chain line in FIG. 10A) is equal to the voltage Vb of the auxiliary battery 23. Higher than the target output voltage Vd0. 10B, the output current Idc of the DC / DC converter 21 (indicated by a one-dot chain line in FIG. 10B) is the required current Ireq of the auxiliary load 22 (in FIG. 10B). (Shown by a solid line). The output current Idc at this time is smaller than the upper limit output current Idmax when the output voltage Vdc of the DC / DC converter 21 is the target output voltage Vd0.

  The auxiliary machine load 22 includes a power steering device and a small motor that drives the hydraulic device. These small motors require a large current (rush current) in a short time in order to operate rapidly when the driver operates a sudden handle or a sudden brake. For this reason, when the sudden handle or the sudden brake operation is performed at time t1 in FIG. 10B, the required current Ireq of the auxiliary machine load 22 increases rapidly after time t1, as shown by the solid line in FIG. 10B. . Accordingly, the output current Idc of the DC / DC converter 21 increases rapidly as indicated by the alternate long and short dash line in FIG. 10B. When the output current Idc of the DC / DC converter 21 reaches the upper limit output current Idmax at time t2 in FIG. 10B, the DC / DC converter 21 converts the output voltage Vdc to the target output voltage as shown by a one-dot chain line in FIG. 10A. Vd0 cannot be maintained, and the output voltage Vdc of the DC / DC converter 21 starts to decrease from the target output voltage Vd0.

  10A, when the output voltage Vdc of the DC / DC converter 21 becomes lower than the voltage Vb of the auxiliary battery 23, that is, the voltage Vb of the auxiliary battery 23 is higher than the output voltage Vdc of the DC / DC converter 21. Is higher (Vb> Vdc), the discharge control IC 42 determines YES in step S101 of FIG. 7 and proceeds to step S102 to turn on the first switching element 91 and start discharging of the auxiliary battery 23. To do. Then, as indicated by a broken line in FIG. 10B, current Ib flows from auxiliary battery 23 to auxiliary load 22. At this time, the output current Id flows from the DC / DC converter 21 to the auxiliary load 22 as indicated by the arrow R4 in FIG. 11, and the current Ib flows from the auxiliary battery 23 as indicated by the arrow R1 in FIG. Therefore, power is supplied to the auxiliary load 22 from the DC / DC converter 21 and the auxiliary battery 23. When power is supplied from the auxiliary battery 23 to the auxiliary load 22, the output voltage Vdc of the DC / DC converter 21 depends on the balance between the power supplied from the DC / DC converter 21 and the power supplied from the auxiliary battery 23. The voltage is kept slightly lower than the voltage Vb of the auxiliary battery 23.

  As shown in FIG. 10B, when the operation of the abrupt steering wheel or the abrupt brake is completed at time t3, the required current Ireq of the auxiliary machine load 22 rapidly decreases from the peak current Ipeak. Then, as shown in FIG. 10A, output voltage Vdc of DC / DC converter 21 begins to rise, and output voltage Vdc of DC / DC converter 21 becomes equal to or higher than voltage Vb of auxiliary battery 23 at time t4 in FIG. 10A. (Vb ≦ Vdc). Then, the discharge control IC 42 determines NO in step S101 of FIG. 7 and turns off the first switching element 91 as shown in step S103 of FIG. Thus, after time t4 in FIG. 10B, the current Ib of the auxiliary battery 23 becomes zero. Further, after time t4 shown in FIG. 10B, the required current Ireq of the auxiliary load 22 rapidly decreases, and accordingly, the output voltage Vdc of the DC / DC converter 21 increases as shown in FIG. 10A. come.

  When the required current Ireq of the auxiliary load 22 becomes smaller than the upper limit output current Idmax of the DC / DC converter 21 at time t5 in FIG. 10B, the output voltage Vdc of the DC / DC converter 21 returns to the target output voltage Vd0. When the vehicle returns to normal running at time t6, the output voltage Vdc of the DC / DC converter 21 is maintained at the target output voltage Vd0 that is higher than the voltage Vb of the auxiliary battery 23, and the discharge control IC 42 has the first switching element. Keep 91 off.

  As described above, the sudden handle or the sudden brake operation is performed during the normal traveling, the rush current of the auxiliary load 22 is generated, and the output voltage Vdc of the DC / DC converter 21 becomes the voltage Vb of the auxiliary battery 23. When the voltage becomes lower (Vb> Vdc), the discharge control IC 42 turns on the first switching element 91 to discharge the auxiliary battery 23 and back up the power supplied to the auxiliary load 22. Further, when the rush current of the auxiliary load 22 is not generated and the output voltage Vdc of the DC / DC converter 21 does not become lower than the voltage Vb of the auxiliary battery 23, the auxiliary load 22 has a DC / DC Electric power is continuously supplied from the converter 21.

  As described above, the power supply system 100 according to the present embodiment continuously supplies power from the DC / DC converter 21 to the auxiliary load 22 during normal running, and when the rush current of the auxiliary load 22 is generated. The power supply from the auxiliary battery 23 to the auxiliary load 22 is intermittently performed to back up the power supplied from the DC / DC converter 21.

<Charge control>
Next, the charging operation of the auxiliary battery 23 will be described with reference to FIGS. Immediately after the use of the auxiliary battery 23 is started, the controller 70 detects the charge / discharge current of the auxiliary battery 23 by the current sensor 26, integrates the current Ib, and estimates the SOC of the auxiliary battery 23. Is going. Immediately after the use of the auxiliary battery 23 is started, for example, when the ignition switch is turned on for the first time after the electric vehicle equipped with the auxiliary battery 23 is completed. As shown in step S201 in FIG. 12, the controller 70 compares the SOC calculated by current integration with a charging start threshold value Ca that is a predetermined threshold value. When the SOC of the auxiliary battery 23 becomes equal to or lower than the charging start threshold value Ca, the process proceeds to step S202 in FIG. 12, and the voltages at the intermediate points 51 and 52 detected by the discharge control IC 42 are set to the voltage Vb of the auxiliary battery 23, respectively. As the output voltage Vdc of the DC / DC converter 21, the output voltage Vdc of the DC / DC converter 21 and the voltage Vb of the auxiliary battery 23 are compared. If the output voltage Vdc of the DC / DC converter 21 is equal to or higher than the voltage Vb of the auxiliary battery 23 in step S202 of FIG. 12 (Vdc ≧ Vb), the process proceeds to step S203 of FIG. The start command 30 is output and the voltage Vb of the auxiliary battery 23 detected by the discharge control IC 42 is output to the charge control IC 35.

  When the charging circuit 30 is activated, the controller 70 proceeds to step S204 in FIG. 12, calculates the SOC of the auxiliary battery 23 by integrating the charging current detected by the current sensor 26 as in step S201, and calculates the auxiliary battery 23. The operation of the charging circuit 30 is maintained until the SOC of the battery reaches the charge stop threshold Cb or more, and the voltage Vb of the auxiliary battery 23 detected by the discharge control IC 42 is output to the charge control IC 35 (step S203). At this time, as shown in FIG. 13, the current Ib flows from the DC / DC converter 21 to the auxiliary battery 23 via the charging circuit 30, and the auxiliary battery 23 is charged. Then, when the SOC of the auxiliary battery 23 becomes equal to or higher than the charging stop threshold Cb in step S204 of FIG. 12, the controller 70 proceeds to step S205 and outputs a command to stop the operation of the charging circuit 30 to the charging control IC 35.

  On the other hand, if the controller 70 determines NO in step S201 in FIG. 12 and NO in step S202 in FIG. 12, the controller 70 returns to the beginning without starting the charging circuit 30, and steps S201 to S205. repeat.

  When the activation command from the controller 70 is input, the charging control IC 35 alternately turns on and off the second switching element 92 and the third switching element 93 to change the output voltage Vdc of the DC / DC converter 21 to the auxiliary battery 23. The charging voltage is reduced to Vch. The charging voltage Vch is equal to or slightly higher than the voltage Vb of the auxiliary battery 23 input from the controller 70. Since the voltage Vb of the auxiliary battery 23 changes from V0 to V100 depending on the SOC as shown in FIG. 6, the charge control IC 35 uses the second switching element based on the voltage Vb of the auxiliary battery 23 input from the controller 70. The charging voltage Vch is adjusted to be equal to or slightly higher than the voltage Vb of the auxiliary battery 23 by changing the duty ratio of the second switching element 92 and the third switching element 93. The charging voltage Vch of the auxiliary battery 23 may not be changed, and charging may be performed as V100 that is the full charging voltage of the auxiliary battery 23 described with reference to FIG.

<Charging operation of auxiliary battery during normal driving>
As described above with reference to FIG. 9, when the vehicle is traveling normally, the power of the main battery 10 is supplied from the DC / DC converter 21 to the auxiliary load as indicated by arrows R2 and R4 in FIG. 22 is supplied. Since the output voltage Vdc of the DC / DC converter 21 is maintained at the target output voltage Vd0 higher than the voltage Vb of the auxiliary battery 23, the discharge control IC 42 keeps the first switching element 91 off. When the activation command from the controller 70 is input to the charging control IC 35, the charging control IC 35 alternately turns on / off the second switching element 92 and the third switching element 93 to change the output voltage Vdc of the DC / DC converter 21. The voltage is reduced to the charging voltage Vch, and the auxiliary battery 23 is charged as indicated by an arrow R5 in FIG.

  In the charge control described above, the charge start threshold value Ca and the charge stop threshold value Cb can take various values. For example, the charge start threshold value Ca is set so that the voltage Vb of the auxiliary battery 23 does not become too low. As the charging stop threshold Cb is higher, the vehicle stop period can be lengthened. However, if the charging stop threshold Cb is too high, the auxiliary battery 23 may be overcharged, so that it may be about 80-90%. As described above, the power supply from the auxiliary battery 23 is performed when the DC / DC converter 21 is stopped when the vehicle is started or stopped, or when the rush current is applied to the auxiliary load 22. In this case, power is not supplied from the auxiliary battery 23 to the auxiliary load 22 during normal travel. For this reason, the discharge amount of the auxiliary battery 23 is small and the required charge amount is also small.

<SOC estimated value replacement operation and current sensor zero point correction operation>
Next, the estimated SOC value replacement operation in power supply system 100 and the zero point correction operation of current sensor 26 will be described.

  As shown in step S <b> 301 of FIG. 14, the controller 70 outputs a command to stop the charging circuit 30. In response to this command, the charging control IC 35 fixes the second switching element 92 and the third switching element 93 to the OFF state so that no charging current flows from the DC / DC converter 21 to the auxiliary battery 23.

  Next, the controller 70 proceeds to step S302 in FIG. 14, and increases the output target voltage of the DC / DC converter 21 to Vd1 (Vd1> Vd0> V100) higher than the normal Vd0. Since Vd0 is higher than the voltage V100 when the SOC of the auxiliary battery 23 is 100%, the discharge current does not flow from the auxiliary battery 23 to the low voltage line 64 even if the discharge circuit 40 is not stopped. However, since the output voltage Vdc of the DC / DC converter 21 may be lower than the target voltage Vd0 depending on the output current to the auxiliary load 22, the zero point correction operation of the current sensor 26 and the SOC estimated value replacement The target voltage of the DC / DC converter 21 is set to Vd1 so that the charge / discharge current of the auxiliary battery 23 can be kept as zero as possible during operation. Thereby, the output voltage of the DC / DC converter 21 becomes Vd1 (> V100).

  In step S303, the controller 70 sets the voltages at the intermediate points 51 and 52 detected by the discharge control IC 42 as the voltage Vb of the auxiliary battery 23 and the output voltage Vdc of the DC / DC converter 21, respectively. The voltage Vdc and the voltage Vb of the auxiliary battery 23 are compared. When the output voltage Vdc of the DC / DC converter 21 is higher than the voltage Vb of the auxiliary battery 23, it is determined that no rush current is generated and the charge / discharge current of the auxiliary battery 23 is maintained at zero. In step S305, the estimated SOC value replacement operation and the zero point correction operation of the current sensor 26 are performed.

  On the other hand, if the controller 70 determines NO in step S303, a rush current is generated, the auxiliary battery 23 is discharged from the auxiliary load 22, and the charge / discharge current of the auxiliary battery 23 is If it is determined that the current is not zero, the process proceeds to step S304, waits for a predetermined time until the rush current converges, and then executes step S303 again. If the controller 70 determines YES in step S303, the controller 70 proceeds to step S305, and performs the SOC estimated value replacement operation and the zero point correction operation of the current sensor 26.

  After proceeding to step S305, the controller 70 detects the temperature Tb of the auxiliary battery 23 by the temperature sensor 25. Then, the polarization elimination time of the auxiliary battery 23 is calculated from the detected temperature Tb and the map (map shown in FIG. 3) showing the relationship between the temperature Tb of the auxiliary battery 23 stored in the memory 72 and the polarization elimination time. Obtained and waits until the polarization elimination time elapses as shown in step S306 in FIG. When the polarization elimination time has elapsed, the controller 70 detects the voltage Vb of the auxiliary battery 23 by the voltage sensor 24 as shown in step S307 of FIG. At this time, the current Ib of the auxiliary battery 23 is kept at zero, and since the polarization elimination time has elapsed since the current Ib became zero, the voltage Vb detected by the voltage sensor 24 is the auxiliary battery 23. OCV.

  When the voltage Vb, which is the OCV of the auxiliary battery 23, is detected, the controller 70 proceeds to step S308, and determines whether or not the voltage Vb is in the second region where the rate of change of the OCV with respect to the SOC is greater than a predetermined threshold. . In the case of the auxiliary battery 23, as described above, in the region where the change rate of the OCV with respect to the change rate of the SOC is 1/10 or more, the OCV changes when the SOC changes, and the SOC is accurately calculated based on the OCV. This is the second region that can be estimated. As shown in FIG. 2, there are two regions where the OCV is between OCV0 and OCV1 (SOC is between 0% and SOC1) and the OCV is between OCV2 and OCV100 (SOC is between SOC2 and 100%). This is the second area. Further, when the OCV is between OCV1 and OCV2 (SOC is between SOC1 and SOC2), the change ratio of the OCV to the SOC is less than 1/10, and this is the first region in which it is difficult to estimate the SOC based on the OCV. Therefore, when the voltage Vb, which is the OCV of the auxiliary battery 23, is less than OCV1, or the voltage Vb, which is the OCV of the auxiliary battery 23, exceeds OCV2, the OCV of the auxiliary battery 23 is in the second region, and the OCV When the voltage Vb is OCV1 ≦ Vb ≦ OCV2, the OCV of the auxiliary battery 23 is in the first region.

  Therefore, when the voltage Vb, which is the OCV of the auxiliary battery 23, exceeds the OCV2 or is lower than the OCV1, the controller battery 23 is in the second region, and the SOC is accurately determined based on the OCV. It is determined that estimation is possible, and the process proceeds to step S309 in FIG.

  As shown in step S309 in FIG. 14, the controller 70 uses the voltage Vb, which is the OCV of the auxiliary battery 23 detected in step S307, and the SOC-OCV characteristic map shown in FIG. The OCV of the machine battery 23 is estimated. For example, when the voltage Vb, which is the OCV of the auxiliary battery 23, is OCV3 shown in FIG. 2, the SOC of the auxiliary battery 23 is estimated as SOC3 from the map. Then, the estimated SOC value that has been estimated based on the current integration is replaced with a highly accurate OCV estimated value. After that, the SOC is estimated by current integration based on the estimated value of the replaced SOC. When the replacement of the estimated SOC value is completed, the controller 70 proceeds to step S311 in FIG.

  On the other hand, if controller 70 determines NO in step S309 in FIG. 14, it is determined that the OCV of auxiliary battery 23 is in the first region and it is difficult to estimate the SOC from the OCV, and the process proceeds to step S310 in FIG. Then, the SOC is not estimated by the OCV, and the SOC value estimated by the current integration is maintained, and the process proceeds to step S311.

  The controller 70 performs zero point correction of the current sensor 26 in step S311. Now, the charging circuit 30 is stopped, and the output voltage Vdc of the DC / DC converter 21 is higher than V100, which is the maximum voltage of the auxiliary battery 23. Therefore, the charging / discharging current of the auxiliary battery 23 is zero. It has become. Therefore, the output of the current sensor 26 in this state is corrected to an output when the current Ib of the auxiliary battery 23 is zero. Thereby, an error due to a temperature rise or the like of the current sensor 26 can be corrected, and the estimation accuracy of the SOC based on the current integration can be improved.

  After performing the zero point correction of the current sensor 26 in step S311, the controller 70 restarts the charging circuit 30, returns the output target voltage of the DC / DC converter 21 to the normal Vd0, and returns to the normal operation.

  As described above, the power supply system 100 of the present embodiment replaces the estimated SOC value with the highly accurate OCV estimated value when the OCV of the auxiliary battery 23 is in the second region, and integrates the current until then. The SOC estimation error estimated by step 1 is once canceled and the zero point of the current sensor 26 is corrected, and then the SOC is estimated by the next current integration. Therefore, even if the SOC changes, the OCV hardly changes. It is possible to accurately estimate the SOC of the auxiliary battery 23 having the area and the second area where the OCV changes with respect to the change in the SOC.

  In addition, the power supply system 100 according to the present embodiment raises the output voltage Vdc of the DC / DC converter 21 to Vd1 and stops the charging circuit 30 so that the current Ib of the auxiliary battery 23 becomes zero. Since the OCV measurement and the zero point correction of the current sensor 26 are performed, the wear of the auxiliary relay 28 caused by turning on / off the auxiliary relay 28 is suppressed, and the estimated SOC value replacement and the current sensor 26 are performed. Zero point correction can be performed. Furthermore, since the auxiliary relay 28 is turned on, power can be supplied from the auxiliary battery 23 to the auxiliary load 22 when a large rush current is generated.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. Parts similar to those of the second embodiment described above with reference to FIGS. 5 to 14 are denoted by the same reference numerals, and description thereof is omitted.

  In the power supply system 200 of the present embodiment, the direction of the parasitic diode 91b of the first switching element 91 of the discharge circuit 40 of the power supply system 100 described with reference to FIGS. The configuration is the same as that of the power supply system 100 except that the auxiliary battery 23 side and the anode is the auxiliary load 22 side. Instead of the first switching element 91, a switching element including a parasitic diode in which the anode is the auxiliary battery 23 side and the cathode is the auxiliary load 22 side, and the cathode is the auxiliary battery 23 side and the anode is the auxiliary load. A switching element including a parasitic diode on the 22 side may be connected in series.

  Due to this configuration, the power supply system 200 shown in FIG. 15 has an auxiliary circuit 23 that does not turn on even if the voltage Vb of the auxiliary battery 23 becomes higher than the output voltage Vdc of the DC / DC converter 21. The discharge current from the machine battery 23 to the auxiliary machine load 22 does not flow.

<SOC estimated value replacement operation and current sensor zero point correction operation>
Next, the estimated SOC value replacement operation in power supply system 200 and the zero point correction operation of current sensor 26 will be described.

  As shown in step S <b> 401 of FIG. 16, the controller 70 estimates the temperature of the switching element of the DC / DC converter 21. Various methods can be used to estimate the switching temperature. For example, the switching temperature may be estimated based on the energization current of the DC / DC converter 21, the temperature of the cooling water, the cooling air, the air volume, and the like. After estimating the temperature of the switching element of the DC / DC converter 21, the controller 70 proceeds to step S402 in FIG. 16, and determines whether the estimated temperature of the switching element is equal to or lower than a predetermined threshold value. Here, the predetermined threshold is, for example, a value obtained by subtracting the temperature rise of the element temperature due to the rush current from the heat resistance temperature of the switching element, that is, a temperature that is not expected to exceed the heat resistance temperature even when a rush current occurs. Also good.

  If the controller 70 determines YES in step S402 of FIG. 16, the controller 70 proceeds to step S403 of FIG. 16 and outputs a command to stop the charging circuit 30 and the discharging circuit 40. By this command, the second switching element 92 and the third switching element 93 of the charging circuit 30 are turned off. Further, the first switching element 91 of the discharge circuit 40 is also turned off. In the power supply system 200 of the present embodiment, the parasitic diode 91b of the first switching element 91 of the discharge circuit 40 is arranged in such a direction that current does not flow from the auxiliary battery 23 to the auxiliary load 22, so that DC / DC Even when output voltage Vdc of converter 21 is lower than voltage Vb of auxiliary battery 23, current Ib does not flow from auxiliary battery 23 toward auxiliary load 22. Therefore, when the charging circuit 30 and the discharging circuit 40 are stopped, the auxiliary battery 23 is completely disconnected from the DC / DC converter 21 and the auxiliary load 22 and becomes independent.

  After stopping the charging circuit 30 and the discharging circuit 40 in step S403, the controller 70 proceeds to step S305 in FIG. 16 to detect the temperature Tb of the auxiliary battery 23 as described with reference to FIG. Then, after waiting for the polarization time to be eliminated in step S306, the voltage Vb which is the OCV of the auxiliary battery 23 is acquired in step S307. If the voltage Vb of the auxiliary battery 23 exceeds OCV2 or is lower than OCV1 in step S308, it is determined that the OCV of the auxiliary battery 23 is in the second region.

  If the auxiliary battery 23 is in the second region in step S308 of FIG. 16, the controller 70 determines that the SOC can be accurately estimated based on the OCV, and proceeds to step S309. Then, as shown in step S309, the controller 70 uses the voltage Vb, which is the OCV of the auxiliary battery 23 detected in step S307, and the SOC-OCV characteristic map shown in FIG. The OCV of the battery 23 is estimated, and the estimated SOC value that has been estimated based on the current integration is replaced with a highly accurate OCV estimated value. When the replacement of the estimated value of the SOC is completed, the controller 70 proceeds to step S311 in FIG. 16 and corrects the zero point of the current sensor 26.

  If the controller 70 determines NO in step S308, the controller 70 determines that the OCV of the auxiliary battery 23 is in the first region and it is difficult to estimate the SOC from the OCV, and proceeds to step S310 in FIG. The SOC value estimated by the current integration is maintained without proceeding to step S311 in FIG. 16, and the zero point correction of the current sensor 26 is performed.

  Further, in the case of NO in step S402 in FIG. 16, the controller 70 predicts that the switching element of the DC / DC converter 21 will exceed the heat resistant temperature when a rush current is generated, and the process proceeds to step S404 in FIG. Steps S301 to S311 shown in FIG. 14 are executed in which the estimated SOC value replacement operation and the zero point correction operation of the current sensor 26 are performed without stopping the discharge circuit 40.

  In the present embodiment, the charging circuit 30 and the discharging circuit 40 are stopped depending on the temperature of the switching element of the DC / DC converter 21. However, the present invention is not limited to this. For example, depending on the situation of the auxiliary load 22 The charging circuit 30 and the discharging circuit 40 may be stopped. For example, when an auxiliary machine such as a defogger or cigar lighter is operating, if the discharge circuit 40 is disconnected, the power supplied to the auxiliary load 22 may be insufficient. The process proceeds to step S404 in FIG. 16 without stopping the discharge circuit 40, and executes steps S301 to S311 shown in FIG. 14 to perform the SOC estimated value replacement operation and the zero point correction operation of the current sensor 26.

  After performing the zero point correction of the current sensor 26 in step S311 of FIG. 16, the controller 70 restarts the charging circuit 30 and the discharging circuit 40, returns the output target voltage of the DC / DC converter 21 to the normal Vd0, Return to normal operation.

  The power system 200 according to the third embodiment described above has the same effect as that of the power system 100 according to the second embodiment, and the output target of the DC / DC converter 21 as in the case of the power system 100 according to the second embodiment. Since it is not necessary to raise the voltage to Vd1 higher than the normal Vd0, there is an effect that auxiliary equipment loss can be suppressed.

  In the embodiment described above, the battery 1 and the auxiliary battery 23 are both described as having a central first region and two second regions at both ends, as shown in FIG. The present invention can also be applied to a power supply system including a secondary battery having a plurality of first regions and three or more second regions.

  1 battery, 2 connection line, 3 relay, 4 load, 5,24 voltage sensor, 6,25 temperature sensor, 7,26 current sensor, 8,70 controller, 9,100,200 power supply system, 10 main battery, 11 system Main Relay, 12 Inverter, 13 Motor Generator, 21 Converter, 22 Auxiliary Load, 23 Auxiliary Battery, 27 Fuse, 28 Auxiliary Relay, 29 Zener Diode, 30 Charging Circuit, 32 Reactor, 34 Capacitor, 40 Discharge Circuit, 51 , 52, 54 Intermediate point, 53 Connection point, 55, 57 Input end, 56, 58 Output end, 61 High voltage line, 63 Connection line, 64 Low voltage line, 65 First auxiliary battery line, 66a Charging circuit input line, 66b Charging circuit output line, 67 2nd auxiliary battery Line, 68, 69 connection line, 71, 81 CPU, 72, 82 memory, 83 sensor / equipment interface, 84 data bus, 91 first switching element, 91a, 91b parasitic diode, 92 second switching element, 92a, 93a parasitic Diode, 93 third switching element.

Claims (1)

A secondary battery,
A voltage sensor for detecting a voltage of the secondary battery;
A current sensor for detecting a charge / discharge current of the secondary battery;
A controller for integrating a charge / discharge current of the secondary battery detected by the current sensor to estimate a charge rate of the secondary battery, and a power supply system comprising:
The controller is
The open-circuit voltage of the secondary battery is detected by the voltage sensor with the charge / discharge current of the secondary battery as zero,
When the detected open-circuit voltage is in a region where the change rate of the open-circuit voltage with respect to the charge rate of the secondary battery is larger than a predetermined threshold, charging of the secondary battery estimated by integrating charge / discharge current Replacing the rate with a charge rate estimated based on the open circuit voltage;
Power supply system characterized by

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