Adjusting electric energy of plurality of batteries mounted in traveling vehicle

A power-supply control device includes: a distribution adjustment unit adjusting electric energy; and a loss comparison unit comparing losses in power running and regeneration and determining, with respect to power running and regeneration, whether a loss in a current state is smaller. Further, the distribution adjustment unit adjusts the electric energy by performing the distribution in accordance with the remaining capacity ratio in the current state in a case where it is determined that the loss in power running is smaller when the current state is a power running state or in a case where it is determined that the loss in regeneration is smaller when the current state is a regeneration state.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2018-077525 filed in Japan on Apr. 13, 2018.

BACKGROUND

The present disclosure relates to a power-supply control device.

Japanese Laid-open Patent Publication No. 2014-023374 discloses that input/output electric power is distributed to two electric storage devices in such a manner that a total loss of an internal resistance loss of a first electric storage device and an internal resistance loss of a second electric storage device is decreased in a power-supply control device that controls input/output electric power of a plurality of electric storage devices.

SUMMARY

There is a need for providing a power-supply control device that can reduce a loss in whole traveling when adjusting electric energy of a plurality of electric storage devices mounted in a vehicle.

According to an embodiment, a power-supply control device, that is mounted in a vehicle including a plurality of electric storage devices and that controls charging/discharging with respect to the plurality of electric storage devices, includes: a distribution adjustment unit adjusting electric energy in a manner that a difference between a remaining capacity of a first electric storage device and a remaining capacity of a second electric storage device becomes small when each of the electric storage devices is charged/discharged and distributing input/output electric power to the first electric storage device and the second electric storage device on a basis of a remaining capacity ratio between the remaining capacity of the first electric storage device and the remaining capacity of the second electric storage device when adjusting the electric energy; and a loss comparison unit comparing a loss in power running with a loss in regeneration in a case where an amount for the adjustment of the electric energy becomes the same between in power running and in regeneration and determining, with respect to power running and regeneration, whether a loss in a current state is smaller. Further, the distribution adjustment unit adjusts the electric energy by performing the distribution in accordance with the remaining capacity ratio in the current state in a case where it is determined that the loss in power running is smaller when the current state is a power running state or in a case where it is determined that the loss in regeneration is smaller when the current state is a regeneration state.

DETAILED DESCRIPTION

In a case where a distribution is performed in consideration of remaining capacity of each of the electric storage devices, a magnitude of the generated loss differs between power running and during regeneration even when an amount to be adjusted of an electric power amount (electric power adjustment amount) by distribution is the same. Thus, in a configuration in which a plurality of electric storage devices is switched between a power running state and a regeneration state, for example, in a case of being mounted in a vehicle, it is important for reducing a loss in whole traveling whether the distribution for an electric energy adjustment is to be performed in the power running state or the distribution for an electric energy adjustment is to be performed in the regeneration state. In a configuration described in Japanese Laid-open Patent Publication No. 2014-023374, the distribution is performed in consideration of a plurality of losses. However, the losses are based on the losses which are generated in a current state, and the time for power running and the time for regeneration are not considered. Thus, there is a possibility that a loss in the whole traveling does not become minimum.

In the following, a power-supply control device according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments described below.

FIG. 1is a diagram schematically illustrating a vehicle in which a power system according to an embodiment is mounted. A power system100includes a first battery B1, a second battery B2, an electric power adjustment unit10, an inverter (INV)20, a motor generator (MG)30, and an Electronic Control Unit (hereinafter, referred to as “ECU”)40. A vehicle Ve in which the power system100is mounted is an electric car in which power output from a motor generator30is transmitted to left and right driving wheels60aand60bthrough a differential device50. Further, a power-supply control device according to an embodiment includes the ECU40.

Each of the first battery B1and the second battery B2is a DC power supply that can be charged/discharged and includes, for example, a secondary battery, which is a nickel-metal hydride battery, a lithium ion battery or the like. The power system100includes an electric circuit in which the first battery B1and the second battery B2are connected in parallel. In power running, electric power charged in the first battery B1and the second battery B2is supplied to the motor generator30which serves as a load. In regeneration, since the motor generator30functions as a generator, electric power generated by the motor generator30is charged into the first battery B1and the second battery B2. Further, the first battery B1and the second battery B2are different kinds of secondary batteries. The first battery B1corresponds to a first electric storage device according to the present disclosure. The second battery B2corresponds to a second electric storage device according to the present disclosure.

The electric power adjustment unit10includes a first boost converter11and a second boost converter12. The first boost converter11includes two transistors T1and T2, two diodes D1and D2, and a reactor L1. The second boost converter12includes two transistors T3and T4, two diodes D3and D4, and a reactor L2. In the electric circuit of the power system100, the first boost converter11is disposed between the first battery B1and the inverter20, and the second boost converter12is disposed between the second battery B2and the inverter20. The electric power adjustment unit10adjusts input/output electric power of the first battery B1and the second battery B2by performing on/off control (switching control) on a plurality of switching elements including the transistors T1, T2, T3, and T4by the ECU40.

The inverter20is provided between the batteries B1and B2and the motor generator30. The inverter20includes an electric circuit (inverter circuit) including a plurality of switching elements in such a manner that three-phase current can be applied to a coil. The inverter20can flow currents of respective phases through coils connected to the inverter circuit.

The motor generator30is electrically connected to the inverter20, and can function as an electric motor and a generator. The motor generator30has a motor function driven by electric power supplied from each of the batteries B1and B2, and a generator function to generate electric power by driving by an external force. When the ECU40performs switching control on the plurality of switching elements of the inverter20, the motor generator30is rotationally driven. In the power running state, the vehicle Ve travels by power output from the motor generator30that is a power source for traveling. In the regeneration state, the motor generator30is driven by an external force input from the left and right driving wheels60aand60band electric power is generated by the motor generator30. The electric power generated by the motor generator30is charged into the first battery B1and the second battery B2.

The ECU40is a control device to control the power system100and control charging/discharging of the first battery B1and the second battery B2. The ECU40includes a Central Processing Unit (CPU), a storage unit that stores data such as various kinds of programs, and an arithmetic processing unit that performs various kinds of arithmetic operations. As a result of the arithmetic operations, the ECU40outputs a command signal to the electric power adjustment unit10or the inverter20. The power system100has a circuit configuration in which electric power of the plurality of batteries B1and B2can be independently output. The electric power adjustment unit10is controlled by the ECU40, whereby input/output electric power of the first battery B1and input/output electric power of the second battery B2can be respectively controlled. Further, the power system100may include, as various kinds of sensors (not illustrated), a first voltage sensor to detect voltage of the first battery B1, a second voltage sensor to detect voltage of the second battery B2, a first current sensor to detect current output from the first battery B1, and a second current sensor to detect current output from the second battery B2. Signals (signal related to measured value) from these various kinds of sensors are input into the ECU40. The ECU40can calculate remaining capacity of the first battery B1and remaining capacity of the second battery B2on the basis of the signals input from the voltage sensors and the current sensors.

When the first battery B1and the second battery B2are charged/discharged, the ECU40performs control to adjust electric energy in such a manner that a difference between the remaining capacity of the first battery B1and the remaining capacity of the second battery B2(electric energy difference) becomes smaller. (electric energy adjustment control). Also, when adjusting electric energy, the ECU40distributes input/output electric power to the first battery B1and the second battery B2on the basis of a ratio of remaining capacity between the remaining capacity of the first battery B1and the remaining capacity of the second battery B2. Moreover, when distributing input/output electric power to the first battery B1and the second battery B2, the ECU40compares a loss generated in electric energy adjustment in power running and a loss generated in electric energy adjustment in regeneration, and adjusts electric energy in a state where the loss is smaller. This is because magnitude of a generated loss varies between in power running and in regeneration even in a case where the electric power adjustment amounts are the same. As described above, when performing a distribution based on the ratio of remaining capacity for electric energy adjustment, the ECU40compares the loss in electric energy adjustment in power running and that in electric energy adjustment in regeneration, and performs the distribution based on the ratio of remaining capacity of the current state in a case where the loss in the current state is smaller. As an example,FIG. 2illustrates a case where electric energy adjustment is performed in a case where a loss in power running is smaller when a current state is a power running state.

FIG. 2is a graph for describing a case where power is discharged from the first battery B1in power running. The example ofFIG. 2is a case where the voltage V1of the first battery B1is higher than the voltage V2of the second battery B2and a case where remaining capacity A1of the first battery B1is greater than remaining capacity A2of the second battery B2. In this case (V1>V2and A1>A2), in order to reduce a difference between the remaining capacity A1and the remaining capacity A2, the remaining capacity A1of the first battery B1is reduced more in power running or the remaining capacity A2of the second battery B2is increased more in regeneration. That is, as timing to adjust electric energy, a time in power running or a time in regeneration can be selected. Moreover, when electric energy is adjusted, input/output electric power corresponding to a ratio of remaining capacity α is distributed to the first battery B1and the second battery B2. The ratio of remaining capacity α indicates the remaining capacity A1of the first battery B1to the sum of the remaining capacity A1of the first battery B1and the remaining capacity A2of the second battery B2. The ratio of remaining capacity α becomes a predetermined value within a range of 0 to 1 (0≤α≤1). Then, the ECU40adjusts electric energy by using the ratio of remaining capacity α and a distribution ratio β.

FIG. 3is a graph illustrating a relationship between a ratio of remaining capacity α and a distribution ratio β in power running. The distribution ratio β indicates input/output electric power of the first battery B1to the sum of the input/output electric power of the first battery B1and input/output electric power of the second battery. The distribution ratio β becomes a predetermined value within a range of 0 to 1 (0≤β≤1). The ECU40determines the distribution ratio β on the basis of the ratio of remaining capacity α in a manner of the relationship illustrated inFIG. 3. Then, the ECU40distributes, with respect to requested electric power requested to the power system100, input/output electric power corresponding to the distribution ratio β to the first battery B1and the second battery B2. Since an example illustrated inFIG. 3indicates the time of power running, the distribution ratio β ofFIG. 3is a distribution ratio in power running and indicates output electric power (discharged amount) of the first battery B1to the sum of the output electric power (discharged amount) of the first battery B1and output electric power (discharged amount) of the second battery B2. In power running, the distribution ratio β changes in a manner of becoming large as the ratio of remaining capacity α is increased toward 1.0. Further, the distribution ratio β becomes 0.5 when the ratio of remaining capacity α is 0.5. When the ratio of remaining capacity α is greater than 0.5, it is indicated that the remaining capacity A1of the first battery B1is large. Thus, the distribution ratio β becomes a value greater than 0.5 in such a manner that a reduction amount of the remaining capacity A1by power running becomes greater. Moreover, in power running, the distribution ratio β becomes 0 in a case where the ratio of remaining capacity α is a value close to 0 (within predetermined range). In contrast, the distribution ratio β becomes 1.0 in a case where the ratio of remaining capacity α is a value close to 1 (within predetermined range). In power running, the distribution ratio β corresponding to the ratio of remaining capacity α is determined on the basis of the relationship ofFIG. 3. For example, when the ratio of remaining capacity α in the example ofFIG. 2(V1>V2and A1>A2) is α1, the ratio of remaining capacity α1becomes a value greater than 0.5 and a distribution ratio β in power running which ratio corresponds to this ratio of remaining capacity α1is set to 0.7 (seeFIG. 3). On the other hand, in regeneration, a relationship with a distribution ratio β is reversed from that in power running.

FIG. 4is a graph illustrating a relationship between a ratio of remaining capacity α and a distribution ratio β in regeneration. Since an example ofFIG. 4indicates time of regeneration, the distribution ratio β ofFIG. 4is a distribution ratio in regeneration and indicates input power (charged amount) of the first battery B1to the sum of the input electric power (charged amount) of the first battery B1and input power (charged amount) of the second battery B2. In regeneration, the distribution ratio β changes in a manner of becoming small as the ratio of remaining capacity α is increased toward 1.0. Further, when the ratio of remaining capacity α is 0.5, the distribution ratio β in regeneration becomes 0.5. When the ratio of remaining capacity α is greater than 0.5, it is indicated that the remaining capacity A1of the first battery B1is large. Thus, the distribution ratio β in regeneration becomes a value smaller than 0.5 in such a manner that the remaining capacity A1is not increased much by regeneration. Moreover, in regeneration, the distribution ratio β becomes 1.0 in a case where the ratio of remaining capacity α is a value close to 0 (within predetermined range). In contrast, the distribution ratio β becomes 0 in a case where the ratio of remaining capacity α is a value close to 1 (within predetermined range). In regeneration, the distribution ratio β corresponding to the ratio of remaining capacity α is determined on the basis of the relationship illustrated inFIG. 4. For example, with respect to the ratio of remaining capacity α1in the above-described example illustrated inFIG. 2(V1>V2and A1>A2), the distribution ratio β in regeneration which ratio corresponds to the ratio of remaining capacity α1becomes 0.3 (seeFIG. 4). As illustrated inFIG. 3andFIG. 4, a relationship between a ratio of remaining capacity α and a distribution ratio β becomes symmetrical between power running and regeneration.

Then, when distributing input/output electric power by using a relationship between the ratio of remaining capacity α and the distribution ratio β, the ECU40compares a loss generated in an electric energy adjustment in power running and a loss generated in an electric energy adjustment in regeneration, and performs distribution in one state where the is relatively small.

FIG. 5is a graph illustrating a relationship between the electric power adjustment amount and the loss. An electric power adjustment amount Q is an amount to reduce a difference between the remaining capacity A1of the first battery B1and the remaining capacity A2of the second battery B2. This electric power adjustment amount Q corresponds to a distribution ratio β in each of power running and regeneration. Then, there is a case where the electric power adjustment amount Q becomes the same value (equal electric power adjustment amount) between in power running and in regeneration. For example, the electric power adjustment amount Q becomes the same (electric power adjustment amount Q1) in a case where a distribution ratio β of the first battery B1is 0.7 in power running and a case where the distribution ratio β of the first battery B1is 0.3 in regeneration. Even in a case of an equal adjustment amount such as this electric power adjustment amount Q1, a loss generated in power running and a loss generated in regeneration become different in magnitude. As illustrated inFIG. 5, a loss in a case of the electric power adjustment amount Q1of when the distribution ratio β in power running is 0.7 is smaller than a loss in a case of the electric power adjustment amount Q1of when the distribution ratio β in regeneration is 0.3. In an example illustrated inFIG. 5, in a case of the equal electric power adjustment amount, a loss becomes smaller when electric energy is adjusted in power running. Then, since a power running state and a regeneration state are repeated in utilization of the power system100in normal traveling by the vehicle Ve, it becomes possible to reduce a loss in whole traveling by performing electric energy adjustment in one of power running and regeneration which one has a smaller loss.

Also, a graph of a loss illustrated inFIG. 5indicates a loss generated in the above-described relationship illustrated inFIG. 2(V1>V2and A1>A2). A loss of a battery is expressed by the product of a square of current and internal resistance. In a case where the internal resistance of a battery is constant, a loss becomes smaller when a current value is smaller. Then, since electric power is expressed by the product of a current value and a voltage value, the voltage value and the current value are inversely proportional to each other in a case where the electric power is constant. From these relationships, a loss becomes smaller when a voltage value is greater in a case where internal resistance of a battery is constant. In the relationship illustrated inFIG. 2, a loss becomes smaller when electric energy is adjusted with the first battery B1as an object since the voltage V1of the first battery B1is higher than the voltage V2of the second battery B2. Moreover, since the first battery B1has greater remaining capacity than the second battery B2, a loss is smaller when the remaining capacity A1is reduced in power running. Thus, in the graph of a loss illustrated inFIG. 5, the smallest value (minimum value) of the loss is on a side where the distribution ratio β in power running is greater than 0.5.

FIG. 6is a flowchart illustrating a control flow of electric energy adjustment. The control illustrated inFIG. 6is performed by the ECU40.

The ECU40determines whether an electric energy adjustment condition is satisfied (Step S1). In Step S1, it is determined whether a difference between remaining capacity A1of the first battery B1and remaining capacity A2of the second battery B2is equal to or greater than a predetermined value. In a case where the difference between the remaining capacity A1and the remaining capacity A2is equal to or greater than the predetermined value, it is determined that the electric energy adjustment condition is satisfied. Alternatively, it is determined in Step S1whether requested electric power (output request) to the power system100is equal to or higher than a predetermined value. In a case where the requested electric power is equal to or higher than the predetermined value, it is determined that the electric energy adjustment condition is satisfied. The ECU40can calculate the requested electric power on the basis of an accelerator position and vehicle speed. Then, in a case where the electric energy adjustment condition is not satisfied and negative determination is made in Step S1(NO in Step S1), the control routine ends.

In a case where the electric energy adjustment condition is satisfied and positive determination is made in Step S1(YES in Step S1), the ECU40calculates the loss generated when distribution according to the ratio of remaining capacity α is performed in a current state (Step S2). In Step S2, the loss is calculated by utilization of a distribution ratio β determined according to the ratio of remaining capacity α. Further, the current state indicates which of a power running state and a regeneration state is a current state. In a case where the current state is the power running state, the loss in power running which loss is generated when electric energy adjustment is performed is calculated by utilization of the distribution ratio β in power running in Step S2. On the other hand, in a case where the current state is the regeneration state, the loss in regeneration which loss is generated when electric energy adjustment is performed is calculated by utilization of the distribution ratio β in regeneration in Step S2. Then, the loss calculated in Step S2is a total loss in an electric system. The total loss in the electric system is the loss generated in the whole power system100and is the sum of the loss in the first battery B1, the loss in the second battery B2, the loss in the first boost converter11, the loss in the second boost converter12, the loss in the inverter20, and the loss in the motor generator30. A processing unit in Step S2is a unit to estimate an electric power loss generated when distribution is performed in the current state.

The ECU40calculates a loss generated when distribution is performed in a state which is opposite to the current input/output state but an electric power adjustment amount is the same (Step S3). In Step S3, a loss generated when distribution is performed for an adjustment of electric energy equal to that in Step S2is calculated with respect to the state opposite to the current state in Step S2, that is, a state in which an absolute value of electric power is the same but a positive/negative sign thereof is opposite and in which power running becomes regeneration and vice versa. Output (discharging) by power running is indicated in a case where a sign of electric power is positive, and input (charging) by regeneration is indicated in a case where a sign of electric power is negative. A processing unit in Step S3is a unit to estimate a loss generated when the distribution is performed in the state opposite to the current state.

Here, a process in Step S2and Step S3in which the process is performed when the current state is the power running state will be described with reference toFIG. 7andFIG. 8. As illustrated inFIG. 7, when an output request (requested electric power) in power running is 30 kW, the first battery B1outputs 21 kW and the second battery B2outputs 9 kW in a case where a distribution ratio β according to a ratio of remaining capacity α becomes 7:3. The electric power adjustment amount in this power running becomes 12 kW. In Step S2, a loss in the current state (loss in power running) is calculated with respect to the relationship ofFIG. 7. As illustrated inFIG. 8, a state opposite to the relationship ofFIG. 7is a case where an input request (requested electric power) in regeneration is 30 kW, a distribution ratio β in regeneration is 3:7, and an electric power adjustment amount becomes 12 kW that is the same with that in power running. In this regeneration, the first battery B1inputs 9 kW and the second battery B2inputs 21 kW. In Step S3, a loss in an opposite state of the current state (loss in regeneration) is calculated with respect to a relationship illustrated inFIG. 8.

Refer toFIG. 6, again. When calculating a loss in the current state and that in the opposite state, the ECU40determines whether the loss in the current state is smaller than the loss in the opposite state of the current state (Step S4). In Step S4, the loss calculated in Step S2and the loss calculated in Step S3are compared and it is determined which of the losses is smaller. For example, in a case where the current state in Step S2is the power running state, it is determined in Step S4whether a loss estimated to be generated when distribution is performed in the power running state is smaller than a loss estimated to be generated when distribution is performed in the subsequent regeneration state. Alternatively, in a case where the current state is the regeneration state in Step S2, it is determined in Step S4whether a loss estimated to be generated when distribution is performed in the regeneration state is smaller than a loss estimated to be generated when distribution is performed in the subsequent power running state.

In a case where positive determination is made in Step S4(YES in Step S4), the ECU40performs the distribution according to the ratio of remaining capacity α in the current state (Step S5). In Step S5, in a case where the current state is the power running state, electric energy is adjusted by the distribution of the output electric power corresponding to the distribution ratio β in power running to the first battery B1and the second battery B2. Alternatively, in Step S5, in a case where the current state is the regeneration state, electric energy is adjusted by the distribution of the input electric power corresponding to the distribution ratio β in regeneration to the first battery B1and the second battery B2. In this Step S5, input/output electric power based on requested electric power is distributed according to the distribution ratio β. Then, the control routine ends when control in Step S5is performed.

On the other hand, in a case where negative determination is made in Step S4(NO in Step S4), the distribution according to the ratio of remaining capacity α is not performed in the current state and the control routine ends. The case where negative determination is made in Step S4indicates that a loss becomes smaller when distribution of the same electric power adjustment amount is performed in the state opposite to the current state. Thus, in a case where negative determination is made in Step S4, the ECU40performs the distribution of the same electric power adjustment amount in a case where a state subsequently becomes the state opposite to the current state. For example, in a case where negative determination is made in Step S4when the current state is the power running state, the ECU40performs the distribution of an equal electric power adjustment amount corresponding to the ratio of remaining capacity α when the current state becomes the regeneration state. Alternatively, in a case where negative determination is made in Step S4when the current state is the regeneration state, the ECU40performs distribution of an equal electric power adjustment amount corresponding to the ratio of remaining capacity α when the current state becomes the power running state.

As described above, in the embodiment, when the distribution according to a ratio of remaining capacity α is performed for electric energy adjustment, a loss generated in power running and a loss generated in regeneration are compared, and distribution according to the ratio of remaining capacity α is performed in a current state in a case where a loss in the current state is smaller. On the other hand, in a case where a loss becomes smaller when the distribution of an equal electric power adjustment amount is performed in the state opposite to the current state, the distribution is not performed in the current state and the distribution is performed when a state subsequently becomes the state opposite to the current state. Accordingly, it is possible to reduce a loss in whole traveling in consideration of both power running and regeneration.

In the above-described embodiment, a case is described where the first battery B1is discharged and the remaining capacity A1is reduced in power running in the example ofFIG. 2(V1>V2and A1>A2). However, the present disclosure is not limited to this. For example, as illustrated inFIG. 9,FIG. 10, andFIG. 11, it is possible to perform the distribution in a case which is different from the above-described case.

FIG. 9is a graph illustrating a case where a second battery B2is discharged in power running. An example ofFIG. 9is a case where the voltage V2of the second battery B2is higher than the voltage V1of the first battery B1and a case where remaining capacity A2of the second battery B2is greater than remaining capacity A1of the first battery B1. In this case (V1<V2and A1<A2), in order to reduce the difference between the remaining capacity A1and the remaining capacity A2, the remaining capacity A1of the first battery B1is increased more in regeneration or the remaining capacity A2of the second battery B2is reduced more in power running. A loss becomes small in the example ofFIG. 9in a case where the remaining capacity A2of the second battery B2having relatively high voltage is adjusted. Since the remaining capacity of the second battery B2to be adjusted is greater than that of the first battery B1, the distribution is performed in such a manner that the remaining capacity A2of the second battery B2is reduced more in power running. Accordingly, in the electric energy adjustment, it is possible to reduce a loss in whole traveling in consideration of both power running and regeneration.

FIG. 10is a graph illustrating a case where the first battery B1is charged in regeneration. An example ofFIG. 10is a case where the voltage V1of the first battery B1is higher than the voltage V2of the second battery B2and a case where the remaining capacity A1of the first battery B1is smaller than the remaining capacity A2of the second battery B2. In this case (V1>V2and A1<A2), in order to reduce the difference between the remaining capacity A1and the remaining capacity A2, the remaining capacity A2of the second battery B2is reduced more in power running or the remaining capacity A1of the first battery B1is increased more in regeneration. A loss becomes small in the example ofFIG. 10in a case where the remaining capacity A1of the first battery B1having relatively high voltage is adjusted. Since the remaining capacity of the first battery B1to be adjusted is smaller than that of the second battery B2, the distribution is performed in such a manner that the remaining capacity A1of the first battery B1is increased more in regeneration. Accordingly, in the electric energy adjustment, it is possible to reduce a loss in whole traveling in consideration of both power running and regeneration.

FIG. 11is a graph illustrating a case where the second battery B2is charged in regeneration. An example ofFIG. 11is a case where the voltage V2of the second battery B2is higher than the voltage V1of the first battery B1and a case where the remaining capacity A2of the second battery B2is smaller than the remaining capacity A1of the first battery B1. In this case (V1<V2and A1>A2), in order to reduce the difference between the remaining capacity A1and the remaining capacity A2, the remaining capacity A1of the first battery B1is reduced more in power running or the remaining capacity A2of the second battery B2is increased more in regeneration. A loss becomes small in the example ofFIG. 11in a case where the remaining capacity A2of the second battery B2having relatively high voltage is adjusted. Since the remaining capacity of the second battery B2to be adjusted is smaller than that of the first battery B1, the electric energy is adjusted by the distribution in such a manner that the remaining capacity A2of the second battery B2is increased more in regeneration. Accordingly, in electric energy adjustment, it is possible to reduce a loss in whole traveling in consideration of both power running and regeneration.

Further, as a modification example of the above-described embodiment, an ECU40may learn a history of a change in the remaining capacity A1of the first battery B1and a history of a change in the remaining capacity A2of the second battery B2and perform distribution control on which a tendency according to the histories is reflected. The ECU40includes a history learning unit to learn the history of remaining capacity. For example, in a case where a frequency of power running is high and a frequency of regeneration is low, it is considered that a history of utilization in a tendency, in which the remaining capacity A1of the first battery B1is likely to be decreased, is acquired. In contrast, in a case where the frequency of power running is low and the frequency of regeneration is high, it is considered that a history of utilization in a tendency, in which the remaining capacity A1of the first battery B1is likely to be increased, is acquired. Thus, the ECU40in the modification example can learn a changing tendency of the remaining capacity A1of the first battery B1and a changing tendency of the remaining capacity A2of the second battery B2, and can change the relationship between the distribution ratio β and the ratio of remaining capacity α according to a result of the learning. This modification example will be described with reference toFIG. 12andFIG. 13. Note that in a description of the modification example, the descriptions about elements similar to those in the above-described embodiment are omitted and the same reference signs are used.

FIG. 12is a graph illustrating a case where the history of remaining capacity is reflected on the relationship between the ratio of remaining capacity α and the distribution ratio β in power running. In a case where the history of remaining capacity is not reflected, the relationship between the ratio of remaining capacity α and the distribution ratio β is similar to the above-described relationship ofFIG. 3. The distribution ratio β becomes 0.5 when the ratio of remaining capacity α is 0.5. For example, in a case where the history indicating that there is a tendency that remaining capacity A1of the first battery B1becomes small is learned, the distribution ratio β is made higher on a side of the second battery B2in such a manner that a discharged amount from the first battery B1is decreased in power running. After this change, as indicated by a dotted line inFIG. 12, the distribution ratio β becomes a value smaller than 0.5 when the ratio of remaining capacity α is 0.5. Alternatively, in a case where the history indicating that there is a tendency that the remaining capacity A1of the first battery B1becomes greater is learned, the distribution ratio β is made higher on a side of the first battery B1in such a manner that the discharged amount from the first battery B1is increased in power running. After this change, as indicated by a thick solid line inFIG. 12, the distribution ratio β becomes a value greater than 0.5 when the ratio of remaining capacity α is 0.5. Note that although not illustrated, a relationship may be changed in such a manner that a distribution ratio β in regeneration is made higher on a side of the first battery B1in order to increase a charged amount to the first battery B1. Similarly, a relationship may be changed in such a manner that the distribution ratio β in regeneration is made higher on a side of the second battery B2in order to reduce a charged amount of the first battery B1.

FIG. 13is a flowchart illustrating a control flow of electric energy adjustment using the history of remaining capacity. The control ofFIG. 13is performed by the ECU40.

The ECU40determines whether the electric energy adjustment condition is satisfied (Step S11). Step S11is similar to Step S1inFIG. 6. In a case where negative determination is made in Step S11(NO in Step S11), the control routine ends.

In a case where positive determination is made in Step S11(YES in Step S11), with respect to a distribution ratio β changed according to the history of the remaining capacity, the ECU40calculates a distribution ratio β corresponding to a current ratio of remaining capacity (remaining capacity ratio) α (Step S12). In Step S12, the distribution ratio β indicated by the above-described dotted line or thick solid line inFIG. 12is calculated as the distribution ratio β for the ratio of remaining capacity α. Note that since Steps S13to S16inFIG. 13is similar to Steps S2to S5described above inFIG. 6except for a point that a distribution ratio β determined in Step S12is used, descriptions thereof are omitted.

As described above, according to the modification example, the distribution ratio β is changed by utilization of the history of a change in the remaining capacity A1of the first battery B1and the history of a change in the remaining capacity A2of the second battery B2. Thus, it is possible to reduce a loss in whole traveling while appropriately adjusting electric energy. That is, according to the modification example, even in a case where the frequency of power running or regeneration is high, the change into a distribution ratio β on which a changing tendency of the remaining capacity is reflected is made. Thus, it is possible to avoid a state in which the electric energy adjustment cannot be made in both of power running and regeneration. Thus, it becomes possible to appropriately manage the remaining capacity A1of the first battery B1and the remaining capacity A2of the second battery B2according to a driving tendency of a driver, a road grade, or a traffic condition.

Note that since what is desired as the vehicle Ve in which a motor generator30as a power source for traveling is mounted, such vehicle Ve is not limited to the above-described electric car and may be a hybrid vehicle in which an engine and a motor generator30are mounted. Further, a power system100may include a plurality of motor generators and a plurality of inverters. A circuit configuration of a power system100may be an electric circuit including a smoothing capacitor (not illustrated). Moreover, a circuit configuration of an electric power adjustment unit10is not limited to the above-described first boost converter11or the second boost converter12and what is desired is an electric circuit in which a plurality of switching elements is appropriately arranged in such a manner that the first battery B1and the second battery B2can perform an output independently. In addition, the first battery B1and the second battery B2may include secondary batteries having different maximum electric power that can be output or different maximum chargeable capacity.

According to an embodiment, in electric energy adjustment of a plurality of electric storage devices mounted in a vehicle, the distribution is performed either in power running or in regeneration whichever the loss is smaller. Thus, it is possible to reduce a loss in the entire traveling.

According to an embodiment, it is possible to reduce a loss in whole traveling since the loss in power running and the loss in regeneration are compared and the adjustment of the electric energy is performed during power running or regeneration whichever the loss is smaller.

According to an embodiment, it is possible to set a distribution ratio based on a ratio of remaining capacity and adjust electric energy by using the distribution ratio.

According to an embodiment, it is possible to change the distribution ratio so that a changing tendency of remaining capacity of each electric storage device is reflected in the changed distribution ratio. Accordingly, it becomes possible to appropriately manage the remaining capacities of the two electric storage devices in accordance with a driving tendency of a driver, a road grade, or a traffic condition.

According to an embodiment, it is possible to change the distribution ratio so that a changing tendency of remaining capacity of each electric storage device is reflected in the changed distribution ratio. Thus, it is possible to avoid a state in which the electric energy adjustment cannot be performed in both power running and regeneration even in a case where one of a frequency of power running or a frequency of regeneration is high.

According to an embodiment, a type of the first electric storage device may differ from the type of the second electric storage device. Therefore, the present disclosure can be applied to variety of vehicles.