Battery control apparatus for power supply system

Before power is supplied to a load from a capacitor and a plurality of batteries, a battery for initially supplying power for charging to the capacitor is determined from among the plurality of batteries, based on a result of acquiring the voltage of each battery, and voltage equalization of the plurality of batteries is performed in response to power for charging being supplied to the capacitor from the determined battery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-054969 filed on Mar. 29, 2021, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a battery control apparatus for a power supply system that includes a plurality of batteries capable of being connected in parallel. More specifically, the present invention relates to a battery control apparatus that performs voltage equalization for the plurality of batteries in the power supply system.

Description of the Related Art

A heavy-load drive motor, such as a traction motor of an electric automobile or a flight motor of an electric aircraft, is supplied with electric power from a high-power battery formed by connecting high-voltage batteries in parallel.

In a power supply system that supplies power to a load by connecting a plurality of batteries in parallel, an excessive inrush current flows to batteries with a low voltage from batteries with a high voltage when the parallel connection is established. In order to suppress this flow of such an excessive inrush current, the plurality of batteries are connected in parallel after voltage equalization is performed on these batteries, and power is then supplied to the load.

As an example, JP 2018-042342 A discloses a voltage equalization method for a power source apparatus of a vehicle drive system that includes batteries connected in parallel (battery stack) supplying power to a load made up of a motor generator and a drive circuit (including a smoothing capacitor and inverter) that drives the motor generator.

In the voltage equalization method disclosed in JP 2018-042342 A, in a case where there is a voltage difference between two batteries after operation of the power source apparatus has stopped (S12), as shown inFIGS.2and5thereof, for example, the parallel connection between the batteries is established through a precharge resistor. By causing the current to flow through the precharge resistor from the battery with high voltage to the battery with low voltage, the voltage difference between these batteries is reduced (paragraphs [0034] and [0035] of JP 2018-042342 A).

SUMMARY OF THE INVENTION

In the voltage equalization method disclosed in JP 2018-042342 A, after the operation of the power source apparatus has been stopped, the voltage equalization is performed for each of the batteries and then the power source apparatus is reactivated. When reactivating the power source apparatus, the batteries are connected in parallel after the smoothing capacitor has been charged, via the precharge resistor, by whichever battery is provided with this precharge resistor (paragraph [0015] of JP 2018-042342 A).

However, in the voltage equalization method disclosed in JP 2018-042342 A, there is a problem that, when the power source apparatus is activated, a voltage inequality (voltage difference) occurs between the battery that supplies power to the smoothing capacitor and the battery that does not supply power to the smoothing capacitor.

Furthermore, there is a problem that when there is a long idle time after the batteries have been used, a voltage difference occurs due to a difference in the self-discharge of the batteries or the like.

The present invention has been devised taking into consideration the aforementioned problems, and has the object of providing a battery control apparatus for a power supply system that makes it possible to efficiently eliminate voltage inequality among batteries connected in parallel, even when a capacitor is connected in parallel with the load to which power is being supplied.

Furthermore, the present invention has the objective of providing a battery control apparatus for a power supply system that makes it possible to efficiently eliminate voltage inequality among batteries connected in parallel, even when there is a long battery idle time.

A battery control apparatus for a power supply system according to one aspect of the present invention includes: a capacitor that is connected in parallel with a load and supplies power to the load; and a plurality of batteries that supply power to the capacitor to thereby charge the capacitor and supply power to the load, the batteries being connectable in parallel to each other, wherein: before power is supplied to the load from the capacitor and the plurality of batteries, one or more batteries for initially supplying power for charging to the capacitor are determined, from among the plurality of batteries, based on a result of acquiring a voltage of each battery; and voltage equalization among the plurality of batteries is performed in response to power for charging being supplied to the capacitor from the determined one or more batteries.

According to the present invention, before power is supplied to the load from the capacitor, a battery for initially supplying power for charging to the capacitor, among the plurality of batteries, is determined based on the result of acquiring a voltage of each battery, and voltage equalization among the plurality of batteries is performed in response to power for charging being supplied to the capacitor from the determined battery.

Therefore, even in a case where the capacitor is connected in parallel with the load to which power is to be supplied, it is possible to efficiently eliminate voltage inequality among the batteries connected in parallel. Furthermore, since the voltage equalization is performed before the power is supplied to the load, it is possible to reliably perform voltage equalization even when there is a long idle time after the batteries are used.

DESCRIPTION OF THE INVENTION

Preferred embodiments of a battery control apparatus for a power supply system according to the present invention will be presented and described below with reference to the accompanying drawings.

FIG.1is a block diagram showing a schematic configuration of an electric flying body10in which a power supply system16according to an embodiment is loaded.

The electric flying body10is basically formed from the power supply system16, a thrust generating section18that is supplied with electric power from the power supply system16to generate thrust, and a control section20that controls the overall electric flying body10including the power supply system16and the thrust generating section18.

The control section20is formed from a battery control apparatus30and a flying body control apparatus36, which transmit and receive signals to and from each other via a communication line such as a CAN. A power switch38of the electric flying body10is connected to the battery control apparatus30.

The battery control apparatus30and the flying body control apparatus36are each formed from a microcomputer including a CPU, a memory (ROM and RAM), a timer, and the like, and each function as various function sections (function means) by having the CPU execute a program stored in the memory.

The power supply system16is formed from a battery section26and a power generating section28.

The battery section26includes a plurality of batteries, which in this case is four batteries1to4, as an example. The four batteries1to4are respectively formed as battery modules21to24.

In the present embodiment, the specifications of the batteries1to4are that each battery is a high-voltage laminated lithium-ion secondary battery that generates the same voltage and has the same power capacity. However, the present invention can be applied to a case where there is variation among the power capacity specifications of the batteries1to4or a case where the batteries1to4are other types of secondary batteries. The laminated lithium-ion secondary battery is an assembled battery that generates a high voltage by connecting single cells in series.

The battery modules21to24are connected in parallel between a positive electrode bus81and a negative electrode bus82.

The battery module21is formed of the battery1that has a voltage sensor31connected thereto and whose negative electrode side is connected to the negative electrode bus82, a precharge resistor R1, a precharge contactor (also referred to simply as a contactor) Kin, and a main contactor (also referred to simply as a contactor) K1p.

In this case, the main contactor K1pis connected in parallel to the precharge resistor R1and precharge contactor Kin, which are connected in series. One end of the main contactor K1pis connected to the positive electrode bus81, and the other end of the main contactor K1pis connected to the positive terminal side of the battery1.

The other battery modules22to24are formed of the same configurational elements as the battery module21in the same connection state.

One end of a contactor K11and one end of a contactor K13are connected respectively to the ends of the positive electrode bus81, and one end of a contactor K12and one end of a contactor K14are connected respectively to the ends of the negative electrode bus82.

All of the contactors K1pto K4p, Kin to K4n, and K11to K14are electromagnetic contactors that have normally-open connection points, and are configured such that the connection points close (contactors close) when power is supplied to the respective coils (not shown in the drawings) from the battery control apparatus30.

The battery control apparatus30acquires battery voltages Vb (Vb=V1, V2, V3, V4) of the batteries1to4from the voltage sensors31to34. Furthermore, the battery control apparatus30acquires battery currents flowing through the batteries1to4using current sensors (not shown in the drawings). Yet further, the battery control apparatus30acquires battery temperatures of the batteries1to4using temperature sensors (not shown in the drawings), and manages the SOC (state of charge), which is the remaining capacity, of each battery1to4.

A capacitor C1, which is a smoothing capacitor serving as a load of the battery section26during startup (when the power switch38is ON), and an input side of an inverter61are connected to the other ends of the contactors K11and K12. The inter-terminal voltage (capacitor voltage) Vc of the capacitor C1, that is, the input end voltage of the inverter61, is measured by a voltage sensor35provided to an inverter control apparatus (not shown in the drawings) that controls driving of the inverter61. The measured capacitor voltage Vc is transmitted to the battery control apparatus30via a communication line such as a CAN (not shown in the drawings), and acquired by the battery control apparatus30.

Under the control of the inverter control apparatus (not shown in the drawings), at startup, the inverter61converts the DC (direct current) voltage (capacitor voltage) Vc generated at the ends of the charged capacitor C1into three-phase AC (alternating current), and causes a main shaft64of a motor generator62to rotate.

The main shaft64of the motor generator62causes the rotor and turbine of a compressor of a gas turbine66to rotate integrally. Then, fuel is supplied to a combustor of the gas turbine66and combusted by the gas turbine66, and the gas turbine66starts rotating due to the fuel.

At this time, the inverter control apparatus (not shown in the drawings) causes the motor generator62to operate as a power generator in which the main shaft64is rotated by the gas turbine66, and converts the AC power generated by the power generator into DC power, through the inverter61, to charge the batteries1to4forming the battery section26.

Under the control of the flying body control apparatus36, the charged DC power of the batteries1to4is converted into AC power through a capacitor C2and inverter72forming the thrust generating section18, via the contactors K13and K14, a main shaft76of a motor74is rotated by this AC power, and a propeller80for generating thrust, which is connected to the main shaft76, is rotated.

In the present embodiment, the electric flying body10is a vertical takeoff and landing aircraft, and includes eight propellers for vertical takeoff and landing and two propellers for horizontal flying. The electric flying body10is not limited to this configuration, and may be a vertical takeoff and landing aircraft that includes two or more propellers for vertical takeoff and landing and one or more propellers for horizontal flying, or some other type of electric flying body.

The following describes the operation, including the process of voltage equalization of the batteries1to4, performed by the battery control apparatus30of the power supply system16configured basically in the manner described above, while referencing the flow chart ofFIG.2. Unless otherwise specified, the component performing the processing shown in the flow chart is a CPU of the battery control apparatus30or a CPU of the flying body control apparatus36or another dedicated ECU (not shown in the drawings), but since it would be complicated to refer to this each time, it is only referred to as needed.

At step S1, monitoring is performed to check whether the power switch38of the electric flying body10has changed from the OFF state to the ON state. When it is judged that the power switch38has changed to the ON state (step S1: YES), at step S2, the battery voltages Vb (Vb=V1, V2, V3, V4) of the batteries1to4and the capacitor voltage Vc of the capacitor C1are acquired through the voltage sensors31to35.

It should be noted that, when the power switch38is in the OFF state, and at the timing when the power switch38switches from the OFF state to the ON state, all of the contactors K1pto K4p, Kin to K4n, and K11to K14are open (i.e., all the electric currents are cut off).

Next, at step S3, charging is performed so that inrush current does not flow into the capacitor C1, and the voltage equalization process is performed so that inrush current does not flow between the batteries1to4.

In practice, in a state where the inverters61and72have been controlled to be in a stopped state, the contactors K11to K14are closed and charging is performed with the capacitor C1and capacitor C2in a parallel state. But here, in order to avoid unnecessary complexity and to facilitate understanding, the process of performing precharging so that inrush current does not occur in the capacitor C1in a state where the contactors K11and K12are closed and the contactors K13and K14are open, and of equalizing the battery voltages, is described in the order of [1] to [4] below.

[1] Normal precharging and voltage equalization process {a case where each battery voltage Vb is a voltage indicating a target remaining capacity (target SOC)}.

In the present embodiment, the target SOC is set to a value that avoids the high remaining capacity side in which deterioration of the batteries1to4is small, for example. This target SOC is the target SOC during charging/discharging control of the batteries1to4by the battery control apparatus30when the gas turbine66performs combustion and the motor generator62operates as a power generator.

The SOC is correlated with the voltage, and therefore the battery voltage Vb corresponding to the target SOC is described as a threshold voltage Vth.

[2] (First Embodiment Example) The precharging and voltage equalization process is performed in a case where, among the batteries1to4, the SOC of one battery is the target SOC (including a state where the SOC is approximately the same as the target SOC, and this is also true in the following descriptions) and the SOCs of the remaining three batteries are lower than the target SOC.

[3] (Second Embodiment Example) The precharging and voltage equalization process is performed in a case where, among the batteries1to4, three batteries have the target SOC and the SOC of the remaining one battery is lower than the target SOC.

[4] (Third Embodiment Example) The precharging and voltage equalization process is performed in a case where the SOCs of all of the batteries1to4are lower than the target SOC, and there is variation among these SOCs.

[1] Description of Normal Precharging and Voltage Equalization Process (a Case where V1=V2=V3=V4=Vth)

The description is provided while referencing the operational schematic diagrams ofFIGS.3A to3D.

In the operational schematic diagrams ofFIGS.3A to3D, configurational elements corresponding to configurational elements shown inFIG.1are given the same reference numerals. The same is true for the operational schematic diagrams in the other descriptions below (FIGS.4A to4D,5A to5D, and6A to6D).

As shown inFIG.3A, in a case where the difference among the battery voltages Vb of the batteries1to4is within an inrush current prevention voltage difference (prescribed voltage range) ΔVp, the capacitor C1is charged from the batteries1to4via the respective precharge resistors R1to R4in a state where the contactors K1pto K4p(seeFIG.1) are open (contactors K11and K12are already in a closed state) and the contactors Kin to K4nare closed, such that an excessive inrush current does not occur, as shown inFIG.3B.

Here, a case in which the difference among the battery voltages Vb of the batteries1to4is within the inrush current prevention voltage difference ΔVp is referred to as a case in which the voltage difference |Vb−Vb*| between the battery voltage Vb of one battery and the battery voltage Vb of another battery (referred to as Vb*) has a relationship of |Vb−Vb*| ΔVp. In other words, this is a case where voltage equalization of the batteries1to4has been achieved (i.e., a case where the voltage equalization process is unnecessary).

The inrush current prevention voltage difference ΔVp for the batteries1to4is a voltage difference that does not cause an excessive inrush current to flow from a battery with high voltage among the batteries1to4to a battery with low voltage among the batteries1to4, even when the contactors K1pto K4pare closed and the batteries1to4are connected in parallel. Here, the contactors K1pto K4pare closed for the equalization process that makes the battery voltages V1to V4of the batteries1to4the same voltage. In other words, the inrush current prevention voltage difference ΔVp is a predetermined voltage range in which a tolerably small inrush current, which is limited by the battery voltage difference |Vb−Vb*| and the internal resistances of the batteries1to4, flows.

As shown inFIG.3C, when the charging progresses and the voltage difference Vbc (Vbc=Vb−Vc) between the voltage Vc of the capacitor C1and the battery voltage Vb (here, V1=V2=V3=V4) has become a value less than or equal to an inrush current prevention voltage difference ΔVr at which a current less than or equal to the tolerable inrush current is guaranteed {(Vb−Vc) ΔVr}, the contacts K1pto K4pare closed. The inrush current prevention voltage difference ΔVr, which makes it possible to limit the inrush current flowing from the batteries1to4to the capacitor C1to be less than or equal to a prescribed current when the batteries1to4and the capacitor C1have become directly connected, is determined in advance according to a combination of the batteries1to4and the capacitor C1.

It should be noted that the contactors Kin to K4nmay be opened before the contactors K1pto K4pare closed. The same is also true below. However, in the interest of preventing aging degradation of the contactors Kin to K4nthat is dependent on the number of opening/closing cycles of the connection points or the like, it is preferable for the contactors Kin to K4nto be closed.

In the connection state shown inFIG.3C, the charging of the capacitor C1continues. In this case, the contactors K1pto K4phaving closed connection points are connected in parallel respectively to the circuits in which the contactors Kin to K4nwith closed connection points and the precharge resistors R1to R4are connected in series. In this case, the contact resistance values of the contactors K1pto K4pare extremely low compared to the resistance values of the precharge resistors R1to R4, and therefore substantially all the currents flowing from the batteries1to4flow into the capacitor C1through the contactors K1pto K4p.

In this manner, the process of charging the capacitor C1through [1] the normal precharging and voltage equalization process performed for the capacitor C1(actually including C2as well) of step S3is finished.

After the charging control for the capacitor C1is finished, at step S4, the inverter61is driven in the state shown inFIG.3C, and the motor generator62is driven as a motor via the driven inverter61to rotate the main shaft64.

Due to the rotation of the main shaft64, at step S5, the gas turbine66is started up via the motor generator62, and the power generating section28starts generating power.

In other words, at step S6, as shown inFIG.3D, the motor generator62operates as a power generator and the charging control by the battery control apparatus30continues in a manner to cause the battery voltages V1to V4of the batteries1to4connected in parallel to become the threshold voltage Vth corresponding to the target SOC due to the power of the power generating section28.

At the same time, at step S7, the propeller80can rotate via the motor74by driving the motor74through the inverter72using the power of the capacitor C2and the batteries1to4connected in parallel. Due to this, the thrust generating section18becomes able to operate (enables vertical takeoff and landing, and horizontal flight or vertical flight after the vertical takeoff) under the control of the flying body control apparatus36.

Next, at step S8, the flight of the electric flying body10continues until the power switch38is set to the OFF state (step S8: NO→step S6: power generation continues→step S7: rotational driving of propeller80).

The electric flying body10lands at a prescribed location and, at step S8, when the power switch38is switched from the ON state to the OFF state (step S8: YES), at step S9, the contactors K11to K14, K1pto K4p, and Kin to K4nare all set to the OFF state and the process of the flow chart is finished.

When this process is finished, in order to avoid danger, the capacitors C1and C2are discharged through a discharge circuit (not shown in the drawings), so that the capacitor voltages Vc become less than or equal to a prescribed voltage.

2 First Embodiment Example

Description of Precharging and Voltage Equalization Process in Case where, Among Batteries1to4, SOC of One Battery is Target SOC and SOCs of the Remaining Three Batteries are Lower than Target SOC (a Process of Preventing Inrush Current from Flowing into the Capacitor C1and a Process of Voltage Equalization Among the Batteries1to4while Preventing Inrush Current, which are the Same in the Cases Below)

The description is given while referencing the operational schematic diagrams ofFIGS.4A to4D.

This process is performed in a case where, as shown inFIG.4A, the battery voltage V1of the battery1is approximately the threshold voltage Vth (V1≈Vth), but the battery voltages V2to V4of the remaining batteries2to4are lower than the threshold voltage Vth (V2to V4<Vth≈V1).

As shown inFIG.4B, in a state where the contactors K1pto K4pand K2nto K4nare open, only the contactor Kin of the battery1that has a high battery voltage Vb is closed. Due to this, the inrush current to the capacitor C1does not become excessive, and the capacitor C1is charged from only the battery1in the high-voltage state through the contactor Kin and the precharge resistor R1.

Next, when the voltage differences ΔVb (V1−V2, V1−V3, V1−V4) between the battery voltage V1of the battery1and the battery voltages V2to V4of the remaining batteries2to4have become the inrush current prevention voltage difference ΔVp, the corresponding contactors K2nto K4nare closed.

As an example, when the voltage difference ΔVb=(V1−V2) has dropped to the inrush current prevention voltage difference ΔVp, the contactor K2nis closed, thereby realizing voltage equalization between the battery1and the battery2and continuing the charging of the capacitor C1from the voltage-equalized batteries1and2through the respective precharge resistors R1and R2.

Under similar conditions below, at the same time that voltage equalization of the batteries1to4is performed by sequentially closing the contactors K3nand K4nof the remaining batteries3and4, excluding the batteries1and2that are supplying power to the capacitor C1, the charging of the capacitor C1continues from the voltage-equalized batteries1to4through the respective precharge resistors R1to R4.

In this way, as shown inFIG.4C, when the charging progresses and the differential voltage Vbc (Vbc=Vb−Vc) between the voltage Vc of the capacitor C1and the battery voltage Vb (Vb=V1to V4) has become a value less than or equal to the inrush current prevention voltage difference ΔVr at which a current less than or equal to the tolerable inrush current for the capacitor C1is guaranteed (Vbc=(Vb−Vc) ΔVr), the contactors K1pto K4pare closed.

Due to this, the currents flowing from the batteries1to4flow to the capacitor C1through the contactors K1pto K4p.

In this manner, the process of charging the capacitor C1(actually including C2as well) of step S3and the process of voltage equalization of the batteries1to4are finished.

In the process ofFIG.4BtoFIG.4Caccording to the first embodiment example described above, in a state where the capacitor C1is being precharged by only the battery1, when a voltage difference ΔVb between the battery voltage V1of the battery1that is in the midst of voltage-dropping and the battery voltages V2to V4of the batteries2to4before the voltage equalization process has dropped to the inrush current prevention voltage difference ΔVp, the contactors K2nto K4nare closed and the voltage equalization process is performed for the batteries2to4. After the voltage equalization process for the batteries2to4has been performed, the precharging of the capacitor C1by the batteries1to4continues through the contactors Kin to K4nand precharge resistors R1to R4. However, the present invention is not limited to this, and may be configured as shown in a first modification.

In this case, in a state (FIG.4B) where the capacitor C1is being precharged by only the battery1through the precharge resistor R1, when the battery voltage V1of the battery1whose inter-terminal voltage (battery voltage V1) is in the midst of dropping has dropped to the same voltage as the battery voltages V2to V4of the batteries2to4(ΔVb=0), that is, when the battery voltage equalization process has substantially been finished, the contactors K2nto K4nare closed. Then, the processing may be changed to continue precharging the capacitor C1with the batteries1to4through the contactors Kin to K4nand precharge resistors R1to R4.

In the first embodiment example and the first modification, if the SOCs of the batteries2to4are much smaller than the SOC of the battery1, the precharging of the capacitor C1is finished with only the battery1and the power generating section28is made to operate, after which processing may be performed to equalize the voltages of the remaining batteries2to4using the battery1.

In this case, when the potential differences between the battery voltages V2to V4and the battery voltage V1have become less than or equal to the inrush current prevention voltage difference ΔVp, the voltage equalization process is performed by sequentially shorting the precharge resistors R2to R4with the contactors K2pto K4p.

Next, a simple description of the processing from step S4described above will be provided.

At step S4, in the state shown inFIG.4C, the motor generator62is driven via the inverter61, and at step S5, the gas turbine66is started up via the motor generator62to start the power generation by the power generating section28.

After this, at step S6, as shown inFIG.4D, charging control is performed such that the battery voltages V1to V4of the batteries1to4become the threshold voltage Vth corresponding to the target SOC using the power of the power generating section28, and the motor generator62continues to operate as a power generator.

At step S7, the propeller80becomes able to rotate due to the power of the batteries1to4. Due to this, the thrust generating section18is able to perform the various flight operations described above under the control of the flying body control apparatus36.

3 Second Embodiment Example

Description of Precharging and Voltage Equalization Process in Case where, Among Batteries1to4, Three Batteries have Approximately Target SOC and SOC of the Remaining One Battery is Lower

The description is provided while referencing the operational schematic diagrams ofFIGS.5A to5D.

As shown inFIG.5A, a case is described in which the battery voltages V1to V3of the batteries1to3are approximately the same as the threshold voltage Vth, but the battery voltage V4of the remaining battery4is lower than the threshold voltage Vth (V4<Vth).

In this case, in a state where the contactors K1pto K4pare open, the contactors Kin to K4nare closed.

Due to this, as shown inFIG.5B, the voltage equalization process is performed on the batteries1to4by charging the battery4having a low voltage via the precharge resistors R1to R3and the precharge resistor R4up to the same voltage as the batteries1to3, and the capacitor C1is charged from the batteries1to4in a range where the inrush current is not excessive, through the respective precharge resistors R1to R4.

InFIG.5Baccording to the second embodiment example, the precharging of the capacitor C1and the charging of the battery4by the batteries1to3are performed at the same time, but the timing is not limited to this, and may be changed as shown in a second modification.

As an example, in the state shown inFIG.5A, the contactors Kin to K3nare closed while the contactor K4nis kept open, and precharging of the capacitor C1by the batteries1to3is prioritized. Then, when the potential differences ΔVb between the battery voltages V1to V3of the batteries1to3and the battery voltage V4of the battery4have become zero (when the battery voltages have become the same), or when these voltage differences ΔVb have dropped to the inrush current prevention voltage difference ΔVp, voltage equalization of the batteries1to4may be performed by closing the contactor K4n.

Which of the process of performing voltage equalization of the battery4prioritizing precharging of the capacitor C1in this way or the process of performing the voltage equalization of the battery4at the same time as the precharging of the capacitor C1from the start such as shown inFIG.5Bshould be adopted can be determined in advance in consideration of the SOCs of the batteries1to4and the electrostatic capacitance of the capacitor C1. Due to this, it is possible to select the process in which the precharging and voltage equalization are finished quickly.

In both the second embodiment example and the second modification, as shown inFIG.5C, when the charging progresses and the differential voltage Vbc (Vbc=Vb−Vc) between the voltage Vc of the capacitor C1and the battery voltage Vb (Vb=V1to V4) has become a value less than or equal to the inrush current prevention voltage difference ΔVr (Vbc=(Vb−Vc) ΔVr), the contactors K1pto K4pare closed. The inrush current prevention voltage difference ΔVr is a voltage difference at which flowing of a current less than or equal to the tolerable inrush current for the capacitor C1is guaranteed.

After this, the currents flowing from the batteries1to4flow to the capacitor C1through the contactors K1pto K4p.

At this point, the charging control for the capacitor C1(actually including C2as well) of step S3is finished.

Next, a simple description of the processing from step S4described above will be provided.

At step S4, in the state shown inFIG.5C, the motor generator62is driven via the inverter61, and at step S5, the gas turbine66is started up via the motor generator62to start the power generation by the power generating section28.

At step S6, as shown inFIG.5D, charging control is performed such that the battery voltages V1to V4of the batteries1to4become the threshold voltage Vth corresponding to the target SOC using the power of the power generating section28, and the motor generator62continues to operate as a power generator.

At step S7, the propeller80becomes able to rotate due to the power of the batteries1to4. Due to this, the thrust generating section18is able to perform the various flight operations described above under the control of the flying body control apparatus36.

4 Third Embodiment Example

Description of Precharging and Voltage Equalization Process in Case where SOCs of all of Batteries1to4are Lower than Target SOC (Threshold Voltage Vth) and there is Variation Among these SOCs

The description is provided while referencing the operational schematic diagrams ofFIGS.6A to6D.

A case will be described in which, as shown inFIG.6A, the battery voltages V1to V4of the batteries1to4are lower than the threshold voltage Vth and have variations resulting in a relationship of Vth>V1>V3>V4>V2.

In this case, first, as shown inFIG.6B, in a state where the contactors K1pto K4pare in the open state, the contactor Kin of the battery1having the highest battery voltage Vb (Vb=V1) and the contactor K3nof the battery3having the second highest battery voltage Vb (Vb=V3) are closed.

Due to this, the battery voltage V3of the battery3is charged up to the same voltage as the battery voltage V1of the battery1through the precharge resistors R1and R3, and voltage equalization is achieved for the battery voltages V1and V3of the batteries1and3(the battery voltage V1at this timing has become lower than the battery voltage V1shown inFIG.6A). Along with the voltage equalization of the battery voltages V1and V3of the batteries1and3, the capacitor C1is charged from the battery1in a range where the inrush current does not become excessive, through the precharge resistor R1. Then, after the voltage equalization has been achieved for the battery1and the battery3(V1=V3), the capacitor C1is charged from the batteries1and3through the respective precharge resistors R1and R3.

Although not shown in the drawings, in the state shown inFIG.6B, the contactor K4nof the battery4having the third highest battery voltage Vb is closed and charging is performed through the precharge resistors R1, R3, and R4until the battery voltage V4of the battery4becomes the same voltage as the battery voltage Vb of the batteries1and3(Vb=V1=V3), thereby achieving voltage equalization of the batteries1,3, and4. Along with the voltage equalization of the batteries1,3, and4, the capacitor C1is charged from the equalized batteries1,3, and4in a range where the inrush current does not become excessive, through the respective precharge resistors R1, R3, and R4.

In a similar manner, although not shown in the drawings, the contactor K2nof the battery2having the fourth highest battery voltage Vb is closed and charging is performed through the precharge resistors R1, R2, R3, and R4until the battery voltage V2of the battery2becomes the same voltage as the battery voltage Vb of the batteries1,3, and4(Vb=V1=V3=V4), thereby achieving voltage equalization of the batteries1to4. Along with the voltage equalization of the batteries1to4, the capacitor C1is charged from the equalized batteries1to4in a range where the inrush current does not become excessive, through the respective precharge resistors R1to R4.

InFIG.6B, the precharging of the capacitor C1and the charging of the battery3are performed at the same time, but the timing is not limited to this, and may be changed as shown in a third modification.

Initially focusing on the battery1that has the highest battery voltage V1, only the contactor Kin of this battery1is closed to precharge the capacitor C1. The battery voltage V1of the battery1decreases in accordance with the precharging of the capacitor C1. When the battery voltage V1decreases and the potential difference ΔVb between the battery voltage V1and the battery voltage V3of the battery3has become zero (when these voltages have become the same), the contactor K3nis closed. Alternatively, when the battery voltage V1decreases and the potential difference ΔVb between the battery voltage V1and the battery voltage V3has dropped to the inrush current prevention voltage difference ΔVp, that is, after voltage equalization has been achieved, the contactor K3nis closed. By closing the contactor K3n, the precharging of the capacitor C1is performed by the batteries1and3. The same is true for the other batteries2and4as well.

In both the third embodiment example and the third modification, as shown inFIG.6C, when the charging progresses and the differential voltage Vbc (Vbc=Vb−Vc) between the voltage Vc of the capacitor C1and the battery voltage Vb (Vb=V1to V4) has become a value less than or equal to the inrush current prevention voltage difference ΔVr at which flowing of a current less than or equal to the tolerable inrush current for the capacitor C1is guaranteed (Vbc ΔVr), the contactors K1pto K4pare closed.

After this, the currents flowing from the batteries1to4flow to the capacitor C1through the contactors K1pto K4p.

At this point, the charging process for the capacitor C1(actually including C2as well) of step S3is finished.

Furthermore, both the third embodiment example and the third modification can be applied to at least two batteries having a voltage level difference.

Next, a simple description of the processing from step S4described above will be provided.

At step S4, in the state shown inFIG.6C, the motor generator62is driven via the inverter61, and at step S5, the gas turbine66is started up via the motor generator62to start the power generation by the power generating section28.

At step S6, as shown inFIG.6D, charging control is performed such that the battery voltages V1to V4of the batteries1to4become the threshold voltage Vth corresponding to the target SOC using the power of the power generating section28, and the motor generator62continues to operate as a power generator.

At step S7, the propeller80becomes able to rotate due to the power of the batteries1to4. Due to this, the thrust generating section18is able to perform the various flight operations described above under the control of the flying body control apparatus36.

Invention Understandable from the Embodiments

The following describes the invention that can be understood from the embodiments described above. Some configurational elements are given the reference numerals used in the embodiments in order to facilitate understanding, but these configurational elements are not limited to those elements given the reference numerals.

According to the present invention, there is provided a battery control apparatus30for a power supply system16, the power supply system including: a capacitor C1that is connected in parallel with a load and supplies power to the load; and a plurality of batteries1to4that supply power to the capacitor C1to thereby charge the capacitor C1and supply power to the load, the batteries being connectable in parallel to each other. Before power is supplied to the load from the capacitor C1and the plurality of batteries1to4, the battery control apparatus determines one or more batteries, from among the plurality of batteries1to4, for initially supplying power for charging to the capacitor C1, based on a result of acquiring a voltage of each of the battery1to4. Further, the battery control apparatus performs voltage equalization among the plurality of batteries1to4, in response to power for charging being supplied to the capacitor C1from the determined one or more batteries.

With this configuration, before power is supplied to the load from the capacitor C1, a battery for initially supplying power for charging to the capacitor C1, from among the plurality of batteries1to4, is determined based on the result of acquiring a voltage of each of the battery1to4; and voltage equalization among the plurality of batteries is performed in response to power for charging being supplied to the capacitor C1from the determined battery.

Therefore, even in a case where the capacitor C1is connected in parallel with the load to which power is to be supplied, it is possible to efficiently eliminate voltage inequality among the batteries1to4connected in parallel. Furthermore, since the voltage equalization is performed before the power is supplied to the load, it is possible to reliably perform voltage equalization even when there is a long idle time after the batteries are used.

In the battery control apparatus30for the power supply system: the one or more batteries for initially supplying power for charging to the capacitor C1may be one battery that has the highest voltage among the plurality of batteries, and the remaining batteries may be set to an open state. Further, power for charging may be supplied to the capacitor from the one battery, through a precharge resistor; while power for charging is being supplied to the capacitor from the one battery, power for charging may be supplied to the capacitor also from a remaining battery whose voltage difference relative to the one battery whose voltage has decreased has become zero, through a precharge resistor; and the plurality of batteries and the capacitor may be connected in parallel by shorting the precharge resistors when voltage differences between the voltage of the capacitor and the voltages of the plurality of batteries become less than or equal to a prescribed voltage difference (corresponding to the first modification).

According to the above, the precharging of the capacitor C1is started before the battery voltage equalization process is started, and therefore it is possible to shorten the capacitor precharging time.

In the battery control apparatus30for the power supply system: the one or more batteries1to4for initially supplying power for charging to the capacitor C1may be one battery that has the highest voltage among the plurality of batteries1to4, and the remaining batteries may be set to an open state; power for charging may be supplied to the capacitor C1from the one battery, through a precharge resistor; while power for charging is being supplied to the capacitor C1from the one battery, the one battery whose voltage has dropped and a remaining battery whose voltage difference relative to the one battery whose voltage has dropped has become less than or equal to a prescribed voltage difference may be connected via precharge resistors, to thereby perform voltage equalization between the one battery and the remaining battery, and thereafter the supply of power for charging to the capacitor C1may be continued from the one battery and the remaining battery that have undergone the voltage equalization, through the respective precharge resistors; and similarly, voltage equalization may be performed among other remaining batteries and the batteries that have undergone voltage equalization, the capacitor C1may be charged from all of the voltage-equalized batteries via the respective precharge resistors, and the capacitor C1may be connected in parallel to the plurality of batteries by shorting the precharge resistors when the voltage differences between the voltage of the capacitor C1and the voltages of the batteries become less than or equal to a prescribed voltage difference (corresponding to the first embodiment example).

According to the above, the precharging of the capacitor C1is started before the battery voltage equalization process is started for the batteries1to4, and therefore it is possible to shorten the precharging time for the capacitor C1.

In the battery control apparatus30for the power supply system: the one or more batteries for initially supplying power for charging to the capacitor may be a group of batteries whose voltages are higher than the voltage of a remaining battery, among the plurality of batteries, and power for charging may be supplied to the capacitor from the group of batteries whose voltages are higher than the voltage of the remaining battery, through respective precharge resistors; while power for charging is being supplied to the capacitor from the group of batteries, supply of power for charging to the capacitor may be continued, in addition to the group of batteries, also from the remaining battery whose voltage difference relative to the group of batteries whose voltages have dropped has become zero, through a precharge resistor; and the capacitor may be connected in parallel with the plurality of batteries by shorting the precharge resistors when the voltage differences between the voltage of the capacitor and the voltages of the plurality of batteries have become a prescribed voltage difference (corresponding to the second modification).

According to the above, it is possible to shorten the capacitor precharge time and the battery voltage equalization time.

In the battery control apparatus30for the power supply system: the one or more batteries for initially supplying power for charging to the capacitor C1may be a group of batteries whose voltages are higher than the voltage of a remaining battery, among the plurality of batteries, power for charging may be supplied to the capacitor C1from the group of batteries whose voltages are higher than the voltage of the remaining battery, through respective precharge resistors, and voltage equalization of the batteries may be performed by supplying power for charging to the remaining battery whose voltage is lower than the voltages of the group of batteries, through the respective precharge resistors (corresponding to the second embodiment example).

According to the above, it is possible to shorten the capacitor C1precharge time and the battery voltage equalization time.

In the battery control apparatus30for the power supply system: there may be at least two batteries that have a voltage level difference; when power for charging is to be supplied to the capacitor, first, power for charging may be supplied to the capacitor from one battery, of the at least two batteries, that has the higher voltage, through a precharge resistor; while power for charging is being supplied to the capacitor from the one battery that has the higher voltage, when a voltage difference between the voltage of the one battery that has the higher voltage whose voltage has dropped and the voltage of the other battery that has the lower voltage has become zero, power for charging may be supplied to the capacitor from the at least two batteries through respective precharge resistors; and when the voltage differences between the voltage of the capacitor and the voltages of the at least two batteries have become less than or equal to a prescribed voltage difference, the capacitor may be connected in parallel to the at least two batteries by shorting the respective precharge resistors (corresponding to the third modification).

According to the above, even when there is a level difference among the battery voltages of the batteries, it is possible to efficiently perform the battery voltage equalization and the precharging of the capacitor.

In the battery control apparatus30for the power supply system: when power for charging is to be supplied to the capacitor C1, first, battery voltage equalization may be performed on a battery having the second highest voltage from a battery having the highest voltage, through a precharge resistor, and power for charging may be supplied to the capacitor C1from the battery having the highest voltage and the battery having the second highest voltage, through precharge resistors; next, battery voltage equalization may be performed on a battery having the third highest voltage from the battery having the highest voltage and the battery having the second highest voltage, through the precharge resistors, and power for charging may be supplied to the capacitor C1from the battery having the highest voltage, the battery having the second highest voltage, and the battery having the third highest voltage, through the precharge resistors; and subsequently the battery voltage equalization may be continuously performed on other batteries similarly to the above (corresponding to the third embodiment example).

According to the above, even when there is a level difference among the battery voltages V1to V4of the batteries1to4, it is possible to efficiently perform the battery voltage equalization and the precharging of the capacitor C1.

In the battery control apparatus30for the power supply system, the load may be a rotary electric machine that is driven through an inverter.

According to the above, various applications can be realized using the power of the rotary electric machine.

The present invention is not limited to the electric flying body10described in the embodiments above, and it is obvious that various configurations can be adopted based on the content described in this specification of the present application, such as applying the present invention to electric automobiles including hybrid vehicles and fuel cell vehicles or to electric moving bodies, such as an electric boat, that use batteries as a power source and a motor as a movement drive source.

Furthermore, in the electric moving body including the electric flying body10, the gas turbine66of the power generating section28may be replaced by an internal combustion engine such as a reciprocating engine.