Storage battery system

Abstract

To improve energy efficiency of a storage battery system.SOLUTION: A storage battery system includes a first storage battery, a second storage battery, a power generation unit, a first switch, a battery charger, a second switch, and a control circuit. The power generation unit operates using an output of the first storage battery or the second storage battery as a power source and outputs AC power. The first switch switches a storage battery used as a power source of the power generation unit to the first storage battery or the second storage battery. The battery charger operates using an output of the power generation unit as a power source and charges the first storage battery and the second storage battery. The second switch connects an output of the battery charger to the first storage battery or the second storage battery. The control circuit controls the first switch and the second switch.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a battery system. [Background technology]

[0002] In order to extend the time during which power can be supplied to a load, a storage battery system equipped with multiple storage batteries is known. In many cases, such a storage battery system is configured to monitor the remaining capacity of a main storage battery, and switch to a spare storage battery when the remaining capacity of the main storage battery falls below a predetermined value.

[0003] For example, while the system is operating on the main battery, the spare battery is charged or replaced. Then, while the system is operating on the spare battery, the main battery is charged or replaced. In this way, by switching between the main battery and the spare battery, the power supply to the load is stabilized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-11447 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the output of a storage battery is direct current. Therefore, when supplying power to electrical equipment that is driven by an alternating current commercial power source, it is necessary to generate alternating current power using an inverter or generator.

[0006] A battery storage system using a generator composed of a motor operates to output a constant amount of power. However, the power supplied to the load is not constant, and surplus power may be generated. This surplus power is lost as thermal energy. Focusing on this lost energy, there seems to be room for improvement in the energy efficiency of battery storage systems.

[0007] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to improve the energy efficiency of a storage battery system. [Means for solving the problem]

[0008] In order to solve the above problems, a storage battery system according to an embodiment includes a first storage battery, a second storage battery, a power generation unit, a first switch, a battery charger, a second switch, and a control circuit. The power generation unit operates using the output of the first storage battery or the second storage battery as a power source, and outputs AC power. The first switch switches the storage battery used as the power source of the power generation unit to either the first storage battery or the second storage battery. The battery charger operates using the output of the power generation unit as a power source, and charges the first storage battery and the second storage battery. The second switch connects the output of the battery charger to the first storage battery or the second storage battery. The control circuit controls the first switch and the second switch. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a storage battery system according to a first embodiment. [Diagram 2] 3 is a block diagram of an excess power feedback unit according to the first embodiment. FIG. [Diagram 3] 5 is a diagram for explaining the operation of a surplus power feedback section according to the first embodiment. FIG. [Figure 4] 5 is a flowchart for explaining a switching control process of the storage battery system according to the first embodiment. [Diagram 5] FIG. 4 is a diagram for explaining a switching control process of the storage battery system according to the first embodiment. [Figure 6] 5 is a flowchart for explaining a charging control process of the storage battery system according to the first embodiment. [Figure 7] 10 is a graph showing the relationship between the remaining capacity of a battery and the output voltage of the battery according to the second embodiment. [Figure 8] FIG. 11 is a diagram for explaining a charging control process of a storage battery system according to a third embodiment. [Figure 9] FIG. 11 is a block diagram of a storage battery system according to a fourth embodiment. [Figure 10] FIG. 11 is a block diagram of a storage battery system according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a storage battery system according to an embodiment will be described with reference to the drawings.

[0011] (Embodiment 1) 1 is a block diagram of a storage battery system according to embodiment 1. The storage battery system 1 includes a first battery 11 (first storage battery), a second battery 12 (second storage battery), a first switch 21, a second switch 22, a power generation unit 30, a battery charger 40, a surplus power feedback unit 50, and a control circuit 70.

[0012] The first battery 11 and the second battery 12 are each formed of, for example, a lithium ion battery. The output voltage of the first battery 11 and the second battery 12 is, for example, a DC voltage of 24V.

[0013] The first switch 21 is a circuit for switching the battery used as the power source for the power generation unit 30. The first switch 21 selects the first battery 11 or the second battery 12 as the power source for the power generation unit 30 based on control by the control circuit 70. The second switch 22 is a circuit for selecting the battery to be charged by the battery charger 40. The second switch 22 connects the output of the battery charger 40 to the first battery 11 or the second battery 12 based on control by the control circuit 70. The first switch 21 and the second switch 22 can be configured with a FET (Field Effect Transistor), a relay, or the like.

[0014] The power generating unit 30 operates using the output of the first battery 11 or the second battery 12 as a power source, and outputs desired AC power. The power generating unit 30 includes an inverter 31, a drive motor 32, and a generator 33.

[0015] The inverter 31 receives a DC voltage of 24 V from the first battery 11 or the second battery 12, and outputs a voltage suitable for the drive motor 32. The inverter 31 outputs a three-phase AC voltage of, for example, 100 V. The inverter 31 is configured to be able to switch the frequency of the three-phase AC voltage so that the frequency of the AC voltage output by the generator 33 becomes 50 Hz or 60 Hz.

[0016] The drive motor 32 rotates using the output of the inverter 31 as a power source, and rotates a motor that constitutes a generator 33.

[0017] The rotating shaft of the motor constituting the generator 33 is connected to the rotating shaft of the drive motor 32 by, for example, gears or the like. The generator 33 rotates based on the rotation of the drive motor 32 and outputs a three-phase AC voltage of about 200V. In detail, taking into consideration the voltage loss in the subsequent circuit, the generator 33 outputs a three-phase AC voltage of about 220V. The frequency of the three-phase AC voltage output by the generator 33 is 50Hz or 60Hz. The frequency of the AC voltage output by the generator 33 is determined by the number of poles of the generator and the rotation speed of the motor. The generator 33 rotates at a rotation speed at which the frequency of the AC voltage output by the generator 33 is 50Hz or 60Hz based on the rotation of the drive motor 32. A three-phase AC voltage of 220V is output to a terminal P1 shown in FIG. 1.

[0018] The battery charger 40 operates using the output of the power generation unit 30 as a power source, and charges the first battery 11 and the second battery 12 with a charging voltage and charging current suitable for the first battery 11 and the second battery 12. For example, the battery charger 40 charges the first battery 11 and the second battery 12 with a constant charging current. The allowable input voltage of the battery charger 40 is 100V to 220V. A 100V commercial power source is connected to terminal P2 in FIG. 1. The battery charger 40 can also operate by switching the power source from the output of the power generation unit 30 to the commercial power source based on the control of the control circuit 70.

[0019] The surplus power feedback unit 50 adjusts the power supplied to the battery charger 40 in accordance with the power supplied from the power generation unit 30 to the load circuit 100. The load circuit 100 is, for example, an electrical device that operates on an AC voltage of 200 V. As shown in Fig. 2, the surplus power feedback unit 50 has a current monitor 51 and a limiting circuit 52. The current monitor 51 measures the value of the current supplied to the load circuit 100.

[0020] The limiting circuit 52 is a circuit for adjusting the power supplied to the battery charger 40. The current monitor 51 measures the value of the current supplied to the load circuit 100 and notifies the control circuit 70. The control circuit 70 controls the limiting circuit 52 to adjust the power supplied to the battery charger 40 in accordance with the power supplied to the load circuit 100.

[0021] 3 is a diagram for explaining the operation of the limiting circuit 52. The limiting circuit 52 supplies the power output by the power generation unit 30 to the battery charger 40 during a period Ton. The limiting circuit 52 does not supply the power output by the power generation unit 30 to the battery charger 40 during a period Toff. The control circuit 70 controls the ratio Ton / (Ton+Toff) of the limiting circuit 52 according to the power supplied to the load circuit 100. If the power output by the power generation unit 30 is 100% and the power supplied to the load circuit 100 is x% of that, the control circuit 70 controls the limiting circuit 52 of the surplus power feedback unit 50 so that (Equation 1) is established. Ton / (Ton+Toff)=f(100-x) (Equation 1) Ton: The time that power has been supplied to the battery charger 40 Toff: The time when the battery charger 40 is not powered

[0022] The function f may be a function determined in stages according to the value of (100-x). For example, the value of (100-x) may be divided into 5% intervals, and a table in which the value of Ton / (Ton+Toff) is set for each interval may be used as the function f. The function f may also be a function such as (Equation 2). f(100-x)=α(100-x) (Equation 2) α: coefficient

[0023] For example, if (100-x)=20%, the control circuit 70 controls the limiting circuit 52 so that the limiting circuit 52 is on for 20% of the time and off for 80% of the time. The limiting circuit 52 can be constructed using a FET, a relay, or the like.

[0024] Returning to FIG. 1, the control circuit 70 controls the first switch 21 and the second switch 22. The control circuit 70 also controls the limiting circuit 52 as described above. The control circuit 70 also performs control to select either the output of the power generation unit 30 or a commercial power source as the input source for the battery charger 40. The control circuit 70 is composed of a CPU, RAM, ROM, etc. The control circuit 70 controls the first switch 21, the second switch 22, the limiting circuit 52, and the battery charger 40 based on software stored in the ROM.

[0025] Next, the switching control process of the first switch 21 and the second switch 22 by the control circuit 70 will be described with reference to the flowchart shown in Fig. 4. Here, the description will start from a state in which the first switch 21 selects the first battery 11 and the second switch 22 selects the second battery 12.

[0026] The control circuit 70 measures the input / output currents of the first battery 11 and the second battery 12 (step S11). As shown in Fig. 5, a first current monitor 111 that measures the charging current with which the first battery 11 is charged is provided on the input side of the first battery 11. A second current monitor 112 that measures the current output from the first battery 11 is provided on the output side of the first battery 11. The control circuit 70 calculates the remaining capacity of the first battery 11 based on the measurement values ​​of the first current monitor 111 and the second current monitor 112 (step S12).

[0027] Furthermore, a third current monitor 121 that measures the charging current with which the second battery 12 is charged is provided on the input side of the second battery 12. A fourth current monitor 122 that measures the current output from the second battery 12 is provided on the output side of the second battery 12. The control circuit 70 calculates the remaining capacity of the second battery 12 based on the measurement values ​​of the third current monitor 121 and the fourth current monitor 122 (step S12).

[0028] Next, the control circuit 70 judges whether the remaining capacity of the battery selected by the first switch 21 is equal to or greater than the threshold (step S13). Here, the first switch 21 selects the first battery 11, so the control circuit 70 judges whether the remaining capacity of the first battery 11 is equal to or greater than the threshold. For example, the threshold is a value such as 40% or 20% when a battery is fully charged at 100%. If the remaining capacity of the first battery 11 is equal to or greater than the threshold (step S13: Yes), the control circuit 70 maintains the connection state of the first switch 21 and the second switch 22.

[0029] On the other hand, if the remaining capacity of the battery is less than the threshold (step S13: No), the control circuit 70 performs switching control of the first switch 21 and the second switch 22 (step S14). Specifically, since the first switch 21 is in a state in which the first battery 11 and the power generation unit 30 are connected (since the first switch 21 is in a state in which the first battery 11 is selected), the control circuit 70 controls the first switch 21 so that the second battery 12 is connected to the power generation unit 30. Also, since the second switch 22 is in a state in which the battery charger 40 and the second battery 12 are connected (since the second switch 22 is in a state in which the second battery 12 is selected), the control circuit 70 controls the second switch 22 so that the battery charger 40 and the first battery 11 are connected.

[0030] When the first switch 21 selects the second battery 12 and the second switch 22 selects the first battery 11, the control circuit 70 performs control in the above explanation by replacing the first battery 11 with the second battery 12.

[0031] Next, the charging control process from the battery charger 40 to the battery by the control circuit 70 will be described with reference to the flowchart shown in Fig. 6. Here, the description will start from a state in which the battery charger 40 is operating based on the output of the power generation unit 30, the first switch 21 selects the first battery 11, and the second switch 22 selects the second battery 12.

[0032] The control circuit 70 determines whether the remaining capacity of both the first battery 11 and the second battery 12 is less than a threshold value (step S31).

[0033] If the remaining capacity of both the first battery 11 and the second battery 12 is less than the threshold (step S31: Yes), the control circuit 70 performs control to switch the input of the battery charger 40 to commercial power (step S32). A state in which the remaining capacity of both the first battery 11 and the second battery 12 is less than the threshold means that the storage battery system 1 is short of energy. Therefore, the storage battery system 1 needs to replenish energy from the outside. After completing the process of step S32, the control circuit 70 transitions to step S35.

[0034] On the other hand, if the remaining capacity of either the first battery 11 or the second battery 12 is greater than or equal to the threshold (step S31: No), the input source of the battery charger 40 remains the power output by the power generation unit 30 supplied via the surplus power feedback unit 50.

[0035] The current supplied to the load circuit 100 is measured by the current monitor 51 (step S33), and the measured value is notified to the control circuit 70. The control circuit 70 controls the limiting circuit 52 of the surplus power feedback unit 50 based on the above-mentioned (Equation 1) to adjust the power supplied to the battery charger 40 (step S34).

[0036] Next, the control circuit 70 judges whether the remaining capacity of the battery not selected by the first switch 21 (here, the second battery 12) is less than a threshold value (step S35). If the remaining capacity of the battery is equal to or greater than the threshold value (step S35: No), the control circuit 70 controls the second switch 22 or the battery charger 40 to stop charging the second battery 12 (step S36). This threshold value is set so that the remaining capacity of the battery becomes a predetermined remaining capacity (e.g., 80% or 90%) with respect to the fully charged state. This control makes it possible to prevent overcharging of the battery and reduce accidents caused by battery damage.

[0037] As a condition for resuming charging, the threshold may have hysteresis. For example, if the threshold for stopping charging is a remaining capacity equivalent to 80% of the full charge state, the threshold for resuming charging may be set to a remaining capacity equivalent to 75% of the full charge state.

[0038] On the other hand, if the remaining capacity of the battery is less than the threshold (step S35: Yes), the control circuit 70 charges the battery not selected by the first switch 21 (step S37). At this time, the control circuit 70 controls the limiting circuit 52 of the surplus power feedback unit 50 based on (Equation 1). The control circuit 70 continues the processes from step S31 to step S37.

[0039] In the storage battery system 1 having the configuration shown in FIG. 1, the power generation unit 30 always generates a predetermined amount of power. On the other hand, the power consumed by the load circuit 100 always changes from moment to moment depending on the usage situation of the user. However, since the drive motor 32 and the generator 33 constituting the power generation unit 30 have inertia, it is difficult to control the rotation speed according to the moment-to-moment load fluctuation. For example, even if there is no power consumed by the load circuit 100, the drive motor 32 and the generator 33 constituting the power generation unit 30 do not stop rotating, and the power generation unit 30 continues to generate power. However, since there is no power supplied to the load circuit 100, the power generated by the power generation unit 30 becomes surplus power. In the absence of the surplus power feedback unit 50 and the battery charger 40, the surplus power would be lost as thermal energy in the power generation unit 30.

[0040] The storage battery system 1 according to the first embodiment charges the first battery 11 and the second battery 12 with surplus power output by the power generation unit 30 via the surplus power feedback unit 50 and the battery charger 40. This allows the storage battery system 1 to reduce the surplus power lost as thermal energy in the power generation unit 30, thereby improving energy efficiency.

[0041] In the above description, the storage battery system 1 supplies 200V AC to the load circuit 100. However, the storage battery system 1 may supply 100V AC to the load circuit 100. In this case, the generator 33 outputs 100V AC. The storage battery system 1 may also supply 100V AC and 200V AC to the load circuit 100. In this case, a generator that outputs 100V AC and a generator that outputs 200V AC are provided.

[0042] In the above description, the inverter 31 outputs an AC voltage of 100V. However, the inverter 31 may output an AC voltage of 200V, and the drive motor 32 may be driven by the AC voltage of 200V.

[0043] Also, in the above description, the case has been described where the power supplied to the battery charger 40 is adjusted by ON / OFF control of the surplus power feedback unit 50. However, the method of adjusting the power supplied to the battery charger 40 does not need to be limited to this. For example, the current supplied to the battery charger 40 may be limited in accordance with the current supplied to the load circuit 100.

[0044] In the above description of step S31, the control circuit 70 determines whether the remaining capacity of both the first battery 11 and the second battery 12 is less than the threshold. However, in the processing of step S31, the control circuit 70 may compare the total value of the remaining capacity of both the first battery 11 and the second battery 12 with a predetermined threshold.

[0045] Also, in the above explanation, it is assumed that the battery not in use is charged to a predetermined amount before switching is performed between the first switch 21 and the second switch 22. If this assumption is not true, the first switch 21 may select the battery with the larger remaining capacity.

[0046] In the above description, the output frequency of the inverter 31 is switched so that the frequency of the AC voltage output by the generator 33 becomes 50 Hz or 60 Hz. However, the method of adjusting the frequency of the AC voltage output by the generator 33 is not limited to this. For example, the frequency can be switched by changing the gear ratio of the gears connecting the drive motor 32 and the generator 33.

[0047] (Embodiment 2) In the first embodiment, a technique for calculating the remaining capacity of a battery based on the input / output power to the battery has been described. In the second embodiment, another technique for estimating the remaining capacity of a battery will be described.

[0048] Figure 7 is a graph showing the relationship between the remaining capacity of a battery and the output voltage of the battery. When the battery is fully charged, the output voltage of the battery tends to be high. The output voltage of the battery gradually decreases according to the remaining capacity. When the remaining capacity of the battery runs out, the output voltage tends to drop drastically. By focusing on this battery voltage characteristic, the remaining capacity of the battery can be estimated.

[0049] The configuration of the storage battery system 1 according to the second embodiment is the configuration shown in FIG. 1, but the configuration for measuring the remaining capacity of the battery shown in FIG. 5 is different from that of the first embodiment. The storage battery system 1 according to the second embodiment includes a first voltage monitor that monitors the output voltage of the first battery 11 and a second voltage monitor that monitors the output voltage of the second battery 12. The control circuit 70 estimates the remaining capacity of the first battery 11 based on the output voltage of the first battery 11, and estimates the remaining capacity of the second battery 12 based on the output voltage of the second battery 12. When the output voltage of the battery becomes a predetermined threshold voltage 2 shown in FIG. 7, the control circuit 70 performs switching control of the first switch 21 and the second switch 22. The threshold voltage 2 is set to a voltage value when the remaining capacity of the battery is a predetermined remaining capacity (for example, 40% or 20%).

[0050] Furthermore, in the process of step S35 shown in Fig. 6, the control circuit 70 determines whether the output voltage of the battery is equal to or higher than the threshold voltage 1 shown in Fig. 7. The threshold voltage 1 is set to a voltage value when the remaining capacity of the battery is a predetermined remaining capacity (e.g., 80% or 90%) with respect to the fully charged state.

[0051] In the configuration of the first embodiment, four current monitors were required to monitor the battery state. In addition, the control circuit 70 had to constantly calculate the remaining battery capacity, which placed a heavy processing load on the control circuit 70. In the configuration of the second embodiment, two voltage monitors are sufficient to monitor the battery state. If the switching process between the first switch 21 and the second switch 22 is triggered by the remaining battery capacity falling below a threshold, the processing load on the control circuit 70 can be reduced.

[0052] (Embodiment 3) In the first embodiment, a case has been described in which the control circuit 70 measures the current supplied from the power generation unit 30 to the load circuit 100, and controls the surplus power feedback unit 50 to adjust the power supplied to the battery charger 40 in accordance with the measured power. In the third embodiment, an example will be described in which the power supplied to the battery charger 40 is adjusted without measuring the current supplied from the power generation unit 30 to the load circuit 100.

[0053] 8 is a graph showing the relationship between the current supplied to the load circuit 100 and the output voltage (effective voltage or peak voltage) of the power generation unit 30. The output voltage of the power generation unit 30 tends to decrease as the output current increases. Also, when the power generation unit 30 approaches a no-load state, the output voltage of the power generation unit 30 tends to increase. This voltage characteristic is due to the fact that the torque of the generator 33 tends to decrease as the load increases, and that the voltage drop increases as the current flow increases.

[0054] Focusing on the relationship between the output current to the load circuit 100 and the output voltage of the power generation unit 30, it can be determined that surplus power is being generated when the output voltage of the power generation unit 30 is equal to or higher than the threshold voltage shown in Fig. 8. When the output voltage of the power generation unit 30 is equal to or higher than the threshold voltage shown in Fig. 8, the control circuit 70 controls the surplus power feedback unit 50 to feed back a part or all of the power output by the power generation unit 30 to the battery charger 40, thereby achieving the same effect as in the first embodiment.

[0055] The storage battery system 1 according to the third embodiment is provided with a voltage monitor that monitors the output voltage of the power generation unit 30, instead of the current monitor 51 of the first embodiment. When the output voltage of the power generation unit 30 exceeds the threshold voltage shown in Fig. 8, the control circuit 70 controls the limiting circuit 52 to supply the power output by the power generation unit 30 to the battery charger 40. The control circuit 70 does not need to perform control based on (Equation 1).

[0056] When the total power supplied to the load circuit 100 and the battery charger 40 increases, the output voltage of the battery decreases, as shown in Fig. 8. When the output voltage of the battery falls below the threshold voltage, the control circuit 70 controls the limiting circuit 52 to stop the power supply from the power generation unit 30 to the battery charger 40.

[0057] In the invention according to the third embodiment, the presence or absence of surplus power in the power generation unit 30 is estimated based on the output voltage of the power generation unit 30. When the control circuit 70 determines that the power generation unit 30 has surplus power, it controls the device itself to charge the battery not selected by the first switch 21 with the surplus power. This can improve the energy efficiency of the storage battery system 1.

[0058] The control circuit 70 may adjust the power supplied from the power generation unit 30 to the battery charger 40 in accordance with the output voltage of the power generation unit 30. For example, the limiting circuit 52 of the surplus power feedback unit 50 may be controlled based on (Equation 3) as shown in FIG. Ton / (Ton+Toff)=f(v) (Equation 3) Ton: The time that power has been supplied to the battery charger 40 Toff: The time when the battery charger 40 is not powered v: output voltage of the power generating unit 30

[0059] If the battery charger 40 is configured not to operate at a predetermined input voltage (for example, the threshold voltage shown in FIG. 8) or lower, the surplus power feedback unit 50 may be omitted.

[0060] Moreover, in the description of the third embodiment, a case has been described in which the surplus power feedback unit 50 feeds back the power output by the power generation unit 30 to the battery charger 40 when the output voltage of the power generation unit 30 is equal to or higher than a predetermined voltage. As another embodiment, an embodiment in which the surplus power feedback unit 50 feeds back the power output by the power generation unit 30 to the battery charger 40 when the output frequency of the power generation unit 30 is equal to or higher than a predetermined frequency is also possible.

[0061] (Embodiment 4) In the first to third embodiments, a case has been described in which the output of the generator 33 shown in Fig. 1 is used as the output of the storage battery system 1. In the fourth embodiment, a case will be described in which the output of the inverter 31 shown in Fig. 1 is used as the output of the storage battery system 1. Fig. 9 is a block diagram of a storage battery system according to the fourth embodiment. Descriptions that are the same as those in the first embodiment will be omitted.

[0062] The inverter 31 outputs, for example, three-phase AC power of 100 V or 200 V. The inverter 31 supplies the three-phase AC power to the load circuit 100, and also supplies power to the battery charger 40 via the drive motor 32 and the generator 33.

[0063] The inverter 31 always generates a predetermined amount of power. Meanwhile, the power consumed by the load circuit 100 constantly changes depending on the user's usage. For example, even when there is no power consumed by the load circuit 100, the inverter 31 continues to generate power. However, since there is no power supplied to the load circuit 100, the power generated by the inverter 31 becomes surplus power. The inverter 31 performs control to keep the output voltage constant, for example, by consuming the surplus power as thermal energy in a dummy load in the circuit.

[0064] The storage battery system 1 according to the fourth embodiment charges the first battery 11 and the second battery 12 with surplus power output by the inverter 31 via the drive motor 32, the generator 33, and the battery charger 40. Therefore, the energy lost as thermal energy in the inverter 31 is reduced. This allows the storage battery system 1 to improve energy efficiency.

[0065] When outputting 100V AC power and 200V AC power, the inverter 31 may be configured with an inverter outputting 100V and an inverter outputting 200V. Also, the inverter 31 may output 100V AC power, and the generator 33 may output 200V AC power.

[0066] Also, a surplus power feedback unit 50 may be provided at the output of the inverter 31, and the power supplied to the drive motor 32 may be adjusted according to the power supplied to the load circuit 100. Also, a voltage monitor may be provided to monitor the output voltage of the inverter 31, and when the output voltage of the inverter 31 becomes equal to or higher than a predetermined threshold voltage, the first battery 11 and the second battery 12 may be charged with the surplus power output by the inverter 31 via the drive motor 32, the generator 33, and the battery charger 40.

[0067] In the explanation of the first to fourth embodiments, the storage battery system 1 has the surplus power feedback unit 50 having the limiting circuit 52. However, there are other means for implementing the function of the surplus power feedback unit 50. For example, the control circuit 70 may control the battery charger 40 or the second switch 22 to be turned on / off, instead of controlling the limiting circuit 52 to be turned on / off.

[0068] (Embodiment 5) In the first to fourth embodiments, the case where the storage battery system 1 outputs AC power has been described. In the fifth embodiment, the case where the storage battery system 1 outputs DC power will be described. FIG. 10 is a block diagram of a storage battery system according to the fifth embodiment. The storage battery system 1 according to the fifth embodiment has a rectifier unit 60 that converts the AC power output by the power generation unit 30 into DC power. The rectifier unit 60 outputs DC power of, for example, DC 24V or DC 48V from terminal P3.

[0069] The rectification unit 60 is configured with an AC / DC converter or a smoothing circuit including a capacitor and a diode.

[0070] The storage battery system 1 according to the fifth embodiment may output AC power from the terminal P1 in addition to DC power.

[0071] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the invention and its equivalents described in the claims. [Explanation of symbols]

[0072] 1. Battery storage system 11…1st battery 12…2nd battery 21…First switch 22...Second switch 30…Power generation section 31…Inverter 32...Drive motor 33…Generator 40…Battery charger 50…Excess power return section 51...Current monitor 52...Limiting circuit 60... Rectifier 70...Control circuit 100...Load circuit 111…First current monitor 112…Second current monitor 121…Third current monitor 122…4th current monitor

Claims

1. A first storage battery; A second storage battery; a power generation unit that operates using an output from the first storage battery or the second storage battery as a power source and outputs AC power; a first switch that switches a storage battery used as a power source for the power generation unit between the first storage battery and the second storage battery; a battery charger that operates using an output of the power generation unit as a power source and charges the first storage battery and the second storage battery; a second switch for connecting an output of the battery charger to the first storage battery or the second storage battery; A control circuit for controlling the first switch and the second switch; A battery storage system having the above configuration.

2. a surplus power feedback unit that adjusts the power supplied from the power generation unit to the battery charger in response to the power supplied from the power generation unit to a load circuit; The battery system according to claim 1 .

3. a surplus power feedback unit that feeds back the power output from the power generation unit to the battery charger when the output voltage of the power generation unit is equal to or higher than a predetermined voltage; The battery system according to claim 1 .

4. the power generation unit is an inverter that uses an output of the first storage battery or the second storage battery as a power source and outputs AC power; a drive motor that rotates using the output of the inverter as a power source; a generator that rotates based on the rotation of the drive motor and outputs AC power; The battery system according to claim 1 .

5. When a remaining capacity of the first storage battery or the second storage battery selected by the first switch becomes equal to or less than a predetermined threshold, the control circuit controls the first switch to select the first storage battery or the second storage battery that has not been selected by the first switch before switching. The battery system according to claim 1 .

6. a first current monitor for monitoring a charging current to the first storage battery; a second current monitor that measures a current output from the first storage battery; a third current monitor that monitors a charging current to the second storage battery; a fourth current monitor that measures a current output from the second storage battery; Equipped with the control circuit estimates a remaining capacity of the first storage battery based on the charging current to the first storage battery and a current output from the first storage battery, and estimates a remaining capacity of the second storage battery based on the charging current to the second storage battery and a current output from the second storage battery. A storage battery system according to any one of claims 1 to 5.

7. a first voltage monitor that monitors an output voltage of the first storage battery; a second voltage monitor that monitors an output voltage of the second storage battery; Equipped with The control circuit estimates a remaining capacity of the first storage battery based on an output voltage of the first storage battery, and estimates a remaining capacity of the second storage battery based on an output voltage of the second storage battery. A storage battery system according to any one of claims 1 to 5.

8. The control circuit controls the second switch so as to connect an output of the battery charger to the first storage battery or the second storage battery that is not selected by the first switch. The battery system according to claim 1 .

9. The battery charger operates using a commercial power source as a power source and charges the first storage battery and the second storage battery. The battery system according to claim 1 .

10. When the remaining capacity of the first storage battery and the second storage battery is equal to or less than a predetermined threshold, the control circuit controls the battery charger to charge the first storage battery or the second storage battery using a commercial power source as a power source. The battery system according to claim 9.

11. A rectification unit converts the AC power output by the power generation unit into DC power. A storage battery system according to any one of claims 1 to 5.

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