Power supply device and power supply control method

Abstract

Provided is a power supply device and a power supply control method that can prevent momentary power interruptions and suppress fluctuations in output voltage, thereby enabling a stable power supply to be continued even when the connection of a plurality of secondary batteries to a load is switched. [Solution] A power supply device comprising a plurality of batteries (12a-12d) for charging and discharging, and a charge / discharge control unit (11) that selects a discharge target from the plurality of batteries (12a-12d) and connects it to a load, and selects a charge target and connects it to a power source, wherein the charge / discharge control unit (11) excludes the charge targets from the plurality of batteries (12a-12d) and selects one from a group of discharge targets included in a first potential range as the discharge target, and if there is no battery among the plurality of batteries (12a-12d) that is included in the first potential range, resets the first potential range, and switches the discharge target between a first battery and a second battery included in the group of discharge targets.

Description

[Technical field]

[0001] The present invention relates to a power supply device and a power supply control method, and more particularly to a power supply device and a power supply control method for supplying power by switching between a plurality of secondary batteries. [Background technology]

[0002] In recent years, electric vehicles that operate motors using power from charged secondary batteries have rapidly become popular. On the other hand, secondary batteries have a problem in that the charging and discharging performance deteriorates, and the driving range of the electric vehicle shortens depending on the number of charging and discharging cycles. Even if a deteriorated secondary battery cannot perform sufficiently for use in an electric vehicle, it may still have sufficient charging and discharging capabilities for other purposes. Therefore, the inventors of the present application have proposed using secondary batteries used in electric vehicles as power sources for other purposes (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-175980 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional power supply devices, when the remaining charge of a secondary battery connected to a load decreases or when the secondary battery is removed, the secondary battery is disconnected and then another secondary battery is selected and connected to the load. Therefore, when switching the connection of the secondary battery in conventional power supply devices, a momentary interruption occurs in which power is not supplied for an instant, making it difficult to continue supplying power to the load. In particular, in power supply devices that convert direct current supplied from a secondary battery into alternating current using a DC-AC inverter, the voltage fluctuation of the output alternating current becomes large, which may cause malfunctions of precision instruments and information devices. In particular, secondary batteries used in electric vehicles have a lower impedance than secondary batteries used in mobile phone devices and portable power supply devices so that they can supply a large current, and therefore there is a problem that the voltage fluctuation occurring when switching the secondary battery becomes large.

[0005] Therefore, the present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide a power supply device and a power supply control method that are capable of continuing to supply stable power by preventing momentary power interruptions and suppressing fluctuations in output voltage even when switching the connection of multiple secondary batteries to a load. [Means for solving the problem]

[0006] In order to solve the above problems, the power supply device of the present invention comprises a plurality of batteries to be charged and discharged, and a charge / discharge control unit that selects a discharge target from the plurality of batteries and connects it to a load, and selects a charge target and connects it to a power source, and is characterized in that the charge / discharge control unit excludes the charge target from the plurality of batteries and selects one from a group of discharge targets included in a first potential range as the discharge target, and if there is no battery among the plurality of batteries that is included in the first potential range, resets the first potential range and switches the discharge target between a first battery and a second battery included in the group of discharge targets.

[0007] In such a power supply device of the present invention, the battery to be discharged is selected from the batteries included in the first potential range, so that the potential difference between the first and second batteries when switching the battery to be discharged is limited, and the current flowing from the battery on the higher potential side to the battery on the lower potential side can be suppressed.Even when switching the connection of multiple secondary batteries connected to the load, it is possible to prevent momentary interruptions and suppress fluctuations in output voltage, thereby continuing to supply stable power.

[0008] In addition, in one embodiment of the present invention, the charge / discharge control unit excludes the discharge target from the multiple batteries and selects one from a group of charging targets included in a second potential range as the charging target, and if there is no battery among the multiple batteries that is included in the first potential range, resets the first potential range.

[0009] In addition, in one aspect of the present invention, the allowable current value is Imax, the impedance from the discharge target to the load is Rimp, and the first potential range is a range in which the upper and lower allowable potential difference Vper satisfies the relationship Vper≦Imax×Rimp.

[0010] In one embodiment of the present invention, the permissible potential difference Vper is 3 V or less.

[0011] In addition, in one aspect of the present invention, when the discharge target is switched from the first battery to the second battery, an overlap period is provided in which the first battery and the second battery are simultaneously connected to the load.

[0012] In one embodiment of the present invention, the overlap period is in the range of 100 msec or less.

[0013] In one aspect of the present invention, the discharge target is connected to the load via a DC-AC inverter, and the overlap period is within a range of five periods or less of an output waveform from the DC-AC inverter.

[0014] In one aspect of the present invention, a peak fluctuation of the output waveform during the overlap period is 5% or less.

[0015] In addition, in one aspect of the present invention, during the overlap period, the potential supplied to the DC-AC inverter is an intermediate potential between the potential of the first battery and the potential of the second battery.

[0016] In order to solve the above problems, the power supply control method of the present invention is a power supply control method that selects a discharge target from a plurality of batteries that are charged and discharged and connects it to a load, and selects a charge target and connects it to a power source, and is characterized in that the charge target is excluded from the plurality of batteries, and one is selected from a group of discharge targets included in a first potential range as the discharge target, and if there is no battery among the plurality of batteries that is included in the first potential range, the first potential range is reset, and the discharge target is switched between a first battery and a second battery included in the group of discharge targets. Effect of the Invention

[0017] The present invention provides a power supply device and a power supply control method that can continue to supply stable power by preventing momentary power interruptions and suppressing fluctuations in output voltage even when switching the connection of multiple secondary batteries to a load. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing an example of the configuration of a power supply device 10 according to a first embodiment of the present invention. [Diagram 2] 2 is a circuit diagram illustrating an example of output control from batteries 12a to 12d by a charge / discharge control unit 11. FIG. [Diagram 3] 3(a) shows the signal of switch SW1, FIG. 3(b) shows the signal of switch SW2, FIG. 3(c) shows the voltage at the input position of DC-AC inverter 13, and FIG. 3(d) shows the voltage at the output position of DC-AC inverter 13. [Figure 4] 4 is a flowchart illustrating a power supply control method according to the first embodiment. [Diagram 5] 11 is a graph illustrating a case where the output from the batteries 12a to 12d to the load 14 continues. [Figure 6] 13 is a graph illustrating a case where charging of batteries 12a to 12d from solar panel 16 or power supply unit 17 continues. [Figure 7] 13 is a graph illustrating a case where charging from solar panel 16 or power supply unit 17 is started in the middle of output from batteries 12a to 12d to load 14. FIG. [Figure 8] 13 is a graph illustrating a case where the battery 12d is not included in the group of batteries to be discharged and outputs continue from the batteries 12a to 12c. [Figure 9] 13 is a graph illustrating a case where the battery 12d is not included in the group of batteries to be charged, and charging of the batteries 12a to 12c from the solar panel 16 or the power supply unit 17 continues. [Figure 10] 13 is a graph illustrating a case in which the battery 12d is not included in the group of batteries to be discharged, and the batteries 12a to 12c continue to output power and discharge progresses to a completely discharged state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. FIG. 1 is a block diagram showing an example of the configuration of a power supply device 10 according to this embodiment. As shown in FIG. 1, the power supply device 10 includes a charge / discharge control unit 11, batteries 12a to 12d, a DC-AC inverter 13, a load 14, an AC-DC converter 15, a solar panel 16, and a power supply unit 17.

[0020] The charge / discharge control unit 11 is a part that selects a discharge target from the batteries 12a to 12d and connects it to the load 14, and also selects a charge target from the batteries 12a to 12d and connects it to the solar panel 16 and the power supply unit 17, which are power sources. The method of selecting a discharge target and a charge target by the charge / discharge control unit 11 will be described in detail later. The specific configuration of the charge / discharge control unit 11 is not limited, but it includes a memory, an external storage device, a central processing unit (CPU), an information communication device, etc. (not shown), and performs information processing according to a predetermined program to switch between connection and disconnection of the discharge target and the charge target. More specifically, the charge / discharge control unit 11 monitors the state of each part of the power supply device 10, and controls the opening and closing operation of a switch (described later) connected to the batteries 12a to 12d based on the state of each part and the predetermined program, thereby controlling the connection between the load 14, the AC-DC converter 15, the power supply unit 17, and the batteries 12a to 12d.

[0021] The batteries 12a to 12d are secondary batteries that can charge and discharge power. Like known secondary batteries, the batteries 12a to 12d each include terminals used for charging and discharging, a BMS (Battery Management System) that controls the charging and discharging, and the like.

[0022] The specific configuration of the batteries 12a to 12d is not limited, and known lithium ion batteries, nickel metal hydride batteries, all-solid-state batteries, etc. may be used. Battery cells contained in secondary batteries used in electric vehicles, hybrid vehicles, etc. may be reused and used as the batteries 12a to 12d. The batteries 12a to 12d may have an internal impedance of 10 mΩ or less.

[0023] The DC-AC inverter 13 is provided between the batteries 12a-12d and the load 14, and converts the direct current output from the batteries 12a-12d into alternating current and outputs it to the load 14. The specific circuit configuration of the DC-AC inverter 13 is not limited, and a known configuration can be used, but it is preferable to output a sine wave in order to expand the range of targets that can be operated as the load 14. The voltage and frequency of the alternating current output from the DC-AC inverter 13 are not limited, but it is preferable that they are in the voltage range of 100V to 220V and the frequency range of 50 to 60Hz, which are used as commercial power sources in various countries.

[0024] The load 14 is an electronic device connected to the output of the DC-AC inverter 13 and driven by the AC current output from the DC-AC inverter 13. The specific configuration of the load 14 is not limited, but examples include a computer device, a network device, a wireless communication relay device, and the like. In addition, the power supply device 10 may be placed in a structure such as a bench installed in a public place, and the output of the DC-AC inverter 13 may be used as an external power supply device, so that the electronic device connected to the external power supply device becomes the load 14. In the power supply device 10 of the present embodiment, no momentary interruption occurs even when switching between multiple secondary batteries, and fluctuations in the output voltage can be suppressed, so that the loads 14 that require a stable power supply can be connected and used continuously.

[0025] AC-DC converter 15 is a part whose input side is connected to power supply unit 17 to convert AC to DC, and is connected to charge / discharge control unit 11 to supply power to batteries 12a-12d. Although the specific configuration of AC-DC converter 15 is not limited, as an example, it converts, for example, 100V AC supplied from a commercial power source into 30V DC.

[0026] The solar panel 16 is a component in which solar cell elements that generate electromotive force when irradiated with light such as sunlight are packaged, and is a part that supplies power to the batteries 12a to 12d according to the control of the charge / discharge control unit 11. The material of the solar cell elements that constitute the solar panel 16 is not particularly limited, and a plurality of solar cell elements connected in series or parallel can be used as necessary. The solar panel 16 supplies power to the batteries 12a to 12d to charge them according to the control of the charge / discharge control unit 11, and therefore corresponds to the power source in the present invention.

[0027] The power supply unit 17 is a part that supplies an alternating current to the AC-DC converter 15. The specific configuration of the power supply unit 17 is not limited, and a commercial power source, an AC power generation device, or the like can be used. The power supply unit 17 supplies power to the batteries 12a to 12d according to the control of the charge / discharge control unit 11 to charge the batteries, and corresponds to the power source in the present invention.

[0028] Fig. 2 is a circuit diagram for explaining an example of output control from the batteries 12a to 12d by the charge / discharge control unit 11. In the example shown in Fig. 2, one end of the switches SW1 to SW4 is connected in series to the output terminals of the batteries 12a to 12d, respectively. The switches SW1 to SW4 are also connected in parallel with each other, and the other end is connected to the input terminal of the DC-AC inverter 13. A load 14 is connected to the output terminal of the DC-AC inverter 13. Although the charge / discharge control unit 11 and the switches SW1 to SW4 are shown separately in Fig. 2, the charge / discharge control unit 11 may include the switches SW1 to SW4 and terminals and wiring connecting each unit.

[0029] The specific configuration of the switches SW1 to SW4 is not limited, and known semiconductor switches or mechanical switches can be used. As described later, the opening and closing operations of the switches SW1 to SW4 are performed on the order of milliseconds, so it is preferable to use semiconductor switches such as field effect transistors (FETs) capable of high-speed switching operations.

[0030] The charge / discharge control unit 11 monitors the state and voltage of each part of the power supply device 10, and controls the opening and closing operations of the switches SW1 to SW4 based on the state of each part and a predetermined program. The charge / discharge control unit 11 selects a discharge target from the batteries 12a to 12d, closes the switches SW1 to SW4 corresponding to the discharge target, and opens the others. As a result, only the discharge target among the batteries 12a to 12d is connected to the DC-AC inverter 13 and power is supplied to the load 14. The selection of the discharge target and the switching timing of each switch SW1 to SW4 will be described in detail later.

[0031] As shown in Fig. 2, the output voltages of the batteries 12a-12d are VBA1-VBA4, the voltage on the input side (parallel connection part) of the DC-AC inverter 13 is DCAC_IN, and the voltage on the output side of the DC-AC inverter 13 is DCAC_OUT. Although Fig. 1 and Fig. 2 show an example using four batteries 12a-12d and four switches SW1-SW4, the number is not limited, and three or five or more batteries may be connected in parallel.

[0032] Next, the control by the charge / discharge control unit 11 in switching the discharge target among the batteries 12a to 12d will be described with reference to FIG. 3. In FIG. 3, the case where the discharge target is switched from the battery 12a to the battery 12b will be described as an example, but similar switching control is performed for other combinations. FIG. 3 is a timing chart showing the switching of the connection in the power supply device 10, where FIG. 3(a) shows the signal of the switch SW1, FIG. 3(b) shows the signal of the switch SW2, FIG. 3(c) shows the voltage at the input position of the DC-AC inverter 13, and FIG. 3(d) shows the voltage at the output position of the DC-AC inverter 13. In the figure, the horizontal axis indicates time t, and the vertical axis indicates voltage. Also, up to time t1 indicates the first connection period, from time t1 to t2 indicates the overlap period, and after time t2 indicates the second connection period.

[0033] 3(a)(b), in the first connection period, the switch SW1 is closed (on) and the switch SW2 is open (off). Therefore, a direct current is supplied from the battery 12a to the switch SW1 and the parallel connection unit, and is converted to AC_OUT by the DC-AC inverter 13 and supplied to the load 14. When an instruction to switch the discharge target is issued in the power supply device 10, the discharge from the battery 12a is stopped, and an overlap period is entered in which the discharge is switched to the discharge from the battery 12b. The length of the overlap period is preferably 100 ms or less, and more preferably in the range of 10 ms to 100 ms.

[0034] Here, examples of cases where the discharge target from the battery 12a is switched include a case where the remaining charge of the battery 12a is reduced and the battery 12a is excluded from the selection of discharge targets, and a case where the battery 12a is switched to a charge target. Another example is a case where the battery 12a is removed and a lock mechanism (not shown) is released. Another example is a case where the user inputs an instruction to exclude the battery 12a from the discharge targets. Another example is a case where the temperature of the battery 12a rises and a protection instruction to stop discharge is sent by a control unit provided in the power supply device 10.

[0035] 3(a)(b), the switch SW1 is closed (ON) and the switch SW2 is closed (ON). During this overlap period, the battery 12a and the battery 12b are simultaneously connected to the load 14. Therefore, a direct current is supplied from the battery 12a or the battery 12b, which has a higher voltage, to the parallel connection part, and is converted to AC_OUT by the DC-AC inverter 13 and supplied to the load 14. After the overlap period set to a predetermined length has elapsed, a transition to the second connection period occurs.

[0036] 3(a) and (b), the switch SW1 is in an open state (OFF) and the switch SW2 is in a closed state (ON). Therefore, a direct current is supplied from the battery 12b to the switch SW2 and the parallel connection unit, and is converted to AC_OUT by the DC-AC inverter 13 and supplied to the load 14. After that, the load 14 continues to operate by the power supplied from the battery 12b.

[0037] As described above, in the power supply device 10 of the present embodiment, when the charge / discharge control unit 11 changes the switch SW1 from a closed state to an open state and the switch SW2 from an open state to a closed state, there is an overlap period during which the switches SW1 and SW2 are simultaneously in the closed state. Therefore, throughout the first connection period, the overlap period, and the second connection period, the battery 12a or the battery 12b is connected to the parallel connection unit, and no momentary interruption occurs during switching.

[0038] During the overlap period, the battery 12a, 12b with the higher voltage discharges, and a current flows in the direction of charging the battery with the lower voltage. If a large current flows in the direction of charging the battery with the lower voltage during this overlap period, the protection circuit of the BMS is activated, making subsequent charging and discharging operations impossible. Therefore, the length of the overlap period must be set to a short period so that an excessive current does not flow in the direction of charging the battery with the lower voltage of the batteries 12a, 12b. The length of the overlap period will be described in detail later.

[0039] As shown in FIG. 3(c), the voltage at the input position (parallel connection part) of the DC-AC inverter 13 is approximately equal to the output voltage VBA1 at the output part of the battery 12a during the first connection period, and is approximately equal to the output voltage VBA2 at the output part of the battery 12b during the second connection period. During the overlap period, the voltage at the input position (parallel connection part) of the DC-AC inverter 13 is an intermediate potential between VBA1 and VBA2. FIG. 3(c) shows an example in which the intermediate potential is close to the average value of VBA1 and VBA2, but it does not have to be the average value as long as it is between VBA1 and VBA2. FIG. 3(c) also shows an example in which the intermediate potential is constant throughout the overlap period, but the potential may change between VBA1 and VBA2.

[0040] As shown in Fig. 3(d), the voltage AC_OUT at the output position of the DC-AC inverter 13 is output as a sine wave AC. In Fig. 3(d), the waveform of AC_OUT after time t1 is marked with a circle, and each number indicates the order of a half cycle of the output waveform because the peak and bottom make up one cycle. In the first connection period, the peak voltage of AC_OUT is stable, but the overlap period begins at time t1, and the peak voltage fluctuates after DCAC_IN changes from VBA1 to the intermediate potential. Also, when the overlap period ends and the second connection period begins at time t2, the peak voltage fluctuates after DCAC_IN changes from the intermediate potential to VBA2.

[0041] The fluctuation in the peak voltage of AC_OUT becomes large at t1 when the overlap period begins and at t2 when the second connection period begins, and attenuates as the sine wave cycle progresses. This is because even if the input voltage to DC-AC inverter 13 changes, it is converted to the target output voltage by the performance and time constant of DC-AC inverter 13. However, if the fluctuation in the peak voltage of voltage AC_OUT is large and it takes a long time for it to attenuate and stabilize, there is a possibility that load 14 will not operate normally.

[0042] Therefore, in the power supply device 10 of this embodiment, the overlap period is preferably in the range of 100 ms or less, more preferably in the range of 10 ms to 100 ms. Alternatively, the overlap period is preferably in the range of 5 periods or less of the output waveform from the DC-AC inverter 13, more preferably in the range of 0.5 periods to 5 periods, and even more preferably in the range of 0.5 periods to 2 periods. Furthermore, it is preferable that the peak fluctuation of the output waveform from the DC-AC inverter 13 during the overlap period is 5% or less.

[0043] The control by the charge / discharge control unit 11 when switching the battery to be charged among the batteries 12a to 12d is omitted from the illustration. One end of a charging switch (not shown) is connected to each of the batteries 12a to 12d, and the other end of each charging switch is connected to the output side of the AC-DC converter 15 or the solar panel 16. The charge / discharge control unit 11 selects the battery to be charged from the batteries 12a to 12d, closes the charging switch corresponding to the battery to be discharged, and opens the others. As a result, only the battery to be charged among the batteries 12a to 12d is connected to the AC-DC converter 15 or the solar panel 16, and power for charging is supplied. When switching the battery to be charged, it is not necessary to provide an overlap period as when switching the battery to be discharged.

[0044] Fig. 4 is a flowchart for explaining the power supply control method according to this embodiment. In the power supply control method according to this embodiment, each step is repeatedly (loop) executed as shown in Fig. 4, and the selected charging target group, discharging target group, charging target and discharging target are recorded in a memory or a storage device and are continuously used in the next loop.

[0045] First, in a voltage measurement step of step S1, the charge / discharge control unit 11 measures the output voltages VBA1 to VBA4 of the batteries 12a to 12d. After the acquisition of the output voltages VBA1 to VBA4 is completed, the process proceeds to step S2.

[0046] Next, in the charging target group selection process of step S2, the charge / discharge control unit 11 selects candidates for charging targets as a charging target group based on the output voltages VBA1 to VBA4 of the batteries 12a to 12d. Here, as a method for selecting the charging target group, a method of selecting the output voltages VBA1 to VBA4 so that the most of them are included in a predetermined potential range may be mentioned. Alternatively, the predetermined potential range may be set based on the output voltage VBA1 to VBA4 with the largest voltage. Furthermore, if the charging target group has already been determined among the batteries 12a to 12d, the charging target group is reselected to continue as the charging target group. Furthermore, if the charging target group has already been determined but all of the batteries 12a to 12d included in the charging target group are outside the predetermined potential range, the predetermined potential range is reset and the charging target group is reselected. When the selection of the charging target group is completed, the process proceeds to step S3.

[0047] Next, in the discharge target group selection process of step S3, the charge / discharge control unit 11 selects candidates for discharge targets as a discharge target group based on the output voltages VBA1-VBA4 of the batteries 12a-12d. Here, as a method for selecting the discharge target group, a method of selecting the batteries so that the output voltages VBA1-VBA4 are most often included in a predetermined potential range can be mentioned. If the discharge target group has already been determined among the batteries 12a-12d, the batteries are reselected as the discharge target group. If the discharge target group has already been determined but all of the batteries 12a-12d included in the discharge target group are outside the predetermined potential range, the predetermined potential range is reset and the discharge target group is reselected. When the selection of the discharge target group is completed, the process proceeds to step S4.

[0048] Here, the predetermined potential range for selecting the group of batteries to be charged and the group of batteries to be discharged is a range in which the permissible potential difference Vper satisfies the relationship Vper≦Imax×Rimp, where Imax is the permissible current value permitted as an output for protecting against short circuits inside the power supply device 10, and Rimp is the impedance from the discharge target to the load 14. In other words, the difference between the upper limit and the lower limit of the predetermined potential range is equal to or smaller than the permissible potential difference Vper, and the batteries 12a-12d whose output voltages fall within this range are selected as the group of batteries to be charged or the group of batteries to be discharged.

[0049] As a specific example, if the allowable current value Imax is 88 A, the internal impedance of each of the batteries 12a-12d is 2 mΩ, and the impedance Rimp of the power supply device 10 is 33.3 mΩ, then Vper = 88 × 0.033 = 2.9 V. In this case, the predetermined potential range for selecting the group of charging targets and the group of discharging targets must be 2.9 V or less, and as an example, 2.0 V can be set as the predetermined potential range.

[0050] Next, in step S4, a charging object determination step, it is determined whether the output voltage of one of the batteries 12a to 12d already selected as a charging object is outside a predetermined potential range. If a charging object has not been selected or if the selected charging object is outside the predetermined potential range, the process proceeds to step S5, and if the selected charging object is within the predetermined potential range, the process proceeds to step S6.

[0051] In the charging object reselection process of step S5, one battery is selected from among the batteries 12a to 12d included in the group of batteries to be charged. In the selection of the charging object, batteries to be discharged are excluded from the selection. Any of the batteries 12a to 12d included in the group of batteries to be charged may be selected as the charging object, but it is preferable to select the battery with the lowest potential among the batteries included in the group of batteries to be charged. When the selection of the charging object is completed, the process proceeds to step S6.

[0052] Next, in step S6, a discharge target determination step, it is determined whether the output voltage of one of the batteries 12a-12d already selected as a discharge target is outside a predetermined potential range. If a discharge target has not been selected or if the selected discharge target is outside the predetermined potential range, the process proceeds to step S7, and if the selected discharge target is within the predetermined potential range, the process proceeds to step S8.

[0053] In the discharge target reselection process of step S7, one discharge target is selected from among the batteries 12a-12d included in the group of discharge targets. Here, in the selection of the discharge target, batteries that are being charged are excluded from the selection targets. Any of the batteries 12a-12d included in the group of discharge targets may be selected as the discharge target, but it is preferable to select the battery with the highest potential among those included in the group of discharge targets. Once the selection of the discharge target is completed, the process proceeds to step S8.

[0054] Next, in the termination determination process of step S8, it is determined whether to terminate charging / discharging of the power supply device 10. If charging / discharging is to be terminated, the control loop is terminated, and if not, the process proceeds to step S1 and the control loop is repeated. Conditions for terminating charging / discharging include when an instruction to stop charging / discharging is input from outside, when the power supply device 10 detects an abnormality, and so on.

[0055] Next, the selection of a group of charging targets and a group of discharging targets, and the continuation of charging and discharging of the power supply device 10 according to the selection of charging targets and discharging targets will be described with reference to Figs. 5 to 10. In each graph, the horizontal axis indicates the passage of time, and the vertical axis indicates voltage. In each graph, the solid line, dashed line, one-dot chain line, and two-dot chain line indicate the output voltages VBA1 to VBA4 of the batteries 12a to 12d. In addition, the range indicated by the thin dashed line in the graph indicates a predetermined potential range at a certain point in time, and the width is the permissible potential difference Vper. In addition, 34V is shown as an example of a voltage in a fully charged state where the SOC (State Of Charge) of the batteries 12a to 12d is 100%, and 28V is shown as an example of a voltage in a completely discharged state where the SOC is 0%.

[0056] FIG. 5 is a graph for explaining a case where the batteries 12a to 12d continue to output to the load 14. In the example shown in FIG. 5, the output voltages VBA1 to VBA4 of the batteries 12a to 12d are 34V with the same SOC=100%, and the predetermined potential range is set to the width from 34V to the allowable potential difference Vper. At this time, since the batteries 12a to 12d are included within the range of the allowable potential difference Vper, all of the batteries 12a to 12d are selected as the group to be discharged. Of the batteries 12a to 12d selected as the group to be discharged, one that has not been selected as the battery to be charged is selected as the battery to be discharged. In the example shown in FIG. 5, the battery 12a is selected as the battery to be discharged first.

[0057] When the charge / discharge control unit 11 continues to output from the battery 12a to be discharged to the load 14, the output voltage VBA1 of the battery 12a gradually decreases and at a certain point falls outside a predetermined potential range. In this case, the charge / discharge control unit 11 reselects one of the batteries 12b to 12d included in the group of batteries to be discharged and switches the connection with the load 14. Here, when switching from the battery 12a to the battery 12b, by providing an overlap period as shown in Fig. 3, it is possible to suppress momentary interruption during switching and fluctuations in the output voltage from the DC-AC inverter 13.

[0058] Thereafter, the batteries 12b to 12d are successively switched from the group of batteries to be discharged in the same manner, and output from the power supply device 10 is continued. At a certain point in time, all of the output voltages VBA1 to VBA4 of the batteries 12a to 12d fall outside the initially set predetermined potential range. In this case, the charge / discharge control unit 11 resets the predetermined potential range so as to include the output voltages VBA1 to VBA4 of the batteries 12a to 12d, and reselects the group of batteries to be discharged. In the example shown in FIG. 5, the value of the output voltages VBA1 to VBA4 at the time of resetting the predetermined potential range is set as the upper limit, and the width of the allowable potential difference Vper is set as a new predetermined potential range. Also, the batteries 12a to 12d included in the new predetermined potential range are reselected as the group of batteries to be discharged.

[0059] Thereafter, reselection of a discharge target from the discharge target group and reselection of the discharge target group are repeated, and power supply from the power supply device 10 to the load 14 continues until all output voltages VBA1 to VBA4 reach a completely discharged state. During this time, an overlap period is provided in switching of the discharge target by the charge / discharge control unit 11, so that instantaneous interruption and fluctuation in output voltage are suppressed in the output from the power supply device 10. In addition, the output voltages VBA1 to VBA4 of the batteries 12a to 12d included in the discharge target group are always within the range of the allowable potential difference Vper. As a result, even if the internal impedance of the batteries 12a to 12d is small, 10 mΩ or less, the current flowing from the high potential side to the low potential side during the overlap period is suppressed, and output can be continued while avoiding protective operation by the BMS.

[0060] FIG. 6 is a graph for explaining a case where the batteries 12a to 12d continue to be charged from the solar panel 16 or the power supply unit 17. In the example shown in FIG. 6, the output voltages VBA1 to VBA4 of the batteries 12a to 12d are 28V with the same SOC=0%, and the predetermined potential range is set to a width from 28V to the allowable potential difference Vper. At this time, since the batteries 12a to 12d are included within the range of the allowable potential difference Vper, all of the batteries 12a to 12d are selected as a group to be charged. Of the batteries 12a to 12d selected as a group to be charged, one that has not been selected as a battery to be discharged is selected as a battery to be charged. In the example shown in FIG. 6, the battery 12a is selected as a battery to be discharged first.

[0061] When the charge / discharge control unit 11 continues charging the battery 12a to be charged, the output voltage VBA1 of the battery 12a gradually increases and at a certain point falls outside the predetermined potential range. In this case, the charge / discharge control unit 11 reselects one of the batteries 12b to 12d included in the group of batteries to be charged and switches the connection to the solar panel 16 or the power supply unit 17.

[0062] Thereafter, the batteries 12b to 12d are successively switched from the group to be charged in the same manner, and charging to the power supply device 10 is continued. At a certain point in time, all of the output voltages VBA1 to VBA4 of the batteries 12a to 12d fall outside the initially set predetermined potential range. In this case, the charge / discharge control unit 11 resets the predetermined potential range so as to include the output voltages VBA1 to VBA4 of the batteries 12a to 12d, and reselects the group to be charged. In the example shown in FIG. 6, the value of the output voltages VBA1 to VBA4 at the time of resetting the predetermined potential range is set as the lower limit, and the width of the allowable potential difference Vper is set as a new predetermined potential range. Also, the batteries 12a to 12d included in the new predetermined potential range are reselected as the group to be charged.

[0063] Thereafter, reselection of batteries to be charged from the group to be charged and reselection of the group to be charged are repeated, and charging of the power supply device 10 continues until all output voltages VBA1-VBA4 reach a fully charged state. Here, the output voltages VBA1-VBA4 of the batteries 12a-12d included in the group to be charged are always within the range of the allowable potential difference Vper. This makes it easy to include the batteries 12a-12d within the range of Vper at the time of selecting the group to be discharged, even when the power supply device 10 switches from charging to discharging.

[0064] Fig. 7 is a graph for explaining a case where charging is started from the solar panel 16 or the power supply unit 17 during output from the batteries 12a to 12d to the load 14. First, similar to the discharging operation shown in Fig. 5, the batteries 12a to 12d are selected as a group of batteries to be discharged, and output from the power supply device 10 to the load 14 is continued by selecting and switching the batteries 12a to 12d to be discharged. At a certain point in time, when the supply of power to the power supply device 10 is started from the solar panel 16 or the power supply unit 17, the charge / discharge control unit 11 performs a charging operation to the batteries 12a to 12d in parallel with the discharging operation from the batteries 12a to 12d, and switches to a charging / discharging operation.

[0065] 7, the group of batteries to be charged and the group of batteries to be discharged are reset when the power supply device 10 switches to a charging / discharging operation. At this time, it is preferable to set a predetermined potential range so that any of the batteries 12a to 12d are included in the group of batteries to be charged and the group of batteries to be discharged. Specifically, the predetermined potential range for selecting the group of batteries to be charged and the group of batteries to be discharged is made common, and the width of the allowable potential difference Vper is set so that any of the batteries 12a to 12d can be a charging target and a discharging target.

[0066] In the example shown in Fig. 7, the battery 12c selected as the battery to be discharged before switching to the charging / discharging operation continues to be selected as the battery to be discharged. Also, the batteries 12a, 12b, and 12d excluding the battery 12c are selected as a group of batteries to be charged, and among them, the battery 12b is selected as the battery to be charged first. At this time, the battery 12b selected as the battery to be charged is excluded from the group of batteries to be discharged.

[0067] As the charging and discharging operation of the power supply device 10 continues, the output voltage VBA3 of the battery 12c to be discharged gradually decreases and at a certain point falls outside the predetermined potential range. In this case, the charge / discharge control unit 11 reselects one of the batteries 12a and 12d included in the group of batteries to be discharged as a discharge target, and switches the connection with the load 14. At this time, if the battery 12d is newly selected as a discharge target, the battery 12d is excluded from the group of batteries to be charged, and the battery 12c is included in the group of batteries to be charged.

[0068] Furthermore, as the charging and discharging operation of the power supply device 10 continues, the output voltage VBA2 of the battery 12b to be charged gradually increases and at a certain point falls outside the predetermined potential range. In this case, the charge / discharge control unit 11 reselects one of the batteries 12a and 12c included in the group of batteries to be charged, and switches the connection to the solar panel 16 or the power supply unit 17. At this time, if the battery 12a is newly selected as the battery to be charged, the battery 12a is excluded from the group of batteries to be discharged, and the battery 12b is included in the group of batteries to be discharged.

[0069] Thereafter, in the charge / discharge operation of the power supply device 10, reselection and switching of the discharge target and the charge target continues so that the output voltages VBA1-VBA4 of the batteries 12a-12d are included in the range of Vper. Furthermore, when the discharge target and the charge target are reselected, the charge target group and the discharge target group are also reselected as described above. Fig. 7 shows an example in which the power supply device 10 switches from the discharge operation to the charge / discharge operation in which charging and discharging are performed simultaneously, but the switching from the charge operation to the charge / discharge operation shown in Fig. 6 is similar.

[0070] 7 shows a case where the predetermined potential range for selecting a discharge target group and a charge target group during charging and discharging does not change, but the predetermined potential range may be changed over time. As an example, when the power output from the power supply device 10 to the load 14 is greater than the power supplied from the solar panel 16 or the power supply unit 17, the predetermined potential range may be lowered to a lower voltage over time. Conversely, when the power output from the power supply device 10 to the load 14 is less than the power supplied from the solar panel 16 or the power supply unit 17, the predetermined potential range may be raised to a higher voltage over time.

[0071] 7, the output voltages VBA1 to VBA4 of the batteries 12a to 12d included in the group to be discharged and the group to be charged are always within the range of the allowable potential difference Vper. This makes it possible to suppress the current flowing from the high potential side to the low potential side during the overlap period and to continue outputting while avoiding protective operation by the BMS, even when the internal impedance of the batteries 12a to 12d is small, at 10 mΩ or less.

[0072] Fig. 8 is a graph illustrating a case where the battery 12d is not included in the group to be discharged and the batteries 12a to 12c continue to output. The example shown in Fig. 8 assumes a case where the old battery 12d included in the power supply device 10 deteriorates and is replaced with a new battery 12d, and the SOC of the new battery 12d is lower than those of the other batteries 12a to 12c.

[0073] In the example shown in Fig. 8, the output voltages VBA1 to VBA3 of the batteries 12a to 12c are 34V with the same SOC=100%, and the predetermined potential range is set to the width of 34V to the allowable potential difference Vper. At this time, the output voltage VBA4 of the battery 12d is not included within the range of the allowable potential difference Vper, so the batteries 12a to 12c are selected as the group to be discharged, and the battery 12d is excluded from the group to be discharged. Thereafter, similar to the example shown in Fig. 5, the selection and connection of the batteries 12a to 12c to be discharged are switched among the batteries 12a to 12c included in the group to be discharged, and the discharge operation of the power supply device 10 continues while the predetermined potential range is also reset.

[0074] As the discharge operation of the power supply device 10 continues, at a certain point in time, the output voltage VBA4 of the battery 12d falls within a predetermined potential range for selecting a group of batteries to be discharged. After that, the battery 12d is included in the group of batteries to be discharged and is selected as a battery to be discharged. Therefore, the battery 12d, which was not initially included in the group of batteries to be discharged because its output voltage VBA4 is outside the predetermined potential range, is now included in the group of batteries to be discharged as the discharge operation of the power supply device 10 continues, and thereafter, all of the batteries 12a to 12d can continue to discharge within the range of the permissible potential difference Vper.

[0075] Fig. 9 is a graph explaining a case where battery 12d is not included in the group to be charged, and batteries 12a to 12c continue to be charged by solar panel 16 or power supply unit 17. The example shown in Fig. 9 assumes a case where old battery 12d included in power supply device 10 deteriorates and is replaced with new battery 12d, and the SOC of new battery 12d is higher than the other batteries 12a to 12c.

[0076] In the example shown in Fig. 9, the output voltages VBA1-VBA3 of the batteries 12a-12c are 28V with the same SOC=0%, and the predetermined potential range is set to the width of 28V to the allowable potential difference Vper. At this time, the output voltage VBA4 of the battery 12d is not included within the range of the allowable potential difference Vper, so the batteries 12a-12c are selected as the group to be charged, and the battery 12d is excluded from the group to be charged. Thereafter, similar to the example shown in Fig. 6, the selection and connection of the batteries to be charged are switched between the batteries 12a-12c included in the group to be charged, and the charging operation of the power supply device 10 continues while the predetermined potential range is also reset.

[0077] As the charging operation of the power supply device 10 continues, at a certain point in time, the output voltage VBA4 of the battery 12d falls within a predetermined potential range for selecting a group of batteries to be charged. After that, the battery 12d is included in the group of batteries to be charged and is selected as a battery to be charged. Therefore, as the charging operation of the power supply device 10 continues, the battery 12d, which was not initially included in the group of batteries to be charged because its output voltage VBA4 is outside the predetermined potential range, comes to be included in the group of batteries to be charged, and thereafter, the charging operation can be continued with all the batteries 12a to 12d being included within the range of the permissible potential difference Vper.

[0078] Fig. 10 is a graph illustrating a case where the battery 12d is not included in the group to be discharged, and the output from the batteries 12a to 12c continues and the discharge progresses to a completely discharged state. The example shown in Fig. 10 assumes a case where the old battery 12d included in the power supply device 10 deteriorates and is replaced with a new battery 12d, and the SOC of the new battery 12d is higher than that of the other batteries 12a to 12c.

[0079] In the example shown in Fig. 10, the output voltages VBA1 to VBA3 of the batteries 12a to 12c have approximately the same SOC, and the predetermined potential range is set to the width of the permissible potential difference Vper. At this time, the output voltage VBA4 of the battery 12d is not included in the range of the permissible potential difference Vper, so the batteries 12a to 12c are selected as the group of batteries to be discharged, and the battery 12d is excluded from the group of batteries to be discharged. Thereafter, similar to the example shown in Fig. 5, the selection and connection of the batteries to be discharged are switched between the batteries 12a to 12c included in the group of batteries to be discharged, and the discharge operation of the power supply device 10 continues while the predetermined potential range is also reset.

[0080] Thereafter, reselection of a discharge target from the group of discharge targets and reselection of the group of discharge targets are repeated, and power supply from the power supply device 10 to the load 14 continues until the output voltages VBA1-VBA3 of the batteries 12a-12c reach a fully discharged state. At this stage, the charge / discharge control unit 11 resets the predetermined potential range to the allowable potential difference Vper so that the group of discharge targets includes the battery 12d that is not in a fully discharged state.

[0081] Furthermore, the charge / discharge control unit 11 selects the battery 12d included in the group of batteries to be discharged as a battery to be discharged, and executes a discharge operation from the battery 12d. If the output voltage VBA4 of the battery 12d falls outside the predetermined potential range due to the discharge operation, none of the batteries 12a to 12d is included in the group of batteries to be discharged, so the predetermined potential range is reset and the battery 12d is included in the group of batteries to be discharged. The discharge operation with the battery 12d as the discharge target continues until the output voltage VBA4 of the battery 12d reaches an over-discharge state.

[0082] In the example shown in FIG. 10, the discharge operation is switched from the batteries 12a to 12c, which are the initially set group of batteries to be discharged, to the discharge operation of the battery 12d as the discharge target. At this time, the potential difference between the output voltage VBA2 of the battery 12b and the output voltage VBA4 of the battery 12d exceeds the allowable potential difference Vper. Therefore, in this discharge switching, no overlap period is provided in the switching from the battery 12b to the battery 12d by the charge / discharge control unit 11. In this discharge switching, since no overlap period is provided, there is a possibility that a momentary interruption or a fluctuation in the output voltage occurs in the output from the power supply device 10 to the load 14. However, there are cases in which this is preferable to stopping the output from the power supply device 10 when the battery 12d is not in a completely discharged state.

[0083] As shown in Fig. 10, after the discharge switching, the discharge operation from battery 12d continues, and eventually the output voltage VBA4 of battery 12d also reaches 28V, which is the fully discharged state. At this time, batteries 12a-12d are all in a fully discharged state, and the output voltages VBA1-VBA4 of batteries 12a-12d are within the permissible potential difference Vper. Therefore, when charging of power supply device 10 is started from solar panel 16 or power supply unit 17, all of batteries 12a-12d are included in the group to be charged, and the charging operation can be continued as shown in Fig. 6.

[0084] 5 to 10, for simplicity, the case where the batteries 12a to 12d included in the charging group and the discharging group have the same SOC has been described, but the present invention can also be applied to cases where the output voltages VBA1 to VBA4 are different as long as they are within a predetermined potential range. Also, in the examples shown in Fig. 5 to 10, for simplicity, the case where the batteries 12a to 12d are in a fully charged state or a fully discharged state as the initial state has been described, but the SOC in the initial state does not have to be 100% or 0%.

[0085] As described above, in the power supply device 10 and power supply control method of this embodiment, a discharge target is selected from batteries 12a to 12d included in a predetermined potential range, so that the potential difference between batteries 12a and 12b when switching the discharge target is limited, and the current flowing from battery 12a on the higher potential side to battery 12b on the lower potential side can be suppressed. Even when switching the connection of multiple secondary batteries connected to load 14, it is possible to prevent momentary interruptions and suppress fluctuations in output voltage, thereby enabling a stable power supply to be continued.

[0086] Second embodiment Next, a second embodiment of the present invention will be described. Descriptions of contents overlapping with the first embodiment will be omitted. In the first embodiment, an example was shown in which a DC-AC inverter 13 is provided to convert direct current from batteries 12a to 12d into alternating current and output the alternating current to a load 14, but a DC-DC converter may be provided instead of the DC-AC inverter 13. When a DC-DC converter is used, an electronic device driven by direct current is used as the load 14.

[0087] Even when a DC-DC converter is used, the other ends of the switches SW1 and SW2 are connected to the parallel connection section, and the connections are switched in the order of the first connection period, the overlap period, and the second connection period. This prevents momentary interruptions in the voltage input to the DC-DC converter, and keeps it at an intermediate potential during the overlap period.

[0088] Third embodiment Next, a third embodiment of the present invention will be described. Descriptions of contents that overlap with the first embodiment will be omitted. In the first embodiment, an example was shown in which an overlap period was provided in which both batteries were connected to a load when the battery to be discharged was switched from the battery 12a to the battery 12b, but the overlap period may not be provided. In this case, the timing of disconnecting the battery 12a, which was the battery to be discharged, from the load 14 and the timing of connecting the battery 12b to the load 14 are set to be the same.

[0089] In the power supply device 10 and power supply control method of this embodiment, the discharge target is selected from batteries 12a to 12d included in a predetermined potential range, so that the potential difference between batteries 12a and 12b when switching the discharge target is limited, and the current flowing from battery 12a on the higher potential side to battery 12b on the lower potential side can be suppressed. Even when switching the connection of multiple secondary batteries connected to load 14, it is possible to prevent momentary interruptions and suppress fluctuations in output voltage, thereby enabling a stable power supply to be continued.

[0090] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0091] 10…Power supply device 11...Charge / discharge control unit 12a~12d…Battery 13…DC-AC inverter 14. Load 15...AC-DC converter 16…Solar panel 17...Power supply section VBA1~VBA4: Output voltage SW1~SW4…Switches

Claims

1. A plurality of batteries that are charged and discharged; a charge / discharge control unit that selects a discharge target from the plurality of batteries and connects it to a load, and selects a charge target and connects it to a power source; The charge / discharge control unit excludes the charging target from among the plurality of batteries, and selects one from a group of discharging targets included in a first potential range as the discharging target; If there is no battery included in the first potential range among the plurality of batteries, the first potential range is reset; A power supply device, characterized in that the object to be discharged is switched between a first battery and a second battery included in the group of objects to be discharged.

2. 2. The power supply device according to claim 1, the charge / discharge control unit excludes the discharge target from among the plurality of batteries and selects one from a group of batteries to be charged that are included in a second potential range as the battery to be charged; A power supply device comprising: a power supply unit configured to reset the first potential range when none of the plurality of batteries is within the first potential range.

3. 2. The power supply device according to claim 1, An allowable current value is Imax, an impedance from the discharge target to the load is Rimp, The power supply device according to claim 1, wherein the first potential range is a range in which an upper limit and a lower limit of an allowable potential difference Vper satisfy the relationship Vper≦Imax×Rimp.

4. 4. The power supply device according to claim 3, A power supply device characterized in that the permissible potential difference Vper is 3V or less.

5. 2. The power supply device according to claim 1, a power supply device comprising: a power supply unit configured to supply a power to the load when the discharge target is switched from the first battery to the second battery; and an overlap period during which the first battery and the second battery are simultaneously connected to the load.

6. 6. The power supply device according to claim 5, A power supply device, wherein the overlap period is in the range of 100 ms or less.

7. 6. The power supply device according to claim 5, The discharge target is connected to the load via a DC-AC inverter, The power supply device according to claim 1, wherein the overlap period is within a range of 5 periods or less of the output waveform from the DC-AC inverter.

8. 8. The power supply device according to claim 7, A power supply device characterized in that the peak fluctuation of the output waveform during the overlap period is 5% or less.

9. 8. The power supply device according to claim 7, During the overlap period, the potential supplied to the DC-AC inverter is an intermediate potential between the potential of the first battery and the potential of the second battery.

10. A power supply control method for selecting a discharge target from a plurality of batteries that perform charging and discharging, and connecting the selected discharge target to a load, and for selecting a charge target to a power source, comprising the steps of: excluding the charging target among the plurality of batteries, and selecting one from a discharging target group included in a first potential range as the discharging target; If there is no battery included in the first potential range among the plurality of batteries, the first potential range is reset; A power supply control method comprising: switching the discharge target between a first battery and a second battery included in the group of discharge targets.

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