Power supply device

Abstract

To provide a power supply device in which full charge of a redox flow battery and a secondary battery other than the redox flow battery is stabilized and overcharge is prevented without complicating the configuration.SOLUTION: In the storage battery device, when charging a redox-flow battery 1 and a secondary cell 3, charging of the secondary cell 3 is started by connecting an opening / closing switching device MC2, and before the secondary cell 3 is fully charged, charging of the redox-flow battery 1 is started by connecting an opening / closing switching device MC1. When the voltage value of the DC charging voltage reaches the upper limit of the charging voltage of the secondary cell 3, the switching device MC2 is disconnected, and when the voltage value of the DC charging voltage becomes higher than the upper limit of the charging voltage of the secondary cell 3 and shifts to constant voltage charging within a range not exceeding the upper limit of the charging voltage of the redox-flow cell 1, it is determined that the redox-flow cell is fully charged, and the opening / closing switching device MC1 is disconnected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device that stabilizes full charging and prevents overcharging of redox flow batteries and secondary batteries other than redox flow batteries without complicating the configuration. [Background technology]

[0002] The present applicant has proposed a power supply device suitable for use in emergency power supply (Patent Document 1). This power supply device employs a redox flow battery. This power supply device is comprised of a battery body (a cell stack consisting of multiple battery cells) and an electrolyte tank. The electrolyte in the electrolyte tank is circulated within the battery body by a pump and returned to the electrolyte tank. By circulating the electrolyte, charging and discharging can be performed with the electrolyte in the electrolyte tank via the battery body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6986183 Summary of the Invention [Problem to be solved by the invention]

[0004] Redox flow batteries face challenges in stabilizing full charge and preventing overcharge. Redox flow batteries have high internal resistance, so voltage tends to rise during charging. When charged with a large current, the battery's upper limit voltage is likely to be reached before reaching full charge. If the battery's upper limit voltage is exceeded, gas generation from the electrode surface due to electrolysis, individual differences in battery cells, and uneven electrolyte flow within the battery cell can lead to localized overcharge, increasing the possibility of vanadium compounds being precipitated.

[0005] To prevent this, the charging current must be limited to a certain charging voltage or less, which requires a long charging time and reduces efficiency. Also, if the charging current is too small, there is a risk of overcharging before reaching the upper limit of the voltage operating range.

[0006] On the other hand, secondary batteries other than redox flow batteries that are operated simultaneously with redox flow batteries often have differences in internal resistance and upper limit voltage compared to redox flow batteries, and there is a risk that they will not be able to fully perform due to instability when fully charged or overcharging.

[0007] It is conceivable to judge these batteries not only by the DC charging voltage but also by using a monitor cell for the battery, but this would result in a problem of making the configuration more complicated.

[0008] Therefore, an object of the present invention is to provide a power supply device that stabilizes full charging and prevents overcharging of redox flow batteries and secondary batteries other than redox flow batteries without complicating the configuration.

[0009] Further objects of the present invention will become apparent from the following description. [Means for solving the problem]

[0010] The above problems are solved by the following inventions.

[0011] 1. A power supply device in which an input power source (10) for supplying power is connected to an inverter (12) via an MPPT (maximum power point tracking controller) (11), a storage battery device is connected between the MPPT (11) and the inverter (12), and power is output via the inverter (12), the storage battery device is configured such that the redox flow battery (1) and a secondary battery (3) other than the redox flow battery are connected in parallel via a control circuit (6), the upper limit of the charging voltage of the redox flow battery (1) is configured to be higher than the upper limit of the charging voltage of the secondary battery (3); The control circuit (6) a voltage sensor (5) that measures a DC charging voltage between the redox flow battery (1) and the secondary battery (3); a current sensor (7) for measuring the charging current of the redox flow battery (1); an on-off switch element (MC1) that switches between the MPPT and the inverter and the redox flow battery (1); an on-off switch element (MC2) for switching between the MPPT and the inverter and the secondary battery (3); Equipped with the redox flow battery (1) and the secondary battery (3) can be switched between disconnection, single connection, and parallel connection by operating the on-off switch element (MC1) and the on-off switch element (MC2) on the basis of the voltage value of the DC charging voltage of the voltage sensor (5) and the current value of the charging current of the current sensor (7); When charging the redox flow battery (1) and the secondary battery (3), the on-off switch element (MC2) is connected to start charging the secondary battery (3), and before the secondary battery (3) is fully charged, the on-off switch element (MC1) is connected to start charging the redox flow battery (1); When the voltage value of the DC charging voltage reaches the upper limit of the charging voltage of the secondary battery (3), the ON / OFF switch element (MC2) is disconnected, a transition to constant voltage charging is made within a range in which the voltage value of the DC charging voltage is higher than the upper limit of the charging voltage of the secondary battery (3) but does not exceed the upper limit of the charging voltage of the redox flow battery (1); When the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged, and the on-off switch element (MC1) is disconnected. A power supply device characterized by: 2. 2. The power supply device according to claim 1, wherein when the constant voltage charging state is maintained and the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged and the on-off switch element (MC1) is disconnected. 3. A power supply device in which an input power source (10) for supplying power is connected to an inverter (12) via an MPPT (maximum power point tracking controller) (11), a storage battery device is connected between the MPPT (11) and the inverter (12), and power is output via the inverter (12), the storage battery device is configured such that the redox flow battery (1) and a secondary battery (3) other than the redox flow battery are connected in parallel via a control circuit (6), the upper limit of the charging voltage of the redox flow battery (1) is configured to be higher than the upper limit of the charging voltage of the secondary battery (3); The control circuit (6) a voltage sensor (5) that measures a DC charging voltage between the redox flow battery (1) and the secondary battery (3); a current sensor (7) for measuring the charging current of the redox flow battery (1); an on-off switch element (MC1) that switches between the MPPT and the inverter and the redox flow battery (1); an on-off switch element (MC2) for switching between the MPPT and the inverter and the secondary battery (3); Equipped with the redox flow battery (1) and the secondary battery (3) can be switched between disconnection, single connection, and parallel connection by operating the on-off switch element (MC1) and the on-off switch element (MC2) on the basis of the voltage value of the DC charging voltage of the voltage sensor (5) and the current value of the charging current of the current sensor (7); When charging the redox flow battery (1) and the secondary battery (3), the on-off switch element (MC2) is connected to start charging the secondary battery (3), and before the secondary battery (3) is fully charged, the on-off switch element (MC1) is connected to start charging the redox flow battery (1); When the voltage value of the DC charging voltage reaches the upper limit of the charging voltage of the secondary battery (3), the ON / OFF switch element (MC2) is disconnected, a transition to constant voltage charging is made within a range in which the voltage value of the DC charging voltage is higher than the upper limit of the charging voltage of the secondary battery (3) but does not exceed the upper limit of the charging voltage of the redox flow battery (1); When the charging current value falls below a predetermined current value, the system switches to float charging. A power supply device characterized by: 4. 4. The power supply device according to item 3, wherein when the constant voltage charging state is maintained and the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged and the power supply device transitions to the float charging state. 5. 5. The power supply device according to any one of the above items 1 to 4, wherein the secondary battery (3) is a lithium ion battery in which a plurality of lithium ion cells are connected in series. 6. 6. The power supply device according to item 5, wherein the lithium ion battery is a lithium iron phosphate battery. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a power supply device that stabilizes full charging and prevents overcharging of redox flow batteries and secondary batteries other than redox flow batteries without complicating the configuration. [Brief explanation of the drawings]

[0013] [Figure 1] Block diagram showing the configuration of a power supply device [Figure 2]1 is a flowchart showing control during charging by a control circuit of a power supply device; [Figure 3] Graph showing control during charging by a control circuit of a power supply device [Figure 4] Flowchart showing control during charging (float charging) by the control circuit of the power supply device [Figure 5] Graph showing control during charging (float charging) by the control circuit of the power supply device [Figure 6] Graph showing control during discharge by a control circuit of a power supply device DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] [Configuration of power supply device] FIG. 1 is a block diagram showing the configuration of a power supply device. In the example of the power supply device of the present invention shown in FIG. 1, a power generation device 10 passes through an MPPT (maximum power point tracking controller) 11 and an inverter 12, and outputs the power externally as an AC output. The power supply device of this embodiment is configured such that an input power source that supplies power is connected to an inverter 12, a storage battery device is connected between the MPPT 11 and the inverter 12, and the storage battery device is charged and discharged. The power generation device 10 may be, for example, a solar power generation device or a wind power generation device, and is preferably a solar power generation device. When using a power source that can fully charge a storage battery device using only constant current charging (CC (Constant Current charging)) and the charging time, such as a commercial power source, the usefulness of the present invention is difficult to demonstrate. The storage battery device is configured such that a redox flow battery 1 (sometimes referred to as RFB) and a secondary battery 3 other than a redox flow battery are connected in parallel via a control circuit 6.

[0016] The secondary battery 3 is a secondary battery other than a redox flow battery. Examples of the secondary battery 3 include a lead-acid battery, a nickel-metal hydride battery, and a lithium-ion battery. The secondary battery 3 preferably has a lower upper limit voltage than a redox flow battery, and is preferably a lithium-ion battery that has a high output per unit weight and volume, i.e., a high output density.

[0017] Furthermore, examples of the lithium ion battery include a cobalt-based lithium ion battery and a lithium iron phosphate ion battery, but from the viewpoint of safety, it is preferable to use a lithium iron phosphate ion battery. In the following, in this embodiment, the secondary battery 3 will be described as an example in which it is a lithium ion battery such as a lithium iron phosphate ion battery.

[0018] The current from the power generation device 10 charges the redox flow battery 1 and / or the secondary battery 3 via the MPPT 11. The control circuit 6 controls the MPPT 11, the inverter 12, and the switch MC3, and can supply power directly to an external load, charge each battery in the storage battery device, or combine the output from the power generation device 10 and the storage battery device to supply power to an external load. Furthermore, the electromotive voltage (discharge voltage) of the redox flow battery 1 and / or the secondary battery 3 is connected to an external load via an inverter (INV) 12 as an output voltage VDC of the control circuit 6.

[0019] A first on-off switch element MC1 is connected to the redox flow battery 1. The first on-off switch element MC1 is operated by a control circuit 6 to close (ON) or open (OFF) the connection between the redox flow battery 1 and the control circuit 6.

[0020] A second on / off switch element MC2 is connected to the secondary battery 3. The second on / off switch element MC2 is operated by the control circuit 6 to close (ON) or open (OFF) the connection between the secondary battery 3 and the control circuit 6.

[0021] The control circuit 6 is configured to be able to switch between a single connection and a parallel connection of the redox flow battery 1 and the secondary battery 3 by operating the first and second on / off switch elements MC1 and MC2 to open or close them.

[0022] The control circuit 6 also includes a voltage sensor 5 that measures the charging voltage to the redox flow battery 1 and the secondary battery 3 as a voltage value of a common voltage.

[0023] [Configuration of redox flow battery] The power supply device of the present invention functions to supply power to power consumption facilities such as lighting, a motor, and electronic circuits using a redox flow battery 1. The redox flow battery 1 is composed of a battery cell 1a, a positive electrode electrolyte tank 2a, and a negative electrode electrolyte tank 2b (note that in FIG. 1, the positive electrode electrolyte tank 2a and the negative electrode electrolyte tank 2b are simply shown as a single electrolyte tank). The battery cell 1a and the electrolyte tanks 2a and 2b are connected by piping and function as a redox flow battery 1. Each of the electrolyte tanks 2a and 2b contains a corresponding electrolyte.

[0024] The battery cell 1a has a positive electrode cell that incorporates a positive electrode and through which a positive electrode electrolyte containing vanadium as an active material can be circulated, and a negative electrode cell that incorporates a negative electrode and through which a negative electrode electrolyte containing vanadium as an active material can be circulated. The positive electrode cell and the negative electrode cell are separated by a diaphragm that is permeable to specific ions (note that in Figure 1, these positive electrode cell and negative electrode cell are simply referred to as battery cell 1a).

[0025] The battery cell 1a is configured so that a positive electrode electrolyte can be introduced into and discharged from the positive electrode cell, and a negative electrode electrolyte can be introduced into and discharged from the negative electrode cell. The battery cell 1a is configured by stacking a plurality of cells. Here, the input and output of the redox flow battery 1 is determined by the number of cells, and the amount of power is determined by the amount of electrolyte and the concentration of the active material. For example, when a cell stack of 40 cells of the redox flow battery 1 is used, the electromotive force is approximately 40 to 62 V. However, this is not limited to this, and it is sufficient to provide the necessary number of cells and stacks so that the input and output of the battery can be performed stably.

[0026] Vanadium is preferably used as the active material contained in the positive electrode electrolyte in the positive electrode electrolyte tank 2a and the negative electrode electrolyte in the negative electrode electrolyte tank 2b.

[0027] The positive electrode electrolyte tank 2a and the negative electrode electrolyte tank 2b have larger tank capacities as the amount of supplied electric power increases. For example, although it depends on the concentration of the active material in the electrolyte, if the amount of electrolyte in the tank is 500 L (total of positive and negative electrode solutions), the power consumption is about 10.0 kWh, and if it is 700 L, the power consumption is about 13.5 kWh. In this embodiment, it is preferable to use a tank with the required tank capacity depending on the amount of power required.

[0028] The positive electrode electrolyte tank 2a is configured so that the positive electrode electrolyte can be introduced and discharged, and the negative electrode electrolyte tank 2b is configured so that the negative electrode electrolyte can be introduced and discharged.

[0029] The charge depth can be measured by measuring the OCV (open circuit voltage), which can be done by stopping the charging and discharging of the redox flow battery, or by providing a separate cell for measurement. A measuring device (not shown) capable of measuring the charge depth can be provided at any position.

[0030] The redox flow battery 1 in this embodiment is equipped with a cathode liquid pump (not shown) that introduces a cathode electrolyte into the cathode cell and discharges it from the cathode cell, and an anode liquid pump (not shown) that introduces anode electrolyte into the anode cell and discharges it from the anode cell.

[0031] The piping between the battery cell 1a and the electrolyte tanks 2a and 2b is connected so that the positive electrode electrolyte can be supplied from the positive electrode electrolyte tank 2a to the positive electrode cell, and the negative electrode electrolyte can be supplied from the negative electrode electrolyte tank 2b to the negative electrode cell. The piping is also connected so that the positive electrode electrolyte can be returned from the positive electrode cell to the positive electrode electrolyte tank 2a, and the negative electrode electrolyte can be returned from the negative electrode cell to the negative electrode electrolyte tank 2b.

[0032] Since the electrolyte contains sulfuric acid and is acidic, which may corrode metals, the pipes through which the electrolyte passes are preferably made of corrosion-resistant resin, and the pipes are preferably filled with a reinforcing mesh to prevent breakage.

[0033] The redox flow battery 1 in this embodiment can be, for example, one that has 40 single cells, an input / output of 4 to 6 kW, an electromotive voltage of 40 V to 62 V, and positive and negative electrolyte volumes of approximately 300 L each. Redox flow batteries are characterized by their good current acceptance.

[0034] Redox flow batteries are used in a form called a cell stack, with the battery cell being the smallest unit, and these are used individually or in a form called a cell stack in which multiple cells are stacked. Charging and discharging are carried out by supplying an electrolyte containing vanadium as an active material to the battery cells. The charge and discharge reactions in the positive and negative electrode cells are as follows. Positive electrode cell Charging:V 4+ →V 5+ +e - Discharge:V 5+ +e - →V 4+ Negative electrode cell Charging:V 3+ +e - →V 2+ Discharge:V 2+ →V 3+ +e -

[0035] Known electrodes can be used as the positive electrode and the negative electrode, and are not particularly limited. However, it is preferable that the electrodes simply provide a place for the oxidation-reduction reaction of vanadium in the electrolyte to occur when it passes through the battery cell, but do not react themselves, have a structure and form that allows excellent electrolyte permeability, have as large a surface area as possible, and have low electrical resistance. Furthermore, from the viewpoint of activating the redox reaction, it is preferable that the electrolyte has excellent affinity with the electrolyte (aqueous solution), and from the viewpoint of preventing the decomposition of water, which is a side reaction, it is preferable that the hydrogen overvoltage and oxygen overvoltage are large. Examples of the electrolyte include carbon materials such as carbon felt or graphitized carbon materials, and mesh-shaped titanium or zirconium substrates plated with a noble metal or coated with carbon.

[0036] The diaphragm may be any known diaphragm, and is not particularly limited. For example, an ion exchange membrane made of an organic polymer is preferred, and either a cation exchange membrane or an anion exchange membrane can be used.

[0037] The positive electrode electrolyte contains a tetravalent or pentavalent vanadium compound or both. The positive electrode electrolyte may contain additives such as a conventionally known oxoacid such as nitric acid, a protective colloid agent, or a complexing agent to prevent deposition of deposits.

[0038] The negative electrode electrolyte contains a divalent and / or trivalent vanadium compound, and may contain additives such as a conventionally known oxoacid such as nitric acid, a protective colloid, or a complexing agent to prevent deposition of deposits.

[0039] Generally, vanadium electrolytes are prepared by dissolving vanadium oxide sulfate salt in a sulfuric acid solution to prepare a tetravalent vanadium ion solution, which is then electrolyzed to obtain vanadium ion solutions with different valences. For example, in the positive electrode electrolyte, tetravalent vanadium ions (VO 2+ ) is converted to pentavalent vanadium ions (VO2 + ) solution is prepared. In the negative electrode electrolyte, trivalent vanadium ions (V 3+) is reduced to divalent vanadium ions (V 2+ ) to prepare a solution containing

[0040] The redox flow battery 1 of this embodiment configured as described above is configured so that the upper limit of the charging voltage is higher than the upper limit of the charging voltage of the secondary battery 3.

[0041] The secondary battery 3 is, for example, a lithium iron phosphate battery. The lithium iron phosphate battery can supply power together with the redox flow battery 1 when a large current supply is required, and can also be used in place of the redox flow battery 1 when the redox flow battery 1 is not being charged. For example, a lithium iron phosphate battery having 16 lithium ion cells connected in series can have an electromotive force of 48 V to 56 V and a capacity of 50 Ah. However, the electromotive force and power capacity of the lithium iron phosphate battery can be changed according to the specifications of the redox flow battery, which also makes control easier.

[0042] A lithium iron phosphate battery is configured by connecting a plurality of cells in series, and is equipped with a cell balancer (not shown) that adjusts the capacity balance of each cell.

[0043] Lithium iron phosphate batteries are safe because there is no oxygen release from the positive electrode material, and no combustion occurs at the site of an internal short circuit. In addition, lithium iron phosphate batteries are safe because the short circuited area undergoes a chemical reaction and becomes an insulator, preventing the fire from spreading to the surrounding area.

[0044] 〔charging〕 Charging of the electrolyte tanks 2a and 2b of the redox flow battery 1 is carried out by applying a voltage between the positive electrode and the negative electrode and circulating the positive and negative electrode electrolytes between the battery cell 1a and the electrolyte tanks 2a and 2b using a pump. The secondary battery 3 is charged by applying a voltage between the positive and negative electrodes.

[0045] Charging is performed by supplying power from various power generation devices 10 such as solar power generation (e.g., MPPT type) and wind power generation devices and / or grid power (commercial power supply). As described above, the power generation device 10 is connected to the MPPT 11. The grid power is connected to the control circuit 6 via a rectifier or an AC / DC converter and may be used as various power sources for the control circuit 6 (not shown). Power from the power generation device 10 and the grid power is supplied via the control circuit 6 to the positive and negative electrodes of the battery cell 1a and the positive and negative electrodes of the secondary battery 3.

[0046] [Discharge] The redox flow battery 1 drives two pumps to circulate the electrolyte between the battery cell 1a and the electrolyte tanks 2a and 2b, discharging the charged electrolyte within the battery cell 1a and supplying power to the outside. To supply power to the outside, the power is supplied to the outside via the control circuit 6 and the inverter 12 (power consumption). The control circuit 6 is configured to connect and disconnect the redox flow battery 1, connect and disconnect the secondary battery 3, and start and stop the inverter 12.

[0047] When the charged electrolyte is discharged within the battery cell 1a, the end of the discharge can be detected (determined) by measuring the charging depth of the electrolyte or the voltage of the battery.

[0048] Power is supplied from the secondary battery 3 to the outside from the positive and negative electrodes via the control circuit 6 and the inverter 12 (AC output) (power consumption).

[0049] The redox flow battery 1 and the secondary battery 3 have different voltage operating ranges depending on their types and the number of series connections. This power supply device performs control that corresponds to the difference in the voltage operating ranges of the redox flow battery 1 and the secondary battery 3. In other words, for efficient operation, it is necessary to connect and disconnect the redox flow battery 1 and the secondary battery 3 of the storage battery device as needed, and switch between single connection and parallel connection.

[0050] As described above, the control circuit 6 controls the connection and disconnection of the redox flow battery 1 and the secondary battery 3 during charging and discharging by operating the first and second on / off switch elements MC1 and MC2, and is configured so that when these batteries are connected simultaneously, the redox flow battery 1 and the secondary battery 3 are connected in parallel.

[0051] Fig. 2 is a flowchart showing the control performed by the control circuit of the power supply device during charging, and Fig. 3 is a graph showing the control performed by the control circuit of the power supply device during charging. The following will be explained together with the flowchart in FIG. 2 and the graph in FIG.

[0052] First, as shown in FIG. 2, the power supply device performs bulk charging, which is charging with the maximum power from the power generation device 10 (S1).

[0053] During this bulk charging, the control circuit 6 measures the charging voltage to the redox flow battery 1 and the secondary battery 3 as a voltage value of a common voltage using the voltage sensor 5, as shown in FIG.

[0054] The control circuit 6 operates the second on-off switch element MC2 to open (disconnect) when the voltage value of the DC charging voltage (also referred to as "common voltage" as necessary) measured by the voltage sensor 5 during charging of the redox flow battery 1 and the secondary battery 3 based on the input voltage CV from the power generation device 10 to the storage battery device reaches the upper limit value of the charging voltage of the secondary battery 3.

[0055] In this embodiment, if the secondary battery 3 is connected alone and continues to be charged, and then is disconnected when the upper limit voltage is reached, there is a risk that the amount of charge will be insufficient if the charging current is large at the end of charging.

[0056] Therefore, in the present invention, the redox flow battery 1 is connected in parallel with the secondary battery 3 before the DC voltage reaches the upper limit charging voltage (disconnection voltage) of the secondary battery 3. This connects the secondary battery 3 and the redox flow battery 1 in parallel, dispersing the charging current and suppressing an increase in DC voltage. In other words, the parallel connection of the redox flow battery 1 and the secondary battery 3 results in "pseudo constant voltage charging (CV (Constant Voltage) charging)," which makes it possible to charge the secondary battery 3 to a state closer to full charge, and fully utilizing the capacity characteristics of the secondary battery 3. Here, "pseudo constant voltage charging" refers to the situation where, unlike normal constant voltage charging, the voltage is not constant, but the charging current decreases as the secondary battery 3 approaches full charge and the resistance increases.

[0057] In order to make the most of the capacity of the redox flow battery 1, it is appropriate that the lower limit voltage of the secondary battery 3 is equal to or lower than the lower limit voltage of the redox flow battery 1. Therefore, it is preferable that the upper limit charging voltage of the secondary battery 3 is lower than the upper limit charging voltage of the redox flow battery 1, but this is not limiting. The redox flow battery 1 has a charge voltage of, for example, 62 V, and when the discharge voltage reaches, for example, about 48 V, there is almost no remaining capacity. The secondary battery 3 has a charging voltage of, for example, 56V, and when the discharging voltage reaches, for example, about 47V, there is almost no remaining capacity.

[0058] As shown in FIG. 3, just before the DC charging voltage reaches 56 V, the redox flow battery 1 is connected (the first on-off switch element MC1 is closed), creating a pseudo-constant voltage charge. When the DC charging voltage reaches 56 V, the secondary battery 3 is disconnected (the second on-off switch element MC2 is opened), and thereafter charging continues with the redox flow battery 1 alone (the first on-off switch element MC1 remains closed), making it possible to make the most of the capacities of the redox flow battery 1 and the secondary battery 3.

[0059] Next, bulk charging continues until the charging voltage to the redox flow battery 1 reaches a predetermined value (e.g., 62 V) that is equal to or lower than the upper charging voltage limit (NO in S2), and once the predetermined value is reached (YES in S2), the process switches to constant voltage charging (absorb charging), in which charging is performed at a constant voltage that is a predetermined value that is equal to or lower than the upper charging voltage limit (S3). In other words, the process switches to absorb charging within a range that does not exceed the upper charging voltage limit of the redox flow battery 1. In this embodiment, if the predetermined value for transitioning to constant voltage charging is too low, the solar generated power will be wasted, so the closer it is to the upper limit charging voltage of the redox flow battery 1, the better. Furthermore, when the redox flow battery 1 is charged at a low current, it is preferable to reduce the flow rate of the electrolyte to make it easier for the voltage to increase.

[0060] Next, while maintaining the constant voltage charging (absorption charging) state, it is determined whether the charging current (IRfB) to the redox flow battery 1 has decreased to a predetermined value or less (S4), and if it is determined that the current has decreased, a timer is started (S5). This timer is for avoiding a temporary decrease in the predetermined current. It is determined whether the charging current (S4) remains below a predetermined value until the timer has counted down for a predetermined time (S6), and if so (YES in S6), the timer is ended (S7), and the first open / close switch element MC1 is opened to disconnect RFB (S8). Here, the timer in (S5) may not be provided. Also, in S6, it may be determined whether the charging current in (S4) has been maintained at a predetermined value or less, and if not, the process may return to (S4) and determine again whether the charging current is at a predetermined value or less.

[0061] When the conditions for terminating constant-voltage charging of the redox flow battery 1 are met, the constant-voltage charging is maintained for a certain period of time by adjusting the timer. This is to prevent malfunctions when using a power generation device 10 that undergoes output fluctuations, such as solar power generation or wind power generation, even if there are momentary fluctuations in the charging voltage or charging current due to output fluctuations of the power generation device 10. Malfunctions caused by momentary fluctuations in the charging voltage or charging current could cause charging to stop midway, resulting in insufficient charging, but this power supply device can prevent such malfunctions.

[0062] The predetermined time after transition to constant-voltage charging, which is the condition for terminating constant-voltage charging, is the time when the redox flow battery 1 is expected to be fully charged, and can be determined by counting (gross and net) the time when both voltage and current conditions are met. However, this cannot be determined uniformly because it is affected by various factors, such as the cell capacity (upper voltage limit), the amount of electrolyte, and the conditions for full charge. Furthermore, if this phase is absent or is too short, solar power generation will be wasted or charging will end before the battery is fully charged, which is inefficient.

[0063] A feature of this power supply device is that, during charging, the states of the redox flow battery 1 and the secondary battery 3 are not managed individually, but in principle, the state is determined solely based on the DC charging voltage detected by the voltage sensor 5, and the redox flow battery 1 and the secondary battery 3 are connected or disconnected accordingly. This eliminates the need for a monitor cell, which is primarily used in redox flow batteries 1, and simplifies the structure, thereby reducing costs.

[0064] However, when managing the battery using only the DC charging voltage, there are issues such as stabilizing the full charge of the redox flow battery 1 and preventing overcharging. This is because the redox flow battery 1 has a large internal resistance, and the state of full charge varies greatly depending on the magnitude of the charging current (IRfB) at any given time. When charging with a large current, the upper limit of the voltage operating range is easily reached, and if a full charge is determined based solely on voltage detection of the DC charging voltage (input voltage CV), there is a risk that the actual charge amount may not be sufficient. Conversely, if the charging current (IRfB) is too small, there is a risk of overcharging before the upper limit of the voltage operating range is reached.

[0065] Therefore, in this power supply device, the DC charging voltage (input voltage CV) is switched to constant voltage charging within a range that does not exceed the upper limit voltage of the redox flow battery 1, and when the charging current (IRfB) becomes equal to or less than a predetermined value (for example, 20 A or less), the redox flow battery 1 is considered to be fully charged and is disconnected (the first on-off switch element MC1 is opened).

[0066] 2, the timer in S5 may be started when the process moves to S3. In this case, instead of the process in S6, the absorb charge time may be set to a predetermined time, and instead of the process of monitoring whether that time has elapsed, the process may proceed to S7 once that time has elapsed. This reduces the number of decision processes, thereby simplifying the control circuit.

[0067] FIG. 4 is a flowchart showing control (float charging) during charging by the control circuit of the power supply device. FIG. 5 is a graph showing control (float charging) during charging by the control circuit of the power supply device. As shown in FIGS. 4 and 5, this power supply device may be controlled to transition to float charging when the termination condition for constant voltage charging of the redox flow battery 1 is met.

[0068] In this control, as shown in FIG. 4, the process up to the point where the redox flow battery 1 alone transitions to constant voltage charging (S1 to S7) is the same as the control described above with reference to FIG.

[0069] When the timer in (S7) is finished, the process shifts to float charging (S9). Float charging has the effect of bringing the redox flow battery 1 into a more fully charged state.

[0070] In float charging, when the redox flow battery 1 is fully charged, the charging current passes through a bypass circuit (not shown) within the control circuit 6, eliminating the burden on the redox flow battery 1. Although the charging voltage continues to be applied, the charging current to the redox flow battery 1 becomes 0 A. By accurately maintaining the float voltage without applying a load to the redox flow battery 1, overcharging does not occur. Float charging can maximize the lifespan of the redox flow battery 1.

[0071] The purpose of float charging is to make final adjustments to the depth of charge. Float charging is a constant-voltage charge using different voltages. The float charging voltage is preferably equal to or less than the value calculated by multiplying the OCV value by the number of series-connected cells of the redox flow battery 1, which is defined as a fully charged state for the redox flow battery 1.

[0072] When the battery is shifted to float charging, the charging voltage can be set to a voltage (e.g., 58.8 V) lower than the voltage (e.g., 62 V) in constant voltage charging, as shown in Fig. 5. Furthermore, if the charging current (IRfB) further decreases during float charging, the first on-off switch element MC1 may be opened to disconnect the redox flow battery 1.

[0073] 4, the processes of S4 and S6 may be omitted and the timer of S5 may be started when the process moves to S3. In this case, instead of the process of S6, the absorb charge time may be set to a predetermined time and the process may be changed to monitor whether that time has elapsed, and once that time has elapsed, the process may proceed to S7. This reduces the number of decision processes and simplifies the control circuit.

[0074] [Electrolyte Flow Rate Control] In any of the charge controls shown in FIGS. 2 and 3 and FIGS. 4 and 5, the charge current value and the flow rate of the electrolyte may be controlled in conjunction with each other in order to control the reaction resistance of the redox flow battery 1. A characteristic of redox flow batteries is that the ion exchange rate on the electrode surface changes depending on the speed at which the electrolyte is circulated, which in turn changes the reaction resistance of the battery. Increasing the electrolyte flow rate per hour increases the ion exchange rate on the electrode surface and decreases the reaction resistance of the battery. Conversely, decreasing the electrolyte flow rate decreases the ion exchange rate and increases the reaction resistance of the battery. Utilizing this, it is possible to achieve a more favorable state of charge.

[0075] Towards the end of charging the secondary battery 3, the electromotive force of the redox flow battery 1 decreases relative to the rise in the electromotive force of the secondary battery 3, and the charging current of the redox flow battery 1 increases. If the electrolyte flow rate is increased in conjunction with this, the reaction resistance of the redox flow battery 1 decreases, the relative electromotive force difference increases, and the state of charge of the secondary battery 3 approaches a sufficient level. The charging speed of each battery 1 and 3 changes, but the charging speed of the system as a whole remains the same. The flow rate of the electrolyte can be adjusted by adjusting the variable input voltage in the case of a DC pump, and by adjusting the frequency using an inverter in the case of an AC pump.

[0076] The redox flow battery 1 can be designed separately for the cell design and the operational full charge design. Because the cell design is an input / output design, there can be a large difference between the upper limit of the cell's designed charging voltage and the electromotive voltage calculated from full charging using the OCV value (OCV value * number of cells in series at full charge). Therefore, when the redox flow battery 1 is charged at a small current, there is a risk that the charging voltage will not reach the upper limit and the battery may become overcharged. Therefore, when the charging current is small, the electrolyte flow rate is reduced to intentionally slow down the ion exchange rate on the electrode surface, thereby increasing the reaction resistance and making it easier for the electromotive voltage of the redox flow battery 1 to increase. This makes it easier to reach the upper limit charging voltage and prevents the battery from falling into an overcharged state.

[0077] [During discharge] FIG. 6 is a graph showing the control during discharge by the control circuit of the power supply device. When charging has progressed to a certain extent, discharging begins with only the redox flow battery 1 connected for charging, as shown in Figure 6. As discharging progresses and the voltage drops to a predetermined level (e.g., 54 V), the secondary battery 3 is reconnected. However, if the load current suddenly increases before this, the voltage of the redox flow battery 1 will drop sharply, and the connection operation of the secondary battery 3 (operation of the first ON / OFF switch element MC1) may not be completed in time, causing the inverter 12 to stop. Because the redox flow battery 1 has high internal resistance, when a large current is discharged, the input voltage to the inverter 12 may drop below the inverter's allowable voltage range.

[0078] As a countermeasure, in this power supply device, a bypass diode (not shown) is provided in parallel with the second on / off switch element MC2 of the secondary battery 3 to create a bypass path, thereby compensating for the voltage drop of the redox flow battery 1.

[0079] In this way, when this power supply device is used to start a large starter motor, if the input voltage to the inverter 12 drops below the allowable voltage range due to the supply of a large current from the redox flow battery 1 to the outside, power will be supplied from the secondary battery 3, and the drop in the input voltage to the inverter 12 can be reduced. [Explanation of symbols]

[0080] 1. Redox flow battery 1a battery cell 2a Positive electrode electrolyte tank 2b Negative and positive electrode electrolyte tanks 3 Secondary battery 6 Control Circuit 10 Power generating equipment 11 MPPT 12 inverters

Claims

1. A power supply device in which an input power source (10) for supplying power is connected to an inverter (12) via an MPPT (maximum power point tracking controller) (11), a storage battery device is connected between the MPPT (11) and the inverter (12), and power is output via the inverter (12), The storage battery device is configured such that the redox flow battery (1) and a secondary battery (3) other than the redox flow battery are connected in parallel via a control circuit (6), The upper limit of the charging voltage of the redox flow battery (1) is configured to be higher than the upper limit of the charging voltage of the secondary battery (3), The control circuit (6) a voltage sensor (5) that measures a DC charging voltage between the redox flow battery (1) and the secondary battery (3); a current sensor (7) for measuring the charging current of the redox flow battery (1); an on-off switch element (MC1) that switches between the MPPT and the inverter and the redox flow battery (1); an on-off switch element (MC2) for switching between the MPPT and the inverter and the secondary battery (3); Equipped with the redox flow battery (1) and the secondary battery (3) can be switched between disconnection, single connection, and parallel connection by operating the on-off switch element (MC1) and the on-off switch element (MC2) on the basis of the voltage value of the DC charging voltage of the voltage sensor (5) and the current value of the charging current of the current sensor (7); When charging the redox flow battery (1) and the secondary battery (3), the on-off switch element (MC2) is connected to start charging the secondary battery (3), and before the secondary battery (3) is fully charged, the on-off switch element (MC1) is connected to start charging the redox flow battery (1); When the voltage value of the DC charging voltage reaches the upper limit of the charging voltage of the secondary battery (3), the ON / OFF switch element (MC2) is disconnected, a transition to constant voltage charging is made within a range in which the voltage value of the DC charging voltage is higher than the upper limit of the charging voltage of the secondary battery (3) but does not exceed the upper limit of the charging voltage of the redox flow battery (1); When the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged, and the on-off switch element (MC1) is disconnected. A power supply device characterized by:

2. 2. The power supply device according to claim 1, wherein when the constant voltage charging state is maintained and the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged and the on-off switch element (MC1) is disconnected.

3. A power supply device in which an input power source (10) for supplying power is connected to an inverter (12) via an MPPT (maximum power point tracking controller) (11), a storage battery device is connected between the MPPT (11) and the inverter (12), and power is output via the inverter (12), The storage battery device is configured such that the redox flow battery (1) and a secondary battery (3) other than the redox flow battery are connected in parallel via a control circuit (6), The upper limit of the charging voltage of the redox flow battery (1) is configured to be higher than the upper limit of the charging voltage of the secondary battery (3), The control circuit (6) a voltage sensor (5) that measures a DC charging voltage between the redox flow battery (1) and the secondary battery (3); a current sensor (7) for measuring the charging current of the redox flow battery (1); an on-off switch element (MC1) that switches between the MPPT and the inverter and the redox flow battery (1); an on-off switch element (MC2) for switching between the MPPT and the inverter and the secondary battery (3); Equipped with the redox flow battery (1) and the secondary battery (3) can be switched between disconnection, single connection, and parallel connection by operating the on-off switch element (MC1) and the on-off switch element (MC2) on the basis of the voltage value of the DC charging voltage of the voltage sensor (5) and the current value of the charging current of the current sensor (7); When charging the redox flow battery (1) and the secondary battery (3), the on-off switch element (MC2) is connected to start charging the secondary battery (3), and before the secondary battery (3) is fully charged, the on-off switch element (MC1) is connected to start charging the redox flow battery (1); When the voltage value of the DC charging voltage reaches the upper limit of the charging voltage of the secondary battery (3), the ON / OFF switch element (MC2) is disconnected, a transition to constant voltage charging is made within a range in which the voltage value of the DC charging voltage is higher than the upper limit of the charging voltage of the secondary battery (3) but does not exceed the upper limit of the charging voltage of the redox flow battery (1); When the charging current value falls below a predetermined current value, the system switches to float charging. A power supply device characterized by:

4. 4. The power supply device according to claim 3, wherein when the constant voltage charging state is maintained and the current value of the charging current becomes equal to or less than a predetermined current value, it is determined that the redox flow battery is fully charged and the power supply device transitions to the float charging state.

5. 5. The power supply device according to claim 1, wherein the secondary battery (3) is a lithium ion battery in which a plurality of lithium ion cells are connected in series.

6. 6. The power supply device according to claim 5, wherein the lithium ion battery is a lithium iron phosphate battery.

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