JP2019198169A - Method for controlling nickel zinc battery - Google Patents

Abstract

To prolong life of a nickel zinc battery.SOLUTION: A method for controlling a nickel zinc battery concerning one embodiment includes an SOC control step of controlling SOC of the nickel zinc battery within a range from a first state to a second state. The first state is the SOC when a charge rate in constant voltage charge of the nickel zinc battery becomes 0.05 C or less. The second state is the SOC when open circuit voltage of the nickel zinc battery becomes 1.75 V/cell or less. The SOC control step includes: a charging step of charging the nickel zinc battery at constant voltage of 1.82 to 1.86 V/cell until the SOC reaches the first state when the SOC becomes the second state; and a non-charging step of not charging the nickel zinc battery until the SOC reaches the second state after the charging step.SELECTED DRAWING: Figure 3

Description

  One aspect of the present invention relates to a method for controlling a nickel zinc battery.

  Conventionally, a method for controlling charge / discharge of a storage battery is known. For example, Patent Document 1 describes a method for charging and discharging an alkaline storage battery such as a nickel hydride storage battery. This method includes a step of charging the alkaline storage battery until the state of charge reaches a first state of charge exceeding 90% of the fully charged state, and the state of charge is within a predetermined time after the end of charging. Forcibly discharging the alkaline storage battery until it reaches a second charged state that is lower than one charged state and 50% or more of the fully charged state.

JP 2012-135114 A

  In the case of a nickel-zinc battery, if the battery is discharged until the SOC becomes low, the battery life is shortened. Thus, a charge / discharge method that extends the life of the nickel-zinc battery is desired.

  A method for controlling a nickel-zinc battery according to an aspect of the present invention includes an SOC control step for controlling the SOC of the nickel-zinc battery within a range from a first state to a second state. The SOC when the charge rate in constant voltage charging is 0.05 C or less, and the second state is the SOC when the open circuit voltage of the nickel zinc battery is 1.75 V / cell or less, and the SOC control When the SOC is in the second state, the charging step of charging the nickel zinc battery at a constant voltage of 1.82-1.86 V / cell until the SOC reaches the first state, and after the charging step, A non-charging step of not charging the nickel-zinc battery until the SOC reaches the second state.

  In such an aspect, charge / discharge of the nickel zinc battery is controlled so that the SOC is within a predetermined range (within the range from the first state to the second state). The second state, which is the lower limit of the range, is a state when the open circuit voltage drops to 1.75 V / cell, and in this second state, the SOC of the nickel-zinc battery maintains a relatively high value. Moreover, the 1st state which is the upper limit of a range is not a full charge state. By controlling the charge / discharge of the nickel zinc battery between the first state and the second state, both the float charge state and the deep discharge depth are avoided, so the life of the nickel zinc battery can be further extended. .

  According to one aspect of the present invention, the life of a nickel zinc battery can be further extended.

It is a figure which shows typically an example of a structure of an electrical storage system and its periphery. It is a figure which shows the function structure of the integrated controller which concerns on embodiment. It is a flowchart which shows the process which limits the range of SOC of a nickel zinc battery. It is a flowchart which shows the process which fully charges a nickel zinc battery. It is a graph which shows the example of the discharge characteristic of a nickel zinc battery. It is a flowchart which shows the process which discharges a nickel zinc battery completely.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

[Entire configuration of power storage system]
The power storage system 1 is a system that stores generated electricity and supplies the stored electricity as necessary. The scene where the power storage system 1 is applied is not limited. For example, the power storage system 1 can be applied to both real estate and movable property. As an example of application to real estate, the power storage system 1 may manage electricity generated using renewable energy, and may be used in various places such as a home, an office, a factory, and a farm. As an example of application to movable property, the power storage system 1 may be mounted as a power source in a moving body such as an automobile.

  An overall image of an electric power system including the power storage system 1 will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating an example of the configuration of the power storage system 1 and its surroundings. The power storage system 1 is provided between a supply element 2 that can supply power to the power storage system 1 and a demand element 4 that can receive power from the power storage system 1. A DC system including the power storage system 1 and the supply element 2 and an AC system including the demand element 4 are electrically connected via a PCS (power conditioning system) 3. The power storage system 1, the supply element 2, and the PCS 3 are electrically connected via a DC (Direct Current) bus 6 through which a direct current flows. The demand element 4 and the PCS 3 are electrically connected via an AC (Alternating Current) bus 7 in which an alternating current flows. The electricity generated by the supply element 2 or the electricity stored in the power storage system 1 is supplied to the demand element 4. The power storage system 1 may play a role of mitigating fluctuations in power supply from the supply element 2 to the demand element 4 by using the storage battery like a cushion.

  The supply element 2 is a device or facility that can supply power to the power storage system 1. The kind of supply element 2 is not limited at all. For example, the supply element 2 may be a power generation device that generates power using renewable energy. The type of the power generation method and the power generation device is not limited at all. For example, the power generation device may be a solar power generation device or a wind power generator. Alternatively, the supply element 2 may be a motor mounted on the moving body.

  The demand element 4 is a device or facility that can receive power from the power storage system 1. The type of demand element 4 is not limited at all. For example, the supply element may be an external power system that is a facility of a commercial power source that integrates power generation, power transformation, power transmission, and power distribution. For example, an external power system is provided by a power company. Alternatively, the demand element 4 may be a load that is a set of one or more devices or devices that consume power. Examples of loads include a collection of one or more household or business electric appliances and any component of any device.

  The PCS 3 is a device that converts direct current electricity into alternating current, and is a kind of power converter. The PCS 3 has a DC terminal connected to the DC bus 6 and an AC terminal connected to the AC bus 7.

  The power storage system 1 includes a power storage device 10, a power converter 20, and a general controller 30. One power converter 20 corresponds to one power storage device 10, and these two devices are electrically connected via a DC bus. A pair of the power storage device 10 and the power converter 20 that correspond to each other can also be referred to as a power storage unit. In the example of FIG. 1, the power storage system 1 includes three sets of power storage devices 10 and power converters 20 (three power storage units), but the number of sets is not limited, and may be 1, 2 or 4 or more. When there are a plurality of power storage units, the performance of the power storage device 10 (for example, rated capacity, response speed, etc.) and the performance of the power converter 20 (for example, rated output, response speed, etc.) may be unified. It does not have to be unified. The overall controller 30 is communicably connected to each power storage device 10 and each power converter 20 via the communication line 40.

  The power storage device 10 is a device that stores the electricity provided from the supply element 2 by converting it into chemical energy, and can be charged and discharged. The power storage device 10 can also be used to mitigate (level) fluctuations in DC power provided from the supply element 2. The power storage device 10 includes a nickel zinc battery 11. The nickel zinc battery 11 may be composed of a single cell, or may be composed of a plurality of cells (for example, 7 cells or 8 cells) connected in series. The power storage device 10 further includes a control function such as a battery control unit (BCU), and the control function can transmit data related to the power storage device 10 to the overall controller 30.

  The power converter 20 is a device that controls charging and discharging of the power storage device 10. The power converter 20 receives an instruction signal (data signal) from the overall controller 30 and controls charging / discharging of the power storage device 10 based on the instruction signal. The power converter 20 stores the electricity flowing from the supply element 2 in the power storage device 10 in the charging mode, discharges the power storage device 10 to supply power to the outside in the discharging mode, and performs charging / discharging in the stopped state. Absent. The power converter 20 may be a DC / DC converter, for example.

  The overall controller 30 is a computer (for example, a microcomputer) that controls the power storage device 10 and the power converter 20. FIG. 2 is a diagram illustrating a functional configuration of the overall controller 30. As shown in this figure, the overall controller 30 includes a processor 101, a memory 102, and a communication interface 103 as hardware devices. The processor 101 is, for example, a CPU and the memory 102 is, for example, a flash memory. However, the types of hardware devices that constitute the overall controller 30 are not limited to these, and may be arbitrarily selected. Each function of the overall controller 30 is realized by the processor 101 executing a program stored in the memory 102. For example, the processor 101 performs a predetermined operation on the data read from the memory 102 or the data received via the communication interface 103, and outputs the operation result to the other device, so that the other device is Control. Alternatively, the processor 101 stores the received data or calculation result in the memory 102. The overall controller 30 may be configured by a single computer or a set of a plurality of computers (that is, a distributed system).

  One of the features of the power storage system 1 is the charge / discharge control method of the power storage device 10, and this feature is realized by the overall controller 30. Below, the function and structure of the general controller 30 regarding the control are demonstrated.

  The processor 101 functions as the acquisition unit 31, the determination unit 32, and the instruction unit 33. The acquisition unit 31 is a functional element that acquires data related to the nickel zinc battery 11. The determination unit 32 is a functional element that determines how to charge or discharge the nickel-zinc battery 11 based on the data. The instruction unit 33 is a functional element that outputs an instruction signal based on the determination toward the power storage device 10. In the present embodiment, the overall controller 30 executes the following three types of control.

  As the first control, the overall controller 30 controls the state of charge (SOC) of the nickel zinc battery 11 within a range from the first state to the second state. This control means that the nickel zinc battery 11 is charged or discharged so that the SOC is within the range from the first state to the second state. The first state is a state in which the SOC of the nickel zinc battery 11 to be controlled has reached the upper limit for management, and the second state is a state in which the SOC has reached the lower limit for management.

  As the second control, the overall controller 30 fully charges the nickel zinc battery 11 whose cell balance is lost. The cell balance refers to a state in which performance (for example, energy capacity, voltage, or SOC) among the plurality of cells constituting the nickel zinc battery 11 is not varied or small, and this is a problem for the nickel zinc battery 11. It is in good condition. “The cell balance is lost” means a state in which the variation in performance among a plurality of cells becomes larger than a predetermined level. Full charge means that all of a plurality of cells are fully charged.

  As the third control, the overall controller 30 completely discharges the nickel zinc battery 11 whose average discharge voltage is lower than a predetermined threshold value. The average discharge voltage is an average value of discharge voltages of one or more cells constituting the nickel zinc battery 11. Complete discharge refers to control for discharging the nickel zinc battery 11 so that no electric power is accumulated in all of the one or more cells. Charging is not performed during this complete discharge.

  The memory 102 stores information necessary for the operation of the processor 101. For example, the memory 102 stores the control rule 34. The control rule 34 is information used for controlling charge / discharge of the nickel zinc battery 11. The description method of the control rule 34 is not limited. For example, the control rule 34 may be expressed by any one of a mathematical formula, a threshold value, an algorithm, and a correspondence table, or may be represented by a combination of any two or more of the mathematical formula, the threshold value, the algorithm, and the correspondence table. . Alternatively, the control rule 34 may be a part of a program executed by the processor 101.

  The control rule 34 may be rewritable. For example, when the power storage device 10 or the nickel zinc battery 11 is replaced with another type or a new type of the power storage device 10 or the nickel zinc battery 11 is added, the administrator can change the configuration. The control rule 34 in the memory 102 is rewritten. In this case, the administrator accesses the overall controller 30 with a management computer (not shown) via a predetermined communication network (not shown), and sets a new control rule 34 reflecting the change in configuration to the overall controller 30. You may forward to. By this transfer, the control rule 34 in the memory 102 is rewritten.

  The communication interface 103 executes data transmission / reception in cooperation with the processor 101. For example, the communication interface 103 receives data relating to the nickel zinc battery 11 in cooperation with the acquisition unit 31. Further, the communication interface 103 transmits an instruction signal in cooperation with the instruction unit 33.

[Operation of general controller]
The operation of the overall controller 30 will be described with reference to FIGS. 3 to 6 and a method for controlling the nickel zinc battery according to the present embodiment will be described.

  FIG. 3 is a flowchart showing an example of the first control (processing for limiting the SOC range of the nickel zinc battery 11; SOC control step). FIG. 3 shows processing for one power storage device 10.

  In step S <b> 11, the acquisition unit 31 acquires the SOC of the nickel zinc battery 11. The acquisition unit 31 acquires data indicating the SOC from the power storage device 10 or the power converter 20 corresponding to the power storage device 10 via the communication line 40. The obtained SOC may be the SOC of a single cell that constitutes one nickel-zinc battery 11, or the average SOC that is the average value of the SOC of a plurality of cells that constitute one nickel-zinc battery 11. There may be. Alternatively, the obtained SOC may be the SOC of a specific part of cells constituting one nickel zinc battery 11.

  In step S12, the determination unit 32 determines whether or not the SOC is in the second state (that is, a management lower limit). The control rule 34 includes information on the second state, and therefore the determination unit 32 can determine whether the SOC is in the second state by referring to the control rule 34. The definition of the second state is not limited. For example, the second state may be defined based on the open circuit voltage of the nickel zinc battery 11 after discharge. As an example, the second state may be an SOC when the open circuit voltage becomes 1.75 V / cell or less. Alternatively, the second state may be defined by SOC, and as an example, the second state may be a state where the SOC has decreased to 80%. For the nickel-zinc battery 11 with a rated voltage of 1.9V, the time when the open circuit voltage becomes 1.75V / cell almost corresponds to the time when the SOC becomes 80%. Alternatively, the second state may be defined based on a depth of discharge (DOD), and as an example, the second state may be a state where the DOD has reached 17.5%.

  If the SOC is in the second state (YES in step S12), the process proceeds to step S13, and instruction unit 33 transmits a charge start instruction to power storage device 10 (charging step). This charge start instruction is a control signal for starting a process of charging the nickel zinc battery 11 having a rated voltage of 1.9 V at a constant voltage of 1.82-1.86 V / cell. The value of the voltage is not limited as long as it is within this range, and may be 1.83V, 1.84V, or 1.85V, for example. “Sending an instruction toward the power storage device” means transmitting an instruction to the power storage device 10 or to another device corresponding to the power storage device 10. In the present embodiment, the instruction unit 33 transmits a charge start instruction to the power converter 20 corresponding to the power storage device 10 via the communication line 40. The power converter 20 that has received the charging start instruction shifts to the charging mode, and performs constant voltage charging of 1.82 to 1.86 V / cell for the nickel zinc battery 11 in the power storage device 10.

  On the other hand, when the SOC is not in the second state (NO in step S12), the process proceeds to step S14, and determination unit 32 further determines whether or not the SOC is in the first state (that is, the upper limit for management). judge. The control rule 34 includes information on the first state, and therefore the determination unit 32 can determine whether or not the SOC is in the first state by referring to the control rule 34. The definition of the first state is not limited. For example, the first state may be defined based on a charge rate in constant voltage charging (1.82 to 1.86 V / cell constant voltage charging) of the nickel zinc battery 11. The charge rate refers to the C rate at the time of charging. As an example, the first state may be the SOC when the charge rate becomes 0.05C or less. Alternatively, the first state may be defined by SOC, and as an example, the first state may be a state in which the SOC reaches 92% by constant voltage charging of 1.82 to 1.86 V / cell.

  If the SOC is in the first state (YES in step S14), the process proceeds to step S15, and instruction unit 33 transmits a charge end instruction to power storage device 10 (non-charging step). This charging end instruction is a control signal for ending constant voltage charging of the nickel zinc battery 11. In the present embodiment, the instruction unit 33 transmits a charge end instruction to the power converter 20 corresponding to the power storage device 10 via the communication line 40. The power converter 20 that has received the charge end instruction transitions to the discharge mode or the stop state, and thereby the constant voltage charging of the power storage device 10 is ended.

  On the other hand, when the SOC is not in the first state (NO in step S14), the process ends without the instruction unit 33 outputting a new control signal. When a new instruction signal is not output, the nickel zinc battery 11 in the state of constant voltage charging is continuously charged with the charging start instruction as a trigger, and the nickel zinc battery is stopped or discharged with the charge end instruction as a trigger. 11 is not continuously charged.

  When the power storage system 1 includes a plurality of power storage devices 10, the overall controller 30 executes the processes of steps S <b> 11 to S <b> 15 for all the power storage devices 10. For one power storage device 10, the processes of steps S <b> 11 to S <b> 15 are repeated (for example, periodically), and thereby the SOC of the nickel zinc battery 11 varies within the range from the first state to the second state. According to the charge start instruction in step S13, the nickel zinc battery 11 is charged at a constant voltage until it reaches the first state (charging step). Thereafter, the nickel zinc battery 11 is not charged until the second state is reached in accordance with the charging end instruction in step S15 (non-charging step). Thereafter, constant voltage charging is executed again according to the charging start instruction in step S13, and thereafter the processing is similarly repeated.

  FIG. 4 is a flowchart showing an example of the second control (a process for fully charging the nickel-zinc battery 11). FIG. 4 shows processing for one power storage device 10.

  In step S <b> 21, the acquisition unit 31 acquires data for determining the cell balance of the nickel zinc battery 11. The acquisition unit 31 acquires the data via the communication line 40 from the power storage device 10 or the power converter 20 corresponding to the power storage device 10. Data for determining the cell balance is not limited. For example, the acquisition unit 31 may acquire the integrated amount of charge / discharge current. This integrated amount is the sum of the integrated amount of the charging current flowing through the nickel zinc battery 11 and the integrated amount of the discharging current flowing from the nickel zinc battery 11 after the nickel zinc battery 11 is fully charged last time. Alternatively, the acquisition unit 31 may acquire discharge characteristics (a state in which the voltage decreases as time passes). For example, the acquisition unit 31 may acquire a time change in the relationship between the voltage (V) and the discharge capacity (Ah) as the discharge characteristics. Alternatively, the acquisition unit 31 may acquire charging characteristics (a state of change in which the nickel zinc battery 11 is charged as time passes). For example, the acquisition unit 31 may acquire a change in charging current with time during constant voltage charging in the first control as a charging characteristic.

  In step S22, the determination unit 32 determines cell balance based on the acquired data (cell balance determination step). Corresponding to the fact that the type of data for determining cell balance is not limited, the method for determining cell balance is not limited.

  When using the integrated amount of charge / discharge current, the determination unit 32 determines whether the integrated amount exceeds a predetermined threshold Ta. The specific value of the threshold Ta is not limited, and may be set in consideration of, for example, the characteristics of the nickel zinc battery 11. The determination unit 32 determines that the cell balance is lost when the integrated amount exceeds the threshold Ta, and determines that the cell balance is maintained when the integrated amount is equal to or less than the threshold Ta.

  When the discharge characteristics are used, the determination unit 32 determines whether or not an overdischarge (a phenomenon in which the nickel zinc battery 11 is discharged exceeding an allowable end voltage) has occurred in the nickel zinc battery 11. The determination unit 32 determines that the cell balance is lost if overdischarge has occurred, and determines that the cell balance is maintained if no overdischarge has occurred.

  When the time change in the relationship between the voltage and the discharge capacity is acquired as the discharge characteristics, the determination unit 32 determines whether or not the increase amount of the discharge capacity in the vicinity of the end voltage exceeds a predetermined threshold value Tb. To do. FIG. 5 is a graph showing an example of discharge characteristics. Specifically, the relationship between the voltage and discharge capacity of an 8-series nickel-zinc battery (a nickel-zinc battery composed of 8 cells connected in series). The time change of is shown. The vertical axis represents the voltage per cell (V / cell), and the horizontal axis represents the discharge capacity (Ah) of the entire battery. Legend numbers (88, 174, 260, etc.) indicate the number of charge / discharge cycles. In this graph, a portion surrounded by a frame 200 indicates that the discharge capacity has rapidly increased near the end voltage. This phenomenon means that a cell having a relatively low voltage is over-discharged by being pulled by a cell having a relatively high voltage. Therefore, it is possible to identify overdischarge by detecting a rapid increase in discharge capacity, and thereby to determine the disruption of cell balance. The specific value of the threshold value Tb is not limited, and may be set in consideration of, for example, the characteristics of the nickel zinc battery 11. The determination unit 32 determines that the cell balance is broken (overdischarge has occurred) when the increase amount exceeds the threshold value Tb, and the cell balance is determined when the integrated amount is equal to or less than the threshold value Tb. It is determined that it is maintained (overdischarge has not occurred).

  When charging characteristics are used, the determination unit 32 determines how much the charging characteristics deviate from a predetermined standard model. The determination unit 32 determines that the cell balance is broken when the degree of deviation exceeds a predetermined threshold Tc, and the cell balance is maintained when the degree is less than or equal to the threshold Tc. It is determined that The specific value of the threshold value Tc is not limited, and may be set in consideration of, for example, the characteristics of the nickel zinc battery 11. When the time change of the charging current during constant voltage charging is acquired as the charging characteristic, the determination unit 32 obtains the degree of deviation of the time change of the charging current from the standard model. The determination unit 32 determines that the cell balance is lost when the degree exceeds the threshold Tc, and determines that the cell balance is maintained when the degree is equal to or less than the threshold Tc.

  Thus, the determination method of cell balance is not limited. In any case, the control rule 34 includes information necessary for determining the cell balance, and may include, for example, a threshold Ta, a threshold Tb, or a threshold Tc. The determination unit 32 can determine the cell balance by referring to the control rule 34.

  If it is determined that the cell balance is lost (YES in step S23), the process proceeds to step S24, and instruction unit 33 transmits a full charge instruction to power storage device 10 (full charge step). This full charge instruction is a control signal for fully charging the nickel zinc battery 11. In the present embodiment, the instruction unit 33 transmits a full charge instruction to the power converter 20 corresponding to the power storage device 10 via the communication line 40. The power converter 20 that has received the full charge instruction shifts to the charge mode, and causes the power storage device 10 to perform charging until the nickel zinc battery 11 is fully charged. The full charge instruction has priority over the above charge end instruction, and accordingly, the SOC of the nickel zinc battery 11 exceeds the first state by the full charge instruction and becomes 100% or almost 100%.

  On the other hand, when it is determined that the cell balance is maintained (NO in step S23), instructing unit 33 does not transmit the full charge instruction, and as a result, nickel zinc battery 11 has the SOC changed from the first state to the first state. Control continues up to 2 states.

  When the power storage system 1 includes a plurality of power storage devices 10, the overall controller 30 executes the processes of steps S <b> 21 to S <b> 24 for all the power storage devices 10. For one power storage device 10, the processes of steps S <b> 21 to S <b> 24 are repeated (for example, periodically), and thereby the nickel zinc battery 11 whose cell balance is lost is fully charged. The fully charged nickel zinc battery 11 is again controlled so that the SOC is within the range from the first state to the second state.

  FIG. 6 is a flowchart showing an example of the third control (a process for completely discharging the nickel zinc battery 11). FIG. 6 shows processing for one power storage device 10.

  In step S31, the acquisition unit 31 acquires the average discharge voltage of the nickel zinc battery 11. The average discharge voltage may be, for example, an average value of the discharge voltage of the nickel zinc battery 11 from the start to the end of the discharge in the first control. Alternatively, the average discharge voltage may be an average value of the discharge voltage of the nickel zinc battery 11 from the start to the end of discharge in other control. The acquisition unit 31 acquires data indicating the average discharge voltage from the power storage device 10 or the power converter 20 corresponding to the power storage device 10 via the communication line 40. The obtained average discharge voltage may be an average discharge voltage of a single cell constituting one nickel zinc battery 11 or an average of an average discharge voltage of a plurality of cells constituting one nickel zinc battery 11. It may be a value. Alternatively, the obtained average discharge voltage may be an average discharge voltage of a specific part of cells constituting one nickel zinc battery 11.

  In step S32, the determination part 32 determines whether the average discharge voltage is less than the threshold value Td. The specific value of the threshold value Td is not limited, and may be set in consideration of, for example, the characteristics of the nickel zinc battery 11. The control rule 34 includes the threshold value Td. Therefore, the determination unit 32 can determine whether or not the average discharge voltage is lower than a predetermined reference by referring to the control rule 34.

  If the average discharge voltage is less than threshold value Td (YES in step S32), the process proceeds to step S33, and instruction unit 33 transmits a complete discharge instruction to power storage device 10 (complete discharge step). This complete discharge instruction is a control signal for completely discharging the nickel zinc battery 11. In the present embodiment, the instruction unit 33 transmits a complete discharge instruction to the power converter 20 corresponding to the power storage device 10 via the communication line 40. The power converter 20 that has received the complete discharge instruction shifts to the discharge mode, and causes the power storage device 10 to perform discharge until the nickel zinc battery 11 is completely discharged. The complete discharge instruction has priority over the above charge start instruction. Therefore, the SOC of the nickel zinc battery 11 exceeds the second state by the complete discharge instruction and becomes 0% or almost 0%.

  On the other hand, when the average discharge voltage is equal to or higher than threshold value Td (NO in step S32), instructing unit 33 does not transmit a complete discharge instruction, and as a result, nickel zinc battery 11 has the SOC changed from the first state to the second state. Continue to be controlled in the range up to.

  When the power storage system 1 includes a plurality of power storage devices 10, the overall controller 30 executes the processes of steps S <b> 31 to S <b> 33 for all the power storage devices 10. For one power storage device 10, the processes of steps S31 to S33 are repeated (for example, periodically), whereby the nickel zinc battery 11 whose average discharge voltage is below a certain level is completely discharged. The fully discharged nickel zinc battery 11 is again controlled so that the SOC is within the range from the first state to the second state.

[program]
The control program for causing the computer to function as the overall controller 30 includes program code for causing the computer to function as the acquisition unit 31, the determination unit 32, and the instruction unit 33. This control program may be provided after being fixedly recorded on a tangible recording medium such as a CD-ROM, DVD-ROM, or semiconductor memory. Alternatively, the control program may be provided via a communication network as a data signal superimposed on a carrier wave. The provided control program is stored in the memory 102, for example. The processor 101 executes the control program in cooperation with the memory 102, thereby realizing each functional element described above.

[effect]
As described above, the nickel-zinc battery control method according to one aspect of the present invention includes the SOC control step of controlling the SOC of the nickel-zinc battery within the range from the first state to the second state, and includes the first state. Is the SOC when the charge rate in constant voltage charging of the nickel zinc battery is 0.05 C or less, and the second state is when the open circuit voltage of the nickel zinc battery is 1.75 V / cell or less. A charge step of charging the nickel-zinc battery at a constant voltage of 1.82-1.86 V / cell until the SOC reaches the first state when the SOC is in the second state. And a non-charging step of not charging the nickel zinc battery until the SOC reaches the second state after the charging step.

  In such an aspect, charge / discharge of the nickel zinc battery is controlled so that the SOC is within a predetermined range (within the range from the first state to the second state). The second state, which is the lower limit of the range, is a state when the open circuit voltage drops to 1.75 V / cell, and in this second state, the SOC of the nickel-zinc battery maintains a relatively high value. Moreover, the 1st state which is the upper limit of a range is not a full charge state. By controlling the charge / discharge of the nickel zinc battery between the first state and the second state, both the float charge state and the deep discharge depth are avoided, so the life of the nickel zinc battery can be further extended. . In addition, this control can ensure the regenerative acceptability of the nickel-zinc battery (an index indicating the ease of instant charging).

  In the method for controlling a nickel zinc battery according to another aspect, the nickel zinc battery may include a plurality of cells. In this case, the lifetime of the nickel zinc battery comprised of a plurality of cells can be further extended.

  According to another aspect of the present invention, there is provided a method for controlling a nickel-zinc battery, wherein the nickel-zinc battery has a charge / discharge current integrated amount, a discharge characteristic of the nickel-zinc battery, and a charge characteristic of the nickel-zinc battery. It may further include a cell balance determination step for determining whether or not the cell balance of the zinc battery is lost, and a full charge step for fully charging the nickel zinc battery when it is determined that the cell balance is lost. Since the cell balance of the nickel zinc battery is maintained by this control, the life of the nickel zinc battery can be further extended.

  The method for controlling a nickel zinc battery according to another aspect may further include a complete discharge step of completely discharging the nickel zinc battery when the average discharge voltage of the nickel zinc battery is less than a predetermined threshold value. Since the memory effect of the nickel zinc battery can be eliminated by this control, the life of the nickel zinc battery can be further extended.

[Modification]
The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  At least one of the full charge process (second control) shown in FIG. 4 and the complete discharge process (third control) shown in FIG. 6 may be omitted.

  For example, the processing procedure of the nickel zinc battery control method executed by at least one processor is not limited to the example in the above embodiment. For example, some of the steps (processes) described above may be omitted, or the steps may be executed in a different order. Also, any two or more of the steps described above may be combined, or a part of the steps may be corrected or deleted. Alternatively, other steps may be executed in addition to the above steps. For example, the order of steps S12 and S14 may be reversed in the process shown in FIG.

  When comparing the magnitude relationship between the two values in the power storage system 1, either of the two criteria “greater than” or “greater than” may be used, and the two criteria “less than” and “less than” may be used. Either of these may be used. The selection of such a standard does not change the technical significance of the process of comparing the magnitude relationship between two numerical values.

  In the above embodiment, the overall controller 30 executes the nickel-zinc battery control method, but part or all of this method may be performed manually.

  DESCRIPTION OF SYMBOLS 1 ... Power storage system, 2 ... Supply element, 3 ... PCS, 4 ... Demand element, 6 ... DC bus, 7 ... AC bus, 10 ... Power storage device, 11 ... Nickel zinc battery, 20 ... Power converter, 30 ... General controller , 31 ... acquisition unit, 32 ... determination unit, 33 ... instruction unit, 34 ... control rule, 40 ... communication line.

Claims (4)

An SOC control step for controlling the SOC of the nickel zinc battery within a range from the first state to the second state;
The first state is the SOC when the charge rate in constant voltage charging of the nickel-zinc battery is 0.05C or less,
The second state is the SOC when the open circuit voltage of the nickel-zinc battery becomes 1.75 V / cell or less,
The SOC control step includes:
A charging step of charging the nickel-zinc battery at a constant voltage of 1.82-1.86 V / cell until the SOC reaches the first state when the SOC enters the second state;
A non-charging step of not charging the nickel zinc battery until the SOC reaches the second state after the charging step;
Control method of nickel zinc battery. The nickel zinc battery comprises a plurality of cells;
The control method of the nickel zinc battery of Claim 1. Whether the cell balance of the nickel-zinc battery has been lost based on one of the integrated amount of charge / discharge current of the nickel-zinc battery, the discharge characteristics of the nickel-zinc battery, and the charge characteristics of the nickel-zinc battery A cell balance determination step for determining whether or not
The method for controlling a nickel zinc battery according to claim 2, further comprising a full charge step of fully charging the nickel zinc battery when it is determined that the cell balance is lost. The nickel zinc battery according to any one of claims 1 to 3, further comprising a complete discharge step of completely discharging the nickel zinc battery when an average discharge voltage of the nickel zinc battery is less than a predetermined threshold. Control method.

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