Control device for an energy storage system, energy storage system, method for controlling an energy storage system, and program

Abstract

To provide a control apparatus for a power storage system that allows adjustment to the charging and discharge power of some of secondary batteries in the power storage system as desired without the need to switch the control mode.SOLUTION: A control apparatus for a power storage system is a control apparatus for a power storage system in which a plurality of secondary battery units are connected in parallel via a DC bus, each secondary battery unit including a secondary battery and a DC / DC converter for converting the voltage of charging and discharge power for the secondary battery. The control apparatus comprises: a droop adjustment unit that adjusts an intercept of a droop characteristic of an object unit, which is at least one secondary battery unit among the plurality of secondary battery units, when the object unit is charged and discharged with a desired power; and a limit value changing unit that changes a limit value of the power that is input to and output from the object unit to the desired power.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a control device for a power storage system, a power storage system, a control method for a power storage system, and a program.

Background Art

[0002] In recent years, power storage systems have been used in various facilities such as power generation facilities and factories that utilize renewable energy. A power storage system includes a plurality of battery units having a battery and a DC / DC converter, a PCS (Power Conditioning System), and a DC bus that connects the battery units and the PCS.

[0003] When the power of the power grid is insufficient, for example, the power storage system supplies the power discharged from the battery to the power grid via the PCS. At this time, the discharge power (load sharing) of each battery unit may be adjusted so that the SOC (State of Charge) of each battery becomes substantially uniform. As a technique for equalizing load sharing, Patent Document 1 and Patent Document 2 describe that by performing droop control that changes the droop characteristics to adjust the output voltage, the load sharing between a generator and a battery or the load sharing between power supply devices is made uniform.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​In some cases, such as when there is a difference in State of Charge (SOC) between batteries in a battery storage system, or when measuring the State of Health (SOH) of batteries, it may be necessary to charge and discharge only some batteries at a desired power level. With conventional droop control, the amount of charge and discharge of batteries changes according to the DC bus voltage, making it difficult to charge and discharge at a desired power level. Therefore, in conventional energy storage systems, it was necessary to switch from DC voltage droop control to current control (switch the control mode) when charging and discharging batteries at a desired power level. It would be desirable to be able to arbitrarily adjust the charge and discharge power of only some batteries using a simpler method than switching control modes.

[0006] The purpose of this disclosure is to provide a control device for an energy storage system, an energy storage system, a control method for an energy storage system, and a program that can arbitrarily adjust the charging and discharging power of some of the batteries in the energy storage system without requiring a switch in control mode. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, the control device for an energy storage system is a control device for an energy storage system which connects a plurality of battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, in parallel via a DC bus, and comprises a droop adjustment unit for adjusting the intercept of the droop characteristics of a target unit, which is at least one of the plurality of battery units, when charging and discharging the target unit with a desired power, and a limit value changing unit for changing the limit value of the power input and output to the target unit to the desired power.

[0008] According to one aspect of the present disclosure, the energy storage system comprises a plurality of battery units each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, and the control device described above.

[0009] According to one aspect of the present disclosure, a method for controlling an energy storage system is a method for controlling an energy storage system in which a plurality of battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, are connected in parallel via a DC bus, and the method comprises the steps of adjusting the intercept of the droop characteristics of a target unit when charging and discharging a desired power to at least one of the plurality of battery units, which is a target unit, and changing the limit value of the power to be input and output to the target unit.

[0010] According to one aspect of the present disclosure, the program causes a control device of an energy storage system, which connects a plurality of battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, in parallel via a DC bus, to perform the steps of adjusting the intercept of the droop characteristics of a target unit, which is at least one of the plurality of battery units, and changing the limit value of the power to be input and output to the target unit, when charging and discharging a desired power to the target unit. [Effects of the Invention]

[0011] According to the above embodiment, the charging and discharging power of some of the batteries in the energy storage system can be arbitrarily adjusted without requiring a switch in the control mode. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the overall configuration of an energy storage system according to one embodiment. [Figure 2] This is a block diagram showing the functional configuration of a control device according to one embodiment. [Figure 3] This is a block diagram showing the functional configuration of a DC / DC converter according to one embodiment. [Figure 4] This flowchart shows an example of processing by a control device according to one embodiment. [Figure 5] This figure shows an example of adjusting the droop characteristics according to one embodiment. [Figure 6]It is a diagram for explaining an operation example of an energy storage system according to an embodiment.

Embodiments of the Invention

[0013] (Overall Configuration of Energy Storage System) FIG. 1 is a diagram showing the overall configuration of an energy storage system according to an embodiment. As shown in FIG. 1, the energy storage system 1 includes a PCS (Power Conditioning System) 2, a control device 3, a DC bus 4, and a plurality of battery units 5.

[0014] The PCS 2 is a power conditioner that is connected to the power grid. The PCS 2 has a bidirectional inverter that converts AC power and DC power. The PCS 2 converts the DC power discharged from each battery unit 5 into AC power and outputs it to the power grid. Also, the PCS 2 converts the AC power supplied from the power grid into DC power and outputs it to each battery unit 5.

[0015] The control device 3 controls the charge and discharge of each battery unit. The specific functional configuration of the control device 3 will be described later.

[0016] The DC bus 4 is a bus for connecting the PCS 2 and the plurality of battery units 5.

[0017] The plurality of battery units 5 are connected in parallel to the PCS 2 via the DC bus 4. Each battery unit 5 includes a DC / DC converter 51 and a battery 52. The DC / DC converter 51 converts the DC power supplied from the PCS 2 into a predetermined voltage according to the command of the control device 3 and charges the battery 52. Also, the DC / DC converter 51 converts the discharge power of the battery 52 into a predetermined voltage and supplies it to the PCS 2.

[0018] (Functional Configuration of Control Device) FIG. 2 is a block diagram showing the functional configuration of a control device according to an embodiment. As shown in Figure 2, the control device 3 comprises a processor 31, memory 32, storage 33, and a communication interface 34.

[0019] The processor 31 performs the functions of an acquisition unit 311, a droop adjustment unit 312, and a limit value changing unit 313 by operating according to a predetermined program.

[0020] The acquisition unit 311 acquires battery information D1 indicating the state of the battery 52 from each of the multiple battery units 5. The battery information D1 includes the state of charge (SOC), cell voltage, temperature, etc., of the battery 52.

[0021] The droop adjustment unit 312 generates and transmits a droop command D2 for controlling the droop of each battery unit 5. The droop command D2 includes set values ​​for the slope (droop slope) and intercept (droop intercept) of the droop characteristics of the battery unit 5.

[0022] Conventional droop control involves changing the droop slope while keeping the droop intercept of each battery unit 5 fixed to an initial value (zero) in order to maintain a constant voltage on the DC bus 4 and suppress variations in the state (SOC, etc.) of each battery unit 5. In addition to this, the droop adjustment unit 312 in this embodiment performs a process to change the droop intercept of a target unit, which is at least one of the multiple battery units 5, as part of the droop control when charging or discharging a desired power to that target unit.

[0023] Furthermore, when the droop adjustment unit 312 returns the battery unit 5, which was operating with a desired charge / discharge power, to normal droop control operation (control by droop tilt only), it generates and transmits a droop command D2 that returns the droop intercept of the battery unit 5 to its initial value (zero).

[0024] The limit value modification unit 313 modifies the charge / discharge power limit value (lower limit value or upper limit value) for a battery unit (target unit) that operates at a desired charge / discharge power. The limit value modification unit 313 also transmits the modified limit value as a power limit command D3 to the target unit.

[0025] Furthermore, the limit value changing unit 313 changes the limit value of the charge / discharge power of the battery unit 5 to its initial value when returning the battery unit 5, which was operating at a desired charge / discharge power, to normal operation (control by droop tilt).

[0026] The predetermined program executed by the processor 31 is stored on a computer-readable recording medium. A computer-readable recording medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives the distribution may execute the program. Furthermore, this program may be intended to implement only a part of the functions described above. Moreover, it may be a program that can implement the above functions in combination with a program already recorded in the computer system, a so-called differential file (differential program).

[0027] Memory 32 has a memory area necessary for the operation of the processor 31.

[0028] The storage 33 is a so-called auxiliary storage device, such as an HDD (Hard Disk Drive) or SSD (Solid State Drive). The storage 33 stores data that each part of the processor 31 acquires, generates, and references during processing.

[0029] The communication interface 34 is an interface for sending and receiving various data and control signals (battery information D1, droop command D2, power limit command D3) between each battery unit.

[0030] (Functional configuration of DC / DC converter) Figure 3 is a block diagram showing the functional configuration of a DC / DC converter according to one embodiment. As shown in Figure 3, the DC / DC converter 51 receives a droop command D2 and a power limit command D3 from the control device 3. The droop command D2 is based on the droop intercept V0 and the droop slope K. d The Power Limit Directive D3 includes a lower power limit value LL or an upper power limit value UL.

[0031] Furthermore, the DC / DC converter 51 includes a calculation unit 511, an AVR (Automatic Voltage Regulator) 512, a limiter 513, and a control unit 514.

[0032] The calculation unit 511 calculates the droop section V0 and droop slope K specified by the control device 3. d And the output power P is the measured value of the output of the DC / DC converter 51. out The target voltage of the DC / DC converter 51 is calculated from the droop intercept V0 and droop slope K specified by the control device 3. d The droop intercept and droop slope are changed in steps at a constant rate until the desired result is reached. This suppresses the occurrence of overcurrent and transient fluctuations in DC bus voltage associated with setting changes.

[0033] The AVR512 measures the target voltage and the DC bus voltage V, which is the measured value of the DC bus 4 voltage. bus The difference between these values ​​is input to the PI controller to obtain a power command value that represents the power corresponding to the voltage that the DC / DC converter 51 should output.

[0034] The limiter 513 limits the power command value so that it does not fall below the lower limit value LL or exceed the upper limit value UL set by the control device 3. The limiter 513 changes the lower limit value or upper limit value in steps at a constant rate until it reaches the lower limit value LL or upper limit value UL specified by the control device 3. This suppresses the occurrence of overcurrent and transient fluctuations in DC bus voltage that occur when the settings are changed.

[0035] The control unit 514 controls the power output by the DC / DC converter to the PCS2 side or the battery 52 side based on the power command value adjusted by the limiter 513.

[0036] (Processing flow of the control unit) Figure 4 is a flowchart showing an example of the processing of a control device according to one embodiment. Here, with reference to Figure 4, we will explain the processing flow when the control device 3 operates some of the battery units 5 at a desired charge / discharge power.

[0037] The acquisition unit 311 acquires battery information D1 from each battery unit 5 at predetermined intervals (step S101). This battery information D1 may be displayed on a monitor (not shown) of the control device 3 so that the administrator of the energy storage system 1 can check it at all times.

[0038] Furthermore, the droop adjustment unit 312 receives a specification of the charge and discharge power of the battery unit 5 (target unit) from the administrator of the energy storage system 1 (step S102).

[0039] For example, the administrator may check the battery information D1 of each battery unit 5, select a battery unit 5 whose SOC differs significantly from other units as the target unit, and specify the charge / discharge power for this target unit. Alternatively, the administrator may select a battery unit 5 for which SOH measurement is to be performed as the target unit and specify a predefined charge / discharge power for SOH measurement.

[0040] Next, the droop adjustment unit 312 determines whether to charge or discharge the target unit (step S103). For example, the droop adjustment unit 312 determines that charging is to be performed if the administrator specifies a negative value as the desired charge / discharge power for the target unit, and discharging is to be performed if a positive value is specified. The droop adjustment unit 312 may also accept a charge or discharge specification from the administrator.

[0041] First, let's explain the charging process (processing from step S103; YES onwards). For example, suppose the target unit is the battery unit 5_N2 shown in Figure 1, and we want to charge the target unit 5_N2 with a desired power. When charging the target unit 5_N2 (step S103; YES), the droop adjustment unit 312 adjusts the droop intercept of the target unit 5_N2 in the negative direction (step S104). The droop adjustment unit 312 also transmits the adjusted droop intercept as a droop command D2 to the target unit 5_N2.

[0042] Figure 5 shows an example of adjusting the droop characteristics according to one embodiment. Figure 5 illustrates the droop characteristics of the target unit 5_N2. The vertical axis represents the output voltage of the target unit 5_N2, and the horizontal axis represents the output power of the target unit 5_N2. G1 is the droop characteristics of the target unit 5_N2 before adjustment. P0 represents the output power under no load (rated voltage). The larger the output power to the right of P0, the greater the power output (discharge) from the target unit 5_N2 to PCS2. Conversely, the larger the output power to the left of P0, the greater the power input (charge) from PCS2 to the target unit 5_N2.

[0043] During charging, the droop adjustment unit 312 adjusts the intercept of the droop characteristic G1 of the target unit 5_N2 to the negative direction (rated voltage - a). The adjustment amount - a of the droop intercept may be a fixed value set in advance for each battery unit, or it may be a value specified by the administrator of the energy storage system 1 via the control device 3. G1a is the droop characteristic of the target unit 5_N2 adjusted to the negative direction.

[0044] Next, the limit value modification unit 313 modifies the lower limit value LL of the target unit 5_N2 (step S105). The limit value modification unit 313 also transmits the modified lower limit value LL to the target unit 5_N2 as a power limit command D3.

[0045] Specifically, the limit value changing unit 313 sets the charging power specified by the administrator of the energy storage system 1 as the lower limit value LL of the target unit 5_N2 after the change.

[0046] In other embodiments, the administrator may provide the control device 3 with a table in which desired charging powers are pre-configured according to the state of the battery 52 of each battery unit 5 (such as SOC or a combination of SOC and temperature). In this case, the limit value change unit 313 reads the charging power corresponding to the current battery information D1 (SOC, temperature, etc.) of the target unit 5_N2 from the table and automatically sets it as the modified lower limit value LL for this target unit 5_N2.

[0047] Next, the discharge process (processing from step S103; NO onwards) will be explained. When discharge occurs from the target unit 5_N2 (step S103; NO), the droop adjustment unit 312 adjusts the droop intercept of the target unit 5_N2 in the positive direction (step S106). The droop adjustment unit 312 also transmits the adjusted droop intercept as a droop command D2 to the target unit 5_N2.

[0048] As shown in Figure 5, the droop adjustment unit 312 adjusts the intercept of the droop characteristic G1 of the target unit 5_N2 to the positive direction (rated voltage + b) during discharge. The adjustment amount of the droop intercept + b may be a fixed value set in advance for each battery unit, or it may be a value specified by the administrator of the energy storage system 1 via the control device 3. G1b is the droop characteristic of the target unit 5_N2 adjusted to the positive direction.

[0049] Next, the limit value modification unit 313 modifies the upper limit value UL of the target unit 5_N2 (step S107). The limit value modification unit 313 also transmits the modified upper limit value UL to the target unit 5_N2 as a power limit command D3.

[0050] Specifically, the limit value changing unit 313 sets the discharge power specified by the administrator of the energy storage system 1 as the changed upper limit value UL for the target unit 5_N2.

[0051] In other embodiments, the administrator may provide the control device 3 with a table in which desired discharge powers are pre-configured according to the state of the battery 52 of each battery unit 5 (such as SOC or a combination of SOC and temperature). In this case, the limit value change unit 313 reads the discharge power corresponding to the current battery information D1 (SOC, temperature, etc.) of the target unit 5_N2 from the table and automatically sets it as the changed upper limit value UL for this target unit 5_N2.

[0052] (DC / DC converter operation) Next, the operation of the DC / DC converter 51 of the battery unit 5 will be described in detail. For example, suppose the administrator of the energy storage system 1 specifies that the battery unit 5_N2 (target unit) should be operated at a desired charging power. In this case, the droop adjustment unit 312 of the control device 3 generates a droop command D2 (G1a in Figure 5) that adjusts the droop intercept of the target unit 5_N2 in the negative direction, as shown in the example in Figure 5, and transmits it to the target unit 5_N2 (step S104 in Figure 4). Also, the limit value change unit 313 of the control device 3 generates a power limit command D3 that changes the lower limit value LL to the charging power desired by the administrator, and transmits it to the target unit 5_N2 (step S105 in Figure 4).

[0053] Furthermore, as shown in Figures 3 and 5, the DC / DC converter 51 of the target unit 5_N2 receives the droop command D2 (droop slope, droop intercept) and the output power P of the DC / DC converter 51. outBased on this, the target voltage (operating point voltage V_tgt) is determined.

[0054] As shown in Figure 5, in the droop characteristic G1 before adjustment, the output power of the DC / DC converter 51 at the operating point voltage V_tgt is P1. On the other hand, in the droop characteristic G1a after adjustment, the output power becomes P1'. Since the output power P1' is below the lower limit value LL, the limiter 513 of the DC / DC converter 51 adjusts it to the final output power P1_adj, which becomes the power command value input to the control unit 514. In other words, the output power P1_adj of the DC / DC converter 51 of the target unit 5_N2 matches the charging power specified by the administrator. This makes it possible to charge the target unit 5_N2 with the desired power, regardless of the voltage of the DC bus 4.

[0055] Furthermore, suppose the administrator of the energy storage system 1 specifies that the battery unit 5_N2 (target unit) should be operated at a desired discharge power. In this case, the droop adjustment unit 312 of the control device 3 generates a droop command D2 (G1b in Figure 5) that adjusts the droop intercept of the target unit 5_N2 in the positive direction, as shown in the example in Figure 5, and transmits it to the target unit 5_N2 (step S106 in Figure 4). Also, the limit value change unit 313 of the control device 3 generates a power limit command D3 that changes the upper limit value UL to the discharge power desired by the administrator, and transmits it to the target unit 5_N2 (step S105 in Figure 4).

[0056] As shown in Figure 5, in the droop characteristic G1 before adjustment, the output power of the DC / DC converter 51 at the operating point voltage V_tgt is P2. On the other hand, in the droop characteristic G1b after adjustment, the output power becomes P2'. Since the output power P2' exceeds the upper limit value UL, the limiter 513 of the DC / DC converter 51 adjusts it to the final output power P2_adj, which becomes the power command value input to the control unit 514. In other words, the output power P2_adj of the DC / DC converter 51 of the target unit 5_N2 matches the discharge power specified by the administrator. This makes it possible to discharge the target unit 5_N2 at the desired power, regardless of the voltage of the DC bus 4.

[0057] Figure 6 is a diagram illustrating an example of operation of an energy storage system according to one embodiment. Figure 6 shows the time series of output power for the battery units 5_1, 5_2, 5_N1, 5_N2, and 5_N3 shown in Figure 1, as well as an example of the droop command D2 and power limit command D3.

[0058] As shown in Figure 6, until time t1, the control device 3 performs normal droop control to discharge power from each battery unit 5. At this time, the droop adjustment unit 312 of the control device 3 sends a droop command D2_1 that adjusts the droop slope of each battery unit 5 in order to keep the voltage of the DC bus 4 constant and suppress variations in the State of Charge (SOC) of each battery unit 5. In addition, the limit value change unit 313 of the control device 3 sends a power limit command D3 that leaves the power limit values ​​(lower limit value LL and upper limit value UL) of each battery unit 5 at their initial values.

[0059] Assume that at time t1, the control device 3 receives an instruction from the administrator of the energy storage system 1 to discharge the battery unit 5_N3 at a specified power. In this case, the droop adjustment unit 312 of the control device 3 generates a droop command D2_2 that changes the droop intercept of the battery unit 5_N3 to the positive direction and transmits it to the battery unit 5_N3 (step S106 in Figure 4). Also, the limit value change unit 313 of the control device 3 generates a power limit command D3 that changes the upper limit value UL of the battery unit 5_N3 to the discharge power specified by the administrator and transmits it to the battery unit 5_N3 (step S107 in Figure 4). UL in Figure 6 is the upper limit value set for the battery unit 5_N3.

[0060] As a result, the DC / DC converter 51 of the battery unit 5_N3 outputs (discharges) power at the discharge power specified by the administrator, based on the droop command D2 and the power limit command D3, as explained earlier using Figures 3 and 5. At this time, the DC / DC converter 51 changes the droop intercept V0 and the upper limit value UL in steps at a constant rate until they reach the values ​​specified by the droop command D2_2 and the power limit command D3. Therefore, as shown in Figure 6, the DC / DC converter 51 controls the output so that the discharge power is as specified by the administrator between time t1 and time t2.

[0061] Furthermore, as the discharge power of battery unit 5_N3 increases, the load (discharge power) that the other battery units 5 must share is reduced. Therefore, the control device 3 adjusts the droop tilt of each battery unit 5 using normal droop control (control by droop tilt) to change the load sharing for the other battery units 5_1, 5_2, 5_N1, and 5_N2.

[0062] Furthermore, suppose that at time t3, the control device 3 receives an instruction from the administrator of the energy storage system 1 to charge the battery unit 5_N2 with a specified power. In that case, the droop adjustment unit 312 of the control device 3 generates a droop command D2_3 that changes the droop intercept of the battery unit 5_N2 in the negative direction and transmits it to the battery unit 5_N2 (step S104 in Figure 4). Also, the limit value changing unit 313 of the control device 3 generates a power limit command D3 that changes the lower limit value LL of the battery unit 5_N2 to the charging power specified by the administrator and transmits it to the battery unit 5_N2 (step S105 in Figure 4). LL in Figure 6 is the lower limit value set for the battery unit 5_N2.

[0063] As a result, the DC / DC converter 51 of the battery unit 5_N2 outputs power to the battery 52 at the charging power specified by the administrator, based on the droop command D2 and the power limit command D3, as explained earlier using Figures 3 and 5. At this time, the DC / DC converter 51 changes the droop intercept V0 and the lower limit value LL in steps at a constant rate until they reach the values ​​specified by the droop command D2_3 and the power limit command D3. Therefore, as shown in Figure 6, the DC / DC converter 51 controls the output so that the charging power is as specified by the administrator between time t3 and time t4.

[0064] Furthermore, as the charging power of battery unit 5_N2 increases, the load (discharge power) that the other battery units 5 must share also increases. Therefore, the control device 3 adjusts the droop slope of each battery unit 5 using normal droop control to change the load distribution for the other battery units 5_1, 5_2, and 5_N1.

[0065] (Effect, Action) As described above, the control device 3 of the energy storage system 1 according to this embodiment includes a droop adjustment unit 312 that adjusts the intercept of the droop characteristics of the target unit when charging and discharging a desired power to the target unit, which is at least one of the plurality of battery units 5, and a limit value changing unit 313 that changes the limit value of the power input and output by the target unit.

[0066] As described above, in conventional technology, when charging and discharging only a specific battery unit (target unit) with a desired power, it was necessary to switch the control mode from droop control to current control. In contrast, the control device 3 according to this embodiment can operate the target unit with any charge and discharge power without switching the control mode, i.e., while remaining under droop control, by changing the droop intercept and the limit value of the charge and discharge power using the droop adjustment unit 312 and the limit value changing unit 313.

[0067] Furthermore, the control device 3 includes an acquisition unit 311 that acquires battery information D1 indicating the state of the battery 52 from each of the multiple battery units 5. The limit value changing unit 313 reads the desired power corresponding to the battery information D1 of the target unit from a table that has been set in advance according to the state of the battery 52 of the battery unit 5, and sets it as the limit value of the target unit.

[0068] In this way, the control device 3 can automatically adjust to charge and discharge the battery 52 of the target unit at a preset desired power level according to its state. This reduces the workload on the administrator.

[0069] Furthermore, the droop adjustment unit adjusts the intercept of the droop characteristics in the negative direction when the target unit is being charged, and adjusts the intercept of the droop characteristics in the negative direction when the target unit is being discharged.

[0070] In this way, the control device 3 can be appropriately adjusted so that the target unit is charged and discharged at the desired power (lower limit value LL or upper limit value UL).

[0071] Furthermore, the DC / DC converter 51 of the battery unit 5 gradually changes the intercept and limit values ​​(lower limit value LL or upper limit value UL) of the droop characteristics at a constant rate until they reach the values ​​set by the control device 3.

[0072] In this way, the battery unit 5 can suppress the occurrence of overcurrents and transient fluctuations in DC bus voltage that result from setting changes by the control device 3.

[0073] As described above, embodiments relating to this disclosure have been explained, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0074] <Note> The control device, energy storage system, control method for the energy storage system, and program described in the above-described embodiment can be understood, for example, as follows.

[0075] (1) According to the first embodiment, the control device 3 of the energy storage system 1 is a control device 3 of the energy storage system 1 which connects a plurality of battery units 5, each having a battery 52 and a DC / DC converter 51 that converts the voltage of the charging and discharging power to the battery 52, in parallel via a DC bus 4, and includes a droop adjustment unit 312 that adjusts the intercept of the droop characteristics of the target unit when charging and discharging at least one of the plurality of battery units 5, which is the target unit, with a desired power, and a limit value changing unit 313 that changes the limit value of the power input and output to the target unit to a desired power.

[0076] As described above, in conventional technology, when charging and discharging only a specific battery unit (target unit) with a desired power, it was necessary to switch the control mode from droop control to current control. In contrast, the control device 3 according to this embodiment can operate the target unit with any charge and discharge power without switching the control mode, i.e., while remaining under droop control, by changing the droop intercept and the limit value of the charge and discharge power using the droop adjustment unit 312 and the limit value changing unit 313.

[0077] (2) According to the second embodiment, the control device 3 of the energy storage system 1 according to the first embodiment further includes an acquisition unit 311 that acquires battery information D1 indicating the state of the battery 52 from each of the plurality of battery units 5, and the limit value changing unit 313 reads the desired power corresponding to the battery information D1 of the target unit from a table that has been set in advance according to the state of the battery 52, and sets it as the limit value of the target unit.

[0078] In this way, the control device 3 can automatically adjust to charge and discharge the battery 52 of the target unit at a preset desired power level according to its state. This reduces the workload on the administrator.

[0079] (3) According to the third embodiment, in the control device 3 of the energy storage system 1 according to the first or second embodiment, the droop adjustment unit 312 adjusts the intercept of the droop characteristic in the negative direction when the target unit is being charged, and adjusts the intercept of the droop characteristic in the positive direction when the target unit is being discharged.

[0080] In this way, the control device 3 can be appropriately adjusted so that the target unit is charged and discharged at the desired power (lower limit value LL or upper limit value UL).

[0081] (4) According to the fourth embodiment, the energy storage system 1 comprises a plurality of battery units 5 each having a battery 52 and a DC / DC converter 51 for converting the voltage of the charging and discharging power to the battery 52, and a control device 3 according to any one of the first to third embodiments.

[0082] In this way, the energy storage system 1 can operate the target unit at any charge / discharge power without switching the control mode, that is, while remaining in droop control.

[0083] (5) According to the fifth embodiment, in the energy storage system 1 according to the fourth embodiment, the DC / DC converter 51 changes the intercept and limit values ​​of the droop characteristics in steps at a constant rate until they reach values ​​set by the control device 3.

[0084] In this way, the battery unit 5 can suppress the occurrence of overcurrents and transient fluctuations in DC bus voltage that result from setting changes by the control device 3.

[0085] (6) According to the sixth aspect, the control method for the energy storage system 1 is a method for connecting a plurality of battery units 5, each having a battery 52 and a DC / DC converter 51 for converting the voltage of the charging and discharging power to the battery 52, in parallel via a DC bus 4, and includes the steps of adjusting the intercept of the droop characteristics of the target unit when charging and discharging a desired power to at least one of the plurality of battery units 5, which is a target unit, and changing the limit value of the power to be input and output to the target unit.

[0086] (7) According to the seventh aspect, the program causes a control device 3 of an energy storage system 1, which connects a plurality of battery units 5, each having a battery 52 and a DC / DC converter 51 for converting the voltage of the charging and discharging power to the battery 52, in parallel via a DC bus 4, to perform the steps of adjusting the intercept of the droop characteristics of the target unit and changing the limit value of the power to be input and output to the target unit when charging and discharging a desired power to the target unit, which is at least one of the plurality of battery units 5. [Explanation of Symbols]

[0087] 1. Energy storage system 2 PCS 3. Control device 31 processors 311 Acquisition Department 312 Droop adjustment section 313 Limit Value Change Section 32 memory 33 Storage 34 Communication Interfaces 4 DC buses 5. Battery Unit 51 DC / DC Converter 511 Calculation Unit 512 AVR 513 Limiter 514 Control Unit 52 Storage batteries D1 Battery Information D2 Droop Command D3 Power Limit Command

Claims

1. A control device for an energy storage system, which connects a plurality of battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, in parallel via a DC bus, A droop adjustment unit adjusts the intercept of the droop characteristics of the target unit when charging and discharging at least one of the multiple battery units with a desired power, A limit value changing unit that changes the limit value of the power input and output to the target unit to the desired power, A control device for an energy storage system equipped with the following features.

2. The system further includes an acquisition unit that acquires battery information indicating the status of the battery from each of the multiple battery units, The limit value changing unit reads a desired power corresponding to the battery information of the target unit from a table that has been set in advance, and sets it as the limit value of the target unit. A control device for an energy storage system according to claim 1.

3. The aforementioned droop adjustment unit is When charging the target unit, the intercept of the droop characteristic is adjusted in the negative direction. The intercept of the droop characteristic is adjusted in the positive direction when the target unit is discharged. A control device for an energy storage system according to claim 1.

4. A plurality of battery units each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, A control device according to any one of claims 1 to 3, A battery storage system equipped with the following features.

5. The DC / DC converter changes the intercept of the droop characteristic and the limit value in steps at a constant rate until they reach a value set by the control device. The energy storage system according to claim 4.

6. A control method for an energy storage system in which a plurality of battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, are connected in parallel via a DC bus, When charging and discharging a target unit, which is at least one of the multiple battery units, to a desired power, the steps include adjusting the intercept of the droop characteristics of the target unit, The steps include changing the limit value of the power input and output to the target unit, A method for controlling an energy storage system having [a specific feature / feature].

7. A control device for an energy storage system that connects multiple battery units, each having a battery and a DC / DC converter for converting the voltage of the charging and discharging power to the battery, in parallel via a DC bus, When charging and discharging a target unit, which is at least one of the multiple battery units, to a desired power, the steps include adjusting the intercept of the droop characteristics of the target unit, The steps include changing the limit value of the power input and output to the target unit, A program that executes the command.

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