WO2024202142A1 - Control apparatus, power conditioner, control method, and program - Google Patents

Abstract

A control apparatus comprising: a voltage acquisition unit that acquires a voltage of a DC bus connecting a power conditioner and a storage battery unit; an output limit unit that sets to zero an output limit value of PCS output power which is power output to the load side by the power conditioner when the voltage exceeds an upper limit threshold value or when the voltage falls below a lower limit threshold value; and a limit release unit that gradually increases or gradually decreases the output limit value after the output limit value is set to zero.

Description

CONTROL DEVICE, POWER CONDITIONER, CONTROL METHOD, AND PROGRAM

The present disclosure relates to a control device, a power conditioner, a control method, and a program.
This application claims priority based on Japanese Patent Application No. 2023-057834, filed on March 31, 2023, the contents of which are incorporated herein by reference.

In recent years, energy storage systems have come to be used in a variety of locations, such as power generation facilities and factories that use renewable energy. Energy storage systems are equipped with multiple battery units, each having a storage battery and a DC/DC converter, a PCS (Power Conditioning System), and a DC bus that connects the battery units and the PCS.

In addition, if the total chargeable/dischargeable power of the entire battery unit becomes smaller than the PCS output power output from the PCS to the load side (to the power grid when the battery unit is discharging, and to the battery unit when it is charging), for example when the DC/DC converter trips, the battery will over-discharge or the DC bus will overvoltage, causing the system to stop. In order to continue operating the battery storage system, it is necessary to limit the PCS output power when the DC bus voltage drops or rises significantly. For example, Patent Document 1 describes how, when starting a load with a battery pack (energy storage system) made up of multiple single cells, if over-discharge of any of the single cells is detected, the power supply from the battery pack to the load will be limited or stopped.

Japanese Patent No. 4821363

FIG. 8 is a diagram showing an example of an output limiting process of a power storage system according to the conventional technology.
As shown in Fig. 8, the conventional battery storage system changes the output limit value for limiting the PCS output power P _PCS in response to an increase or decrease in the DC bus voltage V _dc . A positive value of the output limit value indicates charging to the battery unit, and a negative value indicates discharging from the battery unit.

For example, if a trip occurs during discharge from the storage battery unit, the total dischargeable power of the storage battery unit decreases (a1 in FIG. 8 ), and the DC bus voltage V _dc decreases (a2 in FIG. 8 ). At this time, when the storage system detects a decrease in the DC bus voltage V _{dc _t91} at time t91, it gradually decreases the PCS output power P _PCS (gradually increases the value of the output limit value) to limit the discharge from the storage battery unit (a3 in FIG. 8 ). Then, at time t92, the PCS output power P _PCS can be decreased to the total dischargeable power of the storage battery unit, and the storage battery system stops the process of limiting the discharge power. However, the DC bus voltage V _dc continues to decrease until the PCS output power P _PCS is in balance with the total dischargeable power. Then, the DC bus voltage V _dc continues to decrease until time t92, and thereafter, the storage system continues to operate while maintaining the DC bus voltage in an abnormally low state (the value of the DC bus voltage V _{dc _t92} at time t92) (a4 in FIG. 8 ).

Similarly, suppose that the DC/DC bus of one of the storage battery units is tripped during charging of the storage battery units. Then, the total chargeable power of the storage battery units decreases (b1 in FIG. 8 ), and the DC bus voltage V _dc increases (b2 in FIG. 8 ). At this time, when the storage system detects an increase in the DC bus voltage V _{dc _t93} at time t93, it gradually reduces the PCS output power P _PCS (gradually reduces the value of the output limit value) to limit the charging of the storage battery units (b3 in FIG. 8 ). Then, at time t94, the PCS output power P _PCS can be reduced to the total chargeable power of the storage battery units, so the storage battery system stops the process of limiting the charging power. However, the DC bus voltage V _dc continues to rise until the PCS output power P _PCS balances with the total chargeable power. As a result, the DC bus voltage _Vdc continues to rise until time t94, and thereafter, the energy storage system continues to operate while maintaining the DC bus voltage at an abnormally high state (the value of the DC bus voltage _{Vdc_t94} at time t94) (b4 in FIG. 8).

The objective of the present disclosure is to provide a control device, power conditioner, control method, and program that can prevent the DC bus voltage from exceeding the normal operating voltage range and continue operation when a drop or rise in the DC bus voltage is detected.

According to one aspect of the present disclosure, the control device includes a voltage acquisition unit that acquires the voltage of a DC bus that connects a power conditioning system (PCS) and a storage battery unit, an output limiting unit that sets to zero the output limit value of the PCS output power, which is the power that the PCS outputs to the load, when the voltage exceeds an upper threshold or falls below a lower threshold, and a limit release unit that gradually increases or decreases the output limit value after setting the output limit value to zero.

According to one aspect of the present disclosure, the control method includes the steps of acquiring the voltage of a DC bus connecting a power conditioning system (PCS) and a storage battery unit, setting to zero an output limit value of the PCS output power, which is the power output by the PCS to the load, when the voltage exceeds an upper threshold or falls below a lower threshold, and gradually increasing or decreasing the output limit value after setting the output limit value to zero.

According to one aspect of the present disclosure, the program causes the control device to execute the steps of acquiring the voltage of a DC bus connecting a power conditioning system (PCS) and a storage battery unit, setting to zero the output limit value of the PCS output power, which is the power output by the PCS to the load, when the voltage exceeds an upper threshold or falls below a lower threshold, and gradually increasing or decreasing the output limit value after setting the output limit value to zero.

According to the above aspect, when a drop or rise in the DC bus voltage is detected, the DC bus voltage can be prevented from exceeding the normal operating voltage range and operation can be continued.

1 is a diagram showing an overall configuration of a power storage system according to an embodiment; FIG. 2 is a block diagram showing a functional configuration of a control device according to an embodiment. FIG. 13 is a diagram illustrating upper and lower thresholds for a DC bus voltage according to an embodiment. 5 is a flowchart illustrating an example of an output control process of a control device according to an embodiment. FIG. 11 is a first diagram for explaining an output control process according to an embodiment. FIG. 11 is a second diagram for explaining the output control process according to an embodiment. 5 is a flowchart illustrating an example of an update process of an output limit value of a control device according to an embodiment. FIG. 13 is a diagram illustrating an example of an output limiting process of a power storage system according to the prior art.

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

The PCS2 is a power conditioner connected to the power system. The PCS2 includes an inverter 21, which is a bidirectional inverter that converts AC power and DC power. The PCS2 converts DC power discharged from each storage battery unit 5 to AC power using the inverter 21 and outputs the AC power to the power system. The PCS2 also converts AC power supplied from the power system to DC power using the inverter 21 and outputs the DC power to each storage battery unit 5. The power output from the PCS2 to the load side is also referred to as PCS output power P _PCS . The PCS output power P _PCS is the power output from the PCS2 to the power system when the storage battery unit 5 is discharged, and is the power output from the PCS2 to the storage battery unit 5 when the storage battery unit 5 is charged.

The control device 3 sets an output limit value LM2 of the PCS2 so that the power (PCS output power P _PCS ) output by the PCS2 to the load side is within the range of power (P ₁ +P ₂ + ... +P _N ) that can be charged and discharged by the entire storage battery unit 5. Note that under normal circumstances, the control device 3 receives an output limit value LM1 of the PCS2 from the higher-level device 6 and controls the PCS2 according to this output limit value LM1. The specific functional configuration of the control device 3 will be described later.

The DC bus 4 is a bus for connecting the PCS 2 to multiple storage battery units 5.

The multiple storage battery units 5 are connected in parallel to the PCS2 via the DC bus 4. Each storage battery unit 5 includes a DC/DC converter 51 and a storage battery 52. The DC/DC converter 51 converts the direct current power supplied from the PCS2 to a predetermined voltage and charges the storage battery 52. The DC/DC converter 51 also converts the discharged power of the storage battery 52 to a predetermined voltage and supplies it to the PCS2.

Note that while FIG. 1 shows an example of a configuration in which the PCS 2 has the control device 3 built in, this is not limiting. In other embodiments, the control device 3 may be provided as separate hardware outside the PCS 2.

(Functional configuration of the control device)
FIG. 2 is a block diagram illustrating a functional configuration of a control device according to an embodiment.
As shown in FIG. 2 , the control device 3 includes a processor 31 , a memory 32 , a storage 33 , and a communication interface 34 .

The processor 31 operates according to a predetermined program to perform the functions of a voltage acquisition unit 310, an output limiting unit 311, a limit removal unit 312, and a limit value setting unit 313.

The voltage acquisition unit 310 acquires the voltage of the DC bus 4 connecting the PCS 2 and the storage battery unit 5 (hereinafter also referred to as DC bus voltage V _dc ) from a voltage sensor (not shown) provided on the DC bus 4 .

When the DC bus voltage _Vdc exceeds the upper threshold VUL or falls below the lower threshold VLL, the output limiting unit 311 sets the output limit value LM2 of the PCS output power P _PCS , which is the power output by the PCS2 to the load side, to zero. The upper threshold VUL and the lower threshold VLL will be described in detail later.

The limit removal unit 312 sets the output limit value LM2 to zero, and then gradually increases or decreases the output limit value LM2.

The limit value setting unit 313 fixes the output limit value LM2 at the current value when the DC bus voltage _Vdc becomes the upper limit value Vmax or the lower limit value Vmin of a predetermined normal operation voltage range R. Furthermore, when the limit value setting unit 313 receives the output limit value LM1 of the PCS output power P _PCS from the higher-level device 6, if the output limit value LM1≦the output limit value LM2, the limit value setting unit 313 overwrites the output limit value LM2 with the value of the output limit value LM1. Details of the normal operation voltage range R will be described later.

The predetermined program executed by the processor 31 is stored in a computer-readable recording medium. A computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. The computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program. The program may be for realizing some of the functions described above. The program may also be a so-called differential file (differential program) that can realize the functions described above in combination with a program already recorded in the computer system.

Memory 32 has memory space necessary for the operation of processor 31.

Storage 33 is a so-called auxiliary storage device, such as a hard disk drive (HDD) or a solid state drive (SSD). Storage 33 stores data that each part of processor 31 acquires, generates, and references during processing.

The communication interface 34 is an interface for transmitting and receiving various data and control signals between the PCS 2 and the higher-level device 6, etc.

(Regarding the upper and lower thresholds of the DC bus voltage)
FIG. 3 is a diagram illustrating upper and lower thresholds for the DC bus voltage according to one embodiment.
FIG. 3 shows an example of an upper threshold VUL, a lower threshold VLL, and a normal operation voltage range R of the DC bus voltage _Vdc .

The DC bus voltage of each storage battery unit 5 when it is unloaded (when charging/discharging is not being performed) is set as a reference voltage _V0 .

The normal operation voltage range R is a voltage fluctuation range caused by droop during normal operation of the storage battery unit 5, centered on the reference voltage _V0 . The upper limit value of the normal operation voltage range is also referred to as Vmax, and the lower limit value is also referred to as Vmin.

The upper threshold VUL and the lower threshold VLL are thresholds for detecting an abnormality in the voltage of the DC bus 4. Taking into account transient voltage fluctuations due to overshoot and resonance during voltage control, errors in the voltage sensor, etc., the upper threshold VUL is set to a value that is a predetermined amount α greater than the upper limit value Vmax of the normal operation voltage range. Similarly, the lower threshold VLL is set to a value that is a predetermined amount α smaller than the lower limit value Vmin of the normal operation voltage range. This predetermined amount α may be changed as desired depending on the characteristics of the storage battery unit 5, etc.

(Processing flow of the control device)
Fig. 4 is a flowchart showing an example of an output control process of the control device according to an embodiment. Fig. 5 is a first diagram for explaining the output control process according to an embodiment. Fig. 6 is a second diagram for explaining the output control process according to an embodiment.
Hereinafter, the flow of the output control process of the control device 3 in response to fluctuations in the DC bus voltage will be described with reference to FIGS.

3, the voltage acquisition unit 310 acquires the DC bus voltage _Vdc at each time. The output limiting unit 311 determines whether the DC bus voltage _Vdc acquired by the voltage acquisition unit 310 exceeds the upper threshold VUL or falls below the lower threshold VLL (step S01).

When the storage battery unit 5 is being charged, if the DC bus voltage _Vdc does not exceed the upper threshold VUL (step S01; NO), the output limiting unit 311 returns to step S01 and continues monitoring the DC bus 4. When the storage battery unit 5 is being discharged, if the DC bus voltage _Vdc does not fall below the lower threshold VLL (step S01; NO), the output limiting unit 311 returns to step S01 and continues monitoring the DC bus 4.

On the other hand, when the DC bus voltage _Vdc exceeds the upper threshold VUL or falls below the lower threshold VLL (step S01; YES), the output limiting unit 311 executes the output control process of the PCS2.

First, an explanation will be given of the output control process during discharge of the power storage system 1. Fig. 5 illustrates a time series of the PCS output power P _PCS and the DC bus voltage V _dc during discharge of the storage battery unit 5_2 among the three storage battery units 5_1, 5_2, and 5_3 included in the power storage system 1. Fig. 6 illustrates the correspondence between the DC bus voltage V _dc of the storage battery unit 5_2 measured at each time t01 to t05 in Fig. 5 and the output limit value LM2.

In the example of Fig. 5, a trip occurs in the storage battery unit 5_2 at time t01. In this case, the power that can be discharged by the entire storage battery unit 5 is P1+P2+P3 before time t01, but drops to P1+P3 after time t01. At this time, the PCS 2 cannot know that the storage battery unit 5_2 has tripped. Therefore, the PCS output power P _PCS does not change at time t01. Therefore, after time t01, the PCS output power P _PCS > the dischargeable power P1+P3 of the entire storage battery unit 5, and the DC bus voltage V _dc drops over time as in the example of Fig. 5.

Here, as a comparative example, a case where the output control process of this embodiment is not performed will be described. If the voltage V _BAT1 of the storage battery unit 5_1 is the highest among the storage battery units 5_1 and 5_3 that are still in operation, V _BAT1 will be approximately equal to V _DC . In this case, the storage battery unit 5_1 will compensate for the insufficient load without relying on the control of the DC/DC converter 51 of the storage battery unit 5_1. This may result in over-discharging of the storage battery unit 5_1.

To prevent such over-discharge of the storage battery unit 5_1, the control device 3 according to this embodiment executes the output control process described below.

5 and 6, after the trip occurs at time t01, the DC bus voltage _Vdc decreases over time, and at time t02, the DC bus voltage _{Vdc_t02} falls below the lower limit threshold VLL (step S01; YES). Then, the output limiting unit 311 sets the output limit value LM2 of the PSC2 to zero (step S02). When the output limit value LM2 of the PCS2 becomes zero, the PCS output power _PPCS of the PCS2 becomes zero at time t03, and the DC bus voltage _{Vdc_t03} returns (increases) to the no-load reference voltage _V0 .

After setting the output limit value LM2 of PCS2 to zero, the limit removal unit 312 gradually reduces the output limit value LM2 of PCS2 (step S03).

Next, the limit value setting unit 313 determines whether the DC bus voltage _Vdc has reached the lower limit value Vmin of the normal operation voltage range R (step S04).

5 and 6, the DC bus voltage _{Vdc_t04} has not reached the lower limit value Vmin of the normal operation voltage range R (step S04; NO). In this case, the limit value setting unit 313 waits until the next determination timing.

5 and 6, the DC bus voltage _{Vdc_t05} becomes equal to the lower limit Vmin (step S04; YES). In this case, the limit value setting unit 313 stops the gradual decrease of the output limit value LM2 and fixes the output limit value LM2 at its current value (step S05). Note that if the value of the DC bus voltage _{Vdc_t05} is within a predetermined range from the lower limit Vmin, the limit value setting unit 313 may determine that the DC bus voltage _{Vdc_t05} becomes equal to the lower limit Vmin (step S04; YES) and fix the output limit value LM2 at its current value (step S05).

6 , when the DC bus voltage _Vdc reaches the lower limit Vmin of the normal operation voltage range R, the output power P _PCS of the PCS2 approximately matches the maximum power that can be discharged from all of the storage battery units 5. Therefore, even if the storage battery unit 5_2 trips during discharging, the control device 3 can continue the operation of the power storage system 1 by controlling the other operating storage battery units 5 to discharge at the maximum power that can be discharged and to keep the DC bus voltage _Vdc within the normal operation voltage range R.

Moreover, output control during charging of the power storage system 1 will be described with reference to Fig. 6. Fig. 6 illustrates an example of the correspondence between the DC bus voltage _Vdc measured at times t11 to t15 during charging and the output limit value LM2.

For example, assume that the storage battery unit 5_2 trips at time t11. In this case, the output limit value LM2 of the PCS2 and the PCS output power P _PCS do not change at the time t11, but the DC bus voltage Vdc increases over time and exceeds the upper limit threshold VUL at the time t12 (step S01; YES).

Then, the output limiting unit 311 sets the output limit value LM2 of the PCS2 to zero (step S02). When the output limit value LM2 of the PCS2 becomes zero, at time t13, the PCS output power P _PCS of the PCS2 becomes zero, and the DC bus voltage V _{dc _t13} returns (decreases) to the no-load reference voltage V ₀ .

After setting the output limit value LM2 of PCS2 to zero, the limit removal unit 312 gradually increases the output limit value LM2 of PCS2 (step S03).

Next, the limit value setting unit 313 determines whether the DC bus voltage _Vdc has reached the upper limit value Vmax of the normal operation voltage range R (step S04).

6, the DC bus voltage _{Vdc_t14} has not reached the upper limit value Vmax of the normal operation voltage range R (step S04; NO). In this case, the limit value setting unit 313 waits until the next determination timing.

6, the DC bus voltage _{Vdc_t15} becomes equal to the upper limit value Vmax (step S04; YES). In this case, the limit value setting unit 313 stops the gradual increase of the output limit value LM2 and fixes the output limit value LM2 at its current value (step S05). Note that if the value of the DC bus voltage _{Vdc_t15} is within a predetermined range from the upper limit value Vmax, the limit value setting unit 313 may determine that the DC bus voltage _{Vdc_t15} becomes equal to the upper limit value Vmax (step S04; YES) and fix the output limit value LM2 at its current value (step S05).

6 , when the DC bus voltage _Vdc reaches the upper limit Vmax of the normal operation voltage range R, the output power P _PCS of the PCS2 approximately coincides with the maximum power that can be charged to all of the storage battery units 5. Therefore, even if the storage battery unit 5_2 trips during charging, the control device 3 can continue to operate the power storage system 1 by controlling the other operating storage battery units 5 to the maximum power that can be charged and the DC bus voltage _Vdc to be within the normal operation voltage range R.

After fixing the output limit value LM2, the control device 3 returns to step S01. In this manner, the control device 3 repeatedly performs the series of processes shown in FIG. 3 while the energy storage system 1 is operating.

In step S03, it is preferable that the limit removal unit 312 gradually increases or decreases the output limit value LM2 by setting a time constant that is sufficiently larger than that during normal voltage control. For example, the limit removal unit 312 sets the time constant so that it takes X seconds for the DC bus voltage to reach the upper limit value Vmax or the lower limit value Vmin of the normal operation voltage range R after it reaches the reference voltage _V0 . The value of X may be changed arbitrarily depending on the characteristics of the storage battery unit 5, etc.

FIG. 7 is a flowchart illustrating an example of an update process of an output limit value of the control device according to an embodiment.
The control device 3 may execute the process shown in FIG. 7 to update the output limit value LM2 of the PCS 2 in accordance with a command from the higher-level device 6.

3 that the DC bus voltage _Vdc has exceeded the upper threshold VUL or fallen below the lower threshold VLL, the control device 3 may notify the higher-level device 6 of an abnormality. In addition, the higher-level device 6 accepts an operation to specify an output limit value LM1 of the PCS2 from the manager of the power storage system 1, and transmits this output limit value LM1 to the control device 3.

Then, the control device 3 executes the process shown in Figure 7. Specifically, when the limit value setting unit 313 of the control device 3 receives a new output limit value LM1 from the higher-level device 6 (step S11), it determines whether the output limit value LM1 is less than or equal to the output limit value LM2 (step S12). If the output limit value LM1 is less than or equal to the output limit value LM2 (step S12; YES), the limit value setting unit 313 sets the value of the output limit value LM2 to the value of the output limit value LM1 received from the higher-level device 6 (step S13). On the other hand, if the output limit value LM1 is greater than the output limit value LM2 (step S12; NO), the limit value setting unit 313 ends the process without changing the value of the output limit value LM2.

That is, when the control device 3 detects an abnormality in the DC bus voltage _Vdc (step S01 in FIG. 3; YES), the control device 3 executes the series of processes in FIG. 3 to perform automatic control to provisionally change the output limit value LM2. Furthermore, when the control device 3 receives a new output limit value LM1 from the higher-level device 6 during normal operation (when the DC bus voltage _Vdc is within the normal operation voltage range R), if the output limit value LM1≦the output limit value LM2, the control device 3 resets the output limit value LM2 according to the output limit value LM1. Thereafter, the storage system 1 continues to operate according to the output limit value LM1 specified by the higher-level device 6. For example, after the storage battery unit 5_2 is repaired and replaced to become operable, the output limit value LM2 is reset according to the output limit value LM1 from the higher-level device 6, thereby maximizing the power that can be charged and discharged by the entire storage system 1.

(Action, Effect)
As described above, the control device 3 according to this embodiment includes a voltage acquisition unit ₃₁₀ that acquires the DC bus voltage _Vdc of the DC bus 4 that connects the PCS 2 and the storage battery unit 5, an output limiting unit 311 that sets the PCS output power P, which is the power that the _PCS 2 outputs to the load side, to zero when the DC bus voltage Vdc exceeds the upper threshold VUL or falls below the lower threshold VLL, and a limit release unit 312 that gradually increases or decreases the output limit value LM2 after setting the output limit value LM2 to zero.

In this manner, when the control device 3 detects an abnormality in the DC bus voltage _Vdc , it temporarily sets the output limit value LM2 of the PCS2 to zero to return the DC bus voltage _Vdc to the reference voltage _V0 , and then gradually increases or decreases the output limit value LM2, thereby preventing the DC bus voltage _Vdc from exceeding the normal operation voltage range R and allowing operation to continue.

In addition, the control device 3 further includes a limit value setting unit 313 that stops the gradual increase or decrease of the output limit value LM2 and fixes it when the DC bus voltage _Vdc becomes the upper limit value Vmax or the lower limit value Vmin of a predetermined normal operation voltage range R.

When the DC bus voltage _Vdc substantially coincides with the upper limit value Vmax or the lower limit value Vmin of the normal operation voltage range R, the output power P _PCS of the PCS 2 substantially coincides with the maximum power that can be charged/discharged from all of the storage battery units 5. Therefore, by having the above-described configuration, even if an abnormality (such as a trip) occurs in some of the storage battery units 5, the control device 3 can control the operating storage battery 5 units to the maximum power that can be charged/discharged and the DC bus voltage _Vdc to be within the normal operation voltage range R, thereby enabling the operation of the power storage system 1 to continue.

The limit value setting unit 313 also receives a new output limit value LM1 from the higher-level device 6, and if the new output limit value LM1 is smaller than the output limit value LM2, it overwrites the output limit value LM2 with the value of the new output limit value LM1.

In this way, for example, after the storage battery unit 5 has been repaired or replaced and is once again operable, the control device 3 can reset the output limit value LM2 based on the output limit value LM1 newly instructed by the higher-level device 6, thereby maximizing the amount of power that can be charged and discharged by the entire storage system 1.

As described above, the embodiments of the present disclosure have been described, but the above-mentioned embodiments are presented as examples and are not intended to limit the scope of the present disclosure. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the present disclosure. These embodiments and their modifications are included in the scope of the present disclosure and its equivalents as set forth in the claims, as well as in the scope and gist of the present disclosure.

<Additional Notes>
The control device, the power conditioner, the control method, and the program described in the above-described embodiments can be understood, for example, as follows.

(1) According to a first aspect of the present disclosure, the control device 3 includes a voltage acquisition unit 310 that acquires a voltage _Vdc of the DC bus 4 connecting the PCS 2 and the storage battery unit 5, an output limiting unit 311 that sets a _PCS output limit value LM2 of _{the PCS} , which is the power that the PCS 2 outputs to the load side, to zero when Vdc exceeds an upper threshold VUL or falls below a lower threshold VLL, and a limit removal unit 312 that gradually increases or decreases the output limit value LM2 after setting the output limit value LM2 to zero.

In this manner, when the control device 3 detects an abnormality in the DC bus voltage _Vdc , it temporarily sets the output limit value LM2 of the PCS2 to zero to return the DC bus voltage _Vdc to the reference voltage _V0 , and then gradually increases or decreases the output limit value LM2, thereby preventing the DC bus voltage _Vdc from exceeding the normal operation voltage range R and allowing operation to continue.

(2) According to a second aspect of the present disclosure, the control device 3 according to the first aspect further includes a limit value setting unit 313 that stops the gradual increase or decrease of the output limit value LM2 and fixes it when the voltage _Vdc reaches an upper limit value Vmax or a lower limit value Vmin of a predetermined normal operation voltage range R.

When the DC bus voltage _Vdc substantially coincides with the upper limit value Vmax or the lower limit value Vmin of the normal operation voltage range R, the output power P _PCS of the PCS 2 substantially coincides with the maximum power that can be charged/discharged from all of the storage battery units 5. Therefore, by having the above-described configuration, even if some of the storage battery units 5 trip, the control device 3 can continue to operate the power storage system 1 by controlling the operating storage battery 5 units to the maximum power that can be charged/discharged and the DC bus voltage _Vdc to be within the normal operation voltage range R.

(3) According to a third aspect of the present disclosure, in the control device 3 according to the second aspect, the limit value setting unit 313 receives a new output limit value LM1 from the higher-level device 6, and if the new output limit value LM1 is smaller than the output limit value LM2, overwrites the output limit value LM2 with the value of the new output limit value LM1.

In this way, for example, after the storage battery unit 5 has been repaired or replaced and is once again operable, the control device 3 can reset the output limit value LM2 according to a command value from the higher-level device 6, thereby maximizing the amount of power that can be charged and discharged by the entire energy storage system 1.

(4) According to a fourth aspect of the present disclosure, the PCS 2 includes a control device 3 according to any one of the first to third aspects.

(5) According to a fifth aspect of the present disclosure, the control method includes the steps of acquiring a voltage _Vdc of a DC bus 4 connecting the PCS 2 and the storage battery unit 5, setting a _PCS output power P, which is power that the PCS 2 outputs to the load side, to zero when the voltage _Vdc exceeds an upper threshold VUL or falls below a lower threshold VLL, and gradually increasing or decreasing the output limit value LM2 after setting the output limit value LM2 to zero.

(6) According to a sixth aspect of the present disclosure, the program causes the control device 3 to execute the following steps: acquiring the voltage _Vdc of the DC bus 4 connecting the PCS 2 and the storage battery unit 5; when the voltage _Vdc exceeds an upper threshold VUL or falls below a lower threshold VLL, setting to zero an output limit value LM2 of _{the PCS} output power P, which is the power that the PCS 2 outputs to the load side; and, after setting the output limit value LM2 to zero, gradually increasing or decreasing the output limit value LM2.

According to the above-mentioned embodiment, when a drop or rise in the DC bus voltage is detected, the DC bus voltage can be prevented from exceeding the normal operating voltage range and operation can be continued.

1 Power storage system 2 PCS
Reference Signs List 21 Inverter 3 Control device 31 Processor 310 Voltage acquisition unit 311 Output limiting unit 312 Limitation removal unit 313 Limit value setting unit 32 Memory 33 Storage 34 Communication interface 4 DC bus 5 Storage battery unit 51 DC/DC converter 52 Storage battery 6 Upper device

Claims (6)

A voltage acquisition unit that acquires a voltage of a DC bus that connects a power conditioner (PCS) and the storage battery unit;
An output limiting unit that sets an output limit value of a PCS output power, which is power output by the power conditioner to a load side, to zero when the voltage exceeds an upper threshold or falls below a lower threshold;
a limit release unit that gradually increases or decreases the output limit value after setting the output limit value to zero;
A control device comprising: A limit value setting unit that stops the gradual increase or decrease of the output limit value and fixes it when the voltage reaches an upper limit value or a lower limit value of a predetermined normal operation voltage range.
The control device according to claim 1 . the limit value setting unit receives a new output limit value from a higher-level device, and if the new output limit value is smaller than the output limit value, overwrites the output limit value with the new output limit value.
The control device according to claim 2. A power conditioner equipped with a control device according to any one of claims 1 to 3. Acquiring a voltage of a DC bus connecting a power conditioner (PCS) and a storage battery unit;
When the voltage exceeds an upper threshold or falls below a lower threshold, setting an output limit value of a PCS output power, which is the power output by the power conditioner to a load side, to zero;
setting the output limit value to zero and then gradually increasing or decreasing the output limit value;
The control method includes: Acquiring a voltage of a DC bus connecting a power conditioner (PCS) and a storage battery unit;
When the voltage exceeds an upper threshold or falls below a lower threshold, setting an output limit value of a PCS output power, which is the power output by the power conditioner to a load side, to zero;
setting the output limit value to zero and then gradually increasing or decreasing the output limit value;
A program that causes a control device to execute the above.

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